[sdiy] Truly red noise

[Theo]

----- Original Message -----
From: Magnus Danielson <cfmd at bredband.net>


> From: "Theo" <t.hogers at home.nl>

>
> > Did you notice in the article all the way down Brown noise?
> > Spectrum given is 1/(f^2) and the color Red is suggested as in this case
> > Brown is not a color.
>
> The usefullness of Brown or Red as describing it have nothing to do with
what
> is a "color" in this or that languague. That kind of argument is nonsense!
> Actually, the whole "color" way of reasoning is all bullocks anyway, it
> actually have no real meaning, so it boils down to a matter of taste
rather
> than actual true meaning.
>

Yes sure agreed.
Just but the correct term is brownian noise, not brown noise, hence the
remark.

> What is more useful of the two is Red thought, since it makes sense that
> "pink noise" (with power-spectra of 1/f) is between "white noise" (with
flat
> power-spectra) and "red noise" (with power-spectra of 1/f^2).
>
> > A Pink noise filter is basically a LP filter with -3 dB slope.
> > This is often build as a single RC LP were the R is one resistor and the
C
> > made of multiple cap+resistor combinations.
> > Swapping the resistor and caps+resistors so that the resistor goes to
ground
> > and the caps+resistors become the input should change it into a HP
version
> > for Brownian noise.
>
> Actually, just remove the resistor-cap combinations in parallel with the
> capacitor and you have it. All you need is a "perfect" integrator.
>

Err, I don't get this one.
Wait I do, wrong color, I was trying to get the inverse spectrum of pink.
Think that would be some shade of blue.

Just one question.
When considering noise "colors" usually only the power-spectra are
mentioned.
However the distribution of  frequency density across the spectrum also can
make a quite notable difference.
Even when the power spectrum is correct, the sound can be quite different
from what is expected.
But never really came across a mention of this frequency distribution
effect, why?

The effect is most pronounced when the frequency density is relatively low.
I came across this when cooking up the noise oscillators for a soft synth
that used narrow noise bands instead of sines for additive synthesis.
Past tense, cause it ran on Atari ST and results where not too interesting.
The produced sounds really needed a chorus to live up.

Cheers
Theo


> Cheers,
> Magnus
>
> > Cheers,
> > Theo
> >
> >
> >
> > ----- Original Message -----
> > From: <allenre at umich.edu>
> > To: <synth-diy at dropmix.xs4all.nl>
> > Sent: Friday, June 25, 2004 7:05 AM
> > Subject: [sdiy] Truly red noise
> >
> >
> > > A tangent to the white noise thread--
> > >
> > > I was reading a book on electronic music awhile back and I remember
coming
> > > across some definitions for audio noise (these are off the top of my
> > head):
> > >
> > > white/gaussian noise - power of 1 (unity) over the spectrum
> > > pink noise - power of 1/f over the spectrum
> > > red noise (this is a little foggy) - power of 1/(f^2) over the
spectrum
> > >
> > > If this is correct, I should be able to get red noise by taking the
> > negative of
> > > the derivative of the pink noise, right?  How would this be done
> > > electronically?
> > >
> > > Now I've seen the "colors of noise" article here:
> > > http://www.hoohahrecords.com/resfreq/articles/noise.html
> > >
> > > But there is no math given for the red noise.
> > >
> > > Ryan Allen
> > >
> >
>