[Code of Federal Regulations]
[Title 49, Volume 4]
[Revised as of October 1, 2003]
From the U.S. Government Printing Office via GPO Access
[CITE: 49CFR325.5]

[Page 754]
 
                        TITLE 49--TRANSPORTATION
 
        CHAPTER III--FEDERAL MOTOR CARRIER SAFETY ADMINISTRATION,
                      DEPARTMENT OF TRANSPORTATION
 
PART 325--COMPLIANCE WITH INTERSTATE MOTOR CARRIER NOISE EMISSION STANDARDS--Table of Contents
 
                      Subpart A--General Provisions
 
Sec. 325.5  Definitions.

    (a) Statutory definitions. All terms defined in the Noise Control 
Act of 1972 (Pub. L. 92-574, 86 Stat. 1234) are used as they are defined 
in that Act.
    (b) Definitions in standards. All terms defined in Sec. 202.10 of 
the Interstate Motor Carrier Noise Emission Standards, 40 CFR 202.10, 
are used as they are defined in that section.
    (c) Additional definitions. (1) Hard test site means any test site 
having the ground surface covered with concrete, asphalt, packed dirt, 
gravel, or similar reflective material for more than \1/2\ the distance 
between the microphone target point and the microphone location point.
    (2) Soft test site means any test site having the ground surface 
covered with grass, other ground cover, or similar absorptive material 
for \1/2\ or more of the distance between the microphone target point 
and the microphone location point.
    (3) Ground cover means any of various low, dense-growing plants, 
such as ivy, myrtle, low weeds, or brush.
    (4) Traffic railing means any longitudinal highway traffic barrier 
system installed along the side or median of a highway. For the purpose 
of this part, a traffic railing must have at least 35 percent of its 
vertical height, from the ground surface to the top of the railing, open 
to free space in order to qualify as an acceptable object within a noise 
measurement test site. Further, for the purposes of this part, posts or 
other discrete supports shall be ignored when ascertaining open free 
space.
    (5) Relatively flat when used to describe a noise measurement site 
means a site which does not contain significant concave curvatures or 
slope reversals that may result in the focusing of sound waves toward 
the microphone location point.