Noise induced hearing loss in military helicopter aircrew--a review of the evidence.

Noise Induced Hearing Loss (NIHL) has been recognised for some time. In the military environment one group of personnel at risk are Army helicopter aircrew who are exposed to continuous noise levels of up to 100 dB(A) in flight. The evidence for the damaging effect of this occupational noise is reviewed and some of the difficulties in drawing conclusions are highlighted. The current protection offered for the Mk 4 helmet is discussed and the incorporation of Active Noise Reduction (ANR) is suggested as a likely way of ensuring that the in-flight noise exposure in Army aircrew is kept as low as possible.