The sound parameters are not fully implemented so it means sounds are affected by occlusion or other such effects, But the major point at the moment is that sounds have no distance control other than a cut off.
Eg sounds cannot be heard past 400m, any sound below 400m sounds like its source is right next to you.
This makes communication either TS or Voip next to impossible.
When turning down the audio in the options a strange effect occurs. It appears to reduce the volume of your weapons firing but reduces the impact and explosion sound to an unequal level that is much higher than that of the weapons firing.