Northern Raglai voicing and its relation to Southern Raglai register: evidence for early stages of registrogenesis.

Northern and Southern Raglai are two closely related Austronesian dialects (Chamic branch) spoken in south-central Vietnam. Although they are mutually intelligible, Northern Raglai is described as having a voicing contrast in onset stops, while Southern Raglai is assumed to have replaced the Chamic voicing contrast with a register contrast realized on the whole syllable (but primarily on its vowel). A production study of the two dialects confirms that Northern Raglai preserves a voicing contrast, even if most women exhibit partial devoicing of their voiced stops, and that Southern Raglai has developed a register contrast based on F1 and phonation cues at the beginning of vowels. The weights of the acoustic properties of voicing and register are similar across ages and genders, suggesting that the two laryngeal contrasts are phonetically stable. Even if there is little evidence of change in progress, a close inspection of the Northern Raglai voicing contrast reveals voicing-conditioned modulations of F1 and perturbations of phonation after partially devoiced stops that could be precursors of a register system similar to that of Southern Raglai. We argue that this is a pathway to registrogenesis and speculate about the articulatory laryngeal mechanisms that could trigger registrogenetic changes. Our data also show that the Northern Raglai voicing contrast is unstable in aspirated stops and that voiced aspirated stops typically have a partially voiceless and partially voiced aspiration.