Evaluation of hypernasality in vowels using voice low tone to high tone ratio.
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.


METHODS
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.


METHODS
Eight subjects with hypernasality caused by palatal fistula or velopharyngeal insufficiency.


METHODS
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.
Lee
Guo-She
GS
Department of Otolaryngology, Faculty of Medicine, School of Medicine, National Yang-Ming University, Taipei City 112 Taiwan. gslee@ym.edu.tw
Wang
Ching-Ping
CP
Fu
Sherry
S
D000328:Adult; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015508:Nasal Obstruction / Q000175:diagnosis*; D016155:Oral Fistula / Q000150:complications; D010699:Phonation; D016156:Respiratory Tract Fistula / Q000150:complications; D025363:Rhinomanometry; D013018:Sound Spectrography; D013061:Speech Acoustics; D014681:Velopharyngeal Insufficiency / Q000150:complications; D014732:Vibration; D014831:Voice; D014832:Voice Disorders / Q000175:diagnosis* / Q000209:etiology; D014833:Voice Quality