Cochlear micromechanics—A physical model of transduction

One of the basic questions which has persisted in the field of hearing theory is the still unresolved mechanical action of hair-cell transduction. The fundamental problem that has historically plagued researches is the discrepancy between mechanically measured tuning of basilar membrane motion and neurally measured tuning. In this paper we show that the difference between these two measures appears to be accounted for by a specific, physically motivated, micromechanical model. This model gives rise to a spectral zero which we identify as the ’’second-filter’’ of cochlear transduction. For high-frequency fibers this zero resides at a fixed frequency ratio below CF (characteristic frequency) while for fibers having low-frequency CF’s the zero appears to go to zero frequency faster than CF. In this paper we first present and analyze the assumed mechanical model. We then briefly discuss a possible specific physical realization for the nonlinearity of cochlea mechanics. The nonlinear model is based on dynamical variations in outer hair cell stereocilia stiffness.