Redundant voicing and register in Mnong Râlâm

Mnong Râlâm is a South Bahnaric language (Austroasiatic) that is traditionally described as preserving a voicing contrast in onset obstruents, contrary to other languages of the Mnong/Phnong continuum. Acoustic results yield evidence that this voicing distinction is less robust than previously suggested and is redundant with a register contrast realized on following vowels through modulations of F1 at vowel onset (and more limited variations of F2 and voice quality). A perception experiment also shows that F1 weighs heavier than closure voicing in identification. The existence of a language in which voicing and register are redundant allows us to revisit previous models of registrogenesis. It suggests that the acoustic properties of register may develop and become distinctive while voicing is still present rather than as a direct consequence of devoicing. The unexpected discovery of register in Mnong Râlâm also challenges previous reconstructions of Proto-South-Bahnaric, in which only voicing is postulated, based on hitherto limited available descriptive materials.