TV and Loop problem

I have a lg smart tv and a virgin tivo box. There is a split second delay in the sound from the tv if volume is turned up which is necessary when I watch tv with my wife. Its ok if tv sound is muted as when I watch on my own! I have tried all the settings and had a technician from the HA department but to no avail. When I had the standard tv there was no problem. Has anyone got any thoughts or advice on this?