Vowel characteristics associated with Cantonese speakers of Parkinson's disease : an acoustic study

Abstract

The present study examined vowel articulatory characteristics associated with Hong Kong Cantonese speakers with Parkinson’s disease (PD) along disease progression. Mean values of the first two formants (F1 and F2) associated with the three Cantonese corner vowels (/i, u, a/) were obtained through reading of standard carrier phrases by 18 PD patients (11 at mild stage and 7 at moderate stage) and 30 neurotypical (NT) controls aged between 45 and 83 years. Six derived formant metrics were calculated and results revealed significant differences between neurotypical and hypokinetic speech along the different aspects of vowel articulation. Mild PD speakers were also found to have a significantly lower value in F1RR and tVSA than NT speakers, as well as a significantly higher F1RR value than moderate PD speakers. The findings demonstrated articulatory undershooting manifested in a reduction in working vowel space and vowel dispersion, as well as an increase in vowel centralization in PD speakers. tVSA and F1RR are proposed to be sensitive acoustic measures for assessing subtle vowel articulatory changes. tVSA may also be used as a biofeedback in treatment for mild PD speakers, with superior-inferior lingual movement and jaw opening as the initial treatment targets for improving patients’ speech intelligibility.