Ultrasonic Study of Vocal-Fold Vibration in Normal and Nasalized Vowels
Sandra L. Hamlet · The Journal of the Acoustical Society of America · 1972
Nasal coupling reduces the over-all intensity of a vowel, requiring greater vocal effort to match intensity of a nonnasal vowel. The question is to what extent increased vocal effort for nasal vowels is reflected by a change in duty cycle of vocal-fold vibration. Duration of the vibratory open phase was taken as the time within each cycle during which ultrasonic transmission through the larynx was blocked by reflection from the glottal rim. This measurement is consistent over the small range of transducer positions permitting the ultrasonic beam to pass through the approximate vertical and horizontal midpoint of the vocal folds. At matched microphone signal smplitudes, duty cycles differ for normal and nasalized sustained vowels, spoken at the same vocal fundamental frequency. Results are reported for preadolescent boys. [This investigation was supported by a NIH Grant.]