Sound waves(The behavior of soundboards)

[Richard Brekne]

---------------------- multipart/alternative attachment
Transducer

Hi Ron

I see you've found CCRMA at Stanford. Neat resource eh, but a kelp forest of a
place to navigate through. Still, I have been traversing their nett links more
then once.  Might be wise to put this page-long quote into some perceptive as
its in reference to modeling systems for musical instruments. That being said
the this more or less agrees with other things I have run into.

I understand the key phrase here being

     "When a traveling wave reflects from the bridge of a real stringed
     instrument, the bridge moves, transmitting sound energy into the
     instrument body"


I for one have taken much less issue with the whole motion thing per se then I
have spent time looking into just what it is that constitutes this motion.
Ergo I still seem to be sitting in the middle of this discussion arguing
"apparently" against motion with you, and for it with JD.   (Definition for
Transmit included below)

Something I found of interest is a comment by Olson in his book which states
that at the termination points of strings in musical instruments represent
nodes. And we all know the "motionless" characteristic of modes.

Clearly its not as simple when it comes right down to it as simply waving a
stick at someone, (not that that isn't in reality complicated enough if you
want to get into it) On the other hand, as I have stated several times, I
still see no real earth shaking implications these differing perspectives (if
that's what all this indeed boils down to in the end) have relative to design
issues.... yet, though I have pondered about about how all this fits into the
idea that rims and cases do not play any part in sound radiation or how, if
they do this could be a design issue for some factories.

Another thing you might find neat is the idea that the set of strings can be
viewed as a 2 dimensional plate with its own set of wave impedance modes, as
contrasted to the single dimension modes of a single string. This 2
dimensional perspective of the whole scale can be used feasibly as part of an
alternative way of designing a scale.  This thought is presented in Benades
book. The gist is that such a plane then would interact with the sound board
modes in such a way that the problems relating to resonance modes of the sound
board can be manipulated to some degree.

Last but not least... I clicked on that link to "dashpot" at the link you
provided (wondering what on earth that was) and look what comes up.

     "The elementary impedance element in mechanics is the dashpot which
     may be approximated mechanically by a plunger in a cylinder of air
     or liquid, analogous to a shock absorber for a car."

There we have that "pump" like picture presented again, even a "motion
absorption" picture. The bridge then is loosely compared to a shock absorber
this link you provide... and shock absorbers deal very very much in
compression waves.... or what ?

Ron Nossaman wrote:

> http://www-ccrma.stanford.edu/~jos/waveguide/Dynamic_Terminations.html
>
>
> Ron N

Nice link. Me likes.


Definintions
  Transmit   Physics.  1. to cause light, sound, heat, or another form of
energy to
  pass through a medium.to cause light, sound, heat, or another form of energy
to
  pass through a medium. 2. to convey force or motion from one part of a body
or
  mechanism to another.to convey force or motion from one part of a body or
  mechanism to another. 3. to allow the passing through of a form of energy;
to
  conduct.to allow the passing through of a form of energy; to
  conduct.


--
Richard Brekne
RPT, N.P.T.F.
Bergen, Norway
mailto:rbrekne@broadpark.no


---------------------- multipart/alternative attachment
An HTML attachment was scrubbed...
URL: https://www.moypiano.com/ptg/pianotech.php/attachments/5a/cf/c1/1f/attachment.htm

---------------------- multipart/alternative attachment--