A refrigerator keeps your food cold, and it shouldn't disturb the peace of your home very much. Occasionally, you'll hear a loud noise coming from the kitchen and realise your appliance is making a racket you can't identify. Usually there isn't much need for concern. The fact is, refrigerators make all kinds of noise. Some indicate problems, while others are normal sounds of operation. Distinguishing between the two is important so you'll know whether repairs are needed.
If your refrigerator is making a loud chirping or squealing sound, open the door to the freezer compartment and see if the sound seems much louder. If so, it's likely you're dealing with a faulty evaporator fan. The evaporator fan is the device that keeps air moving near the cooling coils in the freezer. This fan is responsible for pushing the cold air throughout the refrigerator. Unfortunately, when this fan motor begins to fail, the only real option is to replace it. It cannot be simply lubricated or repaired easily, so the best option is to have a technician replace it entirely.
Ii you find that a chirping, squealing or other unusually loud noise is coming from behind the refrigerator, it's possible the compressor is failing. This is the most serious repair you'll have to make, because the unit must be replaced and can cost quite a lot. Often, people choose to buy an entirely new refrigerator instead, especially if the current model is an older, inefficient type. The compressor is encased in a large box, usually mounted on the lower back of the unit. If the noise is definitely coming from this football-sized case, then the compressor is the problem. If not, it's possible that the defrost timer or condenser fan motor in self-defrosting models is malfunctioning.
If the noise is coming from underneath the refrigerator and it sounds like a rattling, then the problem is minor. In some refrigerators, the normal vibration of the unit can cause the drain pan mounted underneath the refrigerator to rattle. Some tape to hold the pan in place should be enough to stop the noise.
From time to time, the refrigerant used in the refrigerator cycles through the piping, moving from the pipes that course through the walls of the food compartments to the coils on the back of the unit and then back to the freezer area. As this refrigerant moves, it turns from a gaseous state to a liquid state and back again. As this happens, some refrigerators will produce a gurgling sound that is audible as far away as another room in a quiet house. This is normal in some units and is not a cause for concern.
If you have been startled by a sudden muffled crashing sound coming from the kitchen, don't worry. It's probably not a ghost -- but it could be your refrigerator's icemaker dumping a fresh load of ice into the bin. This is especially noticeable if the ice bin is empty or near empty.