Summary: These headphones are extremely quiet. Even with the noise canceling (which there isn't much of), I still can't hear a thing. Turning the power on doesn't affect the sound quality, volume, or noise cancellation whatsoever. I'm not even sure what the power button is supposed to turn on exactly. Don't waste your money on these. I plan on returning these tomorrow.
Summary: I am a pilot and have a very good (Bose) headset for use in my own aircraft. I am therefore familiar with noise cancellation. I bought this headset to use with my BB10 to listen to podCasts on a long-haul flight and find that there is no difference whether the noise cancellation is turned on or off. They're going back, but if you do buy a set, don't bother to buy a battery for it --- it has no effect.
Summary: Pros: Comfortable Cons: Basically unnoticeable noise cancelling and bad quality. I received these headphones as a gift and upon looking them up and seeing the $50 price tag I got very excited. When I tried them on the first thing I wanted to do was try out he noise cancelling. So I was in the car and I decided to flip on the noise cancelling to see if it reduced the road noise.