Cutting edge

Apparitions exist, there is no question in my mind that the phenomena described as apparitions are real. But what are they? For more than a century, the Society for Psychical Research has collected reports of hauntings.

Last year the society's journal carried a paper written by Tony Lawrence and me that marked the beginning of my research. It provides an explanation for an apparition that had scared me witless. Working late one night, I had a disturbing feeling of presence, as if I was being watched. I became cold, found it hard to concentrate. A shadow drifted across my shoulder and slowly formed into a misty grey figure. I had seen how shaken the cleaner was when she described a presence in this same room a few days previously. I fought to put features to this thing, which was between the door and me, so I couldn't leg it! The half dozen or so neurons that had not already taken cover in the densest part of my skull were reminding me that I worked with anaesthetic agents. If this experience was due to a leak, I was in danger and must get to fresh air immediately, I clung to that thought and turned to face the thing.

it disappeared.

There were no anaesthetic agents in the room. By chance, however, the following day I discovered that there was a low-frequency standing wave of air caused by an extractor fan. The point of maximum energy coincided with where I was sitting. The wave's frequency was in a band that could cause hyperventilation, perhaps by making the lungs vibrate, and visual disturbance. We are all sensitive to light and dark in our peripheral vision, so it is no surprise to find this figure as with many apparitions, was grey.

After my paper was published, a woman told me that in the winter she felt depressed and often mistook a strange dark form for her old dog. It would approach the chair but disappear when she turned to stroke him. Her son had noticed that the chair was near a radiator; when he sat in it there was a perceptible vibration from the central heating pump. With the chair away from the pump, the woman felt better and the apparition ceased.

The evidence collected by the Society for Psychical Research tends to suggest haunted places rather than haunted people. One adult sufferer of night terrors, which can give the impression of being involved in a paranormal event, had noticed that a particular room in the house was much more likely to evoke an episode than any other. Doctors felt his condition serious enough to refer him to a sleep clinic, but while away from home the condition ceased. The man's father discovered that his son's room was being subjected to low frequency sound: 30 cycles per second (Hz) modulated by another wave at 2 Hz of substantial amplitude. The source was traced to a bank of massive extractor fans.

The effects of low-frequency sound (infrasound) on people are controversial, but I suspect some of the experiments that show no effect may be looking at different parameters. One experiment was reported as finding no effect on physiological parameters (heart rate, etc) in the presence of infrasound.

However, subjects reported feeling colder even though the environment was monitored and temperature controlled. This statistically significant result did not feature prominently in the paper. I suspect lower levels of infrasound than have previously been considered do affect us, and this is where my research is focused. It will never explain all apparitions, but it could provide insight into some other inexplicable human experiences.

Vic Tandy, School of International Studies and Law, Coventry University.

Low-frequency sounds may affect people in unexpected ways. They could also explain the appearance of apparitions 'A shadow drifted across my shoulder and formed into a misty grey figure. I fought to put features to this thing, which was between me and the door, so I couldn't leg it' CUTTING EDGE