All auditory processing starts with a cochlea. Silicon auditory processing must start with a silicon cochlea. The fundamental structure in a cochlea is the cellular membrane. The silicone basilar membrane is a transmission line with a velocity of propagation that can be tuned electrically. Output taps, where the signal can be observed, are located at intervals alone the line. We can think about the taps as crude inner hair cells. Unfortunately, we have about 3500; we will be lucky to have 1000. On the other hand, we can make many delay-line elements; the delay element we use in this delay line is the second-order section described in Chapter 11. We expect this model delay line to be good enough to duplicate approximately the dynamics of the second-order system of fluid mass and membrane stiffness, including the active role of the outer hair cells.
-- From C. Mead's book "Analog VLSI and Neural Systems"