Sony Bravia TV & Sony Home Theater Audio Connections

First, go into the cable box's audio setup menu and make sure it's set to output digital audio through the hdmi connection. It might be set to analog audio output. Then make sure the hdmi input on the Sony dvd system has been assigned to whatever Input button you use on the Sony systems remote control.

If those two things don't help then give us the model numbers of the tv and dvd system (and cable box if you can. That will help us a lot since all these things seem to operate a little differently.

I found this on pg 12 of the cables boxs manual

The HDMI interface automatically confi gures the audio output for a format supported by the television. Because not all
TVs support the Dolby Digital input, the HDMI interface may automatically select a 2-channel stereo audio confi guration
instead of Dolby Digital, which it carries over to the other digital audio outputs of the set-top. This prevents your home
theater system or Dolby Digital decoder from providing the full Dolby Digital surround-sound effect.
You can override this confi guration by completing the following steps.


1. Press SETTINGS twice on the remote control to open the General Settings menu.
2. Press MOVE UP or MOVE DOWN to select the option Audio: Digital Out.
3. Press MOVE RIGHT to select Dolby Digital. This setting will send Dolby Digital audio to the HDMI, DIGITAL AUDIO
OUT, and OPTICAL AUDIO OUT connectors on the set-top.


Notes:
• If the TV is not Dolby Digital capable, it may not produce audio through its speakers when the Audio: Digital Out
setting on the set-top is set to Dolby Digital. You can either switch the Audio: Digital Out setting back to HDMI
when you are not using the home theater or Dolby Digital decoder, or you can connect the baseband audio outputs
(OUT 1 Audio Left and Right) to the TV.
• Digital content is encrypted with High-Bandwidth Content Protection (HDCP) on the DVI/HDMI port. This set-top
is not compatible with devices that do not support HDCP. You must use either the YPbPr or 1394 connection to
connect the set-top to these devices.

See if you can perform steps 1,2 and 3. That may solve the problem. The cable box might be set to output stereo analog which isn't transfered via hdmi.

If this doesn't work maybe we can think of something else.