Coupled strings and pitch drop

[Jim Coleman, Sr.]

Hi Bob:

Did you also notice that the differences were more noticeable in the 5th 
and 6th octave as I did? Or did you find some other area where the 
difference was greater? How about note to note comparisons?

Jim Coleman, Sr.

On Tue, 10 Feb 1998, Robert Scott wrote:

> Ed Foote writes:
> 
> >    Could the unison, when allowed to sound, be causing more bridge movement,
> >thus causing the phenomenom of "longer than absolute length" come into play,
> >showing up as lower pitch?   
> >     Perhaps those that want to measure such things could find out if there is
> >a degree of flattening when two strings are compared to one?  And is this
> >greater or lesser than when the third string is allowed to sound.  
> 
> >( this seems like the sort of project that could use the RCT's
> >capabilities...??)
> 
> 
>  ....or the TuneLab's capabilities, for that matter.  I decided to use
> the TuneLab program to see if I could verify this pitch drop, and this
> is what I found.
> 
> I first selected some notes on a Kawai grand that were the most free of
> false beats so that a very precise pitch measurement could be made.
> Taking a hint from Jim Coleman, Sr.'s inharmonicity studies last year,
> I was very careful to standardize on how hard I hit the note.
> Then I tuned two strings of a unison (F#3) so that when sounded individually
> they each produced a totally stopped display.  Then I sounded the two 
> strings together.  There was a slightly noticeable drift to the left.  
> I had to adjust the offset about 0.4 cents flat to get the display to stop.
> I repeated this experiment for a number of other strings on the piano.
> The pitch flattening was anywhere from zero to .4 cents, depending on the
> note, but on most notes it was too small to measure.
> 
> Bob Scott
> Ann Arbor, Michigan
> Detroit-Windsor Chapter, PTG
> 
>