Good Vibrations: The Case for a Specific Effect of Infrasound in Instances of Anomalous Experience has Yet to be Empirically Demonstrated more

October 2006] Good Vibrations: The Case for a Specific Effect of Infrasound GOOD VIBRATIONS: THE CASE FOR A SPECIFIC EFFECT OF INFRASOUND IN INSTANCES OF ANOMALOUS EXPERIENCE HAS YET TO BE EMPIRICALLY DEMONSTRATED by Jason J. Braithwaite and Maurice Townsend ABSTRACT A growing number of contemporary investigations into the apparitional experience highlight the importance of energetic/environmental factors underlying such instances. These factors have been ascribed with the capacity to influence the brains, perceptions and interpretations of certain observers. Examples include a suggested role for geomagnetic fields, electromagnetic fields, lighting levels, drafts, temperature and infrasound. In reality only a few of these factors have been investigated in depth and have received empirical support. This paper investigates the recent case put forward for infrasound underlying anomalous perceptions in some instances (Tandy, 2000; Tandy & Lawrence, 1998). Contrary to the growing interest in infrasound, here we question studies that claim to have shown a positive role for infrasound in eliciting strange experience. We re-examine these claims and demonstrations from the original studies, investigate the neuro-physiological mechanisms proposed for the effects of infrasound, and show that the case for specific effects due to infrasound alone has yet to be empirically demonstrated. Implications for future research are also discussed. introduction Let us begin with a well-known puzzle: if a tree falls over in the woods and no one is there to hear it, does it make a sound? When presented with this for the first time many people generate an elaborate series of explanations for why it does make a sound: it is just that as no one is there to hear it, it is simply not heard. However, in contrast to intuition, the correct answer to the puzzle is 'No, it does not make a sound'. The key to solving this puzzle is the combined information of no one being there to experience the falling tree and the word 'sound'. Sound is a perceptual phenomenon, an emerging property of the auditory components of the ear and brain transforming an ambiguous external vibration into the perception of coherent sound. Therefore, in the absence of a human observer, and thus a brain, the falling tree cannot actually make a 'sound'. It is only capable of making a vibration through the air. So out in the real world, events generate vibration (not sound), which is transformed into sound by the ear and brain of the observer. So what does this example mean for the present paper examining the claimed role of infrasound in strange experience? The important point highlighted in this example is that both a physical and a perceptual component underlie the resultant experience of 'sound'. All perceptually audible sound is vibration, but not all vibration is perceptually audible. The point to keep in mind is that objects and events in the world do not actually generate sound; they generate air vibration that is converted and transformed into sound by the human ear and brain. The Chambers Dictionary of Science and Technology (1999) defines infra- sound as "sound or frequencies below the usually audible limit of 20 Hz". In 211 Journal of the Society for Psychical Research [Vol. 70.4, No. 885 reality then, true infrasound is, by this definition, inaudible and should be viewed more accurately as a form of vibration that lies outside the capacity of the human auditory system to respond to it and generate the perception of sound. A more accurate description is that air molecules are displaced and vibrate in a particular way which remains inaudible to the human ear—best summarised perhaps as Inaudible Air Vibration (LAV).1 For the purposes of this article, we take infrasound to mean inaudible sound only (i.e. vibration at frequencies less than 20 Hz and energy levels so low they cannot be explicitly heard as sound). Distinguishing between inaudible infrasound and audible low-frequency sound is perhaps of more importance here to the neuroscientist and psychologist than the physicist and engineer. This is because the moment vibration becomes audible (and thus becomes a perceived sound) a legion of neural responses are initiated that would not necessarily be present in the absence of such stimulation. Therefore, the complex neuro-cognitive landscape is distinct for both situations—which may have consequences for how the energy contained within these components can then go on an exert other biophysical effects (if indeed it does). A further reason is that many experimental studies investigate the effects of infrasound by having the signals at a given percentage above the threshold for hearing—so technically this is not true infrasound, it is merely low-frequency sound of a high energy level (see Haneke, Carson, Gregorio & Maull, 2001, for examples). This is important