Intelligibility as a linear combination of dimensions in dysarthric speech

Speech samples of 79 dysarthric patients (native speakers of English) were judged by two experienced judges by means of a perceptual rating scale covering the four main dimensions of speech production: voice quality, articulation, nasality and prosody as well as overall intelligibility. In order to determine the relative influence of the four basic dimensions on intelligibility in this study group. a multiple regression model was applied. This model shows that intelligibility can be expressed as a linear combination of weighted perceptual dimensions (R-2 = 0.89). This expression reveals the relative importance of the individual dimensions on overall intelligibility. Articulation is shown to be the strongest contributor to intelligibility. A group of 16 dysarthric patients (native speakers of Dutch) was used as a control group in order to evaluate the validity of the expression. Judged and calculated ratings (within the 95% prediction intervals) were in agreement for 75% of the patients. These findings may contribute in the construction of a better balanced measure of functional intelligibility. Learning outcomes: 1. Intelligibility can be expressed by a linear combination of weighted single dimensions indicating the relative impact of each of them. 2. The impact of articulation on intelligibility is dominant but inclusion of the dimensions "nasality". "voice" and "prosody" results in a more balanced estimation of intelligibility. (C) 2002 Elsevier Science Inc. All rights reserved.