The Mysterious, Torturous Hum Plaguing People Around the World

For nearly 40 years, a strange humming sound has been creating a lot of buzz -- literally -- in various communities around the world. Bothersome and often intolerable, the sound has baffled locals and scientists this whole time who are still unsure whether "the Hum" is truly a scientific phenomenon or just mass delusion.

According to a report from the New Republic, people who have experienced the Hum are quite consistent in describing it. The sound is heard as "a low, distant rumbling, like an idling diesel engine." More often than not, the Hum can be heard during nighttime and indoors. It's also more commonly picked up in quiet rural areas; very rare do people make the droning sound out in the urban setting, probably because of the background city noise.

The Hum is more than a simple annoyance, too. Reports say people often suffer from a variety of ailments from it including headaches, nosebleeds and nausea.

Since it only affects a small number of people -- two percent of Hum-affected areas, by several accounts -- it's unknown when the first-ever experience of the Hum occurred. The story began gaining media traction in the 1970s in Bristol, England, when news of the phenomenon prompted hundreds of locals to send in letters of their own experiences with the baffling sound.

"It's a kind of torture, sometimes you just want to scream," retired head teacher Katie Jacques from Leeds, England told BBC News in 2009, adding that she can't sleep at night when the noise is at its worst. "It has a rhythm to it -- it goes up and down. It sounds almost like a diesel car idling in the distance and you want to go and ask somebody to switch the engine off -- and you can't."

The Hum can get so agitating that at least one suicide in the U.K. has been traced to the maddening sound. The same thing happened in seemingly random places all around the world: Taos, New Mexico; Kokomo, Indiana; Largs, Scotland; and Bondi, Australia, among them.

Even after decades of the Hum permeating communities around the globe, scientists are unable to ascertain its source. Researchers have offered several theories, but none have been definitively proven as of yet.

A report from Live Science revealed that a study on the Kokomo Hum have pointed to industrial equipment as the root of the sound. Other potential industrial sources include high-pressure gas lines, electrical power lines and wireless communication systems. There has only been a few cases that the Hum has been connected to mechanical and electrical sources, though.

Medical experts have suggested tinnitus, a condition when the patient perceives sound where there is none, but tests on the subjects have shown that most of the Hum-afflicted people have regular hearing.

In 2015, researchers offer an alternative explanation: microseismic activity generated from long ocean waves can make the Earth vibrate and produce the rumbling sound, according to a report from The Independent. More sensitive people can detect the sounds.