as the main difference between what we might term here as 'infrasound' and these 'audible low frequency sounds' is the level of energy contained within the signal. Overview of the Present Study We present the first critical appraisal and review of the proposed effects for infrasound implicated in some haunt reports. It is not the purpose of the present study to provide an extensive analysis of all infrasound research. Instead we concentrate on the two primary and original studies of Tandy (2000) and Tandy and Lawrence (1998), which were important contributions to the specific link between infrasound and selective instances of haunt reports/ anomalous perceptions. It is this claim, and the evidence presented to support it, which is re-examined here. In this paper we question the general concept and demonstrations so far provided, in conjunction with the neurophysiological mechanisms proposed for an interaction between infrasound and human experience.2 We also propose an alternative magnetic field account for the data presented in the primary investigations. It is important to be clear that what is questioned is the nature of the evidence so far reported and the mechanisms proposed in support of infra- sound as a sole contribution to some specific experiences. It is concluded that the current evidence for infrasound-induced perceptions is ambiguous. 1 We prefer the term IAV, as it somewhat more accurately describes the crucial physical dimension (rather than the perceptual ones) of the energy under scrutiny. However, to avoid confusion here we will continue to use the term infrasound. 2 Note—It is important to point out that the case for infrasound was not proposed to account for all haunt-type experiences. However, it was proposed as a viable mechanism for some and it is this that we question here. 212 October 2006] Good Vibrations: The Case for a Specific Effect of Infrasound Therefore, a convincing case for infrasound involvement in specific haunt reports has yet to be made. We agree with Tandy (2000) and Tandy and Lawrence (1998) that future researchers would do well to consider how such energies may be implicated in specific cases of haunt-reports. However, we would add that research would be improved further if infrasound were evaluated in concert with other physical variables, most notably magnetic fields, and the viable cognitive neuroscientific mechanisms by which such energies interact with the human brain were more explicitly sketched out. Energetic Aspects of the Haunt Experience Recent research from laboratory studies has shown that exposure to com- plex low-frequency magnetic fields can induce changes in neurophysiology, conscious experience, or both (Bell, Marino & Chesson, 1992, 1994; Bell, Marino, Chesson & Struve, 1991; Cook & Persinger, 2001; Cook, Thomas & Prato, 2004, 2002; Dobson, St Pierre, Wieser & Fuller, 2000; Fuller, Dobson, Wieser & Moser, 1995). A number of investigations have suggested that this mechanism of interaction can elicit many specific experiential components often implicated in spontaneous haunt-type experiences, and studies have successfully induced such states in observers (Cook & Persinger, 2001; Per- singer, 1999; Persinger, Richards & Koren, 1994; Persinger, Tiller & Koren, 2000; Richards, Koren & Persinger, 2000; Richards, Persinger & Koren, 1993). In line with these laboratory investigations a growing number of field-studies have also revealed the presence of magnetically remarkable and complex wave- forms in specific areas associated with haunt-reports in the natural setting (Braithwaite, 2004; Braithwaite, Perez-Aquino & Townsend, 2005; Braithwaite & Townsend, 2005; Roll & Persinger, 2001; Wiseman, Watt, Greening, Stevens & O'Keeffe, 2003; see also Persinger & Koren, 2001). As the types of waveforms seem complex and legion, Braithwaite (2004) introduced the term Experience- Inducing-Fields (EIFs) to refer generically to all manner of magnetic waveforms with the potential capacity to influence the explicit perceptions and conscious awareness of observers. Collectively, the emerging picture is one suggesting that under certain circumstances complex magnetic EIF waveforms may have the capability to influence specific neural/experiential processes in certain individuals. Furthermore, these anomalies could be present at — and differentiate between — locations associated with some haunt-reports (for reviews see Persinger, 1999; Persinger & Koren, 2001). The consequence of this neuro-magnetic interaction is a sympathetic shift in the experiential state of observers which may either subsequently bias their impressions of ambiguous stimuli towards a paranormal interpretation (Houran, 2000; Lange & Houran, 1998,1999, 2001; Lange, Houran, Harte & Havens, 1996), or indeed may induce more elaborate forms of direct sensory hallucination (see Persinger & Koren, 2001). These studies reflect the growing consensus that specific energetic components at certain locations could have an impact upon human experience and may underlie haunt-reports in some cases. The case for magnetic fields underlying some instances of haunt-reports has been well made; however, recent research suggests that other energetic factors may also be crucial. 