Acoustic markers of vowels produced with different types of face masks

The wide spread of SARS-CoV-2 led to the extensive use of face masks in public places. Although masks offer significant protection from infectious droplets, they also impact verbal communication by altering speech signal. The present study examines how two types of face masks affect the speech properties of vowels. Twenty speakers were recorded producing their native vowels in a /pVs/ context, maintaining a normal speaking rate. Speakers were asked to produce the vowels in three conditions: (a) with a surgical mask, (b) with a cotton mask, and (c) without a mask. The speakers' output was analyzed through Praat speech acoustics software. We fitted three linear mixed-effects models to investigate the mask-wearing effects on the first formant (F1), second formant (F2), and duration of vowels. The results demonstrated that F1 and duration of vowels remained intact in the masked conditions compared to the unmasked condition, while F2 was altered for three out of five vowels (/e a u/) in the surgical mask and two out of five vowels (/e a/) in the cotton mask. So, both types of masks altered to some extent speech signal and they mostly affected the same vowel qualities. It is concluded that some acoustic properties are more sensitive than other to speech signal modification when speech is filtered through masks, while various sounds are affected in a different way. The findings may have significant implications for second/foreign language instructors who teach pronunciation and for speech therapists who teach sounds to individuals with language disorders.