Estimating the intelligibility of speakers with dysarthria

Many speakers with dysarthria have reduced intelligibility, and improving intelligibility is often a primary intervention objective. Consequently, measurement of intelligibility provides important information that is useful for clinical decision-making. The present study compared two different measures of intelligibility obtained in audio-only and audio-visual modalities for 4 different speakers with dysarthria (2 with mild-moderate dysarthria; 2 with severe dysarthria) secondary to cerebral palsy. A total of 80 college-aged listeners provided word-by-word transcriptions and made percent estimates of intelligibility which served as dependent variables. Group results showed that transcription measures were higher than percent estimates of intelligibility overall. There was also an interaction between speakers and measures of intelligibility, indicating that the difference between transcription scores and percent estimates varied among individual speakers. Results revealed a significant main effect for presentation modality, with the audio-visual modality having slightly higher scores than the audio-only modality; however, presentation modality did not interact with speakers or with measures of intelligibility. Results suggest that standard clinical measurement of intelligibility using orthographic transcription may be more consistent than the use of more subjective percent estimates.