213 Journal of the Society for Psychical Research [Vol. 70.4, No. 885 The Case for Infrasound Vic Tandy (Tandy, 2000; Tandy & Lawrence, 1998) originally suggested and outlined a potential role for infrasound as underlying some instances of spontaneous haunt reports. Since then the account has gained considerable currency within both the amateur and professional community, with many field-based researchers now considering the importance of infrasound in relation to their own investigations (see, for example, 'Project Haunt' reported by Holt, 2006). Tandy and Lawrence (1998) describe some of the experiences that occurred to one of the authors and how they concluded that the cause was infrasound-induced anomalous perceptions. Some of the crucial details from this study are outlined below. The factory where Vic Tandy worked had a reputation for being haunted, so it is likely most people at this location were aware in some sense of strange happenings. Indeed, cleaners and others had reported odd sensations and experiences while working there (Tandy & Lawrence, 1998). Tandy himself reports instances of feeling strange, depressed, and having cold shivers. On one occasion when he was alone in the factory he experienced a very strong feeling of a 'sensed presence' which was somewhat discomforting. After some time this experience developed into the strong feeling of being watched and that he was not alone. Tandy then reports a figure slowly emerging in his far left visual field. The figure was described as being indistinct, in the periphery of his vision, grey in colour, made no sound and "moved as [Tandy] would expect a person to" (Tandy & Lawrence, 1998, p. 361). Tandy also relates that his hair was standing on end during this experience and he noticed a distinct chill in the air. On turning to face the apparition the figure faded away. On another occasion when Tandy was in the factory he placed a fencing foil blade in a vice (to carry out repairs) and noticed that it seemed to be oscillating in a particular manner which suggested that it was being influenced by some form of 'energy'. Tandy and Lawrence (1998) immediately suggested that this energy was most likely sound, or more appropriately infrasound. Based on some preliminary experiments using the foil blade in a vice at a number of locations within the factory, Tandy reports roughly plotting the energy over space and based on these observations concluded that he was in the presence of a 19 Hz infrasound standing wave. The cause of this apparent standing- wave was later found to be a large defective extraction fan. Indeed, when the fan was switched off, the wave went away (Tandy & Lawrence, 1998). Following on from this initial study, Tandy (2000) investigated a 14th- century cellar in Coventry, and claimed to find crucial levels of infrasound (again around 19 Hz) that existed in the precise areas where observers reported strange experiences. In this later study an attempt was made to directly quantify the infrasound and signal data were presented. The data reported clearly do show a frequency peak at around 19 Hz in the haunted region—as suspected via the rather cruder methods from the original study. This result was taken as further support for the crucial role of infrasound, and a particular frequency component, in eliciting strange experiences. Based on the collective evidence from these studies, the role of infrasound now appears well established among potential energetic accounts for haunt-reports. In 214 October 2006] Good Vibrations: The Case for a Specific Effect of Infrasound contrast, we suggest that severe shortcomings in the methodology, other confounding components within the signal data, and a questionable biophysical mechanism for infrasound to engage with the human brain complicate this interpretation. The Case Against Infrasound in Haunt Reports There are three main problems related to the arguments for infrasound effects implicated in haunt-reports. The first major issue is that of the quanti- fication of the infrasound. In the first study, Tandy and Lawrence (1998) made no attempt to measure the levels of infrasound formally with suitable equipment. Therefore, even if it is accepted, for the sake of argument, that infrasound was the crucial factor, there is no way of knowing to what degree it was present in the factory. In the second study, which did attempt to measure the levels of infrasound formally, Tandy (2000) only measured a weak (38db) 19Hz peak. We know of no current published study that has found any implications for cognition and experience of infrasound as weak as this (indeed, nor does Tandy—see Tandy, 2000; see also Haneke et al., 2001). It is interesting that in the second study, Tandy (2000) actually failed to find amplitude levels any- where