So I've gotten this bug in the past, but it's happening more and more frequently recently. Often i'll tab out while waiting for a game to fill, but lately, when I do this, I will not hear that the game has started (the drings and whatnot.) This usually leads to me vegging, but if I manage to come back and not veg, all the sounds that I missed will then play. As far as I know, this fixes itself after that (even if you don't get sounds pregame, if you come back after game starts, and then tab out again, you will then get sounds while tabbed out.)