Active noise cancellation uses microphones to listen to surrounding sound and plays an opposite signal to cancel it. The technology has improved, blocking a wider range of noise and adjusting automatically to the environment, from a plane cabin to a busy street.
Quieter surroundings make listening pleasanter and let people use lower volumes, which is easier on hearing. Many devices also offer a transparency mode that lets outside sound back in for safety and conversation. Cancellation works best on steady, low sounds and less so on sudden noises, but the steady refinement has made it a feature many now expect.