Vocal characteristics across English-Northern Sotho bilingual individuals : a comparative study

Abstract

Introduction: Bilinguals constitute a significant portion of speech-language therapists’ (SLTs) caseloads. Insight into the cross-linguistic effect on voice is needed to guide SLTs to make linguistically-appropriate observations when working with heterogenous populations.

Method: A comparative within-subject design explored vocal characteristics across 114 audio recordings. Nineteen female English-Northern Sotho bilingual individuals performed three speech tasks (reading, picture description and monologue) in each language. Acoustic analysis of mean fundamental frequency (f0), intensity, and rate was conducted with Praat software. A blinded listeners’ panel reached consensus during perceptual analysis.

Results: Across languages, mean f0 and intensity were significantly greater during the Northern Sotho picture description (p = 0.002) and reading passage (p = 0.033) respectively. The English reading passage elicited a significantly quicker speech rate (p = 0.002). Within English, reading elicited a significantly quicker speech rate than the picture description (p = 0.003) and monologue (p = 0.003). Within Northern Sotho, reading elicited a significantly higher mean f0 than the monologue (p = 0.028). Perceptual voice quality, glottal attack, and resonance were comparable across languages.

Discussion/Conclusion: Language, task performance, and vocal characteristics are not mutually exclusive in bilinguals. SLTs must consider the interaction between language, speech task, and voice when working with bilingual voice clients.