The effects of flattening fundamental frequency contours on sentence intelligibility in speakers with dysarthria

This study explored the relationship between F0 variability and intelligibi lity in persons with motor speech disorders. The literature suggests that m onopitch may have detrimental effects on the intelligibility of individuals with dysarthria (and other speech disorders), but few studies have examine d the independent effect of a Rat F0 contour on intelligibility in speakers with articulatory difficulties. An LPC resynthesis technique was used to r educe the speakers' sentence F0 range by 25%, 50% and 100% (flattened F0). Two dysarthric speaker groups were evaluated, one with prosodic inadequacy and imprecise articulation( hypokinetic) and one with imprecise articulatio n only (UUMN). Speech intelligibility was assessed using a word transcripti on task and an interval-scaling task. Results argue strongly for the percep tual importance of sentence-level F0 variations on speech intelligibility e ven when the F0 range is severely restricted. Results also suggest that the contribution of F0 to intelligibility may vary with type of dysarthria.