Sound waves(The behavior of soundboards)

[Ron Nossaman]

>After all this, you can tell me how blindingly obvious it is that the 
>fork moves the wire and the wire moves the bridge.
>
>JD

Run about 10 meters of music wire through your straightener. Make it #13,
or #22, as you wish. Lay an unstrung piano down on a skid on it's side and
lay the wire out on the floor so one end is propped up to touch the
soundboard. Apply the fork to the other end. An internal compression wave
in the wire shouldn't care at all what the wire sides are touching
(embedded in concrete, I believe was your description), so the fork sound
should come through loud and clear from the soundboard. If it is required
that the wire be moved by the fork to transmit "sound", nothing will be
heard from the soundboard. 

Recreate two sets your childhood cocoa tin phones, one with a 3 meter
length of light wire or strong sewing thread between and one with a 3 meter
length of 20mm diameter steel rod. A compression wave entering one end of
the steel rod from the cocoa tin bottom diaphragm should come out the other
end with the same volume as that produced by the string connected tins. If
the connection between tins must move to activate the "receiver", then you
won't hear much. 

Simple tests actually making an attempt to separate the two transmission
methods.

Yes, blindingly obvious.

PS: If the fork handle merely vibrates, but doesn't move, you shouldn't be
able to feel it bounce if you slowly touch the handle end of a ringing fork
to your front teeth, should you? And a fork clamped in a vise should pass
that compression wave right through the vise and sound from the bench top
as loudly as it does pressed directly to the top. Does it?

Blindingly obvious.

Ron N