near those reported as having implications for experience when formal attempts to measure the degree of infrasound were made. It is odd that Tandy and Lawrence (1998) made no attempt to measure the levels of infrasound with appropriate equipment. Indeed, no actual direct frequency or amplitude measures were provided at all—despite the fact that the arguments rested centrally on amplitude and frequency information. Although the informal attempts using the fencing foil are interesting and warrant further scrutiny, especially in conjunction with the anecdotal reports from the location, there is in fact no evidence from this paper that 'infrasound' itself was responsible for the experiences (even though it may have been present), or if it were, to what degree it was actually present. Infrasound is certainly one possibility, but there are others (which are discussed below). Secondly, it is very puzzling that neither published study actually presented any baseline data, or indeed any formal comparison between the measurements from haunted and baseline areas within the same locations. The issue of baseline measuring is crucial for field-based investigations of this type (for a discussion of the importance of baseline measurements, see Braithwaite, 2004; Braithwaite, Perez-Aquino & Townsend, 2005; Houran & Brugger, 2000). For example, what if the crucial 19 Hz infrasound frequency is present, to similar degrees, in areas that are not associated with haunt reports? What, then, for the theory of infrasound crucially defining only the haunted areas? What a thorough examination of the evidence from Tandy's two investigations suggests is that the researchers basically found infrasound everywhere they measured —but they only measured (or at least only reported) reputedly haunted areas. What the study did show was that a 19 Hz component was present, to a small degree, in a specific area where strange experiences have been reported. How- ever, the absence of any baseline data, which should be viewed as a serious omission, suggests that these findings should be viewed with caution. A third problem relates to the neuroscience claims that are drawn on to offer a basis for infrasound effects to exert their effects on human observers, 215 Journal of the Society for Psychical Research [Vol. 70.4, No. 885 which is also highly questionable. Tandy and Lawrence (1998) suggested that effects could occur via infrasound inducing resonant vibration at a low level in vision, specifically in the human eyeball (an account Tandy suggests for his own experience of seeing an apparition out of the corner of his eye). Tandy and Lawrence (1998) suggest that it would not be unreasonable to assume such resonant vibration could cause a smearing of vision and something like the corner image of Tandy's spectacle frame to become blurred and seen as an apparition. This was the suggested mechanism for Tandy's specific visual experience. There are a number of problems with this suggestion. Firstly, the account does not explain the curious finding as to why Tandy's perceptions were in the periphery of vision and located only to the left side of his visual field (see Tandy & Lawrence, 1998). If the whole eyeball was resonating, the perceptual phenomena would be more widespread across the retina and this would be associated with a general smearing/blurring/distortion of vision impacting across a more predominant area of vision—none of which was described in the experience. So it becomes difficult to see how such a general influence did not induce other perceptual effects, which would be very noticeable, at the same time. It might be argued that the infrasound was only impacting on one part of the eye but these suggestions are also untenable and inconsistent with the concept of resonance—where the induced vibration would influence the entire organ/object. The mechanism of eyeball resonance, if possible, would not have the perceptual effects prescribed to it and recruited by Tandy to explain his own particular and specific visual apparitional experience.3 In addition, if an out-of-focus spectacle frame was responsible for the impression of a figure, this does not explain how the perceived figure was apparently seen to move as a person would move naturally. We find this explanation untenable. Returning to the concept of resonant vibration, a further and perhaps more worrying problem is that eyeball pressure alone does not produce the complex and sustained forms of high-level hallucination that could be interpreted as a human form or figure (as with Tandy's own experience). This is because the lower the level of the hallucinatory activity within the brain (i.e. occurring in the earlier primary sensory areas), the more basic and simple the nature and form of the hallucination itself (i.e. phosphenes and kaleidoscopic phenomena associated with disinhibition in early visual cortical areas: see Kluver, 1966; Penfield, 1955; Penfield & Perot, 1963; Siegal, 1977; Siegal & Jarvik, 1975; Walsh & Pascual-Leone, 2003). Indeed, many of these perceptions can be induced by light pressure on the eyeballs and are often experienced accidentally by people who place too much pressure on their eyes when showering or bathing, for example.4 These low-level contributions to hallucination seem to produce very simple and predictable images, which reveal both the structure and functional interaction of early neural architecture. The mechanism of eyeball resonance for Tandy's own experience seems very 3 Note, however, that infrasound could still be responsible for more general feelings of discomfort and unease—though this would have nothing to do with eyeball resonance. Here we question the specific role of infrasound for this particular visual phenomenon. 