Changing Harmonicity

[Bernhard Stopper]

Hi Ric,

i know that soundboard impedance acts also upon inharmonicity. This is not
as complicated as it seems on the first look. The impedance acts as if the
string is a little more longer. (the soundboard becomes part of the string)
The formulas for this nonlinearity are well known. In the piano, the losses
in inharmonicity due to the soundboard impedance are more or less
negligible. This is a well known base nonlinearity phenomen in the physics
of damped waves. (Helmholtz described it already)

As like with the soundboard, during contact time, the hammer becomes part of
the string. But only for this short amount of time. A nonlinearity effect of
an ecxiter (hammer) to an oscillator (string) after the contact is off,
would be probably the discovery of a new law of nature.

regards,

Bernhard


----- Original Message ----- 
From: "Richard Brekne" <Richard.Brekne@grieg.uib.no>
To: "Pianotech" <pianotech@ptg.org>
Sent: Thursday, March 04, 2004 10:34 PM
Subject: Re: Changing Harmonicity


>
> Hi Bernhard
>
> I have to admit I'm on foggy ground here, not having read any much on
> the subject for a while and having little direct experience with this
> myself. But I remember we had quite a few discussions about the subject
> matter and that we (many of us) ended up differentiating between what is
> strictly <<string inharmonicity>> and the inharmonicity of the
> instrument as a whole. The soundboard assembly gets into the picture as
> well as hammer hardness/density... tho as I said I am hesitant to make
> any declarations as to specifics until I can re-dig up some of the
> articles and discussions. Tho I do believe things are a bit more
> complicated then just plain "string inharmonicity"
>
> Cheers
> RicB
>
>
>
>
>
> Bernhard Stopper wrote:
>
> > Hello Ric,
> >
> > All spectral measurements i have done on instruments with a spectrum
> > analysator haven´t shown any difference in the offsets of the
frequencies of
> > the spectrum. (of course the amplitudes for every frequency are strongly
> > affected by different hammers)
> >
> > If  there is a difference in the inharmonicity measured by the verituner
> > that differs with different hammer blows, it would be interesting to
know
> > how the verituner calculates the measured inharmonicity (what frequency
is
> > taken into account? what part of time is taken into account?).
> > It is knwon, that with very strong hammer blows the overall pitch raises
up
> > a little, but in that case all other frequencies are raised also, so
> > inharmonicity (the offset between them) is not affected. If the
verituner
> > calculates the inharmonicity by a match of frequencies to some reference
> > frequencies, there may be of course a difference in the result of its
> > measured values, caused by the (short) pitch raise.
> >
> > regards,
> > Bernhard
> >
> > ----- Original Message ----- 
> > From: "Richard Brekne" <Richard.Brekne@grieg.uib.no>
> > To: "Pianotech" <pianotech@ptg.org>
> > Sent: Thursday, March 04, 2004 11:44 AM
> > Subject: Re: Changing Harmonicity
> >
> >
> >
> >>Bernhard Stopper wrote:
> >>
> >>
> >>>I agree with Ron O.
> >>>
> >>>One should not confuse "Harmonicity" (what is not defined as a physical
> >>>parameter) with Inharmonicity.
> >>>Inharmonicity is definded as the offset of the harmonics by the effects
> >
> > of
> >
> >>>the stiffness of the string and is therefore not dependent of the
> >
> > hammer. It
> >
> >>>has nothing to do how "harmonic" impression that different hammers
> >
> > produce
> >
> >>>by enforcing or damping different partials.
> >>>
> >>>Bernhard Stopper
> >>>
> >>>
> >>>
> >>
> >>Defined such there is of course no argument, and Ron O is correct as
> >>Bernhard points out... by definition.
> >>
> >>Yet there is measureable divergence from this apparently having to do
> >>with the condition of the moment of excitement. That, if true, cant be
> >>overlooked either.... tho perhaps a definitions of terms are in order
> >>for any such discussion.
> >>
> >>Cheers
> >>RicB
> >>
> >>_______________________________________________
> >>pianotech list info: https://www.moypiano.com/resources/#archives
> >
> >
> > _______________________________________________
> > pianotech list info: https://www.moypiano.com/resources/#archives
> >
>
> _______________________________________________
> pianotech list info: https://www.moypiano.com/resources/#archives