CANTON, Mich. (WWJ) -- If you live in Canton Township, you may have heard a low-pitched, constant hum over the last few days.

Many people have been asking "what is that noise."

The answer? No one really knows.

Canton Police Lt. Jim Harrison says his department has received several calls about the noise.

“I spoke to one homeowner who had been hearing it for some time now, but last night is when we got multiple calls about it," Harrison told WWJ. "I’ve heard recordings of it, and I’m not sure what it is.”

Numerous residents have been filling social media accounts with their tales about a strange, annoying noise in recent weeks that was particularly loud Monday night.

"It's disturbing. We've had the pictures fall off the wall." Neighbors in Canton reporting "strange and intense" vibrations "only at night..." City and Canton police now investigating... MORE: @FOX2News 5PM pic.twitter.com/dlcoVLbV7I — Erika Erickson (@FOX2Erika) March 19, 2019

Residents reporting or inquiring about tremors/vibration/noise in the southeast area of Canton (Lotz & Palmer), please call Canton's Public Safety dispatch center at 394-5400. PSD call takers will verify the resident... https://t.co/v71xEEDK3I — Canton MSD (@CantonMSD) March 19, 2019

Since 2016, Windsor residents have been complaining about a mysterious humming noise. They've even started a Facebook group called the Windsor/Essex County Hum.

Internet research shows similar phenomena have been reported all across the globe. The Guardian newspaper in London ran a story over the weekend about the mysterious "Global Hum."

The story says some people have reported hearing the noise all the way back to the 1970s. Some say it is louder indoors than it is outdoors, but it follows them wherever they go. Many people aliken the noise to a running diesel engine or other machinery in the distance, but have been unable to track it down. Some say they can feel a vibration with it.

Some people thought it was tinnitus -- ringing in the ears -- but others have ruled it out, as that is a much higher frequency.

A website called "The World Hum Map and Database Project" tracks reports of the noise, with thousands across the United Kingdom and all of Europe saying they've been bothered by it.

A similar phenomenon has been well-documented in the U.S. -- "The Taos Hum" -- which has been heard in Taos, New Mexico, for decades. No one has ever gotten to the bottom of it.

Have you ever heard "the hum" over the years?