If your house is giving you the creeps because of popping noises from inside the walls and up in the attic, you can probably chalk it up to something other than spirits from beyond the grave. Popping is a common way to describe a variety of noises that a house makes, and the causes are varied. They range from the completely natural sounds of a house to problems you will need to address. Learning the various causes of these noises will let you know what, if anything, you need to do to stop it.
If your house was built recently or if it is very old, it will go through a process known as settling. These are minor adjustments that the house makes as it adjusts to the shape of the ground under the foundation. The settlement may never completely end, and the occasional pop caused by stress or movement on joists, joints and the various components of the house are completely normal as long as the walls and ceiling do not develop major cracks. If they do, you may need a structural engineer to inspect the home to see if it needs to have piers installed to support it.
Sometimes popping sounds begin when hot water is turned on somewhere in the house. As hot water moves through PVC pipes, they expand. If the pipes were installed with minimal room to grow and shrink, the pipes could be rubbing against the wood of the structure in the walls, ceilings or floor. This may be described as the sound of a ping-pong ball bouncing on the wall from the other side. This is not usually a major problem, and the pipes will not necessarily suffer any damage from this rubbing, but it may be worth it to widen holes or otherwise insulate the pipes to prevent the noise since it is not technically "normal."
Popping noises may sound like they are coming from walls when the sounds are actually travelling down the air ducts throughout the house. The popping can sound pretty loud as warm air expands or cool air shrinks the metal ductwork, causing them to pop. You can always use a hammer to knock a dent in ducts that move too easily to make them more rigid and less likely to pop.
As the temperature in your house goes up and down, the materials used to build your house expand and contract with the heat and cold. Often this expansion and contraction causes popping sounds in the wood or other materials. This is why many people notice the things that go "pop" in the night. The house is quieter as people sleep and the house is rapidly cooling in absence of the sun.
One problem that could be causing a popping sound in your walls or in the attic is pests. Mice, rats, birds or other animals may have entered the home and are chewing, digging and pecking on the interior of your home from the attic or inside the walls. This is a problem that can lead to damage in the home and it must be remedied as soon as possible by calling an exterminator or an animal-removal service.