Acoustic and perceptual cues to contrastive stress in dysarthria.

PURPOSE In this study, the authors sought to understand acoustic and perceptual cues to contrastive stress in speakers with dysarthria (DYS) and healthy controls (HC). METHOD The production experiment examined the ability of 12 DYS (9 male, 3 female; M=39 years of age) and 12 age- and gender-matched HC (9 male, 3 female; M=37.5 years of age) to signal contrastive stress within short sentences. Acoustic changes in fundamental frequency (F0), intensity, and duration were studied. The perceptual experiment explored whether 48 unfamiliar listeners (24 male, 24 female; M=23.4 years of age) could identify the intended stress location in DYS and HC productions. RESULTS Although both speaker groups used all 3 prosodic cues, DYS relied more heavily on duration. Despite reduced F0 and intensity variation within DYS utterances, listeners were highly accurate at identifying both DYS (>93%) and HC (>97%) productions. Acoustic predictors of listener accuracy included heightened prosodic cues on stressed words along with marked decreases in these variables for neighboring nonstressed words. CONCLUSIONS Speakers signaled contrastive stress using relative changes in one or more prosodic cue. Although individual speakers employed different cue combinations, listeners were highly adept at discerning the intended stress location. The communicative potential of prosody in speakers with congenital dysarthria is discussed.