If you are using an accessory device (DVD, DVR) check cables to see that they are secure and if device has audio out option that it is set correctly. Also check to see that Video and Audio cables are connected to matching inputs on your set.
If you are using DVI to HDMI you will need to use a separate digital audio cable. DVI cables do not carry audio signal. After attaching the audio cable if you still do not hear sound you may need to set Digital Audio In. To do so:
Note: Due to legal requirements, it is possible that with certain copy protected PCM audio qualities from a device connected to the HDMI input, the DIGITAL AUDIO OUTPUT signal is muted.
Please download and install the latest software version.