On Thu, 01 Oct 2009 08:17:39 GMT, "David J Taylor"

I don't ever recall adding noise, though.


Try adding a known noise to a noisy image some time. The human mind is a
wonderful thing. You will find that adding a known noise to an unknown
noise can actually enhance details hidden in the unknown noise.

A good analogy using another type of human perception (as opposed to
visual) would be the sensation of an itch. If you leave that itch alone it
will overpower your senses. The only thing you can think about and perceive
is that "itch noise" in your nervous system. However, if you scratch the
area, adding a wider and stronger region of known noise, the original "itch
noise" disappears in the added noise. The original itch still remains but
you don't realize it. It is now hidden in all the sensory noise that you
added. Effectively canceling out the itch's "noise". This is precisely why
scratching an itch works.

The same holds true for noise in a sound signal. If information is being
sent by sound but has a lot of noise in it, adding a known white-noise to
the noisy sound signal can effectively mask the unknown noise. Making the
information contained in that sound signal audible and intelligible.

This was a discovery of my own one time when in the kitchen, having turned
up a noisy band on the short-wave radio to listen to it while I was busy
cooking. The voices from the radio in the living-room were unintelligible
from the kitchen, the noise in the sound was just too great. By chance, on
the way back to turn off the radio, I first turned on the forced-air
heater-blower for my fireplace. The white-noise from the fan added to the
unintelligible radio transmission made the radio's sound signal amazingly
clear and understandable. I went back to the kitchen as intended and
listened to the broadcast as clear as anything. The noise in the radio
sound was still present. If I went nearer the radio I could hear the noise
the same as before. But the added white-noise from the fireplace fan
between me and the radio masked the radio's noise.

I have since expounded on this discovery about noise vs. signal to include
all other human senses. Adding a known noise to an unknown noise to
increase the available amount of valid information works with sound, sight,
touch, and I suspect taste and smell too.

People who dwell on "noise" in a signal have no idea what they are talking
about. They themselves are more of useless noise than the noise itself that
they constantly and noisily rail against.