Personalized Spatial Audio is also a new feature and it's supposed to improve sound quality to your liking even further.
Arguably the most important update to this year's AirPods is the addition of active noise cancellation. The once Pro-only feature has now trickled down to the AirPods 4 ANC. And ANC works both ways too - it will tone down your surroundings during music playback and calls.
ANC comes with additional features such as Transparency Mode and Adaptive Audio. The former amplifies the outside noise so you can hear your surroundings more clearly, while the Adaptive Audio intelligently selects the appropriate mode depending on your environment. For instance, if the system detects that you are engaging in a conversation, it will turn on Conversation Adaptiveness and lower the music volume.
The case has also been revamped and Apple says it's the lightest and most portable one yet. With the said case, the buds can go for 30 hours of continuous playback, so no compromises in battery life.
The case also gets a small speaker so you can find your AirPods 4 easily or notify you of incoming calls, for example. Right next to the speaker, Apple has added a USB-C connector for charging. Now, the AirPods can be charged wired or wirelessly.

Apple

Apple AirPods Pro 2nd Gen