[Code of Federal Regulations]
[Title 49, Volume 5]
[Revised as of October 1, 2007]
From the U.S. Government Printing Office via GPO Access
[CITE: 49CFR325.39]

[Page 13]
 
                        TITLE 49--TRANSPORTATION
 
                      DEPARTMENT OF TRANSPORTATION
 
PART 325_COMPLIANCE WITH INTERSTATE MOTOR CARRIER NOISE EMISSION 
STANDARDS--Table of Contents
 
      Subpart D_Measurement of Noise Emissions; Highway Operations
 
Sec.  325.39  Measurement procedure; highway operations.

    (a) In accordance with the rules in this subpart, a measurement 
shall be made of the sound level generated by a motor vehicle operating 
through the measurement area on the traveled lane of the highway within 
the test site, regardless of the highway grade, load, acceleration or 
deceleration.
    (b) The sound level generated by the motor vehicle is the highest 
reading observed on the sound level measurement system as the vehicle 
passes through the measurement area, corrected, when appropriate, in 
accordance with the rules in subpart F of this part. (Table 1 in Sec.  
325.7 lists the range of maximum permissible sound level readings for 
various test conditions.) The sound level of the vehicle being measured 
must be observed to rise at least 6 dB(A) before the maximum sound level 
occurs and to fall at least 6 dB(A) after the maximum sound level occurs 
in order to be considered a valid sound level reading.

[40 FR 42437, Sept. 12, 1975, as amended at 41 FR 10227, Mar. 10, 1976]