How do our eyebrows respond to masks and whispering? The case of Persians

Whispering is one of the mechanisms of human communication to convey linguistic information. Due to the lack of vocal fold vibration, whispering acoustically differs from the voiced speech in the absence of fundamental frequency which is one of the main prosodic correlates of intonation. This study addresses the importance of facial cues with respect to acoustic cues of intonation. Specifically, we aim to probe how eyebrow velocity and furrowing change when people whisper and wear face masks, also, when they are supposed to produce a prosodic modulation as it is the case in polar questions with rising intonation. To this end, we run an experiment with 10 Persian speakers. The results show the greater mean speed when speakers whisper indicating a compensation effect for the lack of F0 in whispering. We also found a more pronounced movement of both eyebrows when the speakers wear a mask. Finally, our results reveal greater eyebrow motions in questions suggesting the question is a more marked utterance type than a statement. No significant effect of eyebrow furrowing was found. However, eyebrow movements were positively correlated with the eyebrow widening suggesting a mutual link between these two movement types.