49 CFR §325.73
Verified against eCFR.gov as of June 20, 2026View official text on eCFR.gov ↗
If the distance between the microphone location point and the microphone target point is other than 50 feet (15.2 m), the maximum observed sound level reading generated by the motor vehicle in accordance with § 325.39 of this part or the numerical average of the recorded maximum observed sound level readings generated by the motor vehicle in accordance with § 325.59 of this part shall be corrected as specified in the following table: