Hi,
Check if there is sound when using headphones or an external audio system connected to the TV to determine whether the problem is with the TV speakers or the audio settings.
To set the sound output for headphones or an external audio system, press the Home button then select ''Settings > Sound > Headphones/Audio out.''
If still no audio, have you checked different input types e.g. RF (coax antenna), HDMI or AV etc to see whether the problem is with the signal source e.g. Antenna, cable box of some description etc and not in the TV?
If you determine that the problem is in the TV here's an image of the ''No Sound troubleshooting flowchart'', from the [https://elektrotanya.com/sony_kdl_46hx855_az3f_chassis_sm.pdf/download.html|service manual] for the TV that may help.
[image|2717463]
(click on image to enlarge)