It feels like magic when you flip a switch and the roar of an airplane engine vanishes, but it is actually pure physics: destructive interference.
The Capture: Tiny microphones on the outside of your headphones constantly listen to the ambient noise around you.
The Inversion: The internal electronics instantly calculate the exact opposite physics of that sound wave (shifting it by 180°).
The Cancelation: The headphones play this “anti-sound” wave into your ear at the same time as the noise. When the peaks of the noise wave meet the troughs of the anti-sound wave, they completely flatten each other out, leaving you with silence.