49 C.F.R. § 325.73 Microphone distance correction factors.1
Title 49 - Transportation
1 Table 1, in §325.7 is a tabulation of the maximum allowable sound level readings taking into account both the distance correction factors contained in §325.73 and the ground surface correction factors contained in §325.75. 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: [40 FR 42437, Sept. 12, 1975, as amended at 54 FR 50385, Dec. 6, 1989]
Title 49: Transportation
PART 325—COMPLIANCE WITH INTERSTATE MOTOR CARRIER NOISE EMISSION STANDARDS
Subpart F—Correction Factors
§ 325.73 Microphone distance correction factors.1
Table 2_Distance Correction Factors------------------------------------------------------------------------ The value dB(A) to be applied to the If the distance between the microphone location point and observed the microphone target point is sound level reading is_------------------------------------------------------------------------31 feet (9.5 m) or more but less than 35 feet (10.7 m)...... -435 feet (10.7 m) or more but less than 39 feet (11.9 m)..... -339 feet (11.9 m) or more but less than 43 feet (13.1 m)..... -243 feet (13.1 m) or more but less than 48 feet (14.6 m)..... -148 feet (14.6 m) or more but less than 58 feet (17.7 m)..... 058 feet (17.7 m) or more but less than 70 feet (21.3 m)..... +170 feet (21.3 m) or more but less than 83 feet (25.3 m)..... +2------------------------------------------------------------------------
