What R Mandarin Chinese /ɹ/s? - acoustic and articulatory features of Mandarin Chinese rhotics

Rhotic sounds are well known for their considerable phonetic variation within and across languages and their complexity in speech production. Although rhotics in many languages have been examined and documented, the phonetic features of Mandarin rhotics remain unclear, and debates about the prevocalic rhotic (the syllable-onset rhotic) persist. This paper extends the investigation of rhotic sounds by examining the articulatory and acoustic features of Mandarin Chinese rhotics in prevocalic, syllabic (the rhotacized vowel [ɚ]), and postvocalic (r-suffix) positions. Eighteen speakers from Northern China were recorded using ultrasound imaging. Results showed that Mandarin syllabic and postvocalic rhotics can be articulated with various tongue shapes, including tongue-tip-up retroflex and tongue-tip-down bunched shapes. Different tongue shapes have no significant acoustic differences in the first three formants, demonstrating a many-to-one articulation-acoustics relationship. The prevocalic rhotics in our data were found to be articulated only with bunched tongue shapes, and were sometimes produced with frication noise at the start. In general, rhotics in all syllable positions are characterized by a close F2 and F3, though the prevocalic rhotic has a higher F2 and F3 than the syllabic and postvocalic rhotics. The effects of syllable position and vowel context are also discussed.