the likelihood of devoicing near certain fricatives may be due to language specific
differences in the relative width (and perhaps timing) of glottal abduction gestures of
100
different fricatives: fricative(s) with greater glottal openings in a given language are
more likely to trigger devoicing in that language.
Interestingly, in Korean, the asymmetry between stops and fricatives depends on
whether the stop or fricative appears on the right or left side of the potential target of
vowel devoicing (Jun and Beckman 1994, Jun et al. 1997, 1998). Fricatives and
aspirated stops are more likely to trigger devoicing than fortis and lenis stops when
they precede a vowel, an expected pattern given the greater glottal apertures of
fricatives and aspirated stops. However, following a vowel, all stops, including fortis
and lenis stops trigger devoicing more often than fricatives, even though fricatives
have greater glottal openings than fortis and lenis stops. Jun and Beckman suggest
that the closing gesture into a stop might be faster than the oral constriction gesture
made for a fricative; this greater velocity of the oral closing gesture could lead to a
more abrupt increase in oral pressure which could inhibit voicing in the preceding
vowel. One might hypothesize that the asymmetry between Korean and those
languages in which devoicing is triggered by a following fricative and not a
following stop (Comanche, Goajiro, and Southern Paiute--singletons) is due to
language specific differences in the relative magnitude and timing of glottal opening
gestures in the two classes of consonants.
In summary, although the glottal overlap story does not account for all cases of
devoicing
20
, it nevertheless offer a coherent explanation for many of the devoicing
asymmetries. There are two robust asymmetries, however,
which do not fall out
directly from a gestural overlap account without recourse to other factors. First,
there is the tendency for low-toned vowels to preferentially devoice over high-toned
vowels pointed out in section 3.5. The existence of this asymmetry is presumably
linked to the inherent inability of voiceless segments to carry tone phonetically.
Thus, devoicing both high and low toned vowels would lead to neutralization of a
tonal contrast, either a lexical contrast in the case of languages with lexical tone, or a
semantic contrast, in the case of sentence (or phrase-level) intonation, e.g. questions
vs. statements. In order to maintain the contrast, a language could thus devoice
either high toned or low toned vowels but not both. Perhaps low toned vowels
devoice, because the articulatory gestures involved in producing low tone are more
compatible with the glottal abduction gestures associated with devoicing. An
explanation for the tone asymmetry must await instrumental research.
The next asymmetry left unexplained by the gestural account of devoicing is the
fact that devoicing of final vowels is so prevalent, in fact, even more prevalent than
the devoicing of word-medial vowels in the vicinity of voiceless consonants.
Furthermore, devoicing in final position typically takes place even when the
preceding consonant is not voiceless. Strikingly, as pointed out in section 3.3., final
devoicing itself respects an implicational hierarchy. The occurrence of devoicing in
final position of a given domain implies devoicing in final position of smaller
domains. Thus, utterance final devoicing in a languages implies phrase final
devoicing which implies word-final devoicing. This implicational hierarchy of
devoicing can be explained in terms of the decline in subglottal pressure throughout
the course of an utterance (Dauer 1980); this drop in subglottal pressure results in a
decrease in the volume-velocity of air flow through the glottis which in turns inhibits
devoicing. Subglottal pressure is lesser in final position of larger domains than in
final position of smaller domains; hence, the likelihood of devoicing increases the
larger the domain. Because subglottal pressure is lowest utterance finally, vowel
devoicing is most common in this environment; cross-linguistic devoicing patterns
reflect this fact. Those vowels whose glottal adduction gestures are inherently
hypoarticulated either in terms of magnitude or duration, e.g. short vowels, high
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