I had this problem in both betas. There would be no sound in slapsh screen or in game. I already tried reinstalling game and reintaling the ue4.exe. Still no go. How ever i figured somthing out. I launch game then alt-Tab change my sound seeting to my head phone. Exit game. Launch game. Then sound works. Then al-tab to change it to my speackers system. Then only after i click battle and then exit to main menu. Then sound kicks on my speackers system.