Summary: Humans have a subtle, non‑conscious sensory connection to low‑frequency sound that bypasses ordinary hearing. New research shows that infrasound — sound below 20 Hertz (Hz) — can alter physiology and mood without conscious detection. Short exposures to these deep vibrations, common near heavy traffic, industrial machinery, and aging ventilation systems, produced measurable increases in cortisol and raised reports of irritability and sadness. These findings offer a plausible physical explanation for “haunted” sensations in older buildings and point to invisible noise pollution as a potential contributor to chronic stress.
In controlled tests, people exposed to an 18 Hz tone showed elevated salivary cortisol, reported greater irritation, and judged music as sadder than participants who were not exposed, despite being unable to tell whether the infrasonic tone was present. The research highlights how low‑frequency sound in everyday environments may produce real physiological and psychological effects even when it is not consciously perceived.
Key Facts
- Invisible stressor: Exposure to 18 Hz infrasound produced a significant rise in salivary cortisol, the body’s main stress hormone, while listeners were unable to consciously detect the sound.
- Mood effects: Participants exposed to infrasound rated the same musical pieces as sadder and reported greater irritability and disinterest than unexposed participants.
- “Haunted” sensations explained: Infrasound is often present in basements and older buildings where pipes and ventilation systems vibrate. These low‑frequency vibrations may cause agitation and anxiety commonly misattributed to supernatural causes.
- Evolutionary perspective: Researchers suggest elevated cortisol may reflect an evolved vigilance response to unseen environmental threats, but prolonged activation of this response could be harmful to health.
Source: Frontiers
What is infrasound?
Infrasound refers to sound frequencies below 20 Hz that typically fall beneath human hearing thresholds. Natural sources include storms and earthquakes; human sources include heavy traffic, industrial equipment, and building ventilation systems. While some animals use low frequencies for long‑range communication or avoid them, humans do not consciously hear infrasound in routine contexts. This research examined whether the body nevertheless responds to it.
Researchers led by Prof. Rodney Schmaltz of MacEwan University and colleagues tested whether brief exposure to an 18 Hz tone changes mood and stress physiology. They note that infrasound is ubiquitous in many everyday locations and that people are often unknowingly exposed to it.
Study design and findings
Thirty‑six participants sat alone in a room and listened to either calming or unsettling music while subwoofers, hidden from view, either produced infrasound at 18 Hz or remained silent. Participants provided saliva samples immediately before the session and 20 minutes after the infrasound onset, and completed questionnaires rating their feelings and the music’s emotional tone. They were also asked whether they believed an infrasound source had been present.
The study found that participants exposed to infrasound had higher salivary cortisol, reported greater irritability and disinterest, and judged the music as sadder, compared with those not exposed. Importantly, participants were not able to identify infrasound presence above chance, and expectation about whether it was on did not influence cortisol or mood outcomes.
“The body can react to infrasound even when people do not consciously hear it,” Schmaltz explains. Kale Scatterty, the first author and a PhD student, emphasized that the effects on irritability and cortisol went beyond the usual relationship between mood and stress hormone levels, indicating a direct association with the infrasonic exposure.
Implications and limitations
These results suggest humans can sense infrasound non‑auditorily — feeling its vibrations in tissues or internal organs — which may trigger the body’s stress systems (for example, the hypothalamic‑pituitary‑adrenal axis) and elevate cortisol as part of a vigilance response. While short‑term cortisol release helps respond to immediate threats, sustained elevation is associated with adverse outcomes such as increased cardiovascular risk, anxiety, and disrupted sleep.
The authors caution that this was an initial, relatively small study focused on a single frequency and short exposure. They performed sensitivity analyses indicating the study could detect moderate to large effects, but they call for future research with larger, more diverse samples, varied frequencies, and longer exposure periods. Real‑world infrasound rarely occurs as a single pure tone, and different frequencies or combinations may produce distinct effects. Clarifying these patterns could eventually inform building design and noise regulation to protect public health.
As an investigator who studies misinformation, Schmaltz points out the practical value of these findings: when people feel unexplained unease in basements or old buildings, mechanical sources such as vibrating pipes are a plausible, measurable cause rather than supernatural forces.
Key Questions Answered:
A: Even though infrasound is below conscious hearing, the physical vibrations can be transmitted through tissues and organs. These subtle tremors can activate the brain’s stress systems, leading to cortisol release as if facing a perceived threat.
A: The study suggests it could be. While brief cortisol increases are adaptive, chronic exposure to infrasound from traffic or machinery could contribute to sustained stress responses that are linked to cardiovascular disease, anxiety, and sleep disturbance. More research is needed to quantify long‑term risks.
A: That is plausible. Many locations associated with paranormal reports also contain elevated low‑frequency sound caused by wind, building openings, or old machinery. This study demonstrates that infrasound can produce the unsettling sensations often described in such contexts.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- Journal paper reviewed in full.
- Additional context added by staff.
About this neuroscience and stress research news
Author: Angharad Brewer Gillham
Source: Frontiers
Contact: Angharad Brewer Gillham – Frontiers
Image: The image is credited to Neuroscience News
Original Research: Closed access. “Infrasound Exposure is Linked to Aversive Responding, Negative Appraisal, and Elevated Salivary Cortisol in Humans” by Kale R. Scatterty, Dawson VonStein, Lisa B. Prichard, Brian C. Franczak, Trevor J. Hamilton, and Rodney M. Schmaltz. 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 refers to sound frequencies below 20 Hz that are usually imperceptible to human hearing. Some animal species detect and avoid infrasound, prompting concern that human exposure to anthropogenic low‑frequency noise may have adverse effects. This study tested whether infrasound has measurable non‑auditory impacts on human mood and stress physiology.
Methods:
Thirty‑six participants were assigned to a 2×2 between‑subjects design: calming versus unsettling music, and infrasound on versus off (approximately 18 Hz). Self‑report measures were collected immediately after exposure, and saliva samples were taken immediately before exposure and 20 minutes after onset to assay cortisol.
Results:
Participants did not detect infrasound above chance. Infrasound exposure was associated with elevated salivary cortisol and higher self‑reported irritability, disinterest, and sadness appraisal across music conditions. No expectancy effects were observed. Random‑forest modeling identified interest, irritability, sadness appraisal, and cortisol as relevant predictors of exposure.
Discussion:
Despite a lack of conscious detection, infrasound exposure produced measurable physiological and affective changes. These outcomes align with animal research indicating aversion to low‑frequency sound and suggest infrasound may act as an environmental irritant that influences subjective experience. Further research is required to map frequency‑specific effects, longer exposures, and implications for public health and building design.