Okay, if the PS3 does have sound on this TV, but Direct TV does not, then the problem is not with the TV.
First, make sure the Volume is turned up on BOTH the Direct TV box AND the TV. Each has its own independent volume control and if one or the other is turned down, then you will have no sound.
Beyond this, please reset the system by following the steps below:
Please shut the TV and Direct TV box down. Unplug the Direct TV box from AC power for minutes. During this time, disconnect and reconnect the HDMI cable on both ends, making sure it is secure. Then plug the cable box back in, turn on and let it reboot. Once it's rebooted, then turn on the TV and attempt to watch a program.
The sound should be back on at this point.
If you need further assistance, let me know.
If this answers your question, please click "Accept", as it is the only way we Experts get paid for our knowledge on the site. Tips and Bonuses are welcome and appreciated!!