The QuietComfort 20 and 20i headphones weigh merely 44 grams and fit into any pocket. The acoustic noise cancellation technology, together with the special form of the earbuds, ensures effective noise reduction. Due to this feature, musical details are played back with remarkable clarity, or the wearer simply enjoys silence. A rechargeable battery provides power for up to 16 hours of listening enjoyment. When the battery is empty, the headphones will still play back music, but without active noise reduction.