During Twitch streaming game audio mutes when I alt-tab out to other window

[Heliopause]

I stream CoH gameplay to Twitch using OBS and when I alt-tab out of the game to my browser the games audio mutes.   OBS has a Beta setting to allow the audio to play directly from the game but it doesn't.  How do I get this to work.  Does the game have a command line setting to not mute audio when the game is not in focus?