Firearms noise and hearing conservation: hearing protection fit testing, noise assessment and hearing surveillance

摘要

Background. Noise induced hearing loss (NIHL) continues to be a prevalent problem in Military Service. Purpose. To assess the 'SureFire' earplug, a Hearing Protective Device (HPD), within the context of a hearing conservation programme. Methods. The Sperian 'VeriPro' system was used to test the HPD attenuation. Otoacoustic emissions (OAE) base-line testing assessed base-line status of hearing. Noise exposure during test firing was measured using a B&K precision noise level meter, and a post firing OAE test was carried out to measure any deterioration in hearing due to excess noise exposure. Results. There was a 'between ears' difference in HPD fitting, with better attenuation in right ears. The HPDs were rated to reduce the noise by at least 15 dB in 84% of those exposed. In practice 84% of individuals would have achieved attenuation of between 8.4 and 23.6 dBA. The noise levels during the practice averaged 110 dBA, the actual exposure being 94 dBA, with 84% receiving between 86.4 and 101.6 dBA The OAE testing did not show any significant before and after differences. Discussion. Some individuals achieved good HPD fit, some quite poor. The average noise levels received were excessive, but the daily noise dose would have been within acceptable limits because of the short duration of exposure. This may explain the non-significant differences in OAEs. We recommend that individuals should only use HPDs which are 'fit proven'. Additional testing under more typical conditions with a larger group is required, but OAEs show promise as a practical monitoring tool.