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.
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    \102\ NHTSA-2011-0148-0025, available at www.regulations.gov.
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    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

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.
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    \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

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.

    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.
---------------------------------------------------------------------------

    \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.
---------------------------------------------------------------------------

    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

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.
---------------------------------------------------------------------------

    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.
---------------------------------------------------------------------------

    \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

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 <IP_ADDRESS>
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
<IP_ADDRESS> 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

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.
---------------------------------------------------------------------------

    \109\ Public Law 111-373, Sec.  2(3), 124 Stat. 4086 (2011).
---------------------------------------------------------------------------

    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).
---------------------------------------------------------------------------

    \110\ Springer Handbook of Acoustics, Thomas D. Rossing (Ed.),
Springer Science and Media LLC, New York, 2007, page 472.
---------------------------------------------------------------------------

    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.
---------------------------------------------------------------------------

    \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.
---------------------------------------------------------------------------

    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

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.
---------------------------------------------------------------------------

    \112\ See footnote 36.
---------------------------------------------------------------------------

    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\
---------------------------------------------------------------------------

    \113\ http://www.regulations.gov/#!documentDetail;D=NHTSA-2011-
0148-0022.
---------------------------------------------------------------------------

    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.
---------------------------------------------------------------------------

    \114\ http://www.unece.org/trans/main/wp29/wp29wgs/wp29grb/qrtv_8.html.
---------------------------------------------------------------------------

    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

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 <IP_ADDRESS> 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.
---------------------------------------------------------------------------

    \115\ NHTSA-2011-0148-0031.
---------------------------------------------------------------------------

    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

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

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.

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

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.........
----------------------------------------------------------------------------------------------------------------

    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.

    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

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.
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    \118\ 472 F.2d 659 (D.C. Cir. 1972).
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    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.
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    \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.
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    \120\ Available at http://media.wix.com/ugd/64a49a--
43313ad70e7c40f43150cf747b2e5c44.pdf?dn=A520040+-+DSTN+-
+White+paper+electric+cars+-+av122410+-+ECT+LR.pdf.

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    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