Before inspecting the compressor mounts, unplug the refrigerator to avoid an electrical shock hazard.
The compressor sits on rubber mountings. Those rubber mountings are designed to absorb vibration from the compressor. As the mountings age, they can become hard or disintegrate. When this happens, the compressor vibration is transmitted to the refrigerator and it can be noisy. Replacing the mountings is easy to do.
The compressor is located in the rear. It may be necessary to remove an access panel to get to the compressor.
Locate the compressor and remove the screw or retaining clip (labeled "A" below) of just one of the compressor mounts (labeled "B"). Using a pry bar, lift up the compressor enough to slip out the rubber mount. Inspect the mount for deterioration. The rubber should be firm but not rigid. If the mount is crumbly or hard, it should be replaced. Replace and tighten the compressor mount.
Repeat this step for each of the compressor mounts.
Before inspecting the compressor mounts, unplug the refrigerator to avoid an electrical shock hazard. 
