Interpreting noise

goodchild.trevor@gmail.com wrote:
> How do I know the difference between a signal which is decreasing in
> power as frequency increases because of its characteristic distribution
> (e.g., pink noise, brown noise), and a signal which is decreasing in
> power as frequency increases because it's band limited (e.g., white
> noise with a continuous falloff)?

The difference between "signal" and "noise" is basically the the
"signal"
contains information you might find "useful" in some sense, while the
"noise" does not. Note that the "useless" noise might contain
information
that might be useful to somebody else than you, or elsewhere than the
current application. The obvious example are two interefering radio
sources, one you want to listen to and the other interfering.

So basically, you have to characterize the useful signal as good as
you possibly can, and then regard evberything else, that does not
fit those characteristics, as noise. You can't generally say that
a signal is noise merely based on a general spectrum shape.
I know there exist radio systems where the emitted signal has
a spectrum resembeling white noise.

Rune