Recent developments in firearms noise and hearing conservation: hearing protection fit testing, noise measurement and hearing surveillance

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 'VeriPro' system was used to test the HPD attenuation, with otoacoustic emission (OAE) 'baseline' hearing tests. Noise exposure was measured during test firing, and a post exposure OAE test was carried out to measure any deterioration in hearing due to excess noise exposure. Results. Better attenuation was achieved in right ears. The HPDs were rated to reduce the noise by at least 15 dB in 84% of those exposed, the actual attenuation lying in the range between 8.4 and 23.6 dBA. The median noise level was 110 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 was within acceptable limits because of the short duration of exposure, possibly explaining 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.