The Effect of Rate Control on Speech Rate and Intelligibility of Dysarthric Speech

Abstract

Purpose: This study investigated the effect of rate control methods (RCMs) on speaking rate (SR), articulation rate (AR), and intelligibility in dysarthric speakers. Method: Nineteen dysarthric patients (7 unilateral upper motor neuron dysarthria, 6 hypokinetic, 3 flaccid, 3 ataxic) participated. SR, AR and intelligibility ratings were determined on the basis of 1-min recorded reading passages. Seven RCMs were applied: voluntary rate control, hand tapping, alphabet board, pacing board and delayed auditory feedback with a delay of 50, 100 and 150 ms. Results: Almost all methods resulted in lower mean SRs and ARs (p < 0.05). Rate control did not improve overall intelligibility of the dysarthric population. However, a meaningful increase of intelligibility was found in 5 participants. This study indicates that the effect of rate control on intelligibility is independent of habitual speech rate and type of dysarthria. Degree of intelligibility may be an influencing factor. The most effective methods are: voluntary rate control, alphabet board, hand tapping and pacing board. Conclusion: RCMs do result in lower speech rates. Some dysarthric individuals do benefit from one or more RCMs, but rate control may also have an inverse effect on intelligibility.

Effect of Rate Control on Speech Production and Intelligibility in Dysarthria

“…These results are in accordance with those of other studies [11][12][13][14][15][16][17][18][19][20] and our previous study [5] , and confirm that most RCMs applied in clinical practice to reduce speech rate are effective. The RCMs that most effectively reduced AR and SR were pacing board, hand tapping and alphabet board.…”

“…The majority of the participants with significantly improved intelligibility had SRs and ARs within normal boundaries or even decreased rates. These results add credence to the results of the initial study [5] and the findings of Jaeger et al [24] who found that individuals with dysarthria tend to speak near the upper limit of their SR.…”

“…Whereas only slower on demand, alphabet board, pacing board and hand tapping led to significantly increased intelligibility in the initial study [5] , the extended data reveal that each of the investigated RCMs is able to significantly improve intelligibility of dysarthric speech.…”

“…The methods used in the current study are in accordance with the methods used in the previous study [5] .…”

“…In their 2007 systematic review of evidence on the effectiveness of treatment of loudness, rate and prosody in dysarthria, Yorkston et al [4] indicated that treatment studies comparing various RCMs would be necessary in the future. In 2008, Van Nuffelen et al [5] published a study that compared the effect of 7 RCMs on articulation rate (AR), speaking rate (SR) and intelligibility in dysarthria. The 7 methods were: speaking slower on demand, pacing board, alphabet board, hand tapping, delayed auditory feedback with delays of 50 ms (DAF50), 100 ms (DAF100) and 150 ms (DAF150).…”