The Silent Frequency That Makes Old Buildings Feel Haunted

The basement feels wrong before you can say why. Something in the air, maybe, or the quality of the silence. Your mood dips, irritation creeping in from nowhere, and the music playing through the speakers sounds, suddenly, sadder than it did a moment ago. You haven’t heard anything unusual. You haven’t seen anything unusual. But something has changed, and your body knows it even if your brain can’t quite catch up. Researchers at MacEwan University think they know what that something might be: infrasound, the invisible low-frequency hum of pipes and ventilation systems, rattling along beneath the threshold of human hearing.

The study, published this week in Frontiers in Behavioral Neuroscience, is one of the first controlled human experiments to pair verified infrasound exposure with both psychological self-report and a concrete physiological marker, namely salivary cortisol, the hormone we associate with stress. The results were, in a word, unsettling.

Infrasound sits below roughly 20 Hz, the lower limit of what the human ear can ordinarily detect. It’s generated by storms, by volcanic activity, by tectonic rumblings deep in the Earth’s crust, and (this is the part that matters) by the mundane mechanical heartbeat of cities: ageing pipes, HVAC systems, traffic, industrial machinery. “Infrasound is pervasive in everyday environments, appearing near ventilation systems, traffic, and industrial machinery,” says Rodney Schmaltz, senior author and professor at MacEwan. Most of the time, we walk through it without a second thought. The question the team wanted to answer was whether walking through it was actually doing something to us, whether the frequency was registered somewhere below consciousness, somewhere we couldn’t readily name.

Into the Room

The experimental setup was deliberately ordinary. Thirty-six undergraduate students filed one at a time into isolated testing rooms and sat alone with a piece of music, either a calming instrumental or a horror-themed ambient track designed to provoke discomfort. Hidden subwoofers, including a 12-inch unit positioned in an adjacent hallway and a 16-inch speaker oriented toward the ceiling in a neighbouring room, pumped infrasound at approximately 18 Hz into half those spaces. The participants had no idea.

That last point turned out to be rather important. When the team ran the numbers, they found that participants couldn’t reliably identify whether infrasound had been present. Their guesses were, statistically speaking, no better than chance. And according to Schmaltz, participants’ beliefs about whether the infrasound was on had no detectable effect on their cortisol or mood. The physiological response didn’t care what the participants thought was happening. It just happened anyway.

What happened, specifically, was this: those exposed to infrasound reported higher irritability, lower interest in the music, and a tendency to rate the music as sadder, irrespective of whether it was the calming or the horror track. Cortisol levels, measured before and about 20 minutes after exposure, were also elevated. Kale Scatterty, the PhD student who led the work, notes that irritability and cortisol do tend to move together under ordinary stress, but adds that “infrasound exposure had effects on both outcomes that went beyond that natural relationship.”

Not Anxiety. Irritation.

That distinction matters more than it might seem. Previous theories about infrasound and paranormal experience have often leaned on anxiety as the explanatory mechanism, the idea that low-frequency sound triggers a kind of free-floating dread that the mind then reaches for supernatural explanations to account for. The new data don’t really support that picture. Measures of anxiety didn’t budge significantly. What went up was irritability and disinterest, a kind of sour, low-grade aversion rather than fear. That’s perhaps a more honest description of how a lot of ghost stories actually feel in the telling: not screaming terror, but wrong atmosphere, a sense of unease that never quite crystallises into something you can point at.

Schmaltz, who studies pseudoscience and misinformation as part of his broader academic work, draws the connection explicitly: “Consider visiting a supposedly haunted building. Your mood shifts, you feel agitated, but you can’t see or hear anything unusual. In an old building, there is a good chance that infrasound is present, particularly in basements where aging pipes and ventilation systems produce low-frequency vibrations. If you were told the building was haunted, you might attribute that agitation to something supernatural. In reality, you may simply have been exposed to infrasound.”

The mechanism by which infrasound gets inside us without being consciously heard is still somewhat murky. One leading hypothesis involves the otolith organs, small calcium carbonate structures in the inner ear primarily responsible for balance and spatial orientation. Fish use their otoliths to detect infrasound directly (zebrafish, in prior work by some of the same researchers, showed clear aversive behaviour in response to 15 Hz infrasound), and humans still have otoliths, even if our hearing has largely migrated to the cochlea over evolutionary time. It’s possible that infrasonic perception through vestibular pathways was never fully lost, merely sidelined. The vestibular system connects extensively to the limbic system, the brain’s emotional circuitry, which would help explain why the sensation shows up as mood change rather than sound.

