You are here

  • § 325.1
    Scope of the rules in this part.
  • § 325.3
    Effective date.
  • § 325.5
    Definitions.
  • § 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
    Tires.

Part 325
COMPLIANCE WITH INTERSTATE MOTOR CARRIER NOISE EMISSION STANDARDS

§ 325.53: Site characteristics; stationary test.

(a)(1) The motor vehicle to be tested shall be parked on the test site. A microphone target point shall be established on the ground surface of the site on the centerline of the lane in which the motor vehicle is parked at a point that is within 3 feet (.9 m) of the longitudinal position of the vehicle's exhaust system outlet(s). A microphone location point shall be established on the ground surface not less than 31 feet (9.5 m) and not more than 83 feet (25.3 m) from the microphone target point. Within the test site is a triangular measurement area. A plan view diagram of a standard test site, having an open site within a 50-foot (15.2 m) radius of both the microphone target point and the microphone location point, is shown in Figure 2.
(2) Measurements may be made at a test site having smaller or greater dimensions in accordance with the rules in subpart F of this part.
(b) The test site must be an open site, essentially free of large sound-reflecting objects. However, the following objects may be within the test site, including the triangular measurement area:
(1) Small cylindrical objects such as fire hydrants or telephone or utility poles.
(2) Rural mailboxes.
(3) Traffic railings of any type of construction except solid concrete barriers (see § 325.5(c)(4)).
(4) One or more curbs having a height of 1 foot (.3 m) or less.
(c) The following objects may be within the test site if they are outside of the triangular measurement area of the site:
(1) Any vertical surface, regardless of size (such as a billboard), having a lower edge more than 15 feet (4.6 m) above the ground.
(2) Any uniformly smooth surface slanting away from the vehicle with a slope that is less than 45 degrees above the horizontal.
(3) Any surface slanting away from the vehicle that is 45 degrees or more and not more than 90 degrees above the horizontal, if all points on the surface are more than 15 feet (4.6 m) above the surface of the ground in the test site.
(d) The surface of the ground within the measurement area must be relatively flat. (See § 325.5(c)(5)). The site shall be a “hard” site. However, if the site is determined to be “soft,” the correction factor specified in § 325.75(b) of this part shall be applied to the measurement.

Citation: [40 FR 42437, Sept. 12, 1975, as amended at 41 FR 10227, Mar. 10, 1976; 54 FR 50385, Dec. 6, 1989]

Disclaimer:

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.

The CFR may also be viewed online at http://ECFR.gpoaccess.gov.