Why is my Refrigeration appliance making noises?

It is not unusual to hear noises from refrigeration appliances, especially when the appliance is switching on or off. The refrigeration motor may hum whilst in operation. Clicking may be heard as the thermostat turns the compressor on and off. Cracking may be heard when the auto-defrost or frost free setting is in operation. Our highest noise emitting Refrigeration appliance measures at 42dB which is described as the equivalent noise level to a quiet conversation or flowing stream (so it really isn't loud at all).