The problem of noise-induced hearing loss (NIHL) was objectively and systematically investigated by diagnosing three workers who complained of tinnitus and hearing disturbance.

Atypical hearing loss is diagnosed as a work-related disease by using general medical methods, such as environmental survey, neurological examination, otoscopy, pure-tone audiometry, speech audiometry, otoacoustic emissions (OAE), auditory-evoked potentials, and interview on the history of past disease, family and occupation.

Three results were found according to the work-related hearing loss as follows; (1) hearing loss that is caused by exposure to continuous noise of less than 85 dB(A) or impact noise of greater than 135 dB peak, (2) mixed hearing loss that has progressed due to noise with past otitis media, and (3) atypical hearing loss that showed remarkable differences between air and bone conduction due to tinnitus.

The criteria for work-related hearing loss should be carefully investigated by considering exposure to impact noise, the effect of continuous noise on mixed hearing loss patients, and the hearing loss caused by tinnitus.