Effects of microphone type and distance upon the spectra of speech sounds

Thesis (S.B. and M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1999.Includes bibliographical references (leaf 71).by Dameon C. Harrell.S.B.and M.Eng

Speech Communication

Contains table of contents for Part V, table of contents for Section 1, reports on six research projects and a list of publications.C.J. Lebel FellowshipDennis Klatt Memorial FundNational Institutes of Health Grant R01-DC00075National Institutes of Health Grant R01-DC01291National Institutes of Health Grant R01-DC01925National Institutes of Health Grant R01-DC02125National Institutes of Health Grant R01-DC02978National Institutes of Health Grant R01-DC03007National Institutes of Health Grant R29-DC02525National Institutes of Health Grant F32-DC00194National Institutes of Health Grant F32-DC00205National Institutes of Health Grant T32-DC00038National Science Foundation Grant IRI 89-05249National Science Foundation Grant IRI 93-14967National Science Foundation Grant INT 94-2114

Effect of Repeated Exposure and Attention on Stream Segregation of Stimuli at the Fission Boundary

Neural processes of the auditory system decompose and perceptually organize mix- tures of sound such that we can hear and follow separate auditory streams: the speech of a single person at a party or the melodies of different instruments in an orchestra. Decades of research has yielded much insight into the perceptual dynamics of stream segregation. Yet, some perceptual attributes of stream segregation are not well defined. One example of this is a concept referred to as the fission boundary (FB). The FB is generally con- ceived as a threshold below which stream segregation cannot occur or can only occur with a small probability. Here, I demonstrate that this prior conception of the FB was pri- marily determined by measurement method, as opposed to perceptual limitations of the auditory system, and suggest an alternate definition of the FB. Prior investigations into the neural underpinnings of stream segregation have revealed cortical correlates, but animal models have suggested that stream segregation may be- gin with neural processes in the brainstem. Two recent studies of stream segregation with human participants recorded the frequency-following response (FFR) as a measure of subcortical neural activity. The studies reported inconsistent results: one study provid- ing evidence of an FFR correlate of stream segregation and the other finding no effect of steaming in the FFR. In Experiment 2 of this dissertation, participants performed a stream segregation task while FFRs were recorded simultaneously. The results are consistent with the prior study showing no effects of streaming on the FFR. While the FFR reflects sensory processes and experience dependent long-term plasticity, it may not reflect im- mediate perceptual states associated with stream segregation

Speech Communication

Contains table of contents for Part IV, table of contents for Section 1, reports on six research projects, one report on the research laboratory and a list of publications.C.J Lebel FellowshipDennis Klatt Memorial FundNational Institutes of Health Grant R01-DC00075National Institutes of Health Grant R01-DC01291National Institutes of Health Grant R01-DC01925National Institutes of Health Grant R01-DC02125National Institutes of Health Grant R01-DC02978National Institutes of Health Grant R01-DC03007National Institutes of Health Grant R29-DC02525-01A1National Institutes of Health Grant F32-DC00194National Institutes of Health Grant F32-DC00205National Institutes of Health Grant T32-DC00038National Science Foundation Grant IRI 93-14967National Science Foundation Grant INT 94-2114