longitudinal waves, MiniMens

[Bernhard Stopper]

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
>
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