Yes, it works, but without a screen the configuration is not so easy.

Im looking for an audio extractor that works with apple 4 tv beamer and sonos arc.
Thanks for any advise

It's easier now in iOS12. In the Music app you simply tap the Airplay symbol in "Now Playing" and you can control music selection and Airplay speaker output for the Apple TV (Gen 4 or 4K only) without needing to turn on the TV or projector. The Apple TV must be first setup in the Home App and logged in to the same iCloud/iTunes/App Store account.

How does it get power? I need to connect it to a projector, but I haven't found a USB connection with enough power.