In windows, sounds are usually played though the 'default playback device', while communications are usually handled by the 'default communications device'.
This way, one can play the sounds of a game through speakers, while communicating with a headphone on (for example) TeamSpeak or Skype.
However, ArmA3 currently sends all commutations over the default device. We request making it possible to use our communications device for all ingame communications(Global, Side, Groupchat when using the ingame VON).