49 C.F.R. § B to Part 227
This appendix is mandatory.
Employers must select one of the following three methods by which to estimate the adequacy of hearing protector attenuation.
I. Derate by Type
Derate the hearing protector attenuation by type using the following requirements:
A. Subtract 7 dB from the published Noise Reduction Rating (NRR).
B. Reduce the resulting amount by:
1. 20% for earmuffs,
2. 40% for form-able earplugs, or
3. 60% for all other earplugs.
C. Subtract the remaining amount from the A-weighted TWA. You will have the estimated A-weighted TWA for that hearing protector.
II. Method B From ANSI S12.6-1997 (Reaffirmed 2002)
Use Method B, which is found in ANSI S12.6-1997 (Reaffirmed 2002) "Methods for Measuring the Real-Ear Attenuation of Hearing Protectors." The Director of the Federal Register approves the incorporation by reference of this standard in accordance with 5 U.S.C. 552(a) and 1 CFR part 51 . You may obtain a copy of the incorporated standard from the American National Standards Institute at 1819 L Street, NW., Washington, DC 20036, or http://www.ansi.org. You may inspect a copy of the incorporated standard at the Federal Railroad Administration, Docket Room, 1200 New Jersey Avenue, SE., Washington, DC 20590, or at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, call 202-741-6030, or go to http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html.
III. Objective Measurement
Use actual measurements of the level of noise exposure (as an A-weighted SLOW response dose) inside the hearing protector when the employee wears the hearing protector in the actual work environment.
49 C.F.R. §B to Part 227