Soundboards: Thickness and Area

[Östen Häggmark]

Hello Richard,

(and hello Kjell Sverre!)

Since I also was there at that last lecture of the last
day... :-)

> 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.

I always thought that knocking at the soundboard would make
it resonate at something like the fundamental resonance
frequency? Mr Fandrich called it a "broadband impulse tone
generator" I believe?

> Aslo... The fundemental frequency mode pictures I have
> seen never follow the edge pattern of the soundboard /rim.

I think that the pictures shown at the lecture showed areas
well away from the rim that "contained sand" and I seem to
remember that they were indicated by Udo Steingraeber as
noteworthy.

But you are right that the objective of the described
practice was not modal analysis as such. As Udo
Steingraeber stated, "that's in the design process".

This practice as I understood it was instead used in the
production process as a way of indicating stiff areas, or
maybe rather points, close to the the rim/soundboard
connection, with special care taken to the area in the upper
treble where the bridge closes in to the belly rail (right
word?), a.k.a. the "killer octave".

And a thing I think we both noticed, Richard, was the strikingly
long and singing sound of the upper treble part of the
Steingraeber grands at hand at the Treff. Who knows... :-)


-- 
Best regards,
 Östen Häggmark, Stockholm