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An acoustic study of Iu-Mien tones with a special focus on the role of laryngealization

The interaction of fundamental frequency (f0) and phonation types has been analyzed both in tonal languages in which phonation varies with tone (e.g., Jingpho (Maddieson & Ladefoged 1985), Green Mong (Andruski & Ratliff 2000), Jalapa Mazatec (Garellek & Keating 2011), White Hmong (Esposito 2012)) and in tonal languages in which phonation is not contrastive. Patterns in the distribution of a non-contrastive phonation over tones have also been studied, for example in Mandarin (Keating & Esposito 2007; Yu 2010) and Cantonese (Yu 2010). Previously unnoticed, however, is a phenomenon in which the same phonation type differentiates between two tones exclusively on the basis of differences not in its presence but in its distribution over the duration of the vowel. Here we explore an apparent case of this, investigating how f0 and laryngealization interact in Iu-Mien low tones and how this interaction is manifested across the vowel. The results show that low tones correlate with non-modal phonation. What is more, the study also shows that the distribution of laryngealization across the vowel length separates the low rise tone from the low rise-fall tone despite their pitch contours having been run together. This finding points to the development of contrastive phonation in Iu-Mien.