Whispering provides white noise that reveals vocal tract formants

Evidence

Another way to investigate the vocal tract resonances is to use white noise, an essentially disorganized superposition of sine waves at all frequencies. In effect, white noise allows us to perform all the different frequency investigations in parallel. In fact, we have a good white noise source already in place: in a whisper, the vocal folds are constricted but not vibrating; the rush of air past them causes turbulence and broadband noise (see chapter 14). Recording a whisper while various vowels are being pronounced, we can analyze the sound and look for the formants as resonance peaks with frequencies and widths. It is then a simple matter to take the ratio, Qn = fn/δfn, where fn is the frequency of the nth formant, and δfn is the full width at half maximum (FWHM) of the peak. The quality factors are not the same for different formants, because the effectiveness of the damping mechanisms may be different for different dispositions of the nodes and antinodes in the vocal tract. — Eric J. Heller, Why You Hear What You Hear- An…, 1673

Categorization

• QUESTION: Does whispering reveal the same formant frequencies as phonated vowels, or do the vocal fold state differences shift them?