Effect of Face Masks and Speech Style on Speech Intelligibility and Listener Effort in Parkinson's Disease.

The aim of this study was to quantify the combined effects of face masks and effortful speech styles on listener intelligibility and perceived listener effort in talkers with and without Parkinson's disease (PD). Ten people with PD and 10 healthy, older controls read aloud sentences in two face mask and three speech style conditions. Masks included no mask and KN95 masks. Speech styles included habitual, clear, and loud. Listener participants were tasked with listening to each sentence mixed with background noise and then transcribing what they heard and rating how effortful it was to understand. Listener accuracy and effort were each modeled as a function of speaker group, face mask, and speech style using mixed-effects regression models. Listeners were less accurate and reported greater listening effort for the PD group and for the mask condition. Listeners were more accurate and reported less effort when listening to clear and loud compared to habitual speech. Listener accuracy and listener effort were strongly negatively correlated across all conditions. Face masks were also associated with a steeper decline in speech intelligibility and an increase in listener effort for talkers with PD. Face masks resulted in steeper speech intelligibility decline for talkers with PD compared to controls. Speaking more loudly or more clearly when wearing a face mask improved intelligibility for talkers with PD compared to habitual speech, and both speech styles resulted in speech intelligibility levels that approximated talkers' baseline intelligibility levels without a mask.