The Human Instrument; January 2008; Scientific American Magazine; by Ingo R. Titze; 8 Page(s)

The human vocal system would not receive much acclaim if instrument makers placed it in a lineup of traditional orchestral instruments. Arranged by size, for example, the voice box (larynx)--and the airway it sits in--would be grouped with the piccolo, among the smallest of mechanical music makers. And yet experienced singers compete well with all man-made instruments, one on one and even paired with full orchestras. Recent investigations of how our singing voice generates a remarkable range of sounds have revealed surprising complexity in the behavior of the vocal system's elements and in the ways they interact.

For more than half a century, scientists explained the voice's ability to create song by invoking a so-called linear theory of speech acoustics, whereby the source of sound and the resonator of sound (or amplifier) work independently [see "The Acoustics of the Singing Voice," by Johan Sundberg; Scientific American, March 1977]. Researchers have now learned, however, that nonlinear interactions--those in which source and resonator feed off each other--play an unexpectedly crucial role in generating human sound. Such insights now make it possible to describe how great singers produce those amazing sounds.