---------------------- multipart/alternative attachment Beware Gordon! Are you prepared to re-enter the mine field? You are about to start=20 talking about how the energy from the string actually becomes transformed=20 into the transversal movement of the soundboard, required to create the=20 sound waves we hear, forcing us to ask such questions like, for instance,=20 do the strings make the bridge move up and down, or, for that matter, from= =20 front to back? If you choose to undertake such an adventure, you would be= =20 probably be well advised to avoid starting out with a virtual sign taped to= =20 your rear saying "KICK ME!" By that I am referring to your portrayal of=20 the string pulling on the bridge cap. While I, personally have come to=20 believe that the essence of your idea is correct, that is, all modes of=20 string displacement being transformed into a kind of pulse energy at the=20 termination, the string would, in no way, actually pull on the bridge cap,= =20 with the attending implication that the bridge is pulled forward and=20 backwards, a motion you might more reasonably infer from a theoretical=20 configuration which had the entire string terminate on the bridge, (Of=20 course, in such an arrangement you would be dispensing with downbearing=20 ...but...). If anything, it would be the pins that would be pulled, but,=20 in that case, it would seem that the back scale would counteract any=20 tendency to pull forward. I'm not sure what aspect of Bernhard Stopper's remarks you are reacting=20 to. If anything, he seems to be saying, as are seem to be, that the bridge= =20 moves back and forth. I am doubting that such a description accurately=20 reflects the mechanics involved, but that's only my gut speaking. I have=20 to go back and read 5 Lectures again, along with the last 10 years of=20 Journals and Pianotech. David Skolnik At 07:49 PM 2/11/2004 -0800, you wrote: >Excuse me, please, but is not the piano tone actually >caused by the tugging of the string on the bridge cap, >effectively making it a "bell crank"? Afer all, as a >string vibrates, the end pulls in and out, not up and >down. If it waved up and down, lifting and dropping >the bridge with it, the tone we hear would be the >frequency of the entire string--- from agraffe to >hitch pin. But it isn't. > Thump >--- Bernhard Stopper <b98tu@t-online.de> wrote: > > Dear Marc & Isaac, > > > > Longitudinal waves of strings produce transversal > > vibrations on the > > soundboard caused by the bridge=B4s back and forth > > movement. If this would not > > be the case, one couldn=B4t measure or hear them. I > > think you don=B4t negociate > > that they exist, in the sound samples it is the > > whistle you can hear. As > > Isaac wrote, (he supposed it was the additional line > > below the 4. > > transversal but heard it an octave higher. It is > > overlaid with the 13. > > transveral, so that is indeed what you heard, (good > > ears Isaac, i am really > > impressed... ) > > > > Measuring and separation of transverse and > > longitudinal harmonics were done > > with a software spectrum analyzer (spectraplus, you > > can download a test > > version at http://www.telebyte.com/pioneer/ ). A > > spectrum analyzer extracts > > every frequency that is in a sound wave over time, > > no matter if it is caused > > by a longitudinal or a transversal wave. > > > > To interpert the spectra, just "count" the regular > > lines.. there are 39 > > transversal waves, and the first longitudinal wave > > (at about 712 Hz) is > > overlaid with the 13. transversal (a little thicker > > line) The various > > additional lines (mainly around the mid of the > > spectrum) are caused by the > > blank ends, the wave propagation is faster on that > > part of the string what > > results in splitting up several harmonics. > > > > to ask for a MiniMens Audio demo (the string > > simulator) and more information > > on the MiniMens program look here: > > > > http://www.piano-stopper.de/homepe.htm > > > > best regards, > > > > Bernhard Stopper > > > > ----- Original Message ----- > > From: "Mark Kinsler" <kinsler33@hotmail.com> > > To: <pianotech@ptg.org> > > Sent: Wednesday, February 11, 2004 6:09 AM > > Subject: longitudinal waves > > > > > > > So there's a program that'll simulate the behavior > > of a stretched string, > > > non-linearities and all? I suppose I shouldn't be > > surprised, but I'm > > > certainly impressed. And the recording and > > simulation sounded alike > > (though > > > the attack, etc. was different.) > > > > > > I'm sitting here wondering how you could measure > > longitudinal waves on a > > > string separately from the transverse waves. It's > > easy enough to detect > > > motion in a plane perpendicular to the string, but > > how would you isolate > > > longitudinal waves? > > > > > > I wish those two spectra had some labels on them. > > I couldn't figure them > > > out. > > > > > > > > > M Kinsler > > > 512 E Mulberry St. Lancaster, Ohio USA 43130 > > 740-687-6368 > > > http://home.earthlink.net/~mkinsler1 > > > > > > ---------------------- multipart/alternative attachment An HTML attachment was scrubbed... URL: https://www.moypiano.com/ptg/pianotech.php/attachments/88/6c/ea/28/attachment.htm ---------------------- multipart/alternative attachment--
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