Comparison of the nonlinear responses of a transmission-line and a filter cascade model of the human cochlea

Abstract

Models of the mammalian cochlea have been proposed in a number of ways and they have varying degree of realism and complexity. The transmission-line (TL) models are faithful to the physiology, particularly in terms of cochlear nonlinearity, but are computationally demanding. The pole-zero filter cascade (PZFC) model, however, is much more efficient to implement, but the nonlinearity is included implicitly, using an automatic gain control network. In this study, the connection between the linear responses of these two models is first discussed, followed by a comparison of their nonlinear responses in terms of self-suppression and two-tone suppression on the level of the basilar membrane. Both models are capable of simulating dynamic range compression as measured on the cochlear partition, but the TL model is more reasonable in representing twotone suppression, with the PZFC having lower suppression thresholds and over-predicting the suppression due to high-side suppressors. Further tuning of its parameters and structure, especially the automatic gain control (AGC) network may be possible to make it more compatible with these experimental observations. After adapting the PZFC model to have a more realistic nonlinear behavior, its use for investigating auditory signal processing such as masking effects, and hence as a front-end processor for acoustic signals can be enhanced, while retaining its computational efficiency.

Design of FIR filters with magnitude specifications

“…In deriving the integer-and non-integer-B u GAFs, we are only concerned with filter representations for spatially independent parallel filterbank configurations. We are not interested in spatially dependent configurations [25] such as the non-spatially causal transmission lines [26] and the spatially causal filterbanks in cascade configurations. The former is a fundamentally different form of signal processing 2 and the latter has pole-zero cancellations for the filter which is generally undesirable for most realizations.…”