Talk:Vibrating string
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Copied by me--Light current 22:48, 12 May 2006 (UTC)
This post of mine has been sitting on the Talk:Bridge (instrument) page for about 5 months with no replies. As we seem to have some very educated editors working on this page 8-), I thought some of you would like to comment.
Bearing in mind that there is a node on a vibrating string where it passes over the bridge, how exactly do vibrations get to the body. There arent any vibrations at the bridge cos its a node. Anyone know the answer to this paradox? 8-?--Light current 14:42, 12 November 2005 (UTC) --Light current 18:38, 1 May 2006 (UTC)
- Resonance, I guess...--Army1987 13:09, 13 May 2006 (UTC)
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- Saying there is a node at each end of a string is a simplification. It would be true if the ends of the string were attached to something perfectly rigid, but they're not. The whole instrument is vibrating, including the bridge. Pfalstad 14:10, 13 May 2006 (UTC)
Yes I agree Paul. But can you propose a mechanism for transfer of the string vibrations to the body of the instrument that fits the obervations? 8-)--Light current 14:16, 13 May 2006 (UTC)
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- Do we agree that the end of the string is moving (not perfectly a node)? Well then, the string moves the bridge, and that moves the body... Pfalstad 14:25, 13 May 2006 (UTC)
Yes, but in which direction does it move the bridge-- up and down, back and forth, side to side, or some combination of all three?--Light current 14:29, 13 May 2006 (UTC)
Yes. I think I ve seen this one before.8-) This implies that its the up and down motion of the string that gets trasmitted to the belly. If this is true, it must mean that the 'side to side' vibrations of the string are somehow changed into 'up and down' vibrations. However, I have seen another expalnation that talks of the bridge being rocked back and forth (in a direction // to strings) thus tending to bend the belly slightly and transmit vibrations that way. BTW do you know the reasons for the peculiar shaped cutouts in the violin bridge?
Also, one thing I ve been wondering about is, when you have a vibrating string, set at a nominal tension T newtons say, then when the string is set into vibration, does the instantanoeous string tension change and could this be detected at the 'fixed' points (nut or bridge). The analysis on the page assumes that the tension is constant, but I bet it aint! 8-? In fact its obvious from the analysis that the string tension varies during the vibration cycle of the string. So, the answer to my question appears to be that these changes in tension should be able to be picked up by load cells measuning the tension. Now the more important question is: Are these tension changes the primary means of energy transmission to the bridge. If not, what other mechanisms are involved?--Light current 15:36, 13 May 2006 (UTC)
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- That's not the way I read it. It seems that both side-to-side and up-and-down motions will get transmitted. I have another reference which says that the bridge moves in many different ways. Pfalstad 19:18, 13 May 2006 (UTC)
- The analysis on the page is very weird. I've seen other analyses that make more sense, and they say that they are making many assumptions, including assuming the tension is constant, but I don't think it is. My guess is that this is the primary means of energy transmission. I'll check my reference to see if it says more. (It's a very technical reference so I had trouble finding good quotes in it, but I'l check again.) Pfalstad 19:18, 13 May 2006 (UTC)
THanks. I look forward to seeing what your book says.8-)--Light current 19:21, 13 May 2006 (UTC)
'The physics of wind instruments?' Are there any articles on how wind instruments, or their reeds, work? Or does someone know about books on the matter (I have learned physics so it is OK for the books to be academical) so I can maybe write one? --Satúrnus 20:26, 11 December 2006 (UTC)
