A serial study of noise exposure and hearing loss in a group of small and medium size factories.

Abstract

This paper describes a 3-year study of 277 workers exposed to sound levels ranging from 81·5 dB to 104·5 dB (re 0·0002 dynes/cm2). Progression of hearing loss during the exposure period was determined by annual pure-tone audiometric tests. Presbycusis data were derived from audiometric tests on a control population, not normally exposed to noise in excess of 70 dB. The existence of a hazard to hearing was assessed by the presence of the characteristic 3 kc/s-6 kc/s “dip” in the audiograms, and by comparison of the progression of hearing loss during the exposure, with that anticipated due to ageing. In two factories employees exposed to mean noise levels not exceeding the modified Burns-Littler Damage Risk Criterion showed evidence of hearing loss extending to, or below 2000 c/s. A preliminary enquiry into the psycho-social effects of noise indicated that employees probably under-estimated their noise exposure in previous employment, as assessed by interference with speech communication.