The effects of high -frequency emphasis and amplitude compression on the short-term intensity range of speech.
Item
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Title
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The effects of high -frequency emphasis and amplitude compression on the short-term intensity range of speech.
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Identifier
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AAI9969714
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identifier
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9969714
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Creator
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Oruganti, Balaji.
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Contributor
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Adviser: Arthur Boothroyd
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Date
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2000
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Language
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English
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Publisher
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City University of New York.
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Subject
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Health Sciences, Audiology | Engineering, Electronics and Electrical
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Abstract
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This study evaluated the effectiveness of simple high-frequency emphasis, and single-band and 2-band fast-release wide dynamic range amplitude compression in reducing the short-term dynamic range of speech. In subjects with severe and profound sensori-neural hearing loss, the dynamic range of hearing is often less than the short-term dynamic range of speech. To a certain extent the dynamic range of speech could be reduced by emphasizing the high-frequencies. But to go beyond this requires syllabic compression. The results of past research on syllabic compression have been equivocal. Conflicting results have been attributed to inappropriate selection of compression parameters, deleterious spectral and temporal changes accompanying compression, and evaluation methods.;The present study focused on the evaluation methods used to assess the effectiveness of compression. In the present study, the effectiveness of amplitude compression and high-frequency emphasis, and their benefits were measured both acoustically and perceptually. Single-band and 2-band syllabic compression and high-frequency emphasis of CVC words were effected through off-line digital processing. The acoustic evaluation included the measurement RMS cumulative amplitude distributions and dynamic input/output functions of the test stimuli. Perceptual measurement consisted of Performance-Intensity (PI) functions which were obtained for normally hearing pink-noise-masked individuals. The effects of signal processing on acoustic amplitude distribution, input/output function, and slope and width of the perceptual PI functions were evaluated. Results showed that, acoustically, the target compression ratio was achieved provided the spectral and temporal characteristics of the acoustical analysis matched those of the processing algorithms. Otherwise, the actual amount of compression was less than that target. Perceptually, a simple high-frequency emphasis, while did not result in a decrease of the overall dynamic range of speech, resulted in enhanced perception for low and moderate sensation levels. Addition of single-band compression with a compression ratio of 3:1 resulted in a reduction of the overall dynamic range of the high-frequency emphasized words by a factor of about 1.5:1. A 2-band compression with a compression ratio of 3:1 in both bands was found to be only marginally superior over single-band compression. The outcome of this research project has potential for improving assessment techniques of compression hearing aids.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
