Oops... Re: Unusual rib structure?

[Dave Smith]

Del, your description of modal analysis was lucid.  I did this kind of
research for the auto industry in the 1970-80's using Fourier Analyzers.
Since retiring I have forgotten more than I ever knew, most likely.  I had
assumed that this kind of research had already been done to exhaustion on
pianos, but have not searched for the technical papers.  Has modal analysis
been done systematically on pianos?  Is there any interest  in or
useful application for, this kind of information today?  I am not
volunteering, you understand, as I am trying very hard to become a competent
piano technician, and this would likely be a distraction.  But it would make
a good university graduate research project if not already done AND if it
was useful information.

Dave Smith
SW FL
www.davidsmithpiano.com
----
From: "Delwin D Fandrich" <pianobuilders@olynet.com>
To: "Pianotech" <pianotech@ptg.org>
Sent: Thursday, May 08, 2003 4:56 AM
Subject: Re: Oops... Re: Unusual rib structure?


>
> ----- 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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