Inharmonicity and humidity

Ken Jankura kenrpt@mail.cvn.net
Fri, 15 Jan 1999 10:30:26 -0500


At 12:03 PM 1/14/99 -0500, you wrote:
>>
>>  I believe inharmonicity is almost entirely a function of things
>>that go on in the string itself.  When the humidity changes as much
>>as you cited, the swelling or shrinking of the soundboard requires
>>a significant change in tuning pin rotation to maintain standard
>>pitch.  This in turn changes the termination point on the string
>>at the V-bar or agraffe.  If a small segment of string was
>>previously bent at the V-bar, but now is moved out into the
>>speaking length of the string because of tuning, that little
>>bend could certainly have an effect on the inharmonicity - even
>>if it was only 1/16" long.
>>
>>-Bob Scott
>>Ann Arbor, Michigan
>>
>>
>This  would mean that one could significantly change the inharmonicity by
>leveling the string, which experiment should be easy enough to repeat. This
>is a snow (actually an ice) day for me, so I will try this in my shop this
>afternoon, post ya later with results. Would raising a pitch 20 or 30 cents
>to effect this type of change be cheating? Changing it up and then down
again?
> Ken Jankura
> Newburg, PA
> 
On an old XYZ brand grand, restrung 7 years ago, I measured the difference
between 2nd and 4th partial of G4 ; 6.3. After leveling the string ; 6.5.
I raised the pitch 30 cts. ; 7.0. Leveled ; 6.3. Lowered 30 cts. below
pitch ; 7.2. Leveled ; 6.8.  No, it doesn't seem to make too much
difference, and you can make of these numbers what you will.  I tried a
couple other notes, and seemed to effect about a 1 cent diff by leveling,
which may point to the curvature of the bearing points as a partial (no pun
intended) cause of inharmonicity changes.
   Ken Jankura, RPT
  (Reschedule Land), PA
 
 


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