This is caused by the rubber pads at the bottom of the compressor being worn out or they have simply become detached from the compressors feet.
Replace them and the banging will stop. You can get the parts at most appliance parts stores.
Please use care when you move the compressor. If you bend or kink any of the lines you will need a service call to repair them.
Please post any other concerns you may have here.
Best regards, XXXXX XXXXX Smithy