SELF-SUPPRESSION IN A LOCALLY ACTIVE NONLINEAR MODEL OF THE COCHLEA -A QUASI-LINEAR APPROACH

Mechanical input-output functions of the cochlea for pure-tone stimuli are nonlinear for frequencies around the characteristic frequency. To simulate these functions, a long-wave model of the cochlea containing a saturating pressure generator (located at the site of the outer hai r cells) is solved in the frequency domain with a quasilinear method. In this method distortion products in the basilar-membrane (BM) respon se are treated as perturbations and the nonlinear pressure waveform is approximated by the first-order Fourier component. Because the satura ting pressure generator forms part of a feedback loop the solution of the model is achieved in a number of iteration steps. Model results sh ow flattening of the BM response at higher input pressures; this prope rty, called self-suppression, is due to saturation of the pressure gen erator. The resulting input-output functions display the main features of experimental curves. The third-order distortion product in the BM velocity is always more than 25 dB below the primary BM velocity and d oes not influence the results of the computation; this justifies the u se of the quasilinear method.