Active Cochlea Auditory Signal Processing Model Studies

Sharp frequency selectivity,extreme sensitivity and wide dynamic range are the main features of the human hearing.These unique features of hearing cannot be demonstrated by any passive transducers previously proposed.Experimental observations,such as otoacoustic emission,demonstrated that the process of cochlear signal processing is not passive and linear,which would be completely characterized by a frequency analyzer.The nonlinear characteristics of hearing would be shown with the participation of the active mechanism.Hopf cochlear model has been proposed to explain the nonlinear phenomena of hearing and is of great significance.However,the problem of adjusting the bifurcation point is involved in this model,and the mechanism of how to adjust to the critical point is not clear in the cochlea.Under this background,an adaptive force was introduced by us.The force is related to the velocity.Then,the nonlinear dynamic differential equation of the basilar membrane vibration with the adaptive force is established.The nonlinear differential equation is calculated by the standard four step Runge Kutta method.Numerical simulation demonstrated that the adaptive active-force driven system exhibits nonlinear characteristics of the auditory system,such as nonlinear dynamic compression effect,combination tone generation(two-tone distortion)and two-tone suppression.Finally,effect of the active model extracting signal in noise was study.The results showed that the active system has stronger ability to detect signal in noise.