Sound distortion on music video playback

I spent at least an hour reading through the AppleTV forums yesterday & I could not locate a solution to the sound distortion during Airplay music video playback.

My set up: AppleTV3 (5.2); MacPro 2012 (OSX 10.7.5); iTunes (11.0.1) (HomeSharing is enabled on everything & ATV recognizes my MacPro's iTunes library); Sony LCD 55HX820; Mediabridge (latest) HDMI High Speed cable supporting sound; Apple Airport Extreme (newest) (6.2).

Distance between my Airport Extreme to the ATV is about 20 feet and is line-of-sight.

When I stream the handful of purchased music videos from iCloud, there is no sound distortion. When I attempt to use Airplay to stream from my MacPro, iPad Mini or iPhone 5, there is sound distortion.

I tried a Monster Optical Cable (as one thread suggested) from the ATV to the Sony and the sound distortion actually became worse.

Checked the direction on the Mediabridge HDMI cable (another thread suggestion).

I downgraded the AppleTV software to 5.0.2 (as one thread suggested), with no change to the sound distortion.

I reinstalled the ATV 5.2 software with no change.

I have rebooted the system, unplugging all cables for a few minutes and reconnecting each in the order of Airport, MacPro and ATV. No success.

I have tried all 4 HDMI ports on the Sony. No difference.

I am hosting a party in 5 days and wanted to be able to have music videos playing on the Sony. Is there indeed a solution to the Airplay problem? Any suggestions will be greatly appreciated!