n the first, Jer Ming Chen (a postdoctoral researcher in this lab) sings his own tune, called Desert Lullaby. In the second, he sings up a harmonic series, starting at the fourth harmonic. No treatment of the recording. How does he do that? We'll need to start with some background first.
Whisper. In the first figure, a subject whispers the vowel in 'hoard'. We show the frequency response of the vocal tract (For an explanation of the measurements, follow this link.) The sound of the whisper itself is masked by the injected signal used to measure the vocal tract resonances. The figure shows several peaks, indicated by the arrows. At these frequencies, the sound produced at the vocal folds is most effectively transmitted as sound produced in the external air. (Technically, these are peaks in the acoustic impedance of the vocal tract. At these resonant frequencies, the tract operates most effectively as an impedance transformer between the relatively high acoustic impedance of the tract and the low impedance of the radiation field at the mouth.)