>OK. Question 1: "Wave energy moves the bridge". Under the bridge, >say the bass bridge, I arrange a massive trestle with thick metal >blocks pressing up against the underside of the bridge line, and on >top of the bridge I place a long lead weight as heavy as I can lift. >And if this isn't enough I borrow hydraulic equipment to make sure >that bridge really can't move. I haven't tried it, but you suggest >the effect will be to kill the bass of the piano as though the >soundboard and bridge were not there, since the loudspeaker effect of >the soundboard depends on the solenoid effect of the bridge. That should be the case. Just like clamping the driving coil of a speaker cone to the magnet. The transducer can't transduce if it can't move. >2. "Wave energy moves the bridge". What is wave energy and does it >travel primarily along the bridge surface as you say it moves >primarily along the soundboard surface? If it moves "along the >surface" does it travel in the varnish or in the air touching the >varnish or in the wood just under the varnish but no deeper, and how >does it travel? So far as I know sound travels always as a >compression wave through whatever medium, but you are suggesting >something different. But the soundboard isn't transmitting sound. It's dispersing string energy and producing sound. Transducing. >3. "travels primarily along the soundboard surface.....reflected back >into the soundboard panel." So the sound, I understand, begins its >journey moving _along_ the surface as far as the boundary and then >gets reflected _into_ the soundboard. How does it travel then? Like a ripple, with the stiffness of the transmission medium (soundboard assembly) determining the energy transfer rate from the string. It's the same kind of ripple that propagates along a struck string, and reflects from the terminations back into the string - only there are a whole lot more driving frequencies and excitation sites with the soundboard, so the ripple pattern is much more complex. It's not really a compression wave, though I'm not sure what it would be technically called other than a ripple. >What I suggest is that the sound does indeed travel _in_ and through >the beech and the spruce because otherwise it could not travel at all >except in air. I suggest also that the speed at which these >materials are able to carry the compression wave is elemental to >their choice for this purpose. As to exactly where in relation to >the surface(s) of the board it travels, I'd suggest it travels >wherever the medium exists to carry it and that it travels most >effectively in the hard and long-fibred winter growth. Then why does changing the rib height and feathering have so much more effect than thinning the panel? The long grain stiffness has more of a constrictive, than a transmission enhancing effect in practice. That's why floating the soundboard in the tail enhances the bass in a small piano so well. It relieves the built in excessive constriction of long grain stiffness, and shifts stiffness control to the ribs, where it is more manageable. Ron N
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