[Federal Register Volume 78, Number 9 (Monday, January 14, 2013)]
[Proposed Rules]
[Pages 2798-2868]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2013-00359]
[[Page 2797]]
Vol. 78
Monday,
No. 9
January 14, 2013
Part III
Department of Transportation
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National Highway Traffic Safety Administration
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49 CFR Parts 571 and 585
Federal Motor Vehicle Safety Standards; Minimum Sound Requirements for
Hybrid and Electric Vehicles; Draft Environmental Assessment for
Rulemaking To Establish Minimum Sound Requirements for Hybrid and
Electric Vehicles; Proposed Rules
Federal Register / Vol. 78 , No. 9 / Monday, January 14, 2013 /
Proposed Rules
[[Page 2798]]
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DEPARTMENT OF TRANSPORTATION
National Highway Traffic Safety Administration
49 CFR Parts 571 and 585
[Docket No. NHTSA-2011-0148]
RIN 2127-AK93
Federal Motor Vehicle Safety Standards; Minimum Sound
Requirements for Hybrid and Electric Vehicles
AGENCY: National Highway Traffic Safety Administration (NHTSA),
Department of Transportation (DOT).
ACTION: Notice of proposed rulemaking (NPRM).
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SUMMARY: As required by the Pedestrian Safety Enhancement Act (PSEA) of
2010 this rule proposes to establish a Federal motor vehicle safety
standard (FMVSS) setting minimum sound requirements for hybrid and
electric vehicles. This new standard would require hybrid and electric
passenger cars, light trucks and vans (LTVs), medium and heavy duty,
trucks, and buses, low speed vehicles (LSVs), and motorcycles to
produce sounds meeting the requirements of this standard. This proposed
standard applies to electric vehicles (EVs) and to those hybrid
vehicles (HVs) that are capable of propulsion in any forward or reverse
gear without the vehicle's internal combustion engine (ICE) operating.
This standard would ensure that blind, visually-impaired, and other
pedestrians are able to detect and recognize nearby hybrid and electric
vehicles, as required by the PSEA, by requiring that hybrid and
electric vehicles emit sound that pedestrians would be able to hear in
a range of ambient environments and contain acoustic signal content
that pedestrians will recognize as being emitted from a vehicle.
The benefit of reducing the pedestrian injury rate per registered
vehicle of HVs to ICE vehicles when 4.1% of the fleet is HV and EV
would be 2790 fewer pedestrian and pedalcyclist injuries. We also
estimate that this proposal will result in 10 fewer pedestrian and
pedalcyclist injuries caused by LSVs. Thus, 2800 total injured
pedestrians are expected to be avoided due to this proposal
representing 35 equivalent lives saved. We do not estimate any
quantifiable benefits for EVs because it is our view that EV
manufacturers would have installed alert sounds in their cars without
passage of the PSEA and this proposed rule. Comparison of costs and
benefits expected due to this rule provides a cost of $0.83 to $0.99
million per equivalent life saved across the 3 and 7 percent discount
levels for the light EV and HV and LSV fleet. According to our present
model, a countermeasure that allows a vehicle to meet the proposed
minimum sound requirements would be cost effective compared to our
comprehensive cost estimate of the value of a statistical life of $6.3
million.
DATES: Comments must be received on or before March 15, 2013.
ADDRESSES: You may submit comments to the docket number identified in
the heading of this document by any of the following methods:
Federal eRulemaking Portal: go to http://www.regulations.gov. Follow the online instructions for submitting
comments.
Mail: Docket Management Facility, M-30, U.S. Department of
Transportation, West Building, Ground Floor, Rm. W12-140, 1200 New
Jersey Avenue SE., Washington, DC 20590.
Hand Delivery or Courier: West Building Ground Floor, Room
W12-140, 1200 New Jersey Avenue SE., between 9 a.m. and 5 p.m. Eastern
Time, Monday through Friday, except Federal holidays.
Fax: (202) 493-2251.
Regardless of how you submit your comments, you should mention the
docket number of this document.
You may call the Docket at 202-366-9324.
Instructions: For detailed instructions on submitting comments and
additional information on the rulemaking process, see the Public
Participation heading of the Supplementary Information section of this
document. Note that all comments received will be posted without change
to http://www.regulations.gov, including any personal information
provided.
Privacy Act: Please see the Privacy Act heading under Rulemaking
Analyses and Notices.
FOR FURTHER INFORMATION CONTACT:
For non-legal issues, Ms. Gayle Dalrymple, Office of Crash Avoidance
Standards (telephone: 202-366- 5559) (fax: 202-493-2990). Ms.
Dalrymple's mailing address is National Highway Traffic Safety
Administration, NVS-112, 1200 New Jersey Avenue SE., Washington, DC
20590.
For legal issues, Mr. Thomas Healy, Office of the Chief Counsel
(telephone: 202-366-2992) (fax: 202-366-3820). Mr. Healy's mailing
address is National Highway Traffic Safety Administration, NCC-112,
1200 New Jersey Avenue SE., Washington, DC 20590.
SUPPLEMENTARY INFORMATION:
Table of Contents
I. Executive Summary
II. Background
III. Pedestrian Safety Enhancement Act of 2010
IV. Consultation With External Organizations
V. Safety Problem
A. Comparing the Vehicle to Pedestrian Crash Experience of
Internal Combustion Engine Vehicles to Hybrid and Electric Vehicles
B. Need for Independent Mobility of People Who Are Visually
Impaired and Blind
VI. NHTSA Research and Industry Practices
A. NHTSA Phase 1 Research
B. NHTSA Phase 2 Research
C. NHTSA Phase 3 Research
D. International Approach to Pedestrian Alert Sounds
E. SAE Sound Measurement Procedure
F. Alert Sounds Currently Provided by Manufacturers
G. The Notice of Intent To Prepare an Environmental Assessment
VII. NHTSA's Proposal
A. Acoustic Specifications Developed To Enhance Detection and
Recognition
B. Critical Operating Scenarios
1. Stationary But Activated
2. Reverse
3. Acceleration and Deceleration
4. Constant Speed
C. Application
1. The Definition of Hybrid Vehicle
2. Vehicles With a GVWR Over 10,000 lbs
3. Electric Motorcycles
4. Low Speed Vehicles
5. Quiet Internal Combustion Engine Vehicles
D. Requirements
1. Acoustic Parameters Designed According to a Detectability
Model
2. Recognizability Requirements
3. Prohibition Against Modifying a Vehicle Sound
4. Phase-in Schedule
E. Compliance Test Procedure
1. Test Condition
2. Vehicle Condition
3. Test Procedure
a. Start-up
b. Stationary But Activated and Directivity
c. Reverse
d. Constant Speed
e. Pitch Shifting
f. Recognizability
g. Vehicles of the Same Make and Model Emitting the Same Sound
VIII. Alternatives Considered But Not Proposed
A. Requiring Vehicle Sound To Be Playback of an Internal
Combustion Engine Recording
B. Requiring That the Alert Sound Adapt to the Ambient
C. Acoustic Profile Designed Around Sounds Produces by Internal
Combustion Engine Vehicles
D. Acoustic Profiles Suggested by Manufacturers
E. International Guidelines for Vehicle Alert Sounds
F. Suggestions in Comments to the Notice of Intent That Did Not
Satisfy the
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Statement of Purpose and Need for the Rulemaking
G. Possible Jury Testing for Recognition of a Synthetic Sound
IX. NHTSA's Role in the Development of a Global Technical Regulation
X. Analysis of Costs, Benefits and Environmental Effects
A. Benefits
B. Costs
C. Comparison of Costs and Benefit
D. Environmental Effects
XI. Regulatory Notices and Analyses
I. Executive Summary
As required by the PSEA,\1\ this rule proposes to establish FMVSS
No.141, Minimum Sound Requirements for Hybrid and Electric Vehicles,
which would require hybrid and electric passenger cars, LTVs, medium
and heavy duty trucks and buses, LSVs, and motorcycles to produce
sounds meeting the requirements of this standard. This proposed
standard applies to EVs and to those HVs that are capable of propulsion
in any forward or reverse gear without the vehicle's ICE operating. The
PSEA requires NHTSA to establish performance requirements for an alert
sound that is recognizable as motor vehicle in operation that allows
blind and other pedestrians to reasonably detect a nearby EV or HV
operating below the crossover speed. The crossover speed is the speed
at which tire noise, wind noise, and other factors eliminate the need
for a separate alert sound. The PSEA defines ``alert sound'' as ``a
vehicle-emitted sound to enable pedestrians to discern vehicle
presence, direction, location and operation.'' \2\ The legal authority
for this rulemaking comes from the PSEA and 49 U.S.C. 30111.
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\1\ Public Law 111-373, 124 Stat. 4086 (January 4, 2011).
\2\ Id. at Section 2(2).
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This standard will ensure that blind, visually-impaired, and other
pedestrians are able to detect and recognize nearby hybrid and electric
vehicles by requiring that hybrid and electric vehicles emit sound that
pedestrians will be able to hear in a range of ambient environments and
contain acoustic signal content that pedestrians will recognize as
being emitted from a vehicle. The proposed standard establishes minimum
sound requirements for hybrid and electric vehicles when operating
under 30 kilometers per hour (km/h) (18 mph), when the vehicle's
starting system is activated but the vehicle is stationary, and when
the vehicle is operating in reverse.
The requirements of this proposal apply only to those HVs that are
capable of propulsion in any forward or reverse gear without the
vehicle's ICE operating because these were the vehicles that the agency
believes fall under the definition of ``hybrid vehicle'' contained in
the PSEA. The agency chose a crossover speed of 30 km/h because this
was the speed at which the sound levels of the hybrid and electric
vehicles measured by the agency approximated the sound levels produced
by similar ICE vehicles. This proposal contains minimum sound
requirements for the activated but stationary operating condition
because the definition of alert sound in the PSEA, as explained in
Section III of this NPRM, requires the agency to issue minimum sound
requirements to allow pedestrians to detect hybrid and electric
vehicles. We have tentatively determined that this requirement can be
best met by requiring vehicles to emit sound in this operating
condition.
At lower speeds, hybrid and electric vehicles produce less sound
than vehicles propelled by an ICE. At higher speeds, tire and wind
noise are the main contributors to vehicles noise output so at higher
speeds the sounds produced by hybrid and electric vehicles and ICE
vehicles are similar. Because hybrid and electric vehicles do not
produce as much sound as ICE vehicles when operating at lower speeds,
pedestrians and other road users may not be aware of the presence of a
nearby hybrid or electric vehicle. If a hybrid vehicle is involved in a
low speed maneuver (defined as making a turn, slowing or stopping,
backing up, entering or leaving a parking space, or starting in
traffic), it is 1.38 times more likely than an ICE vehicle to be
involved in a collision with a pedestrian and 1.33 times more likely to
be involved in a collision with a pedalcyclist. We believe that this
difference in accident rates is mostly attributable to the pedestrians'
inability to detect these vehicles by hearing them during these
maneuvers. We seek comment on this assumption.
Statistics for pedestrian collision rates of hybrid and electric
vehicles with a GVWR over 4,536 kg (10,000 lb), and motorcycles were
not available because of the limited penetration of these vehicles into
the fleet. NHTSA expects that should the penetration of hybrid and
electric heavy vehicles, and motorcycles reach the current rate of
penetration of light hybrid and electric vehicles into the fleet, then
the difference in pedestrian collision rates between hybrid and
electric heavy vehicles, and motorcycles and their traditional ICE
counterparts will be similar to the difference in pedestrian collision
rates between light HVs and light ICE vehicles.
In addition to analyzing crash data, the agency measured the sound
produced by HVs, EVs and ICE vehicles to determine the difference in
sound output between the propulsion types at different speeds and
conducted research to see if there was a difference in the ability of
pedestrians to detect approaching hybrid and electric vehicles versus
ICE vehicles. The agency also used acoustic models to determine the
frequency composition of sounds that would give pedestrians the best
chance to detect approaching hybrid and electric vehicles without
contributing undesirably to surrounding ambient noise levels.
The proposed standard ensures that pedestrians will be able to
determine whether a hybrid or electric vehicle is accelerating or
decelerating by requiring the frequency content of the sound emitted by
the vehicle to increase in a manner that is similar to the sound
produced by ICE vehicles when accelerating and decelerating. The agency
developed the minimum sound specifications contained in this proposal
using a detection model that estimated the distance at which a
pedestrian would be able hear a given sound in the presence of a given
ambient sound profile. The standard also requires, as mandated by the
PSEA, that all vehicles of the same make, model and model year emit the
same sound.
The PSEA requires that the final rule establishing this standard be
issued by January 4, 2014 and include a phase-in schedule that
concludes with ``full compliance with the required motor vehicle safety
standard for motor vehicles manufactured on or after September 1st of
the calendar year that begins 3 years after the date on which the final
rule is issued.'' For example the means that if the final rule is
issued January 4, 2014, compliance would commence on September 1, 2015,
which would mark the start of a three-year phase-in period. We
tentatively conclude that the following phase in schedule is reasonable
for manufacturers and allows the fastest implementation of the standard
for pedestrian safety:
30 percent of the subject vehicles produced on or after September
1of the first year of the phase in;
60 percent of the subject vehicles produced on or after September
1of the second year of the phase in;
90 of the subject vehicles produced on or after September 1of the
third year of the phase in; and
100 percent of all vehicles produced on or after, by September 1 of
the year that begins three years after the date that the final rule is
issued.
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As discussed in detail in Section X of this notice, the benefits of
this proposed rule, if made final, will accrue from injuries to
pedestrians that will be avoided, assuming that the rule will cause the
pedestrian injury rate for HVs and EVs to decrease to that of ICE
vehicles. As discussed in Section V, a traditional analysis of
pedestrian fatalities is not appropriate for this rulemaking. If HVs
and EVs continue to rise in popularity and increase their role in the
U.S. fleet to four percent of all vehicle registrations, unchanged by
rulemaking or industry action, a total of 2,790 injured pedestrians and
pedalcyclists would be expected over the life time of the 2016 model
year fleet due to the pedestrians' and pedalcyclists' inability to
detect these vehicles by hearing. We estimate that the benefit then of
reducing the pedestrian injury rate per registered vehicle of HVs to
ICE vehicles when four percent of the fleet is HV and EV would be 2,790
fewer injured pedestrians and pedalcyclists. We do not estimate any
quantifiable benefits in pedestrian or pedalcyclist injury reduction
for EVs because it is our view that EV manufacturers would have
installed alert sounds in their cars without passage of the PSEA and
this proposed rule. We also estimate that this proposal will result in
10 fewer injured pedestrians and pedalcyclists caused by LSVs.
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\3\ Scaled benefits and costs for low speed vehicles are
estimated directly proportional to light vehicles based on sales.
Scaled costs include both installation costs for the system and fuel
costs.
Discounted Benefits for Passenger Cars (PCs) and LTVs, MY2016, 2010$
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Pedestrians Pedalcyclists Total PED + CYC
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3% discount 3% discount Total monetized 3% discount Total monetized 3% discount Total monetized
factor benefits Total ELS factor benefits Total ELS factor benefits Total ELS
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(PC).......................................... 0.8034 $58,640,938 9.27 0.8034 $64,106,653 10.14 0.8034 $122,747,591 19.41
(LTV)......................................... 0.8022 26,945,946 4.26 0.8022 28,319,549 4.48 0.8022 55,265,495 8.74
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Total..................................... ........... 85,586,884 13.54 ........... 92,426,203 14.62 ........... 178,013,086 28.15
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Pedestrians Pedalcyclists Total PED + CYC
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7% discount 7% discount Total monetized 7% discount Total monetized 7% discount Total monetized
factor benefits Total ELS factor benefits Total ELS factor benefits Total ELS
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(PC).......................................... 0.6700 $48,903,944 7.73 0.6700 $53,462,108 8.46 0.6700 $102,366,052 16.19
(LTV)......................................... 0.6303 21,171,815 3.35 0.6303 22,251,074 3.52 0.6303 $43,422,889 6.87
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Total..................................... ........... 70,075,758 11.08 ........... 75,713,183 11.97 ........... 145,788,941 23.06
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Total Costs for PCs and LTVs, MY2016, 2010$
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Sales Fuel costs/ Fuel costs Install Install costs Total cost/
3% discount Sales impacted veh (total) costs/veh total veh Total costs
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(PC)............................ 9,032,303 439,586 $4.73 $2,079,240 $30.00 $13,187,566 $34.73 $15,266,805
(LTV)........................... 7,164,729 231,685 5.33 1,234,880 30.00 6,950,542 35.33 8,185,421
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Total....................... 16,197,032 671,270 4.94 3,314,119 30.00 20,138,107 34.94 23,452,226
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Sales Fuel costs/ Fuel costs Install Install costs Total cost/
7% discount Sales impacted veh (total) costs/veh total veh Total costs
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(PC)............................ 9,032,303 439,586 $3.83 $1,683,613 $30.00 $13,187,566 $33.83 $14,871,178
(LTV)........................... 7,164,729 231,685 4.23 980,026 30.00 6,950,542 34.23 7,930,568
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Total....................... 16,197,032 671,270 3.97 2,663,639 30.00 20,138,107 33.97 22,801,746
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Costs and Scaled Benefits for LSVs, MY2016 \3\
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Sales ratio Scaled Scaled
Discount rate LSV to light Sales Scaled costs injuries Scaled ELS Scaled benefits minus
vehicle (undisc.) benefits scaled costs
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3%...................................... 0.37% 2,500 $87,268 10.39 0.1049 $662,971 $575,703
7%...................................... 0.37% 2,500 84,845 10.39 0.0859 542,959 458,114
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[[Page 2801]]
NHTSA estimates the fuel and installation cost of adding a speaker
system in order to comply with the requirements of this proposal to be
around $35 per vehicle for light vehicles. We estimate the total fuel
and installation costs of this proposal to the light EV, HV and LSV
fleet to be $23.6M at the 3 percent discount rate and $22.9M at the 7
percent discount rate. The estimated total installation cost for hybrid
and electric heavy and medium duty trucks and buses and electric
motorcycles is $1.48M for MY 2016. We have only calculated the benefits
of this proposal for light EVs, HVs and LSVs because we do not have
crash rates for hybrid and electric heavy and medium duty trucks and
buses and electric motorcycles. To estimate the benefits of this
proposal we have converted injured pedestrians and pedalcyclists
avoided into equivalent lives saved. We estimate that the impact of
this proposal in pedestrian and pedalcyclist injury reduction in light
vehicles and LSVs will be 28.15 equivalent lives saved at the 3 percent
discount rate and 23.06 equivalent lives saved at the 7 percent
discount rate. The benefits of this proposal for the light EV and HV
and LSV fleet are $178.7M at the 3 percent discount rate and $146.3M at
the 7 percent discount rate. Comparison of costs and benefits expected
due to this proposal for the light EV, HV and LSV fleet provides a cost
of $0.83 to $0.99 million per equivalent life saved across the 3 and 7
percent discount levels. According to our present model, a
countermeasure that allows a vehicle to meet the proposed minimum sound
requirements would be cost effective compared to our comprehensive cost
estimate of the value of a statistical life of $6.3 million.
Total Benefits and Costs Summary for Light Vehicles and Low Speed
Vehicles, MY2016, 2010$
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3% discount rate 7% discount rate
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Total Monetized Benefits.... $178.7M $146.3M
Total Costs (Install+Fuel).. 23.5M 22.9M
Total Net Impact (Benefit-- 155.2M 123.4M
Costs).....................
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II. Background
Whether or not a vehicle can be easily detected by the sound it
makes is a product of vehicle type, vehicle speed, and ambient sound
level. Quieter vehicles, such as EVs and HVs, can reduce pedestrians'
ability to assess the state of nearby traffic and, as a result, can
have an impact on pedestrian safety. EVs and HVs may pose a safety
problem for pedestrians, in particular pedestrians who are blind or
visually impaired and who therefore rely on auditory cues from vehicles
to navigate. For these pedestrians, the primary safety issue arises
when an HV or EV operates quietly using its electric motor for
propulsion at low speeds. This is also the case when other auditory
cues, such as the noise from the vehicle's tires and wind resistance,
are less noticeable.
Since August 2007, NHTSA has been monitoring the work of the
Society of Automotive Engineers' (SAE) Vehicle Sound for Pedestrians
(VSP) Committee. Participants in the VSP committee include vehicle
manufacturers, suppliers, consulting firms, government, and other
interested parties. The VSP committee's primary goal is to develop a
test procedure to measure the minimum sound output of a motor vehicle.
In September 2011, the SAE published the test procedure, Measurement of
Minimum Noise Emitted by Road Vehicles, (SAE-J2889-1).\4\ The purpose
of J2889-1 is to provide an objective, technology-neutral test to
measure the minimum sound emitted by a vehicle in a specified ambient
noise condition. This is a test procedure only and does not describe
the VSP committee's rationale, provide recommendations about how sounds
for HVs and EVs should be developed or produced, nor does it specify
the ambient condition at which a vehicle sound should be detectable for
the safety of pedestrians.
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\4\ Society of Automotive Engineers (2011) Measurement of
Minimum Noise Emitted by Road Vehicles, SAE-J2889-1. Warrendale, PA.
Available at http://standards.sae.org/wip/j2889/1/.
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On May 30, 2008, NHTSA published a notice \5\ in the Federal
Register announcing that the agency would hold a public meeting on June
23, 2008 for government policymakers, stakeholders from organizations
representing people who are blind or visually impaired, industry
representatives, and public interest groups to discuss the technical,
environmental and safety issues associated with EVs, HVs, and quiet ICE
vehicles, and the safety of pedestrians. The presentations submitted at
the public meeting and a transcript of the meeting can be found in
Docket No. NHTSA-2008-0108 on the Web site http://www.regulations.gov.\6\ Topics discussed at the meeting included a
statement of the problem, general pedestrian safety, sound measurement
and mobility, automotive industry perspective, SAE work and status,
potential solutions, and noise abatement. At the conclusion of the
public meeting, NHTSA indicated the agency's intention to put together
a research plan and encouraged participants to add comments and ideas
to the docket. NHTSA issued a research plan to investigate the topic of
quieter vehicles and the safety of pedestrians on May 6, 2009.\7\
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\5\ 73 FR 31187; May 30, 2008.
\6\ The presentations are in document 0012 and the
transcript is in document 0023 (Docket No. NHTSA-2008-
0108-0012 and Docket No. NHTSA-2008-0108-0023, respectively).
\7\ Quieter Cars and the Safety of Blind Pedestrians: The NHTSA
Research Plan, April 2009, available at http://www.regulations.gov/#!documentDetail;D=NHTSA-2008-0108-0025.
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In September 2009, NHTSA published a technical report documenting
the incidence of crashes involving hybrid-electric passenger vehicles
and pedestrians and pedalcyclists.\8\ The analysis included a sample of
8,387 hybrid and 559,703 ICE vehicles. The analysis used data from 12
states and a subset of model-year 2000 and later vehicles. The results
of the crash data analysis show that HVs are two times more likely than
ICE vehicles to be in a pedestrian crash where the vehicle is backing
out, slowing/stopping, starting in traffic, and entering or leaving a
parking space/driveway. The vehicles involved in such crashes are
likely to be moving at low speeds at which the difference between the
sounds emitted by ICE vehicles and HVs is substantial. The crash
incidence rate for the combined set of maneuvers is 0.6 percent and 1.2
percent for ICE vehicles and HVs respectively and the difference is
statistically significant. Some of the factors considered in this
analysis are: (1) vehicle maneuver prior to the crash; (2) speed limit
as a proxy for vehicle travel speed; and (3) weather and
[[Page 2802]]
lighting condition at the time of the crash.
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\8\ R. Hanna (2009) Incidence of Pedestrian and Bicyclists
Crashes by Hybrid Electric Passenger Vehicles, Report No. DOT HS 811
204. U.S. Dept. of Transportation, Washington, DC Available at
http://www-nrd.nhtsa.dot.gov/Pubs/811204.PDf.
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In October 2009, NHTSA issued a report entitled ``Research on
Quieter Cars and the Safety of Blind Pedestrians, A Report to
Congress.'' \9\ The report briefly discusses the quieter vehicle safety
issue, how NHTSA's research plan would address the issue, and the
status of the agency's research in implementing that plan.
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\9\ Research on Quieter Cars and the Safety of Blind
Pedestrians, A Report to Congress. U.S. Dept of Transportation,
Washington, DC, October 2009, available at http://www.nhtsa.gov/DOT/NHTSA/NVS/Crash%20Avoidance/Technical%20Publications/2010/RptToCongress091709.pdf.
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In April 2010, NHTSA issued a report presenting results of Phase 1
of the agency's research.\10\ This report documents the overall sound
levels and general spectral content for a selection of ICE vehicles and
HVs in different operating conditions, evaluates vehicle detectability
for two background noise levels, and considers countermeasure concepts
that are categorized as vehicle-based, infrastructure-based, and
systems requiring vehicle-pedestrian communications.
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\10\ Garay-Vega et al. (2010) Quieter Cars and the Safety of
Blind Pedestrians: Phase I, Report No. DOT HS 811 304, U.S. Dept. of
Transportation, Washington, DC. Available at http://www.nhtsa.gov/DOT/NHTSA/NVS/Crash%20Avoidance/Technical%20Publications/2010/811304rev.pdf.
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The results show that the overall sound levels for the HVs tested
are noticeably lower at low speeds than for the ICE vehicles tested.
Overall, study participants were able to detect any vehicle sooner in
the low ambient noise condition. ICE vehicles tested were detected
sooner than their HV twins except for the test scenario in which the
target vehicle was slowing down. In this scenario, HVs were detected
sooner because of the distinctive sound emitted by the regenerative
braking system on the HVs. Response time to detect a target vehicle
varies by vehicle operating condition, ambient sound level, and vehicle
type (i.e., ICE vehicle versus HV in EV mode).
NHTSA initiated additional research (Phase 2) in March 2010 to
explore potential audible countermeasures to be used in vehicles while
operating in electric mode in specific low speed conditions.\11\ The
potential countermeasures explored included quantitative specifications
for sound levels and spectral profiles for detectability. The
feasibility of objectively specifying other aspects of sound quality
for the purpose of predicting recognizability was also explored.
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\11\ Garay-Vega et al. (2011) Quieter Cars and the Safety of
Blind Pedestrians, Phase 2: Development of Potential Specifications
for Vehicle Countermeasure Sounds, Report No. DOT HS 811 496. Dept.
of Transportation, Washington, DC. Available at http://www.nhtsa.gov/DOT/NHTSA/NVS/Crash%20Avoidance/Technical%20Publications/2011/811496.pdf.
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In our Phase 2 study, researchers assumed that acoustic
countermeasures should provide alerting information at least equivalent
to the cues provided by ICE vehicles. Groups representing people who
are blind or visually impaired have expressed a preference for sound(s)
that will be recognized as that of an approaching vehicle so that it
will be intuitive for all pedestrians.\12\ In the Phase 2 research,
acoustic data acquired from a sample of ICE vehicles was used to
determine the sound levels at which synthetic vehicle sounds, developed
as countermeasures, could be set. ICE equivalent sounds were specified
using overall A-weighted sound levels and, one-third octave band
spectral content. (See Appendix A, ``Glossary of Sound Engineering
Terms'' and Appendix B, ``Acoustic Primer'' for definitions and
explanations of all acoustic terms used in this notice.)
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\12\ Goodes et al. (2009) Investigation into the Detection of a
Quiet Vehicle by the Blind Community and the Application of an
External Noise Emitting System, SAE 2009-01-2189. Society of
Automotive Engineers, Warrendale, PA; Maurer (2008) The Danger Posed
by Silent Vehicles. National Federation of the Blind. Remarks made
for the United Nations Economic Commission for Europe, Working Party
on Noise. 47th GRB session February 19, 2008 Geneva. Informal
Document No. GRB-47-10. http://www.unece.org/trans/doc/2008/wp29grb/ECE-TRANS-WP29-GRB-47-inf10e.pdf.
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Psychoacoustic models and human subject testing were used to
explore issues of detectability, masking, and recognition of ICE-like
and alternative sound countermeasures. Psychoacoustic models showed
that frequency components between 1600 and 5000 Hz were more detectable
due to strong signal strength and relatively low ambient levels in this
range. Also, frequency components below 315 Hz were often masked by
urban ambient noise.\13\ Human subject studies were conducted to
evaluate countermeasure sounds in a controlled outdoor environment for
six miles per hour forward pass-by with the counter measure sound
output set at 59.5 A-weighted dB and then at 63.5 A-weighted dB
measured 2 meters from the vehicle centerline. The sounds included ICE-
like sounds, alternative (non-ICE-like) sounds designed according to
psychoacoustic principles to improve detectability, and sounds that
combine alternative sounds with some ICE-like components. In addition
to the countermeasure sounds, an ICE vehicle sound was included in the
study as a baseline for comparison purposes.
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\13\ The level and frequency of sounds masked by the ambient
will depend on the sound pressure level and shape of that ambient.
For a full description of the typical urban ambient used in this
study, see the full report cited in footnote 11.
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The results of this research show that synthetic sounds that
resemble those of an ICE produce detection distances similar to actual
ICE vehicles. Some of the synthetic sounds examined in the study that
were designed according to psychoacoustic principles produced detection
distances twice as long as those of ICE sounds. The study participants
had difficulty detecting synthetic sounds that contained only the
fundamental of the combustion noise of the engine (the lowest frequency
associated with the combustion).
This research examined four potential ways in which countermeasure
sounds could be specified. The study examined countermeasure sounds
based on recordings of ICE vehicles, synthetically generated
countermeasure sounds that emulate the sounds of an ICE, non-ICE like
countermeasure sounds designed for maximum detectability at a given
sound-pressure level, and synthetically generated sounds that have
special characteristics to enhance detection and characteristics that
ensure that the sounds contain ICE-like components to enhance
recognizability. The report noted that an objective specification for
non-ICE-like sounds is more difficult to develop than one for synthetic
sound generators that emulate the sound of typical ICEs. The report
also noted that the former approach could result in a wider variety of
sounds, some of which might be not recognized as a vehicle or might be
perceived as annoying.
In early 2011, NHTSA initiated additional research and data
collection activities to further support this rulemaking (Phase 3).
Acoustic measurements and analyses were completed to support the
development of specifications for alerting sounds and test procedures
for compliance with agency requirements. Acoustic data was gathered
from eight vehicles: four ICE vehicles and four EVs/HVs with alerting
sounds (one production and three prototype vehicles). The SAE J2889-1
test procedure was used to measure the sound levels for the stopped and
pass-by conditions. Acoustic measurements were completed on an ISO
10844:1994 noise pad. All HVs and EVs were measured in electric
propulsion mode.
Variations on SAE J2889-1 were used to explore other aspects such
as directivity, sound level as a function of vehicle speed, and to
capture binaural recordings. Directivity refers to the relative
proportions of acoustical energy
[[Page 2803]]
that is emitted from a source, in this case a vehicle, as a function of
direction to the front, back, left, and right. Binaural recordings were
captured for potential use in future research activities. Acoustic
measurements, modeling, and sound simulation tools were used to
identify sound attributes that aid in detection of alert sounds and
recognition of these sounds as a motor vehicle.
Two approaches were considered in the development of parameters for
alert sounds. In one approach, sound levels for the alert sound were
developed using loudness models and a calculation of safe detection
distances. In the other approach, sound levels for alert sounds were
based on the sound of current ICE vehicles. This research focused on
developing specifications that can be applied to all sounds and that
are objective and practical.
All of the research activities summarized above are described in
more detail in Section VI. NHTSA Research and Industry Practices.
III. Pedestrian Safety Enhancement Act of 2010
On January 4, 2011, the Pedestrian Safety Enhancement Act of 2010
(Public Law 111-373) was signed into law. The Pedestrian Safety
Enhancement Act (PSEA) requires NHTSA to conduct a rulemaking to
establish a Federal Motor Vehicle Safety Standard (FMVSS) \14\
requiring an ``alert sound'' \15\ for pedestrians to be emitted by all
types of motor vehicles \16\ that are electric vehicles \17\ (EVs) or
hybrid vehicles \18\ (HVs). The covered types of vehicles include light
vehicles (passenger cars, vans, sport utility vehicles and pickup
trucks), as well as LSVs, motorcycles, medium and heavy trucks and
buses. Trailers are specifically excluded from the requirements of the
PSEA. The PSEA requires NHTSA to establish performance requirements for
an alert sound that allows blind and other pedestrians to reasonably
detect a nearby EV or HV. The PSEA defines ``alert sound'' as a
vehicle-emitted sound that enables pedestrians to discern the presence,
direction,\19\ location, and operation of the vehicle.\20\ Thus, in
order for a vehicle to satisfy the requirement in the PSEA to provide
an ``alert sound,'' the sound emitted by the vehicle must satisfy that
definition. The alert sound must not require activation by the driver
or the pedestrian, and must allow pedestrians to reasonably detect an
EV or HV in critical operating scenarios such as constant speed,
accelerating, or decelerating. In addition to the operating scenarios
previously mentioned the definition of alert sound in the PSEA requires
the agency to establish requirements for a sound while the vehicle is
activated but stationary and when the vehicle is operating in reverse.
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\14\ NHTSA is delegated authority by the Secretary of
Transportation to carry out Chapter 301 of Title 49 of the United
States Code. See 49 CFR 501.2. This includes the authority to issue
Federal motor vehicle safety standards. 49 U.S.C. 30111.
\15\ The definition of that term is discussed below.
\16\ Section 2(4) defines the term ``motor vehicle'' as having
the meaning given such term in section 30102(a)(6) of title 49,
United States Code, except that such term shall not include a
trailer (as such term is defined in section 571.3 of title 49, Code
of Federal Regulations). Section 30102(a)(6) defines ``motor
vehicle'' as meaning a vehicle driven or drawn by mechanical power
and manufactured primarily for use on public streets, roads, and
highways, but does not include a vehicle operated only on a rail
line.
\17\ Section2(10) of the PSEA defines ``electric vehicle'' as a
motor vehicle with an electric motor as its sole means of
propulsion.
\18\ Section 2(9) of the PSEA defines ``hybrid vehicle'' as a
motor vehicle which has more than one means of propulsion. As a
practical matter, this term is currently essentially synonymous with
``hybrid electric vehicle.''
\19\ The PSEA does not specify whether vehicle ``direction'' is
to be defined with reference to the vehicle itself (thus meaning
forward or backward) or the pedestrian.
\20\ Section 2(2).
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The agency has concluded that the requirement in the PSEA that the
alert sound must allow pedestrians to ``discern vehicle presence,
direction, location, and operation,'' \21\ requires the agency to
establish minimum sound requirements for the stationary but activated
operating condition. The requirement that pedestrians be able to
discern vehicle presence must be read along with the requirements that
the sound allow pedestrians to discern direction, location, and
operation. The term ``presence'' means something that is in the
immediate vicinity. The term ``operation'' means a state of being
functional or operative. Read together the definition of alert sound
requires that pedestrians be able to detect vehicle presence when the
vehicle is in operation. A vehicle with an engaged ignition is in a
state of being functional even though it may not be moving. It is the
agency's position that the provision that pedestrians be able to detect
the presence of a vehicle that is turned on requires that the vehicle
emit a minimum sound level when the vehicle is stationary, but the
starting system is activated.
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\21\ Public Law 111-373, Sec. 2(2), 124 Stat. 4086 (2011).
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The agency believes that the PSEA requires the agency to establish
requirements for a sound while the vehicle is moving reverse for the
same reason that a sound while the vehicle is stationary is required.
The PSEA requires minimum sound level requirements promulgated by NHTSA
to allow pedestrians to discern vehicle presence and operation. A
vehicle moving in reverse is unquestionably operating, thus a minimum
sound level is required for this condition.
The PSEA also requires that the minimum sound level requirements
promulgated by NHTSA allow pedestrians to discern the direction of the
vehicle. This language also indicates that the PSEA requires any
standard to establish minimum sound requirements for when the vehicle
is operating in reverse.
Because the PSEA directs NHTSA to issue these requirements as a
FMVSS under the National Traffic and Motor Vehicle Safety Act (Vehicle
Safety Act),\22\ the requirements must comply with that Act as well as
the PSEA. The Vehicle Safety Act requires each safety standard to be
performance-oriented, practicable,\23\ and objective \24\ and meet the
need for safety. In addition, in developing and issuing a standard,
NHTSA must consider whether the standard is reasonable, practicable,
and appropriate for each type of motor vehicle covered by the standard.
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\22\ 49 U.S.C. Chapter 301.
\23\ In a case involving passive occupant restraints, the U.S.
Circuit Court of Appeals for the District of Columbia said that the
agency must consider public reaction in assessing the practicability
of required safety equipment like an ignition interlock for seat
belts. Pacific Legal Foundation v. Department of Transportation, 593
F.2d 1338 (D.C. Cir. 1978). cert. denied, 444 U.S. 830 (1979).
\24\ In a case involving passive occupant restraints, the U.S.
Circuit Court of Appeals for the 6th Circuit said, quoting the House
Report (H.R. 1776, 89th Cong. 2d Sess.1966, p. 16) for the original
Vehicle Safety Act, that ``objective criteria are absolutely
necessary so that `the question of whether there is compliance with
the standard can be answered by objective measurement and without
recourse to any subjective determination.' '' Chrysler v. Department
of Transportation, 472 F.2d 659 (6th Cir. 1972).
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As a FMVSS, the pedestrian alert sound system standard we are
proposing today would be enforced in the same fashion as other safety
standards issued under the Vehicle Safety Act. Thus, violators of the
standard would be subject to civil penalties.\25\ A vehicle
manufacturer would be required to conduct a recall and provide remedy
without charge if its vehicles were determined to fail to comply with
the standard or if the vehicle's alert sound were determined to contain
a safety related defect.\26\
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\25\ 49 U.S.C. 30112 and 30165.
\26\ 49 U.S.C. 30118-30120.
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Under the PSEA, the standard must specify performance requirements
for an alert sound that enables blind and other pedestrians to
reasonably detect EVs
[[Page 2804]]
and HVs operating below their cross-over speed.\27\ The PSEA specifies
several requirements regarding the performance of the alert sound to
enable pedestrians to discern the operation of vehicles subject to the
Act. First, the alert sound must be sufficient to allow a pedestrian to
reasonably detect a nearby EV or HV operating at constant speed,
accelerating, decelerating and operating in any other scenarios that
the Secretary deems appropriate.\28\ Second, it must reflect the
agency's determination of the minimum sound level emitted by a motor
vehicle that is necessary to allow blind and other pedestrians to
reasonably detect a nearby EV or HV operating below the cross-over
speed.\29\ NHTSA plans to ensure that EVs and HVs are detectable to
pedestrians by specifying performance requirements for sound emitted by
these vehicles so that they will be audible to pedestrians in the
ambient noise environment typical of urban areas.
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\27\ Section 2(3) of the PSEA defines ``cross-over speed'' as
the speed at which tire noise, wind resistance, or other factors
make an EV or HV detectable by pedestrians without the aid of an
alert sound. The definition requires NHTSA to determine the speed at
which an alert sound is no longer necessary.
\28\ Section 3(a). Under the PSEA, as with most legislation like
it, the Secretary of Transportation delegates responsibility for
achieving the legislation's objectives to the appropriate Department
of Transportation Administration, in this case NHTSA.
\29\ Section 3(b).
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Nothing in the PSEA specifically requires the alert sound to be
electrically generated. Therefore, if manufacturers wish to meet the
minimum sound level requirements specified by the agency through the
use of sound generated by the vehicle's power train or any other
vehicle component, there is nothing in the PSEA to limit their
flexibility to do so.
The alert sound must also reflect the agency's determination of the
performance requirements necessary to ensure that each vehicle's alert
sound is recognizable to pedestrians as that of a motor vehicle in
operation.\30\ We note that the requirement that the alert sound be
recognizable as a motor vehicle in operation does not mean that the
alert sound be recognizable as a vehicle with an internal combustion
engine (ICE). The PSEA defines ``conventional motor vehicle'' as ``a
motor vehicle powered by a gasoline, diesel, or alternative fueled
internal combustion engine as its sole means of propulsion.'' \31\ If
Congress had intended the alert sound required by the PSEA to be
recognizable as an ICE vehicle, Congress would have specified that the
sound must be recognizable as a ``conventional motor vehicle'' in
operation rather than a motor vehicle because Congress acts
purposefully in its choice of particular language in a statute.\32\
While the mandate that NHTSA develop performance requirements for an
alert sound that is recognizable as a motor vehicle does not mean that
the sound must be based solely on sounds produced by ICE vehicles, the
mandate does impose substantive requirements that the agency must
follow during the rulemaking. The Vehicle Safety Act defines a motor
vehicle as a ``vehicle driven or drawn by mechanical power and
manufactured primarily for use'' on public roads.\33\ The requirement
that the agency develop performance requirements for recognizability
means that the pedestrian alert sound required by this standard must
include acoustic characteristics common to all sounds produced by
vehicles driven by mechanical power that make those sounds recognizable
as a motor vehicle based on the public's experience and expectations of
those sounds. For example, pitch shifting and increases in sound
pressure level denote changes in speed and are common to all vehicles
driven by mechanical power. Further, sounds that the public currently
recognizes as generated by a vehicle driven by mechanical power have
tonal components.
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\30\ Section 3(b)(2).
\31\ Section 2(5).
\32\ Keene Corp. v. United States, 508 U.S. 200, 208 (1993).
\33\ 49 U.S.C. Sec. 30102(a)(6).
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The PSEA mandates that the standard shall not require the alert
sound to be dependent on either driver or pedestrian activation. It
also requires that the safety standard allow manufacturers to provide
each vehicle with one or more alert sounds that comply, at the time of
manufacture, with the safety standard. Thus, a manufacturer may, if it
so chooses, equip a vehicle with different sounds to denote different
operating scenarios, such as reverse or start up. Each vehicle of the
same make and model must emit the same alert sound or set of sounds.
The standard is required to prohibit manufacturers from providing
anyone, other than the manufacturer or dealers, with a device designed
to disable, alter, replace or modify the alert sound or set of sounds
emitted from the vehicle. A manufacturer or a dealer, however, is
allowed to alter, replace, or modify the alert sound or set of sounds
in order to remedy a defect or non-compliance with the safety standard.
Additionally, vehicle manufacturers, distributors, dealers, and motor
vehicle repair businesses would be prohibited from rendering the sound
system inoperative under Section 30122 of the Vehicle Safety Act.
It is the agency's intention that the requirements of this standard
be technology neutral. For this reason, we have chosen to establish
minimum sound requirements for a vehicle-level test. The agency
recognizes that, in the near term, most manufacturers would install
speaker systems that emit synthetically developed sounds in order to
meet the requirements of the proposed standard.
The agency interprets the requirement in the PSEA that each vehicle
of the same make and model emit the same sound as applying only to
sound added to a vehicle for the purposes of complying with this
proposed standard. We also interpret the PSEA requirement that NHTSA
prohibit manufacturers from providing anyone with a means of modifying
or disabling the alert sound and the prohibition on making required
safety systems inoperative contained in Section 30122 of the Vehicle
Safety Act as applying only to sound added to a vehicle for the
purposes of complying with this proposed standard.
Many changes to a vehicle could affect the sound produced by that
vehicle. In issuing this proposal the agency does not wish to prevent
manufacturers, dealers, and repair businesses from making modifications
to a vehicle such as adding a spoiler or changing the vehicle's tires
that may have the effect of changing the sound produced by the vehicle.
The agency will test to ensure sounds produced by two vehicles of
the same model are the same (within 3 A-weighted dB) at the stationary
condition so that a determination of the sameness of the sounds is not
dependent on tire or wind noise or other factors that could influence a
vehicle's sound output. The agency will not consider any modifications
made to a vehicle that affect the mechanical, tire or wind noise
produced by that vehicle to make an alert sound added to the vehicle
inoperative.
The PSEA requires NHTSA to consider the overall community noise
impact of any alert sound required by the new safety standard. In
addition, NHTSA will consider the environmental analysis required by
the National Environmental Policy Act (NEPA) when setting the standard.
As part of the rulemaking process, NHTSA is required to consult
with various other organizations. This is further described in Section
IV below.
[[Page 2805]]
In addition to requiring NHTSA to publish a final rule establishing
the standard requiring an alert sound for EVs and HVs by January 4,
2014, the PSEA requires that the agency provide a phase-in period, as
determined by NHTSA. However, full compliance with the standard must be
achieved for all vehicles manufactured on or after September 1st of the
calendar year beginning three years after the date of publication of
the final rule. Thus, if the final rule were promulgated sometime in
2014, the three-year period after the date of publication of the final
rule would end sometime in 2017. The first calendar year that would
begin after that date in 2017 would be calendar year 2018. Thus, under
that time scenario, full compliance would be required not later than
September 1, 2018.
Finally, the PSEA requires NHTSA to conduct a study and report to
Congress whether the agency believes that there is a safety need to
require the alert sounds required by the FMVSS promulgated to meet the
mandate of the Act for some motor vehicles with internal combustion
engines. The report must be submitted to Congress by January 4, 2015.
If NHTSA determines that there is a safety need to require alert sounds
for those motor vehicles the agency must initiate a rulemaking to
require alert sounds for them.
IV. Consultation With External Organizations
NHTSA is required by the PSEA to consult with the following
organizations as part of this rulemaking: The Environmental Protection
Agency (EPA) to assure that any alert sound required by the rulemaking
is consistent with noise regulations issued by that agency; consumer
groups representing visually-impaired individuals; automobile
manufacturers and trade associations representing them; technical
standardization organizations responsible for measurement methods such
as the Society of Automotive Engineers, the International Organization
for Standardization, and the United Nations Economic Commission for
Europe (UNECE), World Forum for Harmonization of Vehicle Regulations
(WP.29).
The agency has established three dockets to enhance and facilitate
cooperation with outside entities including international
organizations. The first docket (No. NHTSA-2008-0108) \34\ was created
after the 2008 public meeting was held; it contains a copy of the
notice of public meeting in the Federal Register, a transcript of the
meeting, presentations prepared for the meeting and comment
submissions. It also includes NHTSA's research plan, our ``Notice of
Intent to Prepare an Environmental Assessment for the Pedestrian Safety
Enhancement Act of 2010'' published on July 12th 2011 in the Federal
Register, and the agency's Phase 1 and 2 research reports. (The Notice
of Intent [NOI] and the agency's research are discussed more fully
later in this document.) The second docket (No. NHTSA-2011-0100) \35\
was created to collect comments on the NOI; it also includes a copy of
that notice. The third docket (No. NHTSA-2011-0148) \36\ was created in
September 2011 to include materials related to the rulemaking process
(``The Pedestrian Safety Enhancement Act of 2010'', Phase 1 and 2
research reports, statistical reports, meeting presentations, etc.),
outside comments and items to be released in the future up to and
including this Notice of Proposed Rulemaking.
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\34\ http://www.regulations.gov/#!searchResults;rpp=10;po=0;s=NHTSA-2008-0108.
\35\ http://www.regulations.gov/#!searchResults;rpp=10;po=0;s=%252BNHTSA-2011-0100.
\36\ http://www.regulations.gov/#!searchResults;rpp=10;po=0;s=NHTSA-2011-0148.
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NHTSA has since 2009 also been hosting a series of roundtable
meetings with industry, technical organizations and groups representing
people who are visually-impaired. Below are the dates and topics of
discussion:
April 14th, 2009: Status of Phase 1 research and industry
updates.
August 4th, 2009: Phase 1 research plan.
January 25th, 2010: Final results of Phase 1 research and
industry updates.
June 24th, 2010: Phase 2 research plan and status of Phase
2 work.
February 22nd, 2011: Final results of Phase 2 research.
Attendees were asked to submit comments.
The following organizations have been participating in these
meetings: The Alliance of Automotive Manufacturers, the Global
Automakers (formerly Association of International Automobile
Manufacturers (AIAM)), American Council of the Blind, The American
Foundation of the Blind (AFB), the National Federation of the Blind
(NFB), The International Organization for Standardizations (ISO), The
Society of Automotive Engineers (SAE), the International Organization
of Motor Vehicles Manufacturers (OICA), The Environmental Protection
Agency (EPA) and Japan Automobile Manufacturers Association (JAMA).
Representatives of the EPA have also been included in our
activities with outside organizations. They have been kept updated on
our research activities and have actively participated in our outreach
efforts. NHTSA has also kept up to date on EPA activities on the
international front through the activities of the UNECE Working Party
of Noise (GRB).
The American Foundation of the Blind, the American Council of the
Blind and the National Federation of the Blind have provided NHTSA with
invaluable information about visually-impaired pedestrian safety needs
since the 2008 Public Meeting was held.
The Alliance of Automotive Manufacturers and Global Automakers
(formerly the Association of International Automobile Manufacturers
(AIAM)) have met separately with the agency to discuss our research
findings and their ideas regarding this rulemaking. Members of both
organizations have also met separately with the agency to discuss their
own research findings and ideas for a potential regulatory approach to
address the safety issues of interest to the agency.
Automotive manufacturers that produce EVs for the U.S. market have
developed various pedestrian alert sounds, recognizing that these
vehicles, when operating at low speeds, may pose an elevated safety
risk to pedestrians. They have made vehicles with sound alert systems
available for lease by NHTSA for research purposes. This information
has been helpful in the agency decision making process.
The Society of Automotive Engineers (SAE) established the Vehicle
Sound for Pedestrians (VSP) subcommittee in November 2007 with the
purpose of developing a recommended practice to measure sounds emitted
by ICE vehicles and alert sounds for use on EVs and HVs. Their efforts
resulted in standard SAE J2889-1, Measurement of Minimum Noise Emitted
by Road Vehicles.\37\ The agency has been sending liaisons to the VSP
meetings since 2008. SAE is the U.S. technical advisory group to the
International Organization for Standardizations (ISO) and they both
have cooperated in the development of the standard. The ISO document
(ISO/NP 16254 Measurement of minimum noise emitted by road vehicles)
\38\ and SAE document are reported to be technically identical but this
has not been confirmed by NHTSA at this time. The agency is currently
using standard
[[Page 2806]]
SAE J2889-1 and ISO10844 \39\ as references in the test procedure
development.
