Doctoral Dissertations

David Mason

Date of Award

8-1983

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Speech and Hearing Science

Major Professor

Igor Nabelek

Committee Members

Samuel Burchfield, Anna Nabelek, Stephen Handel

Abstract

This study investigated the effects of the duration of the inter-stimulus-interval (ISI) and the tone duration on the acoustic reflex threshold (ART) of normally hearing and hearing-impaired subjects at the tone frequencies of 250, 1000, and 4000 Hz. The ART was measured for ISI durations of 10, 20, 50, 100, 200, 500, 1000, and 2000 ms and tone durations of 10, 20, 50, 100, 200, 500, and 1000 ms. Significant differences were found between groups of subjects, among frequencies, tone, and ISI durations. Significant interactions between factors indicated that; (1) differences between the ARTs for the normally hearing and hearing-impaired groups increased as the tone frequency increased; (2) the differences between the groups' ARTs increased as the ISI duration decreased; (3) the ARTs for the 4000-Hz tones decreased more sharply than for either the 250 or 1000-Hz tones as the tone duration increased; (5) the ARTs decreased more as the tone duration increased when the ISI duration was long than when it was short. Additional conclusions included: (1) the level at which the ART occurs increases as the hearing threshold level of the subject increases, but the ARTs for the hearing-impaired subjects tend to occur at a lower sensation level; (2) the ART does not appear to occur at either a constant loudness or sensation level across frequencies; (3) the ART does not appear to occur at either a constant loudness or sensation level across tone durations; (4) the time constants for the ART temporal integration curves are longer than the time constants for either loudness or hearing threshold curves, and the constants increase with increasing frequency; (5) the ARTS for short duration tones with high repetition rates are lower than for long continuous tones; (6) the amount that the ART decreases as the tone duration increases from 10 to 1000 ms with a constant ISI duration of 2000 ms, or as the ISI duration decreases from 2000 to 10 ms with a constant tone duration of 10 ms is negatively correlated with hearing threshold levels.

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