On the two rhotic schwas in Southwestern Mandarin: when homophony meets morphology in articulation.

This is an acoustic and articulatory study of the two rhotic schwas in Southwestern Mandarin (SWM), i.e., the er-suffix (a functional morpheme) and the rhotic schwa phoneme. Electromagnetic Articulography (EMA) and ultrasound results from 10 speakers show that the two rhotic schwas were both produced exclusively with the bunching of the tongue body. No retroflex versions of the two rhotic schwas were found, nor was retraction of the tongue root into the pharynx observed. On the other hand, the er-suffix and the rhotic schwa, though homophonous, significantly differ in certain types of acoustic and articulatory measurements. In particular, more pronounced lip protrusion is involved in the production of the rhotic schwa phoneme than in the er-suffix. It is equally remarkable that contrast preservation is not an issue because the two rhotic schwas are in complementary distribution. Taken together, the present results suggest that while morphologically-induced phonetic variation can be observed in articulation, gestural economy may act to constrain articulatory variability, resulting in the absence of retroflex tongue variants in the two rhotic schwas, the only two remaining r-colored sounds in SWM.

Vowel coarticulation: Landmark statistics measure vowel aggression.

Regression analysis and mutual information have been used to measure the degree of dependence between a consonant and a vowel, and this has been used to identify the invariance of consonant place and to quantify the coarticulatory resistance of consonants [e.g., Fowler (1994). Percept. Psychophys. 55, 597-610]. This paper presents the first application of this approach to measure coarticulatory properties of vowels, using regression analysis and mutual information on articulatory data of CV syllables produced by seven Taiwan Mandarin speakers. The results show that vowel /i/ shares the most information with the preceding consonant among vowels for the tongue body, whereas vowels /a/ and /u/ are not significantly different from each other in that respect. For the lip articulator, the degree of information sharing for vowels is in the progression: /u/ > /i/ > /a/. Based on the CV model theory of gestural coordination (C-V in-phase relation) and the present results, this study proposes that landmark statistics for vowels reflect the degree of vowel aggression and that V-to-C effect is dominant over C-to-V effect in C-V coarticulation.

Super-imposing maxillary and palatal locations for electroarticulometry: A SIMPLE method.

This study proposes a method of superimposing a physical palatal profile, extracted from a speaker's maxillary impression, onto real-time mid-sagittal articulatory data. A palatal/dental profile is first obtained by three-dimensional-scanning the maxillary impression of the speaker. Then a high resolution mid-sagittal palatal line, extracted from the profile, is sub-divided into articulatory zones and superimposed, by Iterative Closest Point algorithm, onto reconstructed palatal traces in electromagnetic articulometric (EMA) data. Evaluations were carried out by comparing consonant targets elicited by EMA with the proposed method and by static palatography. The proposed method yields accurate results, as supported by palatography.