At 12:40 PM -0600 12/19/01, Ron Nossaman wrote: >Ok John, I answered your questions again. Now how about you answering mine? >We're still holding at two, listed according to age. > >1. How minute does a movement have to be to be nonexistent? That seems to be a metaphysical question, but I'll answer the question you seem to mean. You have talked from the beginning of the bridge rocking and moving up and down and Del and Ron Overs apparently share your view of these matters. From what all of you have said at various times in this thread and in previous threads, including that on longitudinal waves, I get an increasingly clear impression of your concerted view, and many details of this view make no sense to me at all. In order for a body to move, a force needs to be applied (Newton's first law?). If I take a 2" x 2" x 12" steel bar, lay it on a surface and tap the end with a light hammer, the bar will not move because the applied force is less than the limiting friction. If I hit it with a larger hammer, the bar will move. In both cases the whole bar will vibrate and the sound wave will spread throughout the bar. >2. Why doesn't touching the fork to the edge of the soundboard not produce >the same tone as touching it to the top if it's compression wave driven? Well, apart from the extreme difficulty I have in picturing how you would set up a valid test for this, it is no doubt possible to test. One would need to make sure that the impedance at each test point was identical to start with and that would mean dressing the edge with something. You've obviously made such an experiment so how did you set it up and what did you discover? But I think you are missing something. The vibration or compression wave that I claim in my theory to pass from the string termination through the bridge to the soundboard reaches the soundboard in such a direction as to induce transverse vibrations in the soundboard. That has never been at issue. There are certainly compression waves in the board as well but these are secondary and would lead to a rather fruitless discussion at this stage. It is obvious that if one holds the tuning fork against the edge of the board, the board is being induced to vibrate at 180 degrees to the surface and there is no direct stimulus to cause it to vibrate transversally, though in the nature of things a small proportion of the vibration will excite a degree of transverse vibration. The difference between us is that I see the movement of the soundboard as the result of vibrations passing through the bridge to "hit" it at a right angle and shake it up and down, whereas you see the whole bridge as moving and rocking and what not and shaking the board. The bridge certainly does move bodily once the soundboard has received the energy to cause it to vibrate, but according to your theory it is the bodily movement of the bridge that pushes and pulls the soundboard up and down. The more arguments you and the others give in support of this theory, the more incredible it seems to me. JD
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