LG HU70LA Owner's Manual page 167

The volume changes when I change the channel.
•
The volume of different broadcasting stations transmission output may vary.
• (Q. Settings)
Set [Auto Volume] to [On].
•
If you are using a set-top box, consult its supplier.
The sound does not work or only the background music is played in some
programs. (Programs produced for export by broadcasting companies)
• Wheel (OK) or
• Set your language preference in [Audio Language].
The stereo sound is not clear on an analog channel, or there is no sound from
one of the speakers.
• Wheel (OK) or
Applies only in countries where sound multiplex broadcasting is available.
Select [MONO] in Multi Audio if you are out of range or sound multiplex
broadcasting is not stable.
• (Q. Settings)
Adjust the balance as necessary with the Navigation button in [Balance].
[Sound] [Auto Volume]
OK
OK
[Sound] [Sound Mode Settings]
115
[Balance]