Acute acoustic trauma - a clinical investigation and prognosis in 433 symptomatic soldiers.

An audiological and clinical study was carried out on 433 soldiers suffering from symptomatic acute acoustic trauma (AAT). The severity of AAT was similar following exposure to different types of firearms. The typical subjective complaints were tinnitus and hearing loss and the more severe the objective hearing loss, the more frequent were the typical subjective symptoms. It seems that there are critical sound pressure levels and critical frequencies below which the remnants of infectious processes in the middle ear may have a protective effect on the cochlea in cases of exposure to noise, whereas above these critical levels and frequencies the injurious influence of noise appears to be enhanced. The best known treatment for AAT seems to be removal from further exposure to noise. Further exposure to noise had a significant worsening influence on the average hearing status, while removal from noise significantly improved the audiometric status.