[CAUT] Wire Stretch

[RicB]

Hi Michael

My calculations show that a change in string length due to a change in 
offset angles that would be caused if the string was caused to rise or 
be lowered on the bridge pins causes a clearly significant pitch change. 
To the the degree that poor seating can get into this picture I would 
have to disagree with you. As far as the span change isolated from what 
change might take place from offset angle lengths are concerned... I 
would tend to agree.. but then I havent sat down and calculated anything 
along these lines yet so I would hesitate to say for sure.

You raise the idea that the poorly seated string / loose bridge pin may 
cause an in phase movement that goes in all vibrational directions at 
once, causing the string to think it is longer then it is. Making the 
coupling more firm then would eliminate this in phase motion and 
actually raise the pitch of the string. Which kind of goes in the 
opposite direction as we experience when seating strings.

As far as the reaction given by Ron to all this in the direction of the 
loose bridge pins are related to false beats is concerned,  I have to 
respectfully disagree. For the first it has nothing to do with Micheals 
point at all. Secondly because well..  simply based on the fact that one 
can observe far to many exceptions in the case where loose pins and 
recessed edge are present.  When somebody can explain clearly to me why 
this condition can statistically be seen only as randomly associated 
with the occurrence of single string beats I will be insterested.  On 
another note... the horizontal mode as a <<proof>> for the loose pin 
idea is just too easy to dismiss. One can measure in phase movement in 
any direction... not just the horizontal.  It is when the assembly as a 
whole decides to fool the string into thinking its longer then it is 
that single string beats can occur.

I would also like to point out that just a week back I got a note from 
one of the most respected piano physicists in our world stating outright 
that  single string beat as relates to in-phase movement at the bridge 
must be seen in terms of the entire bridge / bridge pin assembly... and 
included in this the soundboard area immediately adjacent to the bridge 
foot.

Cheers
RicB

    It seems to me that any change in the length of the string because
    of poor
    seating on the bridge or  deformation of the bridge surface, would be
    insignificant.  However, that said, I believe that a poorly seated
    string
    coupled to the a loose bridge pin actually lowers the pitch because
    it is as
    if the pulse traveling along the string suddenly thinks that the
    bridge pin
    is part of the string and thus a longer string length.


    Michael Wathen
    -- 


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