Samsung 8000 Series User Manual page 536

The picture is good but there is no sound.
Set the Speaker Select option to TV Speaker
in the Sound menu.
If you are using an external device, check
the device's audio output option. (Ex.
You may need to change your cable box's
audio option to HDMI if you have the box
connected to your TV using an HDMI cable.)
If you are using a DVI to HDMI cable, a
separate audio cable is required.
If your TV has a headphone jack, make sure
there is nothing plugged into it.
Reboot the connected device by