Use HomePod or AirPlay-enabled speakers with Apple TV 4K
You can stream audio from Apple TV 4K to HomePod speakers or stream audio (except system alerts and game sounds) to AirPlay-enabled speakers if they’re connected to the same network.
On Apple TV 4K, do either of the following:
Set HomePod or AirPlay-enabled speakers as your temporary audio output: Press and hold
on your remote to open Control Center, then select 
and choose the speakers you want to use.When you select AirPlay-enabled speakers (other than HomePod speakers) as your temporary audio output, Apple TV 4K plays audio through your AirPlay speakers except system alerts and game sounds, which play through your default audio output. Your speaker selection resets to the default audio output after Apple TV 4K is put to sleep.
Set HomePod or AirPlay-enabled speakers as your default audio output: Go to Settings
on Apple TV 4K, then go to Video and Audio > Audio Output and choose the speakers you want to use.When you select AirPlay-enabled speakers (other than HomePod speakers) as your default audio output, Apple TV 4K plays audio through your AirPlay speakers except system alerts and game sounds, which play through your TV speakers.
You can see a full list of Airplay-enabled speakers on the Home accessories website.