Clicking sounds within the walls can be annoying, particularly if they occur during the night when you are trying to sleep. Beyond being bothersome, they can also indicate trouble inside of the walls that requires immediate attention. If you hear a persistent clicking sound inside of your walls, try to trace down the cause and resolve it.
Clicking sounds in the walls may be the result of thermal expansion in copper or polyvinyl chloride piping, causing it to pop or crackle when hot water passes through it. It may make the same sound again as it contracts and returns to the ambient temperature. The clicking noise you hear is the hot-water pipe rubbing against a stud or joist as it expands and contracts. The problem can be fixed by replacing the clamps that secure the pipe to the framing. In most cases, however, the expense of opening the wall to do so may not be worth it.
Heating ducts sometimes make clicking sounds when the heating system comes on or after it goes off. This may be due to expansion and contraction as the duct heats up and then cools off again or a loose piece of metal in the ductwork that moves when forced air blows through it. A brace that does not secure the heat duct properly also may be at fault. Call a licensed heating and air conditioning contractor to inspect the system and find the cause of the clicking noise.
Clicking or rustling sounds within the walls may indicate the presence of carpenter ants. The ants may hollow out the wood in your walls to build nests, particularly in areas behind the walls where wood may water-damaged, such as around bathroom sinks or under roof leaks. The sound the ants make, which is similar to the crinkling sound of cellophane, is how the carpenter ants communicate with each other. Exterminators sometimes use a stethoscope placed on the wall to listen for this sound when trying to locate a carpenter ant nest.
Audible clicking or popping sounds located in the wall behind or near an electrical wall outlet may indicate a problem with the wiring. It could be due to a loose wire or a broken connection. Other signs that the noise may be caused by an electrical problem include flickering in the appliances plugged into the wall outlet, such as a lamp plugged going on and off or dimming. Other indications include not being able to turn off a device plugged into the outlet and getting shocked when inserting a plug into the outlet. Locate and turn off the breaker to the outlet and call a qualified electrician to inspect it because it could cause an electrical fire.