Inharmonicity - so what?

[Delwin D Fandrich]

Jim Coleman, Sr. wrote:

> Hi Richard:
>
> The next time you rebuild a Grand, while the strings are off, hit the
> soundboard with a tympani mallet or even your fist. You will hear a resonant
> frequency around A1, B1 or C2. A large grand may have a resonant freq.
> as low as F#1 or maybe even lower. My Steinway L has a resonant freq. at B1
> with the strings on and up to pitch. When I worked at Baldwin, I would go
> around at night and give a fist test to all the pianos in 1st belly station.
> That's where the soundboards have just been glued in. The Concert grands
> had lower resonant freqs. than the small M's did. After stringing, the
> freq. is a little higher due to the loading and added stiffness.
>
> Jim Coleman, Sr.

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Jim, Richard, et al,

In the situation described by Jim you will get an indication of the resonant
frequency of what I call the "woofer" area of the board.  This is normally the
lowest frequency resonance of the soundboard assembly.  The fundamental resonant
frequency of the soundboard assembly will change quite a lot as you go up the
scale.  To get an idea of the specific resonant frequencies that will affect a
certain note along the scale, you will need to have the piano strung and at
pitch.  You will then have to drive the bridge at the point in question.
Soundboard resonance frequencies vary quite a lot at different points along the
bridge.

Del