Zug Island, believed to be the source of the hum. (Photo: Tara/CC BY 2.0)

A strange hum that haunted residents in Windsor, Canada, for years before disappearing has returned.

The hum, an inconsistent drone of sometimes loud, sometimes quiet industrial noises, has been heard for the past several months.

“It’s an intrusion, it’s very disturbing, very loud,” Mike Provost, a local resident who tracks the hum, tells The Windsor Star. “Is there a solution? I don’t know. It’s very disturbing.”

Like the hum that residents heard years ago, the latest noise is believed to originate on Zug Island, on the American side, where a steel mill is operated. But no one has ever found out for sure. (A documentary investigating the Windsor Hum is in production, and the hum has also inspired Ph.D. theses and a YouTube channel.)

That first hum also inspired thousands of residents to phone in complaints, though River Rouge, the Michigan city responsible for Zug Island, said then that it was too broke to probe the source.

Later a 2014 federal report linked the hum to the island, but could not find the definitive source after they were denied access to the site of the mill, according to The Windsor Star.

Whatever its source, the latest hum adds another chapter to the history of unexplained noises. Over the years, residents from New Zealand to Bristol, England, have also reported low, possibly mechanical drones, the sources of which are often never discovered. (A conspiratorially-toned Wikipedia entry goes deep on the matter.)

Residents said the Windsor Hum, once considered almost innocuous, was worse than ever.

“It can be almost an exploding industrial sound,” one resident tells The Windsor Star. “You go outside and the sky (over the river) can glow orange and red.”