Glen MacPherson has become one of the leading researchers of a global phenomenon known as the world hum.

Best described as a deep rumbling sound similar to that coming from a large truck idling in the distance, the hum has been reported thousands of times on every continent.

Just the noise alone can drive people batty. Others report physical discomfort because the low drone vibrates through their bodies, causing headaches, earaches and stiffness in their joints.

Some communities, like Kokomo, Ind. and Taos, N.M., have garnered plenty of hum attention because the problem is so prominent. There's also the well-known Windsor Hum in southwestern Ontario, but many amateur researchers there say the source of their hum is not the same as what causes the hum in other regions.

B.C. researcher Glen MacPherson has plotted the locations of more than 9,000 hum reports around the world. (Glen MacPherson)

From his home on B.C.'s picturesque Sunshine Coast, MacPherson has been tracking the world hum. When he first heard it while living in Sechelt, B.C., he thought there was a flock of seaplanes flying over his home.

The high school math teacher started unplugging appliances, one by one, trying to identify the source.

"I found that the greater the number of appliances I turned off, the louder the hum got," he said.

His mysterious noise amplified even more when he cut the power to the entire house. So he jumped in his car and took a drive.

"I discovered that I could hear it pretty much everywhere I went on the Sunshine Coast, as long as it was later at night or the ambient noise was fairly low," he said.

MacPherson now lives in Gibsons, B.C., and has since discovered that people around the world have heard the mysterious noise that he dedicates so much time to researching.

Meanwhile, in Windsor

Other people are doing their own research on hum phenomena. Mike Provost of Windsor first heard the hum four years ago.

"Once you hear it, you always hear it. If you never hear it, you're lucky because it's very, very disturbing," he said. "It rattles everything, including your body, your stomach, everything — headaches, stress, shoulders, neck, ears. Your ears pop, your ears always seem like they're plugged."

Mike Provost has been capturing the Windsor Hum for more than four years with recording devices. He blames the U.S. Steel plant on Zug Island. (Derek Spalding/CBC)

In his mind, the Windsor hum is not the world-wide phenomenon MacPherson is tracking. He cites a 2014 study from the University of Windsor that determined the noise comes from Zug Island, which is home to a heavy manufacturing operation of U.S. Steel.

Provost welcomes other theories from people like MacPherson and accepts there is an outside chance the source is not Zug Island.

"Absolutely. Do we believe that? No," he said. "We know it's coming from Zug Island."

People only need to experience the Windsor hum to understand how it differs from the hum in other regions, Provost told CBC News.

"Our noise is very different than all the other hums they talk about."

To further pinpoint the sound, Provost set up three tiny recorders — smaller than the average cellphone — in three corners of his backyard collecting audio 24 hours a day.

Mike Provost of Windsor has been recording the hum for years in his backyard 5:56

Provost hopes the positioning of the devices will help him triangulate more accurately where the sound is coming from specifically. Hours of digital recordings are collected and stored on his computer.

MacPherson, however, has his own theory about the source of Windsor's hum.

"I'm not convinced that Zug Island is the sole source of that disturbance," he said. "For all we know, all those reports from Windsor and Lasalle and that area are being confounded by people who can hear the world hum."

Mapping the hum

To understand the scope of the phenomenon, MacPherson plotted the locations — along with a thorough description — of more than 9,000 hum reports around the globe. He meticulously pores over each report to ensure it fits the pattern.

His detailed and exhaustive World Hum Map and Database Project has become one of the initial online stops for people first learning about the mysterious noise.

People have put forward many theories about the world hum, blaming everything from cellphones to the introduction of electric power grids. But MacPherson has ruled out many of those by pairing his own research with that of the few others who have studied the noise.

The standard narrative for the world hum, MacPherson explained, is that it rose to prominence in England during the late 1960s. Assuming the timeline is correct, that immediately rules out several theories. Cellphones have not been around that long, and the power grid has been around a lot longer, which means reports would have occurred sooner.

There is emerging evidence that similar noise reports may date back to the 1800s in London.

"I'm by no means ready to make that conclusion, but that's something that's being actively investigated," MacPherson said.

Testing radio waves

MacPherson is currently testing one hypothesis put forward by American geophysicist David Deming, who suggests the hum could be attributed to very low frequency radio emissions used in military planes to communicate with submarines.

MacPherson designed a VLF blocking box, which was envisioned in Deming's hum research paper published in 2004. MacPherson built a box that is big enough to climb inside. If the hum is rooted in very low frequency radio frequency waves, that box should block the noise. His results so far have been inconclusive, but is looking for a better location to test the device.

"It is the source of some humour for some people," he said, laughing. "It looks like a metal coffin."

MacPherson also plans to test a few other theories, including general ambient noise created by modern technology.