Sharp mechanical tuning in a cochlear model without negative damping.

It is possible for a cochlear model without active negative damping to exhibit a mechanical response peak that is arbitrarily high and arbitrarily wide. Conventional active models rely on external energy inputs to the cochlea to produce the required peak shape. The new model proposed here produces very similar response profiles by assuming that outer hair cell stereocilia stiffness suppresses the mechanical motion in all regions basal of the response peak. Therefore, the model is not active in the usual sense of adding energy to the cochlea. The model suggests a reason for the differing basilar membrane structure in the arcuate and pectinate zones and simulates in vivo and postmortem responses similar to those measured in the real cochlea.