proto-southwestern-tai revised: a new reconstruction - seals 22

Contact Induced Change? 17
To sum up, vowel quality differences between registers are at best limited to the F1
of high vowels (at least in the set of three vowels tested here). Even then, these differences
are so small and unsystematic that they are unlikely to be perceptible. It is therefore
unlikely that vowel quality plays a crucial role in the phonetic realization of the register
contrast.
4. Discussion
In this section, we will sum up the results and compare them to previous descriptions,
discuss the relevance of our data for the hypothesis that Cham register systems are shaped
by contact and put forward a fine-grained model of language contact and sound change.
4.1 The phonetics of Cham register
The first observation that can be made based on our results is that the three dialects under
study are surprisingly similar with respect to the phonetic realization of their registers.
First, f0 seems to be the most important property of register in all three dialects. However,
the f0 difference between registers is greater in Eastern Cham than in Kompong Chhnang
Cham and Châu Đốc Cham, which suggests that Eastern Cham might have phonologized it
without making it contrastive, something that the other dialects have not done yet. In this
sense, one could argue that Eastern Cham is transitional in that it has made a step further
towards the development of tone.
The other phonetic properties measured here, open quotient (voice quality) and the
frequencies of the first two formants (vowel quality), are much less conclusive. Open
quotient differences between the registers could play a role in perception in all three
dialects, but they seem less distinct and reliable than pitch differences. Therefore, open
quotient seems to be an ancillary phonetic property, in the sense that it only reinforces a
contrast that is primarily based on f0. Moreover, the exact implementation of open quotient
differences between registers varies between dialects and speakers. Whereas most Eastern
Cham and Kompong Chhnang Cham speakers maximize the open quotient difference at
the beginning of the vowel and then neutralize it towards its end, most Châu Đốc Cham
speakers exhibit a ballistic effect, where the high and low register open quotient curves
cross paths and change positions at about the first third of the vowel. Finally, the role of
vowel quality seems negligible. Only the first formant of the high vowels /i, u/ show
register differences, and these differences are so small that it is unlikely that they can be
used for register identification. At this point, a perceptual study conducted with the same
stimuli in the three dialects is necessary to further understand the phonetic realization of
Cham register.
Interestingly, our findings partially disagree with previous work. The Eastern Cham
results are in tune with other phonetic studies (Phú et al. 1992; Brunelle 2005b; a), but
Kompong Chhnang Cham and Châu Đốc Cham are different from other Western Cham
dialects. Kompong Chhnang Cham, which is spoken in Cambodia, has a pattern of pitch
and voice quality that matches previous descriptions of Cambodian Cham (Headley 1991;
Edmondson and Gregerson 1993), but it does not seem to make much use of vowel quality
contrasts, contrary to Kompong Thom Cham and the dialect investigated by Edmonson and
Gregerson. More mysterious are our results for Châu Đốc Cham, which differ from those