Got these as a gift, sent 'em back and here's why.  The only thing that 'noise cancelling' does is boost the audio.  So maybe sound amplifying, but not noise cancelling.  It didn't make the sound better, just a bit louder.  There was no noise cancelling evident AT ALL.  Not that I needed to confirm it (my ears did fine), but a dB meter confirmed a sound boost when switched on.  Which is 'ok' I guess, but that was all it did.
 
I wrote the above to AT and got back a response that noise cancelling doesn't take effect until a certain hz.  Really?  Gee whiz Mister, thanks!  Another set of NC headphones I have works fine with 'droning' type sounds (vacuum and a air conditioner).
 
Total junk and it makes me steer away from AT for anything.