Also:Sounds made by a spirit entity

From the site of the Spiritualist Church of Canada:

Used from a spirit entity, taps were formed into a method of communication - one tap for yes, two for no. The Modern Spiritualism Movement was initiated from the Hydesville experience in 1848 through this preliminary form of communication with spirit. The raps from spirit have been known to be so sophisticated as to make the sound of a match scratching and can be anything from a soft tap to a loud bang.