Sound waves(The behavior of soundboards)

[Richard Brekne]

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Nice one Charles...

If I wasnt confused before I sure am now.... On the one hand there is by
Weinreich pretty clear message that vertical (transverse to the soundboard)
movement is real important.  Then in the third article this :

     " In the late 19th century FrederickMathushek and his associates
     proved that the quality of a piano's sound was not influenced by the
     transverse, or horizontal, vibrations of thesoundboard. 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. "


All over the place they refer to sound "radiation" ... you ever tried nailing
down just what physics people mean by this term ?.... great fun...:)

I aggree... about the last statement... as far as I can see anyways.

Thanks for the post.

RicB


Charles Neuman wrote:

> 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)

--
Richard Brekne
RPT, N.P.T.F.
Bergen, Norway
mailto:rbrekne@broadpark.no


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