RACHEL MARTIN, HOST:
For a decade, Canadians living near the U.S. border swore they could hear a strange reverberation. It became known as the Windsor Hum, named for the Ontario city near the border with Michigan.
COLIN NOVAK: The low-frequency component tended to shake people's houses, the windows, et cetera.
NOEL KING, HOST:
That's Colin Novak. He's a scientist from the University of Windsor who studies the hum as part of a Canadian federal government investigation.
NOVAK: You had a lot of conspiracy theorists as well, saying that it was military experiments to, you know, something from outer space.
KING: It was probably not. Novak says the mystery may be solved.
NOVAK: Ninety-nine percent, I would say, I consider it solved.
MARTIN: The breakthrough came a few months ago when the hum just stopped. At the same time, an American steel factory stopped its operations on nearby Zug Island.
NOVAK: U.S. Steel was going to shut down some of their operations this year on Zug Island. And part of that would include the blast furnace.
MARTIN: Once those blast furnaces went quiet in April, so did the hum.
NOVAK: There had been no complaints, as far as I'm aware of, since they shut down their operations.
MARTIN: Novak doesn't expect the hum to come back, but there's a downside. He thinks U.S. Steel is permanently moving its operations out of the area to cut costs, so some jobs likely aren't coming back either.
(SOUNDBITE OF HUM'S "STARS") Transcript provided by NPR, Copyright NPR.