If you are having intermittant but persistant connectivity issues between your Apple TV and multiple devices, you may want to take a look at the troubleshooting steps in the following articles:
Sorry for the late reply, non of those links helped and the audio still cuts out. Even when my MBP says it's using Airplay output for audio, just doesn't work about 20% of the time.
This usually happens when left unused for 5 minutes, come back and start playing a video, the sound won't work.
Close my MBP lid, open it again, audio doesn't work.
Watch a video for a while, about half way through the audio fails.
Going to sell this soon and just use the HDMI chord, just too much hassle over the wifi.