'Full spectrum noise reduction' it says in the blurb. Well yes, but when you look at the attenuation graphs you see that high frequency attenuation is bugger all, whereas at lower frequencies it is appreciable. You need a decent amount of passive attenuation to go with the active which is where the Bose falls down. TRY BEFORE YOU BUY. Best so far is the Sennheiser HMEC 450, and I have owned Bose X (good, flashy, but poor high frequency attenuation), and DC X11 (pish, basically).