longitudinal waves, MiniMens

[Bernhard Stopper]

Dear Gordon,

The string moves the bridge up and down (and and also back and forth) for
the transversal waves and mainly back and forth for the longitudinal waves.
This results from the direction of the apllied force on the bridge.
The waves are moving along the string and are reflected at the agraffe and
the bridge terminations. If the bridge termination had a nearly infinte
impedance (like at the agraffe in transversal direction), the waves would be
reflected at 100 % and you could hear nothing. Since the bridge has a finite
impedance (allowing the bridge to move together with the string a small
amount up and down and back and forth due to the strings force) the bridge
captures somewhat of the strings energy each time a wave arrives the bridge.
The mismatch of soundboard/string impedance describes how much energy
dissipation will occur over time. A lower bridge impedance produces a louder
sound, but the decay will be shorter then.

feel free to ask for a free  Demo Version of the MiniMens Software to study
string movement on my homepage:


 http://www.piano-stopper.de/homepe.htm

best regards,

Bernhard Stopper

----- Original Message ----- 
From: "gordon stelter" <lclgcnp@yahoo.com>
To: "Pianotech" <pianotech@ptg.org>
Sent: Thursday, February 12, 2004 4:49 AM
Subject: Re: longitudinal waves, MiniMens


> 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´s back and forth
> > movement. If this would not
> > be the case, one couldn´t measure or hear them. I
> > think you don´t 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
> > >
> > >
> >
> _________________________________________________________________
> > > Find great local high-speed Internet access value
> > at the MSN High-Speed
> > > Marketplace.
> >
> http://click.atdmt.com/AVE/go/onm00200360ave/direct/01/
> > >
> > > _______________________________________________
> > > pianotech list info:
> > https://www.moypiano.com/resources/#archives
> >
> > _______________________________________________
> > pianotech list info:
> https://www.moypiano.com/resources/#archives
>
>
> __________________________________
> Do you Yahoo!?
> Yahoo! Finance: Get your refund fast by filing online.
> http://taxes.yahoo.com/filing.html
> _______________________________________________
> pianotech list info: https://www.moypiano.com/resources/#archives