Going slightly off topic, would over-exposure sometimes help reduce noise? I read that with the Olympus 4/3 cameras, there can be terrible noise when underexposed, but with some exposure compensation the results can be pretty decent. Has noise got any relation with exposure?
Overexposing will only make the number of blown out pixels higher thus washing out the noise.
I also find noise more noticeable when it is on black areas.
Noise is created by electromagnetic radiation produced on the sensor. Higher ISOs increase the ratio of noise to signal so exposure has nothing to do with it.
I prefer noise to a large amount of blown out pixels.