Resonance strategies and glottal behaviour in singing
Nathalie Henrich[1,2], Elodie Joliveau, John Smith and Joe Wolfe
1. Laboratoire d'Acoustique Musicale, Paris, France
2. School of Physics, University of New South Wales, Sydney, Australia
In Fant's classic model, the spectrum of sound radiated by a singer depends on the 'source' and the 'filter'. The source is the nearly periodic vibrations of the vocal folds, which we study here with electroglottography[2,3]. The filter is the vocal tract, which acts as a variable impedance matcher (a 'megaphone') between the vocal folds and the external radiation field. The impedance matching is most efficient (and so produces enhanced vocal power) around the resonances of the vocal tract. The resonances thus produce formants (local maxima in the power spectrum) in the sound, of which the first two are important in vowel identification, and the next few in vocal quality and speaker identification. We study the vocal tract response directly by injecting a carefully synthesised, broad band acoustic current at the mouth[4,5]. The simultaneous use of these techniques allows us to identify spectral features in the singing voice (recorded at the same time) with the behaviour of the glottis and the tract.
We find that, in the high range of the female voice, singers trained in the Western tradition tune the lowest resonance (R1) of the tract to match the pitch frequency f0. This has the musical advantages of increasing radiated power and improved vocal homogeneity, but probably contributes to the difficulty of discriminating vowels at high pitch. The variation with pitch of the higher resonances (R2, R3, R4 and R5) is not associated with analogous tuning. In the high range of the male voice, some singers tune lower resonances to higher harmonics of the voice, but only for some vowels. We also compare the higher resonances (R3, R4 and R5) with those measured in speech in search of the singers' formant.
1. Fant, G. Speech Sounds and Features. MIT, Cambridge, Mass, 1973.
2. Childers D.G. and Krishnamurthy A.K. (1985) "A critical review of electroglottography", CRC Critical Reviews in Biomedical Engineering, 12, pp. 131-161.
3. Henrich, N., d'Alessandro, C., Castellengo, M., and Doval, B. (2004)
"On the use of the derivative of electroglottographic signals for characterization of nonpathological phonation", J. Acoustical Society of America, 115 (3), in press.
4. Epps, J., Smith, J.R. and Wolfe, J. (1997) "A novel instrument to measure acoustic resonances of the vocal tract during speech" Measurement Science and Technology, 8, 1112-1121.
5. Joliveau, E., Smith, J. and Wolfe, J. (2004) "Tuning of vocal tract resonances by sopranos", Nature, 427, 116.
7. Sundberg, J. The Science of the Singing Voice, Northern Illinois Univ. Press., De Kalb, Ill, 1987.
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