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\37\ http://standards.sae.org/j2889/1_201109.
\38\ http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=56019.
\39\ http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=45358.
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The UNECE World Forum WP.29 determined that road transportation
vehicles propelled in whole or in part by electric means present a
danger to pedestrians and directed the Working Party on Noise (GRB) to
assess what necessary steps WP.29 should take to help mitigate the
problem. In response, GRB established an informal group on Quiet Road
Transport Vehicles (QRTV) \40\ to carry out the necessary activities to
address the quieter vehicles issue and the potential need for global
harmonization. NHTSA has been participating in the QRTV's meetings
since its foundation in 2010 and has kept the group informed about
ongoing agency research activities as well as the results from
completed research studies.
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\40\ Papers relating to the informal group periodic meetings may
be found at http://live.unece.org/trans/main/wp29/wp29wgs/wp29grb/qrtv_1.html, http://live.unece.org/trans/main/wp29/wp29wgs/wp29grb/qrtv_2.html, http://live.unece.org/trans/main/wp29/wp29wgs/wp29grb/qrtv_3.html, http://live.unece.org/trans/main/wp29/wp29wgs/wp29grb/qrtv_4.html, http://live.unece.org/trans/main/wp29/wp29wgs/wp29grb/qrtv_5.html, and http://live.unece.org/trans/main/wp29/wp29wgs/wp29grb/qrtv_6.html.
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At its March 2011 meeting, WP.29 adopted guidelines covering alert
sounds for electric and hybrid vehicles that are closely based on the
Japanese guidelines discussed more fully later in this document. The
guidelines were published as an annex to the UNECE Consolidated
Resolution on the Construction of Vehicles (R.E.3).
Considering the international interest and work in this new area of
safety, the U.S. has proposed working on a new GTR, with Japan as co-
sponsor, to develop harmonized pedestrian alert sound requirements for
electric and hybrid-electric vehicles under the 1998 Global Agreement.
WP.29 is now working to develop a GTR that will consider international
safety concerns and leverage expertise and research from around the
world. Meetings of the working group are planned to take place
regularly with periodic reports to WP.29 until the expected
establishment date for the new GTR in November 2014. NHTSA is currently
leading the GTR development process.
Other international organizations, such as the International
Organization of Motor Vehicles Manufacturers (OICA) and Japan
Automobile Manufacturers Association (JAMA) have been providing NHTSA
with their own research findings and have also been attending our quiet
vehicle meetings.
V. Safety Problem
A. Comparing the Vehicle to Pedestrian Crash Experience of ICE Vehicles
and HVs and EVs
Crash Risk
Passenger hybrid electric vehicles first became available to
consumers in 2000, and their numbers as well as their proportion of the
passenger vehicle fleet have risen every year since their introduction.
According to the R.L. Polk and Company National Vehicle Population
Profile, there were 18,628 registered passenger HVs in 2001. By 2004,
there were 145,194 registered HVs comprising 0.1 percent of the
passenger vehicle fleet. By 2009, the number had grown to 1,382,605
registered HVs comprising 0.6 percent of the fleet.
Advocacy groups have raised pedestrian safety concerns regarding
HVs because a vehicle using an electric motor may be quieter than an
ICE vehicle and may not emit the sounds that non-motorists rely on for
warning as vehicles approach them. In 2009, NHTSA released the report
``Incidence of Pedestrian and Bicyclist Crashes by Hybrid Electric
Passenger Vehicles'' which found that, when comparing similar vehicles,
77 out of 8,387 total HVs reported to be in any crash incident were
involved in pedestrian crashes, and 3,578 out of 559,703 total ICE
vehicles were involved in similar pedestrian crashes.\41\ The report
used data collected from 12 individual states. The years for which data
was available varied across different states. Generally, the data used
ranged from the years 2000 to 2006. HV crashes had an overall 40
percent higher chance to involve pedestrians. In situations involving
certain low-speed maneuvers, HVs were twice as likely to be involved in
a pedestrian crash as ICE vehicles in similar situations. The state
data set that NHTSA used to determine the pedestrian and pedalcyclist
crash rates for HVs did not include any information about the vision
status of the pedestrians involved in the crashes. Therefore, we were
unable to determine whether any of the pedestrians involved in these
crashes were blind or visually impaired.
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\41\ See footnote 6.
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A recent analysis updated and verified these previous findings \42\
by adding additional years of state crash files as well as by
increasing the number of states included in the analysis from 12 to 16,
with a total of 24,297 HVs (approximately three times the HVs of the
2009 study) and 1,001,000 ICE vehicles by Honda and Toyota, with five
different models, in 16 States during 2000-2008. This updated analysis
indicates that a total of 186 HVs and 5,699 ICE vehicles were involved
in pedestrian crashes. A total of 116 HVs and 3,052 ICE vehicles were
involved in crashes with bicycles. Overall, a statistical analysis
referred to as odds ratios indicates that the odds of an HV being in
either a pedestrian or bicycle crash is greater than the odds of an ICE
vehicle being in a similar crash, 19 percent higher for pedestrian
crash odds and 38 percent higher for bicycle crash odds.\43\ The crash
factors of speed limit, vehicle maneuver and location were examined to
determine the relative incidence rates of HVs versus ICE vehicles and
whether the odds ratio was different under different circumstances.
This finding also indicates that the largest differences between the
involvement of HVs and ICE vehicles in pedestrian crashes occur with
speed limits of 35 mph and lower and during certain, typically low-
speed, maneuvers such as making a turn, starting up, and pulling into
or backing out of a parking space. HVs were about 1.38 times more
likely to be involved in a pedestrian crash than a vehicle with an ICE
after completing a low speed maneuver. The results in this updated
analysis show trends similar to those first reported in our 2009
report. The sample sizes of pedestrian or bicycle crashes were verified
to validate the sufficient statistical powers in this updated analysis.
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\42\ Wu et al. (2011) Incidence Rates of Pedestrian And
Bicyclist Crashes by Hybrid Electric Passenger Vehicles: An Update,
Report No. DOT HS 811 526. Dept. of Transportation, Washington, DC.
Available at http://www-nrd.nhtsa.dot.gov/Pubs/811526.pdf.
\43\ The incidence rates for pedestrian and pedalcyclist crashes
involving HVs and EVs were calculated from the State data by
comparing the pedestrian and pedalcyclist crash rates for all HVs
contained in the State data set with the crash rates for all ICE
vehicles from that data set. Because this proposal does not apply to
HVs that always have their ICE on while moving, the agency removed
the Honda Civic and the Honda Accord from the HV category and
included those vehicles in the calculations as ICE vehicles in
estimating the incidence rate used in the benefit calculations.
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The rate of crashes between HVs and pedalcyclists was different
than the rate of crashes between HVs and pedestrians. While a larger
percentage of pedalcyclist crashes for both HVs and ICE vehicles
occurred at posted speed limits of 35 mph and below, the difference in
rates of pedalcyclist crashes between HVs and ICE vehicles was higher
at speed limits above 35 mph that at speed limits of 35 mph and below.
For posted speed limits of 35 mph and below HVs showed an
[[Page 2807]]
increased rate of pedalcyclist crashes when compared to ICE vehicles,
however, the results were not statically significant. The difference in
pedealcyclist crash rates between HVs and ICE vehicles was also greater
when driving straight as compared to low-speed maneuvers.
This updated analysis further included all vehicle models from all
manufacturers during the period covered by the study, beyond the five
models from Toyota and Honda, and a similar pedestrian crash trend was
also found from the expanded data. Comparisons restricted to HV and
similar ICE pairs (Prius and Corolla; Civic HV and ICE model) only were
also made. These comparisons also resulted in similar conclusions about
HV pedestrian crashes relative to ICE vehicle pedestrian crashes,
including that the odds of an HV being in a pedestrian crash is greater
than the odds of an ICE vehicle being in a similar crash.
Despite the similarities in the overall sound level produced by the
two vehicles, the differential crash rate for the Civic HV and the ICE
version of the Civic was even larger than for other pairs of HVs and
ICEs. We note that the HV Civic is much different than the other hybrid
vehicles in the analysis because when the agency tested this vehicle,
we could not get the ICE engine to shutoff even at idle. Thus, unlike
the other HVs tested, the ICE was always on in this vehicle, but we
acknowledge that in the real-world, the ICE may shut-off at some point.
We do know that, although sound levels are similar, there are
differences between the frequency profile of the HV and ICE Civics, but
we do not know how pedestrians would perceive this difference either in
general or in the low-speed maneuvers used in our crash analysis. The
agency seeks comments on whether the differences in pedestrian crash
rates between HVs and ICEs are solely due to a pedestrians' inability
to detect the vehicle based on the vehicle's sound while operating
below the crossover speed or whether there may be other factors that we
have not identified that affect the difference in crash rates between
the two types of vehicles.
While this updated analysis provides insightful comparisons of the
incidence rates of HVs versus ICE vehicles involved in pedestrian
crashes, there are some limitations to consider: the use of data from
16 states cannot be used to directly estimate the national problem
size; there is still not enough data to draw conclusions in all
scenarios of interest such as for individual low-speed maneuvers like
making a turn, starting up, or in parking lots.
Fatalities
The Fatality Analysis Reporting System (FARS) contains a census of
all traffic fatalities. HVs and EVs that struck and killed a pedestrian
were identified using the Vehicle Identification Numbers (VINs)
contained in the 2001 through 2009 FARS files. During this period,
there were 53 pedestrian fatalities attributed to crashes involving 47
HVs and EVs. Almost all of these fatalities (47 of the 53) involved
vehicles that were identified as passenger vehicles. In 2008, there
were 10 HVs or EVs that struck and killed 10 pedestrians, and in 2009,
there were 11 HVs or EVs that struck and killed 11 pedestrians.
However, these fatalities are not included in the target population
for analysis under this rulemaking for two reasons. The first is that
pedestrian fatalities are not as likely to occur at low speeds for
which the rate of HV pedestrian collisions is significantly higher than
collisions between ICE vehicles and pedestrians. This proposal would
establish minimum sound requirements for hybrid and electric vehicles
operating at speeds of 30 km/hr (18 miles per hour (mph)) and below. A
majority of pedestrian fatalities occur when the vehicle involved in
the collision is travelling at a speed greater than 18 mph. Overall, 67
percent of the pedestrian fatalities involving HVs or EVs and with
known speed limits occurred at a speed limit above 35 mph. For all
pedestrian fatalities with known speed limits, 62 percent occurred at a
speed limit above 35 mph and 61 percent of those involving passenger
vehicles occurred at a speed limit above 35 mph. The goal of this
proposal is to prevent injuries to pedestrians that result from
pedestrians being unable to hear nearby hybrid and electric vehicles.
At speeds of 35 mph and above, at which a majority fatal crashes
involving pedestrians occur, the sound levels produced by hybrid and
electric vehicles are the same as the sound levels produced by ICE
vehicles. Therefore, establishing minimum sound requirements for hybrid
and electric vehicles operating at low speeds is not expected to have
an impact on pedestrian fatalities.
The second reason is that the rate of pedestrian fatalities per
registered vehicle for HVs and EVs is not larger (and is in fact lower)
than that for ICE vehicles. Using 2008 data, the fatality rate for
pedestrians in crashes with HVs and EVs is 0.85 fatalities per 100,000
registered vehicles, and the corresponding rate for ICE vehicles is
1.57 per 100,000 vehicles.
There also could be fatalities involving HVs and EVs that occur in
non-traffic crashes in places such as driveways and parking lots.
However, a comprehensive search for HVs and EVs involved in pedestrian
fatalities could not be undertaken because NHTSA's Not in Traffic
Surveillance (NiTS) system does not provide VINs, and a search for
model names that indicate hybrid or electric vehicles did not identify
any crashes involving pedestrian fatalities.
B. Need for Independent Mobility of People Who Are Visually Impaired
In addition to addressing the safety need in the traditional sense
of injuries avoided as a result of preventing vehicle-pedestrian
crashes, NHTSA believes it is important to note another dimension of
safety that should be taken into account with respect to pedestrians
who are blind or visually impaired. Pedestrians who are blind or
visually impaired need to be able to travel independently and safely
throughout their communities without fear of injury, both as a result
of collisions with motor vehicles and as a result of other adverse
events in the environments they must negotiate. To a far greater extent
than is the case for sighted people, vehicle sounds help to define a
blind or visually-impaired person's environment and contributes to that
person's ability to negotiate through his/her environment in a variety
of situations.\44\
---------------------------------------------------------------------------
\44\ National Federation of the Blind (2011) How People Who are
Blind Use Sound for Independent Travel, memorandum to the docket
NHTSA-2011-0148, Washington, DC. This memorandum is the source for
this information.
---------------------------------------------------------------------------
Two long-established navigation aids that visually-impaired people
use are the white cane and a guide dog. The modern white cane and the
techniques for its use help the user to navigate and allow sighted
people to recognize that a person is blind or visually impaired. Today,
the ``structured discovery'' method of teaching independent travel for
visually-impaired people emphasizes learning to use information
provided by the white cane, traffic sounds, and other cues in the
environment to travel anywhere safely and independently, whether the
individual has previously visited the place or not.
Of the thirteen guide dog schools currently operating in the United
States, most require applicants for guide dogs to have at least some
skill in traveling with a long white cane, since the basic techniques
for using a white cane and a guide dog are similar in many
[[Page 2808]]
respects. A guide dog does not lead a person but simply guides him or
her around obstacles; the handler is still responsible for navigation.
Whether a blind or visually-impaired person uses a white cane or
guide dog, the primary purpose of both travel tools is to help the
blind traveler identify and/or avoid obstacles in his or her path using
the sense of touch. The remaining information needed by a blind or
visually-impaired person to travel safely and independently is provided
primarily through the sense of hearing.
When traveling with a white cane or guide dog, the primary sound
cue used by blind pedestrians is the sound of vehicle traffic, which
serves two purposes: navigation and collision avoidance. Navigation
involves not only ascertaining the proper time to enter a crosswalk and
maintain a straight course through an intersection while crossing, but
also the recognition of roadways and their traffic patterns and their
relationship to sidewalks and other travel ways a blind or visually-
impaired person might use.
Sound emitted by individual vehicles, as opposed to the general
sound of moving traffic, is critical. The sound of individual vehicles
alerts blind travelers to the vehicle's location, speed, and direction
of travel. For example, a blind or visually-impaired person moving
through a parking lot can hear and avoid vehicles entering or exiting
the lot or looking for parking spaces; a blind person walking through a
neighborhood can hear when a neighbor is backing out of a driveway. The
vehicle sound also indicates to a blind or visually-impaired pedestrian
whether a vehicle is making a turn, and if so, in which direction. The
sound of individual vehicles also allows the blind traveler to detect
and react to unusual or unexpected vehicle movement.
The sound of a vehicle that has an activated starting system but is
stationary (usually referred to as ``idling'' for vehicles with
internal combustion engines) alerts the blind or visually-impaired
traveler to the fact that the vehicle is not simply parked and that it
may move at any moment. The sound of a vehicle starting is important
for the same reason. If a blind person is approaching a driveway and
notes a vehicle that is stationary but running, or hears a vehicle
start, he or she will wait for the vehicle to pull out, or for an
indication that it will not, for example by noting that the vehicle
remains stationary for some time, indicating that the driver has no
immediate plans to move.
Because traffic sound is a navigation aid for blind and visually-
impaired pedestrians, as well as an indispensable part of traveling
safely, blind people listen to the sound of traffic actively and
constantly when they are walking, even when they are not at an
intersection. The sound of traffic helps blind individuals follow the
roadway; this is critical, even when there is a sidewalk, to keep the
blind individual on course. Traffic sounds also allow the detection of
roadway changes like curves, forks, or merges. The sound of traffic is
particularly important in negotiating intersections. By listening to
the traffic, a blind or visually-impaired traveler can determine how
the intersection is controlled (traffic signal, stop sign, etc.); how
many lanes of traffic are involved; and any unusual characteristics of
the intersection (e.g., three-way intersections or roundabouts). These
determinations can be made by listening to the sounds of vehicle
engines--often through one or two entire signal cycles--to determine
driver behavior, which is usually a reliable indicator of the
characteristics of the intersection. This includes the sound of
stationary vehicles--particularly in multi-lane or oddly shaped
intersections--because it is important to identify which lanes of
traffic are active, when, and for how long; and to then follow the line
of traffic that most nearly parallels the direction in which the
traveler wishes to proceed. At the same time that the blind traveler is
listening to the overall traffic pattern, he or she also listens for
cues from individual vehicles, particularly when determining the
precise moment to enter the crosswalk. At signaled intersections, an
idling vehicle in the street parallel to the path of the traveler that
accelerates and moves through the intersection is an indication that a
traffic signal has just changed and that it is safe to proceed into the
cross street, with maximum time to complete the crossing. In general,
by crossing when the traffic flow is parallel to him or her, a blind
individual can safely cross most intersections without difficulty. The
individual will use the sound of the parallel traffic while crossing to
maintain a roughly straight line through the intersection. Figure 1
shows several examples of how a blind pedestrian would use the sound of
traffic to cross a complex intersection.
Example 1: A blind pedestrian standing at corner A (facing
corner B) ready to cross, will wait for the stationary vehicles
behind him/her to start moving as an indication that the traffic
light has changed. Then, the pedestrian will proceed to cross the
street and follow the parallel line of traffic on his left (from A
to B) confident there is enough time to safely cross the street.
Example 2: A blind pedestrian standing at corner A (facing
corner C) ready to cross, will use the sound of the stationary
vehicles on his/her left and the parallel traffic on his/her right
as guides to follow a straight path while crossing.
Example 3: A blind pedestrian at corner C (facing corner D)
ready to cross, will wait for the traffic from C to A to stop and
the parallel traffic across the intersection to start, to safely
walk from corner C to Corner D. The sounds from the stationary
vehicles on his/her left and the parallel traffic across the
intersection serve as guides to keep a straight path while crossing.
[[Page 2809]]
[GRAPHIC] [TIFF OMITTED] TP14JA13.029
Using the white cane or guide dog and the sound of traffic, people
who are blind or visually-impaired have been able to navigate safely
and independently for decades. Blind and visually-impaired people
travel to school, the workplace, and throughout their communities to
conduct the daily functions of life primarily by walking and using
public transportation. Safe and independent pedestrian travel is
essential for blind or visually-impaired individuals to obtain and
maintain employment, acquire an education, and fully participate in
community life. Short of constantly traveling with a human companion, a
blind or visually-impaired pedestrian simply cannot ensure his or her
own safety or navigate effectively without traffic sound. To the extent
that there are more and more HVs and EVs on the road that are hard to
detect, people who are blind or visually impaired will lose a key
means--the sound of traffic--by which they determine when it is safe to
cross streets, but also by which they orient themselves and navigate
safely throughout their daily lives, avoiding dangers other than
automobiles.
VI. NHTSA Research and Industry Practices
On May 6, 2009 NHTSA issued a research plan describing the research
relating to quieter vehicles it planned to conduct. This section
reports on the research completed to date.
A. NHTSA Phase 1 Research \45\
---------------------------------------------------------------------------
\45\ see footnote 8.
---------------------------------------------------------------------------
In April 2010 NHTSA released a report titled ``Quieter Cars and the
Safety of Blind Pedestrians: Phase 1'' referred to as Phase 1. This
report documented a study conducted by the John A. Volpe National
Transportation Systems Center (Volpe) under an interagency agreement.
This study documents the overall sound levels and general spectral
content for a selection of HVs and ICE vehicles in different operating
conditions, evaluates vehicle detectability for two ambient sound
levels, and considers countermeasure concepts. The study investigated
operating scenarios of concern for pedestrians who are blind or
visually impaired, documented acoustic measurements of hybrid, electric
and ICE vehicles and ambient environments in which blind or visually
impaired pedestrians might reasonably be expected to make travel
decisions based on sound alone, examined the auditory detectability of
vehicles in safety scenarios of concern to individuals who are blind or
visually impaired and examined potential countermeasures.
Safety Scenarios for Pedestrians Who Are Blind or Visually-Impaired
As part of Phase 1 research NHTSA sought to identify operating
scenarios necessary for the safety of visually-impaired pedestrians.
The researchers identified these scenarios based on crash data,
literature reviews, and unstructured conversations with blind
pedestrians and orientation and mobility specialists. Scenarios were
defined by combining pedestrian vehicle environments, vehicle type,
vehicle maneuver/speed/operation, and considerations of ambient sound
level. The operating scenarios identified in Phase 1 are:
Vehicle approaching at low speed: One of the strategies
used by pedestrians who are blind is to cross when the road is quiet.
This technique assumes that it is safe to proceed when a vehicle is
loud enough to be heard far enough away, there are no other masking
sounds present, and no other vehicles are detected.
Vehicle backing out (as if coming out of a driveway):
There is a concern
[[Page 2810]]
quieter vehicles may not be detectable when backing out. This scenario
is complex for pedestrians since it is difficult to anticipate where
there may be a driveway and the driver's visibility may be limited. The
pedestrian may have limited time to react and respond to avoid a
conflict.
Vehicle travelling in parallel and slowing: Pedestrians
who are blind often need to distinguish between a vehicle moving
through an intersection and a vehicle turning into their path. The
pedestrian needs to perceive this information when the vehicle is in
the parallel street, before it turns into his or her path. The sound of
slowing vehicles in the parallel street helps pedestrians identify
turning vehicles.
Vehicle accelerating from stop: Pedestrians who are blind
use the sound of traffic in the parallel street to establish alignment
and to identify a time to cross. The sound of accelerating vehicles in
the parallel street indicates, for example, that the perpendicular
traffic does not have the right of way and thus a crossing opportunity
is available. Pedestrians may initiate their crossing as soon as they
detect the surge of parallel traffic or may delay the decision to make
sure traffic is moving straight through the intersection and not
turning into their path. A delay in detecting the surge of parallel
traffic may impact the opportunity to complete a crossing within the
designated walking interval.
Vehicle stationary: The sound of vehicles idling provides
important cues. For example, the sound of a vehicle in the far lane
gives cues about the width of the road (number of lanes), and conveys
information about the distance to walk and the time needed to navigate
across the street. A quieter vehicle may not be detected when it is
stationary at intersections or parking lots and it may start moving
suddenly at the same time a pedestrian enters the conflicting path.
NHTSA was able to gather crash data for collisions involving
pedestrians and HVs when the HV was operating in one of the scenario
described above (the crash report did not separately analyze vehicle
starting from a stop and the vehicle stationary conditions) immediately
prior to the crash in both the crash report released by NHTSA in
September of 2009 \46\ and the updated crash report released in October
2011.\47\ The 2011 report analyzed the crash rates for vehicles making
a turn, slowing/stopping, backing, entering and leaving a parking
space/driveway and starting in traffic separately and then analyzed all
those operating conditions together. Because of the sample size an
independent odds ratio was not available for any of the scenarios. When
taken together, however, these low speed operating conditions show a
statistically significant 1.38 odds ratio showing an increased risk of
pedestrian collisions.
---------------------------------------------------------------------------
\46\ See footnote 7,
\47\ See footnote 39.
---------------------------------------------------------------------------
For this study, the sounds emitted by HVs and ICE vehicles were
measured and recorded under operating conditions representative of the
previously identified safety scenarios.\48\ The operating conditions
were as follows: (1) a vehicle backing up at 5 mph (mimicking a vehicle
backing out of a driveway); (2) a vehicle slowing from 20 to 10 mph
(mimicking a vehicle preparing to turn right from the parallel street);
(3) a vehicle approaching at a low constant speed (6 mph and 10 mph);
(4) a vehicle accelerating from a stop; and (5) a vehicle idling.
Average A-weighted sound levels for each of the six vehicles tested are
reported in Table 1.
---------------------------------------------------------------------------
\48\ The SAE J2889-1 draft test method covers only two operating
conditions: stationary vehicle and 10 km/h (6 mph) constant speed
pass by. This study follows recommendations of the SAE draft method
with regard to instrument settings, calibration, meteorological
monitoring, etcetera; however, it deviates from the SAE method with
respect to operating condition, data measured, as well as height,
distance, and orientation of the microphones. For each measurement,
one-half second contiguous average SPLs were measured. The maximum
of these for each event were analyzed for the development of Table
1. These levels are representative of the sound level when the
vehicle is at or near the microphone line (line PP' in SAE J2889-1,
Figure 1).
Table 1--Overall A-Weighted Sound Level at the Microphone Location (12 ft)
[Average A-weighted level, LAeq0.5s, dB]
--------------------------------------------------------------------------------------------------------------------------------------------------------
2009 Toyota
Scenario/vehicle operation 2010 Toyota 2009 Toyota Honda Civic Honda Civic Highlande 2008 Toyota
Prius Matrix Hybrid ICE Hybrid Highlander
--------------------------------------------------------------------------------------------------------------------------------------------------------
Approaching at 6 mph.................................... 44.7 53.5 49.3 52.0 53.2 55.5
Backing out (5 mph)..................................... 44.2 51.3 48.5 58.2 45.9 52.7
Slowing from 20 to 10 mph............................... 53.0 54.2 56.6 55.0 53.0 55.4
Acceleration............................................ 62.9 63.1 65.4 63.5 64.8 64.9
Idling or Stationary but activated...................... \1\ 47.8 44.8 46.0 \1\ 48.1
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Background.
Additionally, measurements were collected for vehicles approaching
at moderate constant speeds (20 mph, 30 mph, and 40 mph) in order to
document the convergence, if any, of HVs and ICE vehicles at higher
speeds. In general, HVs were quieter below approximately 20 mph, above
which either the vehicle's ICE engine turned on, tire and road noise
became dominant, or both. HVs also tended to have less high frequency
content than ICEs at low speeds. Further details and results from this
study can be found in NHTSA's final report DOT HS 811 304.\49\
---------------------------------------------------------------------------
\49\ See Docket for this notice, Item NHTSA-2011-0148-
0004.
---------------------------------------------------------------------------
Auditory Detectability of Vehicles in Critical Safety Scenarios \50\
---------------------------------------------------------------------------
\50\ See footnote 8; Garay-Vega et al., Auditory Detectability
of Hybrid Electric Vehicles by Pedestrians Who Are Blind. 90th
Annual Meeting Transportation Research Board January 23-27, (2011),
Washington, DC Available at http://amonline.trb.org/12ktc8/1.
---------------------------------------------------------------------------
In Phase 1, NHTSA compared the auditory detectability of HVs and
ICE vehicles by pedestrians who are legally blind. Forty-eight
independent travelers, with self-reported normal hearing, listened to
binaural \51\ audio recordings of two HVs and two ICE vehicles in three
operating conditions, and two different ambient sound levels. The
operating conditions included a vehicle: approaching at a constant
speed (6 mph); backing out at 5 mph; and slowing from 20 to 10 mph (as
if to turn right). The ambient sound levels were a quiet rural (31.2 dB
(A)) and a moderately noisy suburban ambient (49.8 dB (A)). Overall,
participants took longer to detect the two HVs tested
[[Page 2811]]
(operated in electric mode), except for the slowing maneuver. Vehicle
type, ambient level, and operating condition had a significant effect
on response time.
---------------------------------------------------------------------------
\51\ Binaural recordings reproduce the acoustic characteristics
of the sound similar to how a human perceives it. Binaural
recordings reproduce a more realistic three dimensional sensation
than conventional stereo and are intended for playback through
headphones, rather than loudspeakers.
---------------------------------------------------------------------------
Data collection included missed detection frequency and response
time (and corresponding time-to-vehicle arrival and detection
distance). Missed detection frequency is defined as instances when the
target vehicle is present and the participant fails to respond.
Response time is computed as the time from the start of a trial to the
instant the participant presses a space bar as an indication he/she
detects the target vehicle. Time-to-vehicle-arrival is the time from
first detection of a target vehicle to the instant the vehicle passes
the microphone line/pedestrian location. Detection distance is the
longitudinal space between the vehicle and the pedestrian (microphone)
location at the instant the participant indicated detection of a target
vehicle.
A repeated measure of analysis of variance (ANOVA) was used to
analyze the main and interaction effects of the independent variables:
vehicle type, vehicle maneuver and ambient sound level. A separate
analysis was completed for each scenario, and a pair-wise t-test
compared each vehicle with the other (ICE vehicle and HV twins) for
each ambient sound level. The time-to-vehicle arrival for each vehicle-
ambient condition is shown in Table 2, Table 3 and Table 4 for each of
three scenarios.
Vehicle Approaching at 6 mph (9.6 km/h) Pass by: The first
traveling situation examined was a pedestrian standing on the curb
waiting to cross a one-way street when there may be vehicles
approaching from the left. Some trials included a target vehicle and
some trials only included background noise. The target vehicle in this
scenario was traveling from the left at a constant speed of 6 mph.
There were vehicles in the background in all trials. The pedestrian had
to be able to detect a vehicle that would affect the decision about
when to start to cross the street. This scenario tested the distance
and time at which a pedestrian can detect a vehicle approaching at low
speed. On average, participants took 1.1 seconds longer to detect
vehicles in the high ambient sound condition than in the low ambient
sound condition. The main effect of ambient was statistically
significant. The mean time-to-vehicle-arrival was 5.5 and 4.3 seconds
for the low and high ambient condition respectively. Participants
detected both ICE vehicles sooner than the HV twins. The main effect of
vehicle type was statistically significant. The interaction effect of
vehicle type and ambient was also statistically significant, meaning
that the difference between when a passenger was able to detect an ICE
vehicle versus its HV twin was greater when ambient was high than when
it was low. Table 2 presents the individual differences between ICE
vehicles and their HV peers (i.e., Prius vs. Matrix and Highlander
hybrid vs. Highlander ICE); pair-wise comparisons are statistically
significant within a given ambient condition. Participants were more
likely to miss the Toyota HVs than the Toyota ICE vehicles approaching
at a constant low speed. The missed detection rates in the low ambient
condition were: 0.02 for the Prius; 0.01 for the Matrix; 0.03 for the
Highlander Hybrid; and 0.0 for the Highlander ICE vehicle. The
corresponding values in the high ambient condition were: 0.21 for the
Prius; 0.02 for the Matrix; 0.04 for the Highlander; and 0.01 for the
Highlander ICE vehicle.
Table 2--Time-to-Vehicle Arrival and Detection Distance for 6 mph Vehicle Pass-by by Vehicle Type and Ambient
Condition
----------------------------------------------------------------------------------------------------------------
Time-to-vehicle Detection
Vehicle Ambient sound level arrival (s) distance (ft)
----------------------------------------------------------------------------------------------------------------
2010 Toyota Prius....................... Low............................. 4.3 37.9
High............................ 2.4 20.9
2009 Toyota Matrix...................... Low............................. 5.5 48.4
High............................ 4.6 40.5
2009 Highlander Hybrid.................. Low............................. 5.3 46.6
High............................ 4.1 36.6
2008 Highlander ICE..................... Low............................. 6.8 59.4
High............................ 6.3 55.1
----------------------------------------------------------------------------------------------------------------
Vehicle Backing Out (5 mph (8 km/h) Reverse): The second traveling
situation was a pedestrian walking along a sidewalk with driveways on
the left side; the pedestrian heard distant vehicles in the background
in all trials. This is similar to walking in an area that is a few
blocks away from a main road. The target vehicle was a nearby vehicle
backing towards the pedestrian at a constant speed of 5 mph. This task
is complex for pedestrians since it is difficult to anticipate where
there may be a driveway and when a vehicle will move out of a driveway.
In addition, a driver's visibility may be limited and the pedestrian
may have very limited time to respond to avoid a conflict. The main
effect of ambient was statistically significant. The average time-to-
vehicle-arrival was 4.4 and 2.7 seconds for the low and high ambient
condition, respectively. Participants took longer to detect both HVs
than their ICE twins. The main effect of vehicle type was statistically
significant. Table 3 shows the individual differences between ICE
vehicles and their HV twins; pair-wise comparisons were statistically
significant within a given ambient condition. Participants were more
likely to miss the Toyota HVs than the Toyota ICE vehicles in the
backing out session. The missed detection rates in the low ambient
condition were: 0.05 for the Prius; 0.02 for the Matrix; 0.10 for the
Highlander Hybrid; and 0.02 for the Highlander ICE. The corresponding
values in the high ambient condition were: 0.11 for the Prius; 0.0 for
the Matrix; 0.26 for the Highlander; and 0.02 for the Highlander ICE.
On average, participants took longer to detect vehicles in the high
ambient sound condition than in the low ambient sound condition.
[[Page 2812]]
Table 3--Time-to-Vehicle Arrival and Detection Distance for Vehicle
Backing Out by Vehicle and Ambient Condition
------------------------------------------------------------------------
Time-to-vehicle
Vehicle Ambient sound level arrival(s)
------------------------------------------------------------------------
2010 Toyota Prius............... Low................ 4.0
High............... 2.5
2009 Toyota Matrix.............. Low................ 5.2
High............... 3.6
2009 Highlander Hybrid.......... Low................ 3.3
High............... 1.4
2008 Highlander ICE............. Low................ 5.2
High............... 3.3
------------------------------------------------------------------------
Vehicle Traveling in Parallel Lane and Slowing (Slowing from 20 to
10 mph (32 to 16 km/h): The third and last traveling situation examined
in the study was a pedestrian trying to decide when to start crossing a
street with the signal in his/her favor and a surge of parallel traffic
on the immediate left. The sound of slowing vehicles in the parallel
street helps blind pedestrians identify turning vehicles. In some
trials (no-signal condition), a vehicle continued straight through the
intersection at 20 mph, so pedestrians can cross whenever they choose.
However, in other trials there was a vehicle slowing from 20 mph to 10
mph as if to turn right into the pedestrian path (target vehicle). The
pedestrian had to be able to detect when the vehicle was slowing. This
scenario tests whether the pedestrian perceived this information when
the vehicle was in the parallel street. Participants were more likely
to miss the ICE vehicles approaching in the parallel lane and slowing
than the HVs in the same situation. Table 4 shows the time-to-vehicle
arrival and detection distance for the `vehicle slowing' scenario.
Pair-wise comparisons (HV vs. ICE twin) were statistically significant
within a given ambient condition. On average, participants detected HVs
sooner than their ICE vehicle twins. The main effect of vehicle type
was statistically significant. The trend observed in the vehicle-
slowing scenario (i.e., HVs are detected sooner than their ICE vehicle
twins) may be explained by a noticeable peak in the 5000 Hz one-third
octave band for the HVs tested during this operation. The tone emitted
was associated with the electronic components of the vehicles when
braking (e.g., regenerative braking). The missed detection rates in the
low ambient condition were: 0.05 for the Prius; 0.31 for the Matrix;
0.03 for the Highlander Hybrid; and 0.17 for the Highlander ICE
vehicle. The missed detection rates in the high ambient condition were:
0.05 for the Prius; 0.35 for the Matrix; 0.03 for the Highlander
Hybrid; and 0.17 for the Highlander ICE vehicle.
Table 4--Time-to-Vehicle Arrival and Detection Distance for Vehicle Decelerating From 20 to 10 mph by Vehicle
Type and Ambient Condition
----------------------------------------------------------------------------------------------------------------
Time-to-vehicle Detection
Vehicle Ambient sound level arrival(s) distance (ft)
----------------------------------------------------------------------------------------------------------------
2010 Toyota Prius....................... Low............................. 2.0 35.9
High............................ 1.9 33.8
2009 Toyota Matrix...................... Low............................. 1.1 18.0
High............................ 0.8 12.8
2009 Highlander Hybrid.................. Low............................. 3.0 58.8
High............................ 2.7 51.6
2008 Highlander ICE..................... Low............................. 1.5 25.7
High............................ 1.3 21.8
----------------------------------------------------------------------------------------------------------------
Table 5 shows the time-to-vehicle arrival by vehicle type, and
ambient condition. Considering all three independent variables, there
was a main effect of vehicle, vehicle maneuver, and ambient sound
level. Similarly, there were interaction effects between vehicle type
and ambient; vehicle type and maneuver, ambient and vehicle maneuver,
and a three way interaction between ambient, vehicle type and vehicle
maneuver.
Table 5--Average Time-to-Vehicle Arrival by Scenario, Vehicle Type and Ambient Sound
----------------------------------------------------------------------------------------------------------------
Low ambient High ambient
Scenario ---------------------------------------------------------------------------
HVs ICE Vehicles HVs ICE Vehicles
----------------------------------------------------------------------------------------------------------------
Approaching at 6 mph................ 4.8 6.2 3.3 5.5
Backing out (5 mph)................. 3.7 5.2 2.0 3.5
Slowing from 20 to 10 mph........... 2.5 1.3 2.3 1.1
----------------------------------------------------------------------------------------------------------------
[[Page 2813]]
B. NHTSA Phase 2 Research
In October 2011 NHTSA released a second report examining issues
involving hybrid and electric vehicles and blind pedestrian safety
titled ``Quieter Cars and the Safety of Blind Pedestrians, Phase 2:
Development of Potential Specifications for Vehicle Countermeasure
Sounds.'' The research conducted by Volpe first sought to define
acoustic specifications to be used as alert sounds for quiet vehicles
based on the sounds produced by ICE vehicles. Volpe then analyzed the
loudness of the ICE sounds in a suburban ambient using psychoacoustic
modeling. Volpe used human subject testing to evaluate the performance
of several different varieties of countermeasure sounds including ICE
sounds. Based on the results from the Phase I research, the
psychoacoustic modeling and the human subjects testing Volpe developed
potential specifications for vehicle countermeasure sounds.
The Phase 2 research developed various options and approaches to
specify vehicle sounds that could be used to provide information at
least equivalent to the cues provided by ICE vehicles, including speed
change. In this research, acoustic data acquired from a sample of 10
ICE vehicles was used to determine the sound levels at which synthetic
vehicle sounds, developed as countermeasures, could be set. ICE-
equivalent sounds were specified as overall A-weighted sound levels and
spectral content at the one-third octave band level. Psychoacoustic
models and human-subject testing were used to explore issues of
detectability, masking, and recognition of ICE-like and alternative
sound countermeasures.
The researchers determined that the elements of a specification for
vehicle sounds should consider sound output levels; pitch changes that
convey changes in vehicle speed; and acoustic qualities that determine
whether the sound is perceived as a vehicle. The options discussed in
the Phase 2 final report \52\ assume that the vehicle acoustic
countermeasure should:
---------------------------------------------------------------------------
\52\ See footnote 11.
---------------------------------------------------------------------------
Provide information at least equivalent to that provided
by ICE vehicles, including speed change; and
Provide for detection of a vehicle in residential,
commercial and other suburban and urban environments. Note: Human-
subject tests for Phase 2 were conducted in an ambient level of
approximately 58-61 dB (A).
Phase 2 work focused initially on the following two ideas: (1) the
lack of detectability of quieter vehicles can be remediated if they are
fitted with synthetic sound generators that emulate the sound of
typical ICEs; and (2) the specifications for the vehicle sounds can be
defined in terms of objective parameters--namely, overall sound output
as measured by the SAE J2889-1 procedure and spectral distribution
specifications for the minimum amount of sound level in one-third-
octave bands.
Recognizability is more complex than detectability. Most sounds,
and sounds as complex as those emitted by an ICE, have numerous
properties in addition to loudness and spectral distribution that
affect human perception. Among these properties are rise time, decay
time, repetition rates, variations in pitch and loudness, and phase
relations among various components of the sound. These challenges can
be demonstrated, for example, by playing a recording of a sound
backwards, for example, that changes in these properties can render a
sound unrecognizable even though loudness and spectral distribution are
unchanged. There are no established quantitative metrics for many
qualities of a sound that a person might use for recognition.
In the Phase 2 report Volpe first considered whether HVs and EVs
should be equipped with sounds that are based on the acoustic profile
of ICE vehicles. This concept is based on the assumption that the ICE
vehicles measured in this study are typical of the current fleet, emit
an acceptable amount of noise during low-speed operations, and that
some (e.g., ICE-like) countermeasure sounds can be based on the
statistical average of real-vehicle spectral characteristics.
Researchers developed the potential specifications for alert sounds
shown in Table 6 and Table 7 based on acoustic analysis of sounds
produced by ICE vehicles to demonstrate what acoustic specifications
for a vehicle alert sound might look like. The derivations of these
data are given in Section 5 of the Phase 2 final report.
Table 6--Minimum Overall A-weighted Level (LAeq, 1/2; sec) by Vehicle
Operation
------------------------------------------------------------------------
LAeq, 1/2 sec,
Vehicle operation dB(A)
------------------------------------------------------------------------
6 mph................................................... 61.1
10 mph.................................................. 63.6
15 mph.................................................. 68.1
20 mph.................................................. 70.2
Acceleration............................................ 66.7
Start-up................................................ 70.7
Stationary but activated................................ 55.2
------------------------------------------------------------------------
Table 7 shows the corresponding minimum A-weighted one-third-
octave-band spectra for each operating mode. ICE vehicles have energy
components in all frequencies (e.g., 100 to 20k Hz), however, the
psychoacoustic models implemented in this study show that energy
components in the one-third octave bands ranging from 1600 Hz to 5000
Hz contributed the most to detection, and those ranging from 315 Hz to
1600 Hz contributed additional detection and pitch information. These
spectral distribution limits are derived from the procedures described
in Section 6 of the Phase 2 final report.
Table 7--A-weighted One-Third-Octave-Band Spectra at Microphone Line LAeq, 1/2 sec
--------------------------------------------------------------------------------------------------------------------------------------------------------
Stationary but
1/3 Octave band center frequency, Hz 6 mph 10 mph 15 mph 20 mph Acceleration Startup activated
--------------------------------------------------------------------------------------------------------------------------------------------------------
100 to 20000............................ 61.1 63.6 68.1 70.2 66.7 70.7 55.2
315..................................... 43.9 46.9 50.2 52.5 49.8 44.2 37.3
400..................................... 46.5 48.7 53.0 54.1 51.4 46.6 39.0
500..................................... 47.9 51.2 55.6 57.1 53.4 51.8 42.1
630..................................... 49.0 52.5 56.9 59.1 54.6 52.4 42.3
800..................................... 51.1 54.6 59.5 62.3 55.1 55.2 43.2
1000.................................... 51.4 55.2 60.2 63.2 55.6 57.8 44.9
1250.................................... 52.2 54.6 59.6 62.2 57.2 60.5 46.3
1600.................................... 52.0 54.3 58.8 61.3 57.0 61.1 45.4
[[Page 2814]]
2000.................................... 50.3 52.0 56.1 57.9 55.7 60.5 44.6
2500.................................... 49.1 50.3 53.9 54.9 55.1 61.1 43.8
3150.................................... 48.6 49.2 52.4 52.1 54.9 61.6 44.1
4000.................................... 46.9 47.5 50.5 49.5 53.2 60.9 42.4
5000.................................... 44.1 45.0 47.8 46.4 50.8 59.2 40.3
--------------------------------------------------------------------------------------------------------------------------------------------------------
The Volpe Center examined two options \53\ under this first concept
(ICE-like sounds):
---------------------------------------------------------------------------
\53\ In this section of the notice the word ``option'' refers to
countermeasure concepts developed in Phase 2 research and not
rulemaking options considered by the agency when developing this
proposal (see Sections VII and VIII for NHTSA's proposal and
alternatives considered, respectively).
---------------------------------------------------------------------------
Recordings of Actual ICE Sounds
The first option under the ICE-like sound concept explored using
recordings of actual ICE vehicles as alert sounds. Recordings would be
made when the vehicle is operating at constant speeds, forward from 0
to 20 mph and in reverse at 6 mph. Other components of the vehicles
noise output (e.g., tire noise, aerodynamic noise, AC fan noise) would
be emitted regardless of whether an ICE is in use and would not be
included in these recordings. Sound generation systems with signal
processing capabilities would be used to continuously and monotonically
vary the sounds from one operating condition to the next according to
vehicle input (e.g. vehicle speed sensors, throttle sensors, etc.). In
this option, emitted sounds would be based on standardized recordings
with processing limited to pitch shifting in proportion to vehicle
speed and interpolation between sounds.
Synthesized ICE-Equivalent Sounds
The second option under the ICE-like sound concept explored using
simulated ICE sounds directly synthesized by a digital-signal processor
(DSP) programmed to create ICE-like sounds (based on actual target
sounds) that would vary pitch and loudness depending on vehicle inputs.
This is in contrast to the first option, described above, in which the
sounds come directly from recordings of actual vehicles, and the
processor must store and interpolate among files representing every
mode of operation and for every speed within the 0 to 20-mph range.
Here, the resulting synthesized sounds would resemble those of the
first option, but have fewer spectral components. A synthesizer could
be simpler and cheaper than a sound generator based on real ICE sounds.
For this option, target sounds, recorded from actual vehicles for the
operations specified above would be used. The synthesized sounds would
then be developed to match the spectral shape of these target sounds.
(Note: by definition, power-spectra spectral lines have a resolution of
1 Hz).
Sound generation systems with signal processing capabilities would
be used to continuously and monotonically vary the sounds from one
operating condition to the next according to vehicle input (e.g.
vehicle speed sensors, throttle sensors, etc.) and the synthesis
algorithms developed for their sounds. The two options listed above
assume that band-limited (315 Hz to 5000 Hz) ICE-like sounds will be
recognizable as motor vehicles.
Alternative, Non-ICE-Like Sounds Designed for Detectability
The second concept, described in the Phase 2 final report, consists
of alternative countermeasure sounds with acoustic characteristics
different from ICE vehicles. Some of the countermeasures evaluated in
the human-subject studies have sound characteristics that could improve
detectability when compared to ICE-equivalent sounds. The following
sound characteristics can improve detectability of a sound source \54\:
---------------------------------------------------------------------------
\54\ Stanton & Edworthy (Eds.) (1999) Human Factors in Auditory
Warnings
---------------------------------------------------------------------------
Pulsating quality with pulse widths of 100 to 200 msec.
Inter-pulse intervals of about 150 msec.
Fundamental tonal component in 150 to 1000 Hz range.
At least three prominent harmonics in the 1 to 4 kHz
range.
Pitch shifting denoting vehicle speed change.
The design of a non-ICE sound involves a complex tradeoff among
several factors including annoyance, cost, detectability, and overall
sound pressure level values. While the required sound pressure level
values for non-ICE-like sounds will generally be lower than for ICE-
like sounds for the same detection distance, there is no objective
basis upon which to calculate the difference in sound pressure level
values for the class of non-ICE sounds as a whole. Rather, the
equivalent detectability sound pressure level value for a particular
non-ICE sound must initially be determined experimentally by a jury
process that rates detectability. As psychoacoustic models improve, it
may be possible to use them in place of jury testing to determine
minimum sound pressure level specifications for these sounds, but that
approach is not yet sufficiently accurate.
In this concept sound generation systems with signal processing
capabilities would be used to continuously and monotonically vary the
pitch and amplitude of sounds as appropriate to operating conditions
according to vehicle inputs (e.g. vehicle speed sensors, throttle
sensors, etc.). The appropriate relationship between sound amplitude
and throttle position would need to be determined. The detectability of
a specific non-ICE sound can be best determined only through human
subjects testing, at the present state of the art.
Hybrid of Options Discussed Above
A third concept to designing countermeasure sounds, explored in the
Phase II report, would be a combination of the concepts (i.e. using
ICE-like or non-ICE-like sounds) discussed above, with the goal of
gaining the benefits of each, while minimizing the disadvantages.
Simulated ICE sound could be generated which would vary pitch and
loudness depending on vehicle inputs. This system could simultaneously
generate both ICE-like sounds at a lower sound pressure level than the
concepts based on ICE sounds discussed above, and synthetic sounds
designed for optimal alerting potential with minimal annoyance. The
ICE-like sound components may not be heard in higher urban ambient-
noise conditions, but their association with the alerting sound would
be learned over time from when the pedestrian is exposed to the sound
in lower ambients. This method would most likely depend on jury testing
of human subjects to set the sound level for detection.
[[Page 2815]]
Human Subject Evaluation of Detectability
A human subject study was conducted to compare the auditory
detectability of potential sounds for hybrid and electric vehicles
operating at a low speed. The sounds evaluated included: (1) Sounds
produced by vehicles with integrated sound systems rented from
manufacturers, and (2) sounds produced by prototype systems rented from
manufacturers, and played back by loudspeakers temporarily mounted on
HVs rented separately. Five vendors, motor vehicle manufacturers or
suppliers of automotive electronics, provided prototypes of synthetic
sound generators for EVs or HVs. The five systems were labeled ``A'' to
``E''. A total of nine sounds were evaluated: A1, A2, A5, B, C, D, E1,
E3, and E4. Sounds were evaluated at two sound pressure levels typical
of ICE vehicles at low speeds (i.e., A-weighted SPL of 59.5 dB and 63.5
dB).\55\ An ICE vehicle that produced A-weighted SPL of 60 dB in the 6
mph pass-by test was used as a reference in this evaluation. The ICE
vehicle was labeled `R'.
---------------------------------------------------------------------------
\55\ As measured by the SAE J-2889 draft test procedure (SAE J-
2889, draft, 2009).
---------------------------------------------------------------------------
Sound A1 was an engine like sound with a turbine-like whine that
had a prominent peek that varied from 150 Hz to 300 Hz based on vehicle
speed. Sound A2 was an engine sound with enhanced valve noise with
prominent signal content between 100 Hz and 200 Hz. Sound A5 was a
whirring sound with a diesel engine sound. The fundamental signal
content of the whirring part of the sound for sound A5 was between 400
Hz and 600 Hz based on vehicle speed. Sound B emulated the exhaust note
(the fundamental of the combustion noise) of an engine. The sound did
not contain appreciable components above 250 Hz. Sound C was a Wavy,
turbo-like sound with most of its energy as broadband noise in the 200
Hz to 5000 Hz range. Sound D was a broadband sound designed to suggest
an electric motor coupled to other rotating machinery. Sound E1 was a
pure engine noise with most of its energy below 300 Hz. Sound E3 was an
engine-like sound with a `whirring' character and a flatter spectral
distribution than Sound E1 and had none of the prominent harmonics of
the combustion note. Sound E4 contained short bursts of predominantly
high-frequency sound with the peak amplitude of the fundamental varying
in frequency from about 450 Hz to 700 Hz based on speed.
