Models for Approximating Basilar Membrane Displacement - Part II. Effects of Middle-Ear Transmission and Some Relations between Subjective and Physiological Behavior

This report presents the second half of results of a study on the peripheral ear. There are two objectives: (1) to derive computational models for approximating the mechanical displacement of the basilar membrane when the sound pressure at the eardrum is known, and (#) to demonstrate certain relations between subjective behavior measured experimentally and physiological behavior calculated from the models. The report describes a rational function approximation of middle-ear transmission. This residt, in combination with previously derived models for the inner ear, permits an analytical approximation of basilar membrane displacements in both apical and basal regions. Because the models are rational functions, they can, if desired, be simulated by lumped-constant electrical networks. Their computational tractability also permits straightforward approximations to temporal and spatial derivatives of displacement. Relations between computed membrane displacement and subjective behavior are illustrated for several psychoacoustic phenomena, namely pitch perception, binaural lateralization, binaural time-intensity trade, threshold discrimination, and pure-tone masking. The extent to ivhich some of these phenomena can be correlated with, identified in, and predicted by the mechanical operation of the peripheral ear appears to be substantial. Part I of this report 1 described three analytical models for approximating the displacement of the basilar membrane when the human ear is stimulated by sound.