When Science and the Supernatural Overlap
Among the most scientifically grounded theories in paranormal research is the infrasound hypothesis — the idea that certain low-frequency sound waves, below the threshold of human hearing, can produce physical and psychological effects that mimic classic "haunting" experiences. It's a theory that deserves serious attention from anyone interested in understanding unexplained phenomena.
What Is Infrasound?
Infrasound refers to sound frequencies below approximately 20 Hz — below the normal range of human hearing. While we can't consciously hear infrasound, our bodies can detect it. At certain frequencies and intensities, infrasound has been shown to produce a range of physiological and psychological effects:
- Feelings of unease, dread, or awe
- Disorientation and confusion
- Visual anomalies — including the sense of seeing something in peripheral vision
- The feeling of a "presence" nearby
- Physical symptoms including nausea, chills, and hyperventilation
Infrasound is produced naturally by earthquakes, ocean waves, severe weather, and certain geological formations. It can also be produced by industrial machinery, HVAC systems, vehicle traffic, and even certain architectural features that create resonance at low frequencies.
The Vic Tandy Experiment
The most cited piece of evidence for the infrasound-haunting connection comes from engineer Vic Tandy, who in 1998 published a paper in the Journal of the Society for Psychical Research documenting his experience at a reportedly haunted laboratory in Coventry, England.
Tandy and colleagues had been experiencing feelings of anxiety, malaise, and the sense of being watched in a particular room. Tandy discovered by accident — while working on a fencing foil that began vibrating for no apparent reason — that the room had a standing wave at 18.98 Hz. This frequency was being produced by a newly installed extractor fan. When the fan was modified, the experiences in the room ceased.
The frequency of roughly 19 Hz is particularly significant because it corresponds to the resonant frequency of the human eye — theoretically capable of causing visual vibrations that the brain may interpret as seeing something that isn't there.
Implications for Paranormal Investigation
The infrasound hypothesis doesn't necessarily debunk hauntings — it reframes the question. If infrasound can cause a person to genuinely perceive something, that perception is real to them. The debate becomes: what is actually happening, and what is the brain adding?
For investigators, the practical implication is clear: infrasound measurement should be part of any rigorous investigation toolkit. Detecting a standing wave or low-frequency anomaly in a reportedly active area is significant data, regardless of your interpretation.
How to Detect Infrasound
Standard audio equipment doesn't capture infrasound because most microphones roll off below 20 Hz. To detect infrasound in the field, investigators need:
- Infrasound microphones — Specialized condenser microphones with extended low-frequency response
- Spectrum analysis software — Programs like Audacity (free) can visualize frequency data, though capturing infrasound requires appropriate hardware
- Infrasound meters — Purpose-built instruments for measuring low-frequency sound pressure levels
Other Environmental Factors Worth Investigating
Infrasound is part of a broader picture of environmental factors that may contribute to haunting experiences. Electromagnetic field exposure, carbon monoxide (which at low levels causes hallucinations), geomagnetic disturbances, and even mold (which can affect cognition) have all been proposed as contributing factors in some cases. A thorough paranormal investigation is also, necessarily, a thorough environmental investigation.
The Bottom Line
The infrasound hypothesis is one of the strongest scientifically testable explanations in paranormal research. It doesn't explain every reported experience, but it provides a credible mechanism for some of the most commonly reported sensations associated with hauntings. Understanding it makes you a better, more rigorous investigator — whatever your ultimate conclusions.