An ultrasound study of high vowel devoicing in Tokyo Japanese: Evidence for the vowel gesture retention

Abstract

High vowels in Tokyo Japanese are typically devoiced between voiceless obstruents, but controversy remains over whether vowel gestures persist when devoiced or are instead deleted. A previous ultrasound study (Iwasaki et al., 2020) showed that the lingual articulation of the release burst of /kV/ differs by vowel context even when the vowels are devoiced. This study uses tongue surface contours derived from midsagittal ultrasound images to investigate the effects of vowel devoicing on changes in quantified tongue shape over time. Native speakers of Tokyo Japanese produced word pairs (/C1VC2e/) that contrasted in the voicing of V, which was either /i/ or /u/. Tongue shape was characterized by Fourier transforming tangent angles along each contour (Dawson et al., 2016). Time-normalized trajectories over the /C1VC2e/ sequence were compared by vowel context (/i/ versus /u/) and voicing environment (devoiced versus voiced). Preliminary results show that the real component of the first Fourier coefficient is sensitive todetecting evolving shape differences between the two vowel contexts over the sequence, not just when the vowels are voiced, but also when they are devoiced. Based on these results, the high vowel contrast persists even in the devoiced environment, suggesting that devoiced vowels are not deleted.