Study finds infrasound at MacEwan University raises cortisol and worsens mood

A newly published experiment reports that a tone so low that most people cannot consciously detect it can, within minutes, leave listeners more short-tempered, less engaged, and measurably more stressed.

That familiar sense of unease some people associate with basements is given a possible physical basis here: certain spaces may be affecting the body before the brain can pinpoint why.

A hidden sound signal

In a controlled laboratory room at MacEwan University - a public university in Edmonton, Alberta - researchers embedded a deep, low rumble underneath music and observed a shift in how participants felt.

By recording those changes, Rodney M. Schmaltz, Ph.D., a psychology professor at MacEwan University, provided evidence that infrasound can shape emotional responses even when it goes unnoticed. These low-frequency sound waves sit below the normal limit of human hearing.

Compared with those who listened to music on its own, people exposed to the concealed vibration described themselves as more irritable, less interested, and they perceived the very same music as sadder.

The findings do not demonstrate that every “creepy” space is humming, but they do suggest that building-related noise deserves scrutiny long before any paranormal explanation enters the picture.

Why older buildings hum

Even when they seem quiet and motionless, older buildings can continue to generate low-frequency sound.

Ventilation fans, lift motors, pumps, and pipework can transmit slow pressure waves through walls and floors. These man-made sources sit alongside natural ones such as storms, volcanoes, and meteors.

Because low-frequency waves travel far and can bend around obstacles, a basement might contain vibration that does not register as ordinary audible noise.

At sufficiently high volumes, the boundary around 20 hertz – 20 vibrations per second – becomes less distinct, since extremely low tones can start to be heard.

Stress without awareness

The body is capable of responding to hidden stressors even when our attention never consciously detects them.

Cortisol, a stress hormone, helps the body mobilise energy and adjust immune activity when the brain identifies strain.

A brief increase can be useful for staying alert, but frequent or prolonged elevation can take a toll on sleep, mood, blood pressure, and metabolism.

“This study suggests that the body can respond to infrasound even when we can’t consciously hear it,” said Schmaltz.

Measuring stress responses

The study involved 36 adult students, split into four listening conditions with nine participants in each.

Half of the participants listened to calming music or horror-like ambient audio that also contained hidden infrasound near 18 hertz; the others heard the same material without the infrasound.

The low tone was generated via concealed bass speakers at 75 to 78 decibels, designed to avoid obvious rattling.

To capture biological and emotional effects, the researchers collected saliva samples before the session and again 20 minutes after the music ended, and participants completed mood surveys immediately after exposure.

Infrasound altered mood

Once the low-frequency tone was introduced, the emotional scores shifted in a consistent direction.

Those in the infrasound condition reported greater irritability while listening and reduced interest afterwards.

They also rated the identical music as more sad, despite the audible clips having been designed to sound either soothing or unsettling.

Importantly, participants’ guesses about whether infrasound had been present did not account for the outcome, indicating the effect was not driven by expectation.

Stress hormone response

The physiological data aligned with the self-reports. Salivary cortisol increased when infrasound was included, and after one inadequate sample, 35 cortisol measurements remained for analysis.

The association between cortisol rise and infrasound persisted even when the researchers controlled for irritation, fear, and negative feelings during the listening period.

“Increased cortisol levels help the body respond to immediate stressors by inducing a state of vigilance,” said Trevor J. Hamilton, Ph.D., a MacEwan University corresponding author.

Not quite anxiety

Despite the haunted-building framing, fear was not the dominant response. The clearest changes were irritability and reduced interest rather than anxiety, which limits any sweeping claims about panic.

This nuance implies that an environmental irritant can make a place feel unpleasant without making people explicitly frightened.

From a practical standpoint, the work points away from ghost stories and towards unnoticed building conditions that may be influencing mood.

Questions still remain

As with many small laboratory studies, the experiment can reveal a signal without resolving the entire issue.

Given the limited sample - and the fact that most participants were young women - the results need replication with larger groups spanning different ages, health conditions, building types, and longer exposure periods.

The researchers also used a single pure tone, whereas real environments often combine several low frequencies alongside vibration, airflow, and audible noise.

Engineering quieter spaces

Noise is already treated as a comfort concern in building design, yet low-frequency vibration can slip beneath everyday awareness.

More precise monitoring could help engineers identify troublesome areas near large ventilation fans, heavy motors, boiler rooms, and long pipe runs.

Stronger evidence would also support regulators in deciding whether short-term laboratory effects should inform real-world exposure limits.

“The first priority would be testing a wider range of frequencies and exposure durations,” added Schmaltz.

What this changes

Taken together, mood ratings, saliva data, and the fact that participants largely failed to detect the infrasound offer a physical account of “old-building unease” rather than a purely psychological one.

Next steps include testing real rooms, longer exposures, and mixed frequencies, while keeping the takeaway appropriately restrained: a strange sensation may have a physical cause.