The Silicon Cochlea:. from Biology to Bionics

The silicon cochlea maps the traveling-wave architecture of the biological cochlea into a silicon chip. Such an architecture is an efficient way of implementing a bank of wide-dynamic-range frequency-analysis channels in both biology and electronics [1]. However, in both biology and electronics, gain control is essential in ensuring that the architecture is robust to parameter changes, and in attaining wide dynamic range, a fact that has not been widely appreciated. A silicon cochlea with distributed gain control is likely to be advantageous as a front end in future cochlear-implant processors to improve patient performance in noise and to implement the computationally intensive algorithms of the biological cochlea with very low power. We implement a computer simulation of a filter-cascade cochlear model with distributed gain control that incorporates several important features such as multiband compression, an intertwining of filtering and compression, masking, and an ability to tradeoff the preservation of spectral contrast with the preservation of audibility. The particular gain control algorithm that we discuss successfully reproduces cochlear frequency response curves, and represents an example of a class of distributed-control algorithms that could yield similar results.