UBC Theses and Dissertations
Coarticulation and lipreading Pichora-Fuller, Margaret Kathleen
This study investigates the relationship of articulatory variation to the visual perception of phonemes. Normal hearing and hearing-impaired subjects who had demonstrated good lipreading skills on a pilot test were selected to lipread videotaped tests under visual only conditions. Eighty-one V₁CV₂ utterances where V could be /I,æ,u/ and C could be /p,t,k, tϚ, f, Θ, s,Ϛ, w/ were spoken by a speaker who had been selected in a pilot study as being easy to lipread. The 81 stimuli were used to construct three test tapes, one where the speaker spoke slowly, one where she spoke faster, and one in which the fast tape was reversed. Coarticulatory influences were expected to be present in these stimuli. Lipreading scores and measurements of the articulations were compared in an effort to explain some of the variability in the visual perception of phonemes which was suggested by existing literature. Lipreading performance was nearly perfect for /p,f,w, Θ,u/ on all tapes in all disyllables. Lipreading performance on /t,k,tϚ,Ϛ,s,i,æ/ varied depending on phonological context, especially on the fast test tape. Variation in the identification of the less visually dominant phonemes could be directly related to coarticulatory effects revealed in the measurement of articulatory parameters (vertical and horizontal lip opening) of the visual signal. Improvement in lipreading ability throughout the task was evidenced by normal hearing subjects. The features labial, rounded, and alveolar or palatal place of articulation transmitted more information to lipreaders than did the feature continuant. It was concluded that variability in articulatory parameters resulting from coarticulatory effects in faster speech increases lipreading difficulty, especially initially. Lipreaders are sensitive to subphonemic and subvisemic variations.
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