I'm thinking of work that is still definable as Noise but with a subtlety, less emphasis on harshness and "spasticity" and other kinds of outward aggression and more on softer distortion and course, abrasive sound.
I suppose what I think of most is the more recent work of MB. Some material does go more straight into ambient than Noise but there is, such as on "Neurotransmitters", a nice Industrial crunch along with the smoothness.
One album I go back to is a collaboration between Zan Hoffman and Minnoy called "Mmmazamm", a lovely, extended piece of gritty fog. Just the right mix of coarseness and ambience.
The Mark Solotroff series recently put out strikes me as almost an acme for Ambient Noise. The majority of the pieces are lengthy, relying on texture almost solely without making too much of an effort to change drastically, and in many cases mix a softly distorted filth with extended ambience.
Perhaps the Grey Wolves "Blood And Sand" on Cold Spring? They've never been afraid to show their softer side yet it's the lo-fi grit and course, natural sounding distortion on most of these two pieces that could let it qualify.
Leave us not forget PBK's own label,
Noise Ambient. A bit odd for me as the examples I've heard of his work I wouldn't necessarily place under such a label, but I admit I've heard only a few albums so far.
Anything else?