[CAUT] Re. Link to Young Paper

[Jim Busby]

Hi Fred,

 

At a convention someone mentioned this as "the" way one should take the
FAC measurements. Wasn't this in the journal once too? I'm still unclear
as to the "step by step" instructions. (1, 2, 3...) For the gadget
impaired, (me) would you give those instructions???

 

Thanks,

Jim Busby

 

________________________________

From: caut-bounces at ptg.org [mailto:caut-bounces at ptg.org] On Behalf Of
Fred Sturm
Sent: Friday, January 19, 2007 4:47 PM
To: caut
Subject: Re: [CAUT] Re. Link to Young Paper

 

On 1/19/07 3:29 PM, "David Brown" <David.C.Brown.2 at asu.edu> wrote:

Dear Fred-

I wonder if you could expand on this a bit more. I attempted to
calculate FAC this way after reading your post but I must have done
something wrong. The difference between the first and fourth partial of
A4 seemed to yield a wider octave ( larger A number, to be expected I
suppose) than the normal reading,  but the difference between the first
and fourth partial of C 6 yielded numbers well into the 20's or 30's! I
tried the the difference between the first and second partial of C7 as
well and still no real usable numbers for me. There must be a way to
enlighten me! 


Hope all is well in New Mexico.

Regards-

David


Hi David,
    The A4/A6 difference needs to be multiplied by 0.8, to factor out
the difference between 1st and 2nd partial and leave the difference
between 2nd and 4th partial. The C6/C8 difference needs to be multiplied
by 0.2 to factor out the difference between 2nd and 4th partial and
leave the difference between 1st and 2nd partial. The difference between
1st and second partial is 1/4 the difference between 2nd and 4th partial
(it's a logarithmic scale, based on a square of the difference between
partial numbers, kind of).
    So, if you read A4/A6 as 10 (zero A4 and read its 4th partial at A6
as plus 10 cents), you enter 8 as the A number. When you have calculated
the tuning, the number for A4 (the tuning offset, tuning it's 4th
partial) will be 10. For C6/C8, if the number is 35 (C6 zeroed, its 4th
partial at C8 read as plus 35 cents), you enter 7. (Obviously when you
enter the number, you have to go to the right note name and octave, and
scroll cents up or down).
    Is this clearer? 
    (BTW, David is referring, I believe, to some posts I sent to
pianotech around ten years ago, when I was coming to terms with my SAT).

Regards,
Fred Sturm
University of New Mexico 

  

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