[Code of Federal Regulations]
[Title 49, Volume 4]
[Revised as of October 1, 2004]
From the U.S. Government Printing Office via GPO Access
[CITE: 49CFR210.25]

[Page 61]
 
                        TITLE 49--TRANSPORTATION
 
       CHAPTER II--FEDERAL RAILROAD ADMINISTRATION, DEPARTMENT OF 
                             TRANSPORTATION
 
PART 210_RAILROAD NOISE EMIS SION COMPLIANCE REGULATIONS--Table of Contents
 
                    Subpart B_Inspection and Testing
 
Sec. 210.25  Measurement criteria and procedures.

    The parameters and procedures for the measurement of the noise 
emission levels are prescribed in the Standards.
    (a) Quantities measured are defined in Sec. 201.21 of the 
Standards.
    (b) Requirements for measurement instrumentation are prescribed in 
Sec. 201.22 of the Standards. In addition, the following calibration 
procedures shall be used:
    (1)(i) The sound level measurement system including the microphone 
shall be calibrated and appropriately adjusted at one or more nominal 
frequencies in the range from 250 through 1000 Hz at the beginning of 
each series of measurements, at intervals not exceeding 1 (one) hour 
during continual use, and immediately following a measurement indicating 
a violation.
    (ii) The sound level measurement system shall be checked not less 
than once each year by its manufacturer, a representative of its 
manufacturer, or a person of equivalent special competence to verify 
that its accuracy meets the manufacturer's design criteria.
    (2) An acoustical calibrator of the microphone coupler type designed 
for the sound level measurement system in use shall be used to calibrate 
the sound level measurement system in accordance with paragraph 
(b)(1)(i) of this section. The calibration must meet or exceed the 
accuracy requirements specified in section 5.4.1 of the American 
National Standard Institute Standards, ``Method for Measurement of Sound 
Pressure Levels,'' (ANSI S1.13-1971) for field method measurements.
    (c) Acoustical environment, weather conditions, and background noise 
requirements are prescribed in Sec. 201.23 of the Standards. In 
addition, a measurement tolerance of 2 dB(A) for a given measurement 
will be allowed to take into account the effects of the factors listed 
below and the interpretations of these effects by enforcement personnel:
    (1) The common practice of reporting field sound level measurements 
to the nearest whole decibel;
    (2) Variations resulting from commercial instrument tolerances;
    (3) Variations resulting from the topography of the noise 
measurement site;
    (4) Variations resulting from atmospheric conditions such as wind, 
ambient temperature, and atmospheric pressure; and
    (5) Variations resulting from reflected sound from small objects 
allowed within the test site.