Soundboards: Thickness and Area

[Richard Brekne]

I re-read this and think we need to back up a bit here.

Throwing sand on the soundboard and just smacking the bridge with a
hammer is not really how the process of displaying Chladni pattens is
accomplished to begin with. One uses a modal hammer to excite the panel
and read the results with a series of accelerometers so as to ascertain
the soundboards reasonant frequencies. But one doesnt create Chladni
patterns this way.

Chaladni patterns are created by exciting the panel to one of the
reasonant frequencies found, and you dont do that by just taking out a
plastic hammer and smacking the bridge with your hand. The lowest
reasonant frequency is usually around 50 hz or above and you are going
to have a good time hitting the panel with a hammer 50 times a second.

Aslo... The fundemental frequency mode pictures I have seen never follow
the edge pattern of the soundboard /rim. And it would be a bad thing
indeed if the fundemental mode was so large. I dont believe that
Steingræbers sand gathering proceedure has anything at all to do with
the fundemental reasonant mode... Lot of good a cutoff bar is if the
vibrational modes dont get affected (limited) by it ... or what ? 

Chaldni patterns have to do with the reasonant modes of a vibrating
panel. The edge conditions is another matter.

RicB

Richard Brekne wrote:
> 
> Delwin D Fandrich wrote:
> >
> >
> >
> > > No... Banging with a hammer or something on the bridge to see where sand
> > > gathers has nothing to do with Chladni patterns.
> > >
> > > Of course these are Chladni patterns. What do you think banging on the
> > soundboard with a hammer or something is doing?
> 
> The subject matter at hand is the gathering of sand around the edges of
> the piano. The Chladni patterns reflect the vibrational modes of the
> soundboard.
> 
> 
> 
> RicB
> 
> >
> > Striking an object with a carefully calibrated steel hammer is generally
> > how vibrating energy is set up in an object under test for a modal
> > analysis. It's then called a modal hammer and its price goes up by an order
> > or two of magnitude.
> >
> > Del
> >
> >
> --
> Richard Brekne
> RPT, N.P.T.F.
> UiB, Bergen, Norway
> mailto:rbrekne@broadpark.no
> http://home.broadpark.no/~rbrekne/ricmain.html
> http://www.hf.uib.no/grieg/personer/cv_RB.html
> _______________________________________________
> pianotech list info: https://www.moypiano.com/resources/#archives

-- 
Richard Brekne
RPT, N.P.T.F.
UiB, Bergen, Norway
mailto:rbrekne@broadpark.no
http://home.broadpark.no/~rbrekne/ricmain.html
http://www.hf.uib.no/grieg/personer/cv_RB.html