Inharmonicity - so what?

[Delwin D Fandrich]

Richard Moody wrote:

> Can differences in the fundamental resonance be noted with the dampers up
> or down?

Interesting question.  I suspect that the results would be the same, or at least
very similar, either way.  I've never tried a comparison, though.


> Also do you mean the fundamental of resonance freq. or the predomoninant
> resonant freq?

What I call the "fundamental resonance frequency" is what Jim is describing.
That is the sound -- the pitch -- you hear by "thumping" the piano soundboard.
You can also find this frequency by using the shaker method.  The soundboard has
many resonances.  Just like a piano string.  However, unlike a piano string, the
soundboard resonances are not necessarily harmonically related.  They are all
over the ballpark.  A Chladni map can illustrate at least the more predominate
of these resonances.  Smaller ones can be picked up using test equipment to
monitor the motion of the soundboard.

-- ddf


>
>
> ric
>
> ----------
> > From: Delwin D Fandrich <pianobuilders@olynet.com>
> > To: pianotech@ptg.org
> > Subject: Re: Inharmonicity - so what?
> > Date: Thursday, August 20, 1998 1:23 PM
> >
> >
> >
> > Richard Moody wrote:
> >
> > > ----------
> > > > From: Delwin D Fandrich <pianobuilders@olynet.com>
> > > > To: pianotech@ptg.org
> > > > Subject: Re: Inharmonicity - so what?
> > > > Date: Wednesday, August 19, 1998 1:54 AM
> > >
> > > >If the fundamental resonant frequency of the string loaded
> >soundboard
> > > assembly
> > >
> > > How is this freq determined?
> > > Ric
> >
> > -------------------------
> >
> > By driving the soundboard with a shaker.  A shaker is somewhat like a
> > loudspeaker motor assembly except that they are usually fully enclosed
> and they
> > have no cone.  Shakers are designed to transfer specific amounts of
> energy to
> > some mechanical structure.  The shaker is excited by a variable
> frequency sine
> > wave generator along with a power amplifier.  The frequency generator is
> swept
> > through an appropriate frequency band and the resonances noted.  These
> can be
> > detected either by ear -- sometimes confusing -- or by an accelerometer.
>  The
> > accelerometer output is analyzed with some type of signal readout.  The
> readout
> > can be anything from an accurate ac voltmeter, an oscilloscope or an FFT
> > analyzer.
> >
> > -- ddf
> >