In relation to T160756 which I just send, I also observed that when staying into a contaminated area it is possible to hear birds and other animals ambient sounds. My suggestion is to make them silent when staying inside these areas. Explanation seems obvious, why birds and insects can live inside those zones and infected (except NBC ones) and survivors can't?

I observed this while inside Radunin contaminated area, and in server DayZ Livonia EU - UK 0-1 (Experimental/Unstable).