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January 23, 2008

The Human Instrument

Scientific American:

When judged by its size, our vocal system fails to impress as a musical instrument. How then can singers produce all those remarkable sounds?


- Although the human vocal system is small, it manages to create sounds as varied and beautiful as those produced by a variety of musical instruments.

- All instruments have a sound source, a resonator that reinforces the basic sound and a radiator that transmits the sound to listeners.

- A human’s sound source is the vibrating vocal folds of the larynx; the resonator is the sound-boosting airway above the larynx; and the radiator is the opening at the mouth.

- The human voice can create such an impressive array of sounds because it relies on non­linear effects, in which small inputs yield surprisingly large outputs.

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. 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.

This long and very interesting article by Ingo R. Titze continues here.

Posted by acapnews at January 23, 2008 12:06 AM


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