Vocal Fold Vibration of the Whistle Register Observed by High-Speed Digital Imaging

Abstract

Singers use a whistle register to sing at a fundamental frequency above 1000Hz. In previous studies, vocal fold vibrations with or without complete closure and partial vocal fold vibrations were observed depending on the subject. However, the production mechanism of the whistle register is not yet clearly understood because of the limitations of the imaging device for the glottis and subjects. This study aims to examine vocal fold vibrations in a whistle register. The dynamic behavior of the glottis was recorded for six singers (four females and two males) using a high-speed digital imaging device with a frame rate above 10,000fps. Audio signals were recorded simultaneously. The data were analyzed in the form of topography, glottal area waveforms, spectrograms, and phonovibrography to examine spatiotemporal patterns of glottal motion. The vibratory motion of the vocal folds was classified into six patterns. The first pattern was the entire vocal fold vibration with complete closure during the closed phase. The second to fifth was the entire vocal fold vibration without complete closure, where a gap was observed for the full length of the vocal folds for the second, at the posterior part of the glottis for the third, at the anterior for the fourth, and at both ends for the fifth. In the sixth pattern, the vocal folds vibrated partially. Our results support the previous findings on the vibration of the vocal folds. In addition, we identified novel vibratory patterns in the vocal folds. We conclude that the production of the whistle register is not just an extension of the falsetto register to the higher fundamental-frequency region; rather, the production mechanism of the whistle register appeared to be diverse as a means of vocalization.