Infrasound, Carbon Monoxide and Other Causes of a Haunted Feeling

Many hauntings involve no apparition at all. What people describe is a feeling: dread in one particular room, the sense that someone is watching, a sudden chill or shiver, a headache that lifts on leaving the house, a movement glimpsed at the corner of the eye. These experiences are real to the people who have them, and they are often shared by several members of a household or by visitors who knew nothing of a place's reputation.

Because such feelings are physical, researchers have asked whether something in the environment could be producing them: sound too low to hear, a gas that cannot be smelled, magnetic fields, drafts and temperature changes, or simply the power of suggestion. Each of these has been proposed, and some have been tested in the laboratory and in reputedly haunted buildings.

The results are mixed, which is itself useful to know. Some explanations are well supported for some cases; others are popular but weakly tested; none explains every report. This article walks through the best-known candidates and what the evidence shows, starting with an engineer who found his ghost in a fan. Along the way it covers one cause that should always be checked first for safety reasons, because it can kill.

Vic Tandy was an engineer working in a laboratory belonging to a medical equipment company in England, a room his colleagues said was haunted. He described feeling cold, sweaty and depressed there, with a sense that something else was present, and at one point he saw a grey shape at the edge of his vision that vanished when he turned to look at it. Later, Tandy, a keen fencer, clamped a fencing foil in a vise to work on it and noticed that the blade was vibrating with nothing touching it. He suspected sound. Measurements found a standing wave of about 19 hertz, below the range of human hearing, generated by a newly installed extractor fan and strongest near his desk. Once the fan was dealt with, the vibration stopped, and so did the uneasy feelings.

Tandy and the psychologist Tony Lawrence published the account as "The Ghost in the Machine" in the Journal of the Society for Psychical Research in 1998. They suggested that infrasound near this frequency might make the eyeball vibrate and smear vision, which could produce a grey shape at the edge of sight. That remains a speculation rather than an established effect.

Tandy went on to measure other reputedly haunted places, including a cellar beneath Coventry's tourist information center, and reported infrasound in some of them. His story does not show that infrasound causes hauntings in general. It shows a plausible mechanism, found by someone curious enough to follow a vibrating blade.

On 31 May 2003 two concerts in the Purcell Room in London put the idea to an audience test. Some pieces were laced with an inaudible tone of about 17 hertz and others were not, and the audience did not know which. The project brought together the composer and engineer Sarah Angliss, the psychologists Richard Wiseman and Ciarán O'Keeffe, and acoustic scientists from the National Physical Laboratory including Richard Lord. Listeners reported somewhat more unusual experiences, such as unease, sorrow, chills down the spine and nervousness, during the pieces with infrasound. The organizers treated the result as tentative, not least because everyone in the hall knew the experiment involved infrasound.

In 2009 the psychologist Chris French and colleagues at Goldsmiths, University of London, published the results of the Haunt project, in which 79 volunteers each spent 50 minutes in a specially built chamber while being exposed to infrasound, complex electromagnetic fields, both or neither. Many reported odd sensations, but the number had nothing to do with the conditions. Instead it tracked scores on a questionnaire about unusual everyday experiences, and the authors concluded that suggestibility was the simplest explanation.

A small 2026 study led by the psychologist Rodney Schmaltz at MacEwan University in Canada played music to 36 volunteers; half of them were also exposed, without being told, to an 18 hertz tone below the range of hearing. They could not tell whether it was playing, but those exposed reported more irritability and had higher levels of the stress hormone cortisol. The emerging picture is that infrasound may nudge mood, while there is little evidence it creates apparitions on its own. Wind, traffic, machinery, pumps and old ventilation systems all produce it.

In 1921 the ophthalmologist William H. Wilmer published a case in the American Journal of Ophthalmology about a family he called Mr. and Mrs. H. After moving into a new home they suffered headaches and listlessness, heard bells and footsteps in the night, felt strange sensations and saw figures that were not there. The cause turned out to be a defective furnace that was sending its fumes into the house instead of up the chimney. Once it was repaired, the family recovered and the "haunting" ended. The paper is often cited as an early record of carbon monoxide producing experiences that people interpreted as supernatural.

Carbon monoxide is a colorless, odorless gas produced when fuel burns incompletely, in furnaces, boilers, water heaters, stoves, fireplaces, generators and engines. At low levels it causes headaches, dizziness, weakness, nausea, tiredness and confusion that are easily mistaken for flu. Poisoning can also cause hallucinations and a sense of dread, and at higher levels it kills.

This is real safety advice, not folklore. If you have fuel-burning appliances and anyone in the house has unexplained headaches, dizziness or nausea at home, or feels a presence that seems tied to one house or one room, check for carbon monoxide before anything else. Fit carbon monoxide alarms near sleeping areas and on every level of the home, test them, and have appliances, flues and chimneys checked regularly. If an alarm sounds, or several people feel ill at once, get everyone into fresh air and call emergency services. A working carbon monoxide detector belongs in every investigator's kit.

Cold spots are a staple of haunting reports, and most buildings have them: drafts from gaps around windows, doors and floorboards, chimneys that pull air, uninsulated walls, stone stairwells and cellars. A thermometer or thermal camera often shows a cold spot sitting exactly where cold air enters. Noises have ordinary sources too. Wood, metal and pipes expand and contract as temperatures change through the night, producing creaks, knocks and ticks; water pipes can bang when a tap closes; and mice, squirrels and birds move inside walls and roofs.

Magnetic fields are a popular suspect, partly because many ghost hunters carry meters to detect them. In the 1980s and 1990s the neuroscientist Michael Persinger reported that weak, complex magnetic fields applied to the head, using a device nicknamed the God helmet, could produce a sense of presence. In a double-blind replication published in 2005, Pehr Granqvist and colleagues at Uppsala University in Sweden found that the experiences were unrelated to whether the field was switched on and were better predicted by suggestibility; Persinger disputed their method. The question of what an EMF meter actually measures matters for exactly this reason.

Suggestion runs through all of these findings. People who expect a place to be haunted notice more, interpret more and remember more, which is why a careful investigation records what witnesses knew about a building before they arrived.

A believer and a skeptic can agree on a sensible order of checks, starting with the one that matters for safety:

• Test for carbon monoxide, and fit an alarm if there is none.
• Note when and where the feeling happens. Does it follow the time of day, the heating cycle, a fan, the wind, traffic or a neighbor's machinery?
• Look for sources of low-frequency sound and vibration: fans, pumps, boilers, ventilation ducts, nearby roads, rail lines or industry.
• Map temperatures and drafts, especially around reported cold spots.
• Ask whether experiences happen at night, in bed or at the edge of sleep, where sleep paralysis is a strong candidate.
• Record what each witness had heard about the place before their experience.

If the feeling remains after all of that, it deserves to be written down honestly as unexplained. Unexplained is not the same as proven paranormal, but it is not nothing either, and it is the point at which the most interesting investigations begin.