{"data":{"id":"us/40-cfr-201.22","jurisdiction":"us","citation":"40 CFR 201.22","heading":"Measurement instrumentation.","body":"(a) A sound level meter or alternate sound level measurement system that meets, as a minimum, all the requirements of American National Standard S1.4-1971 1 for a Type 1 (or S1A) instrument must be used with the “fast” or “slow” meter response chacteristic as specified in Subpart B. To insure Type 1 response, the manufacturer's instructions regarding mounting or orienting of the microphone, and positioning of the observer must be observed. In the event that a Type 1 (or S1A) instrument is not available for determining non-compliance with this regulation, the measurements may be made with a Type 2 (or S2A), but with the measured levels reduced by the following amount to account for possible measurement instrument errors pertaining to specific measurements and sources:\nTable 1—Sound Level Corrections When Using a Type 2 (or S2A) Instrument\nMeasurement section Source Decibels 1\n201.24 Locomotives 0\nRail cars 0\nLocomotive load cell test stand 0\n201.26 Retarder 4\nCar coupling 2\n201.27 Locomotive load cell test stand 0\nStationary locomotive 0\n1 Amount of correction to be subtracted from measured level (dB).\n(b) A microphone windscreen and an acoustic calibrator of the coupler type must be used as recommended by: (1) the manufacturer of the sound level meter or (2) the manufacturer of the microphone. The choice of both devices must be based on ensuring that Type 1 or 2 performance, as appropriate, is maintained for frequencies below 10,000 Hz.","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":"e1c224d0bcb4eef3b74f29378704d13d6db1e6f8365f9cd262a688655e696f2d","source_id":"us-cfr","stale":true,"prev":"us/40-cfr-201.21","next":"us/40-cfr-201.23"},"notice":"GroundRules: Original legal text. Not legal advice."}