Vowel Acoustics as Predictors of Speech Intelligibility in Dysarthria

Abstract

Purpose: This study sought to determine if alternative vowel space area (VSA) measures (i.e., novel trajectory-based measures: vowel space hull area and vowel space density) predicted speech intelligibility to the same extent as two traditional vowel measures (i.e., token-based measures: VSA and corner dispersion) in speakers with dysarthria. Additionally, this study examined if the strength of the relationship between acoustic vowel measures and intelligibility differed based on how intelligibility was measured (i.e., orthographic transcriptions [OTs] and visual analog scale [VAS] ratings). Method: The Grandfather Passage was read aloud by 40 speakers with dysarthria of varying etiologies, including Parkinson's disease ( n = 10), amyotrophic lateral sclerosis ( n = 10), Huntington's disease ( n = 10), and cerebellar ataxia ( n = 10). Token- and trajectory-based acoustic vowel measures were calculated from the passage. Naïve listeners ( N = 140) were recruited via crowdsourcing to provide OTs and VAS intelligibility ratings. Hierarchical linear regression models were created to model OTs and VAS intelligibility ratings using the acoustic vowel measures as predictors. Results: Traditional VSA was the sole significant predictor of speech intelligibility for both the OTs ( R 2 = .259) and VAS ( R 2 = .236) models. In contrast, the trajectory-based measures were not significant predictors of intelligibility. Additionally, the OTs and VAS intelligibility ratings conveyed similar information. Conclusions: The findings suggest that traditional token-based vowel measures better predict intelligibility than trajectory-based measures. Additionally, the findings suggest that VAS methods are comparable to OT methods for estimating speech intelligibility for research purposes.

Increased vowel contrast and intelligibility in connected speech induced by sensorimotor adaptation

“…Of note for basic and applied speech researchers, the choice of vowel-space metric impacted our results (Thompson et al, 2023;Fox & Jacewicz, 2017;Story & Bunton, 2017;Kim et al, 2011). Consistent with our previous study (Parrell & Niziolek, 2021), AVS was sensitive to adaptation to vowel centralization, as it incorporates all inter-vowel distances.…”

Acoustic and kinematic predictors of intelligibility and articulatory precision in Parkinson’s disease

“…This finding highlights the meaningful and important role of acoustic VSA as a predictor of intelligibility and aligns with previous research reporting moderate associations between intelligibility and acoustic VSA measures (Y-J. Kim et al, 2011;Liu et al, 2005;Thompson et al, 2023;Weismer et al, 2001). Overall, our study agrees with previous reports that acoustic VSA is a promising predictive measure of speech intelligibility.…”

A multidimensional examination of vowel-related articulatory deficits in Parkinson’s disease

“…The SD of listener ratings ranged from 11.73 to 37.64, with lower SD values observed for speakers at the extremes of the intelligibility and articulatory precision spectrum and higher SD values for speakers in the mid-range of the spectrum. These SD ranges are consistent with previous studies that employed the VAS method for perceptual ratings (Thompson et al, 2023). Given that not all listeners rated the same speakers, using the Intraclass Correlation Coefficient (ICC) was not appropriate for measuring inter-listener reliability in this study.…”