Vorbis Noise Normalization Options

[dsimcha]

I've become very curious about how Vorbis noise normalization works. My (very vague) understanding is that it somehow avoids the metallic artifacts of MP3 and makes Vorbis's degradation when perceptual transparency can't be achieved sound much more like (less annoying) Gaussian noise. I can't seem to find a much more detailed explanation anywhere, though. Can someone please either explain it or point me to a decent explanation? I'm looking for a moderately technical explanation. Ideally, I want one that is intended for people with significant math background, etc., but is an overview rather than describing every small detail to someone who might want to implement noise normalization.