Peggy
Mok
PhD
thesis: Influences on
vowel-to-vowel coarticulation
Department of Linguistics, University of Cambridge, 2007.
This thesis
investigates two quasi-independent
types of influences on V-to-V
coarticulation: those
stemming from the phonological structure of the language and
those stemming more from phonetic or physical considerations.
It has been proposed
that the
vowel inventory of a language determines degree of V-to-V
coarticulation, but
results of an experiment on Cantonese and Beijing Mandarin disconfirm
this
hypothesis. I instead propose that language-specific realisations of
syllable structure can affect degrees of V-to-V coarticulation.
Results of an experiment on Cantonese, Thai and English support the
hypothesis
that languages with simple syllable structure allow less V-to-V
coarticulation than languages with complex syllable structure.
Four influences related to phonetic
considerations are
examined: 1) linguistic stress (in Cantonese and Mandarin), 2) duration
(speaking rate in Cantonese and Mandarin, vowel length in Thai), 3)
vowel
qualities (in Thai) and 4) syllabification (in Cantonese, Thai and
English).
Studies based on languages with lexical stress show that stress can
affect
coarticulation, but its effect on tone languages without lexical stress
is
unclear. Results show that contrastive stress has a small effect on
coarticulation in Cantonese and Mandarin. Based on the idea of target
undershoot, a shorter duration caused by rate or length difference can
induce
more coarticulation, but little research has been done to explore its
effects
on V-to-V coarticulation. Results show that a shorter duration does not
induce
more coarticulation in Cantonese, Mandarin and Thai. Many studies show
that the
vowel /a/ allows more V-to-V coarticulation than /i/ and /u/
cross-linguistically,
but the principles behind this pattern and the susceptibility of other
vowel
qualities to coarticulation are still unknown. I propose that the jaw
position is responsible for vowel quality differences in V-to-V
coarticulation. Finally, many
studies show that onset consonants are stronger acoustically, more
stable
articulatorily, more prominent perceptually and more frequent
typologically
than coda. This suggests that syllabification can affect
coarticulation: onsets
should be more resistant to V-to-V coarticulation than codas. My data
on Thai (singleton) and English (clusters) show that coda is indeed
more transparent to V-to-V coarticulation than onset.
The thesis also discusses some important methodological issues in
measuring V-to-V coarticulation.
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