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

Abstract

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.

Keywords: cochlear implant; electric and acoustic stimulation (EAS); hearing preservation; masking release.

Figures

Figure 1

Audiometric thresholds for the non-implanted ears of bimodal and EAS patients.

Figure 2

Pre- and post-implant audiograms for the implanted ear of EAS patients.

Figure 3

Speech reception thresholds for bimodal patients in 4 listening conditions. Data for both steady-state noise and 10 Hz square-wave modulated noise masking conditions are plotted.

Figure 4

Speech reception thresholds for EAS patients in 6 listening conditions. Data for both steady-state noise and 10 Hz square-wave modulated noise masking conditions are plotted.

Figure 5

Masking release (in dB) as a function of the low-frequency pure tone average.