Band sum means the combination of Sound Pressure Levels (SPLs) from selected bands that produce an SPL representing the sound in all of these bands. Band sum is calculated with the following equation:
where SPLi is the sound pressure level in each selected band.
Electric vehicle means a motor vehicle with an electric motor as its sole means of propulsion.
Front plane of the vehicle means a vertical plane tangent to the leading edge of the vehicle during forward operation.
Hybrid vehicle means a motor vehicle which has more than one means of propulsion for which the vehicle's propulsion system can propel the vehicle in the normal travel mode in at least one forward drive gear or reverse without the internal combustion engine operating.
Rear plane means a vertical plane tangent to the leading edge of the rear of the vehicle during operation in reverse.
Trim level is defined to mean a subset of vehicles within the same model designation with the same body type and which are alike in their general level of standard equipment, such as a "base" trim level of a vehicle model. Vehicles with only minor trim differences that are unlikely to affect vehicle-emitted sound are not considered different for the purposes of this safety standard.
Table 1-One-Third Octave Band Min. SPL Requirements for Sound When Stationary and Constant Speeds Less Than 10km/h
One-third octave band center frequency, Hz | Min SPL, A-weighted dB |
315 | 39 |
400 | 39 |
500 | 40 |
630 | 40 |
800 | 41 |
1000 | 41 |
1250 | 42 |
1600 | 39 |
2000 | 39 |
2500 | 37 |
3150 | 34 |
4000 | 32 |
5000 | 31 |
Table 2-One-Third Octave Band Min. SPL Requirements for Sound while in Reverse
One-third octave band center frequency, Hz | Min SPL, A-weighted dB |
315 | 42 |
400 | 41 |
500 | 43 |
630 | 43 |
800 | 44 |
1000 | 44 |
1250 | 45 |
1600 | 41 |
2000 | 42 |
2500 | 40 |
3150 | 37 |
4000 | 35 |
5000 | 33 |
Table 3-One-Third Octave Band Min. SPL Requirements for Constant Pass-by Speeds Greater Than or Equal to 10 km/h but Less Than 20 km/h
One-third octave band center frequency, Hz | Min SPL, A-weighted dB |
315 | 45 |
400 | 44 |
500 | 46 |
630 | 46 |
800 | 47 |
1000 | 47 |
1250 | 48 |
1600 | 44 |
2000 | 45 |
2500 | 43 |
3150 | 40 |
4000 | 38 |
5000 | 36 |
Table 4-One-Third Octave Band Min. SPL Requirements for Constant Pass-by Speeds Greater Than or Equal to 20 km/h but Less Than 30 km/h
One-third octave band center frequency, Hz | Min SPL, A-weighted dB |
315 | 52 |
400 | 51 |
500 | 52 |
630 | 53 |
800 | 53 |
1000 | 54 |
1250 | 54 |
1600 | 51 |
2000 | 51 |
2500 | 50 |
3150 | 47 |
4000 | 45 |
5000 | 43 |
Table 5-One-Third Octave Band Min. SPL Requirements for 30-32 km/h Pass-By
One-third octave band center frequency, Hz | Min SPL, A-weighted dB |
315 | 56 |
400 | 55 |
500 | 57 |
630 | 57 |
800 | 58 |
1000 | 58 |
1250 | 59 |
1600 | 55 |
2000 | 55 |
2500 | 54 |
3150 | 51 |
4000 | 49 |
5000 | 47 |
Table 6-One-Third Octave Band Minimum Requirements for Two-Band Alert
Vehicle speed | A-weighted SPL, dB(A) | |
Minimum in each band | Band sum | |
Reverse | 40 | 48 |
Stationary and up to but not including 10 km/h | 40 | 44 |
10 km/h up to but not including 20 km/h | 42 | 51 |
20 km/h up to but not including 30 km/h | 47 | 57 |
30 km/h | 52 | 62 |
Table 7-Minimum Relative Volume Change Requirements
Critical operating speed intervals | Minimum relative volume change, dB |
Between: | |
Stationary and 10 km/h | 3 |
10 km/h and 20 km/h | 3 |
20 km/h and 30 km/h | 3 |
Table 8-Overall SPL Corrections for Ambient Noise
Difference between vehicle measurement and ambient noise level | Correction |
Greater than 10 dB | 0 dB. |
Greater than 8 dB but less than or equal to 10 dB | 0.5 dB. |
Greater than 6 dB but less than or equal to 8 dB | 1.0 dB. |
Greater than 4.5 dB but less than or equal to 6 dB | 1.5 dB. |
Greater than 3 dB but less than or equal to 4.5 dB | 2.5 dB. |
Less than or equal to 3 dB | Invalid test run. |
Table 9-1/3 Octave Band Corrections for Ambient Noise
Difference between vehicle 1/3 octave band sound pressure level and ambient noise level | Correction |
Greater than 6 dB | 0 dB. |
Greater than 4.5 dB but less than or equal to 6 dB | 1.5 dB. |
Greater than 3 dB but less than or equal to 4.5 dB | 2.5 dB. |
Less than or equal to 3 dB | Specific 1/3 octave band is not useable. |
Where:
i represents the 13 one-third octave bands and Normalized Band Leveli is the normalized one-third octave band value derived in S7.6.2.
49 C.F.R. §571.141