Latent cochlear damage in personal stereo users: a study based on click-evoked otoacoustic emissions

To assess the effects of use of personal stereo systems (PS) on hearing by means of the objective measure of transient-evoked otoacoustic emissions.

People aged between 10 and 59 years who had otoacoustic emissions recorded by the National Acoustic Laboratories between 1989 and 1997 were eligible for inclusion. Recordings from participants with hereditary disorders or any form of aural disease (e.g., otitis media, otosclerosis, fluctuant hearing loss, Meniere's syndrome, or exposure to ototoxic substances) were excluded.

Transient-evoked otoacoustic emission (TEOAE) records were obtained with a standard 260 repetitions of an 80 dB train of clicks used for recording outer hair cell activity. The measure of otoacoustic emission strength was the Otodynamics ILO88 variable Waverepro%. For each participant, all the key factors relating to their hearing history were assessed from patient referral information or from demographic information obtained in writing at the time of recording either in the form of a detailed questionnaire or verbal assessment. Otoacoustic emission data were analysed according to age, industrial noise exposure and personal stereo use.

Usable otoacoustic emission records were obtained from 1724 people (1066 males and 658 females). Otoacoustic emission strength declined with age, and was significantly lower in males than females, lower in people exposed to industrial noise than those not exposed, and significantly lower in users of personal stereo systems than non-users. People with both kinds of noise exposure had values which were significantly lower again, indicating an additive effect.

As only 39 people with PS exposure admitted any hearing problems, decline in otoacoustic emission strength forewarns premature hearing loss in personal stereo users.