Scientific evidence of poltergeist knocking?
A potentially repeatable paranormal phenomenon – if we look for it….
Illustration of the sound pattern of an unexplained rap occurring in poltergeist activity
It is six years since Dr Barrie Colvin published an article ‘The Acoustic Properties of Unexplained Rapping Sounds’ in the Journal of the Society for Psychical Research  Vol 73.2 Number 899 pp 65-93.
Paranormal rappings associated with apparent poltergeist activity have been described for many hundreds of years. But it was not until the 21st century that an interesting and recurrent pattern has been discovered within the fine detail of the paranormal rapping sounds. No explanation has been found for this pattern at present, six years from its identification in existing recordings. The effect emerges from instrumental analysis of sound recordings.
Whereas raps and knocking sounds produced by ordinary means exhibit a normal acoustic pattern, those recorded in alleged poltergeist cases show quite a different sound signature. Crucially, this evidence does not rely on human testimony, but only emerges from instrumental analysis.
Colvin analysed recordings of alleged poltergeist knocking obtained from around the world over a 40-year period. The earliest was a recording made by a local physician at Sauchie (Scotland) in 1960 and the most recent was obtained from a poltergeist case at Euston Square, London in 2000. The samples involved 10 separate recordings recorded on different recording apparatus. Among the samples submitted were recordings made in the famous Enfield poltergeist case in north London during 1977-79. The effect was revealed on the Enfield recordings, some 33 years after they were obtained.
Whilst the two types of rap sound rather similar, they are actually acoustically different, although the effect is only made apparent when the recordings of raps are submitted to detailed analysis. In each of the recordings, when subjected to acoustic analysis, a particular sound pattern is detected which so far remains unexplained.
The essential difference between these raps and those produced by normal means lies in the details of their sound envelope.
In the case of a normal rap, the sound (which often only lasts a few milliseconds) starts loudly and decays over a period of time. The loudest part of the sound is right at the beginning. In the case of a poltergeist rap, the loudest part is near the beginning of the sound – but not at the very beginning. The rapping sound starts relatively quietly and works up to a maximum before it then starts to decay. This effect has been seen in all ten of the poltergeist cases studied.
The raps may be close to the microphone when recorded or at an apparent distance.
The question arises as to how such a sound is generated. There is evidence which points to the sound arising from within the structure of a material rather than from the surface of it, as would be the case with a normally-produced rapping sound.
Dr Colvin stated: “Ever since my personal involvement in the investigation of a rapping poltergeist at Andover, Hampshire, in which it was absolutely clear that no normal explanation could account for the observed phenomena, I wondered whether the recorded raps were in any way different to those produced by normal methods. It is now clear that they are indeed different”.
What is needed now for analysis are fresh samples of alleged poltergeist raps or knocking sounds recorded in ‘haunted houses’ which have been obtained since 2010, to examine if the same pattern may be found.
Dr Colvin’s findings were published in his article ‘The Acoustic Properties of Unexplained Rapping Sounds’ in the Journal of the Society for Psychical Research  Vol 73.2 Number 899 pp 65-93 and the article has also been reproduced in Paracoustics: Sound & the Paranormal (2015) edited by Steven Parsons and Callum E. Cooper published by White Crow Books.