49 CFR § 325.23 - Type of measurement systems which may be used.
---
identifier: "/us/cfr/t49/s325.23"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "49 CFR § 325.23 - Type of measurement systems which may be used."
title_number: 49
title_name: "Transportation"
section_number: "325.23"
section_name: "Type of measurement systems which may be used."
chapter_name: "FEDERAL MOTOR CARRIER SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION"
subchapter_number: "A"
subchapter_name: "GENERAL REGULATIONS"
part_number: "325"
part_name: "COMPLIANCE WITH INTERSTATE MOTOR CARRIER NOISE EMISSION STANDARDS"
positive_law: false
currency: "2026-03-24"
last_updated: "2026-03-24"
format_version: "1.1.0"
generator: "[email protected]"
authority: "42 U.S.C. 4917; 49 U.S.C. 301; and 49 CFR 1.87."
regulatory_source: "40 FR 42437, Sept. 12, 1975, unless otherwise noted."
cfr_part: "325"
---
# 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,
<sup>1</sup>
[^] throughout the applicable frequency range for either:
<sup>1</sup> 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.