Data was collected outdoors during three independent sessions
conducted on three days in July and August 2010. The first session
included four operating modes: idle (stationary), acceleration from
stop, start-up and 6 mph forward pass-by. The following two sessions
included the 6 mph forward pass-by. The HVs used in the study were
operated in electric mode during the pass-by trials. The sample
included 79 participants 34 of which were sighted and 45 of which were
legally blind. The legally blind participants were independent
travelers and all participates had self-reported normal hearing.
The study took place in a parking lot located on the USDOT/Volpe
Center campus in Cambridge, Massachusetts. The test site has the
acoustic characteristic of an urban area with a typical ambient noise
of approximately A-weighted sound pressure level of 58-61 dB. The
dependent variables examined in the study included raw detection
distance, proportion of detection, time-to-vehicle arrival, and
detection distance. Raw detection distance is the number of feet the
vehicle was from the participant when the participant indicated she or
he heard the sound. A failure to detect the sound before the vehicle
passed was treated as missing data. Proportion of detection is the
proportion of trials of a given condition in which the participant
detected the sound anytime before the vehicle passed the participant.
Time-to-vehicle-arrival is the time, in seconds, from detection of a
target vehicle sound to the instant the vehicle passes the pedestrian
location. Detection distance is the calculated distance, feet, to the
target vehicle at the moment each subject responded.
Each subject had a push button device which they used to indicate
when they detected a nearby vehicle. Participants were asked to press a
response button when they detected and recognized a vehicle that would
affect their decision about when to start crossing the street.
Table 8 shows the mean detection distances for the sounds evaluated
in the human-subject studies for the 6 mph pass-by; sounds at the top
of the list can be described as sounds designed according to
psychoacoustic principles and sounds at the end of the list can be
described as ICE-like sounds with only the fundamental combustion noise
or otherwise lacking in the qualities that support detectability. The
results show that high amplitude sounds (A-weighted SPL of 63.5 dB)
were detected more often and at greater distances than low amplitude
sounds (A-weighted SPL of 59.5 dB).
Table 8--Mean Detection Distance (ft) for All Sounds at Two Amplitudes
and for the Reference ICE Vehicle
------------------------------------------------------------------------
Average Average
detection detection
distance distance
Sound number (feet) for (feet) for
amplitude amplitude
equal 59.5 equal 63.5
dB(A) dB(A)
------------------------------------------------------------------------
E4...................................... 72 85
A2...................................... 57 77
E3...................................... 52 70
A5...................................... 50 47
ICE vehicle, 60 dB(A)................... 41 NA
A1...................................... 35 44
C....................................... 32 41
E1...................................... 30 32
B....................................... 20 25
D....................................... 19 NA
------------------------------------------------------------------------
[[Page 2816]]
Results show that A2, A5, E3, and E4 have significantly better
detectability than the ICE reference sound at 6 mph. These sounds never
have significantly worse detectability in any condition. Thus, these
sounds overall have better detectability than the ICE reference sound.
In contrast, sounds A1, B, C, D, and E1 all have significantly worse
detectability than the reference sound for the 6 mph forward pass-by.
These sounds never have significantly better detectability in any of
the conditions presented to subjects. Thus, these sounds overall have
worse detectability than the reference sound.
The analysis also indicated significant main effects of sound and a
significant three-way interaction of session, sound, and direction.
This implies that the relative performance of each sound, including the
reference sound, is jointly contingent on the direction it comes from
and the session it was presented in. The directional effect results
primarily from the fact that the roof-top fans on buildings to the west
were the predominant source of ambient noise, which can mask vehicles
approaching from the west compared with vehicles approaching from the
east. The detectability of each sound relative to the reference was
evaluated by comparing each sound to the reference vehicle for the
corresponding session and direction condition of each.
To compare the detectability of the sounds to each other, a mixed
design ANOVA was performed on detectability with session and vision as
between-subjects independent variables, and sound, direction, and
amplitude as within-subject independent variables.\56\ Sounds were
ranked by comparing each to the other (t-tests) for each session by-
direction-by-amplitude condition. To assist in the control for family-
wise error rate, the analyses only included the four sounds shown to be
superior to the reference sound. Results show that E4 has overall
significantly better detectability than the other sounds, and within
each condition it is never worse than any other sound, except for one
condition when compared to A2. Sounds A2 and E3 are overall not
significantly different than each other, showing only a difference in a
single condition. Sound A5 has overall significantly worse
detectability than the other sounds, and within each condition is it
never better, except for one condition when compared to E3. The overall
ranking of the sounds from most to least detectable is therefore: E4,
A2 and E3, and A5.\57\
---------------------------------------------------------------------------
\56\ The reference sound `R' and sound `D' were excluded from
this analysis since they did not differ in amplitude.
\57\ The acoustic characteristics of these sounds are discussed
in Section 5.2 of NHTSA Report No. DOT HS 811 496.
---------------------------------------------------------------------------
In summary, the human subject testing in Phase 2 suggest that
synthetic sounds that resemble those of an ICE produce similar
detection distances as actual ICE vehicles. In some instances,
synthetic sounds designed according to psychoacoustic principles can
produce double the detection distances relative to the reference
vehicle. The results also suggest that synthetic sounds that contain
only the fundamental combustion noise are relatively ineffective. None
of the analyses found a significant effect of vision ability.\58\
Participants who are legally blind, on average, were no better or worse
than sighted participants in detecting the approach sounds.
---------------------------------------------------------------------------
\58\ All participants were required to wear a blindfold during
the study.
---------------------------------------------------------------------------
C. NHTSA Phase 3 Research
The third phase of NHTSA's research involving quiet vehicles
consisted of developing an objective, repeatable test procedure and
objective specifications for minimum sound requirements for hybrid and
electric vehicles. NHTSA's Vehicle Research and Test Center (VRTC)
conducted acoustic measurements and recordings of several HVs and EVs
and those vehicle's ICE pair vehicles. Volpe used these recordings as
well as data from the Phase 1 and Phase 2 research to identify
parameters and criteria for sounds to be detectable and recognizable as
a motor vehicle.
VRTC Acoustic Measurements
The primary focus of Phase 3 research conducted by VRTC was to
evaluate the new SAE J2889-1 test method and several variations used to
test operating conditions that were not included in SAE J2889-1 and
provide data to establish performance criteria. The research was
conducted using 3 HVs, 1 EV, and 4 ICE vehicles.
SAE J2889-1 was still in draft form at the start of the project,
but the final version published in September of 2011 was not
significantly different from the draft. The vehicles were used to
gather sample data on the difference in sound pressure levels between
ICE sounds and EV or HV sounds as well as directivity and sound quality
levels using eleven test scenarios developed for this program (4 static
and 7 pass-by). Some of the hybrid and electric vehicles were tested
with multiple alert sounds. Some the hybrid and electric vehicles were
also tested with no alert sound at all to determine crossover levels.
A significant modification to the SAE procedure was the addition of
a laser at the microphone line-labeled as PP' in SAE J2889-1. This
addition enabled recording the time at which the leading edge of the
vehicle reached the microphone location.
Test Scenarios \59\
---------------------------------------------------------------------------
\59\ Diagrams showing the microphone setup for all the scenarios
are contained in the Phase 3 report from VRTC.
---------------------------------------------------------------------------
VRTC measured the vehicle sound output for the operating scenarios
listed below for ICE vehicles, hybrid and electric vehicles with an
alert sound active, and hybrid and electric vehicles with no alert
sound active. The overall goal of the research was to capture as much
acoustic data as possible for both ICE sounds and artificial sounds
added to hybrid and electric vehicles as alert sounds so that the
sounds could be analyzed when the agency was the establishing acoustic
specifications contained in this proposal.
Scenario 1: SAE J2889-1 modified Startup (8 microphones).
This set up was used to generate a 360 degree sound or directivity
profile for the vehicle.
Scenario 2: SAE J2889-1 modified Stationary but active (8
microphones). This scenario was the same as Scenario 1 except that the
sound of the vehicle while stationary was recorded.
Scenario 3: SAE J2889-1 modified Startup (5 microphones).
Data from this recording can be used can be used to generate a 180
degree sound or directivity profile for the vehicle.
Scenario 4: SAE J2889-1 modified Stationary but active (5
microphones). This scenario was the same as Scenario 3 except that the
sound of the vehicle while stationary was recorded.
Scenario 5: SAE J2889-1 10 km/h Forward Constant Speed (2
microphones). This test produced result from 2 microphones on either
side of the vehicle centerline.
Scenario 6: SAE J2889-1 20 km/h Forward Constant Speed (2
microphones). This test produced result from 2 microphones on either
side of the vehicle centerline.
Scenario 7: SAE J2889-1 30 km/h Forward Constant Speed (2
microphones). This test produced result from 2 microphones on either
side of the vehicle centerline.
Scenario 8: SAE J2889-1 10 km/h Reverse Constant Speed (2
microphones). This test was pass-by noise test with data being recorded
as the vehicle is driven backwards though the noise test pad with two
[[Page 2817]]
microphones on either side of the vehicle centerline.
Scenario 9: 0 to 10 km/h Forward Acceleration to Constant
Speed (2 microphones) The vehicle was positioned 2 meters before the
PP' line and accelerated at 0.1 g from 0 to 10 km/h pass-by noise test
with data being recorded by two microphones on either side of the
vehicle centerline as the vehicle is accelerated though the remainder
of the noise test pad.
Scenario 10: 30 to 10 km/h Forward Deceleration to
Constant Speed (2 microphones). The vehicle was driven at 30 km/h into
the test zone and began deceleration at 0.1 g to 10 km/h at the PP'
line.
Scenario 11: 0 to 10 km/h Reverse Acceleration to Constant
Speed (2 microphones). The vehicle was positioned 2 meters before the
PP' line and accelerated from 0 to 10 km/h with data being recorded by
microphones on both sides of the vehicle centerline as the vehicle was
accelerated though the remainder of the noise test pad.
When testing the vehicle in the scenarios described above VRTC
identified some challenges. The test drivers found that it was
difficult to reliably maintain a low travel speed for some vehicles
during the 10 km/hr forward pass-by test as these vehicles tried to
shift gears or the electric controls energized or de-energized. During
the pass-by tests conducted in reverse at 10 km/hr the test drivers
experienced some of the same difficulties experienced during the
forward pass-by testing. Also, it was very difficult to maintain the
vehicle in the center of the lane. Testing in reverse could only be
done during daylight hours due to difficulty in driving backwards,
drifting in the lane and possible equipment damage. During the testing
of the vehicle accelerating from 0 to 10 km/hr the test drivers
encountered difficulty in maintaining a consistent acceleration rate.
Positioning the vehicle for this test and starting the data acquisition
was very labor intensive
When testing the vehicle decelerating from 30 to 10 km/hr the test
drivers encountered difficulty in maintaining a consistent deceleration
rate. Determining the starting point of deceleration was difficult.
Some vehicle braking rates were difficult to maintain the 0.1 g rate.
During braking the vehicles' regenerative braking systems transitioned
back and forth from mechanical to regenerative braking. When testing
the vehicles while accelerating in reverse the test drivers encountered
difficulty in maintaining a consistent acceleration rate and
maintaining the center of the lane for the remainder of the test pad.
Positioning the vehicle and starting the data acquisition was very
labor intensive for this test.
Interpretation of Results
One of the purposes of the Phase 3 acoustic measurements was to
gather additional data on the difference in sound levels between EVs
and HVs operating in electric mode and ICE vehicles. For the pass-by
tests in Phase 3 the ICE vehicles were 6.2 to 8.5 A-weighted dB louder
than the EV/HVs without added sound at 10 km/h. At 20 km/h the
difference between the HV/HVs and ICE vehicles varied, but the average
level was 3.5 A-weighted dB louder for the ICE vehicles. At 30 km/h the
sound levels of the HV/HVs approached the levels of the ICE vehicles
and the individual measurements for the two types of vehicles have
considerable overlap. Table 9 shows the results of HEV/EV vehicles with
no sound alert system as compared to their ICE counterpart.
Table 9--Pass-By Sound Level for HEV/EV Vehicles Without Alert Sound Active Versus Counterpart ICE Vehicles
----------------------------------------------------------------------------------------------------------------
HEV/EV Sound ICE Sound ICE minus HEV/
Manufacturer Speed, km/h level, dB level, dB EV, dB
----------------------------------------------------------------------------------------------------------------
Nissan.......................................... 10 50.5 56.6 6.2
20 60.0 62.3 2.2
30 66.5 68.1 1.5
Prototype Vehicle G............................. 10 51.4 59.9 8.5
20 60.5 63.1 0.6
30 67.0 67.5 0.5
Prototype Vehicle H............................. 10 51.2 59.7 8.5
20 59.3 64.5 5.2
30 65.3 69.2 3.9
Average......................................... 10 51.0 58.7 7.7
20 59.9 63.3 3.5
30 66.3 68.3 2.0
----------------------------------------------------------------------------------------------------------------
The measurements from the startup and stationary but active
scenarios were used to measure the directivity of the vehicles' sound.
The purpose of measuring the directivity pattern of the vehicles was to
compare the directivity pattern of ICE vehicles to those hybrid and
electric vehicles equipped with a speaker system. For the ICE vehicles
the sound pressure level behind the vehicle was from 6 to 10 dB less
than that directly in front of the vehicle. For the vehicles with an
speaker system the sound level behind the vehicle was 12 to 15 dB lower
behind the vehicle, and in some cases the sound level at the microphone
behind the vehicle was not distinguishable from a quiet background
sound level of 40 dB. There was a systematic difference from left to
right for some vehicles, particularly with an artificial sound.
Acoustic Analysis Performed by Volpe
As part of the Phase 3 research Volpe examined the frequency range,
minimum sound level for selected one-third octave bands, and
requirements for broadband noise and tones as possible criteria for
vehicle sound using a loudness model to determine when the sounds might
be detectable in a given ambient. Also considered were the relative
proportions of acoustical energy emitted from a vehicle as a function
of direction (directivity) and ways to denote changes in vehicle speed.
Two approaches were used to identify potential detectability
specifications for alert sounds to be included in the NPRM: (a) sound
parameters based on a loudness model and detection distances and (b)
sound parameters based on the sound of ICE vehicles.
[[Page 2818]]
Volpe's work in developing the acoustic specifications based on a
loudness model and detection distances was guided by several aspects of
the agency's Phase 1 and Phase 2 research. Volpe analyzed the acoustic
data of the sounds used in the human factors research in Phase 2 from a
psychoacoustic perspective to determine the loudness of the sounds and
whether the sounds would be detectable in several different ambient
environments. Of the several different loudness models examined by
Volpe, Moore's Loudness provided the most pertinent information about
the perceived loudness and detectability of a sound.
Because the response of the study participants in the human subject
experimentation in Phase 2 varied significantly due to variations in
the ambient, Volpe determined that any analysis of sounds using a
loudness model should use a synthetic ambient that did not vary with
respect to the frequency profile or overall sound pressure level. Volpe
used a synthetic ambient sound with the loudness model during Phase 3
in developing the specifications contained in this proposal. Volpe also
observed during the human factors research that sounds with strong
tonal components were more detectable.
Volpe developed the specifications based on the sound of ICE
vehicles using measurements of ICE vehicles captured in Phase 2 and
acoustic data provided by representatives of auto manufacturers.
Before presenting these two approaches, it is important to explain
how background noise, critical frequency range, and loudness models
relate to the detectability of a sound.
Background Noise
When talking about the detectability of a sound, it is important to
understand masking and background noise (ambient noise). Masking occurs
when the perception of one sound is affected by the presence of an
unrelated sound. Background noise can affect the extent to which
masking occurs. Two characteristics of background sounds are of primary
importance: overall sound pressure level and the frequency content or
shape of the frequency spectrum. Masking depends on the signal-to-noise
ratio in the different frequency bands and therefore cannot be
estimated from the overall A-weighted sound level alone. Acoustic data
for background noise can be obtained from recordings of background
noise made at various locations. Recordings of actual traffic may
include peaks (e.g., passage of nearby loud vehicles) that can
introduce variability when using human subjects for testing or when
applying detectability models. An alternative to recordings of the
actual traffic is to use standardized synthetic background noise.
Synthetic background noise consists of, for example, white noise
filtered to have the same spectrum as what a pedestrian would hear in
real traffic but without the variations in amplitude over time (e.g.,
those caused by the passage of a particular loud vehicle or aircraft).
This broadband noise creates masking while reducing the issues
associated with fluctuations or peaks. The standardized noise is an
advantage for repeatability. For more information about this, see
Pedersen et al. 2011.\60\
---------------------------------------------------------------------------
\60\ Pedersen et al. (2011). White paper on external sounds for
electric cars--Recommendations and guidelines. Delta-Senselab.
Copenhagen.
---------------------------------------------------------------------------
A standardized background noise was used in Phase 3 in the
implementation of Moore's Loudness model to compute minimum sound
levels for detection in a given one-third octave band and to identify
frequency ranges relevant for alert sounds.\61\ The ambient selected
for these analyses is representative of many common urban ambients.\62\
Being detectable in this ambient would mean that the alert sound would
be detectable in other ambients with lower overall levels and similar
spectral shapes. The spectral shape is given in Figure 2. The overall
A-weighted level for detection computations was 55 dB). Results for 60
A-weighted dB can be accurately estimated by adding 5 dB to the results
from the 55 A-weighted dB analysis. Similarly, results for 50 A-
weighted dB can be accurately estimated by subtracting 5 dB from the
results from the 55 A-weighted dB analysis.
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\61\ For a discussion of loudness models see page 67.
\62\ See footnote 59.
[GRAPHIC] [TIFF OMITTED] TP14JA13.030
Critical Frequency Range
Critical frequency regions, defined by a set of one-third octave
bands, are determined by applying psychoacoustic principles for a given
ambient condition. The purpose of identifying a critical frequency
region(s) is to ensure that a sound signal is emitted from the vehicle
such that it would be expected to be detectable at a reasonable
distance away from a pedestrian. Due to masking effects of the ambient
and potential hearing loss of the pedestrian, opportunities for
detection will be maximized if the alert signal contains detectable
components over a wide frequency range.
Frequencies in the audible range for children and most young adults
are from about 20 to 20,000 Hz. Human
[[Page 2819]]
hearing is more sensitive in the 500-5,000 Hz range than it is at low
frequencies or very high frequencies.\63\ Exposure to loud noise and
age-related factors often diminish a person's sensitivity to sound at
higher frequencies. Mid-range frequencies (approximately 320--5120 Hz)
are perceived with greater loudness than lower (20 to 320 Hz) or higher
frequencies (5000 to 20,000 Hz). Frequencies below 300 Hz are commonly
masked by urban background noise.\64\
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\63\ Fletcher, H. and Munson, W. A. (1933). Loudness, its
definition, measurement, and calculation. Journal of the Acoustic
Society of America. 5 (1), 82-108.
\64\ See footnote 11 Chapter 6.
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Localization of sounds is accomplished through multiple
neurophysiological processes, each of which is most effective in a
different range of frequencies. Above 1600 Hz, inter-aural level
differences (caused by the shadowing effect of the head) become the
primary directional cues. For some combinations of frequency and
angular orientation between sound source and listener, cancellation of
the direction cues can occur. Hence, an accurate localization of a
sound source is most likely to occur when it contains multiple high-
frequency components that are audible above the background noise.\65
66\
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\65\ Feddersen et al. (1957). Localization of high frequency
tones. Journal of the Acoustical Society of America. 5, 82-108.
\66\ Yost, W.A. (1994) Fundamentals of Hearing: An Introduction.
San Diego: Academic Press.
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A person's relative sensitivity to different frequencies varies
with loudness. Loudness is a numerical designation of the strength,
expressed in units called ``sones,'' of a sound that is proportional to
the subjective magnitude as estimated by listeners having normal
hearing (ANSI S3.4 2007).\67\ Loudness models predict this strength by
accounting for how the human auditory system processes both the
amplitude and frequency characteristics of a sound.
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\67\ American National Standard (1995). Procedure for the
computation of loudness of steady sound (ANSI S1.13). New York, New
York: Secretariat, Acoustical Society of America.
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Loudness Models
Sound-pressure-level-based metrics, such as, the A-weighted level,
provide a first estimate of the perceived loudness of a sound. These
metrics fail to account for several factors that affect the perceived
loudness including: the level dependence of the frequency sensitivity,
level dependence on frequency selectivity, and frequency based masking
effects. The level dependence of the frequency sensitivity refers to
the fact that for the same change in sound pressure level for a low
frequency sound and a high frequency sound, the low frequency sound
will be perceived as increasing in loudness more than the high
frequency sound. The level dependence of the frequency selectivity
refers to how the human auditory system separates frequency components
of a complex sound's signal. Frequency-based masking is used to
describe how a high-energy component can prevent or reduce the
perception of a lower-energy component at a different frequency. That
is, for example, an ambient with a high level of low-frequency sound
can mask a signal with components in a higher frequency range.
Several psychoacoustic models exist that relate sound pressure
level data to the perceived loudness of the signal or its
detectability/audibility. Moore's Loudness model \68 69\ was used in
Phase 3 to estimate the minimum sound level needed for a sound to be
detectable in the presence of an ambient. This model is useful for the
prediction of thresholds in quiet ambients and for thresholds in the
presence of a masker,\70\ as well as for computing equal loudness
contours.\71\ This model was developed for use with ISO 226, Normal
Equal-Loudness Contours, (1987) and the absolute thresholds found in
ISO 389-7, Acoustics--Reference zero for the calibration of audiometric
equipment--Part 7: Reference threshold of hearing under free-field and
diffuse-field listening conditions, (1996). Since the model's original
development, both of these standards have been updated to ISO 226
(2003) and ISO 389-7 (2005). There are newer implementations of Moore's
model that reflect these new data. However, we are not aware of any
implementations that include these updates as well as provide for
computing thresholds in the presence of a masker. Since computing
thresholds in the presence of a masker is of fundamental importance for
the work in Phase 3, and since the updates represent ``fine tuning'' of
the model, the 1997 model was identified as the most suitable choice.
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\68\ Moore et al. (1997). A model for the prediction of
thresholds, loudness, and partial loudness, J. Audio Eng. Soc.
45(5).
\69\ Moore and Glasberg (1997). A model of loudness perception
applied to cochlear hearing loss. Auditory Neuroscience, 3, 289-311.
\70\ A value of 0 sones is approximately the threshold of
perception. Moore models threshold to be at 0.003 sones to match ISO
389-7:2005 to within 0.2 dB over the frequency range from 50 to
12,500 Hz (ANSI S3.4-2007).
\71\ Loudness contours is a graphical representation of
frequency (x-axis) versus levels (y-axis) such that tones of
different frequency and different level are judged to be equally
loud.
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Moore's Loudness model, as described in Moore and Glasberg
(1997),\72\ accounts for the following factors: how the sound is
presented to the subject (free field, diffuse field, via headphones);
transmission through the pinna (outer ear) and the middle ear;
frequency sensitivity and selectivity; excitation compression/
amplification; the transformation of pressure entering the cochlea to
an excitation pattern (determined from the magnitude of auditory filter
output); transformation from an excitation pattern to specific loudness
for sounds in quiet ambient environments and in the presence of a
masker (specific loudness is analog to power spectral density); and
integration of specific loudness (integrating the area under the curve
of a power spectral density function gives the total power of that
function).
---------------------------------------------------------------------------
\72\ See footnote 67, 289-311.
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The general procedure for running the model is to provide un-
weighted one-third octave band levels for both the signal and the
masker and to provide information on how the signal is presented. For
the purposes of the Phase 3 work, free-field, frontal presentation was
used, which is both accurately and conservatively compared to diffuse
field or headphones. The model provides several levels of detail in the
results, including the specific loudness as a function of the number of
equivalent rectangular bandwidths. It is the integral of this function,
or simply Loudness in sones that was utilized in Phase 3.
This model was adequate for the needs of Phase 3. However, since
this is a time-invariant model, it does not take into account
differences in duration (sounds with very short durations are perceived
differently than long duration sounds due to the temporal windows
associated with the auditory system). Nor does it account for periodic
modulations including the effect of co-modulation masking release.
As part of the Phase 3 research, in addition to exploring the
detectability of sounds, the agency examined acoustic characteristics
that make sounds recognizable. Recognition includes two aspects: 1)
recognition that the sound is emanating from a motor vehicle, and, 2)
recognition of the type of operation that the vehicle is conducting so
that the pedestrian can take appropriate measures. Our research has
shown that sounds that contain both broadband components and tones are
more likely to be recognized as vehicles. Sounds that contain only high
frequencies have a synthetic (and unpleasant) character.
[[Page 2820]]
Sounds with lower frequency tones and broadband components have a more
closely resemble the sound produced by an ICE vehicle. In the Phase 2
human factors research Volpe observed that sounds with strong tonal
components were more detectable.
While developing the acoustic parameters contained in this proposal
during Phase 3, parameters that were critical to recognition were
determined by simulating sounds. Sound simulations were developed for
the following vehicle operating scenarios: stationary but activated,
constant speed pass-bys, and accelerating pass-bys. Pass-bys included
Doppler shifts and accelerations also included a pitch shifting tied to
vehicle speed. The sound pressure levels changed as a function of speed
and as a function of position relative to the receiver during the
vehicle pass-by sound simulations. Roughly two hundred sounds were
generated and evaluated. Based on initial assessment of these sounds
and engineering judgment, at least one tone (and preferably more)
should be included in the acoustic specifications for HVs and EVs for
the purpose of recognition. The lowest tone should have a frequency no
greater than 400 Hz. A component is considered to be a tone if the
Tone-to-Noise ratio according to ANSI S1.13-1995 \73\ is greater than
or equal to 6 dB. (Note: the methodology in ANSI S1.13-1995 appears to
be overly conservative for the Phase 3 work. It may be better to: a)
either reduce the bandwidth, or b) include all tones within the band
for this calculation for the current application. Comments are
specifically sought on this issue).
---------------------------------------------------------------------------
\73\ Secretariat, Acoustical Society of America (1995).
Procedure for the computation of loudness of steady sound, American
National Standard ANSI S1.13. New York, NY.
---------------------------------------------------------------------------
Broadband components, which may be modulated, should be in each
one-third octave band from 160 Hz to 5000 Hz. Tones at frequencies
above 2000 Hz do not contribute to recognition. To aid in recognition
of vehicle acceleration and deceleration, the pitch (as measured by the
fundamental frequency) should increase and decrease by at least one
percent per km/hr of speed over the range from 0 km/hr to 30 km/hr.
Additional cues for recognition will be obtained by the movement of the
vehicle relative to the pedestrian, and were not considered for
potential acoustic specifications.
The following are recommendations to increase recognition based on
the Phase 3 research:
No greater than 50 percent amplitude modulation at
stationary but activated, at a frequency equal to the modeled
combustion frequency.
Ratios of the total tonal power to the total broadband
power should not exceed 15 dB. (Note: this is not the same as the Tone-
to-Noise Ratio).
Multiple harmonics with a fundamental equal to a
hypothetical combustion frequency.
The lowest harmonic included should be as low in frequency
as the countermeasure system can reliably produce.
The first or second harmonic present should have the
highest amplitude with higher harmonics generally decreasing in
amplitude.
Amplitude should increase as a function of speed beyond
the required change for minimum detection (but not beyond the maximum
level).
The agency solicits comments regarding the specific values, e.g. 50
percent, 15 dB, etc., as well as why characteristics should be
included/excluded from this list.
In addition to the recommendations for the recognition of HV and EV
sounds contained above, the Phase 3 research found the acoustic
requirements for HVs and EVs should include pitch shifting as an
element to enhance recognition. A pitch shifting requirement would keep
out melodies or sounds that change over time. The low-frequency
requirement would convey the sound of rotating machinery. Limiting
amplitude modulation would reduce annoyance and help with recognition,
as will excluding frequency modulation and the noise component of the
sound filter shapes with high roll-off rates.
D. International Approach to Pedestrian Alert Sounds
In 2009, the Ministry of Land, Infrastructure, Transport and
Tourism (MLIT) of Japan assembled a committee to study the issue of the
quietness of HVs. The committee concluded that an Approaching Vehicle
Audible System (AVAS) was a realistic alternative to allow pedestrians
who are blind or visually impaired to detect quiet vehicles. In 2010,
MLIT announced guidelines for AVAS based on the recommendations of the
study committee. Although several vehicles were considered in the
initial scope, MLIT concluded that AVAS should be installed only on HVs
that can run on electric motors, EVs and fuel-cell vehicles. In terms
of the activation condition, the MLIT recommended that AVAS
automatically generate sound at least in a speed range from the start
of a vehicle until reaching 20 km/h (12 mph) and when moving in
reverse. The AVAS would not be required when a vehicle is stopped. The
system may include a switch to temporarily halt the operation of the
AVAS. The reason for including this switch is because the committee
believes that the system is not needed on expressways where there are
no pedestrians and to reduce other issues such as drivers deliberately
increasing vehicle speed in order to stop the AVAS.
The MLIT included the following guidelines for the type and volume
for the sound generator system:
``The sound shall be continuous sound associating motor
vehicles running condition.''
``Siren, chime, bells, melody, horns sounds, animals,
insects, and sound of natural phenomenon such as wave, wind, river
current, etc., are not allowed.''
``The sounds generated shall be automatically altered in
volume or tone depending on the vehicle speed for easier recognition of
the movement of the vehicle.''
``Sound volume shall not exceed a level of the sound
generated when vehicles driven by internal combustion only run at speed
of 20 km/h.''
The use of `add-on' devices, generating sound continuously for five
seconds or longer, have been approved in order to increase AVAS
penetration. MLIT will look into social acceptability and verification
of technology implementation issues before moving from a voluntary
process to a mandate.\74\
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\74\ MLIT and JASIC (2010). Guidelines for Measure Against
Quietness Problem of HV. GRB Informal group on Quiet Road Transport
Vehicles (QRTV) Working papers of the 3rd informal meeting. Tokyo,
13-15 July 2010. Available at: http://www.unece.org/trans/main/wp29/wp29wgs/wp29grb/QRTV_3.html.
---------------------------------------------------------------------------
In addition to the actions taken in Japan the United Nations
Economic Commission for Europe (UNECE) World Forum for Harmonization of
Vehicle Regulation has an informal group on Quiet Road Transport
Vehicles (QRTV). The objective of the QRTV is to ``[d]etermine the
viability of `quiet vehicle' audible acoustic signaling techniques and
the potential need for their global harmonization.'' The QRTV's program
plan includes: review the available research; determine human factors
needed for pedestrians; develop technical performance parameters for
vehicles based on human factors needs; determine audible sound
characteristics and ways to convey desired vehicle performance
information to pedestrians; and determine technical and
[[Page 2821]]
economical feasibility of potential audible warning techniques.\75\
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\75\ QRTV (2010). Terms of Reference and Rules of Procedure for
the GRB Informal Group on Quiet Road Transport Vehicles (QRTV).
Available at: http://www.unece.org/trans/main/wp29/wp29wgs/wp29grb/QRTV_1.html.
---------------------------------------------------------------------------
UNECE has adopted guidelines substantially similar to the MLIT
guidelines discussed above with the same requirements and
recommendations.\76\ The guidelines are intended to provide
manufacturers with recommendations to follow in developing alert sound
systems for adding sound to quiet vehicles.
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\76\ http://www.unece.org/fileadmin/DAM/trans/main/wp29/wp29wgs/wp29gen/wp29fdoc/ECE-TRANS-WP29-78-r2e.pdf.
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E. SAE Sound Measurement Procedure
SAE J2889-1 SEP2011, Measurement of Minimum Noise Emitted by Road
Vehicles,\77\ is a performance-based and technology neutral test
standard. The standard specifies an objective method for measuring the
minimum noise emitted by road vehicles. The standard reflects the
development of engine and propulsion technologies that cannot be
correctly tested under other SAE standards. SAE J2889-1 SEP2011
specifies test site and meteorological conditions, as well as the
ambient noise level under which the sound should be recorded. The
standard includes provisions for outdoor and indoor (hemi-anechoic)
testing. The test procedure includes specifications for microphone
position, condition of vehicles (e.g., battery state, tires, warning
signals), operating condition (i.e., 10 km/hr (6 mph) and stopped),
measurement readings, and reporting requirements. SAE J2889-1 is
derived from SAE 2805, Measurement of Noise Emitted by Accelerating
Road Vehicles, and therefore some of the requirements related to
ambient, equipment, and facilities are the same.
---------------------------------------------------------------------------
\77\ See footnote 2.
---------------------------------------------------------------------------
The standard also includes procedures to evaluate external vehicle
sound generator systems for alerting pedestrians about a vehicle's
operating conditions. The outcome includes various acoustic metrics for
the external vehicle sound generators such as sound pressure level,
frequency content, and changes in sound pressure level and frequency as
a function of vehicle speed. SAE J2889-1 SEP2011 does not account for
psychoacoustic factors such as annoyance, recognizability, or
detectability.
SAE published a second version of SAE J2899-1 in May of 2012. This
version, SAE J2889-1 MAY2012, in addition to the provisions described
above, contains a bench test to allow the alert sound's shift in pitch
to be measured on a component level and a procedure to measure the
alert sound's shift in pitch on a vehicle level indoors. SAE J2889-1
MAY2012 also contains a procedure for measuring a ``commencing motion''
sound.
The International Organization for Standardization (ISO) is
cooperating with SAE in its efforts to develop a vehicle minimum noise
measurement standard. The ISO document ISO/NP 16254 Measurement of
Minimum Noise Emitted by Road Vehicles \78\ and SAE J2889-1 are
reportedly technically identical but this has not yet been confirmed by
NHTSA because the ISO document is still in draft form.
---------------------------------------------------------------------------
\78\ ISO/NP 16254 Measurement of Minimum Noise Emitted by Road
Vehicles. http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=56019.
---------------------------------------------------------------------------
F. Alert Sounds Currently Provided by Manufacturers
Automotive manufacturers that produce EVs for the U.S. market have
recently developed various pedestrian alert sounds. At the time that
PSEA was enacted, most manufacturers of HVs had not typically been
equipping those vehicles with alert sounds for the U.S. market. As of
the date of this writing, we have detailed knowledge of only one system
developed by Nissan. We know that others are under development and that
several manufacturers plan to equip their vehicles with these systems
in the near future. Nissan has developed a system called Approaching
Vehicle Sound for Pedestrians (VSP) for the 2011 Nissan Leaf.\79\ The
system consists of a digital sound synthesizer connected to a speaker
mounted under the hood of the vehicle and a sound control system. The
sound controller gets three inputs: Vehicle speed, gear position, and
brake signal. The VSP has an on/off switch located in the instrument
panel for temporary deactivation by the driver. A forward sound
activates at low speeds, fades off as the vehicle reaches 30 km/hr (18
mph) and fades back on as the vehicle speed reduces to 25 km/hr. The
pitch increases proportionally with vehicle speed. A unique sound is
activated when the gear is in ``reverse'' and when the vehicle starts
from a stopped position. No sound is emitted when the vehicle is in
``drive'' gear but stationary, but the vehicle does emit a sound when
stationary in ``reverse'' gear. The sounds emitted from the vehicle are
digitally generated as opposed to being a recording of an ICE vehicle,
and plays through speakers.
---------------------------------------------------------------------------
\79\ Konet et al. (2011) Development of Approaching Vehicle
Sound for Pedestrians (VSP) for Quiet Electric Vehicles. SAE
International. Paper No. 2011-01-0928. Abstract available at: http://saeeng.saejournals.org/content/4/1/1217.abstract.
---------------------------------------------------------------------------
Nissan indicates that the sound was designed to achieve the same
detectability as ICE sound while maintaining a quiet cabin for the
driver and without being intrusive to communities. The VSP was
developed based on three design guidelines. First, increase peak
frequency content between 600 and 800 Hz to improve detectability for
aging pedestrians with high frequency hearing loss. Second, increase
peak frequency content between 2000 and 5000 Hz to improve
detectability of pedestrians with normal hearing. Lastly, reduce
frequency content at around 1000 Hz to avoid noise intrusion. The VSP
was set to have a similar sound pressure level as a Nissan Versa 1.8L
at 10 km/hr (6 mph) while having two peaks at 630 Hz and 2500 Hz, and a
valley at 1000 Hz.
G. The Notice of Intent To Prepare an Environmental Assessment
On July 12, 2011, the agency published a Notice of Intent to
Prepare an Environmental Assessment (NOI) seeking comment on the
alternatives that the agency should consider when analyzing the
environmental consequences of a proposed quiet vehicle rule. The NOI
stated that the purpose and need of the rulemaking was to ``require EVs
and HVs, which tend to be quieter than the ICE vehicles, to be equipped
with a pedestrian alert sound system that would activate in certain
vehicle operating conditions to aid blind and other pedestrians in
detecting the presence, direction, location, and operation of those
vehicles.'' \80\
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\80\ 76 FR 40860 (July 12, 2011). The agency intends this
proposal to be technology neutral. The statement of purpose and need
in the NOI acknowledges, for the purposes of the agency's NEPA
analysis of the environmental impacts of this rulemaking action,
that many manufacturers will choose to install speaker systems on
their vehicles in order to meet the minimum sound requirements in
this proposal. This proposal establishes minimum sound requirements
that HVs and EVs must meet. It does not specify that vehicles must
be equipped with a speaker system.
---------------------------------------------------------------------------
The NOI discussed the following five alternatives that the agency
planned on considering in its analysis of the environmental
consequences of the rule and requested that the commenters propose
other alternatives for the agency to consider: (1) Taking no action;
(2) requiring alert sounds based on recordings of ICE vehicles; (3)
specifying acoustic requirements for synthetic sounds that would
closely resemble sounds produced by ICE vehicles; (4) setting
requirements for alert sounds that possess aspects of both
[[Page 2822]]
sounds produced by ICE vehicles and acoustic elements that contribute
to detectability; and (5) using psychoacoustic principals to develop
requirements for alert sounds that would have enhanced detectability
but would not necessarily have a reference to sounds produced by ICE
vehicles. The NOI stated that it was likely that a rule that allowed
alternatives 4 and 5 would need to include a jury testing procedure to
ensure that the sounds were recognizable to pedestrians as a motor
vehicle in operation.
Comments Received in Response to NOI
In response to the NOI, NHTSA received 33 comments from state
governments and Indian tribes, advocacy organizations for individuals
who are blind, national and international standards organizations, auto
manufacturers, heavy vehicle manufacturers, trade organizations that
represent motor vehicle manufacturers, component manufacturers,
environmental groups and private individuals. The agency received
comments on both the technical and environmental aspects of the NOI.
Most of the commenters expressed support for all of the
alternatives, except the no action alternative. All the commenters that
commented on possible methods for determining compliance with the
various alternatives stated that the performance criteria for alert
sounds should be based on objective factors and that jury testing was
not an appropriate method for determining compliance with an FMVSS.
Several of the commenters requested that the agency set the minimum
sound level requirements for EVs and HVs to the sound levels produced
by quiet ICE vehicles rather than the average sound pressure level
produced by ICEs. These commenters expressed concerns that if NHTSA set
the minimum sound pressure level requirements for EVs and HVs to the
average sound level produced by ICE vehicles, this would stop noise
reduction trends in vehicle design. Commenters that stated that the
minimum sound level requirements for EVs and HVs should be tied to
quiet ICE vehicles were also concerned about minimizing the
environmental effects of adding sound to EVs and HVs and driver
acceptance of the added sounds. One commenter stated that the acoustic
specifications developed by the agency should include a dB level dip in
the mid-range frequencies around 1000 Hz to limit the community noise
impact of adding sound to hybrid and electric vehicles.
Several commenters also questioned whether there was a safety need
for the agency to set minimum sound level requirements for the
stationary but activated operating condition. Most motor vehicle
manufacturers stated that the agency should only require that EVs and
HVs produce sound until the vehicle reaches a speed of 20 km/hr (12
mph) while advocacy groups for individuals who are blind stated that
EVs and HVs should produce sound until 32 km/hr (20 mph).
Light vehicle manufacturers stated that the agency should not be
overly concerned with writing the acoustic specifications for the alert
sound to prevent the use of annoying noises. These manufacturers stated
that they did not believe it was necessary to try to prevent annoying
sounds because manufacturers would not use annoying sounds as alert
sounds because they do not want to annoy their customers.
Several commenters stated that the agency should adopt the ECE
guidelines for alert sound systems (the ECE guidelines are based on the
Japanese guidelines discussed in Section VIII.E), as the agency's
requirements for alert sounds for HVs and EVs. These commenters
believed that the ECE guidelines provide manufacturers with flexibility
in developing sounds while appropriately balancing the needs of
pedestrians and concerns about environmental noise impact. In
discussions with the agency manufacturers have stated that they believe
that the ECE guidelines would address the agency's concerns about
annoying alert sounds.\81\
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\81\ See Section VIII. E. for a discussion of why we are not
proposing to adopt the Japanese or ECE guidelines.
---------------------------------------------------------------------------
Several commenters pointed out potential drawbacks in requiring an
alert sound that was a recording of an ICE vehicle.
The commenters requested that the agency maintain a significant
degree of flexibility in developing acoustic specifications for alert
sounds. Several commenters stated they did not believe that all of the
characteristics that the agency used to describe sounds comprising
alternative 5 were necessary to provide effective pedestrian alert
sounds. Advocacy groups for individuals who are blind also stated that
the agency should not allow alert sounds with none of the acoustic
characteristics of current ICE vehicles and that the agency should not
consider alternative 5 in specifying acoustic requirements for an alert
sound.
Some of the manufacturers of heavy vehicles stated that heavy-duty
hybrid vehicles that are not capable of electric propulsion should be
exempt from the requirements of the standard because these vehicles
produce sufficient sound for pedestrians to detect them in all
operating conditions, including stationary but activated. Several
commenters also stated that motorcycles should be exempt from the
requirements of the proposal.
A few of the commenters questioned whether adding sound to HVs and
EVs was an appropriate means of addressing the increased rate of
collisions between HVs and EVs and pedestrians. Three of these
commenters believed that avoiding pedestrian collisions was the
responsibility of the driver. One commenter believed that NHTSA should
address crashes between HVs and EVs and pedestrians by adding advanced
pedestrian crash avoidance technology to these vehicles.
VII. NHTSA's Proposal
NHTSA has considered three different viable alternatives for
ensuring that HVs and EVs provide detectable, recognizable sound cues
for pedestrians on which the agency seeks comments. These alternatives
include setting the minimum sound levels for EVs and HVs based on the
sound level required for a safe detection distance which is the
agency's preferred alternative, setting the minimum sound levels for
EVs and HVs based on the sound levels produced by light ICE vehicles
and using a jury testing procedure instead of acoustic specifications
to ensure that sounds produced by HVs and EVs are recognizable. The
alternatives differ in the manner in which they balance
recognizability, regulatory feasibility, and manufacturer flexibility.
In this section, we propose the alternative that we believe is the best
approach. The other two alternatives that are not being proposed, jury
testing for recognizability and acoustic profiles designed around
sounds produced by ICE vehicles, are discussed in detail in Section
VIII of this notice.
Under our proposal EVs and HVs would be required to produce sounds
that conform to the specifications listed in S5 of the Proposed
Regulatory Text (see Section XIII of this notice). Our proposal is
similar to Alternative 4 described in the previously referenced NOI as
it contains acoustic elements designed to enhance detection and to aid
with recognition of motor vehicle operation. Through a compliance test,
the agency would be able to easily measure the sound produced by an EV
or HV and determine whether that sound conforms to the requirements in
S5 of the proposed regulatory text. The
[[Page 2823]]
agency developed the acoustic specifications contained in this proposal
using a loudness model and a representative urban ambient sound level
to ensure that sounds fitting the specifications would be detectable in
a wide range of ambient noise conditions.
The agency has included specifications for low frequency because
the agency believes that the low frequency one-third octave band
requirements contained in S5 will assist pedestrians in recognizing
sounds that conform to the requirements as being produced by a motor
vehicle. The low frequency content of the sounds produced by current
ICE engines is the spectral component that pedestrians hear and
associate with these sounds. While the agency believes that the
specifications in S5 provide manufacturers a significant degree of
flexibility to develop vehicle sounds, the specifications do place some
constraints on the sounds that manufacturers are able to use as
countermeasure sounds. These constraints will ensure that
countermeasure sounds will be recognizable and provide the needed
auditory cues to be useful to pedestrians, while avoiding unnecessary
environmental impact.
The agency also developed and is seeking comment on a set of
minimum sound requirements for HVs and EVs using an analysis of sounds
produced by ICE vehicles. The proposed requirements include minimum
sound pressure level specifications in different one-third octave bands
so the frequency content of sounds produced by HVs and EVs would
resemble the spectral content of ICE vehicles. Sounds that meet these
proposed requirements would resemble sounds described in Alternative 3
of the NOI. Relative to the other two viable alternatives, this
approach would place primary emphasis on feasibility and
recognizability.
A. Acoustic Specifications Developed To Enhance Detection and
Recognition
This NPRM proposes performance requirements for sounds produced by
HVs and EVs so that pedestrians can detect, recognize, and locate these
vehicles. While NHTSA acknowledges that many manufacturers will choose
to install a speaker system to comply with the requirements of this
proposal, this is a technology neutral proposal, so manufacturers would
be able to choose any means of compliance they wish so long as the
vehicle produces a sound that complies with the acoustic specifications
in Section XIII of this notice.
The agency has sought to balance community noise impact with the
safety of pedestrians in developing the acoustic specifications
contained in this proposal. For people living in communities near
highways and along busy streets, elevated noise levels can be annoying
and diminish quality of life. The agency recognizes the contributions
motor vehicles make to ambient sound levels in urban areas and near
highways. The DOT's Federal Highway Administration has previously
conducted studies (not part of this rulemaking) that examine noise-
reducing pavements in an attempt to reduce tire noise produced by
vehicles. We note the research on noise reduction that is being
conducted by other operating administrations within DOT in order to
emphasize that this proposal is not contrary to, and will not interfere
with, noise reduction efforts. In setting a minimum requirement for
sound produced by HVs and EVs, the agency has sought to ensure these
sound level requirements would not contribute to transportation noise
pollution. A majority of transportation noise is caused by vehicles
traveling at high speed. In this proposal, the agency would set minimum
sound requirements for vehicles traveling at lower speeds. The proposal
would not affect vehicle noise output during the high speed scenarios
that contribute to noise pollution. Furthermore, as required by the
PSEA, the agency considered the maximum noise emission requirements for
heavy vehicles and motorcycles issued by the Environmental Protection
Agency (EPA) in setting the minimum sound requirements contained in
this proposal.\82\
---------------------------------------------------------------------------
\82\ 40 CFR parts 201-211.
---------------------------------------------------------------------------
In developing this proposal, NHTSA sought to maintain the current
situation involving ICE vehicles in which the pedestrian and the driver
share responsibility for avoiding pedestrian vehicle collisions. Thus,
a pedestrian must be able to hear a vehicle from the point at which the
vehicle would no longer be able to safely stop if the pedestrian
decided to walk into an intersection. A pedestrian must be able to
initiate a street crossing with the knowledge that there are no
vehicles present that would be unable to stop before colliding with the
pedestrian. At distances farther than the vehicle's stopping distance,
the driver would be able to respond to the presence of a pedestrian and
avoid a collision. At distances within which the driver would not be
able to respond to the presence of a pedestrian and stop the vehicle,
the pedestrian must be able to hear the vehicle so the pedestrian can
share responsibility for avoiding a crash by not stepping into the
street.
B. Critical Operating Scenarios
The PSEA states that the required safety standard must allow
pedestrians ``to reasonably detect a nearby electric or hybrid vehicle
in critical operating scenarios including, but not limited to constant
speed, accelerating, or decelerating.'' \83\ The PSEA defines alert
sound as ``a vehicle-emitted sound to enable pedestrians to discern
vehicle presence, direction, location and operation.'' \84\ Thus, in
order for a vehicle to satisfy the requirement in the PSEA to provide
an ``alert sound,'' the sound emitted by the vehicle must satisfy that
definition. In addition to the critical operating conditions mentioned
above, the agency believes that the definition of ``alert sound'' in
the PSEA requires the agency to establish minimum sound requirements
for when a vehicle is in a stationary but activated condition and while
operating in reverse.
---------------------------------------------------------------------------
\83\ Public Law 111-373, 124 Stat. 4086 (January 4, 2011).
\84\ Id.
---------------------------------------------------------------------------
1. Stationary But Activated
It is NHTSA's position that the scenario in which the vehicle is
stationary, but its starting system is activated \85\ is a critical
operating scenario because the definition of ``alert sound'' contained
in the PSEA requires that a pedestrian be able to locate a nearby
vehicle that is running; it is the agency's position that including
this scenario satisfies that provision of the PSEA. Furthermore, sound
provided by idling ICE vehicles is essential to assisting visually-
impaired pedestrians in making safe travel decisions. Sounds made by
vehicles that are stationary but activated address collisions between
pedestrians and HVs and EVs starting from a stopped position.
---------------------------------------------------------------------------
\85\ This condition is commonly referred to as an ``idling''
vehicle for vehicles with internal combustion engines. However, the
term ``idle'' technically refers to an engine state, not a vehicle
state, and has no relevance to electric motors. The description used
here ``stationary but activated'' means the vehicle is not moving,
but its starting system is activated.
---------------------------------------------------------------------------
The agency has concluded that the requirement in the PSEA that the
alert sound required by the agency should allow pedestrians to
``discern vehicle presence, direction, location, and operation,'' \86\
requires the agency to establish minimum sound requirements for the
stationary but activated operating
[[Page 2824]]
condition. As discussed in Section III of this notice, when read
together the terms ``presence'' and ``operation'' in the definition of
alert sound in PSEA require the agency to establish minimum sound
requirements when the vehicle is stationary, but the starting system is
activated.
