Attenuation of high-level acoustic impulses by hearing protectors

Abstract

Attenuation of acoustic impulses by hearing protectors was measured in peak level ranges of 115–135 dB and 145–170 dB. The impulses were generated by a loudspeaker system in the low range of levels and by a blast of air expanding from a cylinder in the high level range. Transmission loss method was used to determine the difference between the peak level under the earmuff and outside the earmuff for over 30 different types of earmuffs. The measurements confirm that attenuation of high-level impulses depends on their peak level. In the 115–135 dB range the difference between the peak level outside and under the earmuff is approximately constant. In the 145–170 dB range, as the impulse level is increased, the level under the earmuff increases to a lesser extent. The peak-to-peak level characteristics determined for the 115 to 170 dB level range substantially differ for various types of protectors and may be a useful indicator of the effectiveness of protectors for impulse noise. [Work supported by the State Committee for Scientific Research Grants Nos. <cn>III-7.03<cnx> and <cn>III-6.07<cnx>.]