Instructions
Turn off the TV, PS3 and any other devices that you have connected. Unplug and replug all the cables making sure that they seat completely into the plug. Examine the cables for cracks and wearing. Once you have verified that all the cables have a good connection, turn the devices back on and check your sound.
Replace any cables that appear to have worn out as this can cause the loss of the audio signal.
Log in to your PS3 and go to "Settings" and "Sound Settings" using the PS3 controller. Verify that the "Audio Out" is set to the cable type you are using for audio. Some home theater receivers only have the capability of "Stereo In" or "Digital Optical" inputs. If you are outputting to your TV using HDMI, you need to change the audio settings under the "Sound Settings" area of the PS3.