I've not found noise cancelling headphones on their own helped all that much. For me, there's still a set of frequencies that seem to penetrate past the noise cancelling tech - outside street traffic, some walking on floors, low frequencies, certain speech. Noise cancelling headphones while using whitenoise works better (though still traffic and such get through, just not as distracting). That said, for me, whitenoise on its own with cheap headphones was much better than fancy noise cancelling ones. My wife had a pair of the high end bose noice cancellers last year - they didn't work for me for work purposes, and they were too bulky for her to sleep with.