Serious sound issues

The last couple of days I’ve encountered some serious sound issues and today it’s rendered the game all but unplayable. I’ve had the silent vehicles for a while, which I can live with, but that seems to have extended to other parts of the game and now I have silent guns, NPC’s lips moving but can’t hear anything, music switching on and off intermittently. There’s no pattern - sometimes there are no firing noises but reloading comes through loud and clear. Sometimes everything is completely silent and then there’ll be one or two gunshots and then silence again.

Have tried switching on and off but no effect. It’s really weird playing the game in almost total silence. and tbh not very pleasant.

Any ideas?