Maybe a new idea? Maybe not, probably not but.........

Ok, I was doing some recording in my home studio this evening. I was drinking some beers as well. :sam: :sam: I like to run the system with no (or apparently so) with no mic input. Ive done this alot over the years and always heard "something" along the white noise. I deal with it because I realize I don't have a great (or even good) sound room. Well I started to wonder, what if I were to take this noise real time, and subtract it from the input. Is this what dolby is? I was thinking along the lines of the bose (I know there is no love lost) noise reducing headphones I've seen advertised. Is this something interesting or am I just another idiot who can't see the forest for the trees?

Dolby boosts low level signals and then the reconstruction part attenuates them back to the original level. The improvement achieved is in the case where the recording medium has noise---the low level signal is recorded higher than it would be without the augmentation, and when you recover the signal, on playback for example, you get a net improvement in signal-to-noise.

Noise is a loaded and ambiguous term. It can mean any undesirable signal, which includes interference, and it can mean something truly random. To properly define and understand randomness is highly nontrivial.

You do touch on a very interesting area when you mention that you "always heard something along the white noise". There is a fairly recent active area of investigation about the influence of noise on system response that might be called "stochastic resonance theory". In essence IIRC adding a bit of random noise into a nonlinear system can enhance signal detection. It's quite a counterintuitive result; it qualitatively resembles the use of "dither" in analogue-to-digital conversion, but is something a bit different. Other than to point at the subject, I'm not conversant enough with it to say much more.

It sounds to me like you are asking about a noise canceling thing. Yes they exist. Waves, for example, has a plug in that "records" the background noise of a recording during a dead spot and then pulls that noise out of the recording.

Yes, if you have well correlated noises you may cancel them like any other function. Einstein once said about eggs and Universe, it may help.