Characters in Ravage exhibit ambient voice chatter - that is to say, they will talk among themselves. If you get close to a group of AI units, you'll hear them talking. It's just another thing that adds to the immersion.

If you want to add voice chatter to manually-placed units, you'll need the following code.

execVM "\ravage\code\scripts\mission\ambientChat.sqf";//init system if not enabled from module
(group _myUnit) spawn rvg_fnc_ambientChat;