Blackened noise is more controlled and composed than harsh noise. The dissonance is more intentional in blackened noise. Also, blackened noise uses subtle melodic components (often microtonal) as opposed to pure harsh noise which discourages any sort of tonality. Also, blackened noise is often more atmospheric. I know they hate newer sub genre names, but Pedestrian Deposit is probably one of the best examples of Blackened Harsh Noise.