Vowel space warped in speaking through facial masks

Wearing facial masks has proved an effective measure of self-protection amid global pandemics. Masks, however, degrades speech signals. This study investigated whether and how facial masks affected speaking by examining changes in vowel properties. Formants of three Cantonese vowels (/aa/, /i/ and /u/) produced by adult native speakers of Hong Kong Cantonese were measured in conditions with and without a mask. Results showed that wearing surgical, KF94 masks and face shields led to different degrees of warping of vowel space compared with the area measure in no mask condition. Moreover, speaking through face shields yielded significantly smaller spaces than those in the other two masks. Previous studies on English reported larger vowel space areas under masks. The warped spaces of vowels under masks may be a result of higher speaking rate and lower intensity when speaking through masks. Differences in ours and previous studies also prompt further investigation to language-specific spectral properties of vowels.