Complicated issue. The SBLive is not the greatest card around. It has higher than (what I would call) normal CPU utilization.
But it is not the sole part of the entire problem. Many players use it with zero problems or drops in VOX. It seems tied to the combination of CPU speed, memory, OS/driver updates, and motherboard chipset. The Internet connection is suspect as well.
I never lost VOX with my old SBLive, and since I got the Audigy 2, my frame rates went up about 10-15 FPS (in all games) and I still have no issues with sound/VOX.
When you say you have no issues with other applications, it really does not mean anything. Those other apps are either dedicated to sound, or have very little CPU activity going on.
In AH, the CPU is getting used quite heavily. All the asynchronous events will collide to cause potential problems with VOX, if the system is not well balanced.
I am doing a lousy job of explaining this. What typically happens is the sound card backs up, for lack of a better defination. It does not take many sounds for this to happen. The SBLive does not expose any hardware buffers to DirectX, so DX is handling it all in software.
If two sounds hit at the same time and another tries to squeeze in, then it could cause DX to dump the buffers if the sound card cannot handle it. Bye-bye VOX.
DX controls the sound. Once we hand it a buffer, we go about our merry way.
Now, this is but one potential instance. There are many more.
Now, for what it is worth, there may be something in the Squad channel possibly related to when a squad member loses his VOX it somehow takes down everyone at the same time. I will not discount that and have talked to HT about it, but the above still holds true.
We understand the players frustration with this. I wish we could reliably duplicate the problem. To my knowledge, no one here has ever lost VOX and we have to connect to the server just like you guys do, over the Internet.