By Dr. Joel Ramsey, The Paranormal Professor

For centuries, people have described feelings of unease in certain locations. A chilling sensation. The sense of a presence nearby. Shadows moving at the edge of vision, or a strange ripple effect, as if the air itself is vibrating. These experiences are real. The people who report them are not imagining things, and they are not foolish for taking them seriously.

What I've learned over more than fifteen years of evidence-based paranormal investigation is that understanding why these experiences happen doesn't diminish them. It deepens them. And one of the most fascinating explanations I've encountered in the field has nothing to do with spirits at all.

It has to do with sound we can't hear, and with what our bodies do in response to it anyway.

What Is Infrasound?

Infrasound refers to sound waves with frequencies below 20 Hz, lower than the threshold of human hearing. We can't consciously detect these vibrations, but our bodies respond to them in ways that are measurable, documented, and deeply relevant to paranormal investigation.

Infrasound is generated by both natural and human-made sources. On the natural side there is wind moving through valleys or around buildings, seismic activity, ocean waves, and even large animal vocalizations like those of elephants and whales. On the human-made side there are HVAC systems and ventilation ducts, heavy traffic, industrial machinery, building resonance, and plumbing and drainage systems.

That last one matters more than most people realize, and I'll come back to it.

The Vic Tandy Discovery

The idea that infrasound might account for some reported hauntings entered the scientific literature in April 1998, when British engineer Vic Tandy published a paper titled "The Ghost in the Machine" in the Journal of the Society for Psychical Research, written with Dr. Tony Lawrence. The events behind that paper had taken place years earlier in a medical equipment laboratory in Coventry, and the story is worth telling in full because it illustrates exactly how rigorous investigation works.

The laboratory had a reputation. Staff reported feelings of unease, cold sensations, and visual apparitions, a gray, shadowy figure appearing at the edge of vision. One night, working late, Tandy experienced it himself. He felt a sudden, oppressive dread. His chest tightened. And in his peripheral vision, a gray, translucent figure appeared to be forming beside him.

He turned to face it directly. It vanished.

Most people would have left the building. Tandy, being an engineer and a fencer, went home and came back with a foil.

He clamped the blade in a vice, and it began vibrating wildly, oscillating back and forth with no visible force acting on it. Then he did the thing that turned an oddity into a finding. He carried the clamped blade around the room and watched what happened to it. In the center of the laboratory the vibration was violent. At the edges of the room it stopped entirely. That is the signature of a standing wave, a sound wave reflecting off the walls and doubling back on itself to create fixed zones of maximum and minimum energy.

A sound wave reflecting between two parallel walls doubles back on itself and stands still. Air motion is fixed at zero against the walls, the nodes, and greatest at the center, the antinode. A room roughly nine meters long, about thirty feet, supports a standing wave near 19 Hz. This is why Tandy's blade shook violently in one spot and not at all in another, and it is also why room dimensions belong in your investigation notes.

Instruments confirmed it. The room contained a standing wave at 18.9 Hz, and the source was a newly installed extractor fan. Nineteen hertz mattered to Tandy because it sits close to a frequency at which the human eyeball has been reported to resonate, and eyeball resonance would produce precisely what the staff had described: shadows moving in peripheral vision, translucent shapes, the unsettling sense that something is present but not quite visible.

Tandy had the fan modified. The infrasound stopped. And so did the experiences.

How Infrasound Affects the Human Body

Infrasound does measurable things to people. At frequencies between roughly 18 and 20 Hz it has been associated with eyeball vibration and the visual disturbances that come with it, including peripheral shadows, ripple effects in vision, and the appearance of translucent figures. Below 20 Hz more broadly it has been linked to activation of the body's fight-or-flight response, producing unexplained fear, chest pressure, and difficulty breathing. In the 5 to 10 Hz range it can disrupt inner ear balance, causing dizziness and the sense that a space is simply wrong. At various low frequencies it affects the vestibular system in ways that can produce the perception of a nearby presence.

These are not supernatural effects. They are physiological responses to environmental stimuli we cannot consciously perceive. And they feel absolutely real to the people experiencing them, because they are.

What the Research Actually Shows, and Doesn't

Here is where I have to be careful, and where a great deal of paranormal writing on this subject is not.

Infrasound has become a popular explanation in the investigation community, repeated so often that it now circulates as settled fact. The evidence is more complicated than that. In 2006, Jason Braithwaite and Maurice Townsend argued that the specific case for infrasound as a cause of haunt-type experiences was weak, and their central criticism is one every field investigator should take personally. There is almost no baseline comparison data. Investigators measure infrasound at locations that already have haunted reputations, find it, and treat that as confirmation, but nobody has systematically measured how often infrasound turns up in buildings where nothing has ever been reported. Without both halves of that comparison, the hypothesis rests on a positive-test fallacy, which means we go looking only where we expect to find something and then treat finding it as proof.

