Extended high-frequency thresholds in noise-induced hearing loss.

Air-conduction and bone-conduction thresholds were measured in the conventional audiometric frequency ranges, and air-conduction alone in the extended high-frequency range of 9-18 kHz in 167 males with a history of occupational noise exposure. The subjects were grouped according to age. Hearing loss in the conventional frequency range was classified in different grades. Threshold elevation in the extended high-frequency range was present in all age groups and grades of conventional frequency hearing loss. An age effect in the extended high-frequency range was present only in the lowest grades of conventional frequency noise-induced hearing loss.