DC Feedback: Noise levels inside locomotive cabs
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This month's installment of DC Feedback deals with noise levels inside locomotive cabs.
Dear Sir and Brother:
You have asked if the metal tag attached to the wall in the locomotive cab is a measurement of noise inside the cab.
The answer is no.
The measurements that are taken and placed on the badgeplate or tag are actually taken from outside the cab of the locomotive to fulfill requirements established by the Noise Control Act of 1972, required by the Environmental Protection Agency (EPA) and enforced by the Federal Railroad Administration (FRA). These measurements are not related to the levels of sound inside the cab.
The requirements for posting the information can be found in §49 CFR Part 210.27, they include:
"New locomotive certification.
"(a) A railroad shall not operate a locomotive built after December 31, 1979, unless the locomotive has been certified to be in compliance with the Standards.
"(b) The certification prescribed in this section shall be determined for each locomotive model, by either:
"(1) Load cell testing in accordance with the criteria prescribed in the Standards; or
"(2) Passby testing in accordance with the criteria prescribed in the Standards.
"(c) If passby testing is used under paragraph (b)(2) of this section, it shall be conducted with the locomotive operating at maximum rated horsepower output.
"(d) Each new locomotive certified under this section shall be identified by a permanent badge or tag attached in the cab of the locomotive near the location of the inspection Form F 6180.49. The badge or tag shall state:
"(1) Whether a load cell or passby test was used;
"(2) The date and location of the test; and
"(3) The A-weighted sound level reading in decibels obtained during the passby test, or the readings obtained at idle throttle setting and maximum throttle setting during a load cell test."
The regulation prescribes minimum compliance requirements for enforcement of the Railroad Noise Emission Standards established by the Environmental Protection Agency in 40 CFR Part 201 and with some exceptions applies to:
"the total sound emitted by moving rail cars and locomotives (including the sound produced by refrigeration and air conditioning units that are an integral element of such equipment), active retarders, switcher locomotives, car coupling operations, and load cell test stands, operated by a railroad as defined in 45 U.S.C. 22, under the conditions described in this part and in 40 CFR part 201."
The provisions do not apply to steam locomotives; street, suburban, or interurban electric railways unless operated as a part of the general railroad system of transportation; sound emitted by warning devices, such as horns, whistles, or bells when operated for the purpose of safety; special purpose equipment that may be located on or operated from rail cars; inert retarders, and locomotives (turbine powered) that cannot be connected by any standard method to a load cell.
The regulation prescribes that:
"(A)ny railroad that uses railroad equipment that is noise defective or engages in a car coupling operating that results in excessive noise according to the criteria established in this part and in the Standards is responsible for compliance with this part. Subject to §210.9, such railroad shall -
"(a) Correct the noise defect;
"(b) Remove the noise defective railroad equipment from service; or
"(c) Modify the car coupling procedure to bring it within the prescribed noise limits."
The regulation further describes the requirements for movement of noise defective locomotives and equipment; waiver processes; inspection and testing; measurement criteria and procedures; penalties, and procedures for certification that the locomotive meets the required Standards.
The actual limits of noise generated by the railroad can be found in the Appendix A of Part 210. The science of noise and the information in the Appendix is not easily described. Generally speaking, a stationary locomotive manufactured after 1979 should emit sound levels below 70 dB (A weighted sound) when at idle, as measured 100 feet from the source. Noise levels measured at the same distance for all other throttle settings should not exceed 87 dB while stationary and 90 dB while moving. There are other requirements for locomotives manufactured before 1979, switcher locomotives, yard equipment and facilities, moving rail cars, and car couplings, retarders, and load cell tests.
The requirements for locomotive cab noise are found in §49 CFR Part 229.121. The permissible limits are determined by a formula that considers level of sound, established and measurable sound characteristics, and assessed on the basis of exposure that is an eight-hour time-weighted average (TWA).
The noise level measurement in the locomotive cab is made "under typical operating conditions." The instruments used may be a sound level meter that conforms to a standard or an accurate and equally precise audiodosimeter. The sound level measurements are to be made with a sound level meter where:
"(T)he microphone shall be oriented vertically and positioned approximately 15 centimeters from and on axis with the crew member's ear. Measurements with an audiodosimeter shall be conducted in accordance with manufacturer's procedures as to microphone placement and orientation."
According to the "Locomotive Crashworthiness and Cab Working Conditions Report to Congress," FRA found that approximately one-third of a total of 69 locomotive engineers that were measured for sound exposure had TWA's (time weighted averages) above 87dB. One fourth of 216 measured locomotives had in-cab TWAs greater than 87dB. The actual noise dose is determined by a scientifically established formula. There can be sound levels in a locomotive cab far in excess of 87dB, particularly when the windows are open and the train horn is sounded, air brakes are vented into the cab, or when the radio volume is high. Long tours of duty, under noisy conditions, can expose locomotive engineers to noise levels above a threshold where hearing loss occurs. The threshold is generally accepted as 85dBA.
It's unfortunate that the only reference to noise associated with a locomotive has nothing to do with sounds inside the cab. This information may help you to understand what the badgeplate does and does not address and encourage you to wear hearing protection.
© 2000 Brotherhood of Locomotive Engineers