[sdiy] Truly red noise

[Magnus Danielson]

From: "Theo" <t.hogers at home.nl>
Subject: Re: [sdiy] Truly red noise
Date: Fri, 25 Jun 2004 11:00:09 +0200
Message-ID: <000b01c45a92$d19d79a0$93b37ad9 at ensch1.ov.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.

What is more usefull 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.

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
> >
>