Head tracking senses the rotation of the listener's head — via sensors in headphones, earbuds, or a VR headset — and counter-rotates the rendered sound field so that virtual sources stay fixed in the room rather than turning with the head. It is what makes spatial audio feel anchored and believable: turn to look at a character and their voice stays put in front of you, exactly as real sound would. It pairs naturally with scene-based (Ambisonics) audio, which rotates cheaply, and with binaural rendering over headphones. Apple's spatial audio on AirPods popularized it for music and film, and it is essential to convincing VR and AR, where a static soundscape would instantly break the illusion.
