How Does Insulation Work in a Refrigerator?
Usually made of rigid foam, refrigerator insulation material traps air in its cells, which slows the transfer of heat from the warm outside of the refrigerator to the cold interior. The more effective the insulation, the less energy the appliance uses to stay cool. In addition to energy savings, the insulation prevents condensation from forming on the outside of the unit. Keeping the air inside the unit dry, it also prevents ice buildup in the freezer.
As insulation technology improves, foam thickness decreases. Because the insulation has become so thin, many newer refrigerators make noises that old units didn't. Sounds you hear when the house gets quiet can include humming, knocking and clicking. While your refrigerator might sound sick, these sounds are usually normal. While a malfunctioning fridge might make a strange noise, the sound is usually accompanied by other more tell-tale symptoms, such as cooling failure and interior condensation or ice buildup.