Design of an Analogue VLSI Model of an Active Cochlea

Abstract

A model of an active cochlea featuring a frequency selective gain adaptation is proposed. The model is developed for analogue VLSI implementation and is based on the original ’’analog electronic cochlea‘‘ proposed by Lyon and Mead (1988) which consists of a second-order lowpass filter cascade. At any position along the cochlea, the gain is locally controlled by the output level at this position through the quality factor of the second-order lowpass filter which best participates to this local gain. In order to achieve a 40dB compression with a limited local quality factor, the pseudoresonance of the cascade is used. A careful analysis of the functional model, supported by realistic computer simulations, shows the validity of the model by comparison with its biological counterpart. All the building blocks for an analogue VLSI implementation are proposed, taking into account the major technological limitations of a standard CMOS process.