We have all been there (at least once in our lives). When everyone in the house is asleep, you hear a strange hum from the walls. You lean in, only to jump at a sudden thud from the attic. Your heart starts racing. All the tormented spirits from the movies you have watched are turning the ordinary night into something sinister. Regardless of how smart or rational you are, fear seeps in. And all you can think of are the ghosts, spirits, and something truly eerie lurking in the shadows. But guess what? The real culprit has nothing to do with any paranormal activity! In fact, you are listening to something you can’t even hear!A recent study published in Frontiers in Behavioral Neuroscience claims that the ghosts in the attic and goblins in the basement are not responsible for paranormal activity! You should actually blame the old pipes for those things that go bump in the night.
You can’t hear it
Humans cannot hear infrasound, which is a very low frequency sound, below 20 Hertz (Hz). This sound can come from natural sources like storms or from anthropogenic sources like traffic. While some animals use it to communicate, others avoid it. The researchers who investigated humans’ ability to sense infrasound noted that we can’t detect it, but somehow respond to it. It is often linked to increased irritability and higher cortisol levels.“Infrasound is pervasive in everyday environments, appearing near ventilation systems, traffic, and industrial machinery. Many 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,” Prof Rodney Schmaltz of MacEwan University, senior author of the article, said in a release.“Consider 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.”
How the infrasound messes with your body
The study involved 36 participants, who were invited to sit alone in a room while either calming or unsettling music was played. Half of the participants were subjected to the 18Hz infrasound from hidden subwoofers. They reported their feelings, their emotional rating of the music, and whether they thought the infrasound was present. Saliva samples were also collected before and after listening to the infrasound.These participants’ salivary cortisol levels were higher. They also reported feeling more irritable and less interested, and thinking the music was sadder. But they couldn’t tell they were listening to infrasound.“This study suggests that the body can respond to infrasound even when we can’t consciously hear it. Participants 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,” Schmaltz said.Kale Scatterty, first author and PhD student at the University of Alberta, added, “Increased irritability and higher cortisol are naturally related, because when people feel more irritated or stressed, cortisol tends to rise as part of the body’s normal stress response. But infrasound exposure had effects on both outcomes that went beyond that natural relationship.”
Felt, but not heard
The findings confirm that though humans can sense the infrasound, they cannot identify it, and the mechanism remains unclear.“Increased cortisol levels help the body respond to immediate stressors by inducing a state of vigilance. This 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,” Prof Trevor Hamilton of MacEwan University, corresponding author, added.So, you can finally rest your case. It’s not the ghosts in your attic.“This study was in many ways a first step towards understanding the effects of infrasound on humans. So far, we’ve 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,” Scatterty cautioned.“The first priority would be testing a wider range of frequencies and exposure durations. 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,” Schmaltz added.Now that you know, you can give the scary figures in your head some rest, and get a good night’s sleep.
