[Fluxus] puzzle

[evan.raskob [lists]]

Usually it's as Kassen said - looks like an exponential curve to me,  
but the theory behind it is that the frequency bands should be double  
with each step, like Kassen said.  So, if we're running at 44100 then  
the frequency interval btw bands is 22100/256 (highest freq we can  
detect is always 1/2 the sample rate) = 86.328125

;-------
(define num-bins 256)
(define freqs (list 1 2 3 4 6 8 11 15 21 29 41 55 75 102 138 188 256))
(define half-sr 22100)

(define bin-width (/ half-sr num-bins))

(define bin-freqs (map (lambda (f) (round (* f bin-width))) freqs))

(display bin-freqs)(newline)
;-------

Gives:

(86 173 259 345 518 691 950 1295 1813 2504 3539 4748 6475 8805 11913  
16230 22100)

Which isn't ideal - we could easily throw out the 86 at the start and  
the 16230 and 22100 at the end and increase the range in the middle.   
Of course, this means that the range won't be perceptually accurate,  
but who cares - that won't help its usefulness.

So, taking bins (starting numbering at bin 1, not 0):

2 3 4 5 6 7 8 11 15 21 29 41 55 75 102 138

(freqs: 173 259 345 432 518 604 691 950 1295 1813 2504 3539 4748 6475  
8805 11913)

Looks more useful, musically, to me.  Up for debate, though.  Its a  
pretty arbitrary thing.

Also, how come you were using 17 bins in the original? Shouldn't that  
have been 16?

Cheers
Evan



On Jan 17, 2010, at 9:33 PM, Matt Jadud wrote:

> Hi all,
>
> On Sun, Jan 17, 2010 at 12:40 PM, Kassen  
> <signal.automatique at gmail.com> wrote:
>> of this was obvious. I didn't do the math, I'll trust Matt that it  
>> checks
>> out. I would BTW expect these numbers to depend on the samplerate  
>> that
>
> All I did was ask Excel fit an exponential to those numbers (leaving
> out the zero). As the saying goes, "It looks like an exponential, and
> quacks like an exponential..." Whether those are meaningful
> coefficients, that's another thing entirely...
>
> Cheers,
> Matt