Science

I'll give it a crack.

As others have hinted at, it's mostly about noise. The author puts noise in quotes when referring to those qualities of sound (and lyrics?) that are normally considered noise but are exploited for aesthetic purposes.

Thus, extreme volume and heavy distortion might normally be undesirable noise when trying to faithfully reproduce a sound, they are exploited by rock music in general and, in their extreme forms, by heavy metal in particular.

A metaphorical or all-inclusive understanding of noise can be applied to the various other aspects of music (rhythm, repetition, tempo, key changes, and even lyrics). The more of these aspects are affected (the more "noisy"), the "heavier" the result.

This was not addressed in the paper, but I think that the noise has to be introduced during the creation or performance of the music. If you play back a recording in ways that distort the signal or sound, you are probably getting noise, not "noise".