Millions Hear a Constant Hum They Can’t Explain — Now Scientists Know Why

For years, people in different parts of the world have reported hearing the same unsettling thing: a low, persistent hum that others around them cannot detect. It has been described as a distant diesel engine, a transformer, a propeller plane, or a machine running somewhere in the background.

The mystery is often called “the Hum” or “the Taos Hum,” but scientists warn against treating it as one single global sound. Research suggests that, for many hearers, the explanation may be inside the ear and nervous system rather than in the outside world — closer to a rare form of tinnitus than a hidden machine.