These headphones hush ambient noise by creating antinoise that obviates the noise at your ear. They don't eliminate noise, but the better models significantly reduce the whoosh of airplanes' air-conditioning systems. (They're somewhat less effective at quieting the background din on trains and buses.)
Bose Noise canceling headphones come in all forms, from full size to earbuds. Since you no longer have to crank up the volume to overcome background noise, this type of headphone lets you listen at lower levels, which leads to reduced ear fatigue. You'll also hear more low-level detail in your music.
