Some hauntings are very noicy. One may hear scratchings, knocks, whistles, even spoken words. What are these? What is going on?
A part from the obvious explanations of these noices - pranks, hoaxes, rats and other smallish animals, underground water, old houses making their natural noises, etc etc - there are one other, not so obviously natural explanation. The poltergeist.
As with ghosts, there are several explanations of exactly what a poltergeist is. The German word 'poltergeist' means "noicy spirit" and has become a blanket term for various paranormal phenomena which usually have in common that they include unexplainable noices as well as psychokinetic phenomena (the link is to a picture of a floating brick at the ruins at Borley rectory, 1944).