StacksVerified U.S. regulatory reference

49 CFR §325.23

Verified against eCFR.gov as of June 20, 2026View official text on eCFR.gov ↗
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:
  1. (a)A Type 1 sound level meter;
  2. (b)A Type 2 sound level meter; or
  3. (c)A Type S sound level meter which has—
    1. (1)A weighing frequency response;
    2. (2)Fast dynamic characteristics of its indicating instrument; and
    3. (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.