Hey there Östen, takk for sist ! a few comments below. Häggmark wrote: > > Richard writes > > 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? > Well that may be, but virtually everywhere I look, including the 5 lectures, the stated purpose of banging on the soundboard is to provide an excitement for all soundboard frequencies at once, which accelerometers placed about the bridge and board use to identify the vibrational mode frequencies of the assembly. And the stated method for finding the patterns is to exite the disired mode of the piano by vibrating the panel at the corresponding resonant frequency. If Udo Steingraæber is just defining the boarders of the fundemental mode to correspond so precisely to the outline of the rim, then I suppose it would be easy enough to find out by subjecting the panel to its lowest resonant frequency and see. Tho what reason one has for a cut off bar then that is so bypassed is a moment of confusion for me... grin.. certainly not the first. I havent seen every picuture of the fundemental mode for sure, but I've seen a good few, and none of them even came close to resembling this picuture. > > 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. Yes, most noteably right in front of the bridge. And I wish too he'd had time to go more into just what he was accomplishing. But to be sure, the sand collects at the places where the soundboard is not vibrating. > > 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". Yep... I remember him making a point of the importance around this area, and his statements to the effect that this had nothing to do with modal analysis in any form. > > 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... :-) We werent the only ones, that was quite the sustain and degree of clarity. He's doing something << right >> thats for sure. > > -- > Best regards, > Östen Häggmark, Stockholm Nice to see your name on the list again Östen. Cheers RicB -- 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
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