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Hello Friends,
I'm sure most of you are familiar with the Chladni patterns. Placing sand on a soundboard and inputing a tone to create a pattern in the sand so you can see the nodes etc. I guess I just don't get it. How is that useful?

'Dunno. I thought it was just supposed to be an artistic curiosity.

Any Luthiers out there?

In the days before spectrum analyzers-the sand would tell you when you found a resonant frequency as you sweep the driver up from the lowest starting point.

So was it a quality control thing then?

Still done by Steingraeber in Bayreuth. They use it before the board is lacquered, probably to see the frequency response of the board, allowing to plane it more on some edges may be.
It shows the resiliency of the panel edges. And more, certainly.

The chladni patterns have been superceded by electronic speckle pattern interferometers, and more recently, laser Doppler vibrometers. Numerous bits of information can be gleened by using these methods. If your into a technical read with some cool photos, this should satiate you..

http://www.csc.kth.se/utbildning/kth/kurser/DT2212/Piano%20Moore%20et%20al%20JASA

Great study, Emmery, thanks, will read it with a little time at hand.
It may be useful to know for the study we like to setup, if the Iraq is serious.

We need a setup to visualise /record coupling, in quantity and plane orientation. (string by string of course, or may be differentiating couples may be enough)

Accelerometers are very difficult to setup to do do (installation on a vibrating element to discern a sub elemrnt) and they also have some mass, even if minimal.

Cost may also be a problem to the lab, if too expensive material is to be bought /loaned (?).

Ideas?

Laser Doppler vibrometers are expensive to buy but there are a couple companies in N.A. who rent them out for reasonable rates, many university physics labs take advantage of this for short studies.