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Title:The structure of variation in spontaneous American English stops
Author(s):Khasanova, Alina
Director of Research:Cole, Jennifer S.
Doctoral Committee Chair(s):Cole, Jennifer S.
Doctoral Committee Member(s):Fleck, Margaret M.; Hasegawa-Johnson, Mark A.; Hualde, José Ignacio
Department / Program:Linguistics
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):speech production
stop consonants
acoustic cues
Abstract:One of the inherent characteristics of speech is that the same discrete units like phonemes, syllables, or words appear vastly different in the articulatory and acoustic domain. Acoustic variation can be thought of as the consequence of various forces driving speech production, including production effort and the need to maintain perceptual distinctiveness of contrastive elements. Variability is then not just random noise, but on the contrary, is structured. Yet, little is known about the general structure of acoustic variation, with primary focus having been on its sources thus far. This work attempts to fill the gap through an investigation of the general structure in the acoustic variation of stops, to see how variation is related to a stop's phonological features. The primary focus of this thesis is on the relationship between acoustic cues to a stop's contrastive phonological features, and whether that relationship is maintained or changes under variation. Two patterns of cue co-variation are considered here: uniform co-variation, i.e. where both cues either get weaker or stronger, or compensatory cue co-variation, where one cue weakens as the other strengthens. The patterns of cue co-variation reflect distinct properties of speech, such as the continuity of articulation, on one hand, and the limited capacity for sequential independence between gestures that make up the stop. Within this framework, two major questions are investigated. The first questoin is whether two acoustic cues related through patterns of uniform or compensatory co-variation. Specific hypotheses tested are (a) that uniform co-variation of cues is more prevalent than compensatory variation due to additional effort most likely required for the latter; (b) that compensatory variation is likely to occur when necessitated by communicative goals; and (c) that the burst portion of the stop is more likely to host compensatory co-variation than the closure, because of different degrees of freedom available to the speaker. The second question is how phonological features of contrast are preserved under variation, as expressed in the parameters of the cues relationship. To answer these questions, linear regression models were fitted to the measurements of acoustic duration and amplitude of the closure and burst intervals for the canonical realizations of stop consonants drawn from the Buckeye speech corpus. The slopes of regression lines were evaluated by simple slope analyses in order to assess their sign and magnitude: the sign carries information whether the relationship of cues is uniform or compensatory, while the magnitude reflects the differences in the categorical affiliation of the stop (place of articulation, voicing, and position in the word). Results indicate that phonological contrast is often preserved under variation in either the direction or, more commonly, the magnitude of the slopes of the regression lines relating a pair of cues. The majority of cue pairs are in uniform co-variation. Compensation is observed in subsets of the data for some of the cue pairs, most clearly in voiced stops and involving burst cues, i.e. when most needed perceptually or most easily achieved articulatorily. The implications of these findings are discussed with respect to current theories of speech production and, more generally, the search for invariance in speech.
Issue Date:2013-08-22
Rights Information:Copyright 2013 Alina S. Khasanova
Date Available in IDEALS:2013-08-22
Date Deposited:2013-08

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