Sound waves(The behavior of soundboards)

[Richard Brekne]

I found this article that has a several basic definitions and some good illustrations.
Amoung them right at the start of the article a good illustration of a transverse wave
in solids. This illustration along with some descriptions I have recieved recently from
a few kind souls satisfy one of the problems I was having with this transverse wave
explanation.

http://www.geology.uiuc.edu/~hsui/classes/geo351/LectureNotes/waves.pdf

It is desecribed to me as a transverse bending wave. As the wave propgates through the
wood this  bending stretches the fibres of the soundboard on the convex side and
compresses the fibres on the opposite side.  This compression and stretching of fibres
alternates with the frequency of the fundamental (of the string). The wave itself
however, is not a compression wave.

This is not at all far removed from the clothsline illustration, though I get a
different picture then one of surface ripples and little or nothing happening in the
middle of the wood.  This description satisfies nicely the difficulty I was having
concerning the 3 dimensionality of the wood. I couldnt see how any wave could fail to
travel through the full thickness of the wood  horizontally.  And of course they do.

This leaves me still wondering about how all the strings partials end up driving the
sound of the board, but I suppose I might get a further description to that as well at
some point.


--
Richard Brekne
RPT, N.P.T.F.
Bergen, Norway
mailto:rbrekne@broadpark.no
http://home.broadpark.no/~rbrekne/ricmain.html