Acoustic analysis of Korean stop sounds in patients with dysarthrias

Abstract

Dysarthria is a motor speech disorder that occurs due to abnormalities in the central and/or peripheral nervous system. The speed, strength, range, steadiness, and tone of motor speech behaviors are affected by the abnormal performances of nerve fibers and muscles [1,2]. This disorder is known to influence five speech components, including respiration, phonation, articulation, prosody, and resonance [1,2]. Because all phonemes in the language are influenced by the disorder, the overall intelligibility, rather than the percentage of correctly produced consonants, has been of interest to both clinicians and researchers."Speech intelligibility" is a measurement that scores how much listeners can under-Purpose: Korean 'stops' are considered an especially good acoustic variable since they are sensitive to speech intelligibility and reflect physiological coordination between laryngeal and supra-laryngeal mechanisms. The purpose of the study was to evaluate the acoustic characteristics of both the dysarthria and control groups in the production of nine Korean stops, /p, p', p h , t, t', t h , k, k', k h /, in VCV contexts. Methods:The participants comprised eight patients with dysarthria and eight age-and gender-matched normal adults. After the acoustic analysis of the closure duration, aspiration duration, and the ratio of closure duration to closure-aspiration combined duration, the results were compared among three types of phonation and places of articulation for Korean stops.Results: The dysarthria group (DG) had longer closure durations, suggesting slower articulatory movements of the DG than the normal control group (NC). Although statistically not significant except for /ap'a/ and /at'a/, the absolute aspiration durations of the DG were still longer than those of the NC. This resulted in the normal levels of ratios in the DG between closure duration and closure-aspiration combined durations. Furthermore, the DG could change the durational aspects of stop production distinctively according to types of phonation more than they could according to the places of articulation. This trend was more prominent during the closure duration than during the aspiration duration.Conclusions: This finding suggested that while the DG has centralized tongue positions, they control the tenseness and the timing coordination between laryngeal and supra-laryngeal articulators to distinctively produce different types of phonation of stops.