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  • § 325.1
    Scope of the rules in this part.
  • § 325.3
    Effective date.
  • § 325.5
  • § 325.7
    Allowable noise levels.
  • § 325.9
    Measurement tolerances.
  • § 325.11
    Issuance, amendment, and revocation of the rules in this part.
  • § 325.13
    Inspection and examination of motor vehicles.
  • § 325.21
    Scope of the rules in this subpart.
  • § 325.23
    Type of measurement systems which may be used.
  • § 325.25
    Calibration of measurement systems.
  • § 325.27
    Use of a windscreen.
  • § 325.31
    Scope of the rules in this subpart.
  • § 325.33
    Site characteristics; highway operations.
  • § 325.35
    Ambient conditions; highway operations.
  • § 325.37
    Location and operation of sound level measurement system; highway operations.
  • § 325.39
    Measurement procedure; highway operations.
  • § 325.51
    Scope of the rules in this subpart.
  • § 325.53
    Site characteristics; stationary test.
  • § 325.55
    Ambient conditions; stationary test.
  • § 325.57
    Location and operation of sound level measurement systems; stationary test.
  • § 325.59
    Measurement procedure; stationary test.
  • § 325.71
    Scope of the rules in this subpart.
  • § 325.73
    Microphone distance correction factors.
  • § 325.75
    Ground surface correction factors.
  • § 325.77
    Computation of open site requirements—nonstandard sites.
  • § 325.79
    Application of correction factors.
  • § 325.91
    Exhaust systems.
  • § 325.93

Part 325

§ 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 § 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.

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


Although we make every effort to assure that the information we provide is complete and accurate, it is not intended to take the place of published agency regulations. Regulations issued by the U.S. Department of Transportation and its Operating Administrations are published in the Federal Register and compiled in the U.S. Code of Federal Regulations (CFR). Copies of appropriate volumes of the CFR in book format may be purchased from the Superintendent of Documents, U.S. Government Printing Office, or examined at many libraries.

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