The following article provdies some useful troubleshooting that can help resolve audio issues with your Apple TV.
Go to your Settings icon on the Apple TV. Look at your audio settings. If your audio output setting is "auto," try changing it to "16-bit." Or, if your audio output setting is "16-bit," try changing it to "auto."
I redeemed and transferred the digital copy from my Skyfall DVD into iTunes. The audio was just fine when I played the downloaded file on my computer, but when I tried to view it on my HD TV via my Apple TV, there was no sound. I changed my Apple TV's audio output from "auto" to "16-bit" and it fixed my problem.