Vowel area and intelligibility in children with and without dysarthria

Vowel quadrilateral areas based on first (F1) and second (F2) formant measures of the corner vowels \i\, \ae\, \a\ and \u\ were determined from words produced by six children with dysarthria and six age-mates with normal neurological histories and speech production. The children's F1 X F2 vowel areas were used to test hypotheses about (a) effect of dysarthria on vowel area, and (b) relationship between speech intelligibility and vowel area. Results were in agreement with previous investigations of adults with and without dysarthria. Vowel areas for the children with dysarthria were significantly smaller than those of their age-mates without dysarthria, largely due to a reduction in F2 extent that was most obvious for the back vowel \a\. Positive correlations were obtained between vowel areas and scores on a single word (r = .73) and a sentence intelligibility test (r = .64).