Modal Analysis (was Negative bearing (long))

[Phillip L Ford]

On Mon, 3 Dec 2001 23:36:00   
 Delwin D Fandrich wrote:
>
>OK. My previous answer was incomplete. But you're taking what I said out of context. What I said was, "One of the problems I have with most of the testing I have seen on the piano soundboard is that it was done on an unloaded board and is, therefore, largely meaningless." This is some different than you are implying above. It is my opinion that tests of this type are basically meaningless unless they are done on soundboards installed in a real world piano, strung and loaded. Remember, we're not just trying to figure out the specific characteristics of the soundboard alone, but the entire, interactive system. No where do I preclude the possibility of obtain useable results from pianos that are strung and at pitch.
>
>  Del
>
I'd like to put in my two cents worth if I may.  In my opinion what we should be hoping for from
modal analysis is a way of relating the behavior of the unloaded (and perhaps even uninstalled)
soundboard to its final behavior in the piano with the strings on it.  Understanding the built up
configuration is only part of the picture.  Until we can relate this back to design or construction
parameters for the piano itself then this information is interesting, but essentially useless.  But
if you can test and analyse  individual components and determine a way of relating their
behavior to the behavior of the whole then you can start to make changes to the components
that will affect performance of the whole.  Violin makers have been doing this for centuries.
Old makers spent years learning to feel top and back flexibilities that were necessary for the
completed violin to function well.  In our own time these flexibilities have been quantified 
through modal analysis and practical methods useful to the modern builder have been
developed to aid in the process so that he or she doesn't have to rely on years of 'getting the
right feel'.  Other parameters such as air modes, neck stiffness, etc. have also been quantified
and related to the performance of the completed instrument.  These are very useful tools
available to the modern violin maker.  The piano maker has no such tools.  Modal analysis is
one of the things holding some promise to provide us with these tools.  It would be a huge
research project but, as Del pointed out, a company which depends on piano sales for their
large income should be spending money on R & D and this is just the sort of thing they ought
to be spending it on.

Phil

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Phillip Ford
Piano Service & Restoration
1777 Yosemite Ave - 215
San Francisco, CA  94124