If you are disturbed occasionally by things that go pop in the night inside your home, there is not likely much to be worried about. Most likely you aren't dealing with ghosts. Your house could be making popping noises for many reasons, and generally it is nothing to be concerned about. Still, if you think you'd feel better knowing the source of these house noises, then you can investigate to see if one of the most common sources is the actual cause of the popping.
One of the most common causes of popping noises in a house is the heating and air conditioning unit. As the warm or cool air blows through the ducts throughout your home, the sheet metal in the ducts can expand and contract. Some ducts will make a loud popping sound when this happens. This sound does not cause any damage to the system and will not interfere with the efficiency of the unit. You can stop the noise by crawling under the house and finding the pieces of metal where the sound originates. Sometimes tapping a small dent into the metal will make it more rigid and less likely to pop.
Popping noises can occur as the result of wood subfloors. This is especially noticeable in old houses and can be a nuisance to people who have recently moved into one. The subfloor may not be attached properly to the floor joist or the structure may not be strong enough. The noise may happen anytime, but is most likely when people are walking around. Pulling up the flooring and screwing the subflooring to the joists tightly may reduce or eliminate the noise.
Warming and Cooling
If you notice popping noises in the house in the mornings or at night, then the problem may simply be the temperature change of the structure. Most homes are built using wood frames. As the morning sun rises and the house begins to warm, the wood expands. This can cause significant popping in the frame. Vinyl siding tends to do the same thing. At night, the wood and siding can contract as the house cools, resulting in the same situation.
A steady tapping or popping sound is common in many homes. This is generally caused by the expansion of plastic plumbing when hot water runs through it. The expanding pipes often make contact with wood or other building materials close by. The same sound may occur as the pipes cool off after hot water is used.