This problem appears unique to my system, since nobody else is complaining on the forums. My mobo is Gigabyte Z370. I installed updated sound driver with no improvement. Tested with Falcon BMS and no problems with that program.
One symptom I just noticed is that while in DCS 3D world, unpaused, the VA sound detection bar at bottom of VA window shows full red sound detection, even tho I am using headset, no speakers and no ambient noise. Pause sim and bar shows no sound detected. So I conclude that for some reason DCS is passing 3d world sim sounds thru the OS to VA and this constant sim sound is causing all the other detection issues.