Being a round /y/: An acoustic description of high front vowels in Singapore Mandarin elicited by speakers with different bilingual balance in Mandarin and English

In acoustic phonetics, there is limited research about individual differences among bilinguals with different language balances. Using a picture description task, we recorded 942 vowel tokens of high front vowels from Singaporean adult bilinguals of Mandrin Chinese and English (N=50, 25 female). F1, F2 and F3 frequencies were tracked for /y/ (phonemic in Mandarin Chinese) and /i/ (phonemic in English and Mandarin). Generalized additive mixed models were used to characterise formant trajectories of /y/ and /i/ over the timecourse of articulation, with smooth terms of vowel, gender, tone and phonemic context. F1 was similar throughout articulation for both vowels. Formant trajectories differed across the whole timecourse for F2, and in the final stage for F3. Furthermore, we observed that speakers’ bilingual balance influenced the degree of difference between /y/ and /i/ for a given speaker, with larger differences in F3 (the psychoacoustic correlate of lip rounding) for those with more Mandarin in their bilingual balance. These findings demonstrate that three-dimensional formant trajectories are a valuable way to investigate nuanced acoustic profiles, and that language histories can be considered a powerful addition to our understanding of individual differences within a multilingual community.