A hypothesis about whistle voice.
The hypothesis here is that whistle voice makes use of a source-vocal tract interaction based on acoustic inertance below the third formant. Acoustic inertance of the vocal tract helps to set the vocal folds into vibration. (2) For a female vocal tract (see eleven vowel shapes in Figure 1a), the third formant occurs above 3000 Hz and vocal tract inertance is found for most vowel shapes if frequencies are in the 1500--3000 Hz range. This range is on the upskirt of the third formant [F.sub.3] (see Figure 1b, where formants [F.sub.1], [F.sub.2], and [F.sub.3] are labeled for the vowel /o/). Formants (the resonances of the vocal tract) are where the inertance curves make an upward turn followed by a sharp drop. When the inertance is high (above the zero line), source frequencies are reinforced. In particular, the fundamental frequency [F.sub.0] gets a boost. Note that for the /o/ vowel shape, the inertance curve is above zero for pitches slightly below and above [C.sub.7]. But the higher harmonics ([2F.sub.0], [3F.sub.0], [4F.sub.0] ...) are not systematically reinforced. They face variable inertances from the vocal tract. Note that the harmonics [2F.sub.0], [3F.sub.0], and [4F.sub.0] lie in the midst of a cluster of formants above [F.sub.3]. Similar situations occur for most of the other vowel shapes. Thus, the frequency range below and above [C.sub.7] (1500--3000 Hz) is particularly advantageous and consistent for the fundamental [F.sub.0], but quite irregular for higher harmonics.
Two examples of spectrograms of whistle voice of recorded artists are shown in Figures 2 and 3. Figure 2 is from Georgia Brown, a Brazilian recording artist. (3) She produces a long sustained whistle note at [F.sub.0] = 2400 Hz (about D7) without vibrato, followed by a lower note with vibrato at 1860 Hz (about B-[flat.sub.6]). For both notes, the fundamental [F.sub.0] is very strong, apparently reinforced by vocal tract inertance. The second harmonic [2F.sub.0] is also strong, but no higher harmonics are evident in the first note. In the second note, the third harmonic has some energy. The exact vowel shape used by the performer is not known, but it would appear from Figure 1b that vowel shapes like /a/ and /i/ would have both [F.sub.0] and [2F.sub.0] reinforcement, whereas a shape like /o/ could also have [3F.sub.0] reinforcement.
The second example (Figure 3) is a spectrogram of Mariah Carey, an American female pop singer.4 In the recording, she produces a series of vocal glides to a maximum fundamental frequency of 2400 Hz (about D7, where [F.sub.0] is labeled). Some energy is seen in both [2F.sub.0] and [3F.sub.0], but the energy is mostly in [F.sub.0] at all pitches.
[FIGURE 1 OMITTED]
The examples shown here support the hypothesis that whistle voice may be a production in which the fundamental frequency [F.sub.0] is strongly reinforced by vocal tract interaction below [F.sub.3]. Supraglottal inertance is known to support vocal fold oscillation by lowering the phonation threshold pressure. The frequency range of about 1500 Hz to 3000 Hz lies in an inertance region (the upskirt of the third formant) in females. Occasionally, whistle voice reaches the 4000--5000 Hz region. This would be in the vicinity of C8 for [F.sub.0]. It is not clear from Figure 1 which vowel shape or formant structure would support such a high fundamental frequency.
Higher harmonics are not systematically reinforced for whistle voice, but may for some pitches find favorable inertance offered by formants 4-6. Much future work is needed to sort out the interactions between source harmonics and the vocal tract.
[FIGURE 2 OMITTED]
[FIGURE 3 OMITTED]
(1.) D. G. Miller and H. K. Schutte, "Physical Definition of the 'Flageolet Register,'" Journal of Voice 7, no. 3 (September 1993): 206-212.
(2.) I. R. Titze, Principles of Voice Production (Denver, CO: National Center for Voice and Speech,2000), Chapter 4.
(3.) Recording of Georgia Brown: sound clip from:www.dutchdivas.net/nighC.html (link to http://escravosdegeo.sites.uol.com.br/index1.htm), last accessed 11/27/07.
(4.) Recording of Mariah Carey: www.youtube.com/watch?v=EUUE4ePt8Xc, last accessed 11/30/07.
Ingo R. Titze is Distinguished Professor of Speech Science and Voice at the University of Iowa and Executive Director of the National Center for Voice and Speech at the Denver Center for the Performing Arts. His formal education is in physics and electrical engineering, but he has devoted much of his studies to vocal music and speech. Dr. Titze has published more than 500 articles in scientific and educational journals, coedited two books titled Vocal Fold Physiology, and has authored two books called Principles of Voice Production, and The Myoelastic Aerodynamic Theory of Phonotion. He has lectured throughout the world and has appeared on such educational television series as Innovation, Quantum, and Beyond 2000. He is a recipient of the William and Harriott Gould Award for laryngeal physiology, the Jacob Javits Neuroscience Investigation Award, the Claude Pepper Award, the Quintana Award, and the American Laryngological Association Award. He is a Fellow of the Acoustical Society of America and the American Speech-Language-Hearing Association. Dr. Titze has served on a number of national advisory boards and scientific review groups, including the Scientific Advisory Board of the Voice Foundation and the Division of Research Grants of the National Institutes of Health. In addition to his scientific endeavors, Dr. Titze continues to be active as a singer. He is married to Kathy Titze and has four children. Mail should be addressed to Ingo R. Titze, National Center for Voice and Speech, 330 WJSHC, Iowa City, IA 52242. Telephone (319) 335-6600.
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|Title Annotation:||VOICE RESEARCH AND TECHNOLOGY|
|Author:||Titze, Ingo R.|
|Publication:||Journal of Singing|
|Date:||Mar 1, 2008|
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