[Effect of noise on the auditory transduction].

The effects of noise on the auditory transduction and the temporary and permanent threshold shifts (TTS and PTS) are reviewed in relation to the physiology, the morphology and the mechanics of the Corti's organ and especially of the outer hair cells. The modification of the mechanical characteristics of the stereocilia: decrease of stiffness, shortening of the rootlets, softening of the interciliary links...reduce the number of ionic channels which are opened during the mechanical excitation of the Corti's organ. This reduction modifies greatly the behavior of the "cochlear amplifier" which is located at the level of the outer hair cells and is responsible for the auditory sensitivity at threshold and the frequency selectivity. Permanent damages to the stereocilia of the hair cells following exposure to noise seem to be the main factor responsible for the apparition and the extent of the hearing losses. The influence cof several parameters: amplitude, duration, frequency..., on TTS and PTS are reviewed and the phenomenon of the half-octave shift is described.