Lip muscle activity related to speech rate and loudness.

Changes in suprasegmental speech parameters may require adjustments in oral motor control that are reflected in the activity of perioral musculature. In order to evaluate possible patterns of difference, perioral surface electromyographic (EMG) signals were obtained from 20 adults who read a paragraph aloud at habitual rate and at self-judged proportionately slower and faster rates, at habitual loudness and at proportionately softer and louder levels, and in a "precise" manner. EMG amplitude analysis showed significant task effects, with higher average amplitudes for fast, loud, and precise speech and lower average amplitudes for slow and soft speech. These results are compatible with a model of multidimensional reorganization of speech motor control for suprasegmental changes applied to connected speech.

Speech and pause characteristics following speech rate reduction in hypokinetic dysarthria.

The effect of speech rate reduction on speech and pause characteristics during a reading task was examined for speakers with Parkinson's disease (PD) and a group of control speakers. Duration of utterances and characteristics of pausing (duration, interpause phrase length, and location) were determined. At habitual reading rate, subjects with PD had shorter speech duration and greater time per pause than control subjects. At reduced reading rates, subjects with PD increased speech duration so that it was equivalent to the control speakers at habitual rate. Both groups had the majority of their pause occurring at appropriate syntactic boundaries. Subjects with PD had a greater proportion of pauses occurring at syntactically inappropriate locations than did the controls. When speech rates were reduced, both groups showed a decrease in pauses located at appropriate syntactic boundaries. The implication of these findings on speech intelligibility is discussed.

Effects of temporal alterations on speech intelligibility in parkinsonian dysarthria.

The effect of two types of temporal alterations, paced and synthetic, on the intelligibility of parkinsonian dysarthric speech was investigated. Six speakers with idiopathic Parkinson's disease served as subjects. Paced temporal alterations were created by slowing each speaker to 60% of his/her habitual speaking rate. The synthetic alterations were created by modifying the habitual rate speech samples using digital signal processing. Three types of synthetic alterations were examined: Pause Altered, Speech Duration Altered, and Pause and Speech Duration Altered. The 60% of habitual speaking rate condition was more intelligible than the synthetic conditions. In addition, none of the synthetic alterations were found to be more intelligible than samples produced at habitual speaking rates. The results suggest that simple alterations of speech signals do not explain the differences in intelligibility that have been observed when parkinsonian dysarthric speakers reduce speaking rates. Reasons for the failure of synthetic alterations to increase speech intelligibility scores are discussed.

The effect of rate control on the intelligibility and naturalness of dysarthric speech.

Speaking rates of individuals with severe ataxic dysarthria (n = 4) and severe hypokinetic dysarthria (n = 4) were reduced to 60% and 80% of habitual rates using four different pacing strategies (Additive Metered, Additive Rhythmic, Cued Metered, and Cued Rhythmic). Effects of rate control on sentence and phoneme intelligibility and speech naturalness were examined. Sentence intelligibility improved for both groups, with metered pacing conditions associated with the largest improvement in scores. Similar improvements as speaking rates were reduced were not seen for the phoneme intelligibility task; however, one must recognize that sentence and phoneme intelligibility tasks are different. Slowing the rate of dysarthric speakers did not have as marked an impact on speech naturalness as it did for normal speakers whose naturalness decreased at slowed rates. Metered rate control strategies were associated with the lowest ratings of naturalness for all subject groups. A potential explanation for the discrepancies between the findings for sentence and phoneme intelligibility is offered.