40 CFR § 201.21 - Quantities measured.

---
identifier: "/us/cfr/t40/s201.21"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "40 CFR § 201.21 - Quantities measured."
title_number: 40
title_name: "Protection of Environment"
section_number: "201.21"
section_name: "Quantities measured."
chapter_name: "ENVIRONMENTAL PROTECTION AGENCY"
subchapter_number: "G"
subchapter_name: "NOISE ABATEMENT PROGRAMS"
part_number: "201"
part_name: "NOISE EMISSION STANDARDS FOR TRANSPORTATION EQUIPMENT; INTERSTATE RAIL CARRIERS"
positive_law: false
currency: "2026-03-24"
last_updated: "2026-03-24"
format_version: "1.1.0"
generator: "[email protected]"
authority: "Noise Control Act of 1972, sec. 17(a), 86 Stat. 1234 (42 U.S.C. 4916(a))."
regulatory_source: "45 FR 1263, Jan. 4, 1980, unless otherwise noted."
cfr_part: "201"
---


# 201.21 Quantities measured.

The quantities to be measured under the test conditions described below, are the A-weighted sound levels for “fast” or “slow” meter response as defined in the American National Standard S1.4-1971.