---------------------------------------------------------------------------
\86\ Public Law 111-373, Sec. 2(2), 124 Stat. 4086 (2011).
---------------------------------------------------------------------------
As discussed in Section V of this notice, sound cues produced by
idling ICE vehicles are critical for the safety of blind pedestrians.
The sound produced by vehicles idling while waiting to pass through an
intersection provides a reference to visually-impaired pedestrians so
they are able to cross a street in a straight line and arrive safely at
the other side. The reference provided by idling vehicles is especially
important to provide auditory cues for visually-impaired pedestrians
crossing streets at complex intersections where the streets intersect
at non-perpendicular angles. The sound of vehicles idling on the far
side of the street while waiting to pass through an intersection also
provides visually-impaired pedestrians with a reference of how wide a
street is so they can accurately gauge the amount of time needed to
safely cross.
A sound emitted by an HV or EV when stationary but activated is
analogous to the ICE vehicle idling and ensures that the responsibility
to avoid a crash between a vehicle and a pedestrian is shared between
the driver of the vehicle and the pedestrian by providing pedestrians
with an acoustic cue that a vehicle may begin moving at any moment.
While there are some scenarios in which a driver starting from stop
should be able to see a pedestrian in front of the vehicle and thus
avoid a crash, the driver may not always be able to be relied upon,
especially in situations where the driver may have an obstructed view.
A driver pulling out of a parking space in a parking lot is an example
of a situation in which a driver might not be able to see a pedestrian
and the pedestrian may step into the path of a vehicle just as the
vehicle is beginning to move. If the pedestrian is able to hear the
vehicle before it begins to move the pedestrian would be able to
exercise caution and avoid a collision with the vehicle by not stepping
in front of the vehicle.
In deciding to include a sound requirement for HVs and EVs at the
stationary but activated condition, we also relied on the experiences
of agency staff when attempting to navigate street crossings while
blindfolded. NHTSA staff traveled to the national headquarters of the
National Federation of the Blind in Baltimore, Maryland to receive
training on white cane travel techniques used by individuals who are
blind. The meeting included a class room session and a session in which
the participants from NHTSA were blindfolded and trained on navigation
using a white cane outside on city streets with blind and visually
impaired individuals as guides. The participants from NHTSA attempted
to navigate city streets and cross at non-signaled intersections while
blindfolded. When approaching intersections, NHTSA staff found the
sound of idling vehicles necessary for determining whether there was a
vehicle present at the intersection and whether it was safe to cross.
Our October 2011 statistical report on the incidence rates of
crashes between HVs and pedestrians \87\ also supports stationary but
activated as a critical operating scenario for pedestrians. The report
shows six incidents of collisions when the vehicle was starting from a
stopped position. While the difference in HV and ICE vehicle crashes
with pedestrians for vehicles starting from a stopped position is not
statistically significant, this can be partially attributed to the
limited penetration of HVs in the fleet. There were no EV collisions
with pedestrians documented in NHTSA's report because electric vehicles
were not widely available in 2008, the last year for which data is
available. Overall, EVs and HVs represent a small percentage of the
total vehicle fleet and fully electric vehicles have yet to be
introduced to the U.S. fleet in significant numbers. Therefore, the
sample size of HVs represented in the State Data System, and the number
of HV pedestrian collisions, remains extremely small. The limited
available crash data does show that HVs have collided with pedestrians
when starting from a stopped position even though the sample size is
not large enough to prove a statistically significant incidence rate.
The growing penetration of HVs and EVs into the vehicle fleet means
that vehicle collisions with pedestrians when an HV or EV is starting
from a stopped position represents a safety concern that is rising to a
level of significance, for which the agency believes it is appropriate
to require that vehicles provide adequate sound cues while stationary
but activated. In passing the PSEA, Congress directed NHTSA to be
proactive in addressing the risk to pedestrians posed by HVs and EVs.
Congress did not intend for NHTSA to wait until crashes between
pedestrians and HVs and EVs starting from a stop rise to the level
where NHTSA has a data set that shows that a sound for the stationary
but activated condition is needed.
---------------------------------------------------------------------------
\87\ See footnote 36.
---------------------------------------------------------------------------
The agency does not believe that establishing minimum sound
requirements for EVs and HVs operating in the stationary but active
condition will have any noticeable impact on ambient noise levels. As
discussed in Section X.D, NHTSA has conducted an Environmental
Assessment (EA) to analysis the environmental effects of this
rulemaking. The EA shows that the difference in ambient sound levels if
the agency issues minimum sound requirements for the stationary but
active condition compared to if the agency did not require sound at
that condition would be negligible.
The agency does not believe that there would be any incremental
cost to requiring a sound at the stationary but active operating
condition to a vehicle that is already equipped with an alert sound
system. Rather, as with all other required operating scenarios, a
vehicle with an alert sound system could be reconfigured to play a
sound at the stationary but active condition through a simple software
modification, which would not require any additional equipment to be
installed on the vehicle.
In comments on the NOI and in meetings between representatives from
various auto manufacturers and NHTSA staff, several manufacturers
stated that the agency should not establish minimum sound requirements
for the stationary but activated condition. These manufacturers do not
believe there is a safety need for an alert sound when vehicles are
stationary but activated. They were concerned that the sound of EVs and
HVs standing in highway traffic and other scenarios in which
pedestrians would not be expected to be present would unnecessarily
contribute to increases in environmental noise impact.
Advocacy organizations for individuals who are blind or visually
impaired believe that the agency should establish minimum sound
requirements for the stationary but active condition. In meetings with
agency rulemaking staff, representatives from NFB have stated that a
sound at the stationary but active operating scenario is necessary for
the safety of blind or visually impaired pedestrians in avoiding
collisions with EVs and HVs operating at low speeds. Representatives
from NFB stated that blind individuals exercise greater caution when
they hear a nearby idling ICE vehicle because they know that the
vehicle could begin moving at any moment. Representatives from NFB
stated that a nearby vehicle that made no sound that could start
[[Page 2825]]
moving at any moment presents a safety hazard to blind or visually
impaired pedestrians because the vehicle could collide with a blind or
visually impaired pedestrians without the pedestrian even knowing that
the vehicle posed a danger to them. The agency believes that minimum
sound levels for EVs and HVs operating when stationary but activated
are necessary from a safety perspective for the reasons previously
discussed. The agency believes that it is important to establish
minimum sound requirements for the stationary but activated condition
so that the sound will alert nearby pedestrians of the presence of a
vehicle without unduly contributing to overall ambient noise levels.
The agency believes that the safety interest in assisting pedestrians
with detecting nearby vehicles and providing the visually-impaired with
acoustic cues necessary to make safe travel decisions justifies
establishing minimum sound level requirements for EVs and HVs operating
when stationary but activated.
The agency acknowledges that with the technology under
consideration today for adding sound to HVs and EVs, most vehicles that
would be subject to this proposed rule (should it become final) will
establish compliance by means of adding a sound generating system that
includes at least one speaker. Requiring a sound at this condition may
result in manufacturers adding speakers to some vehicles (for example
motorcycles or some heavy vehicles) that may not otherwise need a
speaker to meet the requirements of the other operating conditions in
today's proposal (because the vehicle operation in those conditions
makes enough sound without adding an artificial sound). However, we
believe that the definition of alert sound in the PSEA requires the
agency to establish minimum sound requirements for this condition. We
seek comment on the number of vehicles to which this proposal would
apply that would only require speakers to meet the acoustic
requirements in this proposal at the stationary but active condition.
Also, the agency solicits comment on possible configurations of the
alert sound that would lower or deactivate the alert sound in
situations in which pedestrians would not be present. One of the
methods proposed for mitigating the noise caused by stationary EVs and
HVs would be to allow the vehicle to reduce or turn off its sound after
the vehicle had been stationary for a period of five to ten minutes.
The agency does not believe that a switch that would allow the driver
to turn off the vehicle's sound is a viable option for controlling the
noise impact of EVs and HVs when stationary but activated because the
PSEA specifically forbids the agency from allowing the driver to
deactivate the sound; in addition, the agency believes that allowing
drivers to deactivate the sound would compromise pedestrian safety.
As an alternative to requiring a sound when the vehicle is
activated but not moving, Mercedes-Benz USA, LLC (Mercedes) stated that
the agency should instead include acoustic specifications for a
``commencing motion sound'' that would be activated as soon as the
vehicle starts moving.\88\ Mercedes stated that the specifications for
such a sound should be the same as the specifications for the sound at
10 km/hr (6 mph). Mercedes stated that the sound pressure level of the
``commencing motion sound'' should be noticeably higher than the sound
pressure level required for low speeds. Volkswagen Group of America,
Inc. also stated that the agency should require a ``commencing motion
sound'' instead of a sound when the vehicle is activated but
stationary. We seek comment on whether requiring a ``commencing motion
sound'' is as an effective approach to implementing the requirements in
the PSEA that an alert sound allow pedestrians to discern the
``presence, direction, location and operation'' of the vehicle as
establishing minimum sound requirements for when the vehicle is
activated but stationary.
---------------------------------------------------------------------------
\88\ Docket No. NHTSA-2011-0148-0029.
---------------------------------------------------------------------------
2. Reverse
The agency believes that reverse is a critical operating scenario
for which the agency should issue minimum sound level requirements for
HVs and EVs to provide acoustic cues to pedestrians to prevent
pedestrian collisions and to satisfy the requirements of the PSEA.
Requirements for the reverse operation of EVs and HVs will ensure that
these vehicles provide sound cues to pedestrians so pedestrians will be
able to avoid these vehicles when the vehicles are backing out of
parking spaces or driveways.
Several manufacturers in meetings with NHTSA staff stated that
minimum sound requirements for EVs and HVs operating in reverse were
not necessary because the agency's proposed amendments to FMVSS No.
111, Rear Visibility, as required by the Cameron Gulbransen Kids
Transportation Safety Act, would allow drivers to see pedestrians while
backing and thus avoid collisions. NHTSA's proposed amendments to FMVSS
No. 111, while intended to address vehicle collisions with pedestrians
while backing, do not fully ensure that EVs and HVs will not experience
higher rates of pedestrian collisions than ICE vehicles while backing.
Establishing minimum sound level requirements for reverse operation
will ensure that both the pedestrian and the driver continue to have
the ability to avoid pedestrian vehicle collisions. If EVs and HVs do
not produce audible sound levels during reverse operations,
pedestrians, especially those who are blind and visually impaired,
would not have the opportunity to avoid collisions with backing
vehicles because they would not be able to tell that they are being
threatened by a backing vehicle.
NHTSA's report on the incidence rates of crashes between HVs and
pedestrians found 13 collisions with pedestrians when a HV is backing.
The difference between the incidence rates of HVs involved in
pedestrian crashes while backing and the incidence rate of ICE vehicles
involved in pedestrian crashes while backing was not statistically
significant. We do not believe that the lack of a statistically
significant difference in incidence rates between ICE vehicles and HVs
involved in pedestrian crashes while backing can be attributed to the
absence of a safety problem related to a vehicle's noise level during
this operating condition. As discussed above, the absence of a
difference in the incidence rates in backup pedestrian crashes between
ICE vehicles and HVs is, the agency believes, due to the low
penetration of these vehicles into the fleet and the sample size of HVs
and EVs in the State Data System. Also, backing incidents with
pedestrians may tend to be underreported because they occur in parking
lots, garages, and drive ways, as well as other ``off roadways'' that
traditionally have not been captured by existing data collection
systems.
NHTSA believes that the PSEA requires the agency to set minimum
sound requirements for the backing scenario for the same reason that
the agency believes that minimum sound requirements are necessary for
the stationary but activated condition. The PSEA requires minimum sound
level requirements promulgated by NHTSA to allow pedestrians to discern
vehicle presence and operation. A vehicle moving in reverse is
unquestionably operating, thus a minimum sound level is required for
this condition.
The PSEA also requires that the minimum sound level requirements
promulgated by NHTSA allow pedestrians to discern the direction of the
vehicle. This language also indicates that the PSEA requires any
standard to establish minimum sound requirements
[[Page 2826]]
for when the vehicle is operating in reverse.
3. Acceleration and Deceleration
Section 5 of the proposed regulatory text would ensure that sounds
produced by EVs and HVs that meet the requirements of this proposal
will allow pedestrians to determine when a vehicle is accelerating or
decelerating. Pitch shifting is the sound characteristic that
pedestrians currently associate with an accelerating vehicle based on
the sounds produced by an ICE vehicle. The agency included requirements
for pitch shifting in S5 to ensure that components of the sounds
produced by EVs and HVs moved along the frequency spectrum in a manner
similar to those of ICE vehicles as vehicle speed increases. Pitch
shifting will also denote that the vehicle is decelerating. The sound
pressure level in each one-third octave band required in S5 changes as
speed increases, leading to an increasing overall sound pressure level
that corresponds to the behavior of an ICE vehicle. Thus, in addition
to the acoustic cues provided by pitch shifting, pedestrians will be
able to tell if an EV or HV is accelerating or decelerating based on
the increase or decrease in sound emitted from the vehicle, just as
they would be able to in the case of an ICE vehicle.
The agency did not include a separate acoustic measurement
procedure for acceleration and deceleration because we believe that the
requirements for pitch shifting and the increase in overall sound level
as the vehicle increases speed (or the decrease in sound level as the
vehicle decelerates) will provide enough information so that
pedestrians will be able to determine when EVs and HVs are accelerating
and decelerating. The agency also decided not to include acoustic
measurement procedures for acceleration and deceleration because of
concerns about the feasibility of testing in these conditions. It is
difficult for even an experienced test driver to repeatedly achieve and
maintain a specific rate of acceleration or deceleration over the
distance used in the proposed test procedure. Given the difficulty of
ensuring repeatable results of an acoustic test measuring acceleration
and the fact that information about changes in vehicle speed is
provided by pitch shifting and increases and decreases in sound
pressure level corresponding to changes in vehicle speed, NHTSA decided
that the test procedure did not need to include a dynamic test for
acceleration or deceleration.
4. Constant Speed
The agency is proposing to ensure that EVs and HVs produce a
minimum sound level necessary for safe pedestrian detection at constant
speeds by measuring vehicle sound output at 10 km/hr (6 mph), 20 km/hr
(12 mph) and 30 km/hr (18 mph). The agency's proposal would ensure EVs
and HVs produce sound that is sufficient to allow pedestrians to detect
these vehicles at all speeds between 0 and 10 km/hr (6 mph), 10 km/hr
(6 mph), 20 km/hr (12 mph), and 30 km/hr (18 mph) by requiring that the
minimum sound levels be attained for all speeds between these test
speeds. The proposal contains minimum acoustic requirements up to the
speed of 30 km/hr (18 mph) because, for the reasons discussed in
Section VII.E.3 of this notice, the agency believes that this is the
appropriate cross over speed. Manufacturers have suggested in meetings
with the agency that the test procedure for sound measurement should
only specify a pass by test at 10 km/hr (6 mph) because, according to
manufacturers, this is the speed at which the sound levels produced by
ICE vehicles and EVs and HVs differ the most. The agency believes that
it is necessary to include pass by tests at speeds up to and including
the crossover speed to ensure that EVs and HVs meet the minimum sound
level requirements for all speeds for which requirements are specified.
C. Application
1. The Definition of Hybrid Vehicle
The PSEA defines hybrid vehicle as a vehicle with more than one
means of propulsion. The agency has concluded that the definition in
the PSEA requires the agency to apply the standard only to hybrid
vehicles that are capable of propulsion in any forward or reverse gear
without the vehicle's ICE operating. Under the agency's interpretation
of the definition of hybrid vehicle in the PSEA, more than one means of
propulsion means more than one independent means of propulsion. This
proposed definition of hybrid vehicle would exclude from the
application of the proposed standard those vehicles that are equipped
with an electric motor that runs in tandem with the vehicle's ICE to
provide additional motive power when the vehicle is accelerating.\89\
---------------------------------------------------------------------------
\89\ The agency is aware that a vast majority of vehicles that
are equipped with an electric motor to provide additional motive
power when the vehicle is accelerating are equipped with idle-stop.
For a discussion of why the agency has chosen not to require
vehicles equipped with idle-stop that are not capable of propulsion
by a means other than the vehicle's ICE to meet the minimum sound
level requirements in this proposed standard see Section VII.C.5.
---------------------------------------------------------------------------
Because the ICE is always running when these vehicles are in motion
on hybrids that employ the electric engine to provide additional power
when accelerating, the fact that these vehicles may not provide
sufficient sound for pedestrians to detect them cannot be attributed to
the vehicle's propulsion source. If a pedestrian cannot hear this type
of vehicle it is because of the quietness of the vehicle's ICE.
Therefore, we believe that it is most appropriate to address vehicles
that are equipped with an electric motor that provides assistance to
the ICE when the vehicle is accelerating in the report to Congress
regarding the safety need to establish minimum sound requirements for
quiet ICE vehicles required by the PSEA.
The agency would also like to note that the definition of ``hybrid
vehicle'' in the PSEA is not limited to hybrid-electric vehicles. Thus,
the standard would apply to hybrid vehicles that operate using
hydraulic propulsion independently of the vehicle's ICE.
2. Vehicles With a GVWR Over 10,000 Pounds
NHTSA is proposing that the acoustic specifications in Section XIII
apply to all hybrid and electric motor vehicles covered by the PSEA,
including all hybrid and electric passenger cars, multipurpose
vehicles, trucks, buses, low-speed vehicles and motorcycles.\90\
---------------------------------------------------------------------------
\90\ The PSEA specifically excludes trailers from the scope of
the required rulemaking.
---------------------------------------------------------------------------
Across the entire fleet (ICE, hybrid, and electric vehicles
included), heavy vehicles have a lower pedestrian crash rate than light
vehicles (10,000 pounds and less). Only 0.3 percent of all heavy
vehicle crashes involved pedestrians while 0.59 percent of all light
vehicle crashes involve pedestrians. The pedestrian crash rate of heavy
vehicles involved in low-speed maneuvers is also lower than that of
light vehicles. Only 0.42 percent of all heavy vehicle crashes at low
speeds involved pedestrians while 0.80 percent of all low speed light
vehicle crashes involve pedestrians.
NHTSA was not able to determine a separate pedestrian crash rate
for hybrid and electric heavy duty vehicles based on the data available
in the State Data System. The sample of all crashes of hybrid and
electric heavy vehicles in the State Data System is extremely limited
and the State Data System did not, when it was examined, contain any
incidents of hybrid or electric heavy vehicle pedestrian crashes. The
agency
[[Page 2827]]
believes that the lack of crash data on hybrid and electric heavy
vehicles is due to the very low market penetration of these vehicles at
the present time. Therefore, the agency attributes the lack of any
hybrid or electric heavy vehicle pedestrian crashes not to the fact
that these vehicles provide sufficient sounds levels to allow safe
pedestrian detection but instead to the fact that these vehicles are
not present in the fleet in any significant numbers. The agency
believes that it is reasonable to assume that as hybrid and electric
heavy vehicles achieve a higher penetration into the vehicle fleet that
the difference between the crash rates for hybrid and electric heavy
vehicles and ICE heavy vehicles will be similar to the difference in
crash rates between light hybrid and electric vehicles and light ICE
vehicles.
We note that the PSEA did not exclude vehicles with a GVWR over
10,000 pounds from the scope of the required rulemaking. We believe
Congress intended the agency to be proactive in addressing the safety
problem posed by quiet hybrid and electric heavy vehicles before hybrid
and electric heavy vehicle pedestrian crashes begin to show up in crash
data bases in significant numbers. In other words, through the passage
of the PSEA, Congress has determined that there is a safety need for
HVs and EVs of various sizes to produce a minimum sound level.
The agency recognizes that there are some challenges in including
vehicles with GVWR over 10,000 lbs in the current rulemaking. The
agency has not determined the extent to which hybrid heavy vehicles
produce less sound than their traditional ICE peer vehicles. The agency
also is not aware of the extent to which hybrid electric vehicles with
a GVWR of over 10,000 lbs are capable of propulsion using only electric
power without the ICE running.\91\ Heavy vehicle manufacturers, in
their comments on our NOI, stated that to the extent that heavy
vehicles are not capable of propulsion solely by some means other than
the vehicle's ICE, they should be exempt from the requirements of this
proposal.
---------------------------------------------------------------------------
\91\ In its comments to the Notice of Intent to Prepare an
Environmental Assessment (NOI) that the agency issued to solicit
comments on the environmental consequence of this rulemaking, Hino
Motors, Ltd. stated that it is planning on introducing a heavy-duty
hybrid truck that is capable of propulsion using only the electric
motor. Hino, however, stated that even when the truck is being
propelled by the electric motor the ICE will remain on in order to
power auxiliary systems. Comment of Hino Motors Ltd. available at
www.regulations.gov, Docket No. NHTSA-2011-0100-0015.
---------------------------------------------------------------------------
While the agency is today proposing to include heavy vehicles as
part of this rulemaking, we note that the agency intends to conduct
further research before issuing a final rule to determine the sound
levels produced by heavy-duty hybrid and electric vehicles and to
establish whether the sound requirements for light vehicles are also
appropriate for heavy vehicles.
The agency is also aware of practical concerns about acoustic
testing of heavy vehicles. The agency is aware that there are a limited
number of noise pads necessary for vehicle acoustics testing that can
accommodate heavy vehicles. We seek comment on whether it is necessary
to test heavy vehicles on a noise pad meeting the requirements of ISO
10844, Acoustics--Specification of test tracks for measuring noise
emitted by road vehicles and their tires. In the alternative the agency
is considering specifying an acoustic testing surface for heavy vehicle
testing that is based on a typical vehicle test track pavement.
The agency also has not validated whether the sound specifications
that it has developed based on research conducted on light vehicles
would provide appropriate countermeasure sounds for heavy-duty
vehicles. We seek comment on this issue.
The agency is aware that many heavy and medium duty trucks are
equipped with backup alarms to provide warning when the vehicle is
backing. Because we do not want to require that these vehicles produce
additional sound if they are already producing sound when backing, we
would not require vehicles with a GVWR over 10,000 pounds to meet the
acoustic specifications in S5.1.2 when backing. Instead, these vehicles
would only be required to produce a sound with an overall sound
pressure level of 52 A-weighted dB when backing. We seek comment on
this issue. In addition, the agency also has yet to determine whether
it is necessary from a safety perspective for pedestrians to
differentiate light vehicles from heavy vehicles. The agency is aware,
based on conversations with advocacy groups representing people that
are visually-impaired, that a visually-impaired person may wait a
longer amount of time than normal to cross a street after hearing a
heavy truck pass in order to avoid colliding with a trailer that might
be attached to the truck.
The agency also seeks comment regarding the appropriateness of
limiting the application of this proposal to vehicles with a gross
vehicle weight rating of 10,000 pounds and less.
Another regulatory option that the agency considered for heavy-duty
HVs and EVs would require that these vehicles produce only a minimum
sound pressure level rather than the full set of acoustic
specifications in S5. Pending planned research on the sounds emitted by
heavy vehicles, ICE, HV, and EV, the agency has tentatively concluded
that applying the full acoustic specifications that the agency intends
to apply to light vehicles to heavy vehicles would better fulfill the
requirements of the PSEA.
3. Electric Motorcycles
The agency has tentatively concluded that the minimum sound level
requirements in S5 proposed in this notice should apply to electric
motorcycles (we are not aware of the existence of any hybrid
motorcycles). Motorcycles are not specifically excluded by the PSEA.
Also, the agency has yet to determine that these vehicles provide sound
levels that are sufficient to allow pedestrians to detect these
vehicles in time to avoid collisions.
Table 10 shows the number of collisions between motorcycles and
pedestrians from 2000 until 2008. This data was obtained from the State
Data System. Because the State Data System does not include any data
regarding the power source used by motorcycles, the agency was not able
to determine if the incidence rate of collisions between pedestrians
and electric motorcycles is different between the incidence rate of
collisions between pedestrians and motorcycles with ICEs.
[[Page 2828]]
Table 10--Preliminary Results of Motorcycle Crashes
[16 States during 2000-08]
----------------------------------------------------------------------------------------------------------------
Backing
entering/exit Straight
parking spots, moving and
turning, other normal Total
starting, and speeds
slowing
----------------------------------------------------------------------------------------------------------------
Pedestrian crashes.............................................. 55 438 493
Other crashes and missing data.................................. 20,669 90,371 111,040
-----------------------------------------------
Total....................................................... 20,724 90,809 111,533
----------------------------------------------------------------------------------------------------------------
As with heavy-duty vehicles, there are challenges in establishing
minimum sound levels for electric motorcycles in this rulemaking. The
agency has not determined the extent to which electric motorcycles have
a greater risk of collisions with pedestrians than motorcycles with
ICEs or the extent to which electric motorcycles are quieter than ICE
motorcycles of the same type. The agency has not measured any
motorcycles according to the procedures contained in this proposal so
the agency has yet to determine whether the measurement procedure used
to measure sound emitted by 4-wheeled vehicles would be appropriate for
motorcycles.
BMW of North America, LLC (BMW), in its comments on the NOI
(discussed in Section VI.G. above), submitted crash data on incidents
of motorcycle collisions with pedestrians. BMW stated that based on the
number of crashes between motorcycles and pedestrians and the
percentage of pedestrian crashes involving motorcycles, there is no
safety need for minimum sound requirements for electric motorcycles.
BMW cited several different sources of data to illustrate the low rates
of crashes between motorcycles and pedestrians. 2009 statistics from
the New York Department of Motor Vehicles show that approximately 0.4
percent of pedestrian/motor vehicle collisions involved
motorcycles.\92\ Data from the FARS for the period between 2005 and
2009 shows that only 0.7 percent of the pedestrian fatalities during
that period involved motorcycles colliding with pedestrians. Data from
the NHTSA's General Estimates System (GES) for the same time period
shows that 1.07 percent of the pedestrians injured in motor vehicle
crashes were injured in crashes involving motorcycles.
---------------------------------------------------------------------------
\92\ BMW's comments on the NOI. Available at,
www.regulations.gov, Docket No. NHTSA-2011-0100-0020.
---------------------------------------------------------------------------
Both BMW and the Motorcycle Industry Council (MIC) stated that
because of unique attributes of motorcycles, there is no safety need
for NHTSA to establish minimum sound levels for electric motorcycles.
According to MIC and BMW, motorcycle riders are able to better see and
avoid pedestrians than automobile drivers because their view is
unobstructed by pillars and sun visors and they are more alert because
they themselves are vulnerable road users. BMW and MIC maintained that
because motorcycles are unstable at low speeds, riders are required to
maintain a high level of alertness, which minimizes the likelihood of
collisions with pedestrians during low speed maneuvers.
Both BMW and MIC stated that adding a speaker system to a
motorcycle could involve technical challenges not present for other
vehicles. MIC and BMW claimed that it would be more difficult to add a
speaker to a motorcycle than a passenger car because there is less
space available on a motorcycle for a speaker system, the weight of the
system would be a larger percentage of the vehicle's weight, which
could affect low-speed stability, energy consumption by the speaker
system would have a greater impact on a vehicle's range, and the price
of installing the system would be higher than that for other vehicles.
MIC and BMW also claimed that electric motorcycles should not be
subject to the minimum sound level requirements in this proposal
because electric motorcycles are not quiet.\93\
---------------------------------------------------------------------------
\93\ MIC submitted measurements of overall sound pressure level
of two electric vehicle models recorded at 8 km/hr (5 mph) and 16
km/hr (10 mph) in its comments to the NOI. MIC did not provide any
measurements of overall sound pressure level for ICE motorcycles as
a comparison. Available at, www.regulations.gov, Docket No. NHTSA-
2011-0100-0028.
---------------------------------------------------------------------------
The agency acknowledges that establishing minimum sound
requirements for electric motorcycles raises unique issues that are not
present for other light vehicles. The agency, however, notes that
because this proposal is technology neutral, it would be possible for
electric motorcycles to meet the requirements of this proposal without
the use of a speaker system. The agency seeks comment on whether the
minimum sound level requirements in this proposal should apply to
electric motorcycles. The agency seeks comment on the crash risk to
pedestrians and pedalcyclists posed by electric motorcycles and the
cost of the proposal as applied to these vehicles.
4. Low-Speed Vehicles
The agency has tentatively concluded that low-speed vehicles (LSVs)
must meet the requirements in this proposal. While the agency expects
that LSVs that run via an electric motor are extremely quiet, the
agency has not conducted any acoustic measurements of these vehicles to
determine the amount of sound they produce. The agency has very limited
real-world data on crashes involving LSVs so the rate at which these
vehicles are involved in pedestrian collisions is unknown. The agency
has not yet determined the extent to which minimum sound levels
developed for light vehicles would be appropriate for LSVs. The agency
seeks comment on whether the requirements in this proposal should apply
to LSVs.
5. Quiet ICE Vehicles
The agency does not intend to require a minimum sound level for
quiet ICE vehicles in this rulemaking. The agency is aware that,
similar to HVs and EVs, some ICE vehicles may pose a risk to
pedestrians because of the low level of sound that they produce when
operating at low speeds. The PSEA requires the agency to study and
report to Congress whether there is a need for the agency to apply the
minimum sound requirement established for HVs and EVs to ICE vehicles
so that these vehicles can be readily detected by pedestrians. If,
after the study, the agency determines that there is a safety need to
apply these minimum sound requirements to quiet ICE vehicles, NHTSA is
required to initiate a rulemaking to do so. The agency is also aware
that many manufacturers intend
[[Page 2829]]
to make idle stop technology available on ICE vehicles in the near
future.\94\ The agency realizes that the introduction of ICE vehicles
equipped with idle stop means that there will be ICE vehicles that will
be effectively silent when the vehicle is not moving. While the agency
does not propose, in this rulemaking, to require that ICE vehicles
equipped with idle stop produce a minimum sound level while at idle,
the agency plans to consider whether vehicles equipped with idle stop
have a greater risk of collision with pedestrians than vehicles that
produce a sound at idle with an eye toward a rulemaking in the future
to address this issue.
---------------------------------------------------------------------------
\94\ Vehicles equipped with an idle stop function shut down or
slow the vehicle's engine when the vehicle comes to a stop. Because
the vehicle's engine shuts off, the vehicle is no longer providing
any acoustic cues to pedestrians to indicate its presence.
---------------------------------------------------------------------------
D. Requirements
The agency's preferred method for establishing minimum sound
requirements for EVs and HVs uses a detectability model to determine
the sound that the vehicle needs to produce to allow pedestrians to
detect the vehicle at a given distance. The sounds that meet the
minimum requirements using the detection model would be similar to
those described in Alternative 4 in the NOI.
1. Acoustic Parameters Designed According to a Detectability Model
The two critical aspects of the minimum sound level requirements in
this proposed approach are that the sound be detectable and
recognizable. This approach addresses the detectability aspect of the
minimum sound level requirements by determining the sound
specifications needed for a pedestrian to detect a vehicle at a safe
distance and by examining the typical ambient sound profile to
determine which one-third octave bands contribute the most to a
pedestrian's ability to detect vehicles.\95\ This proposal addresses
the pedestrian recognition aspect of the minimum sound requirements by
insuring that the sound has aspects that allow pedestrians to recognize
the sound as being produced by a motor vehicle and by allowing the
pedestrian to recognize the mode of operation of the vehicle.
---------------------------------------------------------------------------
\95\ The agency's research to develop the minimum specifications
for alert sounds for hybrid and electric vehicles is discussed in
greater detail in the agency's report ``Research on Minimum Sound
Specifications for Hybrid and Electric Vehicles.''. Available at
Docket No. NHTSA-2011-0148-0048.
---------------------------------------------------------------------------
The agency developed the minimum detectability requirements for HVs
and EVs by first determining the distance at which a pedestrian would
need to hear a vehicle in order to make a decision about whether it was
safe to cross the street. Thus, the distance at which a pedestrian
would need to hear a vehicle is at least as long as the vehicle's
stopping distance. At distances shorter than a vehicle's stopping
distance the pedestrian must be able to hear the vehicle, otherwise a
situation might develop in which the pedestrian steps off the curb
(because s/he cannot hear the vehicle) and the driver of the vehicle
would be unable to stop the vehicle in time to avoid a collision with
the pedestrian.
The agency set the distance at which it believes that the
pedestrian should be able to hear an approaching HV or EV, also
referred to as the detection distance, using stopping sight distances
computed from the guide on highway design \96\ of the American
Association of State Highway Transportation Officials (AASHTO).
Stopping sight distance is the distance that enables a vehicle
traveling at or near the design speed to stop before reaching an object
in its path. The stopping sight distance is the sum of the driver
reaction distance and the braking distance. The driver reaction
distance is the distance traveled by a vehicle from the instant the
object becomes visible to the driver to the instant the driver applies
the brakes. The braking distance is the distance needed to stop the
vehicle once the driver applies the brakes. The sight distance for a
vehicle traveling at the design speed and on a level road can be
computed with the following formula:
---------------------------------------------------------------------------
\96\ American Association of State Highway and Transportation
Officials, A Policy on Geometric Design of Highways and Streets,
Chapter 3 Elements of Design (2004).
[GRAPHIC] [TIFF OMITTED] TP14JA13.031
---------------------------------------------------------------------------
Where:
t = brake reaction time, s
V = design speed, km/hr
a = deceleration rate, m/s\2\
Drivers typically brake at an average emergency deceleration of about
5.4 m/s\2\ on dry roads. A comfortable deceleration for most drivers
braking on wet surfaces is 3.4 m/s\2\. Drivers' expectation plays a
role in driver reaction time. Mean reaction time to unexpected, but
common, events is about 1.25 seconds. Mean reaction time for surprise
events, such as an object suddenly moving into the drivers' path is
about 1.5 seconds. A longer reaction time, of 2.5 seconds would
consider the capabilities of almost all drivers, including older
drivers and distracted drivers.
The values used as the basis for this proposal are 5.4 m/s\2\ for
deceleration and 1.5 seconds for brake reaction time. We chose the 5.4
m/s\2\ deceleration rate corresponding to dry pavement braking because
most of the pedestrian crashes that the agency identified occurred in
clear conditions \97\ and the slower deceleration rate for wet
pavement, we believe, would result in a sound profile that is
unnecessarily loud for most conditions. The agency believes that 1.5
seconds is an appropriate value to use for driver reaction time (to
stopped objects) because this represents the reaction time of most
drivers for surprise events.\98\
---------------------------------------------------------------------------
\97\ See footnote 5.
\98\ Green (2000) How Long Does It Take to Stop? Methodological
Analysis of Driver Perception-Brake Times.'' Transportation Human
Factors 2(3) 195-216.
---------------------------------------------------------------------------
Based on calculations using these values, the agency determined
that the desired detection distances were 2 meters in front of the
vehicle for stationary but activated, 5 m in front of the vehicle for
the 10 km/hr (6 mph) pass by, 11 m for the 20 km/h (12 mph) pass-by
operation, and 19 m for 30 km/h (18 mph) pass-by operation. The results
of this computation were rounded up to the nearest meter. Levels were
increased by 0.5 dB to provide a small safety factor and rounded to the
nearest integer for simplicity. This small increase was deemed
sufficient due to other conservative aspects of the estimation, e.g.
multiple detection opportunities due to the multiple components. The
agency solicits comment on the appropriateness of a 1.5 second reaction
time and 5.4 m/s\2\ declaration rate in determining the desired
detection distances.
Due to a variety of factors that affect the manner in which sound
moves through an environment, it is not practical to measure sound with
the specificity that the agency desires from the distances at which
pedestrians need to be able to detect the sound. Atmospheric
absorption, ground conditions and divergence of sound all affect sound
measurements conducted at distances greater than the two meters
specified in SAE J2889-1. Acoustic measurements conducted at distances
greater than two meters are not able to accurately record a sound's
frequency profile at the one-third octave band level. Furthermore,
because of attenuation, a sound's decibel level decreases the further a
measurement is taken from the sound source. At the detection distances
that the agency
[[Page 2830]]
believes are necessary for pedestrians to be able to hear vehicles, the
sound pressure level sounds produced by vehicles begin to approach the
ambient. As the sound pressure level begins to approach that of the
ambient sound level, it is more difficult to measure the frequency
composition of the sound. Based on the factors discussed above, the
agency determined that the best approach for determining the minimum
sound level HVs and EVs need to produce to ensure safe detectability
would be to determine what the sound level would need to be at two
meters from the vehicle in order to allow the pedestrian to hear the
sound at the desired detection distance.
Using the method below, it is possible to determine what the sound
levels of the vehicle will need to be at a distance of two meters from
the vehicle so that pedestrians will be able to detect the sound at the
desired detection distance. The table below depicts how the sound
produced by the vehicle attenuates when measured using the procedure in
SAE J2889-1.
Table 11--Computation of Adjustment of SPL (A-Weighted dB) From Source to SAE Microphone Location
----------------------------------------------------------------------------------------------------------------
----------------------------------------------------------------------------------------------------------------
Speed, km/hr................................................. 10 20 30
X source, meters............................................. 5 11 19
Y source,* meters............................................ 2 2 2
r0,** meters................................................. 2.3 2.3 2.3
r1,** meters................................................. 5.5 11.2 19.1
r doubling................................................... 1.2 2.3 3.0
Attenuation, dB.............................................. -6.0 -12.2 -16.8
----------------------------------------------------------------------------------------------------------------
* Assume effective source is at center of vehicle since propagation is forward.
** Assume Z = 1.2.
X represents the distance from the source while Y is the distance from
the source to the microphones in SAE J2889-1. Z represents the height
of the microphone in meters specified in SAE J2889-1. The values in the
Table 11, above, were calculated using the formula below assuming a 1.2
meters value for Z.
[GRAPHIC] [TIFF OMITTED] TP14JA13.032
A critical factor for establishing a minimum sound for pedestrians
based on a desired detection distance is the ambient noise environment
in which the pedestrian is attempting to detect the vehicle. The agency
selected an ambient of 55 A-weighted dB to develop the minimum sound
level specifications. The agency choose an ambient sound pressure level
of 55 A-weighted dB because that is a level representative of a
moderate suburban ambient where pedestrians would be expected to be
able to detect vehicles based on hearing alone. In conversations with
the agency during Phase 1 research, visually-impaired individuals
indicated that in noisier suburban ambient conditions, they would not
try to cross streets unassisted. The ambient levels that the agency
measured during Phase 1 research for which visually-impaired
pedestrians would be expected to cross using hearing alone were 49.5 A-
weighted dB and 49.8 A-weighted dB.
In selecting an ambient at which the agency expects that
pedestrians should be able to detect an approaching vehicle using their
hearing, the agency relied on recommendations for quiet vehicle alert
sound specifications developed by Danish acoustics experts.\99\ In
developing the recommendations the Danish researchers measured
different ambient levels around Copenhagen. The ambient levels in
residential areas where pedestrians would be expected to detect an
approaching vehicle using their hearing was 55 A-weighted dB.
---------------------------------------------------------------------------
\99\ Pedersen et al. White Paper on External Sounds of Electric
Cars-Guidelines and Recommendations. Available at http://media.wix.com/ugd/64a49a_43313ad70e7c40f43150cf747b2e5c44.pdf?dn=A520040+-+DSTN+-+White+paper+electric+cars+-+av122410+-+ECT+LR.pdf.
---------------------------------------------------------------------------
In a presentation to NHTSA staff, Honda Motor Company (Honda)
stated that the ambient at which pedestrians would reasonably be able
to detect vehicles using hearing alone is around 52.5 A-weighted
dB.\100\ Honda based this conclusion on a human factors approach in
which recordings of three different ambient sound levels (quiet
residential, moderate suburban, and urban) were played and participants
were asked whether they would rely on hearing alone to detect an
approaching vehicle. While the study did not include any visually-
impaired participants, the agency agrees that pedestrians--those that
are visually impaired and others that are not--could not be reasonably
expected to detect approaching vehicles in ambient conditions near 60
A-weighted dB.
---------------------------------------------------------------------------
\100\ The Presentation that Honda gave at the meeting is
available on regulations.gov. Docket No. NHTSA-2011-0100-0038.
---------------------------------------------------------------------------
The agency believes that a 55 A-weighted dB ambient represents a
reasonable level below the 60 A-weighted dB ambient (in which
pedestrians would no longer be able to reasonably rely on hearing to
detect approaching vehicles).
The spectral distribution of the ambient is another factor that
affects the detectability of an alerting sound. Tonal components of an
alerting sound in portions of the ambient spectrum that are not strong
contribute to detectability. Using a loudness model and synthetic
ambient that represent a typical urban ambient profile in which a
pedestrian would be attempting to detect a vehicle, the agency
developed minimum sound level requirements for selected one-third
octave bands.
In order to aid pedestrian detection and recognition of sounds
produced by EVs and HVs, the agency has tentatively concluded that the
sound level produced by a vehicle will increase with an increase in
vehicle speed. The agency has two goals in increasing the vehicle's
sound level as the vehicle increases speed. First, increasing the
vehicle's sound level as the vehicle increases speed will allow
pedestrians to detect the vehicle from a greater distance to correspond
to the vehicle's increased sight stopping distance at higher speeds and
the greater distance necessary to stop the vehicle. Second, ICE
vehicles produce increasing sound levels as they accelerate so the
sound produced by HVs and EVs will mimic the behavior of ICE sounds to
enhance recognition.
In developing the acoustic specifications in this proposal, the
agency considered one-third octave bands from 160 Hz to 5000 Hz. When
all one-third octave bands from 160 Hz to 5000 Hz are set to a minimum
audible level, it can be demonstrated that, relative to the overall
sound level, some
[[Page 2831]]
bands are less efficient at providing a detectable signal. That is,
bands below 315 Hz and bands from 630 to 1600 Hz increase the overall
levels more for the same contribution to detection. The levels of these
bands are indicated by arrows in Figure 3. The arrows in the figure
point to the regions of the spectrum that are most effective for
warning sounds, i.e., those where the threshold is not too high and the
ambient is not too high to mask sounds at the threshold.
[GRAPHIC] [TIFF OMITTED] TP14JA13.033
Due to masking effects of the ambient and potential hearing loss of
the pedestrian, opportunities for detection will be maximized if the
countermeasure signal contains detectable components over a wide
frequency range; therefore, a minimum level is proposed for a set of
one-third octave bands that includes mid-frequency one-third octave
bands (315, 400, and 500 Hz) as well as high frequency one-third octave
bands (2000, 2500, 3150, 4000, and 5000 Hz). Low frequency bands (below
315 Hz) were not considered due to the expected strong masking effects
of the ambient at low frequencies. The agency chose these one-third
octave bands because these bands contributed the most to detection
without increasing the overall levels of the sound. Specifying minimum
sound pressure level requirements for a wide range of one-third octave
bands means that sounds meeting the specifications will be detected in
a wider range of ambient conditions with different acoustic profiles.
Specifications for the mid-range frequency bands between 315 and 500 Hz
will assist pedestrians in detecting HVs and EVs in ambient noise
environments such as areas near construction activity with a
significant degree of high frequency signal content. Low-frequency
bands (below 315 Hz) are omitted because they do not contribute to
detection and the likelihood that many practical countermeasure devices
may not be able to produce high level, low-frequency sounds.
In consideration of community noise impact, the agency omitted mid-
frequency bands from 630 to 1600 Hz from the acoustic specifications
because, for the ambient considered, these bands contributed more to
the overall sound level than other bands for the same increase in
detectability. By omitting minimum sound level requirements for the
one-third octave bands in the 630 to 1600 Hz frequency range, the
agency is able to ensure that the alert sounds allow pedestrians to
safely detect nearby EVs and HVs without contributing unnecessarily to
an increase in overall ambient noise levels.
Table 12 shows the one-third octave band frequency requirements for
vehicle emitted sounds for all of the test conditions in S7 of the
proposed regulatory text.
Table 12--Minimum Sound Levels for Detection
----------------------------------------------------------------------------------------------------------------
One-third octave band center Stationary but
frequency, Hz activated Backing 10 km/h 20 km/h 30 km/h
----------------------------------------------------------------------------------------------------------------
315............................. 42 45 48 54 59
400............................. 43 46 49 55 59
500............................. 43 46 49 56 60
2000............................ 42 45 48 54 58
2500............................ 39 42 45 51 56
[[Page 2832]]
3150............................ 37 40 43 49 53
4000............................ 34 36 39 46 50
5000............................ 31 34 37 43 48
Overall A-weighted SPL Measured 49 52 55 62 66
at SAE J2889-1 PP' line........
----------------------------------------------------------------------------------------------------------------
The agency is not including requirements for overall sound pressure
level in the proposed standard. Because each one-third octave band
contributes to the overall sound pressure level of a sound it is
possible to determine what the sound pressure level of sounds meeting
the requirements of Table 12 would be. The overall sound pressure level
of sounds meeting the requirements for each one-third octave band
listed in Table 12 would be 49 A-weighted dB when is in the stationary
condition, 52 A-weighted dB when backing, 55 A-weighted dB at 10 km/hr
(6 mph), 62 A-weighted dB at 20 km/hr (12 mph), and 66 A-weighted dB at
30 km/hr (18 mph).
The agency has tentatively concluded that the sound emitted by EVs
and HVs must meet the minimum sound pressure level requirements for
every one-third octave band listed in Table 12. The agency chose to
require sounds emitted by EVs and HVs to meet minimum sound pressure
level requirements for all of the one-third octave bands listed in
Table 12 because these one-third octave bands all contribute to
pedestrians' ability to detect these sounds. The agency realizes that
requiring HVs and EVs to emit sounds meeting the minimum sound level
requirements for every one-third octave band listed in Table 12 would
make these vehicles more detectable than current ICE vehicles for some
ambient noise environments. A majority of the ICE vehicles tested
during the agency's Phase 2 and Phase 3 research would not meet the
requirements in Table 12 for the one-third octave bands below 2000
Hz.\101\ While these vehicles did not meet all of the one-third octave
band specifications in Table 12, these vehicles were still considered
to be detectable under the agency's detection model. The agency's
detection model considers a vehicle to be detectable if it exceeds the
minimum sound pressure levels listed in Table 12 for any single one-
third octave band. A majority of the ICE vehicles tested by the agency
were detectable in at least two one-third octave bands for the 10 km/hr
(6 mph) pass by test. Even though the agency's detection model would
consider a vehicle to be detectable if it meets one of the one-third
octave bands levels in Table 12, requiring a sound to meet the minimum
levels in more than one one-third octave band increases the likelihood
that sound will be detectable in a wider range of ambient noise
conditions. The agency's detection model was created using a specific
ambient. While the ambient noise profile used with the agency's
detection model is typical of ambient environments in which pedestrians
would generally be attempting to detect HVs and EVs, requiring sounds
emitted by these vehicles to meet all the one-third octave bands in
Table 12 would increase the chance that these vehicles will be
detectable in ambient noise environments different from the one used in
the loudness model.
---------------------------------------------------------------------------
\101\ The agency notes that the acoustic specifications in Table
12 would not necessarily be an appropriate method for determining
whether ICE vehicles are detectable. While the agency intends this
proposal to be technology neutral, the agency recognizes that at
least for vehicles that are capable of electric only propulsion,
manufacturers will have to add some sound to the vehicle in order to
comply with this standard.
---------------------------------------------------------------------------
The fact that ICE vehicles also produce sound in one-third octave
bands outside those listed in Table 12--which may contribute to the
detectability of these vehicles--makes it difficult to compare sounds
produced by ICE vehicles with specifications for synthetic sounds to be
emitted by HVs and EVs. Because the sounds produced by ICE vehicles
include signal content in a far broader range of frequencies than
listed in Table 12, we believe the proposed minimum one third-octave
band requirements represent a reasonable approach to ensure that HVs
and EVs are at least as detectable as ICEs. The specifications in Table
12 were developed so that the synthetically generated sounds that
manufacturers add to vehicles to meet the requirements of this standard
would be detectable, recognizable, and would not contribute to noise
pollution.
The agency believes that requiring EVs and HVs to produce sounds
meeting the acoustic requirements in Table 12 will reduce the risk of
crashes between EVs and HVs and pedestrians to same risk level of
crashes between ICE vehicles and pedestrians. Numerous studies by motor
vehicle manufacturers and academics have found that sound, or lack
thereof, influences pedestrians' decisions about when to cross a
street. The agency's Phase 2 research showed that sounds with certain
acoustic characteristics were at least as detectable to the study
participants as the sound produced by ICE vehicles. Some studies have
shown that sounds designed using psychoacoustic principals are more
detectable than the sounds produced by ICE vehicles.\102\ To date no
studies have linked the increase in the detectability of a sound to a
reduction in the risk of crashes between EVs and HVs and pedestrians.
---------------------------------------------------------------------------
\102\ NHTSA-2011-0148-0025, available at www.regulations.gov.
---------------------------------------------------------------------------
The agency believes that sounds meeting the requirements in Table
12 will be as detectable as an ICE vehicle. If the sound produced by
EVs and HVs is detectable to pedestrians, they will be able to respond
to the presence of a vehicle thereby avoiding a collision. The agency
plans to conduct additional research before issuing a final rule to
confirm that sounds meeting the requirements in Table 12 will be
detectable at the distances predicted in the detection model. We seek
comment to improve the specifications in Table 12 to make the sounds
more detectable and to increase the effectiveness of the specifications
in reducing collisions between EVs and HVs and pedestrians.
Requiring EVs and HVs to emit sound meeting the minimum levels in
every one-third octave band in Table 12 will also enhance pedestrians'
ability to recognize the sounds emitted by EVs and HVs because
pedestrians associate low-frequency signal content with ICE vehicles.
