Fantastic noise reduction, great sound, very comfortable.

The QuietComfort 15 are Bose's top-of-the-line noise cancelling headphones. Considering the price, I had high expecations for these, and they came through: They are indeed quiet, and very comfortable. 

I used these in a crowded office environment, where they filtered out a decent amount of noise even without playing music. They would also be excellent on an airplane. They are bulky, however - I would not recommend them for everyday mobile use, and absolutely not for exercise. 


Build Quality & Dimensions

The Bose QC15 are expensive headphones, and they feel like it. Build quality is excellent - plastic for the rigid parts and synthetic lining for the padded parts, both of high quality. They're lightweight but feel solid enough, the moving parts slide or swivel smoothly, and the earcup pads are firmly attached. They're also replaceable for $15, which is good to know. 

Mine are the Slate Brown version, which cost the same but the foam parts - earcups and headband - are covered in a very attractive tan lining, instead of the usual black. I really like this version; it gives them more of a hand-crafted look. The normal black-on-gray version looks great too. 

Height: 7.5 in (19.1 cm)
Width: 6 in (15.2 cm)
Depth: 1.5 in (3.8 cm)
Weight with cable: 6.8 oz (192.8 g)


Ergonomics, Comfort

I've used this all day in an office setting and I often forgot they were on. The earcups are very big and very cushioned, and the lining is high quality, all of which makes them breathable. Also, the larger amount of surface area grabbing the side of your head means they don't have to fit as tightly to stay put. 

The required AAA battery compartment is cleverly hidden on the side of one of the earcups, but once found, easy to access.

The on-off switch is located on the outside of the right cup, along with a green LED indicator. These both blend into the design nicely, which is great for aesthetics, but actually make it really easy to forget to turn them off when you're done. And when they're on, the battery is draining whether you're listening to music or not. It'll last maybe 2 days that way.

The cups swivel 90 degrees to lay flat in their case, which is itself sturdy and high quality, and designed to hold the accessories as well.

Sound Quality, Noise Cancellation

These are active noise cancelling headphones, which means they use electronics to hear outside noise and then play the opposite of that sound, cancelling it out. Doing this well isn't easy, so good noise cancelling headphones aren't cheap. With the Bose QC15, you're getting what you paid for.

When you first put these on and turn them on, it sounds like the people around you just started talking more quietly. Not whispering, but like the one loud guy always shouting into his phone is talking normally. The biggest reduction isn't the sound of people talking, though - it's noise reduction. Background noise, humming, wind, cars outside, etc. Or, the thing these are designed for - airplane cabin noise. That kind of noise reduction you notice immediately.

I should point out that you can use these strictly for noise cancelling - you don't have to plug them into an audio source.

I did a bit of research and found some numbers:
"QC15s were 19dB quieter at 400 Hz and 26 dB quieter at 40 Hz."
- Geoffrey Morrison, reviewing for Sound & Vision magazine

For noise reduction, these are excellent numbers, and according to my research, the Bose QC15s are regarded as the very best for noise cancellation. 

For me, audio quality is also extremely important, and I was curious whether the noise reduction would hurt it. In my opinion it did not - these earphones sound great, with a nice open soundstage, plenty of detail, and good bass. They are a true pleasure to listen to music with, completely separate from their noise-cancelling. That's really important to me, because the noise-cancelling can't be turned off - the earphones won't work at all unless they're on, and when they're on, they're cancelling noise. 


Accessories

Included with the QC15 earphones are a sturdy travel case, airline adapter, standard audio connection cable, inline connection cable with microphone and remote (the remote works with most Apple devices, but not Android, which is what I have, so I didn't test this), and a AAA battery.


Conclusion

I'm not normally a fan of Bose - I think most of their products are pretty good, but overpriced. These are different - they're priced typically for Bose, but they exceeded my expectations, and other reviews I've read indicate that they outperform pricier models.  

The Bose QuietComfort 15 headphones live up to their name: Quiet and Comfort are the two things they do extremely well.