Effects of loud tones on the inner ear: a combined electrophysiological and ultrastructural study.

Guinea pigs were exposed to a 10 kHz pure tone and damage to the cochlea was investigated immediately after exposure, or after a recovery period ranging from 18-25 days. Structural damage was assessed using scanning electron microscopy and functional damage estimated using the N1 threshold audiogram. Exposure at 106 dB for 1 h caused obvious abnormalities of outer hair cell stereocilia. The location and extent of this damage was related to the immediate or long term deficits in the N1 threshold audiogram.