Sound attenuation of the indoor/outdoor range E-A-R plug

Abstract

The sound attenuation provided by the AOSafety Indoor/Outdoor Range E-A-R Plug was examined. This device, currently used in military operations in several countries, is comprised of two plugs that provide conventional ("indoor" plug) and level-dependent sound reduction (the "outdoor" plug), respectively. The effects of the user's gender and repeated fittings were explored. Eight men and eight women were tested on two separate occasions. Unoccluded and protected hearing thresholds were measured for each of nine one-third octave noise bands centered at 0.125 to 8 kHz. Attenuation was calculated as the difference between these two measures. The indoor plug provided 21 to 40 dB of sound reduction across the frequencies tested, closely matching the manufacturer's specification. The outdoor plug provided 5 to 22 dB of conventional attenuation, suggesting that it might serve as a safe means of conventional and level-dependant attenuation in hearing-impaired users. No differences were found in relation to gender or repeated fittings.