Variability of F2 Transitions in Dysarthria
Abstract
The slope of second formant (F2) frequency transitions is an acoustic measure of the rate of change of vocal tract configuration. Previous research suggest reduced F2 slopes for speakers with dysarthria versus healthy controls. Other studies suggested a strong correlation of F2 slope and speech intelligibility, indicating that F2 slope is a relatively easily obtained measure with the potential to serve as an index of speech severity. Whilst acoustic measures usually include transition duration, extent, and slope derived from a small number of averaged values, thus far no studies have considered the stability of F2 transitions over repeated productions. Stability (inversely: variability) indices derived from kinematic and acoustic measures obtained from repeated productions at the sentence-level have been found to be valid indicators of speech motor involvement, and sensitive to different speaking demands, including changes in speaking rates. This study investigated whether the quantification of variability of F2 transitions metrics could be used to characterize dysarthria. Particularly, we investigated whether these repetition-to-repetition variability measures showed similar sensitivity compared to averaged F2 transition measures, and whether they could potentially reveal aspects of speech motor control deficits in dysarthria not fully captured by averaged measures. Speakers with hypokinetic dysarthria, ataxic (-spastic) dysarthria, and control speakers produced twenty sentence repetitions containing the diphthong /aI/ with F2 transitions of interest. Durational and spatial variability metrics were derived, compared by group, and correlated with intelligibility measures. We report on the ability of these metrics to characterize dysarthria, and evaluate the effects of different speaking rates.
Frits van Brenk
External consultant in the Motor Speech Disorders Laboratory
My research and teaching interests include motor speech disorders, clinical linguistics, experimental psycholinguistics, speech science, and research methods.