I've always been curious about those noise-canceling headphones you see all the business guys wearing on planes. Do they really help that much? Are they worth the expense? After grabbing a set of ATH-ANC7 QuietPoint headphones from Audio-Technica, I can answer definitively "yes" and "yes."
The ANC7s are over-the-ear (or "earcup") headphones (as opposed to in-ear- or earbud-style phones) and they do a bang-up job blocking out noise. Even without the active (i.e., powered) noise-canceling circuitry enabled, the ANC7s do reduce environmental noise. But when you flip the switch to ON, man, it's like a veritable cone of silence has descended over you (Google if you don't get that reference). The specs say they reduce ambient noise up to 20db or 85% (I've no idea how the conversion works, so don't ask); I can tell you that 20db (or 85%) makes a heckuva difference. After a couple of recent 4-hour flights, I was noticeably more relaxed and less stressed than I usually am after such a flight, and I attribute that to the use of these headphones.
The ANC7 has some nice design features as well. For starters, the cord is removable, so if you only need noise canceling (i.e., you don't want them plugged into an audio source, such as when you want to sleep on a plane), then you don't have to futz with a cord. The ANC7s come with a semi-hard case, too. The case has an interior accessory pocket that stores the audio cord and included full-sized (1/4-inch) stereo and airplane (two-prong) adapters (a nice touch, Audio-Technica!). The ANC7s are powered by a single AAA battery (1 included) and I got about 15 hours of mixed use (noise-canceling only and noise-canceling + audio) from a new cell.
Unlike the Bose models (which generally run $299 and up and don't offer any better sound quality than these), the ANC7s can be used as unpowered headphones. Sound quality without noise-canceling turned on isn't great; it sounds a bit muffled, but it'll do in a pinch. However, with the noise-canceling enabled, the sound quality of these is very good; they almost give my open-air Grados a run for their money, and that's saying a lot.
So, if you travel a fair bit, or perhaps work in a noisy environment with white noise you find distracting, plunk down the $120 or so for a set of these and prepare to be amazed.