Predicting perceptual outcomes from acoustic measures of vowels in dysarthria: A classification analysis.

Abstract

Reductions in vowel space presumably obscure the distinctiveness of vowels produced by individuals with dysarthria. This represents a source of intelligibility decrement to the extent that more ambiguous vowels influence access of correct lexical items. The present study sought to examine (1) whether vowel formant frequencies predict perceptual decisions through classification analysis and (2) whether different forms of dysarthria are associated with different classification outcomes. Productions of phrases containing the target vowels /i/, /ɪ/, /ε/, /æ/, /u/, /o/, /ɑ/, and /ʌ/ in strong syllables were obtained from patients whose speech was affected by one of four neurological impairments: Parkinson disease, Huntington disease, amyotrophic lateral sclerosis, or cerebellar degeneration. The first two formant frequencies of each vowel were measured at its midpoint and then subjected to a classification analysis. Classification rules based on the acoustic measurements were used to classify each token as one of the eight target vowels. For each speaker group, the performance patterns obtained by the classification analysis were compared to those made by 15 listeners in an open transcription task. The ability of the classification analysis to predict perceptual outcomes specific to each dysarthric speaker group will be discussed. [Work supported by NIH/NIDCD.]