How to listen to the Dolby Digital technology 5.1 surround sound through your television.
In order to listen to the Dolby Digital® technology 5.1 surround sound through your television, the content you are watching must have Dolby Digital technology 5.1 surround sound available. This feature is available on select digital broadcasts and streaming video.
IMPORTANT: Dolby Digital technology 5.1 surround sound is not supported on standard cable or analog stations.
The television outputs 5.1 surround sound to your Dolby Digital compatible sound system by one of the following audio outputs:
NOTE: For model-specific information regarding any of the information in this solution, refer to the supplied manual or iManual. Manuals are posted on your model support page.
Audio Return Channel (HDMI)
To use this option, connect to A/V receiver or home theater system that also supports the Audio Return Channel (ARC) feature using an HDMI® 1.4 cable.
Digital Audio Output (Optical)
Connects to the optical audio input of any digital audio equipment that is Dolby Digital (DD) compatible. To use this option, connect to an external audio system using an optical cable.
NOTE: You can find these cables and more online.  Go to Parts and Accessories. 
Some models require that the Internal Speaker setting on the TV be turned Off and that the External Speaker setting is set to External Speakers or Audio System depending. Otherwise, only a 2CH PCM audio will be output.