Then in 2009, Christopher French, Usman Haque, Rosie Bunton-Stasyshyn, and Robert Davis published the Haunt Project in the journal Cortex. They built a chamber for the express purpose of manufacturing a haunted room, and they placed seventy-nine participants in it for fifty minutes each, exposing them to infrasound, complex electromagnetic fields, both, or neither.

Participants reported plenty of anomalous sensations. Dizziness was common, a sense of presence was common, and a small number reported outright terror. But the sensations did not track the infrasound. Participants exposed to it reported no more than participants who weren't, and the researchers concluded that suggestibility, the simple fact of having been told that something might happen, accounted for the results more economically than any environmental variable did.

I include this because it is true, and because leaving it out would make me guilty of exactly what I criticize in the wider field, which is treating a favored explanation as a conclusion rather than as a hypothesis that still has to earn its place. The honest summary is this. Infrasound is real, it is measurable, it demonstrably affects the human body, and Tandy's original case remains a genuinely elegant piece of investigation in which removing the source removed the phenomena. Whether infrasound reliably produces haunt-type experiences on its own, apart from expectation and suggestion, has not been demonstrated under controlled conditions.

That distinction matters enormously for how we use it in the field. Finding infrasound at a location does not explain what happened there. It identifies a variable that has to be accounted for.

Phase 2 of RCIP: Testing for Infrasound in the Field

In my Ramsey Communication-Based Investigation Protocol, Phase 2 requires systematically establishing an environmental baseline before drawing any conclusions about a reported experience, and infrasound testing is a critical part of that baseline. I've described the full protocol and the reasoning behind each phase in Speaking Paranormal, Part Two: The Tools of Responsible Investigation.

I use a professional-grade condenser microphone capable of capturing frequencies below 20 Hz, connected to audio recording software with spectral analysis capability. Most consumer-grade equipment filters out low frequencies automatically, which means standard ghost hunting tools will never detect this particular variable no matter how long you stand in the room holding them. During investigations, I set up the microphone in locations where phenomena are reported, record continuously for extended periods, analyze the recordings for frequency patterns, and correlate any infrasound spikes with the experiences witnesses have described.

If consistent infrasound is present, the next step is identifying its source.

Case Study: The War History Museum Basement

A group of paranormal investigators contacted me about a local war history museum. They had been conducting regular investigations there and were convinced the basement was haunted.

What they reported was consistent and compelling. A pervasive feeling of unease whenever they entered the space. One investigator repeatedly experienced a ripple effect in their vision, almost as if the air itself was vibrating. The sensations intensified near specific areas of the basement. Traditional equipment, EMF detectors and spirit boxes, produced no significant results. They wanted me to investigate and help them understand what they were experiencing.

I brought my professional recording equipment and set it up to capture audio across multiple floors, spending extended time in the basement where the phenomena were most concentrated. I didn't tell the team what I was specifically testing for, because I wanted their observations to remain uninfluenced by my hypothesis. Given what the research says about suggestion, that precaution was not optional.

What the recordings revealed was striking. There were consistent infrasound spikes in the basement, and they correlated directly with bathroom use on the upper floors. Every time someone used a toilet or ran water in the sinks upstairs, the vertical drainage pipes, which converged in the basement before exiting to the municipal sewer system, produced low-frequency vibrations as water rushed through them. The basement amplified these vibrations. The older metal pipes were acting as resonance chambers, creating standing waves of infrasound at approximately 18 to 19 Hz, precisely the frequency range associated with eyeball vibration and visual distortions.

I want to state the conclusion carefully, because the careful version is the defensible one. I did not prove that the plumbing caused the investigators' experiences. What I established is that a substantial environmental variable was present in that basement, that it operated in the frequency range associated with the exact sensations being reported, that it had a mundane and traceable source, and that it correlated in time with when the phenomena occurred. That is enough to say the basement was not a controlled environment and that no paranormal conclusion could responsibly be drawn from what happened there. It is not enough to say a ghost was ruled out by pipes. Those are different claims, and the difference is the whole discipline.

Presenting the Findings

When I gathered the team and walked them through the spectral analysis, showing the correlation between bathroom use and infrasound spikes, the responses were varied, and I want to be honest about that because it reflects something important about this work.

Some members of the team were immediately engaged. They asked thoughtful questions about frequency, resonance, and what this might mean for other locations they had investigated, and they left with a new tool and a deeper understanding of how physical environments shape human experience.

Others were not ready to accept the findings. They had felt something real in that basement, something that mattered to them, and an explanation involving drainage pipes didn't feel adequate to the weight of what they had experienced. I understand that response. I genuinely do. The experiences they had were real. The unease, the visual distortions, the sense of presence, none of that was fabricated. And when something feels that significant, it can be deeply unsatisfying to hear that pipes were in the room.

What I try to communicate in those moments is this. Identifying a source is not the same as dismissing an experience. Understanding that infrasound was present doesn't erase what they felt, it gives them a way to account for it, and that account is in some ways more remarkable than a ghost, because it reveals how profoundly the physical environment shapes human perception in ways we cannot consciously detect.

