This Might Explain Why Old Houses Feel Haunted

Those creepy vibes you get in a creaky old house may have more to do with the boiler than with the beyond. A new study suggests low-frequency "infrasound" from aging pipes, boilers, and ventilation systems can quietly raise stress levels and sour your mood—even though undetectable by human ears, per the Guardian and Gizmodo. Researchers in Canada had 36 volunteers listen to either soothing instrumental tracks or horror-movie-style music, sometimes laced with inaudible infrasound (at or below 20 hertz in frequency) via hidden subwoofers.

Participants couldn't tell when the infrasound was on, but when it was, they reported feeling more annoyed, saw the music as sadder, and showed higher levels of cortisol, a stress hormone, according to findings in Frontiers in Behavioral Neuroscience. Study author Rodney Schmaltz says that for believers in ghosts, that vague bodily discomfort can become "proof" of a presence. "They attribute the feeling of irritation to a ghost rather than the old, low rumbling pipes in the basement," the MacEwan University psychologist tells the Guardian. Infrasound also occurs near traffic and industrial machinery, Schmaltz says in a release, suggesting further study on the health effects of prolonged exposure.