Direct Determination of the Adequacy of Hearing Protective Devices for Use with the M198, 155mm Towed Howitzer

摘要

The peak sound pressure levels of the M198, 155mm howitzer firing the M203 propelling charge are far in excess of the exposure limits set forth in the Army hearing conservation criteria. The levels are of a sufficient magnitude that there is serious question whether adequate hearing protection is available. This study provides direct evidence for the adequacy of the E-A-R earplug to protect against the impulse noise of the M198/M203. Fifty-nine volunteers were exposed to a progression of impulse noise levels produced by the M198 and tested for temporary threshold shift. It was found that the threshold shift exhibited by 95 percent of the volunteers was within acceptable limits after exposure to 12 rounds of M203 charge. This finding is interpreted to mean that these earplugs provide adequate hearing protection. In addition, volunteers were evaluated for evidence of laryngeal injury and intestinal injury. None was found. Keywords: Impulse Noise; Hearing Loss; Acoustics; Hearing Conservation.