The Mysterious 'Hum' Heard Around the World for 50 Years May Finally Have an Explanation

For half a century, people around the world have reported a maddening, low-frequency drone with no obvious source—a phenomenon known simply as "the Hum." Now researchers say they may have finally cracked one of acoustics' most persistent mysteries, and the answer points inward: the sound may be generated inside the listener's own auditory system.

An estimated 2 to 4 percent of people worldwide say they can hear the Hum, a steady, engine-like rumble that many describe as unmistakably external and often unbearable. Reports began surfacing in earnest in the United States in the 1990s, first in Taos, New Mexico, and Kokomo, Indiana, before spreading to Canada, Australia, New Zealand, South Africa and cities across Europe. Despite decades of investigations, engineers have rarely been able to locate any physical source.

In the new study, published in the journal PLOS One by researchers at the Norwegian University of Science and Technology, scientists tested two leading hypotheses. They checked whether people who hear the Hum have exceptionally sensitive low-frequency hearing, and whether their ears produce faint measurable sounds of their own. Neither explanation fit the majority of participants.

Instead, the researchers concluded that many cases likely involve a form of low-frequency tinnitus—a phantom perception of sound created by the brain and auditory system rather than by anything in the surrounding environment. Ordinary tinnitus typically manifests as a high-pitched ringing, but the team's findings suggest a low-frequency variant could account for the deep, throbbing quality that Hum sufferers consistently describe.

If confirmed, the explanation would reframe a phenomenon long dismissed as either mass delusion or the byproduct of distant industrial machinery. It would also offer some validation to the many people who have insisted for years that the sound is real, even when no instrument could detect it. The researchers caution that the Hum may not have a single cause—some cases could still stem from genuine environmental noise—but for the millions plagued by an inescapable drone with no off switch, the study offers the first solid scientific footing in decades.

The Hum has spawned an entire subculture of sufferers who compare notes online, keep detailed logs of when the sound is worst and, in some documented cases, have relocated in a desperate bid to escape it. Physicians have often been at a loss, because standard hearing tests come back normal and no external source can be found. If the low-frequency tinnitus explanation holds up, it could open the door to treatments already used for conventional tinnitus, such as sound therapy and cognitive behavioral techniques, that help the brain learn to tune the phantom noise out. The authors say larger studies across more countries will be needed to confirm the mechanism, but they hope their work will at last move the Hum from the fringes of anecdote into the realm of testable science.