An MRI-based Acoustic Study of Mandarin Vowels

This study aims at exploring detailed acoustic characteristics of Mandarin sustained vowels based on magnetic resonance imaging (MRI). Cross-sectional area functions of the vocal tract for Mandarin vowels were extracted from volumetric MRI images obtained from eight Chinese speakers (six-male and two-female subjects). Acoustic analysis was performed for the vowels recorded from each speaker. The acoustic analysis includes comparisons between measured and calculated formants, vowel space, simplified models for Mandarin vowels, and correlation between vocal tract length and formant frequencies. Mean absolute errors of calculated formants across 10 Mandarin vowels over eight subjects ranged from 4.6% to 11%. Simple-model also offers good approximations for Mandarin vowels. Since the simple model can give relatively clear relation between acoustic characteristics and vocal tract properties, it is useful for intuitively understanding the mechanism of speech production. The correlation analysis suggests that there exist negative correlations between vocal tract length and first four formants for Mandarin vowels in general, which showed a clearer relation than a recent study by another research group.