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40 CFR § 201.22 - Measurement instrumentation. 

---
identifier: "/us/cfr/t40/s201.22"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "40 CFR § 201.22 - Measurement instrumentation."
title_number: 40
title_name: "Protection of Environment"
section_number: "201.22"
section_name: "Measurement instrumentation."
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"
---

# 201.22 Measurement instrumentation.

(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 
<sup>1</sup>
[^] 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:

<sup>1</sup> American National Standards are available from the American National Standards Institute, Inc., 1430 Broadway, New York, NY 10018.

Table 1—Sound Level Corrections When Using a Type 2 (or S2A) Instrument

| Measurement section | Source | Decibels |
| --- | --- | --- |
| 201.24 | Locomotives | 0 |
|  | Rail cars | 0 |
|  | Locomotive load cell test stand | 0 |
| 201.26 | Retarder | 4 |
|  | Car coupling | 2 |
| 201.27 | Locomotive load cell test stand | 0 |
|  | Stationary locomotive | 0 |
| Amount of correction to be subtracted from measured level (dB). |  |  |

(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.