At 8:09 AM -0600 12/21/01, Ron Nossaman wrote: > >The vision you and your co-thinkers have of the bodily movement of >>the bridge, not only up and down but also in a rocking motion, >>strikes me as completely absurd and impossible. Throughout this >>thread and previous related threads you have persistently poo-pooed >>any question of waves except the sort of wave or ripple that you >>associate with the ripples on the surface of a body. Similarly the >>only movement you seem to be able to comprehend is movement of a body >>as a whole. > >Once again, I understand your theory and disagree with it. It has been >acknowledged that there are also compression waves passing through the >system as well as progressive and stationary transverse waves. We've >already done this. I have never denied the existence of compression waves >in strings and soundboards. What I have said, and still say, is that they >are not the principal driver of the system. Once again, your response shows that you do not understand at all, since there has been no discussion in this thread of compression waves in the soundboard and the strings. What is under discussion is the waves that pass through the bridge. >by repeatedly avoiding my question of how small a bridge movement >constitutes no movement at all. You made a very big deal of stating >that a strung bridge couldn't be moved with a crowbar, so I think >it's only reasonable that you qualify this claim with a minimum >value of what constitutes movement. This is at the very core of your >theory, and I see no way that you can logically support this theory >without quantifying this claim. So let's have it and get this over >with. You talk of "my" theory as though I had dreamed it up out of thin air without any scientific evidence and as if I were claiming some novelty. On the contrary I have challenged you (in a part of my message you have avoided reproducing) to produce one serious URL, such as a University site, in support of what you are claiming. You ask "how small a bridge movement constitutes no movement at all" and the question is perfect nonsense. If there is some movement then there can't be no movement, but what is supposed to be the context of this meaningless question? You are claiming that the string bodily moves the bridge in such a way as to induce the soundboard to emit the sound appropriate to the string's vibrations and I say that it is impossible for this to happen. In your support Ron Overs piped up and said At 5:42 PM +1100 12/19/01, Overs Pianos wrote: > As the minute variations in the speaking length tension occur in >response to the string's position (at a given point in the cycle), >so too will there be a similar minute variation in the vector force >on the sound board panel. No one is claiming that there is no disturbance or stress at the meeting of the string with the bridge, otherwise no sound would be transmitted, but to claim that this disturbance results in the bodily movement of the bridge and drives the soundboard as a solenoid drives a loudspeaker is nonsense. That disturbance results in the _vibration_ of the bridge, which is the movement of a compression wave through the bridge during which every molecule of the bridge will be set in an oscillatory motion about its position of equilibrium. These vibrations will travel through the bridge in the same way whether or not the sum of the additional forces exerted by the vibrating strings on the bridge, whether laterally or vertically, amounts to zero as in an example I gave earlier in the thread. When you punch a dot in a huge lump of iron with a centre punch, the molecules at the point of the punch are so disturbed that not only does a compression wave travel through the iron but these molecules near the surface are permanently rearranged, and yet the lump of iron does not move. The energy at the point of the punch is sufficient to overcome the intermolecular forces at the surface and take a tiny part of the iron beyond its elastic limit. The remaining molecules simply oscillate about their position of equilibrium in the elastic medium. I take a 6 ft. rod of aluminium and press one end against the bridge of an upright piano. To the other end I hold a vibrating tuning fork. A compression wave passes along the material of the rod, continues in the same way through the bridge and causes the soundboard to emit the sound of the tuning fork. Your theory will announce that some sort of movement of the aluminium rod is responsible for this phenomenon and I say tell that to the marines! JD
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