We have some expensive noise-cancelling ones at Wallyworld, where i work. We have a little station where you can try them on, then press a button that makes an annoying airplane noise, to demonstrate how they cancel noise. Problem is, they don't even cancel out half of the airplane noise, at least not to me. One time i was trying 'em out, with the airplane noise on, and then a co-worker, standing way over by the cash register, goes "psssst" really low. I turned around really quick, and he burst out laughing about how those 50 dollar headphones must not work very well if i heard that. So, i dunno. Those said they cancel out "up to 90%" of noise too. I don't trust those ads anymore.
Hope yours work better.