Hello,
Pull the fridge away from the wall and take off the access panel in the back to find out exactly where the noise is coming from. If it is from the compressor, check to make sure the mounts are tight and not making the compressor loose. If it's internal noise inside the compressor, you will probably need a new one. It's not something a diy can do because you have to open the refrigeration system. If it is the compressor you should check your warranty, it may be 5 years on a compressor. If not, you can just live with it if it's not too bothersome. Hope this helps.
JP, April 2006