A cochlear model using feedback from motile outer hair cells

A model of cochlear vibrations based upon motile outer hair cells (OHCs) has been developed using physiologically demonstrated phenomena. Rapid longitudinally directed OHC forces are connected in such a way as to form a negative-feedback system. The responses at the higher frequencies (greater than 1 kHZ) are quite realistic: they have properly shaped amplitude curves with large tip-to-tail ratios (30-50 dB), Q10's of 2-6, and 'shoulders' at frequencies an octave below the resonant frequency. The phases are also quite realistic, though asymptoting at somewhat lower values (about -6 pi radians) than observed physiologically. The responses in the apical section are not so realistic. The form of the OHC force is physically unrealizable, but realizable forms are discussed.