Cross-Linguistic Influence on Nasalance in Vietnamese-English Bilingual Speakers: Why Is Nasalance Higher for the Vowel /a/ Than /i/?

PURPOSE: Previous studies have reported higher nasalance values for the vowel /a/ compared to /i/ in Vietnamese-speaking children and adults. This study aims to determine whether the same pattern is present in Vietnamese-English bilingual speakers and whether their nasalance scores align more closely with those of monolingual Vietnamese or monolingual English speakers.

METHOD: Sixteen Vietnamese-English bilingual adults participated in the study. Nasalance data of 16 monolingual Vietnamese speakers and 16 monolingual English speakers were adopted from the author's previous studies. Nasalance scores were obtained for three prolonged vowels; syllables; and oral, oral-nasal, and nasal passages in both English and Vietnamese.

RESULTS

Vietnamese-English bilingual speakers exhibited higher nasalance scores for the prolonged vowel /a/ compared to /i/. However, no significant differences were observed between the two vowels in the syllable context. For between-group comparisons, the bilingual speakers produced lower nasalance scores for prolonged vowels /a/ and /i/, syllables with /a/ vowel context, and all three Vietnamese passages, compared to Vietnamese monolinguals. However, the bilinguals' scores were similar to those of English monolinguals for all stimuli, except for /a/.

CONCLUSIONS

The nasalance scores of Vietnamese-English bilinguals more closely resembled those of monolingual English speakers, suggesting an influence of the second language on resonance domain. However, the higher nasalance score of /a/ compared to /i/ indicates that bilingual speakers retain native resonance characteristics when other linguistic factors are minimized. These findings contribute to our understanding of cross-linguistic influences on nasalance and provide important insight for clinical assessment in Vietnamese-speaking populations in the United States.