Sound waves(The behavior of soundboards)

Charles Neuman piano@charlesneuman.net
Sat, 12 Jan 2002 19:19:25 -0500 (EST)


I've got some new goodies. Here are three quotes from three different
Scientific American articles. The last line of the last quote puts this
all into perspective.

Enjoy!

Charles



Frederick Saunders, "Physics and Music". Scientific American, July 1948.

"The sound of a violin is emitted not from the strings or the bow but from
its light wooden body. The contact between the strings and the body of a
violin is through the wooden bridge, which is cleverly cut to filter the
sound transmitted and remove some unpleasant squeaks. To produce loud
sounds, the violin body must satisfy three conditions. It must be strong,
light enough to be easily shaken, and big enough to push a lot of air
around when it moves. The sounding board of a piano must fulfill exactly
the same conditions." (p. 36)


Gabriel Weinreich, "The Coupled Motions of Piano Strings." Scientific
American, January 1979.

"The keyboard end of the string is fixed against an iron frame, whereas
the far end goes over a wood 'bridge' that is glued to the soundboard. The
bridge is not totally rigid because its function is to make the soundboard
vibrate synchronously with the string. Most of the sound is radiated into
the air from the soundboard, although it is also radiated to a lesser
degree from other parts of the piano. The vertical motion of the
soundboard turns out to have much more 'give' than the horizontal motion,
and so energy is easily transferred from the vertical motion of the string
to the vertical motion of the soundboard. This accounts for the faster
decay of the string's vertical motion, which is respondible for the prompt
sound." (p.120)


E. Donnell Blackham, "The Physics of the Piano". Scientific American,
December 1965.

"A part of the piano that has received a great deal of attention from
acoustical physicists is the soundboard. Some early investigators believed
the sound of the piano originated entirely in the soundboard and not in
the strings. We now know that the sound originates in the strings; after a
very short interval, called the attack time, it is translated by means of
a wooden bridge to the soundboard, from which is is radiated into the air.
During the attack time sound is also radiated to a lesser degree from both
the strings and the the bridge. In the late 19th century Frederick
Mathushek and his associates proved that the quality of a piano's sound
was not influenced by the transverse, or horizontal, vibrations of the
soundboard. They glued together two soundboards so that the grain of one
was at right angles to the grain of the other, thereby eliminating any
transverse vibrations, and found that the quality of the sound was not
affected by this arrangement. The behavior of the soundboard has also been
analyzed theoretically by a number of eminent physicists, including
Hermann von Helmholtz, but such analyses have added nothing to the
builders of the early clavichords and harpsichords." (p. 92)




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