Conference Papers Year : 2025

Locus Equations as a Method for Investigating Anticipatory Coarticulation Investigating Uvularized Vowel Contrasts in Mawo Qiang

Abstract

This study evaluates the measurement of anticipatory coarticulation through the use of locus equations. Focusing on Mawo, a dialect of Northern Qiang spoken in Heishui County, Sichuan Province, China, this study investigates how variation in coarticulatory strength— captured by differences in the slope of F2 transitions—can signal the presence of a contrast between plain and uvularized vowels (Evans et al. 2016). Coarticulation captures how adjacent segments influence each other, and in the case of uvularization, these effects often manifest in both anticipatory and carryover patterns in formant transitions—most notably in the lowering of F2 and the raising of F1 and F3-F2 (Evans et al., 2016). The locus equation method, as described by Embarki et al. (2006) relates the onset of the second formant frequency (F2 onset) to its steady-state (F2 midpoint), with the slope of the regression lines providing a numerical index of vowel-induced coarticulation. This aligns with earlier work by Sussman et al. (1999), who used locus equations to reveal how coarticulatory strength varies across consonantal places of articulation. Locus equations, which track the linear relationship between F2 onset and F2 midpoint, are particularly sensitive to changes in coarticulatory dynamics—steeper slopes indicating more vowel influence on consonant articulation. This paper’s analysis employs linear regression models to determine the strength of anticipatory coarticulation, evaluating regression slopes (β) as indices of coarticulatory magnitude. The speech corpus consists of recordings from nine native speakers (4 male, 5 female; mean age = 64 years, range = 58–68 years) of Mawo, drawn from a corpus collected as part of the ANR PhoTon project (https://anrphoton.cnrs.fr/). All participants contributed minimal pairs contrasting plain and uvularized syllables, enabling a controlled investigation of coarticulatory effects. Examples include /ti/ ‘black bear’ vs. /tiʁ/ ‘pair (classifier)’, /də/ ‘beans’ vs. /dəʁ/ ‘poison’. Each pair exemplifies the contrastive nature of uvularization in the vowel system. F2 onset and midpoint values were extracted from each token and used to compute locus equations. Results reveal that uvularized contexts consistently exhibit significantly higher anticipatory coarticulatory slopes across multiple phonetic environments, demonstrating that locus equation analysis is an effective method for identifying uvularization as a contrastive phonetic feature. This pattern is evident across both vowel and consonant analysis contexts, suggesting a widespread articulatory influence of uvularization (Table 1). Among vowels, the mid-central vowel /ə/ showed the most pronounced effect for female speakers, with a steep increase in slope from β = 0.268 in plain contexts to β = 0.927 in uvularized contexts (p < .001). This supports findings from Evans et al. (2016), which describe a rearward tongue gesture for uvularized vowels. The high back vowel /u/ exhibited significant coarticulatory enhancement under uvularization for female speakers (β = 0.025 plain vs. β = 0.633 uvularized, p < .001). Coarticulatory effects were also robust in consonantal environments. The lateral /l/ showed significantly increased slopes in uvularized contexts for both male (β = 0.739 vs. 0.473, p <.001) and female speakers (β = 0.724 vs. 0.334, p < .001), paralleling ultrasound imaging results in Evans et al. (2016), which demonstrated uvularization effects manifesting during lateral articulation. These findings confirm that uvularization can influence consonantal articulation in ways detectable through acoustic slope measures. The nasal /n/ showed a particularly striking contrast among male speakers, where coarticulatory strength more than doubled in uvularized contexts (β = 1.106 vs. 0.542, p < .001), reinforcing the conclusion that uvularization operates as a pervasive articulatory feature that modifies both vocalic and lingual consonantal segments. This research represents the first systematic application of locus equation analysis to a corpus of uvularized vowels in a Tibeto-Burman language and offers new evidence that anticipatory coarticulation can serve as an effective phonetic cue for uvularization.

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hal-05421738 , version 1 (17-12-2025)

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  • HAL Id : hal-05421738 , version 1

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Louise Mc Keever, Katia Chirkova, Claire Pillot-Loiseau, Angélique Amelot, Amélie Elmerich, et al.. Locus Equations as a Method for Investigating Anticipatory Coarticulation Investigating Uvularized Vowel Contrasts in Mawo Qiang. Phonetic Approaches to Under-Documented Languages (With a Special Emphasis on Tibeto-Burman Languages), Sep 2025, Aubervilliers, France. ⟨hal-05421738⟩
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