effects, cold breezes and disturbed The Acoustic Properties of bedclothes (Gauld & Cornell, 1979). Unexplained Rapping Sounds The quality and frequency of rapping sounds vary enormously from isolated BARRIE G. COLVIN single raps to series of raps occurring on a very regular basis. In a small Abstract minority of cases a rapping intelligence has been capable of communicating The wave characteristics of via a code and answer simple unexplained rapping sounds have been questions put to it by those present. studied and compared with similar- Probably the most well-known case of sounding raps produced using normal this type is that of the Fox sisters, tapping methods. Differences in low dating from 1848. This case had a frequency wave properties between profound effect upon the wider public the two classes of raps have been and led to the rise in modern noted. There are indications that the Spiritualism (Gauld, 1968). Other acoustic properties of the two classes similar cases are those of Cideville of sounds are different and that this (Lang, 1904) and Karin (Wijk, 1905). technique can be used to differentiate In more recent times, the Andover between normal and inexplicable case of 1974 consisted of messages rapping sounds witnessed during RSPK being clearly rapped out on a wall and activity. A tentative theory of localised on a bed-head, all in the presence of stress development followed by a investigators (Colvin, 2008). The sudden release of tension has been rapping sounds in this case varied from put forward to account for the rapping light knocks to very heavy bangs, sounds. sufficient to cause the walls of the house to vibrate. Of particular Introduction importance, the position of the raps could be determined and the localized Rapping sounds emanating from an vibrations felt by the principal unknown source have been widely investigators. Furthermore, the quality described in the literature, particularly of the messages was good in that with respect to investigations of there was no ambiguity with regard to apparent recurrent spontaneous specific letters being rapped out using psychokinesis (RSPK) and Spiritualist- a coded format. type sitter groups (Roll, 1976 and Pearsall, 1972). The phenomenon has A literature study of so-called rapping been described in cases covering many poltergeists, together with first-hand hundreds of years and vary from slight and very strong evidence of localised, rapping sounds, scratchings, a inexplicable rapping in the Andover “sawing” sound to thunderous banging case, appears to confirm the notion sounds. RSPK studies, often referred to that sounds of this type seem as poltergeist activity, indicate that as consistent with the hypothesis that many as 50% of all cases include the some rapping-like sounds are not production of rapping sounds, often caused by obvious, conventional accompanied by other phenomena sources. This report looks at the such as object movements, luminous nature of the rapping sounds from an acoustics point of view and is psychologist Alan Gauld of Nottingham described in two parts, an evaluation University was informed of the views of recorded raps from Andover and a of Leon Eeman, a specialist in bio- more general evaluation, involving a circuits and vibrational healing. Eeman, variety of other cases. the author of “Cooperative Healing: The Curative Properties of Human On the basis that unexplained raps do Radiations”, apparently discovered that exist, and that there may be some the sound envelope of inexplicable differences between their acoustic raps rose over time rather than properties and those of normal rapping immediately reaching a maximum sounds, it is worth exploring the intensity and then decreasing. Gauld history of unexplained rapping effects and Cornell also witnessed inexplicable in some detail. This can then be set as rapping sounds first hand during a background against which the results sittings with L.G. in 1959 (Gauld, from the current study can be 1994). Cornell made recordings of the compared. raps, which were later analysed by Wilkinson and Gauld at Nottingham During his investigation of Kate Fox- University (Gauld, 2009). They noted Jencken, William Crookes obtained an that a sound spectrum analysis of the unusual trace on a smoked glass plate raps revealed a curious feature in the when Kate’s hands were placed close lower frequency ranges. The amplitude to the recording apparatus. Each of the sound waves of each rap, movement of the recording needle was instead of beginning at a peak and accompanied by an unusual rapping then dying away, so to speak “worked sound, which Crookes could not up” to a peak over a brief period of explain by normal means (Crookes, time. In essence, this confirmed the 1874). The first audio recordings of views of Eeman, discussed above, and unexplained rapping sounds date from forms the basis of the current work 1915 when mechanical engineer, aimed at determining whether such W.J.Crawford, used a phonograph