4 It is not advised that readers attempt to induce these sensations themselves by applying pressure to the eyeballs as this can cause lasting damage to the eye and its internal structures. 216 October 2006] Good Vibrations: The Case for a Specific Effect of Infrasound unlikely for the particular experience reported. Of course, it might be argued that the energy levels needed to 'smear' vision would be much less than those needed to generate such fleeting low-level hallucinations. So here the suggestion might be one of differences in the levels of energy required in relation to the level of distortion seen. The problem with this is that we have no data on the amplitudes needed to generate this mild 'smearing' of vision. But even if such information were available, again, for the reasons given above, it becomes difficult to see how such a general smearing could be responsible only for a visual effect restricted to the periphery of one visual field. These points lead on to a further issue relating to the actual level of energy contained within the 19 Hz standing wave in order to generate eyeball resonance. Firstly, it is not clear what energy levels are both necessary and sufficient to generate such resonant vibration in the human eyeball. All we were told was that a NASA report suggested 19 Hz as a frequency (a figure not provided by the other studies cited by Tandy), but no level of energy is given. In order to truly qualify as infrasound it would need to be below certain amplitudes (i.e. remain inaudible). For a 19 Hz component to remain inaudible we estimate that it would need to be no higher than approximately 50db. As noted earlier, many more mainstream studies actually assess the effects of infrasound as a percentage above that of actual perceptual hearing — thus containing far more energy than these estimates (see Broner, 1978; Haneke et al., 2001). This can hardly be the mechanism suggested by Tandy (2000) and Tandy and Lawrence (1998) as no actual perception of sound was reported in either study, so presumably in those cases we are dealing with amplitudes less than those that would make such sound audible. This problem is somewhat compounded as, again, no energy measurements were provided by Tandy and Lawrence (1998), only low levels were measured in Tandy (2000), and we have no realistic figure from the experimental studies using true infrasound. It therefore becomes impossible to establish whether the energy that might have been necessary and sufficient to generate a vibration resonance was ever present in the first place (even if we did accept it as a viable mechanism for the experiences reported). In addition, one notable feature of resonant frequencies is that they are typically a very pure, strong waveform, usually a sine wave. It seems very unlikely that such a basic wave could produce complex visual effects like those reported by Tandy and those typical of many spontaneous haunt-type reports. These observations are somewhat problematic for the account proposed. It is interesting to note that in a recent review of all published and empirical studies of the effects of infrasound on humans, no reports of visual/perceptual distortions were reported (Haneke et al., 2001). Furthermore, the most prominent effects of exposure to infrasound occurred at energy levels well above the threshold of hearing and resulted mainly in annoyance and discomfort on the part of the observer. If infrasound alone is capable of inducing neuro-cognitive changes in humans, which may then be recruited into the current experiential state, it would seem that such a low-level and rather crude mechanism as eyeball resonance is not crucial for the more elaborate haunt-reports documented. This means that for the infrasound/haunt-report studies published so far, the actual mechanism 217 Journal of the Society for Psychical Research [Vol. 70.4, No. 885 for an interaction between pure infrasound and higher-level visual neural processes remains obscure. An Alternative Account for Infrasound Effects: A Possible Role for Magnetism and Vibration Induced Magnetic Anomalies In the original account, infrasound effects were proposed to have a direct effect on perception and experience (Tandy, 2000; Tandy & Lawrence, 1998). By this