I was driving home from work and my IS made this noise. The noise is off and on and when it happens it's only happens for a few seconds. And before I take it to the shop I was hoping that someone here can help me out.

I was able to record the noise. My upload is 56 seconds but the noise at the begining and it's only 4 seconds long I thought I had press the stop button.
http://www.zshare.net/download/800592267d541dd9/