THE PSYCHOPHYSICS OF LOW-FREQUENCY ACOUSTIC HEARING IN ELECTRIC AND ACOUSTIC STIMULATION (EAS) AND BIMODAL PATIENTS

This paper provides a review of the current literature on psychophysical properties of low-frequency hearing, both before and after implantation, with a focus on frequency selectivity, nonlinear cochlear processing, and speech perception in temporally modulated maskers for bimodal listeners as well as patients with hearing preservation in the implanted ear and receiving combined electric and acoustic stimulation (EAS). In this paper we review our work, the work of others, and report results not previously published for speech perception in steady-state and temporally fluctuating maskers; the degree of masking release and frequency resolution for 11 bimodal, 6 hearing preservation patients; and 5 control subjects with normal hearing. The results demonstrate that a small masking release is possible with acoustic hearing in just one ear, with the degree of masking release being correlated with the low-frequency pure tone average in the non-implanted ear; furthermore, frequency selectivity as defined by the width of the auditory filter was not correlated with the degree of masking release. Descriptions of the clinical utility of hearing preservation in the implanted ear for improving speech perception in complex listening environments, as well as directions for the future, are discussed.