Sounds heard in a "haunted" house are often very normal sounds, for example footstep-like sounds can be caused by vermin such as squirrels or raccoons. Dead vermin can also cause unusual smells often associated with hauntings. Doors closing by themselves can be caused by wind. Moving shadow figures can be caused by the headlights of passing cars shining through a window. Many times normal sounds that come from outside can be mistaken for a sound inside the house. Sounds made by electronics, plumbing, refrigerators, and heating / air conditioning have also been mistaken for paranormal sounds.