iOS 6 beta 3 that was seeded to registered developers a couple of days back, adds the ability to stream audio to AirPlay speakers from the Apple TV.
Previously, the Apple TV could only receive AirPlay streams.
The change was noted by FlatPanelsHD:
The AirPlay speaker-out function can be found in the AirPlay menu on Apple TV. From here you can select all your AirPlay speakers in your home. The Dolby setting option in the audio has to be turned off. Otherwise, sound volume is very low, it is said.
AirPlay enabled speakers on the same network as the Apple TV are detected, one of which can then be chosen to stream audio.
AirPlay audio out enables the Apple TV to do a better job at being a media streamer, freeing itself of the constraints posed by physical cables.
Amid rumors of the Apple TV platform being opened up to developers, Apple has been incrementally adding features to the Apple TV, by first overhauling the UI, adding the ability to rearrange inbuilt apps and now enable AirPlay audio out.