Knocking Noise

Hi:

I have a 9 month old refrigerator that is making a knocking noise every time I open and close the refrigerator or freezer door. Whirlpool sent our three separate companies to evaluate the problem. Two say it is a defect in the manufacturing proceess because they did not put enough insulation in the cabinet. The other is saying the noise is normal and likely a "damper"?

I have a hard time believing that this noise is normal. Whirlpool of course does not want to do anything about the problem.

Any suggestions?