Summary: Humans can respond to low-frequency sound waves called infrasound—below 20 Hertz—even when they cannot consciously hear them. New research shows that brief exposure to infrasound can raise salivary cortisol, increase irritability, and shift emotional perception, suggesting that invisible low-frequency noise in everyday environments may be a hidden source of stress.
These inaudible vibrations are common near highways, industrial equipment, and aging building systems. The study helps explain why people sometimes feel uneasy or “haunted” in older structures and points to infrasound as an underappreciated form of noise pollution with potential implications for mental well-being.
Key Facts
- Invisible but impactful: Exposure to 18 Hz infrasound caused a measurable increase in salivary cortisol and a rise in reported irritability, even though participants could not consciously detect the sound.
- Mood and perception: Infrasound altered how listeners appraised music, leading exposed participants to rate the same pieces as significantly sadder than unexposed listeners.
- “Haunted” sensations explained: The senior author notes that infrasound commonly originates from vibrating pipes and ventilation in basements and older buildings, which may produce agitation often misattributed to supernatural causes.
- Evolutionary response: Researchers suggest the cortisol increase reflects an ancient vigilance response to unseen environmental threats, but prolonged activation could harm health.
Source: Frontiers
What is infrasound? Infrasound refers to sound wave frequencies below 20 Hz that most people cannot hear. It occurs naturally in storms and earthquakes and is also generated by human activities such as traffic, industrial machinery, and building ventilation. Some animals use infrasound for communication or avoid it, and mounting evidence shows humans can react physiologically even without conscious detection.
The research team found that although people typically cannot detect infrasound, their bodies and emotions can respond to it: short exposure raised cortisol, increased irritability, and produced more negative appraisals of emotional stimuli.
“Infrasound is pervasive in everyday environments — from ventilation systems to heavy traffic,” said Prof Rodney Schmaltz of MacEwan University, senior author of the Frontiers in Behavioral Neuroscience article. “Many people encounter it unknowingly. Our results show that even brief exposure can alter mood and elevate stress hormones, highlighting the need to study infrasound’s real-world effects.”
Experimental setup
The study recruited 36 participants who listened alone to either calming or unsettling music. Hidden subwoofers produced infrasound at approximately 18 Hz for half of the participants. After the listening session, participants completed self-report measures about their mood and the music, and provided saliva samples before and about 20 minutes after exposure to measure cortisol changes. Participants were also asked whether they believed infrasound had been present.
Results showed increased salivary cortisol and higher ratings of irritability and sadness among those exposed to infrasound. Participants rated the music as sadder and reported less interest and more agitation, yet they could not reliably identify when infrasound was present. Expectation or belief about exposure did not account for the physiological or mood changes.
“The findings indicate the body can react to infrasound without conscious hearing,” Schmaltz explained. Kale Scatterty, the study’s first author, noted that infrasound produced effects on both cortisol and reported mood that were not solely explained by their usual correlation—suggesting a direct influence of low-frequency vibration on affective and endocrine responses.
Felt but not heard
The mechanism behind human sensitivity to infrasound remains unclear. The researchers propose that tissues and organs can register subtle vibrations, which may trigger the hypothalamic–pituitary–adrenal (HPA) axis and release cortisol as if responding to a threat. While short-term cortisol release supports vigilance, chronic elevation is associated with negative health outcomes such as cardiovascular risk, disrupted sleep, and anxiety disorders.
Because the study sample was modest, the authors performed sensitivity analyses and confirmed their protocol could detect moderate to large effects. They emphasize that further research with larger, more diverse samples and a broader range of frequencies and exposure durations is needed to determine long-term consequences and practical implications for building design and noise regulation.
“This work is an important first step,” Scatterty cautioned. “We tested a single frequency and relied on post-exposure reports rather than continuous observation. Future studies should explore multiple frequencies, combinations, and longer exposures to better understand how infrasound shapes mood and physiology.”
Schmaltz added: “In real environments, infrasound rarely occurs as a single pure tone. If we map out how different frequencies and mixtures affect people, the findings could one day inform standards for noise control and building systems. For now, when a basement or old house feels eerie, consider vibrating pipes rather than restless spirits.”
Key Questions Answered:
A: Even without conscious hearing, the body’s tissues and organs can sense subtle vibrations. Those mechanical sensations may activate the brain’s stress systems (HPA axis), triggering cortisol release and a vigilance response similar to that produced by visible threats.
A: This study suggests it could be a concern. Short-term cortisol increases help with alertness, but repeated or prolonged exposure to infrasound from traffic or machinery may contribute to chronically elevated stress levels that are linked to cardiovascular problems, sleep disruption, and anxiety.
A: It’s a plausible explanation. Many locations identified as paranormal hotspots have elevated low-frequency vibrations from wind, structural resonances, or old equipment. This study demonstrates that 18 Hz infrasound can produce measurable biological and emotional reactions that may be experienced as eerie or supernatural.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- Journal paper reviewed in full.
- Additional context added by editorial 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 comprises frequencies below 20 Hz that are typically outside human hearing. Animal studies show aversive responses to infrasound, raising questions about its effects as an environmental pollutant. Emerging human research indicates non-auditory effects on mood and physiology; this study examined those responses.
Methods:
Thirty-six participants experienced calming or unsettling music while infrasound (~18 Hz) was either present or absent in a 2×2 between-subjects design. Self-reports were collected immediately after exposure, and saliva samples were taken before exposure and 20 minutes after onset to assess cortisol.
Results:
Participants did not detect infrasound above chance. Infrasound exposure was linked to elevated salivary cortisol and higher self-reported irritability, disinterest, and sadness appraisal across music conditions. Random-forest modeling identified interest, irritability, sadness appraisal, and cortisol as important predictors of infrasound exposure.
Discussion:
Even without conscious detection, infrasound was associated with measurable increases in cortisol and more negative affect. These findings align with animal evidence and suggest infrasound can be aversive to humans, potentially acting as an environmental irritant that worsens subjective experience and, with prolonged exposure, may affect health.