CFR > Title 49 - Transportation > SUBTITLE B—Other Regulations Relating to Transportation > CHAPTER III—FEDERAL MOTOR CARRIER SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (Parts 300–399) > SUBCHAPTER A—GENERAL REGULATIONS (Parts 300–325) > PART 325—COMPLIANCE WITH INTERSTATE MOTOR CARRIER NOISE EMISSION STANDARDS > SUBPART C—Instrumentation (§325.21 to §325.27) > 325.23—Type of measurement systems which may be used.

325.23—Type of measurement systems which may be used.

The sound level measurement system must meet or exceed the requirements of American National Standard Specification for Sound Level Meters (ANSI S1.4-1971), approved April 27, 1971, issued by the American National Standards Institute, 1 throughout the applicable frequency range for either:

Code of Federal Regulations

Footnote(s): 1 Copies of the specification may be secured from the American National Standards Institute, 1430 Broadway, New York, New York, 10018.
(a) A Type 1 sound level meter;
(b) A Type 2 sound level meter; or
(c) A Type S sound level meter which has—
(1) A weighing frequency response;
(2) Fast dynamic characteristics of its indicating instrument; and
(3) A relative response level tolerance consistent with those of either a Type 1 or Type 2 sound level meter, as specified in section 3.2 of ANSI S1.4-1971.