That sounds like a new bug. I have a few questions. Does it affect all sound or just certain sounds? Does this happen every time or just sometimes? Roughly how far away do you need to move to make it happen? When you say "suddenly mutes" do you mean you can hear some sounds and everything suddenly stops? If you go into Freecam mode, by pressing C and moving away, and make it happen?
Sorry for all the questions, but these will help we work out what's going wrong.