Changing Inharmonicity

[baoli liu]

Hi List,

Roger has a good explanation about the hammer,I'd like
to mention three factors for this topic.

1. termination--the bridge will expand or shrink when
the humidityy changes,while the bridge pin remains
stable.the brass-made bridge pin are ususlly "cut" or
"copressed" by harder strings, this will cause the
variation of the termination and results in
inharmonicity(including the fundamental) change.

2. soundboard-- soundboard has its own vibration
modes(just like the partials of the string),and this
modes are certainly influenced by the humidity.
Just assuming that the frequency of one mode of the
board is very close to that of one partial of the
string.when the frequency of the mode is a little
higher,this partial will be accelerated by this
mode,if the same mode becomes a little lower than that
of the partial due to humidity change,the frequency of
the partial will be lowered also.

Hammer --play harder,the string will vibrate in a
larger amplitude,this may cause higher partials and
higher fundamental.

Baoli Liu
University of Wisconsin-Madison 



--- jolly roger <baldyam@sk.sympatico.ca> wrote:
>  
> >So what really happened here?  I don't remember the
> conversation following
> the
> >demonstration, but I am assuming the steam
> rearranged the strength of the
> >partials.  Roger may wish to comment.
> >
> >Regards,
> >Clyde Hollinger, RPT
> 
> Hi Clyde,
>                The voicing changes the pitch of the
> partials,  hence the
> beat.  This is clear and easy to hear.   Now the
> voicing changes the
> elasticity of the hammer and hence the dwell time. (
> length of time the
> hammer is on the string, and how the harmonics
> develop.)
> Oleg is also correct, even blows will also have an
> effect. Since dwell time
> is also effected.   Now enter the weather,  the
> hammer swellls and shrinks,
> with humidity changes
> Changing FAC numbers is very sensitive to, weather
> changes, and felt
> compression on a well used piano.
> At a guess, I think the changes are more due to
> humidity and hammer
> hardness changes, than board changes.
> One way to get an indication.  Sample FAC. (don't
> play the piano for a
> month)  Re sample again after a large humidity
> swing.
> I have done test where the pitch was the same, and
> the notes were struck
> with a constant velocity and mass device.  Cjhanges
> occur.   But from
> what??????   The sampler?  Just the felt? The board?
> The bearing? The SAT?
> Or all of the above?
> I suspect all of the above.  No answers just
> rambling thoughts.
> 
> Roger
> 
> 


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