The Hum is the name given to a persistent low-frequency drone or rumble that a small minority of people report hearing, often indoors and at night, while others in the same place hear nothing. Reports gathered in Bristol, England, in the 1970s, when newspapers received letters about a noise that never stopped. In 1993 residents of Taos, New Mexico, described a similar sound, and scientists from several US laboratories and the University of New Mexico measured the area without finding a cause.
Some cases have plausible local explanations. In Windsor, Ontario, a government-funded study launched in 2013 detected an airborne tone of about 35 Hz and pointed, without confirmation, to a blast furnace on Zug Island on the US side of the border; reports seem to have stopped after the plant closed in 2020. Elsewhere, studies of hearers have favoured a low-frequency form of tinnitus, and researchers now assume several different causes. As a single phenomenon the Hum remains unexplained, a reminder that the boundary between environmental drone and the ear’s own noise is not always easy to draw.