I have been dealing with this bug for a while now, at least a year or more (stopped playing for a while and recently started again). It was driving me nuts, I couldn't hear any impacts either bullets or missiles.
So over the weekend I was messing around trying to figure out why I still cannot hear impacts on my aircrafts (f15c & a10a flaming cliffs). I found that if you uncheck the box that says "hear like a helmet" or something, I unchecked that box and now I can hear impacts.
Not sure if that's intended, but it seems to be my issue hope it helps someone.
