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>A year or two ago when I was doing some research on sound exhibits I
>ran across a place that had different shaped metal plates that
>visitors would place sand on top and "play" with a bow.  I believe
>this would show vibration patterns in the sand.  Does anyone know
>what I am talking about and where I might get some information on
>building an exhibit like this?

What you saw was an exhibit version of the classic physics
demonstration/experiment setup of Chladni plates.  Try googling
"chladni plate" to find out more such as the information in the
following url's:
http://astronomy.swin.edu.au/~pbourke/modelling/chladni/
http://faraday.physics.uiowa.edu/acoust/3D40.30.htm

To get information about building something similar, in addition to
the "Bells" recipe in the Exploratorium Cookbook I, you could try
contacting your local university physics department and see if they
are able to offer advice and assistance.
--
Claire Pillsbury

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