account vibration alone was seen as having the capability to induce experiential changes in observers (via interactions with the human eyeball). However, we suggest that a completely different indirect mechanism could also have been responsible for the experiences reported. This mechanism is 'indirect' in the sense that although contributions from infrasound may well be present, this component itself may not have the capacity to induce high- level hallucination. The active components with the capacity to influence neural processing are not vibration alone. In contrast to infrasound, one primary candidate for the active component is that of complex variability in the localised magnetic field. This magnetic variability may come about by small vibrations occurring in magnetic and ferrous objects which could, on occasion, be induced by the source that is producing the infrasound, or even the infrasound itself. Furthermore, both the studies of Tandy (2000) and Tandy and Lawrence (1998) provide evidence that a magnetic component may have been present in their original investigations. If a magnet or any ferrous object is vibrated, at a given frequency, it will generate distortions and changes in the localised magnetic field that vary in sympathy with the level of vibration.5 In other words, if we vibrate a ferrous object/bar magnet at 19 Hz, we will cause a corresponding distortion in the surrounding Earth's magnetic field which will also consist of a 19 Hz magnetic component. The vibration is needed to generate the magnetic field variability, but it is the resultant magnetic field which may have consequences for human experience. The mechanical vibration such as infrasound itself may have few if any implications for cognition and consciousness, at least at the readily available amplitudes from the natural world. In contrast, weak complex magnetic fields are known to be able to interact with brain processes and influence perceptions (see Persinger, 1999; Persinger & Koren, 2001; Roll & Persinger, 2001). This account can be applied to any ferrous object, all of which might be capable of creating changes in the local magnetic field when vibrated. There are many factors that can produce infrasound vibration in the natural environment, including avalanches, meteors, ocean waves, tectonic and geological movement, volcanoes, severe weather and violent storms (modern artificial contributions can come from transformers, heavy traffic, machinery and factories, etc.; see Bedard & Georges, 2000). Interestingly, many of these natural factors are also associated with independent magnetic anomalies as well which have already been linked to strange experiences and events (i.e. 5 We have conducted unpublished experiments that support this idea using magnets contained within stereo system speakers which can vibrate in line with the auditory signal. These small vibrating magnets also produce mild magnetic field disturbances (in the nanoTesla range) which can easily be measured with appropriate technology. 218 October 2006] Good Vibrations: The Case for a Specific Effect of Infrasound geological fault lines: Persinger, 1985; Persinger & Cameron, 1986; Persinger & Koren, 2001). Although sound and magnetic fields may be considered independently, they may also share some degree of interdependence under certain circumstances. For instance, in the natural setting, whatever is generating infrasound could be in direct mechanical contact with a magnetic or ferrous object being vibrated. Any resultant airborne infrasound would be seen as an actual side effect, and would not necessarily be the neurophysiologically active component. Such low-frequency vibration could indeed be a useful indicator that potent magnetic EIFs may be present. If one measured the environment for infrasound, or magnetic anomalies, some aspect of the component may be measurable with either system. Recent research has reported substantial space-based and time-based magnetic anomalies, some of which can be directly related to the presence of magnetised objects in the localised vicinity of observers (Braithwaite, 2004; Braithwaite, Perez-Aquino & Townsend, 2005; Braithwaite & Townsend, 2005). In relation to one instance, Braithwaite and Townsend (2005) suggested that modest vibrations and movements in the objects responsible for these steep magnetic field gradient anomalies (in this case a magnetised bed support) would generate magnetic signatures varying well over lOOnT (nanoTesla). This area is also associated with striking accounts of haunt-reports. So both the demonstration of highly magnetised objects in the natural living environment, and vibration or movement within them having the potential to generate very complex magnetic anomalies, are not without precedent. If we consider these issues in relation to the observations outlined by Tandy and Lawrence (1998) a quite different scenario from that originally proposed could be present. Tandy and Lawrence noted that a malfunctioning extractor fan (approximately