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consequence, as of July Table 2. Center frequencies and sound pressure levels for two-band alert signals 2021, manufacturers
must install an AVAS in
all new EVs in the EU
One-Third Octave- Band Center Frequency (Hz)
Minimum A-Weighted SPL (dB)
A-Weighted Band Sum (dB)
Example of Measured Alert Signal
315
47
47
400
47
47
500
47
55*
630
47
46
800†
47†
46†
1,000
47
57
46
1,250
47
55*
1,600
47
46
2,000
47
45
2,500
47
45
3,150
47
44
One-third octave-band center frequencies and minimum A-weighted SPLs for two-band alert signals are shown for the condition “constant vehicle pass-by speeds equal or greater than 20 km/h but less than 30 km/h” as defined in FMVSS No. 141. †One of the two bands meeting the minimum requirements must be one of the 315- to 800-Hz bands and the second needs to be one of the 1,000- to 3,150-Hz bands. *Example of a measured alert signal meeting the minimum level requirements and the band sum criterion of FMVSS No. 141 due to the one-third octave bands.
(2014). Moreover, all newly manufactured EVs, to which FMVSS No. 141 applies in the United States, have had to comply with this minimum sound safety standard as of September 2020 (FMVSS, 2019).
The US standard establishes
performance requirements
for pedestrian alert
sounds that are designed
to reduce the number of
injuries resulting from EV
crashes with pedestrians
by providing a sound level
and characteristics that are
detectable and recognized by
pedestrians. An alert sound
is understood as a vehicle-
emitted sound that enables
pedestrians to discern vehicle
presence, direction, location, and operation (FMVSS, 2016).
Pedestrian Alert Sounds
There are two options for designing pedestrian alert sounds in compliance with FMVSS No. 141. In one option, four nonadjacent one-third octave bands spanning no fewer than 9 of the 13 bands from 315 to 5,000 Hz must exceed specified required minimum one-third octave- band levels. Table 1 shows the performance requirements for four-band alert sounds designed for vehicle constant pass-by speeds from 20 km/h to just under 30 km/h.
The second option is for an alert sound in two nonadjacent one-third octave bands from 315 to 3,150 Hz if it meets a minimum A-weighted sound pressure level in each band and a band sum requirement. In addition, one of the two one-third octave bands meeting the minimum level requirements must be in bands ranging from 315 to 800 Hzandtheothermustbebetweenthemidbandfrequencies of 1,000 to 3,150 Hz. Table 2 shows the performance
requirements for two-band alert signals for the same vehicle constant pass-by speeds as shown in Table 1.
Originally in the notice of proposed rulemaking (NHTSA, 2013), a change in frequency as a function of vehicle speed was proposed to allow pedestrians to detect vehicle acceleration and deceleration. But after further consideration, this pitch-shifting requirement was replaced in the final rule with an increase in sound pressure level by a specified amount because expected repeatability issues in compliance evaluations. Instead of pitch shifting, a relative change in level of 3 dB is required to signify acceleration and deceleration when moving from 1 relevant operating condition to the next (e.g., changing from 10 to 20 km/h constant-speed condition).
UNECE Regulation No. 138.01 requires that EVs must use an AVAS if the vehicle exterior noise without an additional alert sound does not meet specified overall levels with a margin of +3 dB(A). If the vehicle does not meet these
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