The Long Game

The cortisol elevation in the study arose from a single, brief exposure of roughly five minutes. Worth sitting with. Trevor Hamilton, the study’s corresponding author, puts the longer-term concern plainly: “Increased cortisol levels help the body respond to immediate stressors by inducing a state of vigilance. This is an evolutionarily-adapted response that helps us in many situations. However, prolonged cortisol release is not a good thing. It can lead to a variety of physiological conditions and alter mental health.” People who live or work in environments saturated with infrasound, close to wind turbines, in older buildings with persistent mechanical hum, in dense urban cores, might be experiencing something like a low-grade chronic stress response, one whose source they cannot identify or easily remedy.

The study has real limits. Only one frequency was tested: 18 Hz, chosen partly because of prior zebrafish findings and partly because it produced stable, validated signal delivery in the specific rooms used. The sample was small and skewed heavily female, which matters because hormonal variation across menstrual cycles can influence cortisol levels. And real-world infrasound is almost never a single clean tone. “Infrasound in real environments is rarely a single clean tone, and we don’t yet know how different frequencies or combinations affect mood and physiology,” Schmaltz concedes. Meanwhile Scatterty adds: “This study was in many ways a first step towards understanding the effects of infrasound on humans. So far, we’ve only tested a specific frequency. There could be many more frequencies and combinations that have their own differential effects.”

Broader frequency testing and longer exposures are the obvious next steps, and Schmaltz believes the findings could eventually shape building design standards and noise regulations if the patterns hold. In the meantime, the study offers something more modest but still genuinely strange: evidence that you can be measurably stressed by something you cannot hear, cannot feel, and do not know is there. So, the next time a basement makes your skin crawl for no reason you can name, the cause might be “vibrating pipes rather than restless spirits.” Which is either reassuring or, depending on your disposition, somehow worse.

Scatterty et al., Frontiers in Behavioral Neuroscience, 2026. DOI: 10.3389/fnbeh.2026.1729876

Frequently Asked Questions

Can infrasound really make a building feel haunted?

It’s a plausible contributor. The research found that people exposed to infrasound below 20 Hz, sound humans cannot consciously detect, became more irritable, less interested, and rated music as sadder, without knowing why. In old buildings where ageing pipes and ventilation systems generate low-frequency vibrations, someone primed with the idea that the location is haunted might reach for a supernatural explanation for what is, in fact, a physical sensation. The study doesn’t rule out all paranormal claims, but it does offer a testable, physiological alternative worth taking seriously.

Why does infrasound affect mood if we can’t actually hear it?

The mechanism isn’t fully established, but the leading hypothesis involves the otolith organs in the inner ear, structures normally associated with balance that may retain sensitivity to very low frequencies even though human hearing has largely migrated to the cochlea. These organs connect to the limbic system, the brain’s emotional circuitry, which could explain why infrasound registers as mood change rather than as perceived sound. The study confirmed participants couldn’t identify whether infrasound was present, yet their bodies responded measurably anyway, suggesting a route that bypasses conscious auditory perception entirely.

Should people living near wind turbines or busy roads be worried?

The honest answer is that we don’t yet know enough to say definitively. This study used a single 18 Hz tone for roughly five minutes and found measurable cortisol elevation even over that short a window. Chronically elevated cortisol is linked to a range of health problems including sleep disruption and immune function changes, but the specific dose-response relationship for infrasound hasn’t been mapped yet. More research across a range of frequencies and exposure durations is the necessary next step before regulators or individuals can draw firm conclusions.

What’s stopping researchers from just testing a wider range of infrasound frequencies?

Practical constraints, mostly: producing stable, validated infrasound at specific frequencies in controlled lab settings is technically demanding, and each new frequency effectively requires its own experimental design and validation process. The 18 Hz target used here was chosen partly because prior zebrafish studies showed aversive responses around 15 Hz, and partly because the research rooms could deliver that frequency reliably. The team acknowledges this as a significant limitation and identifies broader frequency testing as the clear priority for follow-up work.