Benjamin Mayo, 9to5Mac:

If you have an Apple TV, particularly when connected to a secondary speaker system, then you can be afflicted by a common AV issue: unsynchronized audio.

The video signal is processed by the TV at a slightly different time than the audio is transmitted from the speaker system. This leads to a delay where the audio is out-of-sync to the video frames, often noticeable by looking at an actor’s lips move … but hearing the words a beat later.

What can you do? Physics, right? But:

With iOS 13 and tvOS 13, Apple aims to combat this problem. You can enter a new configuration step called Wireless Audio Sync. This is initiated by pressing a button in the Apple TV settings.

And:

As part of the process, the Apple TV will play a series of tones. The iPhone then measures how long it takes to hear the sounds. This calculation is then saved on the Apple TV.

The tvOS operating system can then send audio earlier or later using the time offset it calculated from the Wireless Audio Sync data, thereby synchronizing audio and visual outputs.

Cleverness abounds. Yet another example of Apple firing on all cylinders.