Does the video sound staticky (sorry, invented a word there!) only when it is played in camera or do you hear static both in camera and on the computer? If it is only in the camera, you may have the playback volume turned up too high. The tiny speakers in the camera are easily overdriven, which makes the static. Hope this helps! I am not very familiar with Nikon, but my 70d behaves the same way when I crank the volume up too much.
