HDMI hooked up to set top box can cause
audio distortion.Try entering the cable/satellite STB set the output parameters.format to:16:9,dvi/hdmi/component=1080i fixed,4x3overide off,color space can't be RC 4:4:4-hast to be set to RGB,next enter
audio menu and select PCM or LPCM if Dolby Digital is enabled,Disable it.after parameters are set turn set top box off.
This may not be on all STB'S
edward