Acoustic analysis of inexplicable banging noises recorded during alleged poltergeist activity shows a different sound signature from ordinary banging noises, according to a paper by Dr Barrie Colvin in the latest SPR Journal.
Dr Colvin analysed 10 separate recordings of alleged poltergeist knocking sounds obtained from around the world over 40 years, from a 1960 case in Sauchie, Scotland, to one in Euston Square, London, in 2000, and including recordings made in the famous Enfield poltergeist case in north London during 1977–79. Though the two types of rap sound rather similar, they are actually acoustically different, and acoustic experts have been unable to replicate the pattern of the alleged poltergeist raps.
In the case of a normal rap, the sound (which often only lasts a few milliseconds) starts loudly and then decays; while in the case of all the poltergeist raps, the loudest part is near the beginning of the sound, but not at the very beginning. There is evidence suggesting the sound arises from within the structure of a material rather than from its surface, as would be the case with a normally produced rapping sound.
Dr Barrie Colvin BSc, PhD: “The Acoustic Properties of Unexplained Rapping Sounds” (Journal of the Society for Psychical Research, 2010, vol.73.2 no.899, pp65–93).