Reports of The Hum first started appearing in the 1950's. People who had never heard anything unusual before started hearing a weird, droning hum, sometimes described as sounding like a diesel engine idling nearby. Because so few people heard it, they were dismissed as crackpots or other such things, blaming mass hysteria or hypochondria.
But in the 1970's, The Hum started to spread.
Bristol, England became the first confirmed instance of The Hum. About 800 people reported hearing The Hum, causing nosebleeds, headaches, nausea, sleep disturbance, and at least one suicide. Eventually, The Hum was blamed on local factories working 24 hours a day and the resulting traffic.
Then, in 1991, Taos, New Mexico, got The Hum. Starting that spring, people started complaining about it. Realizing the chance to put SCIENCE! in action, a bunch of people from Los Alamos National Laboratory teamed up with the University of New Mexico, Sandia National Laboratories, and other regional scientists. They detected The Hum and proved it existed. But they couldn't find anything that was causing it.
Want to know what you're missing? Here ya go:
Since then, The Hum has popped up in Largs, Scotland, Windsor, Ontario, Bondi in Sydney, Australia, and Leeds in England. The Hum was detected in Kokomo, Indiana. In 2003, researchers blamed that one on on two industrial sites — one a Daimler Chrysler plant — producing noise at specific frequencies. Noise-abatement measures were instituted, but The Hum remains.
What exactly it is is unknown. The Hum is estimated to only be detectable by about 2% of the population. Tinnitus was initially blamed, but tests on people who heard The Hum found no diagnosis, their hearing was perfectly fine (some may be people who can hear outside the normal human audio range, which is possible and has happened). Besides, researches have confirmed The Hum exists, so it's not human reaction. It's usually stronger at nighttime in rural and suburban areas (it's possible cities have so much ambient noise it cancels The Hum out), and is only heard indoors.
Either way, The Hum appears to be spreading. Sleep tight.