Why This Matters

I apply rigorous methodology in my investigations because I believe that if genuinely unexplained phenomena exist, we will only find them by ruling out everything explainable first. Every location declared haunted because of bad plumbing or a poorly ventilated HVAC system makes it harder to take seriously the cases where no environmental explanation can be found. The same is true in reverse, though. Every location declared explained because someone found a low-frequency reading and stopped investigating does the same damage from the other direction.

This isn't about proving ghosts don't exist. It's about doing the work carefully enough that when something genuinely resists explanation, we can say so with confidence.

The investigators at that museum were not wrong to trust their experiences. They were right to take them seriously and to seek out someone who would investigate with rigor. What I hope they took away was not disappointment, but a more complete picture of how human beings experience the world, and a methodology they can carry into every investigation that follows.

How to Test for Infrasound in Your Own Investigations

If you conduct paranormal investigations, incorporating infrasound testing will strengthen your work considerably.

You'll need a professional-grade condenser microphone such as the RODE NT1 or a comparable model, an audio interface like the Focusrite Scarlett series, and recording software capable of spectral analysis. Audacity is free and works well for this purpose.

Set up your microphone in locations where phenomena are reported and record continuously for thirty to sixty minutes. Analyze the recordings by examining the frequency spectrum for activity below 20 Hz, correlate any spikes with the timestamps of reported experiences, and then work on identifying likely sources, whether that's HVAC systems, plumbing, nearby traffic, structural resonance, or the dimensions of the room itself. Common sources worth checking include ventilation systems, older metal plumbing and drainage pipes, buildings near busy roads or rail lines, and long hallways or rooms with specific dimensional ratios that can create standing waves.

One more piece of technique, borrowed directly from Tandy. If you suspect a standing wave, map it. Take readings at the center of the room and at the walls, because a standing wave will show dramatic variation across a space while a general noise floor will not. Where the effect is strongest should also be where the reports cluster. If it isn't, you have not found your explanation.

And if you do find consistent infrasound, resist the urge to announce that you've solved the case. You've found a significant variable, and you should also record who knew what was being tested, what the witnesses had been told beforehand, and what they expected to feel. Whether the variable accounts for everything reported at that location is a separate question, and one worth continuing to investigate.

The Deeper Lesson

Infrasound is real. Its effects on the human body are documented. It is present in a great many buildings that have acquired reputations. Whether it is the engine behind those reputations, or one contributor alongside expectation, architecture, lighting, temperature, and the stories people carry into a room with them, is still an open question, and I would rather say so than pretend otherwise.

What is not in question is the obligation. We owe it to the people who trust us with their experiences to look carefully before we conclude anything, in either direction.

What I've found, over and over again, is that rigorous investigation doesn't make paranormal experiences less meaningful. It makes the genuinely unexplained ones more credible. And it gives the people who come to me something more valuable than a ghost story: an honest account of what happened to them, and why.

If you have ever walked into a building and immediately felt that something wasn't right, the question was never whether your experience was real. It was. The question is what produced it, and answering that question honestly, without deciding the answer in advance, is the whole of responsible investigation.

That is what evidence-based investigation is for.

Sources

Tandy, V., & Lawrence, T. R. (1998). The ghost in the machine. Journal of the Society for Psychical Research, 62.

Tandy, V. (2000). Something in the cellar. Journal of the Society for Psychical Research, 64.

Braithwaite, J. J., & Townsend, M. (2006). Good vibrations: The case for a specific effect of infrasound in instances of anomalous experience has yet to be empirically demonstrated. Journal of the Society for Psychical Research, 70, 211–224.

French, C. C., Haque, U., Bunton-Stasyshyn, R., & Davis, R. (2009). The "Haunt" project: An attempt to build a "haunted" room by manipulating complex electromagnetic fields and infrasound. Cortex, 45(5), 619–629.

Diagram by the author.

Dr. Joel Ramsey is a paranormal research scientist and certified investigator with a Ph.D. in Communication from Regent University. He applies the Ramsey Communication-Based Investigation Protocol (RCIP) to unexplained phenomena and has been conducting evidence-based investigations for more than fifteen years.

If this article interests you, the full framework behind it, including additional case studies and the complete RCIP protocol, appears in his book The Paranormal Professor: Investigating Belief, Perception, and the Unexplained, available here. He also speaks regularly to libraries, museums, historical societies, community groups, and paranormal conferences on perception, belief, grief, and responsible investigation. For investigation inquiries or speaking engagements, contact him at paranormalprofessor@yahoo.com.

Related reading

• The Spooky Science Behind Ghost Photos: A History of Spectral Trickery and Modern Misunderstanding

• Why Every New Home Feels a Little Haunted

• Speaking Paranormal, Part One: The Language of Contact

• Speaking Paranormal, Part Two: The Tools of Responsible Investigation