I know this might sound stupid but you can try two "easy temporary fixes" which are:
1. Turning the TV off, unplugging it, then replugging it back in, and turning it back on.
2. Changing the input selection to a different input for a second and then changing it back to whatever you are using.
When I had my 73" 3D DLP from them, I had similar issues, but typically it was the picture with no sound.