ON MECHANICAL PREPROCESSING IN THE COCHLEA - THE 3 GREAT HEARING THEORIES COMBINED

Since otoacoustic emissions were discovered, the old idea of a second (active) filter (1) in the cochlea has been pursued with considerable dedication. In this contribution a concept explaining the action of th e second filter is presented, which is derived from high-frequency res onance: The outer hair cells are excited when the traveling wave break s rather than when it reaches its peak amplitude (2). They vibrate at a much higher frequency, i.e. their mechano-electrical resonant freque ncy. The amplitude of the exciting stimulus is very small, but in keep ing with the chaos theory it is amplified by self-organization to a le vel sufficient for physiologic excitation. This concept helps to expla in the hitherto unexplained frequency changes of spontaneous otoacoust ic emissions. (C) 1996 Academic Press, Inc.