First, buy 500 cans of expanding foam from your local DIY store. Second, close all the doors and windows in your kitchen or whichever room the fridge is located. Third, drill a hole the same size as the tube on the expanding foam canisters in your one of the doors you have just closed. (At this point in your repair, you MUST NOT be in the same room as your fridge, but the other side of the door). Finally, following the instructions on the side of the expanding foam canisters, insert the tube through the drilled hole. Continue to discharge expanding foam from all the canisters (one at a time) until foam begins to appear back through the hole. Let the foam set for a few hours and you will find that you will no longer be able to hear the banging noise from the fridge.
h2pob
July 2009