Prosody plays an important role in speech communication. Many individuals with motor speech disorders have decreased prosodic control and thus lower overall intelligibility. Few studies have examined the effect of a flattened prosodic contour on the intelligibility of dysarthric speech, and little is known about the role that listener gender plays in understanding disordered speech. The purpose of this study was to quantify the impact of artificial prosodic manipulation on the intelligibility of dysarthric speech as a function of the extent of fundamental frequency (F0) contour flattening. A further goal was to examine the influence of listener gender on intelligibility. Speech recordings from two speakers (one with mild dysarthria and one with severe dysarthria) were synthetically altered by reducing F0 variability by 50%, 75%, and 100%. Fifty listeners transcribed the sentences and rated the perceived difficulty of the task. Results of the study indicated that a flattened F0 contour led to decreases in the intelligibility of both speakers with dysarthria, both in terms of transcription accuracy and ratings of listener confidence. All altered conditions resulted in poorer intelligibility than the unaltered utterances. For the mild speaker, scores and ratings decreased predictably in proportion to the extent of F0 flattening, whereas for the severe speaker, there was not a steady decrease in intelligibility as the F0 was progressively flattened. The utterances were more intelligible to female than male listeners.



College and Department

David O. McKay School of Education; Communication Disorders



Date Submitted


Document Type





dysarthria, prosody, synthetic alteration, intelligibility