Voice Outcomes of Clear Speech Cueing in Individuals With Parkinson's Disease

The purpose of this study was to investigate acoustic and auditory-perceptual voice outcomes of clear speech cueing in individuals with Parkinson's disease (PD).

Speakers with PD completed speaking tasks (a spontaneous speech sample and a standard reading passage) in two speaking conditions: typical and clear speech. Acoustic measures of vocal intensity, fundamental frequency (f_o) variation, cepstral peak prominence (CPP), and low-to-high (L/H) ratio were calculated. Expert listeners completed auditory-perceptual ratings of the overall severity of dysphonia, breathiness, and strain of samples using visual-analog scales. Acoustic and auditory-perceptual measures were compared across speaking conditions and tasks.

Intensity significantly increased in the clear speech condition compared with typical speech. When controlling for intensity, f_o variation increased, and L/H ratio decreased in the clear speech condition. Breathiness decreased from typical to clear speech. There were no condition differences in CPP when accounting for intensity and no condition differences in overall severity of dysphonia or strain.

Targeting the articulatory subsystem with clear speech cueing in PD elicits acoustic and auditory-perceptual changes that align with a louder voice, increased intonational variation, and reduced breathiness. Voice changes with clear speech are not fully explained by concomitant increases in intensity.