Event-Based Neuromorphic Systems

4

Silicon Cochleas

While the previous chapter was about neuromorphic silicon retinas, this one is on silicon cochleas. The cochlea is biology’s sound sensor – it turns vibrations in the air into a neural signal. This chapter briefly explains the operation of the various components of the biological cochlea and introduces circuits that can simulate these components. Silicon cochlea designs typically divide the biological cochlea into several sections that are equally spaced along its length. Each section is then modeled by an electronic circuit. Silicon cochlea designs may be classified as 1D or 2D, depending on the coupling between these sections. Circuits for both variants are presented. They may also be classified as active or passive, depending on whether the quality factor of each cochlear section changes as a function of the output signal of the section or not. Details for both implementations are presented. A tree diagram at the end of the chapter illustrates the progression of silicon cochlea modeling.

4.1  Introduction

The biological cochlea is a bony, fluid-filled, spiral structure that forms the majority of the inner ear. It performs the transduction between the pressure signal representing the acoustic input and the neural signals that carry information to the brain. Figure 4.1 shows the location of the cochlea relative to other key features in the human ear.

The cochlea ...