{"data":{"id":"us/40-cfr-201.21","jurisdiction":"us","citation":"40 CFR 201.21","heading":"Quantities measured.","body":"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.","path":["Title 40—Protection of Environment","CHAPTER I—ENVIRONMENTAL PROTECTION AGENCY","SUBCHAPTER G—NOISE ABATEMENT PROGRAMS","PART 201—NOISE EMISSION STANDARDS FOR TRANSPORTATION EQUIPMENT; INTERSTATE RAIL CARRIERS","Subpart C—Measurement Criteria"],"source_url":"https://www.ecfr.gov/api/versioner/v1/full/2026-08-25/title-40.xml","current_through":"2026-08-25","vintage":"","retrieved_at":"2026-08-27T02:26:04Z","sha256":"b7fc6f42d165bfc4646f8bc25f3880533a8aba9dd8f9c0b3e7f6f146977d90ac","source_id":"us-cfr","stale":true,"prev":"us/40-cfr-201.20","next":"us/40-cfr-201.22"},"notice":"GroundRules: Original legal text. Not legal advice."}