Hearing loss risk from exposure to shooting impulses in workers exposed to occupational noise

The effect of shooting impulses on hearing was analysed in 150 professional forest workers exposed to noise from chain saws. The exposure to shooting impulses (Lesi) was designed to take into account the peak levels of shooting impulses, their number and use of hearing protectors. Hearing loss was dependent on Lesi even after allowing for the age of subjects and their exposure to chain saw noise. Hearing threshold levels were compared between pairwise matched groups with high and low Lesi. Proper matching was achieved for age, chain saw noise, salicylate consumption, blood pressure, cholesterol, smoking and vibration-induced white finger symptoms. The workers with high Lesi had 9 dB greater hearing loss at 4 kHz and 10 dB greater hearing loss at 8 kHz than those with low Lesi, the difference being significant at P < 0.05 level. In evaluation of noise-induced hearing loss the exposure to shooting impulses from different calibre weapons should be determined since they increase the extent of hearing loss. The present study describes the Lesi method which more accurately evaluates the harmful effects of shooting noise impulses on hearing.