Off-campus UMass Amherst users: To download dissertations, please use the following link to log into our proxy server with your UMass Amherst user name and password.
Non-UMass Amherst users, please click the view more button below to purchase a copy of this dissertation from Proquest.
(Some titles may also be available free of charge in our Open Access Dissertation Collection, so please check there first.)
Effect of onset cues on lateralization and binaural masking
Abstract
The effects of onset interaural time differences (ITD) on lateralization and detection of binaural broadband click trains with alternating and non-alternating ITDs were examined under earphones. Three ITDs were employed: 0 us, or $\pm$ 500 us (right-leading and left-leading). Within each train, ITDs were the same (all-left, all-right, and centered) or alternated between two of the three values. The interclick interval was 2 milliseconds and the train duration was 250 milliseconds. Lateralization has investigated with a broadband acoustic pointer with variable delay. Listeners' pointer adjustments were essentially dominated by onset ITD. Detection thresholds were obtained with two broadband continuous maskers, left-leading and diotic. MLDs of nearly 12 dB were seen for the right-leading non-alternating probe when the masker was left leading. For the alternating ITD probes, thresholds improved when one or both ITDs in the probe differed from that of the masker. Threshold improvement was independent of the onset ITD. Similar results were obtained with the diotic masker, with the magnitude of the MLD being somewhat less. To rule out the possibility of the onset being masked by the noise masker at threshold, MLDs were obtained for trains with an exponentially decaying envelope with the onset 20 dB above the trailing portion of the trains. Detection thresholds obtained in a duration discrimination task revealed MLDs of smaller magnitude, but even with the onset enhanced, no effect of onset ITD was seen. These results showed that while onsets strongly influenced lateralization of the relatively long duration signals used in these experiments, MLDs were determined by the ongoing interaural differences. Subjects' performance in lateralization showed some inter-subject variability and variability across signals. Three out of four subjects also lateralized more strongly to the left than to the right. When lateralization was determined as a function of signal sensation level (SL), the effect of onset ITD became weaker or disappeared at low SLs. These results are generally consistent with the statistical decision theory based hypothesis of Houtgast and Plomp (1968) and suggested that while onset cues dominated lateral position, detection depended on the time-varying steady-state cues in the signals.
Subject Area
Audiology|Educational psychology|Experimental psychology|Psychology
Recommended Citation
Balakrishnan, Uma, "Effect of onset cues on lateralization and binaural masking" (1994). Doctoral Dissertations Available from Proquest. AAI9420597.
https://scholarworks.umass.edu/dissertations/AAI9420597