Summary: Humans have a “hidden” sensory relationship with the environment that bypasses conscious hearing. A new study reveals that infrasound, sound waves below 20 Hertz (Hz), can physically alter our bodies without our knowledge.
Even brief exposure to these low-frequency vibrations, which are common near traffic, industrial machinery, and aging ventilation systems, significantly raises cortisol levels and increases feelings of irritability and sadness. These findings provide a scientific explanation for “haunted” feelings in old buildings and suggest that invisible noise pollution may be a silent driver of chronic stress.
Key Facts
- The Invisible Stressor: Participants exposed to 18 Hz infrasound showed a measurable spike in salivary cortisol (the primary stress hormone) and reported feeling more irritable, even though they could not hear the sound.
- Mood Distortion: Infrasound changed how people perceived art; those exposed to the frequency rated music as being significantly “sadder” than those in the control group.
- The “Haunted” Effect: Senior author Rodney Schmaltz notes that infrasound is often found in basements and old buildings due to vibrating pipes. The resulting agitation and anxiety are frequently misattributed to supernatural phenomena.
- Evolutionary Vigilance: Researchers believe the rise in cortisol is an evolutionary adaptation that induces a state of “vigilance” in response to environmental stressors we cannot see, such as distant storms or large predators.
Source: Frontiers
Infrasound is very low-frequency sound, below 20 Hertz (Hz), which humans typically canโt hear. It can come from natural sources like storms, or from anthropogenic sources like traffic. Some animals use it to communicate, while others avoid it.
Scientists investigating humansโ ability to sense infrasound determined that we canโt detect it, but we do respond to it: itโs linked to increased irritability and higher cortisol levels.ย
โInfrasound is pervasive in everyday environments, appearing near ventilation systems, traffic, and industrial machinery,โ said Prof Rodney Schmaltz of MacEwan University, senior author of the article inย Frontiers in Behavioral Neuroscience.
โMany people are exposed to it without knowing it. Our findings suggest that even a brief exposure may shift mood and raise cortisol, which highlights the importance of understanding how infrasound affects people in real-world settings. ย
โConsider 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.โ
Sound of the underground
The scientists recruited 36 participants and invited them to sit alone in a room while either calming or unsettling music was played. For half the participants, hidden subwoofers played infrasound at 18 Hz.
After listening, they were asked to report their feelings, their emotional rating of the music, and whether they thought the infrasound was present. They also gave saliva samples before and after listening. ย
The scientists found that participantsโ salivary cortisol levels were higher if they had been listening to infrasound. These participants also reported feeling more irritable and less interested, and thinking the music was sadder. But they couldnโt tell they were listening to infrasound.
โThis study suggests that the body can respond to infrasound even when we can’t consciously hear it,โ said Schmaltz. โParticipants could not reliably identify whether infrasound was present, and their beliefs about whether it was on had no detectable effect on their cortisol or mood.โ
โIncreased irritability and higher cortisol are naturally related, because when people feel more irritated or stressed, cortisol tends to rise as part of the bodyโs normal stress response,โ said Kale Scatterty, first author and PhD student at the University of Alberta. โBut infrasound exposure had effects on both outcomes that went beyond that natural relationship.โ
Felt but not heard
These results indicate that humans can sense but not identify infrasound, though the mechanism remains unclear. They also suggest we may need to investigate whether prolonged infrasound exposure could impact health through consistently elevated cortisol levels and wellbeing issues related to lowered mood and increased irritability.
โIncreased cortisol levels help the body respond to immediate stressors by inducing a state of vigilance,โ said Prof Trevor Hamilton of MacEwan University, corresponding author.
โThis 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.โ ย
Because the sample was comparatively small, the scientists carried out sensitivity analyses before drawing conclusions from their results. They confirmed that their study could detect moderate to large effects of infrasound, which includes their main findings. However, more research with greater, more diverse participant samples will be needed to fully understand how infrasound influences human emotion and behavior.
โThis study was in many ways a first step towards understanding the effects of infrasound on humans,โ cautioned Scatterty.
