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Polar Spectrum Coding is a novel speech coding algorithm for narrowband voice communications. A polar Fourier transform of the signal is computed, and the magnitude and phase of the speech spectrum is encoded for transmission. The correlation between frames of speech signals is exploited to minimize the transmission rate required for intelligible speech. At the receiver, the encoded words are decoded and the spectrum reconstructed. An inverse Fourier transform is performed, and the result is the reconstructed speech waveform. Polar Spectrum Coding theory is explained. The sensitivities of various parameters on performance are explored, and performance in the presence of channel noise is measured. Directions for future research in the realm of Polar Spectrum Coding is suggested.

A procedure is presented that is capable of extracting various speaker features, and is of particular value for analyzing records containing single words and shorter segments of speech. By taking advantage of the fast convergence properties of adaptive filtering, the approach is capable of modeling the nonstationarities due to both the vocal tract and vocal cord dynamics. Specifically, the procedure extracts the vocal tract estimate from within the closed glottis interval and uses it to obtain a time-domain glottal signal. This procedure is quite simple, requires minimal manual intervention (in cases of inadequate pitch detection), and is particularly unique because it derives both the vocal tract and glottal signal estimates directly from the time-varying filter coefficients rather than from the prediction error signal. Using this procedure, several glottal signals are derived from human and synthesized speech and are analyzed to demonstrate the glottal waveform modeling performance and kind of glottal characteristics obtained therewith. Finally, the procedure is evaluated using automatic speaker identity verification. / Ph. D.

This study was designed to investigate whether learning style and attitudes toward voice input technology were related to performance in using the technology. Three null hypotheses were tested: (a) No differences exist in the performance in dictating a paragraph using voice input for individuals with different learning styles; (b) No differences exist in attitude toward voice input for individuals with different learning styles; and (c) No interaction exists for the performance scores for individuals with different learning styles and different attitudes toward voice input technology. The statistical procedure used to examine the hypotheses was analysis of variance. Participants were 50 students preparing to become vocational teachers enrolled in vocational education courses at Virginia Tech. Procedures involved having the participants complete three stages. First, they completed the Gregorc Style Delineator (GSD) learning style instrument. Due to a lack of individuals of one learning style category, abstract sequential (AS), only three learning style categories were used in the study. Second, they completed a background information sheet. Third, they participated in the voice-input training and dictation phase. Each student completed a one-hour session that included training, practice using voice input, and dictating a paragraph. Participants also completed the Attitude Toward Voice Input Scale developed by the researcher. It includes 21 attitude statements, 11 positively worded and 10 negatively worded. The first hypothesis was not rejected. A student's learning style does not relate to the performance of the student when dictating a paragraph using voice input technology. The second hypothesis was not rejected either. A student's attitude toward voice input technology was not related to learning style. The third hypothesis was also not rejected. A student's learning style, regardless of whether the student had a "high" or "low" attitude toward voice input, was not significantly related to performance in using voice input technology. However, the mean performance scores of individuals with concrete sequential (CS) learning styles with "high" and "low" attitudes did appear to be different. Those with "high" attitudes toward voice input had better performance scores than those with "low" attitudes toward the technology. / Ph. D.

The objective of this study was to develop a voice interface for the on-line catalog of VTLS. Three major components of the system, namely, voice recognition system, text-to-speech synthesizer, and screen review program, were identified. These components were selected after a comparative study of several commercially available systems. Once the components were selected they were integrated to form a complete voice recognition and synthesis system. Using this system, a voice interface was realized to suit the operations of VTLS. A telephone interface for the system was investigated and recommendations were made for future research. / Master of Science

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No description available.

From the start of their lives, infants and young children are surrounded by a tremendous amount of multimodal social information. One intriguing question in the study of early social cognition is how vital social information is detected and processed and how and when young infants begin to make sense of what they see and hear and learn to understand other people’s behavior. The overall aim of this thesis was to provide new insights to this exciting field. Investigating behavior and/or neural mechanisms in early life, the three different studies included in this thesis therefore strive to increase our understanding on perception and processing of social information. Study I used eye-tracking to examine infants´ observations of gaze in a third-party context. The results showed that 9-, 16- and 24-month-old infants differentiate between the body orientations of two individuals on the basis of static visual information. More particularly, they shift their gaze more often between them when the social partners face each other than when they are turned away from each other. Using ERP technique, Study II demonstrated that infants at the age of 4 to 5 months show signs of integrating visual and auditory information at a neural level. Further, direct gaze in combination with backwards-spoken words leads to earlier or enhanced neural processing in comparison to other gaze-word combinations. Study III, also an EEG investigation, found that children between 18 and 30 months of age show a desynchronization of the mu rhythm during both the observation and execution of object-directed actions. Also, the results suggest motor system activation when young children observe others’ mimed actions. To summarize, the findings reported in this thesis strengthen the idea that infants are sensitive to others´ gaze and that this may extend to third-party contexts. Also, gaze is processed together with other information, for instance words, even before infants are able to understand others’ vocabulary. Furthermore, the motor system in young children is active during both the observation and imitation of another person’s goal-directed actions. This is in line with findings in infants, children and adults, indicating that these processes are linked at neural level.

Thesis (MSL and HT (Interdisciplinary Health Sciences. Speech-Language and Hearing Therapy))--Stellenbosch University, 2008. / This study aims to describe the speech processing skills of three children ages 6;0, 6;10 and 8; 10, with cochlear implants. A psycholinguistic framework was used to profile each child’s strengths and weaknesses, using a single case study approach. Each child’s speech processing skills are described based on detailed psycholinguistically-orientated assessments. In addition, retrospective data from 1-2 years post-implantation were examined in the light of the psycholinguistic framework in order to describe each child’s development over time and in relation to time of implantation. Results showed each child to have a unique profile of strengths and weaknesses, and widely varying outcomes in terms of speech processing even though all three children had the same initial difficulty (congenital bilateral hearing loss). Links between speech processing and other aspects of development as well as contextual factors are discussed in relation to outcomes for each child. The case studies contribute to knowledge of speech processing skills in children with cochlear implants, and have clinical implications for those who work with children with cochlear implants and their families.