Is the camera in after effects? Or are you referring to an actual camera that filmed the scene?
If after effects, you could make a separate audio track with your effects and link the distance to dB levels. So as the camera gets further away increase the levels of the sound effects, but that might cause other issues. It would be better to finish the video portion, export it, and do your audio mixing in a separate program like Audition or Audacity. You will get better results there and have more control.