Here's some advice from Sony's troubleshooting website if you are having good picture but no sound:

- Check the volume level.

- Press MUTING or VOL + so that “Muting” disappears from the screen.

- Set Speakers to TV Speakers in the Sound settings. If it is set to Audio System, sound is not output from the TV’s speakers regardless of the TV’s volume control.

- When using HDMI input with Super Audio CD or DVD-Audio, DIGITAL AUDIO OUT (Optical) may not provide an audio signal.

- When tuned to a digital channel with Alternate Audio, the broadcaster may not be broadcasting your preferred Alternate Audio language. Press OPTIONS, highlight and select Alternate Audio, and change the Alternate Audio language.

From: http://docs.esupport.sony.com/referenceb...