Same here. Intro videos are fine but no sound after that.
I updated video drivers, added "-nohmd" to launch options, ran as admin (first just the game then both Steam and the game), rebooted at least a half dozen times, verified the game cache multiple times, tried Win 7 compatability mode, and disabled all other audio devices in Sound Control Panel.
I even tried setting the output device to my Vive Pro headset (which was turned off/disconnected during all other testing) and still no sound. As a last ditch resort I upgraded Windows 10 from 1803 to 1809, still nothing.
Uninstalling and reinstalling UE4PrereqSetup_x64.exe as recommended in this thread also didn't work.
Hope this gets read. The how to report a bug or crash sticky says not to use tags in the post title or it likely won't get read. But it also says to post in an existing topic if there is one.... I can't do both.
Windows 10 1809
i7 920 @3.85ghz
24GB Ram DDR3 1600
Nvidia 1070 (connected to audio receiver by HDMI)