There are two AirPods 4. This is the one with Active Noise Cancellation, which is the difference people care about and the difference between the two prices you will see quoted.
The other version is the same earbud without it. The shape changed.
A refined contour and a shorter stem, with quick-press controls on the stem for music and calls, and Apple's stated aim was stability — these stay put through a walk in a way the older open-fit ones did not always manage. There is no silicone tip to size, which is either the reason you buy them or the reason you do not.
Inside is the H2 chip, and that is what the feature list actually rests on. Active Noise Cancellation reduces outside sound before it reaches you; Transparency mode lets the room back in; Adaptive Audio blends the two as your surroundings change rather than making you choose.
Voice Isolation works on the other end of a call, separating your voice from a noisy street. Battery is four hours of listening with noise cancellation on, twenty hours in total with the case, and up to thirty hours with cancellation off.
The case is the smallest in the industry with wireless charging, and takes an Apple Watch charger, a USB-C cable or any Qi-certified pad. Both the earbuds and the case are rated IP54 for dust, sweat and water — rain and a hard workout are within what they are built for.
Personalised Spatial Audio with head tracking is there for film and games, and Siri Interactions let you answer with a nod or a shake of the head.