Instruction: Extract information from the supporting document to answer the given question.

Input:
Question: Can you use the noise-cancellation feature even while the headphones are not plugged into any music device? (Want to use for quiet, as a sleep aid; don't want to have a music device playing at night).
Document: Didn't want to travel with clunky, over-the-ear headphones but wanted a pair with decent noise-canceling capability. No, they're not cheap, but they work. I was surprised at how very well they work. Supposedly the acoustics aren't ideal for classical music, but my ear isn't that sophisticated. I was listening to opera all night on an international flight and it sounded great to me. Blocked out everything else that was happening on that plane and allowed me to sleep far better than I usually do.
As a weekly transcontinental traveler, a good noise cancelling earphone is paramount to my &#34;sleep night&#34;. I have used the QC20s for a roughly 1.5 years before trying the 20i and I am not disappointed.As many other reviewers pointed out, there in a considerable gain in noise cancelling performance (especially when no music is playing), and the static white noise is considerably better than the QC20.
I had high expectations for these headphones that were beyond their capability.I expected them to completely mute outside noises when not playing music. They can muffle loud close noise like traffic but not eliminate it. However the playback is really superior and cannot be overcome by outside noises unless you are listening to something like quiet passages in classical music.The call answering feature comes really in handy if you are listening to music with your smartphone and need to answer an incoming call. Android model also works well with iPod.
"Finally" broke down, put on these buds with some quiet music, and got a decent night of quiet and snooze-time. In the morning, one bud had fallen out during the night, but the other was still where it should be.. So, consider these as potential sleep aids, if you need them!
I also didn't want to have to use AA batteries, which are a pain. I also wanted smaller earphones that fit in my bag. The Bose earphones met these requirements.As for how well does the noise cancelling work. Well, I am sitting in the fairly quiet train now. Even without music, I can't really hear the wheel noise at all, except for a little bit when it squeals around a sharp corner.
Just finished long plane trip that's 24 hrs door to door. I was astonished by the quality of the noise canceling. The QC15s do a wonderful job, but the 20i is superior in cancellation and so much more comfortable and allows you to sleep in any position. They have very robust cords and I used them for both flight entertainment, iphone music and simply on for sleeping. The flat battery I clipped inside the v neck of my sweater when not attached to device and it lasted the trip.
Even though I use these headphones in many different settings, the reason why I really want them handy is when getting on a plane. There is nothing like the feeling of peace and quiet that these give you when you turn them on either for watching a movie or for relaxing to some tunes.The noise isolation is impressive. Before getting these I would typically carry my Bose QC2. There are two drawbacks to my previous choice that are completely solved by the QC20i.
Horrible. Should be 0 starsIf you really want quiet don't buy these. I listed a few recent examples of why I thought these headphones should be 0 stars.On a recent 5 hour flight to Vegas, a baby was crying 5 rows from me and even with the music volume turned up 100%, I could hear the baby as background. As hard as I tried to get the baby to cry in tune with the music, I just could get the baby noise canceled.
The Bose earphones fit in easily and stay put. I used the headphones on a plane trip from Boston to Australia. They were great - quiet and comfortable when not playing music and comfortable and sounding good when playing music. Probably more effective than the on ear phones. One downside was that they ran out of battery before I got to Australia. On the way back I topped up the charge at LAX. The battery probably lasts around 12 hours which for most use is fine.
Excellent noise cancellation and a setting that allows you to hear the surrounding sounds without interfering with the clarity of the audio - a good safety feature when using the device is public areas. If you are a passenger and can use both ear buds, then the noise cancellation is great to drown out the street noise and you rarely have to adjust the volume. Using the ear buds without the noise cancelling feature blocks external noise better than the other ear buds we tried.
Answer: I really like my headphones, but honestly believe that a good set of earplugs would work better. They will work without music playing. I sometimes do this on a plane. They do an excellent job of blanking out the engine drone but I can still hear people talking (albeit at a much reduced volume)