UBC Theses and Dissertations
A comparison of threshold and supratheshold measurement of temporal integration in normal and cochlea-impaired ears Smith, Faye Evelyn
The present study was undertaken in order to investigate temporal integration at threshold and suprathreshold levels in normal-hearing and cochlea-impaired subjects, and also to examine the effect of frequency on the amount of integration for each group. Thresholds for 500-and 20-msec tone pulses were established in a Bekesy tracking procedure by 20 subjects with normal hearing acuity and 20 subjects with noise-induced hearing loss. The amount of threshold shift between the long-and short-duration tones, or temporal integration, was examined as a function of subject group and signal frequency (500 Hz and 4000 Hz) both in quiet and in the presence of a white noise masker. Results of this study showed that the two groups could be differentiated by the mean threshold shift between the two tone durations, although overlap between groups was marked. The amount of integration observed for the group with normal hearing was frequency-dependent in both quiet and masked conditions The group of subjects with cochlear impairment exhibited normal integration values at 500 Hz, where no hearing loss was present and significantly smaller than normal values at 4000 Hz, where they demonstrated cochlear pathology. The masker altered the amount of temporal integration of the hearing-impaired group at both signal frequencies, while the normal subjects were unaffected by the presence of the masker at 4000 Hz. Critical ratios which were calculated from the masked thresholds showed larger values for the hearing-impaired group than the normal-hearing group. The present results support the use of brief-tone audiometry in the clinical assessment of cochlear impairment. However, the group overlap in performance which was demonstrated in this study indicates that an individual's performance using this assessment must be interpreted cautiously. That is, a subject cannot be reliably assigned to either group in this experiment when the amount of integration falls within the region of overlap.
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