lm in diameter and powered by a lkW electric motor) was generating an infrasound standing wave. This disappeared when the fan was switched off. However, based on the current suggestions, the fan could have been generating at least two forms of varying magnetic field as well. Firstly, the fan would have had an electric motor, which runs from a 50 Hz power supply (50Hz is the UK power frequency). Although a 50Hz sine wave could be considered too simple on its own to produce hallucinations, a motor will also produce lower frequency distortions in the local magnetic field. An electric motor (such as that driving the lm-blade extraction fan; Tandy & Lawrence, 1998) can be considered as a strong permanent magnet being rotated, pole over pole, between the opposing poles of two other permanent magnets. In the real world, all the magnets are electromagnets but the effect is the same. Under these circumstances, a rotating magnetic field is produced, with a frequency reflecting the rotation rate of the motor's armature. In addition to these distortions, the fan blade could also, particularly if unbalanced or faulty, produce secondary vibrations with different frequencies within itself and anything that it is in mechanical contact with (i.e. the fan spindle, bearings, fan housing, the wall, floor, etc.). If any material vibrated by this action happened to be ferrous, this too would vibrate in sympathy and produce magnetic field changes with the same frequencies. Note that all these potential distortions in the magnetic field would also have disappeared when the fan was switched off. Which magnetic factor may have been crucial for the experiences 219 Journal of the Society for Psychical Research [Vol. 70.4, No. 885 (or whether both were), or whether infrasound and these magnetic fields were both contributing, is impossible to say, but, on the growing number of studies showing a prominent role for magnetic fields, the contribution from these factors cannot be ruled out. Therefore, this study does not convincingly demonstrate that infrasound alone was crucial for the anomalous perceptions reported under these circumstances. The data from Tandy (2000) are also interesting with respect to this magnetic suggestion; within the frequency data reported in his Figure 5 there is a 50 Hz peak component (note — the scale is logarithmic). The existence of this peak shows clearly that there is a contribution to the background vibrations of the room from a 50 Hz (and likely electromagnetic) source. We suggest that this is most probably due to an AC transformer in the immediate vicinity and reflects a process of magnetostriction (tiny physical movements in a transformer core caused by a changing electric field). The presence of a powerful transformer is interesting. Although a transformer is not, in itself, likely to produce complex magnetic fields, this 50 Hz component implies extensive use of electrical equipment in the measured area—all of which might have made up a complex magnetic signature. As well as generating a magnetic field, this movement would also generate noise or vibration — it is this vibration component that we suggest Tandy (2000) measured. Consistent with our suggestions for the findings from Tandy and Lawrence (1998), these data support the contention that, along with any infrasound that may have been present, complex EIFs in the immediate vicinity are more than likely. The important points we make here are that sources which produce infra- sound in the environment can produce complex magnetic fields as well — it could be the magnetic field, not the infrasound, which is crucial. Laboratory evidence has shown that complex magnetic fields alone (in the absence of any infrasound or vibration) can influence the perceptions and experiences of observers (see Persinger & Koren, 2001); however, there is no evidence that true infrasound can have the same effects on perception. Collectively, it appears that the empirical demonstrations of a role for infra- sound in haunt-reports are questionable. It seems the case for infrasound is not as straightforward as it might have first appeared. The studies of Tandy (2000) and Tandy and Lawrence (1998) may well have demonstrated that infrasound was indeed present in those environments. However, it remains unclear whether the levels truly were anomalous and typify locations/areas associated with haunt-reports, or whether other interactive factors such as magnetic fields were actually the crucial distinguishing components. The suggested mechanism of interaction between infrasound and the observer for a specific visual apparitional experience also seems very unlikely. The empirical case for infrasound as an energetic aspect to the haunt experience is ambiguous and has yet to be empirically demonstrated. Infrasound: The Future This paper has presented a critical reappraisal of the methods, findings and claims from recent investigations that were interpreted as supporting the claim that infrasound could underlie some