Hi Gordon :) I really dont think anyone knows for sure just how exactly all this works... tho there are plenty out there who are pretty darned sure they do. Funny how so many of these dissagree fundementally on the subject as well. We have a professor of acoustics from Purdue who recently revealed a thesis in which longitudianal wave motion through the soundboard was finally <<proved>>. We have others who dissagree with his conclusions, and of those there is often dissagreement as to what they think is going on. My own perspective... unschooled as it is, is that in principle... all wave action is longitudinal in nature. Transverse and hybrid wave behaviour only occur when a wave form traveling through one medium encounters another. Some of the wave energy then is reflected, some absorbed and given off as heat or some other waste product, and some simply passes through. The apparent vibration of the more solid medium is simply a partial image of the transition from one medium to the other that is taking place. Many will have it today that the soundboard simply acts like a diaphragm, moving up and downwards only, experiencing no internal longitudinal action, or whatever there is does not influence the transverse output that sets air in motion. I simply cannot see how this can be in the first place. Since it is indeed only one wave we are really looking at... but broken into componet parts... that part which intereacts with the air medium, that part that stays internal, and that part which is transformed into some other product,... these must be all interedependant with each other. Any longitudinal motion and frequencies which necessarilly must be present is then very much an influencing factor on the transverse interaction with the air... because really these two are one in the same.... part of a whole. Same thing really goes for the string... it is a medium which interacts with at least three others. The air, the bridge, and the front termination. It will neccessarilly have both transverse and longitudnial motion when excited, and all this motion / energy will be transfered and reflected back from to some degree or another to the other three... which in turn do their bit in similiar fashion. I hadnt thought about the <<leverage>> a string exerts on the bridge as such. Dont remember it being brought up before either... tho perhaps it has been. Anyone have any comments on that ? Cheers RicB gordon stelter wrote: >It seems to me that energy is transferred to the board >from the string via "bell-crank" motion, NOT the >direct waving of the board ( heavy and stiff ) by the >string ( light and flexible). As the string >oscillates it expands and contracts in lenghth, and it >is this motion, yanking the top surface of the bridge >for and aft, that is transmitted into an up-and-down >motion of the board near the bridge >( alternately adjacent to its sides ) and these >vibrations are then sent rippling along the grain to >the rest of the board surface. > Therefore, could it be that increased bearing >mainly improves the mechanical advantage, via >leverage, that the string has in tranfessing its >motion to this most immediate portion of the board, >and that this is as ( or more ? ) important than any >increased stiffness to to compression? > If my theory is correct, then bridge height would >probably also be a significant factor in tone, as it >would also have marked effect on the mechanical >advantage the string has as it vibrates. > Has anyone studied the effect of bridge height on >tone, all else being equal? > Thump > > > >
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