Workplace evaluation of earmuff-type hearing protectors

Abstract

The measurement of attenuation values for hearing protectors as used by personnel at the work site give a more realistic estimation of the protection afforded the worker. Head movement, sweating, chewing, and other physical factors may affect the integrity of the hearing protector resulting in different attenuation values than those obtained from the standard ANSI test method. A miniature, two-channel, frequency-modulated, telemetry system has been developed to measure attenuation values for earmuff-type protectors. Data from small microphones located inside and outside the hearing protector are transmitted to a remote receiver (up to 200 ft) and tape recorder for later analysis. The wireless link between the worker and observer allows the gathering of data while leaving the worker unencumbered to perform normal duties. Repetitive laboratory tests using combinations of nine subjects and eleven different muffs have provided correction factors for the system relative to the ANSI S3.19-1974 psychoacoustic standard method for measurement of earmuff attenuation. The results of numerous field trials in terms of NRR, dBA reduction and octave-band attenuation values are presented for various muffs, occupations, and noise sources. These results are compared to those stated by the manufacturer.