The effects of spectrally shaped noise masking on cortical auditory event-related potentials to speech sounds.
Item
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Title
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The effects of spectrally shaped noise masking on cortical auditory event-related potentials to speech sounds.
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Identifier
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AAI9732946
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identifier
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9732946
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Creator
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Martin, Brett A.
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Contributor
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Adviser: David R. Stapells
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Date
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1997
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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
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Abstract
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This dissertation examines the effects of decreased audibility produced by spectrally shaped noise masking on cortical auditory event-related potentials (ERPs) to speech sounds /ba/ and /da/. High-pass noise masking studies examined the effects of decreased audibility for high-frequency spectral regions. Results indicated that as the high-pass noise masker cutoff was lowered from 2000 to 1000 Hz, cortical ERPs MMN, N2, P3, and behavioral measures (d{dollar}\sp\prime{dollar}, RT) all showed significant changes. Amplitudes decreased and latencies increased. N1 showed a different pattern of results as a function of high-pass noise masking, with amplitudes decreasing and latencies increasing gradually as the masker cutoff was lowered. Low-pass noise masking studies examined the effects of decreased audibility for low-frequency spectral regions. Results indicated that as the low-pass noise masker was raised to from 500 to 1000-2000 Hz, ERPs MMN, N2, P3 and behavioral measures all changed significantly. N1 again showed different results, particularly for speech sounds presented at 80 dB SPL. Crossover point analyses examining the contributions of selected frequency regions to behavioral and electrophysiological responses to the speech sounds also showed a different pattern of results for N1 compared to the other measures. Based on results of the studies, N1 appears to be related to the presence of audible stimulus energy, being present when speech sounds were audible, whether or not they were discriminable. MMN, N2 and P3 appear to be related to speech sound discrimination, being present only when behavioral results indicated audible speech sounds were discriminable. The speech sounds were discriminable only when there was spectral energy in the region of the second formant transition for /ba/ and /da/.
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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.
