Delayed speech feedback in normal hearing and conductive hearing loss, with and without a functioning stapedius muscle.

Abstract

Normal ears, otosclerotic ears with normal hearing after stapedectomy, and ears with pure conductive hearing loss from otosclerosis and packing of the ear canal, were subjected to a delayed speech feedback test (DSF-test). The results showed no difference in the DSF-effect between the normal ears and the normal hearing operated otosclerotic ears. Neither was there any difference between the nonoperated otosclerotic and the normal hearing ears with an artificial hearing loss. The results suggest that activity in the stapedius muscle has no influence on the DSF-effect in normal hearing ears and in ears with conductive hearing impairment. The DSF-effect, however, was almost double in the non-operated otosclerotic ears and in ears with artificial hearing loss. This may be due to the acoustic energy from the earphones, in the pure conductive hearing losses of about 40 dB, reaching the cochlea both by air and bone conduction in almost equal amounts.