Refrigerators often make noise during the course of normal operation. Depending on the individual model, you may hear a wide assortment of hums, whirrs and vibrations as the compressor turns on and off to keep the refrigerator at the appropriate temperature. Louder noises such as banging are cause for more concern, especially if the noise is out of the ordinary. If you're hearing a banging noise in the fridge, it may have one of several causes.
Open the fridge and verify that nothing fell inside the fridge. Check around the fridge to look for anything that may have fallen around or behind the appliance.
Check the defrost condensing pan. If it is out of place, a banging noise could result. Reset the pan to its normal position.
Inspect the tubing going into the fridge. If the tubing is touching each other, the vibration could cause a sound. Separate the tubes.
Look at the condenser fan motor blade. If it is hitting something, it makes a banging noise. Make sure the fan is unobstructed.
Move the fridge farther from the wall if it is touching the wall. A vibrating backing against the wall can result in noise.
Have the compressor looked at by a professional if a banging noise still is occurring. A broken compressor can result in banging, and the unit needs to be replaced.