Attenuation performance of four hearing protectors under dynamic movement and different user fitting conditions.
Hum Factors 1990 Feb; 32(1):9-25
The purpose of this study was to develop and use a laboratory based protocol to estimate the influence of fitting procedure and movement activity during wearing periods on the achieved attenuation of four different hearing protective devices (HPDs). Forty subjects participated in this study with five men and five women randomly assigned to each of four HPD conditions. Psychophysical attenuation measurements at nine 1/3 octave bands from 125 to 8000 hertz (Hz) were obtained prior to, during, and following a 2 hour wearing stint that included periods of either highly kinematic but controlled work activity or vigorous temporomandibular movement. The subject fit condition resulted in significantly lower protection levels, from 4 to 14 decibels (dB) at 1000Hz and below for a premolded polymer earplug, a user molded foam earplug, and a double protector consisting of a muff over the foam plug. The muff alone was significantly more resilient to fitting effects on attenuation than were the plugs. Movement activity caused up to a 6dB significant reduction in frequency specific attenuation over time for the premolded plug, muff, and muff/plug combination. The compliant foam earplug was largely resistant to either type of movement effect but did benefit more than the other devices from use of the trained fit procedure. Implications of the results for hearing protector testing protocol, device selection, and user training are discussed.
NIOSH-Publication; NIOSH-Grant; Noise-induced-hearing-loss; Hearing-protection; Personal-protective-equipment; Safety-equipment; Safety-practices; Hearing-loss; Hearing-impairment; Ear-protectors; Ear-protection
Indus Engr and Operations Res Virginia Polytechnic Institute Blacksburg, VA Blacksburg, VA 24061
Virginia Polytechnic Inst and St Univ, Blacksburg, Virginia