Just got ArmA yesterday, and it runs fine, other than the sound. I couldn't tell you what soundcard I have, but I know it's pretty damn good. This doesnt happen in any of my other games, just ArmA.
Problems include:
Engine noises disappearing altogether.
Gunshots disappearing.
Gunshots being replaced by another sound effect, which gets extremely irritating when you're firing a machine gun, and it's going "roger roger roger roger roger roger roger roger roger roger roger roger roger roger roger " all the frigging time.
Speech cutting out halfway through sentences, or sometimes just not being heard at all.
Anyone else find this? Anyone got any suggestions for fixing it? I've turned off hardware accelerationa and EAX, but to no avail.