A new study has found that a sound too low for most people to hear can make listeners more irritable, less engaged, and biologically more stressed after only minutes of exposure.
The finding gives that uneasy basement feeling a physical explanation, pointing to rooms that may unsettle the body before the mind can recognize a cause.
A hidden sound signal
Inside a controlled room at MacEwan University, a public university in Edmonton, Alberta, a low rumble hidden beneath music changed how people felt.
By tracking those reactions, Rodney M. Schmaltz, Ph.D., a psychology professor at MacEwan University, helped show that unnoticed infrasound could still influence emotional reactions. These low-frequency sound waves fall below the usual human hearing limit.
People exposed to the hidden vibration reported more irritability, less interest, and a sadder impression of the same music than people who heard music alone.
The result does not prove that every eerie room is vibrating, but it makes building noise a serious suspect before the story turns supernatural.
Why older buildings hum
Old buildings keep making low sounds, even when they seem still.
Ventilation fans, elevator motors, pumps, and pipes can send slow pressure waves through floors and walls. These sources overlap with natural ones such as storms, volcanoes, and meteors.
Because low-frequency waves can travel long distances and pass around barriers, a basement can hold vibration that never sounds like an ordinary noise.
At very high volume, the boundary near 20 hertz – 20 vibrations per second – becomes fuzzy because very low tones can become audible.
Stress without awareness
The body can react to hidden stressors even when attention never catches them.
For the body, cortisol – a stress hormone – helps release energy and adjust immune activity when the brain flags strain.
Short bursts can help someone stay alert, but repeated elevation can wear 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
Thirty-six adult students took part, with nine assigned to each of four listening conditions.
Half heard calming music or horror-like ambient sound with hidden infrasound near 18 hertz; the rest heard the same music without it.
Hidden bass speakers produced the tone at 75 to 78 decibels without creating obvious rattles.
Saliva samples taken before and 20 minutes after the music gave the team a biological readout, while surveys captured mood right after exposure.
Infrasound altered mood
Emotional ratings moved in one clear direction after the low tone entered the room.
Participants exposed to infrasound reported more irritability during the music and less interest afterward.
They also judged the same music as sadder, even though the audible clips were either calming or unsettling by design.
Crucially, their guesses about whether infrasound was present did not explain the effect, so expectation was not driving the result.
Stress hormone response
Biology backed up the mood reports. Salivary cortisol rose in the infrasound condition, and one poor saliva sample left 35 usable hormone measurements.
The rise remained linked to infrasound even after the researchers accounted for irritation, fear, and feeling bad during exposure.
“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
Fear did not dominate the pattern, despite the haunted-building hook. Irritability and disinterest stood out more than anxiety, which keeps the findings from becoming a broad claim about panic.
That distinction suggests an irritant can make a room feel unpleasant without making someone feel openly afraid.
In practical terms, the study points less toward ghost stories and more toward unnoticed building conditions that may impact mood.
Questions still remain
Small experiments can reveal a signal without settling the whole case.
With such a small group – most of them young women – the results need larger tests across ages, health conditions, building types, and longer exposure times.
Researchers also tested only one clean tone, while real rooms often mix several low frequencies with vibration, airflow, and audible noise.
Engineering quieter spaces
Building design already treats noise as a comfort issue, but low-frequency vibration often escapes everyday attention.
Better measurements could help engineers find problem spots near large ventilation fans, heavy motors, boiler rooms, and long pipe runs.
Clearer evidence would also help regulators decide whether short-term laboratory effects translate into real-world exposure limits.
“The first priority would be testing a wider range of frequencies and exposure durations,” added Schmaltz.
What this changes
Evidence from mood ratings, saliva samples, and failed detection guesses now gives the old-building unease story a physical explanation rather than a purely psychological one.
Useful next steps will test real-world rooms, longer exposures, and mixed frequencies, while keeping the main warning modest: a strange feeling can have a physical source.
The study is published in Frontiers in Behavioral Neuroscience.
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