I searched for days and tore my computer apart trying to get it to work. I am using the realtek dolby 5.1 via optical and an nvidia 1070. sound would work on cutscenes but once gameplay started it was silent. Finally saw something tried and it worked. Here you go...unless this is old news sorry...figured I couldn't find it so thought I'd post...forgive me if it's outdated:
find the launch application file, right click properties then set at "run as administrator" as well as compatibility for Windows 7.