Instructions
Basics
Ensure that the problem isn't with the TV itself. Turn the volume up and down to see if the sound is muted or too low, and view a TV channel or a movie in a DVD player to see if you can get sound that way. If there's no audio from any of those sources, then the problem is actually with the TV, so consult its manual or contact the customer support division of its manufacturer.
Check the PS3's cord connections. Depending on your setup, you may have a single cord or a couple of cords connecting your PS3 to your entertainment center. The cords should be securely connected to the PS3; if they're loose or disconnected, your audio may distort or disappear altogether.
Check the TV's cord connections. Like the PS3, the TV must have a secure connection to every cable connected to its ports. In order to have an audio signal at all, you must be using one of the following jacks on your TV: HDMI; twin stereo RCA, or "composite," jacks colored red and white; or digital audio, also called "optical" or "Toslink."
PS3 Audio
Look at the connections on the back of the PS3 to see which jacks you're using for audio. The three options are "AV MULTI OUT," "HDMI OUT" and "Digital Out." The first two are connections that each bundle audio and video together; the third is a connection for audio alone. If you're using a setup that's connected to two of these jacks, one of those two must be "Digital Out." Under no circumstances should your PS3 be using "HDMI OUT" and "AV MULTI OUT" at the same time.
Go to the "Settings" section of the XMB menu on your PS3.
Select "Sound Settings," then "Audio Output Settings." Configure the PS3 for its current audio setup here. Your PS3 doesn't know when you switch to a new TV, so if the PS3's audio settings need to change for that TV, you have to adjust them yourself.
Select the audio option for your setup based on the connections your PS3 is using and press the right directional key to continue. If you're using "HDMI OUT," select "HDMI"; if you're using "AV MULTI OUT," select "Audio Input Connector / SCART / AV MULTI"; If you're using either of those as well as the "Digital Out" connection, then select "Digital Out (Optical)."
Select the audio output format that your system is compatible with and press the right directional key to continue. This only applies to the "HDMI" and "Digital Out" options; if you're using the "Audio Input Connector" option, this screen does not display. If you're unsure of the formats, go with the default options or, in the case of "HDMI," allow the PS3 to select the format automatically.
Check over the review screen to make sure you selected the right options, then press the "X" button to confirm your configuration. Your PS3 should now be set up to properly use your audio system.