Infrasound: The Silent Sound That May Make Us Feel Haunted

In many cities, old theaters, abandoned factories, and historic mansions are popular spots for ghost tours. Tour guides point out creaking floors, flickering lights, and strange noises that seem to come from nowhere. Scientists have found that some unsettling feelings in these places may come from a sound we cannot hear. The sound is called infrasound, and it travels in waves below the lowest tone a human ear can detect.

Infrasound is a natural part of the world. Volcanoes, earthquakes, and strong winds produce waves below 20 hertz. Everyday machines also create infrasound. Traffic, trains, air‑conditioning units, and many industrial machines emit low‑frequency vibrations that spread through buildings and the ground. Because the human ear is tuned to frequencies between about 20 and 20,000 hertz, we do not hear these waves. Yet researchers think the body might sense them through the bones in the skull or the fluid in the inner ear, influencing how we feel and react.

The idea that infrasound can affect mood and health is not new. In the 1990s, a study in a cathedral found that people felt uneasy when low‑frequency noise was present. More recent work linked infrasound to headaches, nausea, and anxiety. However, evidence has been mixed, and many scientists want more controlled experiments to confirm the effect.

A new study by researchers led by Dr. Scatterty tried to answer this question. The team recruited 36 college students from a university in the United States. The experiment was double‑blind, meaning that neither the participants nor the people who recorded the results knew which group was listening to infrasound. This design helps to avoid bias.

The experiment took place in two rooms that were set up to sound the same. In each room, a set of speakers played a piece of music. The music was the same in both rooms, so any difference in how the students felt could be attributed to the presence or absence of infrasound. Around the rooms, the researchers installed subwoofers that could produce very low‑frequency sound. In one room, the subwoofers played a silent wave that was below 20 hertz. In the other room, the subwoofers were turned off, so no infrasound was present.

The 36 students were split evenly. Half of them listened to the music with the infrasound wave playing in the background. The other half listened to the same music but without the infrasound. After each listening session, the students filled out a short questionnaire. The questionnaire asked them to rate how the music made them feel, how interesting it was, and whether they thought the music was sad or happy. The students also gave a saliva sample, which the researchers used to measure cortisol, a hormone that rises when the body is stressed.

The researchers measured two main things. First, they looked at the students’ subjective ratings. These ratings told the researchers how the students felt about the music and whether they thought the music was sad or interesting. Second, they measured the cortisol levels in the saliva samples. Cortisol is a hormone that the body releases when it is under stress. By measuring cortisol, the researchers could see if the infrasound had a physical effect on the body, not just on how the students felt.

The results were clear. Students who listened to the music with infrasound reported that the music felt sadder than it did for students who listened without infrasound. They also said the music was less interesting. These differences were true no matter whether the music was calm or more intense. In addition, the students who heard infrasound felt more irritated. The cortisol levels in their saliva were higher after the listening session than in the group that did not hear infrasound. This suggests that infrasound can raise stress hormones in the body.

The study also found that the effect was not limited to a particular type of music. Whether the music was slow and soothing or fast and exciting, the presence of infrasound made it feel sadder and less engaging. This shows that infrasound can change how we experience sound in a broad way.

The researchers think that infrasound may be one reason why people feel uneasy in old buildings. The low‑frequency waves can travel through the walls and floors, creating a subtle vibration that we cannot hear. Even though we cannot hear it, the body may sense it through the bones or the inner ear. This sense could trigger a feeling of discomfort or fear, especially in places that already feel spooky.

The study has some limitations. The sample size was small, with only 36 students. The experiment was done in a controlled environment, not in a real haunted house. The researchers also used only one type of music. Future studies could test more people, use different settings, and try different kinds of sounds. They could also look at how long the effect lasts and whether people can learn to ignore the infrasound.

Despite these limitations, the study adds to a growing body of evidence that infrasound can affect mood and stress. It also shows that even silent vibrations can influence how we feel. For people who enjoy ghost tours, this might explain why some places feel more haunted than others. For scientists, it suggests that low‑frequency sound is an important factor to consider when studying human perception and health.

In the future, researchers may explore ways to reduce infrasound in buildings that are meant to be safe and comfortable. They may also investigate whether people who are more sensitive to infrasound are at higher risk for stress‑related health problems. Understanding how infrasound works could help us design better environments and protect people from unwanted stress.

In short, infrasound is a silent sound that travels below the range of human hearing. It can make music feel sadder, less interesting, and can raise stress hormones. This new study shows that even sounds we cannot hear can shape our emotions and our bodies. The next time you walk through a quiet, old building, remember that there may be a low‑frequency wave humming beneath your feet, quietly influencing how you feel.