AVS Forum Special Member
Join Date: Nov 2013
Location: Salem, Oregon, United States, Earth
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First, I am assuming the TV has an actual HDMI port you are using, not a DisplayPort with a HDMI-to-DisplayPort adapter. (DisplayPort wasn't designed to carry audio.)
Since you didn't identify the cable service nor the cable box, I can't even look up the manual for your cable box. But somewhere your cable box probably also allows you to select one of a limited number of audio formats, and select whether to turn off or use the TV speakers. It is in those settings that you may have set up the audio options to make best use of your Receiver but may end up being incompatible with the TV.
For example, the RNG200N HD-DVR that I am renting from Comcast has a setup menu (accessed by pressing the Menu button twice, then clicking on Setup), and Audio is one of the choices on that menu. On that menu there are several options, including Surround Sound, Stereo, TV speakers. I personally have that set to TV Speakers, then I clicked on the button that says "Optimize".