Analysis of army-wide hearing conservation database for hearing profiles related to crew-served and individual weapon systems.

Damage-risk criteria (DRC) for noise exposures are designed to protect 95% of the exposed populations from hearing injuries caused by those noise exposures. The current DRC used by the US military follows OSHA guidelines for continuous noise. The current military DRC for impulse exposures follows the recommendations from the National Academy of Sciences--National Research Council Committee on Hearing, Bioacoustics, and Biomechanics (CHABA) and are contained in the current military standard, MIL-STD-1474D "Noise Limits." Suggesting that the MIL-STD for impulse exposure is too stringent, various individuals have proposed that the DRC for exposure to high-level impulses be relaxed. The purpose of this study is to evaluate the current hearing status of US Army Soldiers, some of whom can be, by their military occupational specialties (MOS), reasonably expected to be routinely exposed to high-level impulses from weapon systems. The Defense Occupational and Environmental Health Readiness System--Hearing Conservation (DOEHRS-HC) was queried for the hearing status of enlisted Soldiers of 32 different MOSs. The results indicated that less than 95% of the Soldiers in the DOEHRS-HC database were classified as having normal hearing. In other words, the goal of the DRC used for limiting noise injuries (from continuous and impulse exposures) was not stringent enough to prevent hearing injuries in all but the most susceptible Soldiers. These results suggest that the current military noise DRC should not be relaxed.