The Relationship Between Acoustic and Kinematic Vowel Space Areas With and Without Normalization for Speakers With and Without Dysarthria

Abstract

Purpose: Few studies have reported on the vowel space area (VSA) in both acoustic and kinematic domains. This study examined acoustic and kinematic VSAs for speakers with and without dysarthria and evaluated effects of normalization on acoustic and kinematic VSAs and the relationship between these measures. Method: Vowel data from 12 speakers with and without dysarthria, presenting with a range of speech abilities, were examined. The speakers included four speakers with Parkinson's disease (PD), four speakers with brain injury (BI), and four neurotypical (NT) speakers. Speech acoustic and kinematic data were acquired simultaneously using electromagnetic articulography during a passage reading task. Raw and normalized VSAs calculated from corner vowels /i/, /æ/, /ɑ/, and /u/ were evaluated. Normalization was achieved through z score transformations to the acoustic and kinematic data. The effect of normalization on variability within and across groups was evaluated. Regression analysis was used across speakers to assess the association between acoustic and kinematic VSAs for both raw and normalized data. Results: When evaluating the speakers as three different groups (i.e., PD, BI, and NT), normalization reduced the standard deviations within each group and changed the relative differences in average magnitude between groups. Regression analysis revealed a significant relationship between normalized, but not raw, acoustic and kinematic VSAs, after the exclusion of an outlier speaker. Conclusions: Normalization reduces the variability across speakers, within groups, and changes average magnitudes affecting speaker group comparisons. Normalization also influences the correlation between acoustic and kinematic measures. Further investigation of the impact of normalization techniques upon acoustic and kinematic measures is warranted. Supplemental Material: https://doi.org/10.23641/asha.22669747

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

“…Lee and colleagues (2017) examined the relationship between acoustic and kinematic VSA in speakers with dysarthria due to amyotrophic lateral sclerosis (ALS) and found the two measures to be highly correlated (𝜌 = .918). However, a recent study by Kuo and Berry (2023) found a very low correlation between the two measures from speakers with PD or brain injury and typical speakers (𝑟 = .15, 𝑅 2 = .02). More data is needed to understand the relationship between acoustic and kinematic VSA, especially given the heterogeneity of the research methods of the studies including the underlying neuropathologies of the participants and speech stimuli used.…”

“…As an example, the vowel /ae/ in the target word "Dan" often exhibited a low F1 value in our study, likely attributed to the coarticulatory effects of the surrounding /d/ and /n/ phonemes. Similarly, Kuo and Berry (2023) used tokens from connected speech (i.e., The Caterpillar Passage, Patel et al, 2013) to calculate acoustic and kinematic VSAs. Consequently, like the current study, the stimuli in their study were likely highly coarticulated, leading to the inconclusive relationship observed between acoustic and kinematic VSA.…”

Vowel production: a potential speech biomarker for early detection of dysarthria in Parkinson’s disease

“…Moreover, we ensured that the relative proportions of men and women in each group were identical to ensure the relevance of comparisons between groups even though the data was not standardized. Examining the effects of normalizing formant values, as recently proposed by Kuo and Berry (2023) , may be relevant to a future study.…”