[Code of Federal Regulations]

[Title 49, Volume 5]

[Revised as of October 1, 2005]

From the U.S. Government Printing Office via GPO Access

[CITE: 49CFR325.53]



[Page 13-14]

 

                        TITLE 49--TRANSPORTATION

 

                      DEPARTMENT OF TRANSPORTATION

 

PART 325_COMPLIANCE WITH INTERSTATE MOTOR CARRIER NOISE EMISSION STANDARDS

--Table of Contents

 

        Subpart E_Measurement of Noise Emissions; Stationary Test

 

Sec. 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.



[[Page 14]]



[GRAPHIC] [TIFF OMITTED] TC01AP91.011



    (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 Sec. 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 Sec. 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 Sec. 325.75(b) of this part shall be applied to the 

measurement.



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

54 FR 50385, Dec. 6, 1989]