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Evaluation of hypernasality in vowels using voice low tone to high tone ratio
Guo-She Lee1, Ching-Ping Wang, Sherry Fu
1Department of Otolaryngology, Faculty of Medicine, School of Medicine, National Yang-Ming University, Taipei City 112 Taiwan. gslee@ym.edu.tw
Objective:
The voice low tone to high tone ratio (VLHR) is defined as the power ratio of low frequency to high frequency energy obtained by dividing the voice spectrum with a specific cutoff frequency. In a previous study, VLHR correlated significantly with nasalance and perceptual rating of hypernasality for a single vowel. The methodology was optimized in this study by investigating the correlations among other vowels.
Design:
Voice signals of six sustained vowels vocalized by subjects with hypernasality were collected. Vowel nasalance was obtained with a nasometer, and hypernasality rating scores were provided by two speech-language pathologists. The VLHRs calculated using different cutoff frequencies were correlated with nasalance and hypernasality rating scores.
Participants:
Eight subjects with hypernasality caused by palatal fistula or velopharyngeal insufficiency.
Main Outcome Measures:
VLHR, nasalance, and hypernasality rating score.
Results:
The correlation of VLHR with nasalance and hypernasality rating was most significant using a cutoff frequency of 600 Hz. The correlation of VLHR with nasalance was significant (r = .62, p < .01, Pearson's correlation), as was the correlation of VLHR with hypernasality score (Spearman's rank correlation coefficient = .62, p < .01).
Conclusions:
VLHR correlated significantly with nasalance and hypernasality in the six sustained vowels and may provide another quantitative index for the evaluation of hypernasality in sustained vowels.
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