Acoustic Properties of Vowel Production in Mandarin-Speaking Patients With Parkinson Disease-Related Hypokinetic Dysarthria.

Abstract

Objective: The objective of the present study is to identify acoustic parameters for speech evaluation in patients who speak Mandarin, with Parkinson disease-related hypokinetic dysarthria (PDHD).

Methods: The authors' sample included 31 patients with PDHD and 38 neurologically normal adults in a similar age range. The authors recorded each participant articulating a list of Mandarin monosyllables that included 6 monophthong vowels (i.e., /a, i, u, ɤ, y, o/). The authors identified the vowel duration (V-dur) and formants (F1 and F2) of each vowel token. On the basis of the formants, the authors calculated and analyzed the acoustic indexes of vowel space area (VSA), vowel articulation index (VAI), and formant centralization ratio (FCR) of the vowels.

Results: Compared with healthy speakers, patients with PDHD had a significantly longer vowel duration for all 6 vowels (P < 0.01). The differences in VSA, VAI, and FCR between the case and normal groups were all statistically significant.

Conclusions: Differences in vowel acoustic indexes (V-dur, VSA, VAI, and FCR) between the 2 groups revealed that these 4 indexes were sensitive to the variation in vowel production in patients with PDHD. These indexes can be used to evaluate speech intelligibility caused by impaired vowel pronunciation in patients with PDHD and the outcome of rehabilitation therapy.