Measurement instrumentation.

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§ 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[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:

Expand Table

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

Measurement section Source Decibels1
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

(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.


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