That seems more binary then I'd like.
The other problem is matrix access itself. If your node is the city away, but you're jacked in locally, there shouldn't be an issue. Seriously, the first coast-to-coast telegraph message in the united states only had a half second delay. A half second! With the advent of wireless and fiber optic communications, city-wide delays would be nill.
So Noise is going to have to be a wireless only feature, for devices not also on the matrix. (Is that possible now?)
Ideally, I'd like to see something as simple as -1 modifier per [distance unit] between attacker and target. Since I'm in love with the idea of the hacker *being there*, and not in their impenetrable invisible vehicle located nearby, i'd have that unit be a meter. I'm also an asshole, so take that suggestion with a grain of salt.