Dynamic evidence for the vowel gesture retention of devoiced high vowels in Tokyo Japanese

Abstract

High vowels in Tokyo Japanese are typically devoiced between voiceless obstruents. Controversy remains over whether vowel gestures in devoiced vowels persist or are deleted. A previous ultrasound study (Iwasaki et al., 2020) showed that the lingual articulation of the /kV/ release differed by vowel context even when devoiced. This study looked at changes in the midsagittal tongue surface over time by quantifying the shape and location of the tongue within the vocal tract. Native speakers of Tokyo Japanese produced items (/kVC2e/) that contrasted in the voicing of V, which was either /i/ or /u/. Tongue contours were quantified by Discrete Fourier Transform (DFT), using the approach of Liljencrants (1971). Time series of phase and magnitude of the first Fourier coefficient were compared by vowel context (/i/ vs. /u) and vowel voicing (devoiced vs. voiced). These showed the presence of the vowel contrast whether vowels were devoiced or voiced, suggesting that some devoiced vowels retain lingual gestures. For /u/ only, we found a voicing-induced difference, consistent with reduction or deletion of this vowel gesture. DFT can be a useful tool to analyze tongue contours, supporting the analysis of tongue shape evolving over time.