Otoacoustic emissions in the general adult population of Nord-Trøndelag, Norway: I. Distributions by age, gender, and ear side.

Transient evoked otoacoustic emissions (TEOAEs) and distortion-product otoacoustic emissions (DPOAEs) are described as a function of age, gender and ear side in an unscreened adult population of 6415 subjects comprising a subsample of the 51975 subjects from the Nord-Trøndelag Hearing Loss Study. While most descriptions of OAEs are from samples selected based on hearing threshold, the present sample is from a less selected general population. The OAEs were recorded as a part of the programme of a general health screening. The large sample size provided accurate estimations of mean values. TEOAEs were analysed at 1, 2 and 4 kHz. DPOAEs were measured with f2 frequencies of 2, 3, 4, 6, and 8 kHz. Signs of bimodality were seen in the OAE density distributions of the > or = 45-year age group. The OAEs declined as a function of age, with the steepest gradient between 30 and 65 years. OAEs were generally higher in females than in males and in right ears than in left ears. Controlling for pure-tone thresholds reduced some of the effects of age, gender and ear side.