| Abstract | Objective:
Voice production of humans is governed by the MyoElastic-AeroDynamic (MEAD) principle, where an air stream is modulated by self-sustaining vocal fold oscillation to generate audible air pressure fluctuations. An alternative mechanism is found in ultrasonic vocalizations of rodents, which are established by an aeroacoustic (AA) phenomenon without vibration of laryngeal tissue. Previously, some authors argued that high-pitched human vocalization is also produced by the AA principle.
Material and Methods:
Nine professional female operatic sopranos were asked to sing pitches from C6 (fo ≈ 1047 Hz) to G6 (fo ≈ 1568 Hz). Recording was performed using transnasal high-speed videoendoscopy with 20.000 fps combined with simultaneous electoglottographical and audio signals. After segmentation of the images, the glottal area waveform and glottovibrograms were generated. In order to reproduce the experimental findings, a computational modeling approach using a finite difference model of vocal fold tissue vibration with string-like restoring forces was conducted.
Results:
The recordings revealed vocal fold collision in all participants, with closed quotients from 30% to 73%. Computational modeling suggests a vocal fold strain of about 50%, facilitated by high subglottal pressures and increased contraction of the cricothyroid muscle. In the experiments, two major configurations of vocal fold closures could be identified: 4 subjects used closure with a posterior gap and 5 subjects phonated with full glottal closure where three of these exhibited partial opening of the vocal folds, occurring along 40 % to 50 % of the visible vocal fold length. A computed reproduction of both glottal configurations showed the production of self-sustained oscillation at a fiber stress of 0.9 MPa for both cases.
Conclusion:
The presented data suggest that high-pitched operatic soprano singing uses the MEAD mechanism. Consequently, the commonly used term “whistle register” is inappropriate for this singing style at the investigated pitches.
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