Oops... Re: Unusual rib structure?

[Delwin D Fandrich]

----- 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