Abstract
Statement of Problem
Previous studies have shown that the use of an alphabet board by an individual with dysarthria can significantly increase the individual's speech intelligibility. Alphabet cues have been shown to reduce rate of speech, rate of articulation, and increase length and occurrence of pauses (Bustad & Garcia, 2005). These changes provide the speaker with opportunities to modify speech, as well as allow the listener more processing time. It is unclear if the increase in intelligibility is a result of the use of alphabetic cues alone, the accompanying acoustic changes, or a combination of both factors. Previous studies have shown mixed results and indicated that severity of dysarthria may be a factor as well. The present study was conducted to answer the following question: What variables associated with the use of an alphabet board (e.g. signal-dependent, signal-independent, or a combination of both variables) are responsible for the increases in speech intelligibility? An answer to this question may help in clinical decision-making
regarding therapy of individuals with dysarthria.
Sources of Data
Three members of the United Cerebral Palsy Organization of Sacramento were recruited to participate in this study. Each speaker was asked to produce 10 scripted sentences while using an alphabet board Two video recordings were produced: an audio-only recording (i.e. the speaker was utilizing an alphabet board, but the visual of an alphabet board was not seen in the recording) and an audiovisual recording (i.e. with the visual of an alphabet board). Thirty listeners judged their performance by transcribing the recordings. The transcription data was then used to see if there was a statistically significant difference between mean intelligibility scores between presentation modes.
Conclusions Reached
Mean intelligibility scores for all speakers showed a statistically significant increase across presentation modes, with a combined average increase of6.2% · (p=0.00269). Individual results varied Speaker 1, who had the lowest intelligibility scores across listeners, showed a statistically significant increase in mean intelligibility scores, with an average increase of8.2% (p=0.03708). Speaker 3 also showed a statistically significant increase in intelligibility scores, with an average increase of intelligibility scores of7.0% (p=0.04698). Speaker 2, who had the highest intelligibility scores and demonstrated the least severe dysarthric symptoms, did not show a statistically significant increase in intelligibility scores, with an average increase of3. 2% (p=0.14600). Based on these findings, it can be inferred that intelligibility of speech increased due to visual cues provided to the listener (i.e. the alphabet board). If the changes in intelligibility were due to acoustic changes only, the intelligibility scores across modes would have been similar and changes in intelligibility would not have been statistically significant.