Pure tone audiometry screening and ear examinations were conducted among 138 males working as machine and equipment operators occupationally exposed to intermittent noise of 85 to 105 dBA. Hearing loss up to 30 dB (preserved socially adequate hearing) was found in 25 workers. The hearing impairment was confirmed by distortion products of otoacoustic emissions measurements. A sharp increase in the frequency of cases can be found among the workers with service length over 10 years. While the frequency of the cases among workers with service length below 10 years is 5.45%, it is 26.5% among the subjects with service length over 10 years, with a gradual increase as a result of the increase in exposure duration. A positive correlation (p < 0.05) was found between the frequency of hearing impairment among the workers and the years of exposure to excessive noise levels. Some measures for preventing occupational noise-induced hearing loss were suggested.
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