Twas quoted (from an outside source) "SOUNDBOARDS, AND OLD WIVES' TALES There is no physical movement in the board, as you think of physical motion. " Of course nothing could be farther from the truth. Touch a soundboard and if you don't feel it moving I suppose no one is playing the piano. I suppose the penny on a soundboard rattling worse than a crack cannot be moving because there is "no physical movement of the board" The statement would be truer if it read, "as I think of physical motion. Longitudinal motion is associated with sound traveling in air, sound traveling through water, sound traveling through a sold. Transverse vibration is seen when strings vibrate up and down, causing soundboards to vibrate up and down at the same rate. The sb is a diaphram much like a speaker cone. As it moves it displaces air. This displacement is then longitudinal. It gets into mathematical realtion between the speed of sound, and the frequency and wave length of the particular periodic motion called sound. The string itself is moving no where near the speed of sound. (but I wonder how fast it does move?) but the sensation of tone we call pitch that we perceive comming from the string soundboard combination reaches our ears at the speed of sound. This is illustrated I think by McFerrin in Fig.1-2 p9. Now the way I understand it is that this motion of strings (transverse) produces longituditional motion (of air) that moves with the speed of sound. By the way he says on the same page that a longitudional wave can be produced in a piano string "by rubbing a piece of leather with powered (sic) rosin, then grasping the wire and pulling the leather lengthwise of the wire. A squealing noise or tone will be produced. Now I might challange that by way of experiment. If the "squealing tone" happens to be the same pitch as a tone produced by bowing and then again by striking then in this case what he is calling longitudional wave is not the same as what he describes below Fig 1-2. "these lines represent air particles compressed by some vibrating object atht e left which has given them a shove to the right." The explaination is much longer. It is possible a piano wire can vibrate longitudinally which I think rubbing with a rosin rag might cause, but this is not the same as longitudinal vibration as physists such as himself descibe. Or course what is actually happening in phyiscal reality is no way dependent or affected even by conceptualizations such as above. It is intellectual (well mental then) activity (effort?) to aid understanding. (whatever that is). But if it somehow will enable me to produce an instrument as good or better than a B then I will expend the effort. =-=ric "From a practical point of view the pianist or piano technician may consider that he needs to know little or nothing about the speed of waves traveling to and fro along the vibrationg string. However, it is well in any vocation to learn more than the minimum background knowledge about that vocation." ---W.V. McFerrin Formerely Associat Professor of Physics The colege of Emporia, Emporia, Kansas Craftsman Member of Piano Technician's Guild
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