โSo far, weโve only tested a specific frequency. There could be many more frequencies and combinations that have their own differential effects. We also only collected subjective reports of how the participants felt after exposure, without directly observing their responses during the trial.โย
โThe first priority would be testing a wider range of frequencies and exposure durations,โ added Schmaltz.
“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. If those patterns become clearer, the findings could eventually inform noise regulations or building design standards.
“As someone who studies pseudoscience and misinformation, what stands out to me is that infrasound produces real, measurable reactions without any visible or audible source. So, the next time something feels inexplicably off in a basement or old building, consider that the cause might be vibrating pipes rather than restless spirits.โย
Key Questions Answered:
A: While your ears don’t “hear” it in the traditional sense, your body’s tissues and internal organs can feel the vibrations. These subtle physical tremors can trigger the brain’s “fight or flight” system (the HPA axis), leading to a release of cortisol as if you were facing a visible threat.
A: This study suggests it might be. While short-term cortisol release helps us stay alert, prolonged exposure to infrasound from traffic or machinery could lead to chronically elevated stress levels, which are linked to heart disease, anxiety, and sleep disorders.
A: Very likely. Many “paranormal” hotspots have been found to have high levels of infrasound caused by wind blowing across a building’s openings or old machinery. This study proves that the “creepy” feeling of being watched or unexplained agitation is a documented biological reaction to 18 Hz frequencies.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- Journal paper reviewed in full.
- Additional context added by our staff.
About this neuroscience and stress research news
Author:ย Angharad Brewer Gillham
Source:ย Frontiers
Contact: Angharad Brewer Gillham โ Frontiers
Image:ย The image is credited to Neuroscience News
Original Research:ย Closed access.
โInfrasound Exposure is Linked to Aversive Responding, Negative Appraisal, and Elevated Salivary Cortisol in Humansโ by Kale R. Scatterty, Dawson VonStein, Lisa B. Prichard, Brian C. Franczak, Trevor J. Hamilton, and Rodney M. Schmaltz.ย Frontiers in Behavioral Neuroscience
DOI:10.3389/fnbeh.2026.1729876
Abstract
Infrasound Exposure is Linked to Aversive Responding, Negative Appraisal, and Elevated Salivary Cortisol in Humans
Introduction:
Infrasound describes sound wave frequencies below 20โฏHz, which are typically imperceptible to humans. Some animals perceive and demonstrate aversion to infrasound, raising concerns about its potential adverse effects as an anthropogenic pollutant.
Recent research suggests humans may also respond to infrasound, despite being below the conventional limit of human hearing. This study explored the non-auditory impact of infrasound on human mood and stress responding.
Methods:
Participants (nโฏ=โฏ36) were exposed to calming or unsettling music with infrasound (~18โฏHz) present or absent in a 2โฏรโฏ2 between-subjects design (calming vs. unsettling, infrasound on vs. off). Self-report measures were collected immediately post-exposure, and saliva was collected immediately pre-exposure and 20โฏmin post-onset for cortisol assay.
Results:
Participants did not detect infrasound above chance (pโฏ=โฏ0.241). Infrasound was associated with elevated salivary cortisol (pโฏ=โฏ0.022, rrbโฏ=โฏ0.390) and higher self-reported irritability (pโฏ=โฏ0.049, ฮท2โฏ=โฏ0.096), disinterest (pโฏ=โฏ0.044, ฮท2โฏ=โฏ0.121; pโฏ=โฏ0.047, ฮท2โฏ=โฏ0.118), and sadness appraisal (pโฏ=โฏ0.002, ฮท2โฏ=โฏ0.253) across both music conditions, with no expectancy effects. Interest, irritability, sadness appraisal, and cortisol were also identified as important predictors of infrasound exposure via random-forest modeling.
Discussion:
Without auditory detection nor expectancy effects, infrasound exposure was linked to elevated cortisol and more negative affective self-reporting. These findings align with previous animal studies and suggest infrasound may be aversive to humans, acting as a potential environmental irritant and contributing to more negative subjective experience.
