I love my D7000,,,,,,,,,but!

I have had my camera for about a year and love it. Recently I decided to look at the video recording side of things which again, the camera does very well. My 'but' is this. The video records the horrible grinding noise of the auto focus motor, to a degree where any original sound track is useless. I set it to AF-F and it is unusable.

Is this a common complaint when using auto focus in video mode or is there something wrong with my machine?