No audio when AirPlay mirroring from MacBook Air to Apple TV
Found a solution on Apple forums, posting it here in case anyone else runs across this problem. I had to:


Turn off AirPlay Mirroring
Open Sound.prefPane and select Apple TV as the output
Turn AirPlay Mirroring back on


For some reason it appears you have to manually set the sound output before connecting AirPlay Mirroring

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