Abstract:
A novel mathematical technique is presented for modeling the linear and nonlinear properties of the cochlear transduction process. This new nonlinear system identification procedure (Bendat, 1990) has several advantages over classical techniques used for analyzing nonlinear systems. With this technique, nonlinear systems may be modeled as a linear system in parallel with any number of finite-memory nonlinear systems. Higher-order nonlinear terms can be more easily computed with this technique than with others such as volterra kernel analysis. Furthermore, a broadband signal such as a transient signal can be used to characterize the cochlea over a wide frequency band. This makes the application of this procedure ideal for modeling cochlear transduction process with transient evoked otoacoustic emissions data. Otoacoustic emissions were recorded in response to finite impulse response (FIR) pulses from 11 subjects with normal hearing. System identification procedures were implemented using third- and fifth-order polynomial models. Based on the input and output records, system properties were estimated. Coherence measures tested the goodness-of-fit of the chosen model. The identified systems were used to predict the systems' response to two-tone stimuli. The fifth-order model predictions were in better accordance with previously reported data on acoustic distortion products.