You should check to ensure that the sound output is set correctly, to do this:
- Open Settings (The cog at the top of the main menu)
- Select "System"
- Go down to "Audio" on the left hand list.
- Select "Audio Output Device"
- You will see a few options, some will start with "ALSA: HDA Intel PCH" and then will include the name of your TV. As an example "ALSA: HDA Intel PCH, MCE Panasonic-TV on HDMI #0". Select whichever option has your TV name in it. If you don't see an option with your TV name try each of the options with HDMI in it.
When the correct output is selected you should hear clicks as you move around the screen, if you are not hearing this try the other option.