Piano acoustics

[Richard Moody]

I have no doubt you are measuring differences of inharmonicity.  However it
would be interesting to know how accurate these measurements are.   There
are several ways to test this.   Using one machine take at least 5
measurements of inharmonicity in say 5 minutes and compare the differences.
If this machine is consistant within an agreeable range then it would be
interesting to compare 3 machines to 5 measurements in 5 minutes.  If these
machines are consistant then a comparison of a string vibrating between two
solid termini with no sound board against the same string in an acoustic
piano could be taken as reliable.
    If the machines are not consistant with inharmomicity readings then
they could be compared to reading the fundamental of  a sound or tone
source such quartz digital instrument, or the shortwave broadcasts.  An
experiment with one ETD yielded wild results in FAC type measurements, but
no detectible differences between repeated measurements of an audio tone
(fundamental) from an electronic digital source.  ( a Korg Digital Tuner
DT-1 from about 1987).  From that I conclude the ETD, (a share ware version
of TuneLab97) and the Korg are extemely stable in producing and detecting
the fundamental.   ---ric


----- Original Message -----
From: Don <pianotuna@accesscomm.ca>
To: <pianotech@ptg.org>
Sent: Tuesday, February 05, 2002 10:49 AM
Subject: Re: Piano acoustics


| Hi JD,
|
| How else could a string exhibit negative inharmonicity other than through
| coupling to the bridge/soundboard/plate? Direct measurement shows that
| negative inharmonicity does exist. It just doesn't happen very often.
|
| Also humidity levels affect inharmonicity--and last time I checked steel
is
| not affected by moisture in any way except that it will rust if the
| moisture level is too high. Therefore I conclude that inharmonicity *is*
| affected by the bridge/soundboard (and possibly the plate as well)
|
| It may also be affected by the hardness of the hammer--though I don't
have
| any measurements to confirm that. I suspect that the changes that Roger
| Jolly did at conventions were a change in the amplitude of a particular
| partial making an octave "out of tune" because a different partial was
| louder. That would not necessarily indicate a change in inharmonicity.
|
| Inharmonicity is also changed by "setting" the strings and bridge pins.
|
| The authority I quote for the above statements are my own direct
| measurements before and after and the history in my database of FAC
numbers
| over many years and changes of season.
|