Rating: 
Summary: At least they're cheap...
Review: The fact that noise-canceling headphone reviews were all over the place made figuring out what to buy kind of difficult. I decided to buy the Sennheiser HDC451s, the Sony MDR-NC20s , and the Aiwa HP-CN5 , and the Etymotic ER-6 , try them all, and then return the three I liked least. Bose makes what are probably the industry standard but they weren't any better reviewed than the others and at ..., I wasn't interested.Here's what I found: Comfort: Kind of subjective, but in my opinion they rank as follows: Etymotic, Sony, Aiwa, Sennheiser. The Etymotics are basically earphones built into earplugs, so there's no bulk to worry about when moving around or trying to sleep on a plane. How comfortable they are kind of depends on how you feel about having things shoved in your ears. Of the conventional 'phones, the Sony's closed-ear design is more comfortable over long periods. The open-air design of the other two tends to squeeze your ears after a while. The Sennheiser loses because of an inexplicably uncomfortable pad in the top. Noise Canceling: Etymotic, Sony, Sennheiser, Aiwa. The Etymotics have no noise-canceling circuitry and rely purely on blocking the ear canal to reduce noise. This cuts more noise than the others and does it across the entire spectrum-making it the only one that will silence the kid screaming in the seat behind you. In the conventional 'phones, the Sony again benefits from the closed-ear design, passively blocking some high register noise that the others miss. The Sennheisers actually have the most elegant electronics, silencing low hums with less hiss than the other two. Remember that active noise canceling only works in the very low registers-like the rumble of an airplane. Sound: Etymotic, Sennheiser, Sony, Aiwa. The Etymotics live up to their reputation of being one the best sounding 'phones on the market at any price, though they can amplify body noises such as chewing. The Sennheisers sound really muddy with the canceling turned off, but with it on they give fairly crisp sound a bit lacking in bass. The other two remain kind of muddy sounding with somewhat sloppy bass which might make watching movies on a plane a little more difficult. Overall, the Sony and Aiwa don't sound any better than the cheap 'phones that came with my MD player. Convenience: Etymotic, Aiwa, Sony, Sennheiser. The Etymotics fit in your shirt pocket but are definitely harder to get in and out than the others and don't include an airline adapter. The Aiwas fold up quite flat, have the batteries in the headset and have a carrying case. The Sonys fold up (but are still bulky), include a carrying case, and have the battery in the headset. The Sennheisers don't fold, have no carrying case, and have the batteries in the cord. All three conventional units come with airline adapters. So in conclusion, the Etymotics are pretty much light years ahead of the others, but only if you are okay with having them jammed in your ears (didn't bother me, but my wife had no interest.) The conventional units all have their pluses and minuses, so you'll have to decide what features are important to you.
Rating: 
Summary: medieval torture device cutting into your scalp, sums it up!
Review: I wish I would have read the reviews. I have tried foam, pillows like another reviewer and a clean diaper and still too painful to wear! I can't believe how uncomfortable these things are!
Rating:
Summary: Astonishingly uncomfortable.
Review: The headband looks like it should sit flat on your head, but it doesn't. You have to move the headphones around a little to get the noise cancelling to kick in, and the sharp plastic edge of the band digs into your scalp like a slow medieval torture (yes, I have hair, it doesn't help). I have been seen sitting on planes with part of an airplane pillow on my head, just trying to make these livable for an hour. The low price and somewhat-functional noise cancelling are useless if you can't wear them. Order something else, I am.
Rating: 
Summary: very good
Review: I am a classical musician. I am very picky when it comes to sound. These are good ear phones. My only complaint is it doesn't handle really low tones and they are not loud enough.
Rating:
Summary: Do you want the battery imprinted on your head?
Review: I read and heard the hype of noise-cancelling headphones and how they will make my life much better. So, i went out and bought/researched most of the top selling headphones. The Aiwa model (HP-CN5) is the most value priced. But, it has a buzz when you turn on the noise-cancellation, and i certainly think that most of the noise-cancellation is being achieved by increasing the volume than anything else. Also, the battery slot is awkwardly placed above the left earpiece, and it thus constantly budges against my head. The Sony MDR-NC11's are quite uncomfortable, and cost nearly 3 times as much as the Aiwa model. The manual said that the noise-cancellation will work only if the earbuds are fitting "snugly," and from my experience it seems that the snugly fit of the earbuds is what cancels more noise than the noise cancellation technology. I must say, however, that these are the most stylish, sleek and portable headphones of the lot. Sadly, their noise cancellation is nominal, and not worth it for the pain of "snugly" fitting earbuds for extended periods of time. The third model i tried was the Sony MDR-NC20, which is the most expensive of the lot. It is definitely more comfortable than the previous models, and also has passive noise cancellation due to the closed loop cushion design around the ear. However, it will get uncomfortable when worn for long durations due to the small earcup design. In Summary, all three of these headphones cancel noise by adding a "buzzing" sound when noise-cancellation is turned on, and by increasing the volume of the music if plugged to a CD player. I would suggest using your money on a better CD player, and get comfortable headphones without the noise cancellation feature. Let me suggest Koss UR-20 or Koss UR-30 for beautiful sound quality and comfort, and the Koss THE-Plug or Sony Fontopia for ear bud type models. All cost less than 50 bucks! Enjoy, and i'll head to the stores to make all the returns! :(
Rating: 
Summary: they work for me
Review: I really can't complain about these. They accomplished what I was looking for, which was cutting down the engine drone on a 5 hour flight. I did not experience the discomfort that others seem to have, as a matter of fact, on my return flight I was able to grab the center 4 seats on the airbus, flip up the arm rests and take a nap while wearing them plugged into my shirt pocket. I also used them to reduce the ambient gibberish and un-intelligible announcements in the airport waiting lounges, again just connected to nothing. I did not buy them for music or computer use, but just to be more comfortable on the 1 or 2 trips a year.
Rating:
Summary: They hurt -- and they buzz!
Review: I wish I had checked the Amazon customer reviews before I purchased these Aiwa noise canceling headphones. The tension in the headband was too high, so they hurt my ears when I wore them. More importantly, they tended to buzz (electronically) when I used them with my laptops -- totally defeating any noise canceling benefit they might've provided. I was looking for a less expensive alternative to my Sennheiser HDC 451's, which are excellent. I guess I should've known better.
Rating:
Summary: Not good for high-frequency noise
Review: I work in a server room where we have 40 racks full of computers and hard disks roaring away, and I bought these headphones hoping that they would offer some relief from the noise. First off, the cord is way too short -- only 3 feet and 7 inches. So I had to move one of my computers closer to me so that I could listen to my music from my computer's sound card, and even then, I could not move my chair around too much. Second, I found that I could still hear the high-pitched whine of some of our disk racks. A closer look at the technical specs printed on the cover of this product revealed that the active noise attenuation frequency range is only 40 to 2,000 Hz, and the attenuation level is only 10 dB at 400 Hz. That's a very poor spec, considering that the human ear can hear noises from 20 to 20,000 Hz. There are far better products out there, like the Maxell HP-NC1 which offers about 15 dB of maximum cancellation, and has a cancellation frequency range of 20 to 15,000 Hz.
Rating:
Summary: Yuck
Review: Yuck! Way too uncomfortable - I couldn't last 30 minutes wearing this, let alone a 12 hour flight to Narita.
Rating:
Summary: Ouch!
Review: Yes they cancel noise and sound ok, but the hard plastic that rests on top of your head hurts - a lot! Major design flaw, and makes using these otherwise decent headphones unacceptable.
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