False beats ....was M&A A

[Erwinspiano at aol.com]

The header should a been re titled a ways back  guys

.
Dale

 
IF YOU WANT TO KNOW THE TRUTH, STOP  HAVING OPINIONS!
 
 
In a message dated 02/20/07 02:04:30 Central Standard Time,  
ricb at pianostemmer.no writes:

  Hi Dave 

Jims Article was entitled "Unisons - The effect of tuning on  persistence 
and timbre"  September 1982

Dave, as Ric says above, the article is from...:-) (thanks Ric).

. 

Its a good read and it shows (I think) where the present idea  that the 
pin is the kind of support the article refers too in the  pendulum 
analogy, and that falseness is caused by horizontal movment of  same 
support.  Give it a read. 

My take is that, well aside  from the obvious observation that loose pins 
and the presence of false  beats do not occur simultaneously more then 
what can be called randomly,  the article just shows how a termination 
for an oscillating object can  alter the period of the object. A better 
interpretation to translate to  pianos IMHO would be to say that the 
bridge and pin assembly as a whole  can come to oscillate in phase with 
one (or more) frequencies of the  string and in one (or more) direction.

I would love to see some really carefully constructed experiments with  the 
right optics, metrics, etc. to see the movement of the string at a  point in 
its length as close to the bridge as possible with the  hypothesis that it is 
not only rotating transversely, but in small arcs of  rotation in the plane of 
the string plane as well because of the springiness  of the termination, and 
possibly cycloidal effect combined. I know that this  has longitudinal effect, 
and that this is an extension of Jim's  article. Birkett's high speed films 
show quite clearly, particularly the  bridge-end films, significant movement of 
the strings not only in and out  of phase, but right up to the pin, which I 
would dearly love to see more  closely. Some of these questions are not 
answerable by math alone but by  better observational technique, even though I've 
always believed that the  right question, properly asked, contains the best, if not 
 only, answer. In some man! ner, the principle of parsimony needs to work  
here better; there are too many factors possibly involved in the cause of real  
beats and we need to shave away the least likely.


This fits better with the more technical article in the 5 lectures,  and 
explains why loose pins can not be statistically associated with  false 
beats.  It also eliminates the whole problem with this  horizontal motion 
of the pin thing.

I agree, Ric. Can we yet shave loose pins from the "cause" plot?



Your comments relative to longitudinal modes are interesting,  and I see 
where you are going. Tho the longitudinal modes are very much  higher 
frequencies then the transverse we ultimately hear in much of the  
piano....especially where the classic false beat is usually a big  
problem... there is perhaps no reason why these could not create a false  
beat.... if and only if there are two horizontals at nearly the same  
frequency... and I dont think they function this way... but perhaps I am  
wrong.

I think maybe you're right. Particularly since we cannot correlate any  given 
longitudinal mode with a  "real" beat speed with any accuracy at  all. So 
statistically unlikely.



In anycase one is still confronted with some clear  observational data 
that as I mentioned cant be ignored. 

Cheers  
RicB 


Ric, Paul, & All - 
Shooting from the hip, so to speak. I've been accurately (but  
well-meaningly) chastised in the past for not actively  trying to find 
the answers to the questions I ask.  I'm coming to accept that 
answers are not my roll.  Perhaps something to aspire to.  In any 
case, I'll  pick through Ric's post below and refer to one item of 
Paul's.  For the sake of space, I'm deleting all but the specific  
quote, so it would be necessary for a reader to access the  original 
post to fully understand (if that ware possible)'  

At 06:41 AM 2/18/2007, you wrote: 
>Hi Paul. 
> 
> !  Jim  Ellis's article from way back. 
Can you better identify the  source? 





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