Plug your computer into a different circuit

As I continue to experiment by recording noise in my system by placing a sensitive mic about an inch away from my right channel tweeter, I've stumbled upon an interesting finding: my computer, a simple windows laptop, when plugged into my PS Audio Duet filter, adds a tremendous amount of noise - relative of course. So I plugged the computer into a different circuit and wouldn't you know it the noise is gone. Very interesting, and I never would have guessed or heard this without this listening method that I've been toying with.
Does it make a big difference running the laptop using the battery and not plugging it in at all?