I had been thinking about getting a pair on noise cancelling headphones mainly for when I am travelling, although was hesitant as I was unsure of just how good they might actually be.
Wanting some in-ear headphones with active noise cancelling is very limiting, and to begin with I could only find the Sony MDR-NC11 and MDR-NC22 (the NC11 won the Which Don't buy award, so they were instantly out) and was very close to getting the NC22 - that is until I found these Audio Technica ones.
They come in a nice cardboard box, so no nasty plastic to have to cut open (useful if you want to make use of the Distant Sellers Regulations and send it back). What you actually get is the headphones, an extension lead, airline adaptor, 3 sizes of ear pods, a battery and carry case.
The inline adaptor has an on/off switch and monitor button, and is where the battery goes. Each headphone has a little microphone built in which is what is used for the noise cancelling, and actually cancels out what is reaching the ear (unlike the Sony where the mic is on the inline adaptor).
I turned mine on and was instantly disappointed - I couldn't tell any difference at all (I did this in an office, so background noise of the air con unit, people typing, computers etc). A second or 2 later, silence. Well, not total silence, but the background noise was reduced to a slight muffle - very impressive. There is a slight hiss introduced from the headphones, but this is only noticeable when there is no music at all.
Overall, I am very happy with these headphones. It is as good as I could have expected from in-ear headphones. Having used them on trains and planes I am having my iPod volume *much* lower and not being aware of any background noise. From time to time I press the monitor button (which lets background noise in for as long as it is pressed) and am always amazed how loud it is, and how well the noise cancelling is.
I did find that walking down the street to the train station wasn't much improved over my old headphones, but that isn't a problem for me as it's only a short walk.