hello. 

i can't explain this feedback. perhaps it is due to some iteration when reading some table. anyway, there is a problem in the abstraction : noise~, as you say, is not a gaussian noise source. it is a uniform white noise source. 

to have a gaussian noise source in pd, i suspect a pd external should be writen.  Karl-L. Noell and  Helmut  Weber  wrote a library that implements the Marsaglia uniform random numbers generator. Inside, there is a routine to generate gaussian numbers. I used it to write some externals for maxmsp. the sources, that are public, could be easily adapted to pd ...

http://www.sonoscop.net/jmb/pub/gaussmt~.zip  (gaussian number generator using mersenne twister uniform random number generator)
http://www.sonoscop.net/jmb/pub/gaussm~.zip (gaussian number generator using tt80 uniform  random number generator)
http://www.sonoscop.net/jmb/pub/gaussr250.zip (gaussian number generator using r250 uniform  radom number generator)
http://www.sonoscop.net/jmb/pub/gauss~.sit (gaussian number generator using Marsaglia uniform random number generator)
http://www.sonoscop.net/jmb/pub/rojo~.zip (red noise generator  using Marsaglia uniform random number generator )
http://www.sonoscop.net/jmb/pub/ruidist.zip (red noise, 1/f^alpha noise, random  number generator and statistical distributions)
http://www.sonoscop.net/jmb/pub/ruidos~.zip (marsaglia, tt80 and mersenne twister uniform random number generators)

jmb



El 20/08/2006, a las 11:37, alberto..zin@@poste..it escribió:

Hi ~Kyle,

But is the algorithm only supposed to generate 1/2 of the
hfa array?
I "doodled" in it, just to play with the convolution, and
now the
agorithm is only writing to the first 512 locations of the
array.  Is
it a bug?

It is wanted to be like that; actually in the original algo
there are arrays (of noise and hfa coeff) of 2n elements: n
values are filled, the other are padded with zeros.
Then real fft is done on the first n and convolution on 2n
elements.. so mine is an adaptation of this. When I looked
at the spectrum (in audacity) the noise seems to behave
fine; my concern is the strange sensation
in hearing the noise, like a small "feedback" even on a
single channel of output for high alpha..

Alberto



On 8/19/06, alberto.zin@poste.it <alberto.zin@poste.it> wrote:
Hi,

attached is an abstraction for generation of "colored" noise
(http://en.wikipedia.org/wiki/Colors_of_noise) using a
relatively new method (by J.N. Kasdin, 1995) that uses
frequency domain multiplication. White, pink, brown noise
(and intermediate flavors) can be obtained by varying
a single parameter (the slope of the spectrum in a linear
log(PSD)-log(f) plot).
I searched a bit in the archives and it seems to me that in
for noise generation in PD we actually have noise~ (uniform
white noise), pink~ (from zexy and cyclone) and a variety of
filters, but no direct generation of 1/f^a noise (am I
right?).

Inside the archive there is a short readme, look at it
first. To me the patch sounds a little "tubby", let me know
if you have the same feeling.

Any comment, suggestion for improvements is welcome.

The abstraction lives in
http://www.puredata.org/Members/AlbertoZ

All the best,

Alberto Zin



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