Ron Nossaman wrote: > >Ron,,, I took the up and down motion out of the picture by not letting it > >come in > >contact with the wood. > -------------------------------------------------------------------- > >The only thing new in this is the realization that the energy > >coming out the end apparently is stronger then the energy coming out the > sides, > >which is neat to know..... Perhaps because there are two waves fronts coming > >out of > >the side for every one coming out the bottom ? > > Here's where you dismissed the fork action. Where in the world does this > notion that energy leaks out the bottom of something without disturbing the > something come from? Especially since the energy is applied by moving mass. > Like the bridge, you aren't talking about waves leaking out the end here, > the entire fork moves. As the tines oscillate back and forth, they bend to > do so. Because they bend and deviate from being parallel to the length axis > of the fork, the overall length of the fork CHANGES as the tines vibrate. > The center of mass of the fork moves up and down with each cycle, which > means that the fork moves in space. The handle is physically moving up and > down. The entire handle. Well, perhaps... but that's not what the word elongation means. And that's the word used for the lengthwise motion by physicists. If my interpretation is wrong, then I suppose when I get to checking this out a bit closer, then there are a few things I will not see. 1 - I won't see for example that the wave amplitude is any less when "isolating" the sides from the bottom. 2- I won't see a 4 "rays" moving at 45 degree angles each where there is wave interference that results in almost no movement along these. > That includes the sides of the handle as well as > the bottom, which is why you eliminated nothing whatsoever by leaving the > bottom of the fork handle open in your demo. The fork is still pistonically > driving the board transversely. Maybe so... It seems easy enough to confirm this or not though given the expected patterns of the two different types of vibration would yield. > It's very simple and straightforward. There > is some side to side movement of the handle too, but that's the result of > the virtual physical impossibility of exactly matching the length, mass, > and spring rate of the two tines. The eventual side to side motion base on tine matching problems sounds reasonable enough, but as for the rest... perhaps it is straightforward... I could be making a mountain out of a molehill for sure... done that many times. But I will reserve my purchasing rights until I run the experiment again with some tools that will allow me to measure close enough what's going on. > > That is also why the sound produced by the fork on the tabletop is loudest > from the end of the handle, if you tried the experiment I asked you to. Er.... TILT ! :) That does not compute. Explain why your interpretation should result in the loudest sound when the end is touched to the table instead of the sides ? Why should the up and down pistonic action have any greater force when dependent on where its sapped from. I did the same thing in my Bending between the knees panel experiment, and the fork was very very tight in the hole in the one case, and hand held butt end on the surface in the other and I still get a the same differences in sound level. Another thing that bothers me about this... is why is it so easy to accept this the up and down motion of the handle when it is so difficult to accept the out ward and inward expansion /contraction of same along the sides. Actually as I think of it, if this second is true at all, then the first is not really up and down pistonic motion of the whole fork, rather it is the same kind of expansion, or... as Russells choice of the word "elongation" that is at work here. Interesting. I think actually I will contact the physics department here at the U and set up an experiment that should tell us what's what. If the wave pattern in the "knees" panel bears significant resemblance to the URL I sent you, then I will have to stick with my interpretation until something more likely shakes these old brain cells. If not, then the patterns in both cases will be very much alike. Should be easy enough to do actually. > > These are simple straightforward movements we're talking about here and in > the string, bridge, and soundboard, not radiating energy effects that > magically produce movement. It's actual physical movement. That's the > orientation part - basic physical reality. Yes... I understand that this is your position. And I grant that it may be so for all I know. But I think the above experiment will confirm or refute that one way or the other. > > >Actually, I think its time we all made a concerted effort to leave High School > >physics behind as much and as quickly as possible. > > I obviously disagree, since a very large portion of extremely elementary > established physics is being ignored altogether in this whole discussion of > soundboards, sound, waves, etc. An "education" or specific explanation that > doesn't correspond to observable and demonstrable fact is worse than > useless. That's supposed to be what scientific method is about, or am I > wrong there too? I don't know whether you are wrong or not to be honest.... In fact I think none of us are in a position to say. How can we judge whether elementary physics are being overlooked, or are just provide us with oversimplified explanation unless we are advanced enough in our physics knowledge to know for sure ? I think that's what's at issue really here... just how trustworthy is our present understanding of physics ? Is it really up to the job at hand here, or are we over estimating ourselves ? Or are we over estimating the difficulty of describing the system ? Again.. I am still not sure that any of this matters, above and beyond the academics of it all, for the everyday rebuilder and tech. But I am enjoying the process, and I thank all of you for pushing me in this most enjoyable (for me) direction. > > > >My table top experiment is incomplete. I have to verify that with an open > >air mic > >and a contact mic. And I don't think the forks action was really the point > with > >that one as the significant difference I pointed to was that of the case of > >listening to the open air sound, vs isolating (as best I could) the sound > >internal > >to the wood. > > Again discounting the fork motion from your conception of energy flow. When > something doesn't fit, take a step back and question your premise instead > of going deeper into ever more confusing layers of minutiae. It isn't > necessarily a matter of obtaining more education. You probably already > "know" too much that you haven't integrated into the physical world in any > meaningful way. That's why I asked you to think about it instead of looking > up something to think for you. > > >As I used the butt end of the fork in all cases in the table top experiment, > >the > >basic action and energy should be more or less constant. The difference in > >volume > >produced by the countertop seems obviously related to the wood orientation > >itself, > >though I will be a bit confused methinks if after putting a contact mic I > >find that > >there is very little difference in the amplitude when the fork is placed > on the > >side of the counter vs the top. Why THAT should result in a different > >relationship > >then listening open air will require some explanation I don't have at the > >moment. > >But I have to verify those results first. > > Of course the sound will be different from the edge of the tabletop than > from the top. That's why the experiment I asked you to do was all done on > exactly the same spot on the top of the table. Once with the end of the > fork handle, and twice with the side of the handle lying flat on the > tabletop. Have you tried this? > Yes... as well as I could with a ball ended fork. And I got the same kinds of results. I had to use the end of the counter instead of the top. I also mentioned I would borrow another fork to see. The experiment I mentioned above was with butt end all around and I was looking at the way the wood itself responds to wave input. We have three different experiments going at the same time here... :) hard to keep from mixing them up. > > Ron N Thanks muchly again. This thread has taken a decided turn in a very enjoyable direction if you all ask me. I do hope more of you all are actually trying out some of this stuff. Perhaps as Ron says,,, this is elementary, even so... RicB -- Richard Brekne RPT, N.P.T.F. Bergen, Norway mailto:rbrekne@broadpark.no http://home.broadpark.no/~rbrekne/ricmain.html
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