On the nature of apical vowel in Jixi-Hui Chinese: Acoustic and articulatory data

Chinese languages have a set of segments known as apical vowels, which have been analysed in previous studies as either genuine vowels, fricative vowels, fricative consonants, or approximants. This study is concerned with the apical vowel attested in Jixi-Hui Chinese. We examine this segment from acoustic and articulatory perspectives and argue that it is best defined as a fricative /z/. Phonologically, Jixi-Hui Chinese /z/ is a distinct phoneme that is exclusively attested in syllable nucleus position where it constitutes a tone-bearing unit and which can undergo tonal sandhi processes. It can appear not only after coronal sibilants /s ts tsʰ/, but also after bilabials /p pʰ/ and nasals /m n/. Acoustically, we show that this segment contains frication noise in its initial phase in the majority of cases, with a formant structure towards its end. The analysis of the zero-crossing rate confirms this significant presence of noise, clearly distinguishing this segment from genuine vowels. Furthermore, articulatory analyses of ultrasound data show that /z/ has a near-identical tongue shape to fricative /s/ on both mid-sagittal and coronal planes, in both sibilant and non-sibilant contexts. These findings are viewed in light of the variability in the way /z/ is phonetically implemented in Jixi-Hui Chinese.