[sdiy] Truly red noise

[allenre at umich.edu]

I noticed that, but there are inconsistencies throughout the page and I've seen
literature describe 1/(f^2) noise as red, not brown.

The page says that 'purple noise' is differentiated white noise, but if white
noise has a distribution of 1, then differentiating it gives you 0 (silence).

I think it should go something like this:

.
.
.
'infrared noise', 1/(f^3) distribution
'red noise', 1/(f^2) distribution
'pink noise', 1/f distribution
'white noise', unity distribution
'blue noise', f distribution (given on page)
'violet noise', f^2 distribution
'ultraviolet noise', f^3 distribution
.
.
.

The black noise distribution seems consistent in keeping with the light/sound
analogy.

> 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.
>
> 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.

Wouldn't you want a steeped LP filter instead? Say, -6dB/octave slope?  If it is
HP then you have a proportional instead of inversely proportional distribution.

I would like to experiment and see how different distributions of the
frequencies can be obtained.

Ryan