For the reasons discussed above, as an alternative to requiring EVs
and HVs to meet the minimums for every one-third octave band listed in
Table 12 the agency seeks comment on requiring these vehicles to emit
sounds that meet only the one-third octave band requirements for 2000
Hz and above. The one-third octave band levels in
[[Page 2833]]
Table 12 represent a conservative approach, from a safety perspective,
to determining the sound level that an HV or EV would need to make in
order to allow a pedestrian to detect the vehicle from a desired safe
detection distance. Thus, it is possible that pedestrians may be able
to hear these vehicles at distances farther than predicted by the
agency's model. The agency plans to conduct additional research before
issuing a final rule to validate the assumptions relied upon in
determining the sound levels contained in Table 12. We are seeking
comment on the number of bands that should contain minimum sound level
requirements and what those minimum sound level requirements should be,
if the agency chooses to restrict the number of one-third bands for
which we would require a minimum sound pressure level. Along with
comments on the specifications in Table 12, the agency is seeking
recordings of sounds that manufacturers may wish to add to EV and HV
vehicles. The agency plans to analyze any recordings submitted in
response to this proposal along with other recordings made during
further research in finalizing the acoustic performance requirements
for the alert sound. For more information about submitting recordings
to the agency along with comments please see the instructions for
public participation in Section XII of this proposal.
The agency seeks comment of the possibility of allowing light
hybrid and electric vehicles to meet the minimum sound requirements for
the backing scenario with a beeping sound similar to the sound made by
a backing truck. The agency has yet to determine that a backup beeping
sound would be appropriate for light vehicles because this sound is
normally associated with backing heavy vehicles and thus many not be
recognizable as light motor vehicle. The agency also seeks comment on
whether such a sound would be annoying to the public.
The agency is also seeking comment on whether we should establish a
maximum sound level requirement in addition to the minimum sound level
requirements contained in this proposal. The PSEA directs NHTSA to
``consider the overall community noise impact'' of the specifications
contained in this proposal.\103\ One way that the agency could address
the overall community noise impact of this proposal would be to
establish maximum sound levels for hybrid and electric vehicles. We
seek comment on what the maximum levels should be were they to be
included in the final rule.
---------------------------------------------------------------------------
\103\ Public Law 111-373, Sec. 3(b)(3), 124 Stat. 4086 (2011).
---------------------------------------------------------------------------
The agency notes that motor vehicle manufacturers attempt to limit
the noise emissions of their vehicles in response to customer
preferences. The agency believes that manufacturers will limit the
sound output of hybrid and electric vehicles so as not to increase the
sound output of these vehicles beyond the minimum levels contained in
this proposal. The agency is hesitant to establish maximum sound levels
because we do not wish to increase the complexity of compliance with
the standard by establish tolerances that manufacturers must meet.
In October, 2012, representatives from Nissan Motor Co., Ltd.
(Nissan) presented results of the company's research to agency
rulemaking staff. Nissan conducted a survey to gauge costumer
acceptance of the sounds currently emitted by the Nissan Leaf. Nissan
also conducted a study to evaluate the detectability of different
sounds. Nissan interviewed blind pedestrians to ask them when they
believed a sound at idle would and would not be useful.
In November, 2012, Ford Motor Company (Ford) met with agency
rulemaking staff to present the results of human factors research
conducted by the company. The experiment included both blind and
sighted participants. During the experiment the participants were
presented recordings of various sounds approaching either from the
right or from the left. The participants were asked to identify when
they heard the sound and then asked to identify the direction from
which the sound was approaching. Ford compared the participants'
ability to detect the sounds to the detection distances discussed in
the agency's report on sound specifications for hybrid and electric
vehicles.\104\
---------------------------------------------------------------------------
\104\ See Hastings et al. (2012) ``Research on Minimum Sound
Specifications for Hybrid and Electric Vehicles.'' U.S. Dept. of
Transportation, Washington, DC. Available at Docket No. NHTSA-2011-
0148-0048.
---------------------------------------------------------------------------
2. Recognizability Requirements
The recognizability approach analyzes the sounds produced by ICE
vehicles and sets the acoustic requirements for HVs and EVs so that
they would contain acoustic characteristics similar to the sounds that
pedestrians associate with current ICE vehicles.
While the agency believes that the mid-range frequency
specifications in Table 12 will contribute to pedestrians' ability to
recognize the sounds as being produced by a motor vehicle, we believe
that the requirements for low-frequency broadband and low-frequency
tones in the agency's recognizability requirements adequately ensure
that pedestrians will be able to recognize these sounds. Further, the
low-frequency components in many ICE sounds may be masked by the
ambient level chosen for our model. However, this low-frequency content
contributes to recognition because it is associated with the sound
perceived by the pedestrian in lower ambients and that association is
remembered. Therefore, this low-frequency content does not need to be
detectable in every ambient to contribute to the recognizability of a
sound. Consistent with the assumption that ICE vehicles are
recognizable, low frequency content of alert sounds for HVs and EVs
does not need to be detectable in the 55 dB ambient to ensure that
these vehicles can be recognized by pedestrians.
Recognition includes two aspects: (1) recognition that the sound is
emanating from a motor vehicle that may pose a safety risk to the
pedestrian, and (2) recognition of the vehicle's operating mode
(acceleration, deceleration, constant speed, reverse or stationary but
activated) so that the pedestrian can take appropriate measures to
avoid a collision with the vehicle. Sounds that contain both broadband
noise and tones can produce sounds that are recognized as vehicles.
Sounds that contain only high frequencies have a synthetic (and
unpleasant) character. Sounds with lower frequency tones and noise
sound more like the sounds typically associated with a conventional
(ICE) motor vehicle.
While the one-third octave band requirements listed in Table 12
include some requirements for lower frequency signal content for
vehicle emitted sounds, low frequency tones are necessary to provide
additional cues to allow pedestrians to recognize these sounds. Tones
are not necessary to achieve a certain sound pressure level in a one-
third octave band. A vehicle-emitted sound would be able to meet a
minimum sound pressure level requirement for a one-third octave band if
it contained broadband noise at a high enough level. In addition to the
detectability requirements in Table 12, our proposal requires that the
lowest tone of the vehicle emitted sound must have a frequency not
greater than 400 Hz. Low-frequency tones are the tones that contribute
the most to recognizability so tones less than 2000 Hz contribute to
recognition while tones above 2000 Hz contribute to detection. ICE
vehicles produce low, mid, and high-frequency tones. The lowest
frequencies are related to the
[[Page 2834]]
combustion frequency of the engine. The low frequency components
contribute to the perceived power of the vehicle. Low-frequency tones
in simulated sounds will contribute the most to recognition because
these are closer in frequency to the low order harmonics of the engine
fundamental.
The agency is also proposing a general requirement for broadband
noise in the requirements designed to ensure that EV and HV emitted
sounds are recognizable. Sounds produced by current ICE vehicles are
broadband in nature, meaning that the sounds have some minimal signal
content across a wide part of the frequency spectrum. Also, it is
easier for a pedestrian to tell which direction a sound is coming from
if the sound contains broadband characteristics. (Broadband sounds are
also easier for pedestrians to localize than narrow band sounds.) In
order for sounds emitted by EVs and HVs to provide sufficient broadband
content to allow pedestrians to recognize these sounds as being
produced by a motor vehicle, the agency is proposing to require these
sounds to have some measurable content in each one-third octave band
from 160 Hz to 5000 Hz. This means that sounds emitted by EVs and HVs
are required to possess some acoustic signal content above 0 A-weighted
dB at all frequencies in the one-third octave bands between 160 Hz to
5000 Hz.
In the event that the agency decides to only require minimum sound
pressure levels in Table 12 for the one-third octave bands of 2000 Hz
and above, the agency would retain requirements for broadband signal
content in the one-third octave bands between 315 Hz and 500 Hz to
ensure that the sound retained aspects that contribute to
recognizability. In order to ensure that the sounds produced by EVs and
HVs are recognizable to pedestrians, the agency is proposing some
minimum low frequency signal content. In the event that the agency
decides to limit the requirements in Table 12 to one-third octave bands
above 2000 Hz, sounds produced by HVs and EVs would be required to emit
a sound with a sound pressure level of 30 A-weighted dB in the one-
third octave bands between 315 Hz and 500 Hz. The 30 A-weighted dB
level corresponds to the one-third band levels measured for a quiet
urban ambient during the agency's Phase 2 research. The agency would
not expect this signal content to be detectable in the 55 dB ambient;
it would only be present to assist pedestrians in recognizing the
sound. The agency seeks comment on the minimum sound pressure levels of
low frequency content that should be included in the agency's
recognizability requirements.
The agency recognizes that the speakers that manufacturers may wish
to use on EVs and HVs to meet the minimum sound requirements contained
in this proposal may not be able to produce tones as low as 160 Hz. The
agency believes that most of the speakers that manufacturers wish to
use will be capable of producing at least some signal content in the
160 Hz one-third octave band. The agency solicits comment on the issue
of whether speakers that manufacturers may wish to use to meet the
requirements of this proposal are capable of producing any measurable
signal content in the 160 Hz one-third octave band. The agency also
solicits comment on the cost of a speaker system that is able to
reproduce some measurable content at the 160 Hz one-third octave band
versus a speaker system that is only capable of producing sound above
315 Hz.
Pitch shifting is also a critical element to aid in pedestrian
recognition of vehicle sounds. Pitch shifting is the movement of the
tones of a sound along the frequency scale. Pitch shifting mimics the
behavior of an ICE vehicle as it increases speed. Based on analysis of
sounds produced by ICE vehicles the agency believes that the pitch of a
vehicle sound should increase with increasing vehicle speed, or
decrease with decreasing vehicle speed by at least one percent per km/
hr of vehicle speed.
3. Prohibition Against Modifying a Vehicle's Sound
The PSEA also requires that the FMVSS developed in this rulemaking
``prohibit manufacturers from providing any mechanism for anyone other
than the manufacturer or the dealer to disable, alter, replace, or
modify the sound or set of sounds, except * * * in order to remedy a
defect or non-compliance.'' Our proposal extends this prohibition to
any entity subject to NHTSA's authority (manufacturers, distributors,
dealers, and repair businesses), allows for repair of a vehicle
malfunction (in addition to the PSEA's defect and non-compliance), and
also prohibits any entity subject to our authority from providing the
means to defeat or change the sound emission to any other person,
except for repair of a malfunction associated with the vehicle's sound
emission. The goal of this section is to avoid the situation where
vehicle sounds are changed, at the request of the consumer, to
something individualized and no longer associated with the specific
make/model of motor vehicle, or indeed even recognizable as a motor
vehicle at all.
4. Phase-in Schedule
Lastly, the PSEA directs NHTSA to include a phase-in schedule for
compliance with the new FMVSS. ``The Secretary shall promulgate the
required motor vehicle safety standard pursuant to this subsection no
later than 36 months after the date of the enactment of this Act.'' The
Act further requires, at section 3(c), a phase-in period for
compliance, with full compliance of all motor vehicles subject to the
standard manufactured on or after the September 1 of the calendar year
that begins three years after the date of the final rule. For example,
if the final rule were issued on January 4, 2014, full compliance would
be required for all subject motor vehicles manufactured on or after
September 1, 2018. The maximum duration of the phase-in period would
therefore be January 4, 2014 through September 1, 2018. Vehicle model
years typically begin September 1, for example, the 2014 model year
will run from September 1, 2013 to August 31, 2014. In light of this
traditional production schedule, we tentatively conclude it would be
unreasonable to require manufacturers to build any vehicles to the new
FMVSS by September 1, 2014, for the 2015 model year, in this example.
However, most manufacturers are now involved in planning some form of
sound emission for vehicles they know will be affected by the new
standard. Changes to any sounds provided before the final rule date
will likely be made by software, not hardware, changes and
manufacturers will be familiar with the test procedure through the use
of the SAE J2889-1.
We therefore tentatively conclude that the following phase-in
schedule is reasonable for manufacturers and allows the fastest
implementation of the standard for pedestrian safety:
30 percent of the subject vehicles produced on or after September 1
of the first year of the phase in;
60 percent of the subject vehicles produced on or after September 1
of the second year of the phase in;
90 of the subject vehicles produced on or after September 1 of the
third year of the phase in; and
100 percent of all vehicles produced on or after, by September 1 of
the year that begins three years after the date that the final rule is
issued.
Small volume manufacturers will not need to comply with the
requirements of this proposal until the end of the phase-in period. We
seek comment on the appropriateness of this proposed schedule.
[[Page 2835]]
We have not included provisions for carry-forward credits in the
proposed regulatory text; however, we seek comment on allowing carry-
forward credits in the phase-in schedule to give manufacturers
flexibility in meeting the phase-in requirements.
E. Compliance Test Procedure
The compliance test procedure proposed in this notice is consistent
with the Society of Automotive Engineers Surface Vehicle Standard
J2889-1, ``Measurement of Minimum Noise Emitted by Road Vehicles,''
September 2011.\105\ Several sections of the SAE Standard are
incorporated by reference into our proposed FMVSS. This industry
standard was developed for use by manufacturers to test their own
vehicles. The compliance test procedure proposed by the agency must
deviate, however, in some respects so that it can be used by a third-
party testing entity with little or no detailed knowledge of all of the
vehicle's systems and their development.
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\105\ The agency recognizes that SAE published an updated
version of J2889-1 in May 2012. We have not yet evaluated this new
version, but intend to do so before publishing a final rule.
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Some particular differences between the SAE J2889-1 and our
proposed test procedure are:
This proposal is limited to outdoor testing, while the SAE
standard has an alternative for indoor testing.
The SAE procedure contains different methods for different
vehicle operating modes, and for vehicles fitted with external sound
generating systems versus vehicles without. Our proposal is uniform for
all vehicles and stated in technology neutral terms so that it can be
applied to any new motor vehicle to which the requirements in this
proposal would apply.
1. Test Condition
SAE J2889-1 paragraph 6.2 specifies the ambient weather conditions
under which the acoustics testing should be conducted. The ambient
weather conditions should be measured at the microphone height. SAE
J2889-1 specifies an ambient temperature between 5 degrees Celsius
([deg]C) (41 degrees Fahrenheit ([deg]F)) and 40 [deg]C (104 [deg]F).
The ambient weather conditions are restricted to ensure accurate
repeatable measurement. SAE J2889-1 states that the ambient temperature
may need to be restricted to a narrower temperature range so that all
key vehicle functions can be run in their quietest state per the
manufacturer's specifications.
The agency has found during the course of research conducted in
support of this rulemaking that tests that occur within the temperature
range specified in SAE J28889-1 can produce divergent results when a
vehicle is tested at different temperatures. In high ambient
temperatures, the battery cooling fan on pure electric vehicles
activates intermittently while the vehicle is operating. The agency has
decided to address the issue of intermittent vehicle sound caused by
the vehicle's battery cooling fan by requiring that any vehicle sound
measurements taken while the cooling fan is operating be discarded.
While the agency believes that it has addressed repeatability issues
caused by battery cooling fans, as stated in SAE J2889-1, it is
possible that there are other vehicle functions that produce varying
sound levels based on the ambient temperature level. Therefore, we are
soliciting comment on the other vehicle functions that produce varying
noise levels at different ambient noise levels. The agency is also
soliciting comment on specifying a low ambient temperature for
acoustics testing of between 5 [deg]C (41 [deg]F) and 20 [deg]C (68
[deg]F) to ensure that the vehicle will be in its quietest state during
testing. The disadvantage of doing so is that it further limits the
number of outdoor testing days available. The agency tentatively
concludes that we have sufficiently controlled this situation in the
test procedure by invalidating measurements in which any component of
the vehicle's thermal management system (i.e. a cooling pump or fan) is
engaged.
SAE J2889-1 test conditions specify a maximum wind speed of 5 m/s
(11 mph) because wind speeds higher than this level can interfere with
acoustic measurement. We have adopted this condition in our test
conditions.
SAE J2889-1 specifies that the ambient noise at the test site
should be measured for at least 10 seconds before and 10 seconds after
a series of vehicle tests. The measurements of the minimum A-weighted
sound pressure level and one-third octave band frequency content of the
ambient noise level are made using the same microphones in the same
locations used to measure the vehicle sound as specified in Figure 1 of
SAE J2889-1.
It is important to know the background noise level during the test
to get an accurate measurement of the sound made by the vehicle alone.
Because we are proposing requirements on the one-third octave band
basis we believe that ambient corrections should also be calculated on
the one-third octave band basis. In order to ensure accurate
measurements SAE J2889-1 contains a procedure for correcting the
overall sound pressure level measurement to remove any ambient
influences. It is important to know the background noise level during
the test to get an accurate measurement of the sound made by the
vehicle alone. Because we are proposing requirements on a one-third
octave band basis we believe that ambient corrections should also be
calculated on a one-third octave band basis. In order to ensure
accurate measurements, SAE J2889-1 contains a procedure for correcting
the overall sound pressure level measurement to account for ambient
influences. Because the variance of a signal is greater on a one-third
octave band basis than on the overall, it may be difficult to apply the
ambient correction procedure in SAE J2889-1 to ambient corrections on a
one-third octave band basis. SAE J2889-1 requires a peak-to-peak
variation of less than two dB in order to do a valid correction. Even
if the peak fluctuation of the overall sound pressure level of the
ambient is less than two dB, the fluctuation in individual one-third
octave bands would likely be higher. In meetings with agency rulemaking
staff, manufacturers have stated that it would be difficult to apply
the method for correcting for the ambient in SAE J2889-1 to one-third
octave bands.
In response to these concerns we are proposing to include a
procedure that allows for ambient correction if the peek-to-peek
fluctuation of the ambient is less than eight dB when the signal that
is being measured is more than six dB higher than the ambient in that
one-third octave band or less than six dB when the signal that is being
measured is more than three dB higher than the ambient in that one-
third octave band. These criteria were chosen in order to provide a
high degree of confidence that contamination due to an unobserved,
random fluctuation will not impact the final reported level by more
than one half of one decibel.
We believe that increasing the acceptable peak-to-peak variability
in the ambient correction procedure will allow for testing to be
conducted in ambient sound environments in which the agency would
expect to be able to make accurate measurements. We believe that this
approach will increase flexibility in the locations and times when
outdoor testing can be conducted without significantly compromising the
accuracy of measurements.
In October of 2012, members of the SAE VSP committee presented
research to the agency regarding the use of the test procedures in SAE
2889-1 and issues related to correcting for the influence of the
ambient in measurements on the one-third octave band basis. The VSP
committee also
[[Page 2836]]
raised issues regarding measuring pitch shifting and the influence of
ambient noise and tire noise on pitch shifting measurements. Members of
the VSP committee stated that analyzing pitch shifting measurements
will require a narrowband analysis. The VSP committee stated that the
procedure for correcting measurements of the overall sound pressure
level of a signal for the influence of ambient should not be applied to
measurements of individual one-third octave bands. The VSP committee
stated that outdoor testing raised issues regarding interference with
measurements by the ambient. Members of the VSP committee also
expressed concern that manufacturers would not be able to sufficiently
attenuate the low frequency tones discussed in the agency's research to
prevent those tones from intruding into the occupant compartment.
Members of the VSP committee stated that pass-by measurements at 20 km/
h (12 mph) and 30 km/h (18 mph) are influenced by tire noise. Members
of the VSP committee believe that issues related to the influence of
ambient noise on measurements of the vehicle and issues related to
measuring pitch shifting can be solved by the use of indoor testing to
measure regulatory compliance. We seek comment on the points raised by
the VSP Committee.
The agency is considering whether the procedures for analyzing the
frequency spectrum in SAE J2889-1 are sufficient to ensure that the
results of the acoustic measurements are recorded in a consistent
manner. The agency has the following questions about the measurement
correction procedure and the recording of results of acoustic
measurements:
What roll-off rates have been used?
Have entities conducting research on minimum sound emitted
by quiet vehicles completed the \1/3\ octave band analysis of their
measurements in the frequency domain or the time domain?
Volpe staff have been using an exponential window (to be
consistent with SAE procedures for the measurement of overall levels)
when conducting frequency analysis. In the presentation by VSP
committee a committee member discussed using a Hanning window for the
analysis. Does the agency need to provide additional procedures for
conducting the one-third octave band analysis?
The agency has tentatively concluded that outdoor acoustics testing
is preferable to indoor testing in hemi-anechoic chambers. Outdoor
testing is more representative of real world vehicle-to-pedestrian
interactions. Also, the agency is concerned about both the availability
of repeatable specifications for all aspects of indoor testing and the
availability of hemi-anechoic chambers in which to conduct compliance
testing.
Outdoor tests, especially pass-by tests at speed, transmit to the
pedestrian not just vehicle-generated sounds (e.g., engine-powertrain
and pedestrian alert system), but also sounds from the vehicle body's
interaction with the atmosphere (wind noise) and road test surface
(tire noise). These complete sound profiles are transmitted to the
pedestrian over some level of ``outdoor ambient'' background noise and
with Doppler shift when the vehicle is moving relative to the
pedestrian. Pass-by tests allow a recording of vehicle sound parameters
(levels, content, phase, etc.) against a trace of time and distance
from the pedestrian's location.
Conversely, when a vehicle is tested on an indoor dynamometer in a
hemi-anechoic chamber, the body of the vehicle is static and does not
produce aerodynamic noise. It is unclear how representative the tire
noise generated during rotation on the curved dynamometer test wheels
is of actual tire-road noise. The vehicle approach and passing of the
microphones can be simulated by phasing a row of microphones next to
the vehicle, and interior tire noise can be digitally replaced with
exterior tire noise recordings. However, the agency has not determined
the fidelity of such methods.\106\
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\106\ http://www.bksv.com/Products/PULSEAnalyzerPlatform/PULSESolutionsOverview/AcousticApplications/PassbyNoiseTesting/IndoorPassbyNoiseTesting.aspx.
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The agency also believes that specifications for outdoor testing
have a more detailed history of objective and repeatable performance
than specifications for indoor testing. A substantial amount of
development and refinement has gone into the test procedures and
facilities used for outdoor vehicle noise testing. For instance,
outdoor tests such as the ISO 362 ``Acoustics Measurement of noise
emitted by accelerating road vehicles--Engineering method'' \107\ have
been in use since its issuance in 1994 for measurement of maximum
vehicle noise. One key to achieving repeatable test results with ISO
362 at multiple testing locations was the standardization of a common
road test surface. The 1994 and subsequent versions of ISO 10844
``Acoustics--Specification of test tracks for measuring noise emitted
by road vehicles and their tyres'' \108\ specify test surface
materials, absorption, texture, and compaction to allow comparable test
results from different outdoor noise test pads.
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\107\ http://www.iso.org/iso/iso_catalogue/catalogue_ics/catalogue_detail_ics.htm?csnumber=25971.
\108\ http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=45358.
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SAE J2889-1 contains specifications on the cut-off frequency of the
indoor hemi-anechoic test facility and requirements to meet ISO 3745
``Acoustics--Determination of sound power levels of noise sources using
sound pressure--Precision methods for anechoic and hemi-anechoic
rooms,'' or ISO 26101 ``Acoustics--Test methods for the qualification
of free-field environments.'' However, the agency is not aware of
specifications for dynamometer drum surface textures, materials,
diameters, road loads coefficients (i.e., to produce appropriate engine
RPMs), etc. to allow comparable results between different indoor
dynamometers.
The agency intends to specify performance requirements for vehicle-
emitted sounds that are detectable and recognizable to a pedestrian as
a motor vehicle in operation. Therefore, all components of the
vehicles' sound profile that convey the signature of a motor vehicle in
operation (including aerodynamic and tire noise) up to the cross-over
speed are important facets of the vehicle's sound performance.
The agency is concerned that hemi-anechoic chambers that have four-
wheel dynamometer drive capabilities are not widely available for
commercial testing. The agency was able to locate a large number of
outdoor 10844 noise pads in the U.S., most of which were available for
paid use by outside parties. One vehicle manufacturer stated that it
has nine noise pads throughout its global operations and we believe the
standardized outdoor noise pads have widespread commercial
availability.
The agency found limited availability of indoor hemi-anechoic
chambers that had four-wheel dynamometer drive capabilities.
Additionally, the availability of indoor hemi-anechoic dynamometer
chambers that can accommodate all motor vehicles covered by the PSEA,
such as motorcycles, trucks, buses, etc., was found to be far more
limited. While indoor testing does not have the seasonal downtimes of
some outdoor test facilities, and may be more predictable and time
efficient, we believe the cost of test time at indoor test facilities
will be higher than at outdoor proving ground noise pads. There may
also be difficulties locating
[[Page 2837]]
and scheduling indoor facilities large enough to accommodate the heavy
vehicles subject to this rule.
In addition to conducting indoor testing in a hemi-anechoic chamber
using a dynamometer to simulate vehicle motion, it is possible to
conduct pass-by testing in an indoor hemi-anechoic chamber. Indoor
pass-by testing in a hemi-anechoic chamber would capture elements of
the vehicle sound profile (including aerodynamic and tire noise) that
contribute to the recognizability of the vehicle's sound signature
until the vehicle reaches the cross over speed. Therefore, indoor pass-
by testing in a hemi-anechoic chamber is able to record all aspects of
the vehicle's sound profile while still achieving the convenience and
efficiency advantages of indoor testing. An indoor pass-by procedure
would be the same as the pass-by procedure contained in Section 7.3.2.2
of SAE J2889-1 SEP2011 except that 50 meter radius free of reflecting
objects around the test track would not apply. The provision in SAE
J2889-1 SEP2011 that the hemi-anechoic chamber used for indoor pass-by
testing comply with ISO 3745 or ISO 26101 would ensure that reflection
from the test would not interfere with the vehicle's sound measurement.
The agency is not aware of the availability of hemi-anechoic
chambers that are large enough to accommodate indoor pass-by tests. The
agency believes that the existence of such facilities is limited. The
agency seeks comment on the availability of hemi-anechoic facilities
that could accommodate indoor pass-by testing and the desirability of
including a test procedure for indoor pass-by testing in this standard.
The agency realizes that there are some advantages to testing
indoors. Testing in an indoor hemi-anechoic chamber would not be
influenced by weather conditions or high ambient noise levels that can
affect outdoor pass-by testing. It is possible that indoor testing
could be more predictable and time efficient than outdoor pass-by
testing because testing time would not be limited by weather and noise
conditions at the test site. The agency seeks comment on including a
test procedure for indoor hemi-anechoic chamber acoustics measurement
in this standard.
The agency's test procedure specifies that the acoustic
measurements for all test conditions shall be conducted on a test
surface that meets the requirements of ISO 10844:2011 which specifies,
among other things, a very particular type of pavement to be used so as
to minimize the contribution of tire noise to the sound measured as
coming from the vehicle. Doing so helps to minimize test variability
between repeat tests of the same vehicle at the same facility and
variations in measurements taken at different facilities.
Instruments used to make the acoustical measurements required under
our proposal must meet the requirements of paragraph 5.1 of SAE J2889-
1. This paragraph also describes procedures for calibration of the
acoustical equipment. Use of such instruments and calibration
procedures will ensure that test measurements can be duplicated
repeatedly on the same vehicle at one facility, or at different test
facilities. Manufacturers, in meetings with agency rulemaking staff,
have stated that the filter roll-off rate can affect the results of
acoustic measurement at the one-third octave band level. Paragraph
7.1.6.2 of SAE J2889-1 requires conformance with ANSI S1.11, which
specifies a wide range for filter roll-off rates. (See ANSI S1.11
Table1, Figure 1, and Annex B.) Filters with roll-off rates at the two
extremes of the range could produce different results. The agency seeks
comment on whether the test procedure in this proposal should specify a
maximum roll-off rate that is not infinite.
The test site envisioned by our proposal must be established per
the requirements of S6.1.1 of SAE J2889-1, including Figure 1, ``Test
Site Dimensions'' with the definitions of the abbreviations in Figure 1
as given in Table 1, S4 of SAE J2889-1. All references to microphone
line PP' and vehicle centerline CC' are per Figure 1 of SAE J2889-1.
Microphones are to be set on the PP' line on both sides of the vehicle,
two meters from the vehicle centerline (CC'). Use of the test set up
described in the SAE's Figure 1 will ensure repeatable test
measurements from run to run, vehicle to vehicle, and among various
test facilities.
2. Vehicle Condition
The agency's goal in measuring the vehicle's sound level in the
test procedure is to measure the vehicle at its quiet state. The test
procedure in the agency's proposal contains a specification for vehicle
condition to ensure that there is no variability in the results of the
acoustics testing and that the vehicle will be tested at its quietest
state. The vehicle condition specifications state that the tires should
be pressurized per the tire placard and conditioned by driving,
clockwise and counterclockwise, around a circle 30 meters (100 feet) in
diameter at a speed that produces a lateral acceleration of
approximately 0.5 to 0.6 g. This removes mold sheen from new tires. The
SAE J2889-1 test procedure used in our research has a further
requirement that tires have at least 80 percent of their tread depth.
NHTSA has not included such a requirement because we are proposing that
only new vehicles with less than 100 miles on their odometers at the
start of testing be used. This is the normal agency protocol for
compliance testing in general. The vehicle condition specifications
also state that the tire treads should be free of debris, because
pebbles and other objects in the vehicle's tire tread can produce a
clicking sound that can increase the vehicle's sound level and
interfere with acoustics measurements during pass by testing.
The vehicle test condition states that all doors should be shut and
locked before commencement of testing. This step is included in the
proposed vehicle condition specifications because some vehicles are
equipped with automatic locks that lock the vehicle once the vehicle
reaches a certain speed. The sound produced by the locking doors can
introduce variability into the test results.
The proposed vehicle test condition specifies that all the
accessory equipment on the vehicle should be turned off. This step is
included because the vehicle's air conditioning system, heating system,
and windshield wipers can all produce sound when activated that can
introduce variability into the acoustic measurements in S7 of the
proposed regulatory text.
The agency wishes to measure the sound produced by the vehicle with
the ICE off because we are attempting to measure the sound of HVs and
EVs in those vehicles' quietest states. This proposal is designed to
ensure that these vehicles emit a minimum level of sound in situations
in which the vehicle is operating in electric mode because in that mode
the vehicle did not provide sufficient sound cues for pedestrians.
Therefore, we propose to control the situation in which an ICE engine
does start operating during a test by invalidating test measurements
that are taken when a vehicle's ICE is operating. The proposed test
procedure states when testing a hybrid vehicle with an ICE that runs
intermittently, measurements that contain sounds emitted by the ICE are
not considered valid.
As discussed below, the agency is not requiring that HVs meet the
requirements of this proposal for a given operating condition if they
are not capable of operating in EV only mode in
[[Page 2838]]
that condition. The agency's method for determining whether a vehicle
is incapable of operating in EV mode above a certain speed requires
that the batteries on the vehicle be fully charged at the beginning of
the test sequence; otherwise the vehicle may be improperly exempted
from meeting the requirements for a given condition. The agency
believes that the hybrid vehicles to which this proposal would apply
are equipped with an indicator that provides information on the state
of charge of the propulsion batteries. The agency is also considering
adding a vehicle charging procedure to charge the vehicle's propulsion
batteries prior to each test sequence. This procedure would involve a
set of vehicle maneuvers designed to charge the vehicle propulsion
batteries. The agency seeks comment on whether there are HVs to which
this proposal would apply that do not visually indicate their
propulsion batteries state of charge to the driver. The agency also
seeks comment on whether a battery charging procedure should added to
the test procedure.
3. Test Procedure
The agency proposal contains steps for measuring the sound of the
vehicle at startup, stationary but activated, reverse, 10 km/h (6 mph)
pass by, 20 km/h (12 mph) pass by and 30 km/h (18 mph) pass by. The
agency has tentatively concluded that EVs and HVs should produce a
minimum sound at least until they reach a speed of 30 km/h (18 mph).
The PSEA defines crossover speed as the ``speed at which tire noise,
wind resistance, or other factors eliminate the need for a separate
alert sound.'' \109\ Because we intend for the proposed standard to be
technology neutral, we are not including a requirement for when an
alert sound added to a vehicle must be active in the regulatory text.
Instead, the proposed standard includes required minimum sound pressure
levels that vehicles subject to the standard are required to meet at
different test speeds so that these vehicles will make sufficient sound
to allow pedestrians to detect them.
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\109\ Public Law 111-373, Sec. 2(3), 124 Stat. 4086 (2011).
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The agency established the proposed top crossover of 30 km/hr (18
mph) by examining the speed at which EVs and HVs produce a similar
amount of sound to their peer ICE vehicles. In comparing the sound
produced by HVs and EVs to the sound produced by ICE vehicles, the
agency sought to determine the speed at which the ICE was no longer the
dominant sound source of the vehicle and tire and wind noise were the
main source of vehicle sound output. We also examined the crash
statistics from the State Data System to determine if there was a speed
at which the rate of pedestrian crashes for HVs and ICE vehicles were
the same.
NHTSA's research indicates that the speed at which the sound levels
produced by HVs and EVs and the sound levels produced by those
vehicles' ICE peers become indistinguishable differs depending on make
and model. The difference in sound pressure level between sounds is not
distinguishable to humans over time if the sounds are within 3 A-
weighted dB of each other.\110\ The sound level of three of the HVs
tested during the agency's Phase 1 research were within 3 A-weighted dB
of their ICE peer vehicles at 16 km/h (10 mph) with the sound levels
for all HVs meeting those of their peer ICE vehicles at 32 km/h (20
mph).
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\110\ Springer Handbook of Acoustics, Thomas D. Rossing (Ed.),
Springer Science and Media LLC, New York, 2007, page 472.
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During the agency's Phase 3 research, an EV (Nissan Leaf) and three
HVs with prototype sound systems and their ICE peer vehicles were
tested to compare the sound levels of HVs and EVs and their ICE peers
when stationary but activated, 10 km/h (6 mph), 20 km/h (12 mph), and
30 km/h (18 mph).\111\ Only one of the HVs tested during the Phase 3
research was within 3 A-weighted dB of its ICE peer at 20 km/h (12
mph), the same hybrid produced a sound level 3.5 A-weighted dB above
its ICE peer at 30 km/h (18 mph). The sound level produced by the
Nissan Leaf was 5 A-weighted dB lower than its ICE peer, the Nissan
Versa, at 20 km/h (12 mph) and 4 A-weighted dB lower than the Versa at
30 km/h (18 mph) with its sound generation system turned off. The other
HV tested was 5 A-weighted dB lower than its ICE peer at 20 km/h (12
mph) and 4 A-weighted dB lower than its ICE peer vehicle at 30 km/h (18
mph). The sound levels produced by the Nissan Leaf and the HVs were not
as high as the overall levels of sounds that would meet the proposed
requirements for every one-third octave band listed in Table 12 at 20
km/h (12 mph) (see Table 12). Both HVs produced sound levels as high as
sounds meeting the requirements for every one-third octave band in
Table 12 at 30 km/h (18 mph) and the Nissan Leaf produced a sound only
2 A-weighted dB lower.
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\111\ One of the HVs tested during the Phase 3 research was
excluded from the crossover speed analysis because the agency was
not able to deactivate the vehicle's sound alert system. Because the
sound alert system on that vehicle remained active the agency was
not able to compare the sound level of the vehicle while operating
in electric mode to sound level emitted by the vehicle's ICE peer.
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The acoustic measurements for the agency's Phase 3 research were
conducted on a test surface conforming to ISO 10844 (1998) and acoustic
measurements conducted during Phase 1 research were taken on the VRTC
test track which does not conform to ISO 10844 (1998). Even though the
Phase 1 and Phase 3 measurements were taken on different surfaces the
direct comparison between the EV or HV and its ICE peer remains valid,
as EVs and HVs were measured on the same test surface as their
respective ICE peer vehicles.
Our research data from Phase 1 and Phase 3 shows that the sound
level gap between HVs or EVs and their ICE peer vehicles still exists
at 20 km/hr (12 mph) and becomes much smaller or negligible in some
tests at 30 km/hr (18 mph). Also, the EVs and HVs tested in Phase 3
research did not meet our minimum sound pressure level detectability
requirements at 20 km/hr (12 mph). For these reasons, NHTSA tentatively
concludes that ensuring EVs and HVs produce a minimum sound level until
they reach a speed of 30 km/hr (18 mph) will ensure that these vehicles
produce sufficient sound to allow pedestrians to detect them. The
agency believes that the minimum sound level requirements will ensure
that these vehicles produce sufficient sound to allow for safe
pedestrian detection at this speed. Thus, the requirements in this
proposal, if made final, would require that EVs or HVs that do not
currently produce enough sound for pedestrians to detect them while
traveling at 30 km/hr (18 mph) would have to increase their sound
output. The agency solicits comments on the determination of 30 km/hr
(18 mph) as the appropriate upper limit for light EVs/HVs and
additional data on similar tests performed on the same type of
vehicles.
At speeds greater than 30 km/hr (18 mph), the agency has
tentatively concluded that EVs and HVs produce sufficient sound for
safe pedestrian detection. The agency believes that vehicles that will
require a countermeasure sound to meet the minimum sound requirements
at 30 km/hr (18 mph) will continue to produce those countermeasure
sounds at higher speeds so that the added sound will phase out at
speeds greater than the crossover speed. The agency believes that
manufacturers are likely to gradually phase the countermeasure sound
off at speeds above the crossover
[[Page 2839]]
speed to avoid annoyance caused by a sharp drop in sound level if the
countermeasure was terminated exactly at 30 km/hr (18 mph).
The crashes used in our statistical analysis discussed earlier came
from areas where the posted speed limit was less than or equal to 35
mph. As discussed previously, this analysis indicated that the odds
ratio of an HV being involved in a crash with a pedestrian was 1.38
when the vehicle in question completed a low speed maneuver immediately
prior to the crash.\112\ This means that HVs and EVs were 38 percent
more likely to be involved in an incident with a pedestrian than an ICE
vehicle under these circumstances. Low-speed maneuvers include making a
turn, slowing or stopping, backing, entering or leaving a parking space
or driveway, and starting in traffic. The agency also tentatively
concludes that a crossover speed of 30 km/hr (18 mph) will ensure that
EVs and HVs will produce sufficient sound to allow pedestrians to
safely detect them during low-speed maneuvers in which these vehicles
would otherwise pose a risk to pedestrians because of the low sound
level they produce. The odds ratio of a HV being involved in a
pedestrian crash while going straight is 0.96. This means that HVs are
no more likely to be involved in pedestrian crashes when going straight
than ICE vehicles.
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\112\ See footnote 36.
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The agency does not believe that establishing a crossover speed of
30 km/h will have any noticeable impact on ambient noise levels. As
discussed in Section X.D, NHTSA has conducted an EA to analysis the
environmental effects of this rulemaking. The EA shows that the
difference in ambient sound levels if the agency were to establish a
crossover speed of 30 km/h compared to a crossover speed of 20 km/h
would be negligible. A single EV or HV travelling at 30 km/h that
produced sound meeting the requirements of this proposal would not be
noticeable to a person standing 7.5 meters from the roadway in a 55 A-
weighted dB ambient environment representative of urban areas.
The guidance document developed by UNECE recommends that EVs and
HVs emit pedestrian alert sounds beginning when the vehicle starts
moving and continuing until the speed of the vehicle reaches 20 km/hr
(12 mph). The Alliance of Automobile Manufacturers also suggested 20
km/hr (12 mph) as the crossover speed.\113\
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\113\ http://www.regulations.gov/#!documentDetail;D=NHTSA-2011-
0148-0022.
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During QRTV's eighth meeting, the Japan Automobile Standards
Internationalization Center (JASIC) presented its research on crossover
speed.\114\ It determined the crossover speed by measuring when the
tire noise was dominant over engine noise for several vehicles. JASIC
concluded that the tire noise was dominant for every ICE vehicle and HV
they tested at speeds that exceeded 20 km/h (12 mph). It also concluded
that the difference between sound levels of HVs and ICEs occurred at
speeds below 20 km/h (12 mph). The agency solicits comments on whether
20 km/h (12 mph) should be considered the crossover speed, as an
alternative to the 30 km/h (18 mph) crossover speed as well as
additional research data that support this speed.
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\114\ http://www.unece.org/trans/main/wp29/wp29wgs/wp29grb/qrtv_8.html.
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In the absence of more detailed analysis supporting another
crossover speed, the agency tentatively concludes that a crossover
speed of 30 km/hr (18 mph) will ensure that pedestrians will be able to
safely detect EVs and HVs in situations in which these vehicles pose an
increased risk to pedestrians because of their quiet nature while also
minimizing community noise impact by ensuring that the sound is not
active when it is no longer necessary.
In order to ensure that HVs and EVs produce a minimum level of
sound to be detectable by pedestrians until the crossover speed, the
agency is proposing to measure the minimum sound of the vehicle at 30
km/hr (18 mph). Because the agency's proposal is technology neutral, a
manufacturer can choose how to comply with the minimum level sound
requirements at the 30 km/hr (18 mph) pass by. Thus, no countermeasure
sound would be required if a vehicle subject to the requirements of
this standard produces sound sufficient to meet the requirements in
section S5 of our proposed regulatory text at 30 km/hr (18 mph).
For all operating conditions, our proposed test procedure (and that
of SAE J2889-1) specifies that four consecutive valid measurements be
within 2 A-weighted dB. This repetition and decibel level restriction
are to ensure repeatability of vehicle sounds without the presence of
unwanted ambient spikes, other non-vehicle sounds, or intermittent
sounds the vehicle may happen to make that are not associated with its
normal operating sound.
The test procedure also specifies that test runs in which the
vehicle's ICE, (for HVs), or battery cooling system activate must be
discarded. As stated earlier, it is the agency's goal to measure the
minimum sound levels of vehicles subject to this standard in their
quietest state. It is because these vehicles are capable of very quiet
operation that the agency is requiring a minimum sound level to ensure
pedestrians can detect them.
The agency also found that a hybrid vehicle's ICE engine turning on
during the test can introduce variability into the test results. The
agency has no preference in how manufacturers choose to comply with the
minimum sound level requirements in this standard. If the agency could
rely on battery cooling fans on pure electric vehicles or the ICE
engines on hybrid vehicles to be activated whenever the vehicle is
turned on or moving this would be a satisfactory manner for a
manufacturer to comply with the minimum sound level requirements. The
fact that both the battery cooling fans and the ICEs on hybrid-
electrics are only running intermittently means that sounds produced by
these vehicle functions cannot be relied on to provide sound to
pedestrians under all conditions. While the specifications requiring
four valid measurements with 2 A-weighted dB would to some extent
address repeatability issues caused by intermittent vehicle noise, the
agency wants to guard against a situation in which measurements are
accepted with the battery cooling fans active on an EV or the ICE
engaged on a hybrid-electric.
The agency realizes that it may be possible that not all the HVs to
which this proposal would apply are designed to be operated in EV only
mode for every operating condition for which this proposal would
specify requirements. Because the agency would be testing HVs in their
quietest state, the test procedure and requirements in this proposal
are not designed to test a vehicle that is producing added sound while
its ICE is operating. Therefore, the agency would not require that HVs
meet the requirements of this proposal for a given operating condition
if they are not capable of operating in EV only mode in that condition.
For example, if a vehicle is not designed to operate in EV only mode
above 25 km/h it would not be required to meet the requirements in this
proposal at any speed above that (e.g. at the typical 30 km/h crossover
speed).
The test procedure in S7 calls for 4 valid consecutive measurements
and tests in which the vehicle's ICE is running are not considered
valid. Thus, according to these test procedure, it would not be
possible to test vehicles that do not operate in EV only mode in one of
the conditions for which we are
[[Page 2840]]
proposing minimum sound requirements. Therefore, we have included a
provision in the proposal that excludes an HV from meeting the minimum
sound requirement for a given operating condition after 10 consecutive
tests during which the vehicle's ICE is on for the entire test.
a. Start-Up
The proposed regulatory text in Section XIII of this notice would
require that the vehicle's stationary but activated sound commence
within 500 milliseconds of when the vehicle's starting system engages.
The proposal does not currently contain specifications for a separate
``start-up'' sound. The requirement that the stationary but activated
sound commence within 500 milliseconds of when the vehicle's starting
system engages establishes how soon the vehicle must meet the
requirements of the proposal after it is turned on. The agency believes
it is important for the pedestrian to be aware of a vehicle as soon as
its starting system is activated. We believe 500 milliseconds is
adequate time for the vehicle's starting system to engage after the
driver has initialized the process by whatever method is used on that
vehicle (i.e., turning a key or pressing a button) and for the staring
system to communicate with other vehicle systems. We seek comment on
whether 500 milliseconds is a sufficient amount of time for the alert
sound to activate after the vehicle's starting system is engaged. We
also seek comment on whether 500 milliseconds is an appropriate amount
of for the alert sound to activate after the vehicle's staring system
is engaged from a safety prospective.
While the agency has not included separate acoustic requirements in
Section XIII to signal that the driver has turned on the vehicle, the
agency is considering whether we should include such requirements in
the final rule. If the agency decides to include a different acoustic
cue to signal that the driver started the vehicle, we would require
that the sound start within 500 milliseconds of the driver initializing
the starting process and continue for two seconds. The sound pressure
levels that the agency measured for vehicle starting sounds during the
Phase 2 research were between 65 A-weighted dB and 75 A-weighted dB.
The startup sounds that the agency measured during the Phase 2 research
were 11 A-weighted dB to 15 A-weighted dB louder than the sound
produced by those vehicles when stationary but activated. The agency
recognizes that a start-up sound of 75 A-weighted dB is probably higher
than necessary to alert pedestrians to the presence of a starting
vehicle. Were the agency to require a different start-up sound, the
agency would want the difference between the start-up sound and the
sound produced by the vehicle when stationary but activated to mirror
the difference in sound pressure levels between stationary but
activated and start-up in ICE vehicles so that a pedestrian would be
able to differentiate between the two operating conditions. Thus, a
start-up sound for HVs and EVs would be 11 to 15 A-weighted dB higher
than the requirements proposed for stationary but activated in Section
XIII (see Table 1, S5.1.1 of the proposed regulatory text). The agency
solicits comments on whether a start-up sound should be included as an
operating condition for which the agency should establish minimum sound
requirements as well as the acoustic requirements that are different
from the requirements for the stationary but activated sound.
The microphone position for the start-up sound test is the same as
the microphone position for the stationary but activated condition test
described below.
b. Stationary But Activated and Directivity
The test procedure used to measure the compliance of the vehicle to
the startup, stationary but activated, and directivity requirements of
Section 5 of the proposed regulatory text is based on the ``stopped
condition'' test of paragraph 7.3.2.1 of SAE J2889-1. The front plane
of the vehicle is positioned at the microphone line (PP'), the vehicle
is stationary and four consecutive 10 second measurements are taken.
Measurements are considered invalid if they contain sounds emitted by
any component of the vehicle's battery thermal management system
(cooling fans or pumps), or they come from an ICE on an HV equipped
with an ICE that runs intermittently. These provisions help to ensure
that the vehicle is measured in its quietest state. The pass/fail
requirements for this test, as for all the tests, are a set of sound
pressure level measurements in each of eight one-third octave bands,
which were chosen for their ability to contribute to detectability
without unnecessarily adding to the overall sound pressure level of the
vehicle in that condition.
The agency is proposing that the vehicle be tested for minimum
sound level at the stationary but activated operating condition with
the vehicle's gear selection in park (for vehicles fitted with a park
position). The agency has decided to test at the stationary but
activated condition while the vehicle is first turned on and while the
vehicle is in park instead of testing while the vehicle's gear
selection is in drive because the agency believes that the vehicle must
produce a sound level while at park that is sufficient to allow
pedestrians to avoid collisions with vehicles pulling out of parking
spaces and driveways. The agency believes that the alert sound
activating when the vehicle is shifted into drive will provide
insufficient warning of the presence of a vehicle that is about to pull
out of a parking space or a driveway. It is likely that drivers will
shift into drive and commence vehicle motion with minimal delay. In
this situation, an alert sound that activated when the vehicle was
shifted into drive would provide little to no warning that there was a
nearby vehicle. The agency believes that testing the vehicle's minimum
sound level while in drive would reduce the effectiveness of the
requirement of a sound when stationary but activated and testing the
vehicle's sound level while the vehicle is in park will decrease the
number of collisions between EVs and HVs and pedestrians caused by the
vehicle's quietness.
In an email to the Director of the Office Crash Avoidance Standards
the NFB expressed concern that establish minimum sound requirements for
when the vehicle's gear selection was in drive but not in park would
mean that blind and visually impaired pedestrians would not be able to
detect the presence of nearby vehicles that had just been turned on in
``a parking space, driveway, or other location.'' \115\ Representatives
from motor vehicle manufacturers have urged the agency to establish
minimum sound requirements for the stationary but active scenario when
the vehicle's gear selection is in drive.
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\115\ NHTSA-2011-0148-0031.
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The agency realizes that a sound in park may not be necessary for
safety in situations in which a vehicle is stationary for long periods
of time. This includes situations in which the vehicle is in park but
still ``on'' while the driver is preparing to exit the vehicle or while
the driver is waiting for someone. In these situations, the vehicle is
unlikely to commence movement at a moment's notice, which lessens the
need for the vehicle to emit some minimum sound level. The agency
solicits comment on approaches that could be adopted to ensure that the
vehicle is not producing sounds in situations in which the sound is not
needed for pedestrian safety. One of the approaches that the agency is
considering for mitigating noise caused
[[Page 2841]]
by idling vehicles would be to allow the countermeasure sound to
deactivate when the vehicles is shifted from drive into park. Another
option would be for the sound to deactivate after the vehicle has been
in park for some amount time such as two or five minutes. We seek
comment on how to mitigate unnecessary noise from vehicles idling for
long periods of time, while preserving the stationary but activated
sound when needed for pedestrians' safe navigation.
