Sound output on the TV Box is managed by Android TV.

You may connect Bluetooth headsets/speakers to the TV Box via the Settings > Android Settings menu.

However, there is a major limitation today when watching Live TV on Cable network: as the sound & picture tracks are protected by the CAS security, the Bluetooth devices currently can't access the audio source which means you won't hear the sound on Live TV. Sound is OK on other sources (Apps but also Recording playback, VOD and Replay/Startover). We're working on a resolution but it's not available yet.