To provide active noise cancelation, internal and external microphones measure unwanted ambient noises, then circuity in the headphones generates sound at a frequency that cancels out those noises. Active noise cancelation works whenever headphones with this feature are turned on.
Adaptive noise cancelation is a type of heightened noise cancelation. When you're listening to music, speaker output strikes a balance between audio quality and noise cancelation. When you're not listening to music, the level of noise cancelation automatically increases to block outside sounds.
Noise isolating earphones and headphones passively block out ambient sound without batteries. Adjustable-fit eartips on earphones and extra earcup padding on headphones act as physical barriers to keep unwanted noise from reaching your ears. These barriers also help prevent people around you from hearing your music.