to views can be verified using more record rapping sounds at a séance in modern techniques applied to a variety Northern Ireland (Crawford, 1916). of rapping sounds from various Crawford was interested in establishing poltergeist cases. whether inexplicable rapping sounds which had been heard by himself and An important series of table-rapping others were in fact truly objective in experiments was carried out in 1959 to nature. He concluded that this was 1961 (Paul, 1963 and Paul, 1963a). indeed the case after having produced The well run tests, which placed three good recordings of such sounds emphasis on minimising the possibility using rather primitive but effective of fraud or other natural causes, apparatus. Naturally, these recordings resulted in the production of clear proved the objectivity of the sounds rapping sounds when in the presence but gave no detailed information about of a non-professional medium. Most of their acoustic properties or how the the raps came from the table, around sounds were generated. Some possibly which sat the group of interested significant information did come to sitters. Some raps came from an area light about forty years later when up to three metres away from the table. The duration of each rap was those displayed on the storage between 3 and 6 milliseconds and oscilloscope. The absence of the efforts were made to determine higher frequencies and harmonics did whether correlations could be found not alter the overall sound envelope between raps and skin temperatures, form or the duration. electrostatic charge, electromagnetic field intensity and ambient particle A similar series of table rapping tests counts using a Geiger counter. In was undertaken in the mid-seventies addition, recordings were made of (Bayless, 1976 and Bayless, 1977). pulse rate, blood pressure, Many of the sounds which were electromyograms and recorded could not be heard at the electroencephalograms. No correlation time of the test but were clearly was found but clear evidence of audible when the tape was played inexplicable raps, sustained over a back at a later stage. Bayless carried period of more than two years was out most of the tests in conjunction reported. with a medium, Mr Wesley Frank but some notable successes were obtained One of the most important studies of when Bayless sat alone. psychokinesis took place in Canada in the 1970s. This enquiry involved the Having established that there may be “Philip” project which has not only some differences between normal and been described in detail (Owen & unexplained raps, at least from Sparrow, 1976) but has also been evidence of the kind presented above, summarised more recently (Charman, I decided to more fully evaluate the 2008). The series of group sittings acoustic properties not only of the around a table involved the production Andover raps, but also raps from cases of unexplained raps that were investigated by other researchers. I recorded and evaluated over a was able to obtain recordings from considerable period of time. Video several poltergeist cases, all of which footage of the events was broadcast could be subjected to acoustic on Canadian television. A detailed analysis. The purpose of this work was analysis of the rapping sounds to examine the notion that generated at the Paul sittings, as well unexplained raps have a fundamentally as those from the Philip group, was different acoustic waveform to raps undertaken by Whitton (Whitton, 1975 produced by normal means. However, and Whitton, 1976). Both sets of in order to appreciate the technical recordings were played back into a aspects of the investigation, it is storage oscilloscope for visual necessary to understand at least the inspection and were permanently fundamentals of acoustic analysis, a recorded using a Brush strip-chart short summary of which follows. recorder running at 125 millimetres per second. It is worth noting that the General Acoustics chart recorder was capable of reproducing frequencies up to 200Hz In order to determine whether only. However, Whitton has pointed inexplicable raps are in any way out that the form and duration of the different to normal rapping sounds, it acoustic envelope were identical to was necessary to fingerprint the rapping sounds using generally- and its pitch. The amplitude is often accepted methods of acoustic analysis. measured in terms of sound pressure In order to understand the procedures level, which is defined as the involved in the current analysis, some difference between the actual pressure understanding of the nature of in the medium at a particular point and acoustics is required. A brief time, and the average pressure of the introduction to the subject is given medium at that same point. As the below, including the important and human ear can detect sounds with a relevant topics of amplitude, waveform very wide range of amplitudes, sound and frequency. pressure is often measured as a level on a logarithmic decibel scale.