----- Original Message ----- From: "Greg Newell" <gnewell@ameritech.net> To: "Pianotech" <pianotech@ptg.org> Sent: May 07, 2003 8:25 PM Subject: Re: Oops... Re: Unusual rib structure? Del, Can this type of modal experiment be reproduced? and if so, how? Greg Newell -------------------- Sure. In fact it would be much easier today than it was then--computers are much faster and the software is much more sophisticated. All you need is a piano with a suitable soundboard set up so you have access to the soundboard at specific intervals. As I recall we used a grid of approximately 3" spread across the board. If you want the results to be meaningful this means that the piano must be strung. Yes, you want to get to all parts of the soundboard so that means drilling some holes through the plate. You mount a suitable accelerometer on the bridge at some suitable location. Using a Modal Hammer (i.e., a hammer of known mass and with an accelerometer and a force transducer on its striking surface) you tap the soundboard at each grid point with as much consistency as possible. Once all the data from these hammer impacts has been recorded you process the whole thing through some very expensive Modal Analysis software. For your trouble you will get a picture of the soundboard panel vibrating in slow motion at whatever frequency or frequencies you desire. Then, of course, you have to interpret what you see. Interesting stuff. But pricey and time consuming. Del
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