specific instances of haunt-reports. The comments raised in this paper are not meant to stifle current efforts at 220 October 2006] Good Vibrations: The Case for a Specific Effect of Infrasound measuring infrasound, but to encourage researchers to consider other possible causes of haunt-type effects while investigating cases. Moreover, these issues question a current and growing perception that a reliable case for infrasound in haunt-type experiences has been made. It has not. The issues raised from the current critique should focus the questions for future research in this field. We make what we see as just a few helpful suggestions below. Firstly, it is clear that infrasound measurements need to be made in a reliable and valid manner, referencing both haunt-areas and baseline areas alike (in line with the suggestions of Braithwaite, 2004 and Houran & Brugger, 2000). A study becomes difficult (if not impossible) to interpret if appropriate baseline measures have not been taken. Furthermore, detailed consideration needs to be given to alternative suggestions when evaluating infrasound data. This is particularly the case with regard to the relationship suggested here between infrasound and magnetic fields, but could extend to other factors as well. It is also important to note that it is not being suggested that every anomalous magnetic field in the natural setting is generated by infrasound vibration. Geological, tectonic, atmospheric and artificial magnetic anomalies can be generated without the need for infrasound vibration to act as a catalyst. How- ever, where considerable infrasound is present, perhaps an assessment of the local magnetic microenvironment, in relation to geology, structure, objects and man-made appliances, would be prudent. In addition, future studies should seek to separate the diverse contributions from magnetic fields and infrasound by measuring both factors simultaneously to assess their relative presence and contribution. The only way to truly disambiguate the current situation is to make simultaneous measurements of both magnetic fields and infrasound waves, at the same place, and at the same time. A high level of shared coherence between aspects of these signatures would suggest a degree of interdependence between these factors. In some cases infrasound alone may be crucial; in other cases the magnetic signatures may be responsible. In further investigations, both could be playing a role (via the suggested infrasound-induced vibration in magnetic and ferrous objects as outlined here) and in yet further instances neither could be important. Only a protocol that employs detailed magnetic and infrasound measures can address all these scenarios effectively and how they may co-occur 'in the wild'. Furthermore, a good deal more thought needs to be given to relevant neuro- physiological mechanisms for how such infrasound could influence ongoing neural processes and impact on perceptual experience. The mechanisms for how such energies are engaging with the individual observer and potentially inducing altered states remains a mystery. The suggested mechanism of eye- ball resonance seems totally insufficient to explain the perceptual anomalies attributed to infrasound and Tandy's own experience. Although it is difficult to speculate as to how infrasound could influence the perceptions of observers, perhaps likely candidates are through interactions with the auditory-vestibular (and possibly even tactile) systems (Broner, 1978; Kuralesin, 1997). Problems here can cause severe instances of loss of balance, nausea, sickness, disorientation and discomfort. Of course, all these factors can occur in the complete absence of any assumed paranormality; however, if they occur within a specific experiential context which is conducive to such 221 Journal of the Society for Psychical Research [Vol. 70.4, No. 885 interpretations (such as prior knowledge or expectation of a haunting) then these sensations may serve as a catalyst for more elaboration on the part of the observer. Therefore, infrasound may have general implications for rather nebulous experiential states, which are modified and elaborated into something more, due to the specific context (i.e. prior knowledge of haunting at the location) at that time (Lange & Houran, 1998, 1999, 2001; Lange et al., 1996). However, such possibilities remain to be investigated. Summary and Conclusions The empirical demonstrations provided so far do not actually conclusively support the sole involvement of infrasound in certain haunt-reports, and thus do not support the contention that it can have the effects ascribed to it (at least as so far demonstrated). It may have been the case that the sound vibrations came from a source also emitting complex magnetic EIFs. By this account it is complex changes in the magnetic field that are the neurophysiologically active components, not the associated vibration that may have given rise to them per se. 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