Our proposal contains a requirement and a test procedure for
measuring the directivity of the sound emitted by the vehicle because
the stationary but activated and pass by tests measure the sound at two
microphones two meters on either side of the vehicle's centerline. The
pedestrian, however, will be passing in front of the vehicle. We want
to ensure that there is no drop off in sound level from the side of the
vehicle where the measurement is taken to the front of the vehicle,
where the pedestrian hears the sound. The directivity measurement
involves placing a third microphone at the vehicle's centerline, two
meters in front of the vehicle. This measurement is done when
stationary but activated and the sound that is measured by the center
microphone must meet the same sound pressure level requirements in the
same one-third octave bands as the sound measured by the side
microphones.
c. Reverse
Our proposal contains a requirement and a test procedure for sound
while the vehicle is backing because this is one of the critical
operating scenarios we have identified in our research and statistical
studies. The requirement is limited to vehicles capable of rearward
self-propulsion. This means that motorcycles (and other motor vehicles,
possibly low speed vehicles) constructed without a reverse gear, such
that they cannot move rearward under their own power will not be
required to make a sound when moving backward (presumably by being
pushed). For all other vehicles, whenever the gear selection control is
in reverse, the vehicle must emit a sound meeting the specified sound
pressure level in each of eight one-third octave bands. These sound
pressure level requirements are greater than those when stationary but
activated, but less than those for the 10 km/hr (6 mph) pass by test,
because, while we know the vehicle will be moving while backing, we
know it will almost always move at less than 10 km/hr. The test for
backing is done when stationary but activated with the rear plane of
the vehicle on the microphone line because it is very difficult for a
test driver to reliably and repeatedly back a vehicle through the test
area at any constant speed.
d. Constant Speed Tests
Constant speed pass by tests are required at 10 km/hr (6 mph), 20
km/hr (12 mph), and 30 km/hr (18 mph). The vehicle passes through the
measurement area specified in SAE J2889-1 at a constant speed and the
sound profile is captured at the microphone line. Four consecutive
valid measurements are required and must be within 2 A-weighted dB of
each other. As in the stationary but activated test, invalid
measurements are those that contain sounds emitted by any component of
a vehicle's battery thermal management system, or that come from the
ICE on a hybrid vehicle with an ICE that runs intermittently. The
requirement is stated as a set of sound pressure levels in each of
eight one-third octave bands, at any speed greater than or equal to10
km/hr (6 mph), but less than 20 km/hr (12 mph). The constant speed pass
by tests at 20km/hr (12 mph) and 30 km/hr (18 mph) are conducted in the
same manner as the 10km/hr (6 mph) test but each have their own set of
required sound pressure levels. Requirements are in the same eight one-
third octave bands, but sound pressure levels are higher than the 10km/
hr (6 mph) test, because the pedestrian needs a longer detection
distance to avoid a faster moving vehicle. As discussed above, an HV
would not be required to meet the requirements for a given test speed
if it was not capable of operating in EV only mode at that speed.
e. Pitch Shifting
Our proposal contains a requirement for pitch shifting to signify
acceleration and deceleration. Sounds to alert pedestrians to
acceleration and deceleration are required by the language of the PSEA.
Pitch shifting gives the pedestrian information about the acceleration
or deceleration of an approaching vehicle. This information is
important to the pedestrian in making a decision about whether or not
to cross in front of a vehicle. An accelerating vehicle does not intend
to stop. A decelerating vehicle on a path parallel to the pedestrian
may be slowing to make a right turn into the pedestrian's path if she
or he were to cross the street. The proposed requirement is that the
fundamental frequency of the sound emitted by the vehicle increase with
speed by at least one percent per km/hr between 0 and 30 km/hr (18
mph). There is no test procedure associated with this requirement.
Pitch shifting is verified by comparing the fundamental frequency from
the stationary but activated, 10 km/hr (6 mph), 20 km/hr (12 mph), and
30 km/hr (18 mph) tests.
The agency is aware that the pitch of the sound produced by a
traditional ICE vehicle does not increase linearly because as a vehicle
transitions to a higher gear, the revolutions per minute of the engine
drop, and therefore so does the frequency of the sound produced by the
engine. The agency notes that it is possible that the sound produced by
an HV or EV may not increase linearly in pitch because the sound output
may change as the vehicle transitions from a lower gear to a higher
gear. The agency does not believe that this phenomenon will have a
significant impact on the agency's method for measuring pitch shifting
because a majority of the electric motors on vehicles subject to this
proposed standard have single gear transmissions.
While the pitch shifting requirement contained in this proposal
does not exactly mimic the sound produced by a traditional ICE vehicle,
increasing pitch is a characteristic that pedestrians associate with an
accelerating vehicle based on experience. Because the pitch shifting
requirement only applies while the vehicle is traveling at speeds
between 0 km/hr and 30 km/hr (18 mph), the sound produced by a vehicle
meeting the requirements of this proposal will be similar to the sounds
produced by a traditional ICE vehicle. The agency believes that the
pitch shifting requirement contained in this proposal will approximate
the acoustic behavior of traditional ICE vehicles closely enough to
provide pedestrians with valuable information about a vehicle's change
in speed.
Manufacturers and their representatives, in meetings with NHTSA
staff, have expressed concerns that it is difficult to measure the
change in pitch of a sound produced by a vehicle on a vehicle level
during a pass by test. Manufacturers have requested that the agency
measure pitch shifting using a component level test.
The agency is hesitant to include a component level test because we
want the standard to be technology neutral and because we do not wish
to limit technological innovation. Further, the agency is aware that
manufacturers plan to use different technologies to comply with this
standard so defining the component subject to the component level test
could prove difficult. The agency is aware that some sounds produced by
a vehicle do not necessarily shift in pitch as the vehicle increases
speed. However, the agency
[[Page 2842]]
believes that it is possible using the test procedures in S7 to
accurately measure the change in pitch of a sound added to a vehicle
for purposes of complying with this proposed standard.
The agency seeks comment on including a component level test to
measure pitch shifting in the test procedure. If the agency included a
component level test in the final rule, it would apply to devices added
to a vehicle to generate sound for purposes of complying with this
proposed standard. A sound generation device would be defined as a
device that is not connected to the vehicle's propulsion source or
drive train that is installed on a vehicle for the purposes of
generating sound. Under such a test the agency would place a microphone
one meter in front of the sound generating device mounted 0.5 m above
the floor. The agency would then input into the device a signal
corresponding to the vehicle speeds 0 km/hr, 10 km/hr (6 mph), 20 km/hr
(12 mph), and 30 km/hr (18 mph) and make 5 second recording of the
output of the sound generating device at each speed. The measurement
would have to be conducted under the conditions in S6.1 with the
instruments specified in S6.3.1. The performance requirements for a
component level pitch shifting measurement would be the same as the
proposed requirements in S5.1.6.
The agency's proposed method for measuring pitch shifting depends
on the presence of a strong tone in the sound. The pitch of a sound is
verified by tracking this tone as it increases in frequency for each
pass by test as the vehicle increases speed. It is difficult to verify
a sound's increase in pitch if the sound does not have any strong
tones.
The agency has some concerns about identifying the tone of a sound
and tracking this tone as the vehicle increases speed. The agency plans
to conduct further research to verify that it is possible to track a
tone's increase in frequency as the vehicle increases speed. If it is
not possible to identify a tone to track in order to verify the
increase in a sound's pitch, the agency may use a different method to
verify the increase in a sound's pitch. Possible methods to quantify
pitch shifting include in-situ and bench tests of constant speed or
accelerating pass-by events. A method to track tonal components is
needed. Additional measurements, not currently being collected in the
compliance test procedure, such as engine RPM may be required in order
to apply the verification procedure for pitch shifting to spectrally
complex sounds. We request comments on this issue.
f. Recognizability
The PSEA also requires that our new standard have performance
requirements that ensure the sound emitted by an HV or EV is one that
is recognizable as a motor vehicle. Our proposal includes requirements
to address recognizability. The sound emitted by the vehicle to meet
requirements for each of the critical operating scenarios must contain
at least one tone, and at least one tone no higher than 400 Hz. A
component is defined as a tone if the total sound level in a critical
band centered about the tone is 6 dB greater than the noise level in
the band. The criteria set for determining the appropriate tone-to-
noise ratio could be refined. Possible refinements to the tone-to-noise
ratio criteria to better suit the current application include a)
reduction in the bandwidth, or b) inclusion of all tones within the
band for the tone-to-noise calculation, and c) possibility of changing
the 6 dB criterion.
The sound must also have broadband content in each one-third octave
band from 160 Hz to 5000 Hz. Broadband components are those that have
energy at all frequencies within a one-third octave band. This
broadband component requirement could be met, for example, by Gaussian
distributed random noise, a set of damped sine waves whose damping and
spacing covers a one-third octave band, or a combination of tones and
noise.
g. Vehicles of the Same Make and Model Emitting the Same Sound
Pursuant to the PSEA, NHTSA is required to ensure that vehicles of
the same make and model emit the same sound or set of sounds. We
interpret a vehicle model as a specific grouping of similar vehicles
within a vehicle line. 49 CFR part 541, Federal Motor Vehicle Theft
Prevention Standard, defines line as ``a name which a manufacturer
applies to a group of vehicles of the same make that have the same body
or chassis, or otherwise are similar in construction or design.'' If a
manufacturer calls a group of vehicles by the same general name as it
applies to another group, but adds a further description to that name
(e.g., Ford Fusion Hybrid, or Toyota Prius Three), the further
description indicates a unique model within that line.
The proposed standard would require vehicles of the same make and
model to emit the same sound or set of sounds for a particular model
year. Thus a 2012 Prius Two could have a different sound than a 2012
Prius Four. A 2012 Prius Two could also have a different sound than a
2013 Prius Two. All Prius Twos from the 2012 model year would be
required to emit the same sound or set of sounds.
We are only proposing to require that only sounds added to vehicles
for the purpose of complying with this proposed standard be the same.
The requirement that sounds emitted by vehicles of the same make and
model be the same does not apply to sounds generated by a vehicle's
tires or body design or sounds generated by the mechanical functions of
the vehicle. Because NHTSA intends only to test whether sounds added to
a vehicle for purposes of complying with this standard are the same, we
propose to test for this requirement at the stationary condition.
Testing at the stationary condition will ensure that the agency is able
to test sound added to the vehicle without interference from other
sources of vehicle noise. We seek comment on testing to ensure that
sound produced by two different vehicles of the same make and model is
same at additional test scenarios other than idle. We also seek comment
on the extent to which changing a vehicle's tires or body design would
affect the vehicle's sound profile.
The agency proposes to consider the sounds produced by two vehicles
to be the same if, when tested according to S7.2, the sound emitted by
the two vehicles has a sound pressure level within 3 A-weighted dB for
every one-third octave band between 315 Hz and 5000 Hz. The agency
seeks comment on this method for determining if two sounds are the
``same.''
VIII. Alternatives Considered But Not Proposed
As discussed below, the reason that the agency did not propose many
of the alternatives described in this section was because of
difficulties in compliance testing. These alternative methods for
developing sounds could be used so long as the resulting sounds meet
the requirements of the proposal. The agency believes that allowing
multiple compliance alternatives would make compliance testing unduly
complicated. The agency seeks comment on modifications to the acoustic
specifications contained in Section XII of this proposal. To the extent
that the suggested modifications allow for increased flexibility
without a decrease in safety, the agency will consider adopting the
comments in the final rule.
[[Page 2843]]
A. Requiring Vehicle Sound To Be Playback of an ICE Recording
The agency considered specifying that the alert sound used on EVs
and HVs be a recording of an ICE peer vehicle. After further
consideration and based on comments on the NOI, the agency concludes
that a recording based on an ICE vehicle is not a viable regulatory
option for ensuring that EVs and HVs produce sound levels sufficient to
allow pedestrians to safely detect them. The agency believes that it is
not practical to require that the alert sound be a recording of an ICE
vehicle because of concerns about enforcing such a standard, because
the recording of an ICE engine might not be as detectable as the sounds
that the agency is proposing, and because of the expense of creating
and replaying the recording. In addition manufacturers have expressed a
desire for flexibility in developing pedestrian alert sounds and this
approach is unnecessarily limiting in that aspect.
The agency believes that requiring an alert sound based on a
recording of an ICE vehicle would unnecessarily complicate the agency's
compliance testing. Under the compliance test that the agency was
considering for an alert sound based on a recording of an ICE vehicle,
manufacturers would be required to report to the agency which vehicle
the alert sound was recorded from. The agency would then test both the
vehicle the alert sound was recorded from and the EV or HV on which the
alert sound was installed and compare the acoustic profiles of the two
sounds. Testing two vehicles would double the time and expense of
conducting compliance testing. While the agency does not require
manufacturers to conduct any testing to certify their vehicles, the
agency recognizes that many manufacturers choose to follow the test
procedure in the agency's standards to be assured of compliance. Thus,
increasing the amount of vehicles tested would also increase
manufacturers' testing costs.
The agency does not believe that the recording of an ICE would be
as detectable as the sounds meeting the specifications in S5 of this
proposal. Most of the frequency content produced by an ICE is in the
lower frequency part of the spectrum where the ambient is highest.
Because ICE sounds have a significant amount of low frequency signal
content, they are more likely to be masked by the ambient than sounds
with higher frequency tones or high frequency broad band. The agency's
Phase 2 research indicated that sounds that contain only elements
produced by the fundamental combustion of the ICE are relatively
ineffective in providing adequate detection. An alert sound that was
based on a recording of an ICE vehicle would not allow manufacturers to
use sounds that had tones in frequencies for which the ambient is not
very strong and that might be more detectable than a recording of an
ICE.
In their comments on the NOI, manufacturers have stated that it can
be more expensive to create and replay an alert sound based on a
recording of an ICE vehicle than to create and replay a synthetic
sound. Manufacturers have stated that they would have to conduct
recordings at several vehicle speeds and then process the sound so that
when played through a speaker system mounted on the vehicle it would
produce a smooth sound that mimics the sound produced by the ICE
vehicle on which the recording was based.
Creating the recording at several different speeds adds an
additional expense in creating the sound that is not present in
synthetic sounds. The recordings would have to be captured by multiple
vehicle pass bys or through recordings conducted indoors in hemi-
anechoic dynamometer chambers, both of which would entail significant
cost.
Playing back the sound so that it sounded like an ICE vehicle would
likely require costly high performance signal processing. High
performance signal processing is necessary for systems to be able to
accurately reproduce sounds for acceleration and deceleration. One
commenter also stated that the vehicle on which the alert sound was
installed would have to have a larger data storage capacity to replay
an alert sound recorded from an ICE vehicle. The commenter stated that
the vehicle would require this additional storage capacity because the
system would have to retain a recording of the ICE at each speed below
the crossover speed in order to reproduce the recording. This
additional storage would lead to additional expense for the alert sound
system.
Commenters also stated that a recording of an ICE played back over
a speaker mounted on an EV or HV would not sound exactly like the
recorded vehicle because speaker systems that manufacturers would be
using cannot reproduce sound with that level of accuracy. The inability
of speakers mounted on vehicles to reproduce the sound of the recorded
vehicle at a high level would diminish the advantages in the level of
pedestrian recognition of the alert sound that the agency had hoped to
gain in requiring that the alert sound be a recording of an ICE
vehicle.
In comments on the NOI and in meetings with NHTSA staff,
manufacturers have stated that they wish to have a certain degree of
flexibility to develop sounds that pedestrians will find recognizable
and detectable but will also be pleasing to the driver. Given the other
difficulties present in requiring an alert sound based on a recording
of an ICE vehicle, the agency does not believe that the benefit gained
from requiring an alert sound based on a recording of an ICE vehicle
justifies restricting manufacturer choice regarding the sounds that can
be used as alert sounds especially since some of the sounds that
manufacturers may wish to use could be more detectable than recordings
of ICE vehicles.
Given that alert sounds based on recordings of ICE sounds would be
more expensive to test, create, and replay than the sounds fitting the
parameters in Section XIII and the marginal benefit to pedestrians in
recognizing ICE sounds that might be gained from using a recording of
an ICE as an alert sound, the agency believes that the specifications
in Section XIII present a more feasible approach to establishing
minimum sound levels for EVs and HVs.
B. Requiring That the Alert Sound Adapt to the Ambient
The agency considered requiring that the sound level of the alert
sound vary based on the ambient noise level in the environment
surrounding the vehicle. The agency is aware that technology is
available for back-up alarms for heavy vehicles and construction
equipment that vary the sound pressure level of the alert sound based
on the sound pressure level of the ambient.
The agency decided not to pursue this approach because it was not
justified based on safety need, because of concerns about the impact of
environmental noise, and because of concerns about the sophistication
of this technology. Based on conversations with the groups representing
the visually-impaired community and a review of literature describing
navigation by visually-impaired individuals, we have tentatively
concluded that pedestrians who are visually impaired are taught not to
attempt to cross intersections using hearing alone in urban
environments with a high ambient noise levels.\116\ The agency believes
that sounds meeting the specifications in Section XIII will provide
adequate detectability for pedestrians in ambient environments in which
sound cues are necessary to assist pedestrians in avoiding collisions
with
[[Page 2844]]
vehicles. The agency is concerned that an alert sound that reacts to
the ambient noise level could contribute to an increase in the overall
ambient noise level and contribute to noise pollution. An alert sound
that would be detectable over a high urban ambient sound level would
raise the overall ambient level simply by its presence. Multiple
vehicles with variable noise alert devices would contribute to noise
pollution by driving the ambient sound pressure level higher and higher
by reacting to the sound being produced by other vehicles. The agency
is concerned that this technology is not at a stage where it can avoid
the feedback effect of two equipped vehicles reacting to each other and
thereby increasing the overall noise level.
---------------------------------------------------------------------------
\116\ See footnote 8.
---------------------------------------------------------------------------
Because an alert sound that adapted to the ambient environment
would provide little additional safety benefit and could lead to
increases in noise pollution, the agency decided that such a device
should not be required in this rulemaking.
C. Acoustic Profile Designed Around Sounds Produced by ICE Vehicles
The agency is hesitant to set the minimum sound level requirements
for quiet vehicles to mean levels produced by ICE vehicles. Setting the
minimum sound requirements for HVs and EVs at the mean levels produced
by ICE vehicles could have the effect of cutting off efforts by
manufacturers to reduce vehicle noise emissions. This would also serve
to increase the overall levels of vehicle noise emissions because
vehicles that had been quieter would now be required to produce sound
at the mean sound level of ICE vehicles.
Acoustic requirements based on the sound level of ICE vehicles also
include a pitch shifting requirement, as we have proposed in this
notice.
The agency is also hesitant to set the minimum sound levels for HVs
and EVs at 3 (or 2) standard deviations below the mean sound level
produced by ICE vehicles because then sound levels may not be high
enough to allow pedestrians to detect these vehicles. The agency has
yet to determine whether all ICE vehicles produce sound levels that are
sufficient enough to allow pedestrians to readily detect them. Because
the PSEA requires the agency to study whether quiet ICE vehicles pose
an increased risk of collisions with pedestrians, the agency does not
believe that it is in a position to assume that very quiet ICE vehicles
are easily detectable by pedestrians.
As discussed in Section VI.C of this notice, in our Phase 3
research we developed a set of minimum sound level criteria for HVs and
EVs based on the sounds produced by current ICE vehicles. While we are
not proposing acoustic specifications based on the sound profile of ICE
vehicles at this time we seek comment on the acoustic specifications
below.
As discussed in section VII.D.1, the following one-third octave
bands were identified as critical for vehicle detectability: 315, 400,
500, 2000, 2500, 3150, 4000, and 5000 Hz. A total of 152 measurements
of stationary but activated and 10 km/hr (6 mph) forward pass-by events
were analyzed to determine levels for these two operations. Data came
from three different sources (the International Organization of Motor
Vehicles Manufacturers (OICA), Phase 2 as described above, and Phase 3
research). Sound levels for backing were derived from the 10 km/hr (6
mph) forward levels but adjusted downward by 3 dB to account for
directivity. In particular, the sound pressure level in the rear of an
ICE vehicle is about 3 dB lower than what is measured at the SAE 2889-1
microphones. Two versions of potential requirements based on measured
ICE levels are provided below. Table 13 shows minimum A-weighted sound
levels based on the mean levels of ICE vehicles in the dataset. Table
14 shows minimum A-weighted sound levels based on the mean levels minus
one standard deviation. Mean levels minus two standard deviations were
also considered, however, these levels are not expected to be
sufficiently detectable in many cases.
Table 13--Minimum A-Weighted Sound Levels Based on ICE Mean Levels
----------------------------------------------------------------------------------------------------------------
One-third octave band center Stationary but
frequency, Hz activated Backing 10 km/hr 20 km/hr 30 km/hr
----------------------------------------------------------------------------------------------------------------
315............................. 40 42 45 52 55
400............................. 41 44 47 53 57
500............................. 43 45 48 54 59
2000............................ 44 46 49 55 59
2500............................ 44 46 49 53 56
3150............................ 43 44 47 52 54
4000............................ 41 42 45 49 51
5000............................ 37 40 43 45 48
Overall A-weighted SPL Measured 52 54 57 62 66
at SAE J2889-1 PP'line.........
----------------------------------------------------------------------------------------------------------------
Table 14--Minimum A-Weighted Sound Levels Based on ICE Mean Levels Minus One Standard Deviation
----------------------------------------------------------------------------------------------------------------
One-third octave band center Stationary but
frequency, Hz activated Backing 10 km/hr 20 km/hr 30 km/hr
----------------------------------------------------------------------------------------------------------------
315............................. 34 37 40 48 52
400............................. 35 40 43 49 53
500............................. 37 42 45 51 56
2000............................ 39 42 45 50 54
2500............................ 39 41 44 49 51
3150............................ 39 40 43 47 49
4000............................ 36 37 40 42 44
5000............................ 29 34 37 38 40
Overall A-weighted SPL Measured 46 49 52 58 61
at SAE J2889-1 PP'line.........
----------------------------------------------------------------------------------------------------------------
[[Page 2845]]
Note, neither the mean nor the mean minus one standard deviation
have levels that are as high as those for our proposed requirement
specification (Table 12) at the low frequencies. This does not indicate
a disagreement between the two approaches, but rather indicates that
low frequencies of typical ICEs are not as detectable in the ambient
used in the modeling as typical ICE high-frequency components. Finally,
Table 14 has levels that are as high as Table 12 for stationary but
activated only at 3150 and 4000 Hz. Again, this does not mean that
vehicles with levels below the mean will never be detectable, but
rather that they will not likely be detectable for the ambient that was
used in the modeling.
D. Acoustic Profiles Suggested by Manufacturers
The Alliance of Automotive Manufacturers (the ``Alliance'')
submitted acoustic specifications that could serve as minimum sound
requirements for HVs and EVs.\117\ The Alliance proposed that the
agency specify that HVs and EVs emit a sound with frequency content
between 150 Hz and 3000 Hz. The Alliance proposal would require that
sound emitted by HVs and EVs have at least two one-third octave bands
with a sound pressure level of 44 A-weighted dB within this frequency
range with one of the one-third octave bands being above 500 Hz and an
overall sound pressure level of 48 A-weighted dB.
---------------------------------------------------------------------------
\117\ A presentation given at a meeting with NHTSA staff with
the details of the proposal is available in the rulemaking docket
accessible through regulations.gov. NHTSA-2011-0148-0022.
---------------------------------------------------------------------------
The agency believes that specifications for sound levels in only
two one-third octave bands would not guarantee that sounds produced by
HVs and EVs would be detectable in the range of ambient conditions in
which the agency believes that pedestrians would need to detect them.
If a sound has a greater number of one-third octave bands, it is more
likely to be detectable at a given ambient. Sounds containing only one
or two one-third octave bands with elevated sound pressure levels would
be masked by ambient sound with strong spectral content in the same
one-third octave bands which would hinder the ability of pedestrians to
detect the sound. If a sound has elevated sound pressure levels at a
wide range of one-third octave bands, it is less likely that an ambient
will mask all of the bands that would increase the likelihood that the
sound would be detectable.
We do not believe that the suggestion submitted by the Alliance
specifies the one-third octave bands for which a minimum sound level is
required in enough detail. The placement of one-third octave bands in
the frequency spectrum influences the detectability of a sound. While
the Alliance's suggestion would require one of the one-third octave
bands to be at a frequency band above 500 Hz, the agency does not
believe that this specification would ensure that the sounds would be
loud enough for pedestrians to detect them at speeds above 0 km/hr.
Based on the agency's detection model, a one-third octave band with a
sound pressure level of 44 A-weighted dB would not be detectable at 10
km/hr (6 mph) if the frequency of the one-third octave band was below
3150 Hz. A sound with two one-third octave bands with a sound pressure
level of 44 A-weighted dB would be masked by the ambient if those one-
third octave bands were both positioned in mid-range frequencies for
which the ambient level is highest.
We believe that the agency's proposal would better ensure that
sounds produced by HVs and EVs would be recognizable to pedestrians as
a motor vehicle in operation. The Alliance's suggestion does not
include requirements for broadband, low frequency sound that
contributes to recognizability.
These suggestions have been considered, but they do not meet either
the requirements of the PSEA or the safety need because the suggestions
are not specific enough about the placement of required one-third
octave bands in the frequency spectrum to adequately ensure the
detectability of the sound and they do not contain specifications for
recognition. However, we will consider any further comments from the
Alliance and all other commenters to this proposal with regard to the
sound that should be made and, to the extent those comments are
persuasive, they will be useful in creating the final rule. The agency
seeks comment on the acoustic profile of the minimum sound
requirements, as well as on the number of one-third octave bands for
which the agency should establish requirements.
In its comments on the NOI, Nissan described the acoustic profile
of the sound that is emitted by the Nissan Leaf. Nissan described the
Leaf sound as having two peaks in sound pressure level with one peak
near 2500 Hz and one peak near 600 Hz. Nissan stated that it included
the 2500 Hz peak in sound pressure level to provide enhanced detection
for pedestrians with normal hearing and the 600 Hz in sound pressure
level to provide detection for pedestrians with age related hearing
loss. The Leaf sound does not include mid-range one-third octave bands
so that sound does not contribute to overall increases in ambient
noise.
As discussed above, the agency believes that sound should be
present in multiple high frequency one-bands to increase the likelihood
that a pedestrian will be able to detect the sound in multiple ambients
with differing acoustic profiles. Like the Leaf sound, the acoustic
specifications in this proposal do not contain requirements for the
one-third octave bands that would contribute to the greatest increase
in overall levels. The one-third octave band levels in Table 12 would
ensure that pedestrians with age related hearing loss would be able to
detect the sounds meeting these requirements. They would have a
significant amount of detectable content below 2000 Hz which, according
to Nissan, is the threshold for age related hearing loss.
The agency believes that the acoustic specifications for minimum
sound level requirements for HVs and EVs in the agency's proposal will
provide manufacturers flexibility to develop alerts that are detectable
and recognizable to pedestrians and pleasing to drivers. While the
specifications described in the agency's proposal are more detailed
than those contained in proposals that the agency received from
manufacturers and their representatives, the agency believes that the
specifications in its proposal place a greater emphasis on
recognizability than specifications submitted by manufacturers. The
agency's specifications will also ensure that sounds produced by HVs
and EVs will be detectable in a wider range of ambient sounds than
would be the case in suggestions submitted by manufacturers because
specifications for a wider range of one-third octave bands increases
the likelihood that the sound pressure level in any one one-third
octave band will exceed the ambient for that frequency.
E. International Guidelines for Vehicle Alert Sounds
As discussed in Section VI.D above, the Japanese government issued
voluntary guidelines for manufacturers to use when installing alert
sounds on HVs and EVs. The ECE has also adopted these guidelines for
use on a voluntary basis. In their comments on the NOI, several
manufacturers stated that the agency should use these guidelines as a
basis for ensuring that HVs and EVs produce sound levels sufficient to
allow pedestrians to detect these vehicles.
[[Page 2846]]
The agency does not believe that these guidelines have the level of
detail necessary to serve as the basis for an FMVSS. The guidelines do
not contain objective minimum requirements that manufacturers would be
required to meet. The guidelines state that levels of sounds produced
by HVs and EVs should not exceed the levels produced by ICE vehicles of
the same class. The agency does not believe that this description of
the sound levels would adequately ensure that these vehicles will be
detectable by pedestrians or provide manufacturers with a set of
requirements that they would be expected to meet.
The guidelines also do not contain an objective description of the
acoustic characteristics that the sound should possess. Rather, the
guidelines list what the sounds should not sound like. The guidelines
state that vehicle emitted sounds should not sound like ``siren[s],
chime[s], bells, melody, horn[] sounds, animals, insects, [or] sound[s]
of natural phenomenon such as wave[s], wind, [or] river current[s].''
We do not believe that we would be able to tell whether a sound fell
within one of the exclusions by means of an objective acoustic
measurement because these descriptions do not contain any measurable
values.
F. Suggestions in Comments to the NOI That Did Not Satisfy the
Statement of Purpose and Need for the Rulemaking
Several of the commenters to the NOI suggested that the agency
either take no action or address HV and EV collisions with pedestrians
by other means. The PSEA requires the agency to establish an FMVSS that
sets minimum sound requirements for HVs and EVs so taking no action was
not a viable alternative.
One commenter suggested that the agency use advanced pedestrian
crash avoidance technologies as a means of addressing collisions
between HVs and EVs and pedestrians. While these technologies offer a
promising means of preventing collisions between pedestrians and all
vehicles, they are not yet mature or widespread enough for the agency
to be able to consider making these devices a mandatory piece of safety
equipment on a vehicle at this time. Furthermore, requiring advanced
pedestrian crash avoidance devices on HVs and EVs would not meet the
requirements of the PSEA.
G. Possible Jury Testing for Recognizability of a Synthetic Sound
The PSEA requires the agency to develop performance requirements to
determine whether pedestrian alert sounds required by the standard are
recognizable as being emitted by a motor vehicle in operation. The
agency has tentatively decided that a compliance test for
recognizability based solely on acoustic measurements over spectral
distribution detailed above is the best way to ensure recognizability
while, at the same time, allowing manufacturers the flexibility to
design sounds representative of each make/model of vehicle. While the
agency believes that sounds that fall within the agency's acoustic
parameters will be recognizable to the public as a motor vehicle in
operation, it is possible that manufacturers may wish to use sounds
that would be equally as recognizable as those sounds meeting the
agency's proposed specifications but would fail to satisfy the
requirements proposed.
Notwithstanding the agency's tentative decision to use a set of
sound parameters to achieve recognizability, we solicit comment on the
possibility of allowing another compliance procedure designed to ensure
that pedestrian alert sounds are recognizable and detectable. We are
considering, but not proposing, allowing compliance through jury
testing of sounds that would not meet the agency's acoustic
specifications for recognizability. Allowing jury testing of sounds may
give manufacturers greater flexibility in meeting the requirements of
the standard. We specifically are soliciting comment on the
desirability and the feasibility of a jury testing procedure for
ensuring that sounds would be recognizable as a motor vehicle.
While the agency believes that human subject testing could provide
an accurate evaluation of the recognizability of the pedestrian alert
sound, the agency recognizes jury testing poses its own challenges.
While the agency has tentatively concluded that jury testing is
objective and repeatable as required by the Motor Vehicle Safety Act,
manufacturers have expressed technical concerns about compliance
testing by the agency using human subjects.
Under the jury testing framework envisioned by the agency,
manufacturers would be required to submit information to NHTSA
demonstrating that the sounds emitted by their vehicles are
recognizable as a motor vehicle in operation. Under this framework,
manufacturers would conduct a jury test according to procedures
established by NHTSA and then submit to NHTSA documentation of the
results of the jury and a certification that the jury test was
conducted according to the procedures established by the agency.
After NHTSA received documentation of the manufacturer's jury test,
the agency would examine the documents to ensure that the test was
conducted properly. The agency would also include the same performance
test for detectability in the standard as is proposed today.
While the agency believes that a compliance test using jury testing
is objective and repeatable, manufacturers have expressed concerns in
discussions with the agency about being subjected to a jury based
performance standard. We recognize that automobile manufacturers face
significant penalties in the event that they are determined to be
noncompliant with a FMVSS. In an effort to provide manufacturers with
regulatory certainty and in acknowledging that the agency does not
currently specify any jury-based compliance testing, we have concluded
that the most feasible approach to jury testing at this time would be
for the agency to require manufacturers to conduct the jury tests
themselves and submit their results to NHTSA as part of their vehicle
certification. Thus, the manufacturers' records that the jury test was
conducted properly with the jury determining that the sound was
recognizable would constitute the manufacturers' certification.
The agency believes that a certification procedure outlined above
would be objective and repeatable, as required by the Motor Vehicle
Safety Act. While recognizability may be described as a subjective
concept, the procedure envisioned by the agency for determining whether
a sound is recognizable as a motor vehicle would be stated in objective
terms. The standard would specify the composition of the jury, the jury
size, how to conduct the jury test, and pass fail criteria. The jury
procedure would be repeatable because the underlying statistics dictate
that if the required percentage of jurors finds the ICE control sound
and non-ICE sound recognizable as a motor vehicle, a different jury
would make the same determination of whether the non-ICE sound is
recognizable or not. In conducting a compliance test to determine if
the sound complied with the standard, NHTSA would not conduct its own
jury testing; instead the agency would review the manufacturer's
documentation of its jury process to ensure the testing performed by
the manufacturer was conducted according to the standard. Thus, a
manufacturer would not be subject to the possibility that a jury test
done by NHTSA would come to a different conclusion about the sound than
the jury test conducted by the manufacturer.
The jury testing procedure envisioned by the agency would provide
an
[[Page 2847]]
objective, repeatable method for determining compliance as required
under the United States Court of Appeals for the District of Columbia
Circuit's interpretation of the Motor Vehicle Safety Act in Chrysler v.
Department of Transportation.\118\ As discussed above, this jury test
procedure would not subject the manufacturer to any subjective
determination regarding compliance. Manufacturers would be assured of
compliance if they conducted their jury test according to the agency's
procedure and properly documented the process and results.
---------------------------------------------------------------------------
\118\ 472 F.2d 659 (D.C. Cir. 1972).
---------------------------------------------------------------------------
The jury of human subjects would be comprised of a sample size to
make the jury results as repeatable as possible across multiple juries.
Under the jury testing framework that the agency would mandate, the
jury members would be exposed to two different sounds, a control sound
and the sound that the manufacturer wished to use to meet the
requirements of this standard.
The jury members would be asked to identify whether each sound was
a regular and detectable vehicle sound or not. The jury size that the
agency would require under this alternative certification procedure
would depend on the statistical power the agency wished to achieve, the
recognition rate of the ICE-like control sound, and recognition rate
that the agency would specify for non-ICE sounds.
Assuming a 90 percent statistical power, a 90 percent ICE
recognition rate and a minimum candidate sound recognition rate of 65
percent, (that is, 65 percent of the jury would have to find the
candidate sound recognizable and detectable for the manufacturer to
certify the vehicle with the candidate sound) the jury sample size
would need to be at least 28 people to provide results that would be
repeatable. If the statistical power and ICE recognition rate were 90
percent and the minimum candidate sound recognition rate was changed to
75 percent, the size of the jury would increase to 54 people. If the
ICE recognition rate was lowered to 85 percent and the statistical
power was maintained at 90 percent, a minimum recognition rate of 65
percent for the candidate sound would require a jury of 45 people. A
minimum recognition rate of 75 percent for the candidate sound under
the same circumstances would require a jury of 140 people. Thus, the
size of the jury increases as the gap between ICE recognition rate and
the candidate sound recognition rate closes.
In the event that the agency were to adopt a jury based approach in
the pedestrian alert sound standard for determining recognizability,
the jury size would be determined based on the agency's decision of the
statistical power, ICE-recognition rate, and minimum candidate sound
recognition that the agency believes will ensure that pedestrians will
be able to safely recognize the vehicle equipped with the candidate
alert sound. We have tentatively concluded that jury testing to
determine the recognizability of sounds should be conducted at a 90
percent statistical power. The agency seeks comment on the general
approach to jury testing that the agency is considering as discussed
above. Specifically, the agency would like comment on the appropriate
size of the jury for testing to determine whether sounds are
recognizable as a motor vehicle, the statistical power that should be
used for the test, the reference ICE recognition rate that should be
required, and the minimum candidate sound recognition rate that should
be required.
If the agency were to specify a jury test for recognizability, the
agency would specify the specific demographic composition of the jury
to ensure that the jury testing results would be repeatable across all
segments of the public. The standard would require the jury to be
composed of adults between the ages of 18 and 69 years old, with equal
numbers of male and female participants.\119\ Subjects from the 18-29
year-old, 30-49 year-old age, and 50-69 year-old age groups would each
make up one-third of the jury. Subjects would be required to be willing
to be screened for hearing threshold shift in the 500 Hz to 8,000 Hz
frequency range. Subjects with an estimated hearing loss of 20 dB or
more above the normal range for the 500 Hz to 8,000 Hz range would be
excluded from the study. Jury subjects would also be prohibited from
being employees of the manufacturer conducting the testing or otherwise
interested in the outcome of the test.
---------------------------------------------------------------------------
\119\ The jury composition requirements would allow for a slight
deviation from the requirement that the jury be composing of equal
numbers males in females in the event that the jury consisted of an
odd number of subjects.
---------------------------------------------------------------------------
A jury test for recognizability of pedestrian alert sounds
specified by the agency would be conducted using headphones in an
audiometric test room. The jury test procedure would specify a maximum
acceptable ambient for the audiometric test room in which the jury test
would be conducted similar to the acceptable ambient for audio testing
described in ANSI S3.1-1991, Maximum Permissible Ambient Noise Levels
for Audiometric Test Rooms, American National Standard. NHTSA would
also require that jury testing be conducted with high quality head
phones. NHTSA has concluded that headphones are preferable to a test
utilizing loudspeakers. Headphones allow for greater flexibility in the
setup of the jury room. Further, jury members listening to the sounds
via headphones would not be influenced by their seating position or the
room's acoustics.
The manufacturer conducting the jury test would be required to use
a vehicle of the same make to create the ICE control sound used in the
jury testing and would be required to submit that sound to NHTSA as
part of its certification documentation. The audio file played for the
subjects would be required to include synthetic urban noise, filtered
according to a specification developed by Torben Pedersen in ``White
Paper on External Sounds of Electric Cars,'' \120\ as background to
simulate ambient that pedestrians would encounter when attempting to
detect an EV or HV in the everyday environment. The audio file used for
jury testing should be created using a binaural recording technique
that accurately reproduces the qualities of a moving sound source. This
is ordinarily accomplished by making recordings of actual vehicle pass-
bys. The agency believes that the operating scenario under which the
vehicle was recorded will influence whether the jury members will think
the sound is recognizable. The agency believes that the sound used for
the jury evaluation should be recorded while the vehicle is
accelerating. The sound of a vehicle accelerating provides many of the
sound cues that the agency is addressing through the acoustic
specifications for recognizability The agency included specifications
for pitch shifting in today's proposal so that when the vehicle is
accelerating the vehicle is providing acoustic cues about its changing
speed The agency also believes that pitch shifting contributes to
recognizability. Because the sounds that manufacturers may want to
evaluate using this alternative framework should continue to provide
pedestrians with cues that the vehicle is changing speed and because
information provided by the sound that a vehicle makes while it is
accelerating contributes to recognizability, the agency believes that
the jury should evaluate the sound produced by the vehicle while it is
accelerating, in addition to constant speed pass-by.
---------------------------------------------------------------------------
\120\ Available at http://media.wix.com/ugd/64a49a_43313ad70e7c40f43150cf747b2e5c44.pdf?dn=A520040+-+DSTN+-+White+paper+electric+cars+-+av122410+-+ECT+LR.pdf.
---------------------------------------------------------------------------
[[Page 2848]]
The sample of the pedestrian alert sound played to the jury should
be 10 seconds in length for both the ICE control sound and the
candidate sound the manufacturer is attempting to certify. The control
sound and the candidate sound the manufacturer is seeking to evaluate
would be played in a random sequence for each jury member. Thus, some
members of the jury would hear the control sound first while others
would hear the candidate sound first. The agency would specify the
loudness at which the sound would be played for the jurors as well as
the level of the synthetic ambient noise.
Responses would be recorded using bubble-in survey forms with the
bubbles representing yes or no for each sound for both the ICE control
sound and the sound the manufacturer is seeking to certify. These forms
would require minimal training for jury members as most jury members
would likely be familiar with these forms. The jury instructions would
consist of the following statement:
In this evaluation you will be presented a pair of sounds. You are
asked to indicate whether you believe that each of the sounds is
recognizable as a motor vehicle sound or not. Select the response
listed on the form that corresponds with your view of that sound. If
you think that sound A is recognizable as a motor vehicle sound
select yes, if you do not think that sound A is recognizable as a
motor vehicle select no. After you have made your selection for
sound A, evaluate sound B and check the box that corresponds with
your view on whether Sound B is recognizable as a motor vehicle
sound. If you think that sound B is recognizable as a motor vehicle
sound select yes, if you do not think that sound B is recognizable
as a motor vehicle select no. Since the objective of the experiment
is to understand the individual's reaction to the sounds, there are
no right or wrong answers.
The agency seeks comment on the jury instructions outlined above.
The agency is specifically interested in instructions that result in a
yes or no answer and that would not lead members of the jury to
prejudge the sound. The agency recognizes that asking whether the sound
is a regular and detectable vehicle sound may influence the jury to a
certain degree. However, in order for the results of the jury test to
be repeatable, jury responses would need to come in the form of yes or
no answers.
The validity of the jury test would be dependent on the jury
members identifying the ICE control sound at the percentage required by
the standard. If the jury members do not recognize the ICE control
sound with the specificity required in the standard, the jury results
must be discarded and the test invalidated. If the required percentage
of jurors found both the candidate sound and ICE control sound to be
recognizable as a motor vehicle in operation at the required
recognition rates, the manufacturer would be able to certify the
vehicle to the pedestrian alert standard.
IX. NHTSA's Role in the Development of a Global Technical Regulation
On June 25, 1998, the United States signed the 1998 Global
Agreement, which entered into force on August 25, 2000. This agreement
was negotiated under the auspices of the United Nations Economic
Commission for Europe (UN/ECE) under the leadership of the U.S., the
European Community (EC) and Japan. The 1998 Agreement provides for the
establishment of Global Technical Regulations (GTRs) regarding the
safety, emissions, energy conservation and theft prevention of wheeled
vehicles, equipment and parts. By establishing GTRs under the 1998
Agreement, the Contracting Parties seek to pursue harmonization in
motor vehicle regulations not only at the national and regional levels,
but worldwide as well.
As a general matter, governments, vehicle manufacturers, and
ultimately, consumers, both here and abroad, can expect to achieve cost
savings through the formal harmonization of differing sets of standards
when the contracting parties to the 1998 Global Agreement implement new
GTRs. Formal harmonization also improves safety by assisting us in
identifying and adopting best safety practices from around the world,
and reducing diverging and unwarranted regulatory requirements. The
harmonization process also allows manufacturers to focus their
compliance and safety resources on regulatory requirements whose
differences government experts have worked to converge as narrowly as
possible. Compliance with a single standard will enhance design
flexibility and allow manufacturers to design vehicles that better meet
safety standards, resulting in safer vehicles. Further, we support the
harmonization process because it allows the agency to leverage scarce
resources by consulting with other governing bodies and international
experts to share data and knowledge in developing modernized testing
and performance standards that enhance safety.
Under the 1998 Agreement, countries voting in favor of establishing
a GTR, agree in principle to begin their internal implementation
processes for adopting the provisions of the GTR, e.g., in the US, to
issue an NPRM or Advanced NPRM, within one year. The ultimate decision
whether or not to adopt the GTR is at each contracting party's
discretion, however, based on its determination that the GTR meets or
does not meet its safety needs. The UN/ECE World Forum for
Harmonization of Vehicle Regulations (WP.29) administers the 1998
Agreement. Four committees coordinate the activities of WP.29: AC.2
manages the coordination of work of WP.29, while AC.3 is the
``Executive Committee'' for the 1998 Agreement. There are also six
permanent subsidiary bodies of WP.29, known as GRs (Groups of
Rapporteurs) that assist WP.29 in researching, analyzing and developing
technical regulations.
At its March 2011 session, WP.29 determined that vehicles propelled
in whole or in part by electric means, present a danger to pedestrians
and consequently adopted Guidelines covering alert sounds for electric
and hybrid vehicles that are closely based on the Japanese Government's
guidelines. The Guidelines were published as an annex to the UNECE
Consolidated Resolution on the Construction of Vehicles (R.E.3).
Considering the international interest and work in this new area of
safety, the US has decided to lead the efforts on the new GTR, with
Japan as co-sponsor, and develop harmonized pedestrian alert sound
requirements for electric and hybrid-electric vehicles under the 1998
Global Agreement. Development of the GTR for pedestrian alert sound has
been assigned to the Group of Experts on Noise (GRB), the group most
experienced with vehicle sound emissions. GRB is in the process of
assessing the safety, environmental and technological concerns to
develop a GTR that leverages expertise and research from around the
world and feedback from consumer groups. The US, along with Japan, is
the co-chair of the informal working group assigned to develop the GTR
and, therefore, will guide the informal working group's development of
the GTR. GRB will meet regularly and report to WP.29 until the expected
establishment of the new GTR in November 2014.
Prime Minister Stephen Harper and President Barack Obama created
the U.S.-Canada Regulatory Cooperation Council (RCC) on February 4,
2011 to increase regulatory cooperation between the United States and
Canada. One of the action items of the RCC is to work to develop joint
plans to address hybrid and electric vehicles and pedestrian safety.
Pursuant to the RCC, the agency has been collaborating with Transport
Canada on areas of research of mutual
[[Page 2849]]
interest regarding sound produced by hybrid and electric vehicles.
X. Analysis of Costs, Benefits, and Environmental Effects
A. Benefits
As stated above in the discussion of the statistical analysis of
safety need done for this rulemaking (see Section V), the use of data
from 16 states cannot be used to directly estimate the national problem
size and, an analysis of pedestrian fatalities is not appropriate for
this rulemaking. The target population analysis will therefore focus on
injuries only.
The PSEA directs NHTSA to establish minimum sound requirements for
EVs and HVs as a means of addressing the increased rate of pedestrian
crashes for these vehicles. In calculating the benefits of this
rulemaking we have assumed that adding sound to EVs and HVs will bring
the pedestrian crash rates for these vehicles in line with the
pedestrian crash rates for ICE vehicles because the minimum sound
requirements in the proposed rule would ensure that EVs and HVs are at
least as detectable to pedestrians as ICE vehicles. This approach
assumes that EVs and HVs have higher pedestrian crash rates than ICE
vehicles because of the differences in sound levels produced by these
vehicles. Therefore, the target population for this rulemaking is the
number of crashes that would be avoided if the crash rate for hybrid
and electric vehicles was the same as the crash rate for ICE vehicles.
No quantifiable benefits are estimated for EVs because we assume that
EV manufacturers would have added alert sounds to their cars in the
absence of this proposed rule and the PSEA.
First, injury estimates from the 2006-2010 National Automotive
Sampling System--General Estimates System (NASS-GES) and 2007 Not in
Traffic Surveillance (NiTS) were used to provide an average estimate
for combined in-traffic and relevant not-in-traffic crashes. In order
to combine the GES and NiTS data in a meaningful way, it was assumed
that the ratio of GES-to-NiTS will be constant for all years 2006 to
2010.
Because both the GES and NiTS databases rely on police reported
crashes, these databases do not accurately reflect all vehicle crashes
involving pedestrians because many of these crashes are not reported to
the police. The agency estimates that the number of unreported crashes
for pedestrians is equal to 100.8 percent of the reported crashes. That
is to say, for every 100 police reported pedestrian crashes, there
exist 100.8 additional unreported pedestrian crashes, for a total of
200.8 crashes.
Table 15 shows the reported and unreported crashes by injury
severity. Only injury counts will be examined for the purpose of
benefits calculations, and as such fatalities and uninjured (MAIS 0)
counts are not included.
Table 15--Quiet Cars Target Population Injuries Reported (GES, NiTS) and Unreported Pedestrians and
Pedalcyclists, by Vehicle
----------------------------------------------------------------------------------------------------------------
MAIS level 1 2 3 4 5 Total 1-5
----------------------------------------------------------------------------------------------------------------
Reported (GES+NiTS) and Unreported Injured Pedestrians
----------------------------------------------------------------------------------------------------------------
Passenger Car (PC)............................ 75,401 12,490 2,561 613 248 91,313
Light Trucks & Vans (LTV)..................... 51,761 8,627 1,771 423 171 62,753
-----------------------------------------------------------------
Total Light Vehicles (PC+LTV)............. 127,163 21,116 4,332 1,037 419 154,067
----------------------------------------------------------------------------------------------------------------
Reported (GES+NiTS) and Unreported Injured Pedalcyclists
----------------------------------------------------------------------------------------------------------------
Passenger Car (PC)............................ 43,795 6,329 1,105 247 88 51,564
Light Trucks & Vans (LTV)..................... 28,840 4,184 730 162 58 33,974
-----------------------------------------------------------------
Total Light Vehicles (PC+LTV)............. 72,635 10,513 1,835 409 146 85,538
----------------------------------------------------------------------------------------------------------------
The estimates in Table 15 are based on the current make-up of the
fleet for all propulsion types. This means that the total target
population described above across 2006 to 2010 is not only the result
of 100% of the combined sales of all vehicle propulsion types, but also
it is assumed to be equal to 100.67% of the injuries resulting from a
fleet comprised of only ICE vehicles (due to the increased rate of
these incidents for EVs and HVs). The estimated injuries in Table 16
are created by combining the percentage of annual sales of hybrid and
electric vehicles with the odds ratio of 1.19, representing the
increased risk of an HV being involved in a pedestrian crash, and the
odds ratio of 1.44, representing the increased risk of an HV being
involved in a pedalcyclist crash.\121\ Thus, when considering
pedestrians injured by MY2016 vehicles and assuming these pedestrian
and pedalcyclist crashes occurred because the pedestrians and
pedalcyclists failed to detect these vehicles by hearing, the
rulemaking is responsible for the 1,223 injury difference between that
theoretical ICE-only fleet (153,271 injuries) and the estimated
lifetime injuries from the MY2016 fleet (154,494). When considering
pedalcyclists injured by MY2016 vehicles, the rulemaking is responsible
for the 1,567 injury difference between that theoretical fleet (84,516
injuries) and the estimated lifetime injuries from the MY2016 fleet
(86,084). The rule would also reduce 5 pedestrian injuries over the
lifetime of the MY 2016 fleet of LSVs and 5 pedalcyclist injuries over
the lifetime of the MY 2016 fleet of LSVs.
