It is a scenario that sounds plucked from science fiction.

A mysterious sound invades the shores of a large post-industrial city. It's known as The Hum. Picture frames rattle on the walls; residents report nausea and lost sleep.

Eventually, an official report traces the source of the sound to an island wrapped in fences and home to a belching steel plant; visitors are not welcome. Amidst the secrecy, odd theories flourish, involving UFOs and a billionaire's secret tunnel.

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Over the years, the sound comes and goes, but never stays gone for long. Half a decade after The Hum first sounded, it grows louder than ever.

For many residents of Windsor, Ont., this is not, or not merely, a sci-fi plot. They call it a civic nuisance that has pushed them to their wits' end and highlighted anxieties over sovereignty and the fate of industry in a hard-hit border community.

After years of stasis, they hope the Liberal government will save their ear drums and their peace of mind.

The Windsor Hum, as it's known, has been compared to an idling diesel truck, a "constant earthquake," an orchestra tuning up, and a car's subwoofer playing Barry White.

Gary Grosse, the Hum's foremost expert and leading spokesman for its "victims," said the sound comprises two main parts: a rumble and a pulse, both at an extremely low frequency.

Women are said to perceive it more readily than men, but thousands of both gender claim to be tormented by the noise. Mr. Grosse's Facebook group dedicated to the Hum has nearly 1,400 members. A public teleconference on the issue in February, 2012, drew some 20,000 people, says Al Maghnieh, a former Windsor city councillor.

And the Hum has gotten worse since then. "This is probably the loudest it's been in the last six years," Mr. Grosse said.

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The most frequent Hum-related complaint is interrupted sleep – the sound seems to be most prominent in the quiet of night. Mr. Grosse resorted to sleeping pills for two years.

Others describe physical symptoms they believe are caused by the noise. Mike Provost, a retired insurance salesman active around the issue, pops Tums to cope with his Hum-engendered nausea.

The sound might be less irritating if it were more predictable. Instead, it occurs at odd times and for seemingly random intervals, sometimes for hours, sometimes a full day and then sometimes not for weeks.

That erratic schedule has helped turn the Hum into an "obsession," Mr. Grosse said. "You go home and you're listening for it: 'Ah, there it is!' "

Unanswered questions only add to its fascination. Although a federal government study placed the Hum's likely source on the grim industrial enclave of Zug Island, on the U.S. side of the Detroit River across from Windsor, much remains unknown.

Why, for example, did the noise apparently start up in 2011, more than a century after heavy industry came to the island; why do residents on the U.S. side seem less bothered; and why does it come and go, even as the steel plant churns away?

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"We don't have any information about what's happening over there – so there is a kind of mystique or mystery," Mr. Grosse said.

Conspiracy theories have sprouted in these shadows of doubt. One bit of wild speculation holds that Manuel "Matty" Moroun, a secretive Detroit billionaire whose family owns the Ambassador Bridge, is digging a tunnel in the area to outflank a new planned bridge over the river. Others mutter about alien aircraft or nuclear testing.

These notions tend to embarrass more serious Hum hunters. "I get a little bit irked sometimes when people call it a mysterious noise," Mr. Maghnieh said. "We've had two reports and some very smart people pointing to a very industrialized area."

The federal government has taken two cracks at solving the riddle. In June, 2011, after months of inquiries, Natural Resources Canada conducted a study of the sound that failed to pinpoint its exact source, but discovered that it measured about 35 Hertz (a deep bass tone) and that it probably came from Zug Island.

The enigmatic isle is part of the tiny suburban municipality of River Rouge, Mich. and home to two industrial behemoths: the U.S. Steel plant, and a coke battery owned by DTE Energy, the local utility company.

A more extensive study in 2013 – commissioned by the Department of Foreign Affairs and International Trade and using special equipment to detect extremely low frequencies – suggested a blast furnace was a likely cause of the Hum.

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But with responsibility still uncertain, efforts to curb the sound have been halting. In 2012, foreign affairs minister John Baird sent his parliamentary secretary, Bob Dechert, to Detroit on a fact-finding mission.

The results were disappointing, said Brian Masse, the New Democrat MP for Windsor West. Mr. Masse has been badgering governments about the Hum for years. He says Canada's diplomatic priorities always seem to lie elsewhere.

A Jan. 6 letter he sent to Foreign Affairs Minister Stéphane Dion received a tepid response, Mr. Masse said.

The U.S. side has its own reasons for avoiding a resolution. Closing or modifying its Zug Island plant could cost U.S. Steel a steep price and the company refuses to address the subject in public.

"We do not comment on this issue," corporate spokesperson Sarah Cassella said on Friday.

River Rouge is reluctant to interfere with the operations of a top municipal taxpayer like U.S. Steel, Mr. Masse said. (City staff did not respond to a request for comment.)

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Many in Windsor sympathize with their U.S. neighbours – both sides of the border have been stung by industrial decline.

"We don't want anyone to lose their job," Mr. Provost said. "We don't want U.S. Steel to shut the furnaces down. We just want them to meet with some engineers about how to muffle it."

In the meantime, he will continue popping antacid tablets and tossing in his sleep, haunted by the Hum.

"Once you hear it, you're done," he said.