Transphonologization of onset voicing: revisiting Northern and Eastern Kmhmu'

Phonation and vowel quality are often thought to play a vital role at the initial stage of tonogenesis. This paper investigates the production of voicing and tones in a tonal Northern Kmhmu' dialect spoken in Nan Province, Thailand, and a non-tonal Eastern Kmhmu' dialect spoken in Vientiane, Laos, from both acoustic and electroglottographic perspectives. Large and consistent VOT differences between voiced and voiceless stops are preserved in Eastern Kmhmu', but are not found in Northern Kmhmu', consistent with previous reports. With respect to pitch, f0 is clearly a secondary property of the voicing contrast in Eastern Kmhmu', but unquestionably the primary contrastive property in Northern Kmhmu'. Crucially, no evidence is found to suggest that either phonation type or formant differences act as significant cues to voicing in Eastern Kmhmu' or tones in Northern Kmhmu'. These results suggests that voicing contrasts can also be transphonologized directly into f0-based contrasts, skipping a registral stage based primarily on phonation and/or vowel quality.