Introduction A single exposure to high level impulse noise in shooting ranges can cause permanent hearing loss. Aim of our cross sectional study was to compare the hearing threshold among workers exposed to high level impulse noise in shooting ranges to that in a sample of the general population occupationally and not occupationally exposed to noise.
Methods We monitored exposure to noise during the shooting activities. We also collected questionnaire information and measured the hearing threshold by pure-tone audiometry in 428 exposed workers in shooting range. The age-adjusted mean hearing threshold level from 2,5 to 8 Khz in both ears, expressed in dB, was compared by two study group (800 and 295 people) using a t test for independent samples.
Results During shooting activities, the standard for peak acoustic pressure was regularly exceeded with readings as high as 148.5 dB (C). The mean age of the military group was 39 (SD ± 9) years. We found audiometric evidence of hearing loss in 129/428 workers (30.1%), 61 (47.3%) with bilateral involvement and 68 (52.7%) with unilateral involvement. In this last group, the left ear was more frequently affected. The mean hearing thresholds at the frequency of 3–4-6 and 8 KHz did not significantly vary between the military and the reference subgroups.
Discussion Despite the high level exposure to peak impulse noise, the low annual frequency of training in the shooting range and the regular use of appropriate headsets seem to effectively protect the hearing function in the tested workers.
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