Characterizing the Variability of Second Formant Frequencies in Vowels of Dysarthric Speech Classified by Diphthong and Monophthong

Abstract

This study investigated the effects of variability in the second formant (F2) of monophthongs and diphthongs on intelligibility in patients with dysarthria. The research also examined the relationship between lexical stress and intelligibility. Data from 4 speakers and 30 listeners were collected from previous studies and retrospectively analyzed. Monophthongs were measured at onset, midpoint, and offset according to the fixed-point method while diphthongs were measured at the vowel onset and offset. The variability of these measurements were correlated with intelligibility via a linear-regression model. No significant effect was found for stress. Variability of monophthongs at midpoint and offset had a direct relationship with intelligibility, while variability of diphthongs at onset demonstrated an inverse relationship with intelligibility.