Rejecting a cochlear-partition model with constant mass

Abstract

The question of whether a simple low-order, linear, passive model of cochlear-partition dynamics can account for ‘‘global’’ (overall stiffness change, range of best frequencies and best places) and ‘‘local’’ (peakiness of frequency- and place-selectivity, amount of phase-angle change around the best place or frequency) attributes of cochlear response to tones in Békésy’s observations in cadavers remains unresolved. With answering that question the goal, a simple stiffness-damping-mass model of cochlear-partition dynamics with constant mass and exponentially varying stiffness and damping, was investigated computationally using a box-cochlea model of cochlear hydrodynamics. Constrained only by Békésy’s reported change in stiffness by about two orders of magnitude, the model’s global and local response attributes were determined over a reasonably exhaustive set of mechanical parameter values. It was found that the only combinations of mechanical parameters resulting in reasonable cochlear maps had magnitude-response shapes neither qualitatively resembling nor quantitatively consistent with observations by Békésy or anyone else, postmortem or in vivo.