---------------------------------------------------------------------------
\121\ See footnote 42.
[[Page 2850]]
Table 16--Enhanced Injury Rate (EIR) for Pedestrians for 2016 Model Year \122\
--------------------------------------------------------------------------------------------------------------------------------------------------------
EVs + Injuries Injuries
Mild Strong fuel cell ICEs Total assuming assuming
hybrids hybrids (percent) (percent) 100% ICE predicted Benefits
(percent) (percent) (percent) fleet fleet
--------------------------------------------------------------------------------------------------------------------------------------------------------
Passenger Car................................................... 4.46 5.79 0.50 90.18 100.92 90,706 91,545 839
Light Trucks & Vans............................................. 5.62 3.85 0.04 91.11 100.61 62,565 62,949 384
---------------------------------------------------------------------------------------
Total....................................................... ......... ......... ......... ......... ......... 153,271 154,494 1,223
--------------------------------------------------------------------------------------------------------------------------------------------------------
Enhanced Injury Rate (EIR) for Pedestrians for 2016 Model Year \123\
--------------------------------------------------------------------------------------------------------------------------------------------------------
Injuries Injuries
Mild Strong EVs + ICEs Total assuming assuming
hybrids hybrids fuel cell (percent) (percent) 100% ICE predicted Benefits
(percent) (percent) (percent) fleet fleet
--------------------------------------------------------------------------------------------------------------------------------------------------------
Passenger Car................................................... 4.46 7.01 0.50 90.18 102.14 50,777 51,865 1,087
Light Trucks & Vans............................................. 5.62 4.66 0.04 91.11 101.42 33,739 34,219 480
---------------------------------------------------------------------------------------
Total....................................................... ......... ......... ......... ......... ......... 84,516 86,084 1,567
--------------------------------------------------------------------------------------------------------------------------------------------------------
The agency has not estimated the benefits associated with applying
the requirements of this proposal to hybrid and electric vehicles with
a GVWR over 4,536 kg (10,000 pounds), and electric motorcycles because
the agency was unable to determine separate pedestrian collision rates
for these vehicle types. The agency is unsure whether using the
difference in rates between light ICE vehicle pedestrian crashes and
light HV and EV pedestrian crashes would be an appropriate means of
calculating the benefits of applying the requirements of this proposal
to these other classes of vehicles. As discussed in the Preliminary
Regulatory Impact Analysis (PRIA), MAIS injury levels are converted to
dollar amounts. The benefit of reducing 2,800 pedestrian and
pedalcyclist injuries, or 35 equivalent lives saved, is estimated to be
$ 178.7M at the 3 percent discount rate and $146.3M at the 7 percent
discount rate for the light vehicle and LSV fleet.
---------------------------------------------------------------------------
\122\ Table values may be off by one due to rounding.
\123\ Table values may be off by one due to rounding.
---------------------------------------------------------------------------
The agency calculated the benefits of this proposal by calculating
the ``injury differences'' between ICE vehicles and HVs. The ``injury
differences'' assume that the difference between crash rates for ICEs
and non-ICEs is explained wholly by the difference in sounds produced
by these two vehicle types of vehicles and the failure of pedestrians
and pedalcyclists to detect these vehicles by hearing. It is possible
that there are other factors responsible for some of the difference in
crash rates, which would mean that adding sound to hybrid and electric
vehicles would not reduce pedestrian and pedalcyclist crash rates for
hybrids to that of ICE vehicles. NHTSA also assumes the sound added to
hybrid and electric vehicles will be as effective in providing warning
to pedestrians as the sound produced by a vehicle's ICE. NHTSA seeks
comment on the underlying assumptions used in calculating the benefits
of this proposal.
In addition to the benefits in injury reduction due to this
proposal there is also the benefit to blind individuals of continued
independent mobility. The increase in navigational ability resulting
from this proposal is hard to quantify and thus this benefit is
mentioned but not assigned a specific productivity or quality of life
monetization. By requiring alert sounds on hybrid and electric
vehicles, blind pedestrians will be able to navigate roads as safely
and effectively as if the fleet were entirely ICE vehicles. The benefit
of independent navigation leads to the ability to travel independently
and will, therefore, also lead to increased employment and the ability
to live independently.
B. Costs
Based on Ward's Automotive Yearbook, 2011 there were 306,882 hybrid
engine installations in light vehicles (74% were in passenger cars and
26% were in light trucks) in MY 2010 (these were 2.8% of sales in 2010
of 10,796,533). There were a small number of electric vehicles (an
estimated 852 from NHTSA's data not Ward's) sold in 2010, the larger
sellers (GM Volt and Nissan Leaf) were introduced later. The Annual
Energy Outlook (AEO) for 2011 provides estimates of the fleet by year
for hybrid and electric vehicles.\124\ The number of vehicles that the
agency projects will be required to meet the standard is shown in TABLE
17.
---------------------------------------------------------------------------
\124\ In calculating the costs of this proposal the agency only
included those vehicles that can operate solely via the vehicle's
electric motor. The agency did not included ``micro hybrids'' whose
ICE is always running when the vehicle is motion when calculating
the costs of this proposal.
Table 17--Estimated/Predicted Hybrid and Electric Vehicle Sales Proposed To Be Required To Provide an Alert
Sound
----------------------------------------------------------------------------------------------------------------
Estimated 2010 Predicted 2016 2016 sales for
sales sales costing purposes
----------------------------------------------------------------------------------------------------------------
Low-Speed Vehicles..................................... 1,500 2,500 2,500
Light Vehicles Electric................................ 852 46,200 .................
Fuel Cells............................................. 0 2,900 .................
Light Vehicles Hybrid.................................. 289,282 671,300 671,300
[[Page 2851]]
Light Vehicles Total................................... 290,143 720,400 .................
Medium and Heavy Truck................................. 2,000 21,500 21,500
Buses.................................................. 3,000 5,000 5,000
Motorcycles............................................ 1,500 5,000 5,000
--------------------------------------------------------
Total Sales........................................ 298,143 754,400 705,300
----------------------------------------------------------------------------------------------------------------
The Nissan Leaf and other fully electric vehicles come equipped
with an alert sound system. Based on what manufacturers have
voluntarily provided in their fully electric vehicles, the agency
assumes that fully electric vehicles and hydrogen fuel cell vehicles
would have provided an alert sound system on their own and, therefore,
for costing purposes we assumed that this is not a cost of the
proposal. However, those vehicles' alert sounds may not meet the
proposed standard and, the rulemaking may force a change in a
manufacturer's sound alert. We assume that manufacturers would incur no
incremental cost for that change, as it is anticipated to be a simple
software modification. Thus, the incremental number of light vehicles
that have to add an alert sound system for costing purposes for MY 2016
is 720,400-46,200-2,900 = 671,300.
Based on informal discussions with suppliers and industry experts,
the agency estimates that the total consumer cost for a system that
produces sounds meeting the requirement of this proposal is around $30
per vehicle. This estimate includes the cost of a dynamic range speaker
system that is protected from the elements and attached with mounting
hardware and wiring to both power the speaker and receive signal inputs
and a digital signal processor that receives information from the
vehicle regarding vehicle operating status (to produce sounds dependent
upon vehicle status). We seek comment of the cost of a speaker system
used to produce sounds meeting the requirements contained in this
proposal. We assume there will be no other structural changes or
installation costs associated with complying with the rule's
requirements and seek comment on this assumption. We believe the same
system can be used for both low-speed vehicles and light vehicles. We
estimate that the added weight of the system would increase fuel costs
for light vehicles around $5 over the life time of the vehicle.
Table 18--Total Costs
----------------------------------------------------------------------------------------------------------------
3% Discount rate 7% Discount rate
----------------------------------------------------------------------------------------------------------------
Passenger Cars Per Vehicle............ $34.73 $33.83.
Light Trucks Per Vehicle.............. $35.33 $34.23.
All Passenger Cars.................... $15.27 Million $14.87 Million.
All Light Trucks...................... $8.19 Million $7.93 Million.
Total for Light Vehicles.............. $23.45 Million $22.80 Million.
Low-speed Vehicles Per Vehicle........ $30.24 $30.24.
Low-speed Vehicles Total Cost......... $0.08 $0.08.
Partial Costs for All Medium/Heavy $1.48 Million $1.48 Million.
Trucks, Buses, and Motorcycles.
-------------------------------------------------------------------------
Total............................. $25.00 Million $24.36 Million.
----------------------------------------------------------------------------------------------------------------
In addition to the quantifiable costs discussed above, there may be
a cost of adding sound to quiet vehicles to owners who value quiet.
NHTSA does not know how to put a value on quiet for a driver's own
vehicle. We are also unsure of the extent to which the added sound will
reach the passenger compartment of the vehicle and request comment on
this issue. Nor does the agency know how to put a value or a cost on
the increase in noise that the alert sound from other vehicles would
produce.
As explained further in the Draft Environmental Assessment (Draft
EA) that the agency has analyzed the potential environmental effects of
this rulemaking, we expect that the increase in noise from the alert
sound will be no louder than that from an average ICE vehicle and that
there will not be an appreciable aggregate sound from these vehicles.
Given the low increase in overall noise caused by this rule, we expect
that any costs that may exist due to added sound will be minimal.
Nevertheless, we ask commenters whether the increase in noise brought
about by this proposal has any cost and how to value it. NHTSA also
seeks comment on whether manufacturers are taking any actions beyond
adding speakers and typical noise reduction efforts in response to
adding sound to quiet vehicles and the cost of such actions. NHTSA has
not found any way to value the increase in noise, and, thus it is a
non-quantified cost.
C. Comparison of Costs and Benefits
Because we have calculated the costs of this rule to all applicable
hybrid and electric vehicles, but not calculated the benefits of
applying this proposal to the medium and heavy duty trucks and buses
and electric motorcycles the comparison of costs and benefits only
takes into account light vehicles and low-speed vehicles. Comparison of
costs and benefits expected due to this rule provides a cost of $0.83
to $0.99 million per equivalent life saved across the 3 and 7 percent
discount levels. This falls under NHTSA's value of a statistical life
of $6.3M, and therefore this rulemaking is assumed to be cost
beneficial. Since the lifetime benefits of MY2016 light vehicles is
expected to be between $145.8M and $178M, the net impact of the rule is
a positive one, even with the
[[Page 2852]]
estimated $20.1M required to install speakers \125\ and $3M in lifetime
fuel costs.
---------------------------------------------------------------------------
\125\ Based on the assumption in this analysis that
manufacturers will install speakers to meet the proposal.
Table 19--Discounted Benefits MY 2016, 2010$
------------------------------------------------------------------------
Total
3% Discount monetized Total ELS
benefits
------------------------------------------------------------------------
TOTAL PED + CYC
------------------------------------------------------------------------
(PC)......................................... $122,747,591 19.41
(LTV)........................................ 55,265,495 8.74
--------------------------
Total...................................... 178,013,086 28.15
------------------------------------------------------------------------
Total
7% Discount monetized Total ELS
benefits
------------------------------------------------------------------------
TOTAL PED + CYC
------------------------------------------------------------------------
(PC)......................................... $102,366,052 16.19
(LTV)........................................ 43,422,889 6.87
--------------------------
Total...................................... 145,788,941 23.06
------------------------------------------------------------------------
Table 20--Total Costs 2010$
------------------------------------------------------------------------
Total
3% Discount cost/veh Total costs
------------------------------------------------------------------------
(PC)......................................... $34.70 $15,253,618
(LTV)........................................ 35.30 8,178,471
--------------------------
Total...................................... 34.91 23,432,088
------------------------------------------------------------------------
Total
7% Discount cost/veh Total costs
------------------------------------------------------------------------
(PC)......................................... $33.80 $14,857,991
(LTV)........................................ 34.20 7,923,618
--------------------------
Total...................................... 33.94 22,781,608
------------------------------------------------------------------------
Table 21--Net Impacts 2010$
----------------------------------------------------------------------------------------------------------------
Net costs/ELS
3% Discount Net impact/veh Net impact (in $M)
----------------------------------------------------------------------------------------------------------------
(PC)................................................... $244.53 $107,493,974 0.79
(LTV).................................................. 203.24 47,087,024 0.94
--------------------------------------------------------
Total.............................................. 230.28 154,580,998 0.83
----------------------------------------------------------------------------------------------------------------
Net costs/ELS
7% Discount Net impact/veh Net impact (in $M)
----------------------------------------------------------------------------------------------------------------
(PC)................................................... $199.07 $87,508,062 0.92
(LTV).................................................. 153.22 35,499,271 1.15
--------------------------------------------------------
Total.............................................. 183.25 123,007,333 0.99
----------------------------------------------------------------------------------------------------------------
The net impact of this proposal to LSVs is also expected to be
positive. The net benefits of the minimum sound requirements for these
vehicles is $662,971 at the 3 percent discount rate and $542,959 at the
7 percent discount rate. Thus, the total net impact of the rule
considering both the MY2016 light vehicle and LSV fleet is positive.
---------------------------------------------------------------------------
\126\ Scaled benefits and costs for low speed vehicles are
estimated directly proportional to light vehicles based on sales.
Scaled costs include both installation costs for the system and fuel
costs.
Table 22--Costs and Scaled Benefits for LSVs, MY2016 \126\
--------------------------------------------------------------------------------------------------------------------------------------------------------
Scaled
Sales ratio Scaled Scaled benefits
Discount rate LSV to light Sales Scaled costs injuries Scaled ELS benefits minus scaled
vehicle (undisc.) costs
--------------------------------------------------------------------------------------------------------------------------------------------------------
3%...................................... 0.37% 2,500 $87,268 10.39 0.1049 $662,971 $575,703
7%...................................... 0.37% 2,500 84,845 10.39 0.0859 542,959 458,114
--------------------------------------------------------------------------------------------------------------------------------------------------------
D. Environmental Effects
The agency has prepared a Draft Environmental Assessment (Draft EA)
to analyze and disclose the potential environmental impacts of a
reasonable range of potential minimum sound requirements for HVs and
EVs, including a preferred alternative. The alternatives the agency
analyzed include a No Action Alterative, under which the agency would
not establish any minimum sound requirements for EVs/HVs, and two
action alternatives. Under Alternative 2, which is the Preferred
Alternative and is equivalent to the agency's proposal, the agency
would require a sound addition at speeds at or below 30 km/h and would
require that covered vehicles produce sound at the stationary but
active operating condition. Under Alternative 3, the agency would
require a minimum sound pressure level of 48 A-weighted dB for speeds
at or below 20 km/h; there would be no sound requirement when the
vehicle is stationary.
In the Draft EA, NHTSA separately analyzed the projected
environmental impacts of each of the three alternatives in both urban
and non-urban environments because differences in population, vehicle
speeds, and deployment of EVs/HVs in these areas could affect the
potential environmental impacts. National Household Travel Survey data
for 2009 shows that non-urban households account for 31 percent of all
vehicle miles traveled (VMT) but just 14 percent of VMT associated with
trips at an average speed of less than 20 km/h, indicating that these
households spend a much smaller percent of travel time at slow speeds
associated with congested traffic than do households in urban areas.
The Draft EA estimates the direct and indirect impacts of the
alternatives in both urban and non-urban areas by taking into
[[Page 2853]]
account the higher percentage of total VMT that takes place in non-
urban areas, the lower percentage of VMT traveled at slow speeds in
non-urban areas, and the lower percentage of EV/HV sales expected in
non-urban areas.
In the Draft EA, NHTSA estimated the amount of total annual U.S.
passenger vehicle driving time spent in the stationary but active
operating condition, at speeds up to 20 km/h, and at speeds between 20
and 30 km/h. Using forecasts of EV/HV deployment levels in 2035, NHTSA
projected the percentage of total U.S. light duty driving hours that
would be impacted by the standards (e.g., vehicles driven at speeds
that would enable the alert sound). Based on these assumptions, NHTSA
projects that under Alternative 2 (the Preferred Alternative), 2.3
percent of all urban and 0.3 percent of all non-urban light vehicle
travel hours would be affected by the minimum sound requirements in
2035. Under Alternative 3, 0.9 percent of all urban and 0.1 percent of
all non-urban light vehicle travel hours would be affected by the
minimum sound requirements in 2035.
The agency's analysis also shows that in either urban or non-urban
environments, assuming EV/HV deployment levels of either 10 percent and
20 percent, the agency's Preferred Alternative would have negligible to
minimal effects on overall community noise levels. Under the Preferred
Alternative, in a simulated high-traffic condition, the agency found a
difference in sound level of no greater than 0.3 dB(A), as measured by
a receiver 7.5 meters from a roadway, at all speeds and under all
conditions compared to the No Action Alternative. Even if EVs/HVs were
to reach 50 percent deployment, Alternative 2 is projected to amount to
a maximum difference of 0.9 dB above the sound level under the No
Action Alternative in non-urban environments and 0.7 dB in urban
environments. Because differences in sound pressure of less than 3 dB
are generally not noticeable by humans, the environmental impacts of
this proposal are expected to be negligible. Although sound level
differences are greater for single vehicle pass-by events the
difference would be similar to the existing variation that results from
differences between ICE vehicle models. Thus, although the individual
event may be noticeable, overall the noticeable noise levels in the
case of single-car pass-by are considered to cause only a minor impact.
XI. Regulatory Notices and Analyses
Executive Order (E.O.) 12866 (Regulatory Planning and Review), E.O.
13563, and DOT Regulatory Policies and Procedures
The agency has considered the impact of this rulemaking action
under E.O. 12866, E.O. 13563, and the Department of Transportation's
regulatory policies and procedures. This action was reviewed by the
Office of Management and Budget under E.O. 12866. This action is
``significant'' under the Department of Transportation's regulatory
policies and procedures (44 FR 11034; February 26, 1979).
This action is significant because it is the subject of
congressional interest and because it is a mandate under the PSEA. The
agency has prepared and placed in the docket a PRIA.
We estimate the total fuel and installation costs of this proposal
to the light EV, HV and LSV fleet to be $23.5M at the 3 percent
discount rate and $22.9M at the 7 percent discount rate. The estimated
total installation cost for hybrid and electric heavy and medium duty
trucks and buses and electric motorcycles is $1.48M meaning that the
total costs for this rule are between $25 and $24.36 million, depending
on the discount rate. We have only calculated the benefits of this
proposal for light EVs, HVs and LSVs because we do not have crash rates
for hybrid and electric heavy and medium duty trucks and buses and
electric motorcycles. We estimate that the impact of this proposal in
pedestrian and pedacyclist injury reduction will be 28.15 equivalent
lives saved at the 3 percent discount rate and 23.06 equivalent lives
saved at the 7 percent discount rate. The benefits of this proposal for
the light EV and HV and LSV fleet are $178.7M at the 3 percent discount
rate and $146.3M at the 7 percent discount rate. Thus, this action is
also significant because it has an annual economic impact greater than
$100 million.
Executive Order 13609: Promoting International Regulatory Cooperation
The policy statement in section 1 of Executive Order 13609
provides, in part:
The regulatory approaches taken by foreign governments may
differ from those taken by U.S. regulatory agencies to address
similar issues. In some cases, the differences between the
regulatory approaches of U.S. agencies and those of their foreign
counterparts might not be necessary and might impair the ability of
American businesses to export and compete internationally. In
meeting shared challenges involving health, safety, labor, security,
environmental, and other issues, international regulatory
cooperation can identify approaches that are at least as protective
as those that are or would be adopted in the absence of such
cooperation. International regulatory cooperation can also reduce,
eliminate, or prevent unnecessary differences in regulatory
requirements.
NHTSA requests public comment on whether (a) ``regulatory approaches
taken by foreign governments'' concerning the subject matter of this
rulemaking and (b) the above policy statement have any implications for
this rulemaking.
National Environmental Policy Act
Concurrently with this NPRM, NHTSA is releasing a Draft EA, pursuant to
the National Environmental Policy Act, 42 U.S.C. 4321-4347, and
implementing regulations issued by the Council on Environmental Quality
(CEQ), 40 CFR part 1500, and NHTSA, 49 CFR part 520. NHTSA prepared the
Draft EA to analyze and disclose the potential environmental impacts of
the proposed minimum sound requirements for HVs and EVs and a range of
alternatives. The Draft EA analyzes direct, indirect, and cumulative
impacts and analyzes impacts in proportion to their significance.
Because this proposal would increase the amount of sound produced
by a certain segment of the vehicle fleet, the Draft EA considers the
possible impacts of increased ambient noise levels on both urban and
rural environments. The Draft EA also describes potential environmental
impacts to a variety of resources. The resources that may be affected
by the proposed action and alternatives include biological resources,
noise, and environmental justice.
The agency's analysis in the Draft EA shows that in either urban or
non-urban environments, assuming EV/HV deployment levels of either 10
percent and 20 percent, the agency's Preferred Alternative would have
negligible to minimal effects on overall community noise levels. Even
if EVs/HVs were to reach 50 percent deployment, the agency's Preferred
Alternative is projected to amount to a maximum difference of 0.9 dB
above the sound level under the No Action Alternative in non-urban
environments and 0.7 dB in urban environments. Because differences in
sound pressure of less than 3 dB are generally not noticeable by
humans, the environmental impacts of this proposal are expected to be
negligible.
For additional information on NHTSA's NEPA analysis, please see the
Draft EA.
[[Page 2854]]
Regulatory Flexibility Act
Pursuant to the Regulatory Flexibility Act (5 U.S.C. Sec. 601 et
seq., as amended by the Small Business Regulatory Enforcement Fairness
Act (SBREFA) of 1996), whenever an agency is required to publish a
notice of rulemaking for any proposed or final rule, it must prepare
and make available for public comment a regulatory flexibility analysis
that describes the effect of the rule on small entities (i.e., small
businesses, small organizations, and small governmental jurisdictions).
The Small Business Administration's regulations at 13 CFR part 121
define a small business, in part, as a business entity ``which operates
primarily within the United States.'' \127\ No regulatory flexibility
analysis is required if the head of an agency certifies the rule will
not have a significant economic impact on a substantial number of small
entities. SBREFA amended the Regulatory Flexibility Act to require
Federal agencies to provide a statement of the factual basis for
certifying that a proposal will not have a significant economic impact
on a substantial number of small entities.
---------------------------------------------------------------------------
\127\ 13 CFR 121.105(a).
---------------------------------------------------------------------------
I hereby certify that this proposed rule would not have a
significant economic impact on a substantial number of small entities.
We believe that the rulemaking would not have a significant economic
impact on the small vehicle manufacturers because the systems are not
technically difficult to develop or install and the cost of the systems
($30) is small in proportion to the overall vehicle cost for most small
vehicle manufacturers.
This proposal would directly affect motor vehicle manufacturers and
final-stage manufacturers. The majority of motor vehicle manufacturers
will not qualify as a small business. There are five manufacturers of
light hybrid and electric vehicles that would be subject to the
requirements of this proposal that are small businesses.\128\
Similarly, there are several manufacturers of low-speed vehicles\129\
and electric motorcycles that are small businesses.
---------------------------------------------------------------------------
\128\ CODA, Fisker Automotive Inc., Via, Phoenix, and Tesla.
However, it is our view that the manufacturers of electric vehicles
would face little costs due to this rule because they would have
installed alert sounds in their vehicles without this proposed rule.
\129\ In the low-speed vehicle group there are Columbia ParCar
Corp., Club Car, LLC, Miles Electric Vehicles LLC, STAR Electric Car
Sales, Tomberlin, Wheego Electric Cars, Inc., Wildfire, GTT Electric
and others.
---------------------------------------------------------------------------
We believe there are very few manufacturers of heavy trucks in the
United States which can be considered small businesses. The agency is
aware that many manufacturers of medium duty trucks are small
businesses. The agency is aware of at least two small manufacturers who
are producing electric trucks with a GVWR over 10,000 lb.\130\ In
addition to the two manufacturers of medium duty electric vehicles
identified by the agency, we believe that there may be other small
manufacturers who are currently producing these vehicles.
---------------------------------------------------------------------------
\130\ Boulder Electric Vehicle and Smith Electric Vehicles are
producing or have plans to produce electric vehicles with a GVWR
over 10,000 lb.
---------------------------------------------------------------------------
NHTSA believes there are approximately 37 bus manufacturers in the
United States. Of these, 27 bus manufacturers are large business and 10
are small businesses. Three of these small manufacturers produce
electric buses--E-bus Inc., Enova Systems, and Gillig Corporation.
Because the PSEA applies to all motor vehicles (except trailers) in
its mandate to reduce quiet vehicle collisions with pedestrians, all of
these small manufacturers that produce hybrid or electric vehicles are
affected by the requirements in today's final rule. However, the
economic impact upon these entities will not be significant for the
following reasons.
(1) The cost of the systems ($30) is a small proportion of the
overall vehicle cost for even the least expensive electric vehicles.
(2) This proposal would provide a three year lead-time and would
allow small volume manufacturers the option of waiting until the end of
the phase-in (September 1, 2018) to meet the minimum sound
requirements.
Executive Order 13132 (Federalism)
NHTSA has examined today's proposed rule pursuant to Executive
Order 13132 (64 FR 43255, August 10, 1999) and concluded that no
additional consultation with States, local governments or their
representatives is mandated beyond the rulemaking process. The agency
has concluded that the rulemaking would not have sufficient federalism
implications to warrant consultation with State and local officials or
the preparation of a federalism summary impact statement. The proposed
rule would not have ``substantial direct effects on the States, on the
relationship between the national government and the States, or on the
distribution of power and responsibilities among the various levels of
government.''
NHTSA rules can preempt in two ways. First, the National Traffic
and Motor Vehicle Safety Act contains an express preemption provision:
When a motor vehicle safety standard is in effect under this chapter, a
State or a political subdivision of a State may prescribe or continue
in effect a standard applicable to the same aspect of performance of a
motor vehicle or motor vehicle equipment only if the standard is
identical to the standard prescribed under this chapter. 49 U.S.C.
Sec. 30103(b)(1). It is this statutory command by Congress that
preempts any non-identical State legislative and administrative law
addressing the same aspect of performance.
The express preemption provision described above is subject to a
savings clause under which ``[c]ompliance with a motor vehicle safety
standard prescribed under this chapter does not exempt a person from
liability at common law.'' (49 U.S.C. Sec. 30103(e)). Pursuant to this
provision, State common law tort causes of action against motor vehicle
manufacturers that might otherwise be preempted by the express
preemption provision are generally preserved. However, the Supreme
Court has recognized the possibility, in some instances, of implied
preemption of such State common law tort causes of action by virtue of
NHTSA's rules, even if not expressly preempted. This second way that
NHTSA rules can preempt is dependent upon there being an actual
conflict between an FMVSS and the higher standard that would
effectively be imposed on motor vehicle manufacturers if someone
obtained a State common law tort judgment against the manufacturer,
notwithstanding the manufacturer's compliance with the NHTSA standard.
Because most NHTSA standards established by an FMVSS are minimum
standards, a State common law tort cause of action that seeks to impose
a higher standard on motor vehicle manufacturers will generally not be
preempted. However, if and when such a conflict does exist--for
example, when the standard at issue is both a minimum and a maximum
standard--the State common law tort cause of action is impliedly
preempted. See Geier v. American Honda Motor Co., 529 U.S. 861 (2000).
Pursuant to Executive Order 13132 and 12988, NHTSA has considered
whether this proposed rule could or should preempt State common law
causes of action. The agency's ability to announce its conclusion
regarding the preemptive effect of one of its rules reduces the
likelihood that preemption will be an issue in any subsequent tort
litigation.
To this end, the agency has examined the nature (e.g., the language
and
[[Page 2855]]
structure of the regulatory text) and objectives of today's proposed
rule and finds that this proposed rule, like many NHTSA rules, would
prescribe only a minimum safety standard. As such, NHTSA does not
intend that this proposed rule would preempt state tort law that would
effectively impose a higher standard on motor vehicle manufacturers
than that established by today's proposed rule. Establishment of a
higher standard by means of State tort law would not conflict with the
minimum standard proposed here. Without any conflict, there could not
be any implied preemption of a State common law tort cause of action.
Executive Order 12988 (Civil Justice Reform)
With respect to the review of the promulgation of a new regulation,
section 3(b) of Executive Order 12988, ``Civil Justice Reform'' (61 FR
4729; Feb. 7, 1996), requires that Executive agencies make every
reasonable effort to ensure that the regulation: (1) clearly specifies
the preemptive effect; (2) clearly specifies the effect on existing
Federal law or regulation; (3) provides a clear legal standard for
affected conduct, while promoting simplification and burden reduction;
(4) clearly specifies the retroactive effect, if any; (5) specifies
whether administrative proceedings are to be required before parties
file suit in court; (6) adequately defines key terms; and (7) addresses
other important issues affecting clarity and general draftsmanship
under any guidelines issued by the Attorney General. This document is
consistent with that requirement.
Pursuant to this Order, NHTSA notes as follows. The issue of
preemption is discussed above. NHTSA notes further that there is no
requirement that individuals submit a petition for reconsideration or
pursue other administrative proceedings before they may file suit in
court.
Unfunded Mandates Reform Act
Section 202 of the Unfunded Mandates Reform Act of 1995 (UMRA)
requires federal agencies to prepare a written assessment of the costs,
benefits, and other effects of proposed or final rules that include a
Federal mandate likely to result in the expenditure by State, local, or
tribal governments, in the aggregate, or by the private sector, of more
than $100 million annually (adjusted for inflation with base year of
1995). Adjusting this amount by the implicit gross domestic product
price deflator for 2010 results in $136 million (110.659/81.536 =
1.36).
As noted previously, the agency has prepared a detailed economic
assessment in the PRE. We estimate the annual total fuel and
installation costs of this proposal to the light EV, HV and LSV fleet
to be $23.5M at the 3 percent discount rate and $22.9M at the 7 percent
discount rate. The estimated total installation cost for hybrid and
electric heavy and medium duty trucks and buses and electric
motorcycles is $1.48M. Therefore, this proposal is not expected to
result in the expenditure by State, local, or tribal governments, in
the aggregate, or by the private sector, of more than $136M annually.
Paperwork Reduction Act
Under the Paperwork Reduction Act of 1995, a person is not required
to respond to a collection of information by a Federal agency unless
the collection displays a valid OMB control number. The NPRM contains
reporting requirements so that the agency can determine if
manufacturers comply with the phase in schedule.
In compliance with the PRA, this notice announces that the
Information Collection Request (ICR) abstracted below has been
forwarded to OMB for review and comment. The ICR describes the nature
of the information collections and their expected burden. This is a
request for new collection.
Agency: National Highway Traffic Safety Administration (NHTSA).
Title: 49 CFR Part 575.141, Minimum Sound Requirements for Hybrid
and Electric Vehicles.
Type of Request: New collection.
OMB Clearance Number: Not assigned.
Form Number: The collection of this information will not use any
standard forms.
Requested Expiration Date of Approval: Three years from the date of
approval.
Summary of the Collection of Information
This collection would require manufacturers of passenger cars,
multipurpose passenger vehicles, trucks, buses, motorcycles and low
speed vehicles subject to the phase-in schedule to provide motor
vehicle production data for the following three years: September 1,
2015 to August 31, 2016; September 1, 2016 to August 31, 2017; and
September 1, 2017 to August 31, 2018.
Description of the Need for the Information and Use of the Information
The purpose of the reporting requirements will be to aid NHTSA in
determining whether a manufacturer has complied with the requirements
of Federal Motor Vehicle Safety Standard No. 141, Minimum Sound for
Hybrid and Electric Vehicles, during the phase-in of those
requirements.
Description of the Likely Respondents (Including Estimated Number, and
Proposed Frequency of Response to the Collection of Information)
The respondents are manufacturers of hybrid and electric passenger
cars, multipurpose passenger vehicles, trucks, buses, motorcycles and
low-speed vehicles. The agency estimates that there are about 73 such
manufacturers. The proposed collection would occur one per year.
Estimate of the Total Annual Reporting and Recordkeeping Burden
Resulting From the Collection of Information
NHTSA estimates that the total annual burden is 146 hours (2 hours
per manufacturer per year).
Comments are invited on:
Whether the collection of information is necessary for the
proper performance of the functions of the Department, including
whether the information will have practical utility.
Whether the Department's estimate for the burden of the
information collection is accurate.
Ways to minimize the burden of the collection of
information on respondents, including the use of automated collection
techniques or other forms of information technology.
A comment to OMB is most effective if OMB receives it within 30
days of publication. Send comments to the Office of Information and
Regulatory Affairs, Office of Management and Budget, 725 17th Street,
NW., Washington, DC 20503, Attn: NHTSA Desk Officer. PRA comments are
due within 30 days following publication of this document in the
Federal Register.
The agency recognizes that the collection of information contained
in today's final rule may be subject to revision in response to public
comments and the OMB review.
The procedure for the evaluation of vehicle sounds by human
subjects contained in Section VIII.G of this proposal would also
constitute a collection of information for the purposes of the PRA. If
the agency decides to adopt the procedure described in Section VIII.G
in the final rule then agency would submit an ICR to OMB before the
final rule is issued in compliance with the PRA.
[[Page 2856]]
Executive Order 13045
Executive Order 13045 \131\ applies to any rule that: (1) Is
determined to be economically significant as defined under E.O. 12866,
and (2) concerns an environmental, health or safety risk that NHTSA has
reason to believe may have a disproportionate effect on children. If
the regulatory action meets both criteria, we must evaluate the
environmental health or safety effects of the proposed rule on
children, and explain why the proposed regulation is preferable to
other potentially effective and reasonably feasible alternatives
considered by us.
---------------------------------------------------------------------------
\131\ 62 FR 19885 (Apr. 23, 1997).
---------------------------------------------------------------------------
This proposed rule would not pose such a risk for children. The
primary effects of this proposal are to ensure that hybrid and electric
vehicles produce enough sound so that pedestrians can detect them. We
expect this rule to reduce the risk of injuries to children and other
pedestrians.
National Technology Transfer and Advancement Act
Section 12(d) of the National Technology Transfer and Advancement
Act (NTTAA) requires NHTSA to evaluate and use existing voluntary
consensus standards in its regulatory activities unless doing so would
be inconsistent with applicable law (e.g., the statutory provisions
regarding NHTSA's vehicle safety authority) or otherwise impractical.
Voluntary consensus standards are technical standards developed or
adopted by voluntary consensus standards bodies. Technical standards
are defined by the NTTAA as ``performance-based or design-specific
technical specification and related management systems practices.''
They pertain to ``products and processes, such as size, strength, or
technical performance of a product, process or material.''
Examples of organizations generally regarded as voluntary consensus
standards bodies include the American Society for Testing and Materials
(ASTM), the Society of Automotive Engineers (SAE), and the American
National Standards Institute (ANSI). If NHTSA does not use available
and potentially applicable voluntary consensus standards, we are
required by the Act to provide Congress, through OMB, an explanation of
the reasons for not using such standards.
The agency uses certain parts of voluntary consensus standard SAE
J2889-1, Measurement of Minimum Noise Emitted by Road Vehicles, in the
test procedure contained in this proposal. SAE J2889-1 only contains
measurement procedures and does not contain any minimum performance
requirements. The agency did not use any voluntary consensus standards
for the minimum acoustic requirements contained in this proposal
because no such voluntary consensus standards exist. The agency added
additional test scenarios other than those contained in SAE J2889-1
because those additional test scenarios address aspects of performance
not covered in that standard. As discussed in Section VII.E.1, the
proposal does not include a procedure for indoor testing because of the
limited availability of indoor test facilities and because test
surfaces for indoor testing are not sufficiently specified.
Executive Order 13211
Executive Order 13211 \132\ applies to any rule that: (1) Is
determined to be economically significant as defined under E.O. 12866,
and is likely to have a significant adverse effect on the supply,
distribution, or use of energy; or (2) that is designated by the
Administrator of the Office of Information and Regulatory Affairs as a
significant energy action. If the regulatory action meets either
criterion, we must evaluate the adverse energy effects of the proposed
rule and explain why the proposed regulation is preferable to other
potentially effective and reasonably feasible alternatives considered
by NHTSA.
---------------------------------------------------------------------------
\132\ 66 FR 28355 (May 18, 2001).
---------------------------------------------------------------------------
The proposed rule seeks to ensure that hybrid and electric vehicles
are detectable by pedestrians. The average weight gain for a light
vehicle is estimated to be 1.5 pounds (based upon a similar waterproof
speaker used for marine purposes), resulting in 2.3 more gallons of
fuel being used over the lifetime of a passenger car and 2.5 more
gallons of fuel being used over the lifetime of a light truck. When
divided by the life time of the vehicle (26 years for passenger cars
and 36 years for light trucks) the yearly increase in fuel consumption
attributed to this proposed rule would be negligible. Therefore, this
proposed rule would not have a significant adverse effect on the use of
energy. Accordingly, this proposed rulemaking action is not designated
as a significant energy action.
Regulation Identifier Number (RIN)
The Department of Transportation assigns a regulation identifier
number (RIN) to each regulatory action listed in the Unified Agenda of
Federal Regulations. The Regulatory Information Service Center
publishes the Unified Agenda in April and October of each year. You may
use the RIN contained in the heading at the beginning of this document
to find this action in the Unified Agenda.
Plain Language
Executive Order 12866 requires each agency to write all rules in
plain language. Application of the principles of plain language
includes consideration of the following questions:
Have we organized the material to suit the public's needs?
Are the requirements in the rule clearly stated?
Does the rule contain technical language or jargon that
isn't clear?
Would a different format (grouping and order of sections,
use of headings, paragraphing) make the rule easier to understand?
Would more (but shorter) sections be better?
Could we improve clarity by adding tables, lists, or
diagrams?
What else could we do to make the rule easier to
understand?
If you have any responses to these questions, please include them
in your comments on this proposal.
Privacy Act
Anyone is able to search the electronic form of all comments
received into any of our dockets by the name of the individual
submitting the comment (or signing the comment, if submitted on behalf
of an organization, business, labor union, etc.). You may review DOT's
complete Privacy Act statement in the Federal Register published on
April 11, 2000 (Volume 65, Number 70; Pages 19477-78) or you may visit
http://www.dot.gov/privacy.html.
Public Participation
How do I prepare and submit comments?
Your comments must be written and in English. To ensure that your
comments are correctly filed in the Docket, please include the docket
number of this document in your comments. Your comments must not be
more than 15 pages long.\133\ We established this limit to encourage
you to write your primary comments in a concise fashion. However, you
may attach necessary additional documents to your comments. There is no
limit on the length of the attachments.
---------------------------------------------------------------------------
\133\ See 49 CFR Sec. 553.21.
---------------------------------------------------------------------------
Please submit your comments by any of the following methods:
[[Page 2857]]
Federal eRulemaking Portal: go to http://www.regulations.gov. Follow the instructions for submitting comments on
the electronic docket site by clicking on ``Help'' or ``FAQ.''
Mail: Docket Management Facility, M-30, U.S. Department of
Transportation, West Building, Ground Floor, Rm. W12-140, 1200 New
Jersey Avenue SE., Washington, DC 20590.
Hand Delivery or Courier: West Building Ground Floor, Room
W12-140, 1200 New Jersey Avenue SE., between 9 a.m. and 5 p.m. Eastern
Time, Monday through Friday, except Federal holidays.
Fax: (202) 493-2251.
If you are submitting comments electronically as a PDF (Adobe)
file, we ask that the documents submitted be scanned using Optical
Character Recognition (OCR) process, thus allowing the agency to search
and copy certain portions of your submissions.\134\
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\134\ Optical character recognition (OCR) is the process of
converting an image of text, such as a scanned paper document or
electronic fax file, into computer-editable text.
---------------------------------------------------------------------------
Please note that pursuant to the Data Quality Act, in order for
substantive data to be relied upon and used by the agency, it must meet
the information quality standards set forth in the OMB and DOT Data
Quality Act guidelines. Accordingly, we encourage you to consult the
guidelines in preparing your comments. OMB's guidelines may be accessed
at http://www.whitehouse.gov/omb/fedreg/reproducible.html. DOT's
guidelines may be accessed at http://dmses.dot.gov/submit/DataQualityGuidelines.pdf.
How can I be sure that my comments were received?
If you submit your comments by mail and wish Docket Management to
notify you upon its receipt of your comments, enclose a self-addressed,
stamped postcard in the envelope containing your comments. Upon
receiving your comments, Docket Management will return the postcard by
mail.
How do I submit acoustic recordings?
If you wish to submit acoustic recordings along with your comments
please sent the recordings to NHTSA at the address given above under
FOR FURTHER INFORMATION CONTACT. If you wish to request confidential
treatment of the records please follow the instructions listed below.
In order to be of use to the agency, NHTSA is requesting that any
recordings submitted to the agency be 16-bit with a sampling frequency
of 44.1 kHz or better and made with a stationary binaural head facing
perpendicular to the vehicle's trajectory. As well as any recording
made using a binaural head, it would be useful to the agency, if
possible, for recordings submitted to include a recording from a
monaural microphone made according to SAE J2889-1. The agency requests
that a Calibration Tone be included in each set of recordings. The
agency also requests that the level and frequency of the Calibration
Tone be indicated, e.g. 94 dB at 1000 Hz.
In order to be of use in the agency's analysis, we request that
idle recordings be at least 30 seconds long and preferably 60 seconds
long. Constant speed pass-by recordings should include at least 15
seconds of approach towards the microphone and at least 5 seconds
departing from the microphone. Ideally the recording will start before
the vehicle is audible. We are requesting the recording of time after
departure so that we have additional data for analysis of tone-to-noise
ratio, Doppler shifts, and Head-Related Transfer Function (HRTF)
effects, but do not need recordings up until the point at which the
vehicle is no longer audible. The agency requests that commenters
identify the distance of vehicle from microphone at start of recording
as well as the distance between the microphone and the vehicle center
line. The agency requests that commenters identify the operating
scenario of the vehicle when the recording was made.
In order to help us with our analysis, we request that commenters
submit information about the make, model and year of the vehicle being
recorded along with the recording. We also request that commenters
identify whether the recording is of an ICE vehicle or an EV/HV
equipped with an alert sound. The agency requests that commenters
submit the minimum A-weighted level and maximum A-weighted level while
using a fast (125 ms exponential) time weighting of the sound produced
by the vehicle along with the recording.
In order to assist the agency in analyzing recordings submitted in
response to the NPRM we request that commenters inform the agency
whether the recording was conducted on an ISO noise pad, in a semi-
anechoic chamber or on a test bench. For outdoor testing it would be
useful for commenters to provide measurements of the air and pavement
temperature, and wind speed at the time of the recording as well as
photographs of the test site if available. For more information about
how the agency collected data for its research please see Chapter
4.1.5, Data Collection Protocol, in the agency's Phase I research
report.
How do I submit confidential business information?
If you wish to submit any information under a claim of
confidentiality, you should submit three copies of your complete
submission, including the information you claim to be confidential
business information, to the Chief Counsel, NHTSA, at the address given
above under FOR FURTHER INFORMATION CONTACT. When you send a comment
containing information claimed to be confidential business information,
you should include a cover letter setting forth the information
specified in our confidential business information regulation.\135\
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\135\ See 49 CFR Sec. 512.
---------------------------------------------------------------------------
In addition, you should submit a copy, from which you have deleted
the claimed confidential business information, to the Docket by one of
the methods set forth above.
Will the agency consider late comments?
We will consider all comments received before the close of business
on the comment closing date indicated above under DATES. To the extent
possible, we will also consider comments received after that date.
Therefore, if interested persons believe that any new information the
agency places in the docket affects their comments, they may submit
comments after the closing date concerning how the agency should
consider that information for the final rule.
If a comment is received too late for us to consider in developing
a final rule (assuming that one is issued), we will consider that
comment as an informal suggestion for future rulemaking action.
How can I read the comments submitted by other people?
You may read the materials placed in the docket for this document
(e.g., the comments submitted in response to this document by other
interested persons) at any time by going to http://www.regulations.gov.
Follow the online instructions for accessing the dockets. You may also
read the materials at the Docket Management Facility by going to the
street address given above under ADDRESSES. The Docket Management
Facility is open between 9 a.m. and 5 p.m. Eastern Time, Monday through
Friday, except Federal holidays.
List of Subjects
49 CFR Part 571
Motor vehicle safety, Reporting and recordkeeping requirements,
Tires.
[[Page 2858]]
49 CFR Part 585
Motor vehicle safety, Reporting and recordkeeping requirements.
Proposed Regulatory Text
For reasons discussed in the preamble, NHTSA proposes to amend 49
CFR part 571 as follows:
PART 571--FEDERAL MOTOR VEHICLE SAFETY STANDARDS
0
1. The authority citation for part 571 continues to read as follows:
Authority: 49 U.S.C. 322, 30111, 30115, 30117, and 30166;
delegation of authority at 49 CFR 1.95.
0
2. In Sec. 571.5, paragraphs (i)(2) and (l)(50) are added to read as
follows:
Sec. 571.5 Matter incorporated by reference.
* * * * *
(i) * * *
(2) ISO 10844:2011 ``Acoustics--Test Surface for Road Vehicle Noise
Measurements,'' into Sec. 571.141.
* * * * *
(l) * * *
(50) SAE Standard J2889-1 SEP2011, ``Measurement of Minimum Noise
Emitted by Road Vehicles,'' the following sections only into Sec.
571.141: S4, Table 1, S5.1, S5.3, S6.1.1, S6.4, S6.5, S7.1.
* * * * *
0
3. Section 571.141 is added to read as follows:
Sec. 571.141 Standard No. 141; Minimum Sound Requirements for Hybrid
and Electric Vehicles.
S1. Scope. This standard establishes performance for pedestrian
alert sounds from motor vehicles.
S2. Purpose. The purpose of this standard is to reduce the number
of deaths and injuries that result from electric and hybrid vehicles
crashes with pedestrians by providing a sound level and sound
characteristics necessary for these vehicles to be detected and
recognized by pedestrians.
S3. Application. This standard applies to--
(a) Electric vehicle passenger cars, multipurpose passenger
vehicles, trucks, buses, motorcycles, and low-speed vehicles;
(b) Passenger cars, multi-purpose passenger vehicles, trucks,
buses, and low-speed vehicles with more than one means of propulsion
for which the vehicle's propulsion system can propel the vehicle in the
normal travel mode in reverse and at least one forward drive gear
without the internal combustion engine operating and;
(c) Motorcycles with more than one means of propulsion for which
the vehicle's propulsion system can propel the vehicle in the normal
travel mode in at least one forward drive gear without the internal
combustion engine operating.
S4. Definitions.
Broadband content means a measureable acoustic signal (greater than
0 A-weighted dB) at all frequencies within a one-third octave band.
Electric vehicle means a motor vehicle with an electric motor as
its sole means of propulsion.
Front plane of the vehicle means a vertical plane tangent to the
leading edge of the vehicle during forward operation.
Fundamental frequency means, for purposes of this regulation, the
lowest frequency of a valid measurement taken in S7.
Rear plane means a vertical plane tangent to the leading edge of
the vehicle when the vehicle is in a condition in which it is capable
of reverse self-mobility.
S5. Requirements. Subject to the phase-in set forth in S9 of this
standard, each vehicle must meet the requirements specified in S5 under
the test conditions specified in S6 and the test procedures specified
in S7 of this standard.
S5.1 Performance Requirements for critical operating scenarios. The
vehicle must satisfy the requirements of this section when tested under
the test conditions of S6 and the test procedures of S7.
S5.1.1 Start up and stationary but activated. When measured
according to the test conditions of S6 and the test procedure of S7.2,
the vehicle must, within 500msec of activation of its starting system,
emit a sound having at least the A-weighted sound pressure level in
each of the one-third octave bands according to Table 1. The vehicle
must also emit a sound meeting these requirements whenever moving at
less than 10 km/h.
(a) Directivity. When measured according to the test conditions of
S6 and test procedure of S7.2, the sound measured at the microphone on
the line CC' must have at least the A-weighted sound pressure level in
each of the one-third octave bands according to Table 1.
Table 1--One-Third Octave Band Min. SPL Requirements for Sound When
Stationary But Activated
------------------------------------------------------------------------
Min SPL, A-
One-third octave band center frequency, Hz weighted dB
------------------------------------------------------------------------
315..................................................... 42
400..................................................... 43
500..................................................... 43
2000.................................................... 42
2500.................................................... 39
3150.................................................... 37
4000.................................................... 34
5000.................................................... 31
------------------------------------------------------------------------
S5.1.2 Backing. For vehicles capable of rearward self-propulsion,
whenever the vehicle's gear selection control is in the reverse
position, the vehicle must emit a sound having at least the A-weighted
sound pressure level in each of the one-third octave bands according to
Table 2 as measured according to the test conditions of S6 and the test
procedure of S7.3.
Table 2--One-Third Octave Band Min. SPL Requirements for Sound while
Backing
------------------------------------------------------------------------
Min SPL, A-
One-third octave band center frequency, Hz weighted dB
------------------------------------------------------------------------
315..................................................... 45
400..................................................... 46
500..................................................... 46
2000.................................................... 45
2500.................................................... 42
3150.................................................... 40
4000.................................................... 36
5000.................................................... 34
------------------------------------------------------------------------
S5.1.3 Constant 10 km/h pass by. When tested under the conditions
of S6 and the procedures of S7.4, the vehicle must emit a sound having
at least the A-weighted sound pressure level in each of the one-third
octave bands according to Table 3 at any speed greater than or equal to
10 km/h, but less than 20 km/h.
S5.1.3.1 If after a vehicle to which this standard applies
according to paragraph S3(b) or S3(c) is tested in accordance with
paragraphs S7.4, for ten consecutive times without recording a valid
measurement because the vehicle's ICE remains active for the entire
duration of the test, the vehicle is not required to meet the
requirements in S5.1.3.
