The effect of whisper and creak vocal mechanisms on vocal tract resonances.

The frequencies of vocal tract resonances estimated using whisper and creak phonations are compared with those in normal phonation for subjects who produced pairs of these phonations in the same vocal gesture. Peaks in the spectral envelope were used to measure the frequencies of the first four resonances (R1-R4) for the non-periodic phonations, and broadband excitation at the mouth was used to measure them with similar precision in normal phonation. For resonances R1-R4, whispering raises the average resonant frequencies by 255 Hz with standard deviation 90 Hz, 115 + or - 105, 125 + or - 125, and 75 + or - 120 Hz, respectively. A simple one dimensional model of the vocal tract is presented and used to show how an effective glottal area can be estimated from shifts in resonance frequency measured during the same vocal gesture. Calculations suggest that the effective glottal area thus defined increases to 40 + or - 30 mm(2) during whispering. Creak phonation raised significantly only the first and third resonant frequencies, by 45 + or - 50 and 65 + or - 120 Hz respectively. It thus appears possible to use creak phonation to determine resonances with more precision than is available from the spectral envelope of voiced speech, and this supports its use in teaching resonance tuning to singers.