I’ve heard about this on some sites dealing with binaural beats, brainwave entrainment, soundscapes, etc. but the only thing I know about it (that is, I think I know) is that it helps to calm your mind down, so you can sleep easier. Also, Iv’e heard some people here say that they fell asleep with a fan on, and the noise helped them sleep. Last night I noiced that while the furnace was running, I was more relaxed and sleep, but when It stopped, I kind of woke up a little. Is this white noise?
I wouldn’t think so, it most probably was just that you got used to it, and in the same way a sharp noise could jolt you awake, the sudden lack of noise did the same.
More info on white noise:
Wikipedia : White Noise