Table 3--One-Third Octave Band Min. SPL Requirements for 10 km/h Pass-by
------------------------------------------------------------------------
Min SPL, A-
One-third octave band center frequency, Hz weighted dB
------------------------------------------------------------------------
315..................................................... 48
400..................................................... 49
[[Page 2859]]
500..................................................... 49
2000.................................................... 48
2500.................................................... 45
3150.................................................... 43
4000.................................................... 39
5000.................................................... 37
------------------------------------------------------------------------
S5.1.4 Constant 20km/h pass by. When tested under the conditions of
S6 and the procedures of S7.5, the vehicle must emit a sound having at
least the A-weighted sound pressure level in each of the one-third
octave bands according to Table 4 at any speed greater than or equal to
20 km/h but less than 30 km/h.
S5.1.4.1 If after a vehicle to which this standard applies
according to paragraph S3(b) or S3(c) is tested in accordance with
paragraphs S7.5, for ten consecutive times without recording a valid
measurement because the vehicle's ICE remains active for the entire
duration of the test, the vehicle is not required to meet the
requirements in S5.1.4.
Table 4--One-Third Octave Band Min. SPL Requirements for 20 km/h Pass-by
------------------------------------------------------------------------
Min SPL, A-
One-third octave band center frequency, Hz weighted dB
------------------------------------------------------------------------
315..................................................... 54
400..................................................... 55
500..................................................... 56
2000.................................................... 54
2500.................................................... 51
3150.................................................... 49
4000.................................................... 46
5000.................................................... 43
------------------------------------------------------------------------
S5.1.5 Constant 30km/h pass by. When tested under the conditions of
S6 and the procedures of S7.6, the vehicle must emit a sound having at
least the A-weighted sound pressure level in each of the one-third
octave bands according to Table 5 at 30 km/h.
S5.1.5.1 If after a vehicle to which this standard applies
according to paragraph S3(b) or S3(c) is tested in accordance with
paragraphs S7.6, for ten consecutive times without recording a valid
measurement because the vehicle's ICE remains active for the entire
duration of the test, the vehicle is not required to meet the
requirements in S5.1.5.
Table 5--One-Third Octave Band Min. SPL Requirements for 30 km/h Pass-by
------------------------------------------------------------------------
Min SPL, A-
One-third octave band center frequency, Hz weighted dB
------------------------------------------------------------------------
315..................................................... 59
400..................................................... 59
500..................................................... 60
2000.................................................... 58
2500.................................................... 56
3150.................................................... 53
4000.................................................... 50
5000.................................................... 48
------------------------------------------------------------------------
S5.1.6 Pitch shifting to signify acceleration and deceleration. The
fundamental frequency of the sound emitted by the vehicle must vary
with speed by at least one percent per km/h between 0 and 30 km/h.
S5.2 Performance requirements for recognition as a motor vehicle.
S5.2.1 The sound emitted by the vehicle to meet the requirements in
S5.1.1 must contain at least one tone. A component is defined as a tone
if the total sound level in a critical band centered about the tone is
6 dB greater than the noise level in the band.
S5.2.2. The sound emitted by the vehicle to meet the requirements
in S5.1.1 must have at least one tone no higher than 400 Hz.
S5.2.3 The sound emitted by the vehicle to meet the requirements in
S5.1.1 must have broadband content in each one-third octave band from
160 Hz to 5000 Hz.
S5.3 Any two vehicles of the same make, model, and model year (as
those terms are defined at 49 CFR 565.12) must emit the same sound as
measured by the test required in S5.1.1 within 3 A-weighted dB in each
one-third octave band from 160 Hz to 5000 Hz
S6. Test Conditions.
S6.1 Weather conditions. The ambient conditions required by this
section must be met at all times during the tests described in S7.
Conditions must be measured with the accuracy required in S6.3.3 at the
microphone height required in S6.4 +/- 2.54 cm.
S6.1.1 The ambient temperature will be between 5 [deg]C (41 [deg]F)
and 40 [deg]C (104 [deg]F).
S6.1.2 The maximum wind speed at the microphone height is no
greater than 5 m/s (11 mph), including gusts.
S6.1.3 No precipitation and the test surface is dry.
S6.1.4 Background noise level. The background noise level must be
measured and reported as in S6.4 of SAEJ2889-1 (incorporated by
reference, see Sec. 571.5).
S6.2 Test surface. Test surface shall meet the requirements of ISO
10844:2011 (incorporated by reference, see Sec. 571.5).
S6.3 Instrumentation.
S6.3.1 Acoustical measurement. Instruments for acoustical
measurement must meet the requirements of S5.1 of SAE J2889-1
(incorporated by reference, see Sec. 571.5).
S6.3.2 Vehicle speed measurement. Instruments used to measure
vehicle speed during S7.4 and S7.5 of this standard must be capable of
continuous measurement within 1.0 km/h over the entire
test distance in S7.4 and S7.5.
S6.3.3 Meteorological instrumentation. Instruments used to measure
ambient conditions at the test site must meet the requirements of S5.3
of SAE J2889-1 (incorporated by reference, see Sec. 571.5).
S6.4 Test site. The test site must be established per the
requirements of S6.1.1 of SAE J2889-1 (incorporated by reference, see
Sec. 571.5), including Figure 1, ``Test Site Dimensions'' with the
definitions of the abbreviations in Figure 1 as given in Table 1, S4 of
SAE J2889-1 (incorporated by reference, see Sec. 571.5). Microphone
positions must meet the requirements of S7.1 of SAE J2889-1
(incorporated by reference, see Sec. 571.5).
S6.5 Test set up for directivity measurement must be as per S6.4
with the addition of one microphone meeting the requirements of S6.3.1
placed on the line CC', 2m forward of the line PP' at a height of 1.2m
above ground level.
S6.6 Vehicle condition
(a) Tires will be fitted and pressurized per the vehicle's tire
placard. Tire tread will be free of all debris. Tires will be
conditioned according to the following procedure:
(1) Drive the test vehicle around a circle 30 meters (100 feet) in
diameter at a speed that produces a lateral acceleration of
approximately 0.5 to 0.6 g for three clockwise laps, followed by three
counterclockwise laps.
(b) The vehicle's doors are shut and locked and windows are shut.
(c) All accessory equipment (air conditioner, wipers, heat, HVAC
fan, audio/video systems, etc.) will be off. Propulsion battery cooling
fans and pumps and other components of the vehicle's propulsion battery
thermal management system are not considered accessory equipment.
(d) Test weight of the vehicle will be the curb weight (as defined
in 571.3) plus 125 kilograms. Equipment, driver and ballast should be
evenly distributed between the left and right side of the vehicle. Do
not exceed the GVWR or GAWRs of the vehicle.
(e) Vehicle's electric propulsion batteries, if any, are fully
charged.
[[Page 2860]]
S6.7 Ambient correction
S6.7.1 Measure the background noise for at least 30 seconds before
and after a series of vehicle tests.
S6.7.2 A 10-second sample taken from these measurements will be
used to calculate the reported background noise.
S6.7.3 The 10-second sample selected will include background levels
that are representative of the background levels that will occur during
the vehicle measurement.
S6.7.4 The minimum A-weighted SPL in the selected 10-second sample
as the overall background noise level, Lbgn will be
reported. The average A-weighted SPL in the same 10-second sample will
also be noted.
S6.7.5 The minimum A-weighted \1/3\ octave band levels (OBLs) (per
ANSI S1.11, Class 1) in the selected 10-second sample will be reported
as the \1/3\ octave band background noise level, OBLbgn, fc.
The average A-weighted \1/3\ octave band level in the same 10-second
sample for each \1/3\ octave band will also be noted.
S6.7.6 each \1/3\ octave band of the measured jth test result
within a test condition OBLtest,j,fc, will be corrected
according to Table 6 to obtain the noise-corrected level
OBLtestcorr, j, fc which is the OBLtest, j, fc
minus the correction factor, Lcorr.
Table 6--Corrections for Background Noise
----------------------------------------------------------------------------------------------------------------
\1/3\ Octave band level
* Peak-to-Peak \1/3\ of jth test result, ith
\1/3\ Octave band noise level octave band background frequency, minus \1/3\
OBLbgn,fc noise level OBLbgn,fc,p- octave band noise level Correction Lcorr
p DL = OBLtest,j,fc-OBL
bgn,fc
----------------------------------------------------------------------------------------------------------------
>= 25 dB(A).......................... **..................... > 10 dB................ 0 dB.
< 8 dB................. > 8-10 dB.............. 0.5 dB.
> 6-8 dB............... 1.0 dB.
< 6 dB................. > 4.5-6 dB............. 1.5 dB.
> 3-4.5 dB............. 2.5 dB.
<= 3 dB................ Do not correct, but
report OBLtestcorr,j <
OBLtestj.
< 25 dB(A)........................... <=10 dB................ Do not correct, but
report: OBLtestcorr,j
< OBLtestj.
**..................... > 10 dB................ 0 dB.
----------------------------------------------------------------------------------------------------------------
* Ensure that maximum allowable peak-to-peak variation occurs in not more than one measurement for each
operation during the portion of the measurement that will be reported, e.g. within the second prior to pass-by
or during an entire active but stationary measurement.
** Ensure that the background level is at least 10 dB below the measurement during any portion of the
measurement that will be reported, e.g. within the second prior to pass-by or during an entire active but
stationary measurement.
S7. Test Procedure.
S7.1 Vehicle stationary but activated
S7.1.1 Position the vehicle stationary with the front plane at the
line PP', the centerline on the line CC' and the starting system
deactivated.
For vehicles equipped with a Park position, place the vehicle's
gear selection control in ``Park''. For vehicles not equipped with a
Park position, place the vehicle's gear selection control in
``Neutral'' and engage the parking brake. Activate the starting system
to energize the vehicle's starting system.
S7.1.2. The vehicle minimum sound pressure level shall be measured
per S7.3.2.1 and S7.4.1 of SAE J2889-1 (incorporated by reference, see
Sec. 571.5) and corrected for the ambient sound level in each \1/3\
octave band according to the procedure in S6.7 and the correction
criteria given in Table 6.
S7.1.3.1 Four consecutive valid measurements must be within 2 A-
weighted dB Measurements that contain sounds emitted by any component
of a vehicle's battery thermal management system are not considered
valid. When testing a hybrid vehicle with an internal combustion engine
that runs intermittently, measurements that contain sounds emitted by
the ICE are not considered valid.
S7.2 Backing. Test the vehicle per S7.1, except that the rear plane
of the vehicle is placed on line PP'.
S7.3 Pass-By test at 10km/h
(a) Measure the sound emitted by the vehicle at a constant 10 km/h
(+/- 1 km/h) throughout the measurement zone specified in S6.4 between
lines AA' and PP'. The test result shall be the lowest value (average
of the two microphones) of the four valid pass-bys. The test result
shall be reported to the first significant digit after the decimal
place.
(b) Four consecutive valid measurements must be within 2 A-weighted
dB. Measurements that contain sounds emitted by any component of a
vehicle's battery thermal management system are not considered valid.
When testing a hybrid vehicle with an ICE that runs intermittently,
measurements that contain sounds emitted by the ICE are not considered
valid. The test result shall be corrected for the ambient sound level
in each \1/3\ octave band according to the procedure in S6.7 and the
correction criteria given in Table 6 and reported to the first
significant digit after the decimal place.
S7.4 Pass by test at 20 km/h. Repeat the test of S7.3 at 20 km/h.
S7.5 Pass by test at 30 km/h. Repeat the test of S7.3 at 30 km/h.
S8 Prohibition on altering the sound of a vehicle subject to this
standard. No entity subject to the authority of the National Highway
Traffic Safety Administration may:
(a) disable, alter, replace or modify any element of a vehicle
installed as original equipment for purposes of complying with this
Standard, except in connection with a repair of a vehicle malfunction
related to its sound emission or to remedy a defect or non-compliance
with this standard; or
(b) provide any person with any mechanism, equipment, process or
device intended to disable, alter, replace or modify the sound emitting
capability of a vehicle subject to this standard, except in connection
with a repair of vehicle malfunction related to its sound emission or
to remedy a defect or non-compliance with this standard.
S9 Phase-in schedule
S9.1 Vehicles manufactured on or after September 1, 2015, and
before September 1, 2016. For vehicles manufactured on or after
September 1, 2015, and before September 1, 2016 the number of vehicles
complying with this standard must not be less than 30 percent of:
(a) The manufacturer's average annual production of vehicles
manufactured on or after September 1, 2012, and before September 1,
2015; or
[[Page 2861]]
(b) The manufacturer's production on or after September 1, 2015,
and before September 1, 2016.
S9.2 Vehicles manufactured on or after September 1, 2016, and
before September 1, 2017. For vehicles manufactured on or after
September 1, 2016, and before September 1, 2017, the number of vehicles
complying with this standard must not be less than 60 percent of:
(a) The manufacturer's average annual production of vehicles
manufactured on or after September 1, 2013, and before September 1,
2016; or
(b) The manufacturer's production on or after September 1, 2016,
and before September 1, 2017.
S9.3 Vehicles manufactured on or after September 1, 2017, and
before September 1, 2018. For vehicles manufactured on or after
September 1, 2017, and before September 1, 2018, the number of vehicles
complying with this standard must not be less than 90 percent of:
(a) The manufacturer's average annual production of vehicles
manufactured on or after September 1, 2014, and before September 1,
2017; or
(b) The manufacturer's production on or after September 1, 2017,
and before September 1, 2018.
S9.4 Vehicles manufactured on or after September 1, 2018. All
vehicles manufactured on or after September 1, 2018 must comply with
this standard.
S9.5 Vehicles produced by more than one manufacturer.
S9.5.1 For the purpose of calculating average annual production of
vehicles for each manufacturer and the number of vehicles manufactured
by each manufacturer under S9.1 through S9.3, a vehicle produced by
more than one manufacturer must be attributed to a single manufacturer
as follows, subject to S9.6.2:
(a) A vehicle that is imported must be attributed to the importer.
(b) A vehicle manufactured in the United States by more than one
manufacturer, one of which also markets the vehicle, must be attributed
to the manufacturer that markets the vehicle.
S9.5.2 A vehicle produced by more than one manufacturer must be
attributed to any one of the vehicle's manufacturers specified by an
express written contract, reported to the National Highway Traffic
Safety Administration under 49 CFR Part 585, between the manufacturer
so specified and the manufacturer to which the vehicle would otherwise
be attributed under S9.6.1.
S9.6 Small volume manufacturers.
Vehicles manufactured during any of the three years of the
September 1, 2015 through August 31, 2018 phase-in by a manufacturer
that produces fewer than 5,000 vehicles for sale in the United States
during that year are not subject to the requirements of S9.1, S9.2,S9.3
and S9.5.
S9.7 Final-stage manufacturers and alterers. Vehicles that are
manufactured in two or more stages or that are altered (within the
meaning of 49 CFR 567.7) after having previously been certified in
accordance with Part 567 of this chapter are not subject to the
requirements of S9.1 through S9.5. Instead, all vehicles produced by
these manufacturers on or after September 1, 2018 must comply with this
standard.
PART 585--PHASE-IN REPORTING REQUIREMENTS
0
4. The authority citation for part 585 is revised to read as follows:
Authority: 49 U.S.C. 322, 30111, 30115, 30117, and 30166;
delegation of authority at 49 CFR 1.95.
0
5. Add subpart N to read as follows:
Subpart N-- Minimum Sound Requirements for Hybrid and Electric Vehicles
Reporting Requirements
Sec.
585.128 Scope.
585.129 Purpose.
585.130 Applicability.
585.131 Definitions.
585.132 Response to inquiries.
585.133 Reporting requirements.
585.134 Records.
Subpart N--Minimum Sound Requirements for Hybrid and Electric
Vehicles Reporting Requirements
Sec. 585.128 Scope.
This subpart establishes requirements for manufacturers of hybrid
and electric passenger cars, trucks, buses, multipurpose passenger
vehicles, low-speed vehicles, and motorcycles to submit a report, and
maintain records related to the report, concerning the number of such
vehicles that meet minimum sound requirements of Standard No. 141,
Minimum Sound Requirements for Hybrid and Electric Vehicles (49 CFR
571.141).
Sec. 585.129 Purpose.
The purpose of these reporting requirements is to assist the
National Highway Traffic Safety Administration in determining whether a
manufacturer has complied with the minimum sound requirements of
Standard No. 141, Minimum Sound for Hybrid and Electric Vehicles (49
CFR 571.141).
Sec. 585.130 Applicability.
This subpart applies to manufacturers of hybrid and electric
passenger cars, trucks, buses, multipurpose passenger vehicles, low-
speed vehicles, and motorcycles.
Sec. 585.131 Definitions.
(a) All terms defined in 49 U.S.C. 30102 are used in their
statutory meaning.
(b) Bus, gross vehicle weight rating or GVWR, low-speed vehicle,
multipurpose passenger vehicle, passenger car, truck, and motorcycle
are used as defined in Sec. 571.3 of this chapter.
(c) Production year means the 12-month period between September 1
of one year and August 31 of the following year, inclusive.
(d) Electric Vehicle is used as defined in Sec. 571.141 of this
chapter.
Sec. 585.132 Response to inquiries.
At any time during the production years ending August 31, 2016,
August 31, 2017, and August 31, 2018 each manufacturer shall, upon
request from the Office of Vehicle Safety Compliance, provide
information identifying the vehicles (by make, model and vehicle
identification number) that have been certified as complying with the
requirements of Standard No. 141, Minimum Sound Requirements for Hybrid
and Electric Vehicles (49 CFR 571.141). The manufacturer's designation
of a vehicle as a certified vehicle is irrevocable.
Sec. 585.133 Reporting requirements.
(a) Phase-in reporting requirements. Within 60 days after the end
of each of the production years ending August 31, 2016, August 31,
2017, and August 31, 2018, each manufacturer shall submit a report to
the National Highway Traffic Safety Administration concerning its
compliance with the requirements of Standard No. 141 Minimum Sound
Requirements for Hybrid and Electric Vehicles (49 CFR 571.141) for its
vehicles produced in that year. Each report shall provide the
information specified in paragraph (d) of this section and in Sec.
585.2 of this part.
(b) Phase-in report content--(1) Basis for phase-in production
goals. Each manufacturer shall provide the number of vehicles
manufactured in the current production year, or, at the manufacturer's
option, in each of the three previous production years. A manufacturer
that is, for the first time, manufacturing vehicles for sale in the
United States must report the number of vehicles manufactured during
the current production year.
(2) Production of complying vehicles. Each manufacturer shall
report for the
[[Page 2862]]
production year being reported on, and each preceding production year,
to the extent that vehicles produced during the preceding years are
treated under Standard No. 141 as having been produced during the
production year being reported on, information on the number of
vehicles that meet the requirements of Standard No. 141, Minimum Sound
Requirements for Hybrid and Electric Vehicles (49 CFR 571.141).
Sec. 585.134 Records.
Each manufacturer shall maintain records of the Vehicle
Identification Number for each vehicle for which information is
reported under Sec. 585.133 until December 31, 2023.
Note: The following appendices will not appear in the Code of
Federal Regulations.
Appendix A--Glossary of Sound Engineering Terms
Acoustic Pressure: A pressure variation about a medium's mean
pressure caused by a sound wave.
Acoustic Wave: A wave that propagates acoustic pressure through
a medium, such as air.
Ambient (also called ambient noise or background noise):
Relating to the immediate environment or surroundings. Generally
refers to unwanted sounds. In an acoustic measurement, after the
main sound being studied is suppressed or removed, this is the
remaining sum of sounds taken from the environment of the
measurement.
Amplitude: The value of the sound pressure at any instant.
Amplitude Modulation: When the amplitude of a sound changes as a
function of time.
Attenuation: A decrease in the intensity of a sound.
Auditory Filter: A measure of the auditory systems frequency
selectivity. An auditory filter is a band pass filter that closely
approximates the shape of a rounded exponential filter or, to a
lesser degree, a one-third octave band filter.
Auditory Flutter/Flicker: Auditory sensation produced when a
continuous sound is disturbed at a slow, intermittent rate.
Auditory Fusion: Series of short successive sounds that are
perceived as one continuous sound.
A-weighting: A filter that attenuates low and high frequencies
and amplifies some mid-range frequencies. The A-weighting curve
approximates the equal loudness contour at 40 dB.
Bandwidth: Range of frequencies. For example, a speaker may have
an effective bandwidth from 150 to 5000 Hz. Alternatively, it is the
minimum frequency subtracted from the maximum frequency. For the
above example, this would be 5000--150 or 4850 Hz.
Band-Pass Filter: A type of filter that only allows a specific
range of frequencies to pass through while attenuating all other
frequencies. For example, a one-third octave band filter centered at
1000 Hz would pass sounds with frequencies from about 890 to 1120 Hz
while attenuating frequencies outside this range.
Band Pressure Level: The pressure level of a sound wholly
contained within a particular frequency band.
Band-Stop Filter: A type of filter that attenuates a particular
range of frequencies while allowing frequencies outside the band to
pass through.
Basilar Membrane: A membrane inside the cochlea that supports
the organ of corti and vibrates as a response to sound.
Broadband: Signal with a spectrum that covers a broad range of
frequencies.
Broadband levels: Levels regarding signal quantities that cover
a wide range of frequencies.
Cochlea: A small snail shell-shaped tube within the inner ear
that houses the receptor organs responsible for converting
mechanical vibration into electro-chemical signals for the brain to
process.
Condenser: Type of microphone that uses acoustic pressure to
change the distance between two plates of a capacitor. The changing
distance between the two plates causes the voltage across the
capacitor to change.
Consonant: Auditory experience where sounds are harmonic.
Dichotic: Event in which sounds heard by both ears are
different.
Diffraction: The bending of waves as they travel around an
object or across an impedance change.
Digital Recorder: A device that converts acoustic waves into
electric signals and stores them in its memory to be replayed back.
Dipole: Usually constructed with two monopoles with equal but
opposing strengths.
Directivity: The relative proportions of acoustical energy that
are emitted from a source as a function of direction, typically
expressed in polar coordinates.
Dissonant: An auditory experience where sounds are in-harmonic,
usually referred to as noise.
Divergence: The physical spreading of the sound waves over an
area. Divergence attenuates a sound as a function of distance. See
also ``Line Source'' and ``Point Source''.
Decibel (dB): Ten times the logarithmic ratio of a physical
quantity to a reference value. For example,
Sound Pressure Level = 10 log10(P2/
Pref2)
where P is the acoustic pressure and Pref is equal to 20
[ballot]Pa for air.
Doppler Effect: Change in the frequency of a sound wave due to
the relative velocity between the source and the observer. As the
sound source approaches the observer, the frequency is perceived to
be higher and as it moves away it is perceived to be lower.
Dull: A semitone less than the natural pitch of a given tone.
Sound composed of a greater proportion of low frequencies.
Dynamic Microphone: Type of microphone that uses a small metal
coil positioned to be within a particular magnetic field attached to
a diaphragm. Acoustic pressure causes the diaphragm to move the coil
through the magnetic field and a current is generated.
Equivalent Rectangular Bandwidth (ERB): An idealized rectangular
filter with a bandwidth defined such that it passes the same energy
as an associated auditory filter. A set of contiguous ERB filters
can be used to represent the frequency scale in a psychoacoustic
sense. For example, an auditory filter centered at 1000 Hz has an
equivalent rectangular bandwidth of 132 Hz and it takes 15.6
contiguous equivalent rectangular bandwidths to cover the auditory
range below 1000 Hz. An auditory filter centered at 4000 Hz has an
equivalent rectangular bandwidth of 456 Hz and it takes 27.1
contiguous equivalent rectangular bandwidths to cover the auditory
range below 4000 Hz.
Equal Loudness Contour: A contour of levels (y-axis) versus
frequency (x-axis) such that tones of different frequency and
different level are judged to be equally loud.
Equal Loudness Principle: Mid-range frequencies (approx. 320--
5120 Hz) are perceived with greater intensity than lower (20 to 320
Hz) or higher frequencies (5000 to 20,000 Hz).
Filter: A system that selectively passes some elements and
attenuates others as a function of frequency.
Flat Response: A flat frequency-response curve, i.e. a response
that does not change with frequency, sometimes referred to as Z or
un-weighted.
Free Field: A sound field without boundaries such that sound is
not reflected or scattered.
Frequency: Number of times a particle in a medium contracts and
expands (cycles) per unit of time. Typically expressed in Hertz
(Hz); one cycle per second is equal to 1 Hz. Humans can detect sound
waves with a wide range of frequencies, nominally ranging between 20
to 20,000 Hz.
Frequency Response: The response of a system to an input as a
function of frequency. The response can be characterized by
including both the magnitude as a function of frequency and the
phase as a function of frequency. The magnitude describes the
amplitude of the output relative to the input while the phase
describes the time delay between the input and output of the system.
Frequency Modulation: Changing frequency as a function of time.
Fundamental Frequency: The lowest frequency of a waveform.
Hair Cells: Sensory receptors found in the organ or corti on the
basilar membrane in the cochlea that have hair-like structures
(stereocilia). Hair cells transform sound waves into nerve impulses.
Half-power Point: Frequency at which the power output of an
amplifier reduces to half of its mid-band level.
Harmonics: Components of a sound that are integer multiples of a
fundamental frequency in the sound.
Harmonic Distortion: The ratio (normally expressed as a
percentage) of the sum of the acoustic power of all of the harmonics
generated by the device under test to the power of the fundamental,
pure tone being produced. Harmonic distortion increases rapidly as a
device is driven close to its maximum output capability or when a
speaker is driven at frequencies outside its intended range.
[[Page 2863]]
Head-Related-Transfer-Function (HRTF): Essentially a frequency
response that is also a function of angle. It accounts for how a
sound changes to an observer due to the relative position of the
source and the head, pinna, and torso of the observer.
Hertz (Hz): The unit associated with frequency. One cycle per
second equals one Hertz.
In-harmonic: A frequency component that is not an integer
multiple of another frequency.
Inner Ear: The innermost portion of the ear located behind the
middle ear. It contains the cochlea and the vestibular system.
Line Source: A sound source that geometrically forms a line.
Line sources attenuate at 3 dB per distance doubling perpendicular
to the source. One example is roadway noise; another is a stack of
speakers at a concert.
Longitudinal waves: Waves moving in the same direction as it is
being propagated.
Loud: Producing much noise, being easily audible.
Loudness: Attribute of an auditory sensation that humans can use
to judge sound intensity. Loudness is used to rank sounds on a scale
from quiet to loud.
Malleus: One of the three ossicles (bones) in the middle ear, it
is attached to the tympanic membrane (ear drum) and the body of the
incus (anvil).
Masking: Phenomenon when the perception of a sound is diminished
by the presence of another sound.
Microphone: A device that converts acoustic waves into
electrical signals.
Middle Ear: Air cavity behind the tympanic membrane (ear drum)
and before the inner ear.
Minimum Audible Field: the threshold for detecting sound in a
sound field.
Minimum Audible Threshold: Also known as the absolute threshold
of hearing, it refers to the minimum sound level of a pure tone that
the average ear with normal hearing can hear without any other sound
in its environment.
Modulation: A change in the dimension of a stimulus. For example
see ``Amplitude Modulation'' or ``Frequency Modulation''.
Monopole: A single point in space that is an acoustic source.
Narrow band: A limited range of frequency, as opposed to a wide
band, which tends to include frequencies from the low to high end, a
narrow band focuses in on a particular range.
Natural Frequency: Frequency at which a system has maximum, or
near maximum, response.
Noise: Sound wave(s) that is made up of random sounds. Sound
wave(s) that is viewed as an undesirable sound.
Octave (also called octave band): Interval between two
frequencies that have a ratio of 2:1. The range of human hearing
covers approximately 10 octaves. For example, if the first octave is
20 to 40 Hz the next octave is 40 to 80 Hz, the next is 80 to 160
Hz, etc.
One-third Octave Band: Frequency band that is one-third of an
octave band or whose lower and upper limits are 2\1/3\ times the
center frequency apart, as defined by their half-power points. For
example a one-third octave band centered at 1000 Hz has upper and
lower cutoff frequencies at about 890 and 1120 Hz and a bandwidth of
230 Hz. A one-third octave band centered at 4000 Hz has upper and
lower cutoff frequencies at about 3560 and 4490 Hz and a bandwidth
of 930 Hz.
Organ of Corti: Also known as the spiral organ, it is located in
the inner ear and contains hair cells, which act as receptors to
sound waves.
Outer Ear: The visible outer part of the ear that directs sound
waves through the canal within the temporal bone and delivers them
to the tympanic membrane (ear drum).
Pascal: Unit used to measure pressure; it is equal to
9.8692x10-6 atm.
Period: The time interval in which successive occurrences of a
recurring or cyclic phenomenon occur. The reciprocal of frequency.
Phase: The time relationship between two or more sounds reaching
a receiver. The sounds are in phase when their amplitudes add. The
sounds are out-of-phase when their amplitudes subtract.
Phon: A unit used to measure the loudness level of a sound in
dB.
Pink Noise: A random noise whose amplitude is inversely
proportional to frequency. Pink Noise sounds more natural than white
noise.
Pinna: External part of the human ear, also known as the
auricle.
Pitch: The sensation of a frequency. Attribute of an auditory
sensation that humans can use to order sounds on a musical scale. A
high pitch sound corresponds to a high frequency sound wave. A low
pitch sound corresponds to a low frequency sound wave.
Pitch Strength: Perception of how strong a pitch seems to be
according to a listener. Two sounds with equal frequencies can be
perceived to have different strengths.
Point Source: A sound source whose dimensions are sufficiently
small that it can be treated as a point. Point sources attenuate at
6 dB per distance doubling. One example is of a point source is a
stationary ICE vehicle at idle.
Power: A measure of energy supplied or consumed per unit of
time, usually expressed in Watts (W). A sound with a power of only
one-trillionth of one W can be audible in an otherwise quiet
environment; a jackhammer has an acoustic power output of about 1 W.
Propagation: The advancement of a sound wave in a particular
direction traveling through a medium.
Psychoacoustics: A branch of psychophysics that studies the
psychological correlations between acoustic and psychological
parameters.
Pure Tone: A sound characterized by the fact that it is
comprised of only one frequency.
Quiet: Causing little to no noise.
Reflection: A change in the direction of propagation of a wave
due to boundary, for example pavement.
Refraction: Bending of waves due to a change in the speed of
sound in the medium, for example, due to a temperature change in the
air.
Resonance: The response of a system to input at a natural
frequency.
Reverberation: Repetition of sound resulting from reflected
sound waves.
Reverberant Field: A sound field resulting from a large number
of reflections from boundaries within an enclosed area.
Ribbon: A type of microphone that converts sound into an
electrical signal by placing a ribbon between the two poles of a
magnet to generate electromagnetic induction.
Roll-off Rate: The steady attenuation that occurs on either end
of a frequency range which is typically expressed in dB/octave or in
dB/decade.
Roughness: Level of dissonance.
Sharp: A semitone above the natural pitch of a given tone. Sound
composed of a greater proportion of high frequencies.
Sinusoid (Sine): Used to graphically represent a sound wave. A
trigonometric function of an angle describing the ratio between the
length of the opposite side of the triangle from which the angle is
drawn, and the length of the adjacent side of the triangle.
Sone: Unit of subjective loudness on a linear scale. A sound
that is 14 sones is twice as loud as a 7 sone sound.
Sound Intensity: The sound power passing through an area in a
sound field, expressed as Watts per square meter.
Sound Intensity Level: The logarithmic measurement of sound
intensity with respect to a reference level.
SIL = 10 log10(I\2\/Iref\2\)
where I is the acoustic intensity and Iref is equal to
10-12 W/m\2\ for air.
Sound Pressure Level (SPL): Level of a sound relative to a
reference pressure and measured in decibels.
SPL = 10 log10(P\2\/Pref\2\)
where P is the root mean square of the acoustic pressure and
Pref is equal to 20 microPascals ([mu]Pa) for air.
Examples of a-weighted sound pressure levels include: threshold of
human hearing (0 dB(A)), quiet office (40 dB(A)), noisy restaurant
(70 dB(A)), rock concert (110 dB(A)), pain (140 dB(A))
Sound Level Meter: Instrument used to measure sound pressure
levels, often used for noise pollution studies.
Spectral Balance: The relative pressure levels of components of
a sound at various frequencies. This is often described by a
spectral plot with frequency in the horizontal axis and sound
pressure level/Hz on the vertical axis.
Stationary Sound: A sound whose root mean squared amplitude does
not change with time. Examples include a fan running at a constant
speed, a waterfall, and a constant tone or hum.
Tonalness (tonality): Harmonic effect of being in a certain key.
Transverse Waves: Waves moving in right angles to their
propagation.
Tympanic Membrane: Also known as the ear drum, a membrane in the
inner ear that vibrates as a response to sound, or changes in air
pressure.
Un-weighted Spectrum: A spectrum recorded with uniform
amplification at all frequencies. In contrast, many spectra are
recorded after the signal is processed through filters that
approximate the variation in
[[Page 2864]]
sensitivity with frequency that occurs in human hearing (e.g., the
A-weighted filter). See also ``Flat Response''.
.wav: Waveform Audio File Format, a type of file format used to
storing audio.
White Noise: Noise with spectrum level that does not vary as a
function of frequency.
Appendix B. Acoustic Primer
This primer introduces and describes what sound is, its
components, how it is perceived by humans and how the different
components of a sound can be measured. Sound can be described using
physical principles but is also a perceptual phenomenon. Humans can
perceive various qualities of sound, not all of which have
established quantitative measures. Humans can also perceive the
direction, distance and movement of sound sources. The information
included here provides background and context to concepts put forth
in the NPRM.
What is sound?
A sound is said to exist when the static pressure of a medium
(typically air) is disturbed by periodic pressure variations (sound
waves) that propagate through the medium and are perceived by a
listener. The pressure variations in the medium are due to the
compression and rarefaction of molecules in the medium. In regions
of compression, the density of molecules is high and the number of
molecule collisions increases relative to the static pressure
condition. In regions of rarefaction, the density of molecules is
low and the number of molecule collisions decreases relative to the
static pressure condition. Over time, the pressure in a given region
will increase and decrease as the sound wave propagates through the
medium. The change in pressure relative to the static pressure is
called the acoustic or sound pressure.
In the simplest case, sound pressure can be represented as a
function of time by a sinusoidal wave for a specific location in
space, as shown in Figure 1.\136\ Here, the baseline represents the
static pressure. The difference in pressure from the baseline to the
peak of the wave is the peak amplitude of the acoustic pressure; the
higher the amplitude, the louder the sound. As time progresses, the
pressure increases and decreases cyclically for this location. The
period of the wave can be defined by the time that it takes to go
from one peak to the next; a longer period indicates a lower pitch.
Another way to quantify the rate of change of a wave is by its
frequency. The frequency of a wave is the inverse of the period and
the unit is Hertz (Hz); the lower the frequency, the lower the
pitch. The wavelength of a sound wave is similar to the period of
the wave, except that rather than considering the time to go from
one peak to the next for a given location in space, one considers
the distance to go from one peak to the next for a given instant in
time. The wavelength is mathematically related to the period by
[lambda] = cT, where [lambda] is the wavelength, c is the speed of
sound in the medium and T is the period.
---------------------------------------------------------------------------
\136\ While it is convenient to represent sound waves as
transverse waves, where the motion is perpendicular to the wave
propagation, they are in actuality longitudinal waves, where the
motion is parallel to the wave propagation.
[GRAPHIC] [TIFF OMITTED] TP14JA13.034
The relative location of sound source and listener in an
environment can have a strong effect on the final sound that is
received by the listener. As a sound propagates away from the
source, the acoustic energy \137\ is spread over a greater area in a
manner similar to ripples in a pond. In a pond, the ripple's
diameter becomes larger but the amplitude becomes smaller the
further they travel from the source. Similarly, the further a sound
propagates from a source, the quieter the sound will tend to be. For
a point source radiating sound into free space, the intensity of
that sound will diminish by a factor of four for each doubling of
distance from the source to listener (inverse square law). However,
in typical environments, reflections and atmospheric absorption also
affect the sound level. The latter effect is greatest for high
frequencies, so when a sound propagates long distances, the high
frequency components of a sound will tend to decrease more than the
low frequency components. This affect is most noticeable for
distances greater than a hundred meters. Finally, sound propagation
can be affected by intervening surfaces, which can reflect and block
sound propagation. Highway barriers are a classic example of
surfaces intended to block sound propagation. By placing these
barriers between traffic and the listener, the sound due to the
traffic can be reduced at the listener's position. A ``live''
gymnasium is an example of an environment with many reflective
surfaces. Due to the reflective surfaces, sound waves can arrive
simultaneously at the listener from the same source even though the
sounds were emitted at slightly different times. The combination of
these direct and reflected sound waves create interference patterns
that can cause the level to be higher or lower. Constructive
interference occurs when the sounds are ``in phase'', that is, when
the peaks line up. Destructive interference occurs when the sounds
are ``out of phase'', that is, when peaks line up with valleys.
---------------------------------------------------------------------------
\137\ Acoustic energy is equal to the acoustic intensity
integrated over the area. In an environment with no reflecting
boundaries, the acoustic intensity is proportional to the acoustic
pressure squared.
---------------------------------------------------------------------------
How is sound perceived?
Amplitude and frequency of sound pressure are physical
attributes of sound that can be related to perceptual dimensions
such as loudness, pitch, and timbre.\138\ Humans interpret these
psychological dimensions subjectively, but some of them can be
quantified through psychoacoustic modeling. Psychoacoustics is the
study of how humans
[[Page 2865]]
perceive sound and forms the basis for extracting objective data
from the physical characteristics of acoustic pressure to quantify
how humans perceive the loudness, pitch, and timbre of a sound.
However, some of the properties of sounds that are important to
recognition or the characterization of a sound as pleasant or
annoying have no established metrics.
---------------------------------------------------------------------------
\138\ Since timbre includes all other perceptual characteristics
other than the loudness and pitch of a sound, it includes the
perception of modulations, attack, decay, sharpness, roughness, etc.
---------------------------------------------------------------------------
The loudness of a sound (by definition, a subjective measure) is
primarily related to the sound pressure level of a sound, but is
also influenced by its frequency. Loudness (or loudness level) is
measured in sones (or phons). The loudness level of a sound in phons
is equal to the sound pressure level in dB of a 1000-Hz tone that is
perceived to be equal in loudness to the sound of interest. For
example, all sounds that are judged to be equal in loudness to a
40dB-SPL, 1000 Hz tone have a loudness level equal to 40 phons.
Loudness level (phons) increases logarithmically, while loudness
(sones) increases linearly. For a human to judge a sound to be twice
as loud, the sound needs to be increased by roughly 10 phons or by
twice the number of sones, for example the perceived loudness
approximately doubles for 40, 50, 60, 70, 80 phons or 1, 2, 4, 6, 8,
16 sones. The relationship between perceived loudness and the
physical acoustic pressure of a sound is non-linear in both
amplitude and frequency, as illustrated in Figure 2. This means that
the relative loudness (and detectability) of two sounds with the
same SPL value can change substantially depending on their amplitude
and frequency.
[GRAPHIC] [TIFF OMITTED] TP14JA13.035
Pitch is directly related to frequency. Roughly speaking, humans
interpret the fundamental frequency of a sound to be its pitch; the
higher the frequency, the higher the pitch; the lower the frequency,
the lower the pitch. A sound wave with a high frequency produces the
sensation of a high, sharp pitch and a low frequency produces a low,
dull pitch. Pitch strength refers to the strength of the pitch's
sensation. The pitch strength is dependent on the tone-to-noise
ratio. The tonal components of a sound have periodic, sinusoidal
waveforms, while the noise components are random (e.g., wind noise).
However, if noise is constrained by some physical or electronic
process to contain a relatively narrow band of frequencies, it can
produce the sensation of pitch, e.g., some turbine sounds. The
greater the noise levels relative to the tone level, the weaker the
pitch strength.
There is a strong correlation between the pitch of a sound and
the spectral location of its frequency components. When there are
multiple frequency components present that are integer multiples of
a single lowest frequency, the sound is said to be harmonic. The
lowest frequency is commonly referred to as the fundamental. If
there are harmonics present, the ability to detect pitch is
improved. Even when the fundamental is not present (case of the
missing fundamental), the human auditory system compensates for the
loss of the lower harmonic. For example, a tone complex of 600, 800
and 1200 Hz is judged to have a pitch of 400 Hz because this
corresponds to the shortest common wave period.
Timbre describes the characteristics of a sound that allow the
listener to differentiate two sounds with the same pitch and
loudness. The timbre of a sound is based predominantly on
characteristics of the sound's spectrum but is also dependent on
temporal characteristics. Characteristics of the spectrum that
effect timbre include: the relative strength of the tonal and noise
character of the sound (pitch strength and
[[Page 2866]]
tonality); the number of harmonics (harmonic richness); and the
relative level of high frequencies and low frequencies components
(sharpness and dullness). Temporal characteristics include the
musical concepts of ``attack, sustain, and decay'' as well as
``vibrato'' or modulations. A violin, a muted bell, and a voice can
all create a sound at the same pitch and loudness, but the violin
will have a short attack, long sustain, and moderate decay. The
muted bell will have a short attack, a short sustain, and a short
decay. The voice will have a long attack, a moderate sustain, and a
moderate decay. The violin and voice can be expressed either with or
without vibrato (modulations).
Temporal effects on timbre can also be considered outside of the
musical context. Humans can perceive sounds as being constant,
changing or impulsive. A sound is perceived to be constant when the
physical aspects, such as the tonal frequencies and levels, are
unvarying and steady. An example would be standing next to an idling
vehicle. Since the car is stationary and the engine speed is
constant, the sound emitted from the engine does not vary
significantly (assuming a well-functioning engine). Slow changes in
pitch or loudness at a rate of about [frac12] second or longer lead
to the perception of a changing sound. A good example of a changing
sound is that of a siren on an emergency vehicle. If the rate of
change is very quick, for example over a time less than [frac12]
second, the sound will be perceived as impulsive. Sound with a very
high rate of change such as gun fire and individual combustions
produce impulsive sounds.
It is rare that humans hear only one sound at a time. This is
because one sound may overshadow, very closely resemble, or
interfere with the perception of another sound that does not share
the same physical characteristics. When one sound interferes with
the perception of another sound, it is called masking. The masking
threshold is the point at which one sound's audibility or
detectability is lost because of the masking sound. It can be
measured in the laboratory by presenting subjects with different
target sounds (stimuli) of different amplitudes and frequencies in
combination with various masking sounds, and testing the subjects to
determine under which conditions they can detect the targets. The
level of the masking sound is used as an indicator of the amount
masking the sound provided for the stimulus.
How is sound quantified?
Sound is most commonly quantified in decibels (dB). A decibel is
a logarithmic unit of magnitude based on the ratio of two powers. In
terms of acoustics, the ratio, commonly referred to as the sound
pressure level, is between the mean-squared acoustic pressure
relative to a reference mean-squared acoustic pressure. The
reference for sound pressure level measurements in air is typically
20 micro-Pascals. However, when sounds are processed electronically,
standard practice is to represent their intensity on a dB scale
where 0 is the maximum amplitude that can be handled without
distortion. In this frame of reference, levels are usually negative
numbers.
Usually, acoustic equipment used for measurements is A-weighted
to approximate the frequency response of human hearing (see Figure
2) to sounds of moderate loudness.
The distribution of acoustic energy in a sound can be
represented graphically with a full spectrum plot, like that shown
in Figure 3, or more compactly by breaking the spectrum into a
relatively small number of bands, usually 30 for a one-third octave
analysis, shown in Figure 4.
[[Page 2867]]
[GRAPHIC] [TIFF OMITTED] TP14JA13.036
Due to the breadth of this spectrum, octave bands and one-third
octave band scales were created to facilitate identifying the
specific frequency of sounds. Octave bands separate the range of
human audible frequencies into ten bands and the one-third octave
bands split each of the ten octave bands into three bands. Each
scale in the breakdown provides more information about the sound
being analyzed. An octave band is split by the interval between two
frequencies and identified by the center frequency within the bands:
31.5 Hz, 63 Hz, 125 Hz, 250 Hz, 500 Hz, 1 kHz, 2 kHz, 4 kHz, 8, kHz
and 16 kHz. Since there are ten octaves, there are 30 one-third
octave bands. A one-third octave band extends from one-sixth of an
octave below the center frequency to one-sixth above an octave
frequency. The measurement of how humans perceive the loudness of a
sound is dependent on the sound pressure level and
[[Page 2868]]
can be used as a way to determine the annoyance qualities of a
sound. The values from a one-third-octave analysis can also be
easily presented in tabular form (Table 1), while those from a full-
spectrum cannot.
Table 8--Example of One-Third-Octave Data in Tabular Form: Summary of Ambient Levels during ICE Measurements, A-
weighted Level, dB(A)
----------------------------------------------------------------------------------------------------------------
Linear average
\1/3\ octave band center (\1/3\ octave Min (overall A- Max (overall A- Min (\1/3\ Max (\1/3\
frequency, Hz band) weighted) weighted) octave band) octave band)
----------------------------------------------------------------------------------------------------------------
100 to 20k...................... 49.6 46.1 53.4 45.3 54.7
100............................. 34.6 30.7 34.1 30.7 38.4
125............................. 35.5 32.4 36.8 32.4 42.1
160............................. 36.1 32.1 37.9 32.0 41.5
200............................. 36.9 32.7 37.9 32.7 41.2
250............................. 36.5 33.9 38.1 33.1 40.7
315............................. 36.5 32.5 37.6 32.1 41.5
400............................. 36.0 31.9 38.1 31.8 39.7
500............................. 36.7 33.6 39.8 33.1 41.1
630............................. 38.2 34.4 41.7 34.0 42.2
800............................. 40.2 36.0 46.1 35.8 46.1
1k.............................. 41.1 36.4 46.4 36.4 46.4
12.5k........................... 40.0 35.3 45.1 35.3 45.1
16k............................. 37.6 32.9 43.1 32.9 43.1
2k.............................. 34.7 30.3 37.8 30.3 37.8
2.5k............................ 34.5 32.8 35.4 30.8 42.1
3.15k........................... 35.5 36.9 37.1 30.0 39.6
4k.............................. 34.0 33.0 34.3 28.3 40.2
5k.............................. 29.0 25.0 29.8 24.3 32.8
6.3k............................ 25.7 22.3 26.9 19.7 31.7
8k.............................. 20.2 16.6 22.4 14.1 24.2
10k............................. 14.4 10.3 17.3 7.6 18.3
12.5k........................... 8.9 5.0 11.7 3.2 13.0
16k............................. 3.1 0.7 5.6 -0.8 8.7
20k............................. -1.9 -3.1 -0.4 -3.5 2.0
----------------------------------------------------------------------------------------------------------------
Summary
The acoustic science described above was intended to provide
novices enough knowledge to understand the data and discussions put
forth in the NPRM. Sound is a form of energy that is created when a
medium vibrates, creating pressure variations (compressions and
rarefactions of molecules) within a medium (such as air) which
creates a pattern called a wave. Sound pressure over time creates
peaks and valleys which make up the wavelength. The difference in
acoustic pressure from the ambient pressure (no contraction of the
medium) to the peak or valley of a wavelength is called the
amplitude; the higher the amplitude, the louder the sound. The
period of a wave is the time it takes for a cycle (a peak and a
valley) to complete; a longer period indicates a lower pitch. The
frequency of a sound is the number of complete wave cycles that pass
by a given point in space every second; the higher the frequency,
the higher the pitch.
The wavelength, amplitude, period and frequency are physical
attributes of a sound wave that affect the human perception of
loudness, pitch and timbre. These perceptions can be quantified
using psychoacoustics. Psychoacoustics is the study of how humans
perceive sound and forms the basis for extracting objective data
from the physical characteristics of acoustic pressure (sound).
Using the physical characteristics and psychoacoustic analysis, a
sound is usually measured in decibels (dBs) within an octave.
Octaves can be further broken down into one-third octave bands which
provide more information about the spectral content of sound being
analyzed. After reading this primer, the reader should understand
what ``sound'' is, identify its different components, and understand
how humans perceive sound and how each of these contributes to
measuring sound.
References
[1] Christopher L. Morfey, Dictionary of Acoustics, Academic Press,
2001.
[2] ANSI S1.1-1994, Acoustical Terminology, American National
Standards Institute, 1994.
[3] CEI IEC 50(801), International Electrotechnical Vocabulary--
Chapter 801: Acoustics and Electroacoustics, International
Electrotechnical Commission, 2nd Edition, 1994.
[4] ANSI S3.20-1973, Psychoacoustical Terminology, American National
Standards Institute, 1973.
[5] Brian C. J. Moore, An Introduction to the Psychology of Hearing,
Academic Press, 4th Edition, 1997.
[6] Lawrence E. Kinsler, Austin R. Frey, Alan B. Coppens, and James
V. Sanders, Fundamentals of Acoustics, John Wiley and Sons, 3rd
Edition, 1982.
[7] E. Zwicker and H. Fastl, Psychoacoustics: Facts and Models,
Springer, 2nd Edition, 1999.
[8] Leo L. Beranek, Acoustical Measurements, American Institute of
Physics, 1988.
[9] Garay-Vega, Lisandra; Hastings, Aaron; Pollard, John K.;
Zuschlag, Michael; and Stearns, Mary D., Quieter Cars and the Safety
of Blind Pedestrians: Phase 2, John A. Volpe National Transportation
Systems Center, DOT HS 811 496 October 2011, available at http://www.nhtsa.gov/DOT/NHTSA/NVS/Crash%20Avoidance/Technical%20Publications/2011/811496.pdf.
Issued in Washington, DC on January 7, 2013, under authority
delegated in 49 CFR 1.95.
Christopher J. Bonanti,
Associate Administrator for Rulemaking.
[FR Doc. 2013-00359 Filed 1-9-13; 4:15 pm]
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