Mechanical cochlear-partition parameter variation in a box-cochlea model

Abstract

Place and frequency responses were determined for one-, two-, and three-dimensional fluid motion in a box-cochlea model with a stiffness-damping-mass cochlear-partition representation having exponentially decreasing stiffness, exponentially varying damping, and constant mass densities per unit length. The rational-function frequency-domain impedance for that partition model was represented as a function of a single variable, the generalized cochlear place, a linear combination of cochlear place, and the logarithm of stimulus frequency. When cochlear mass density was relatively large, the best generalized cochlear place was a constant, with the result that the slope of the linear best (ordinary) place versus log-frequency graph depended only on the rate of partition stiffness decrease; in that case, three orders of magnitude of presented stimulus frequency mapped best places over the entire cochlear length only when the stiffness changed by six orders of magnitude. When cochlear mass density was relatively small, the slope of best generalized place versus log frequency could be made more negative for the same stiffness rate, and the same range of best-place versus frequency variation was achieved with less stiffness change along the cochlear length.