The Acoustic Properties of Vowels in Foreigner-Directed Speech: Insights from Speech Directed at Foreign Domestic Helpers

This study examines the acoustic properties of vowels in foreigner-directed speech (FDS) in interactions between female Omani-Arabic-speaking employers and their foreign domestic helpers (FDHs). Particularly, it investigates whether Arabic corner vowels /i:/, /a:/, and /u:/ undergo acoustic adaptations in FDS. The study also explores the influence of foreign interlocutors’ psycholinguistic characteristics, such as degree of foreign accent, religion, and length of residence (LoR), on the extent of these adaptations. Data were collected from 22 Omani-Arabic-speaking women interacting with their 22 FDHs and with a native speaker (NS) confederate using a spot-the-difference task. Acoustic measures including vowel space area, formant frequency measures (F1 and F2), fundamental frequency (f0), intensity, and duration were compared across speech directed at FDHs and the NS. The results revealed that FDS exhibited greater vowel space expansion, higher F1, and increased pitch (f0) and intensity compared to speech directed at the NS confederate. However, FDS did not significantly affect F2 values. Unexpectedly, vowel duration in FDS was shorter than in speech directed at the NS. Furthermore, the psycholinguistic factors of foreign interlocutors had no significant effect on vowel space expansion in FDS. These findings provide evidence that FDS is characterized by heightened prosodic and acoustic features, potentially contributing to clearer speech. Additionally, the study highlights that NSs employ FDS when interacting with foreigners perceived to have a foreign accent.