Variation and change in the production of te reo Māori closing vowel sequences

This study examines the vowel sequences /ai ae ao au ei oi ou/ in te reo Māori, the indigenous language of Aotearoa New Zealand. Descriptions state that these closing sequences are comprised of separate phonemes, which are realised as surface diphthongs within morphemes, but as hiatuses when they straddle a morpheme boundary. We examine whether this description is borne out through acoustic analysis of data from the MAONZE corpus, which contains recordings from three generations of Māori speakers. Using the approach developed in Culhane et al. (In press. Variation in the production of te reo Māori opening vowel sequences. Laboratory Phonology), we find that for all sequences, there is systematic covariation between duration, intensity, and formant trajectories, which form a spectrum from hiatus-like to diphthong-like realisations. There is some evidence for the morpheme boundary effect described, but also for effects of stress and word position. We find that production of closing sequences has changed over time, with increasingly diphthong-like productions. Our analysis reveals that these patterns of change are likely systematic, whereby the change towards more diphthongised sequences reflects a change in the phonetics-phonology system more broadly.