StickyItToYou The USB port is what powers the decoder for the wireless, not using it would prevent the decoder from sending a signal to the headset resulting in no audio at all. I use the SPDIF Out on my motherboard with the provided digital optical cable that plugs into the decoder's Opt In port. This works fine for Arma 2 and Operation Arrowhead but for some reason not for Arma 3.
I can hear every noise in the game except for: My own weapon's gunshots, Countermeasures deployed by me in aircraft, My Aircraft's weapons being fired, and pretty much every sound triggered by the player that has to do with shooting or deploying something.