Objective: The purpose of this study was to explore the possibility of using Lyapunov exponents (LE) to evaluate the voice and speech in cleft palate (CP) patients. Subjects and Methods: Fifty healthy adults (25 males and 25 females) and 17 adult patients (10 males and 7 females) with repaired CP, who had no hypernasality, were enrolled. Five Japanese vowels were recorded at 44.1 kHz. Nasalance scores were measured simultaneously. The first LE was computed for each 1-second interval, and the mean for the first LE from all intervals (mLE1) was then calculated. The delay time and embedding dimension were estimated at 13, 40, 34, 27 and 22 points for the vowels /a/, /i/, /u/, /e/ and /o/, respectively, and at 8 points for all vowels. Results: The mLE 1s for all vowels did not differ between normal males and females. The mLE1s for /a/ were significantly higher both in males and females with CP than in normal individuals. The correlation coefficient between the mLE1s and nasalance scores for all vowels was not significant for both normal and CP subjects. Conclusion: The LE seemed to be related to pathological disorders of the vocal cords in CP patients, but was independent of resonance parameters.
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