Why Won't the Hum Stop? Still No Scientific Explanation For This Mystery Sound

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Not everyone can hear the Hum, but people who do often complain of accompanying nausea, sleeplessness and nosebleeds. Travis Isaacs / Flickr

What exactly is "the Hum"? It's a low, rumbling noise — often described as sounding similar to a diesel engine — plaguing hundreds of people across the globe. And its source is still a mystery.

The Hum is typically heard more clearly indoors, late at night, and affects certain areas of the world more than others. Entire cities and communities have complained of a distracting rumbling noise, confounding scientists as well as medical experts who wonder if it's a problem involving the inner ear.

Indeed, many have considered tinnitus as an explanation to the phenomenon. Tinnitus is the perception of sound within the ear, when there is actually no sound present - it comes from the Latin word tinnitus, meaning "ringing." Tinnitus affects between 38 percent and 60 percent of the population, and ranges across all ages - it's often that ringing you might hear after a loud concert.

But people who've heard the Hum are typically between the ages of 55 and 70, according to a study by acoustical consultant Geoff Leventhall.

Marylin Grech, a 57-year-old who has experienced the Hum recently in a small English village called Woodland, told the Telegraph that "It's not tinnitus, that's a high pitched sound and this is very low. If I put my fingers in my ears it stops, so I know it's not in my head."

As scientists grapple to understand what may be causing the Hum, there have been reports of physical symptoms associated with the noise. Aside from the obvious distraction of hearing a constant noise, people have mentioned headaches, nausea, sleeplessness and nosebleeds that comes along with the Hum - and there has been at least one suicide reported, from a woman who couldn't take it anymore.

Around 800 residents of Bristol, England first reported the Hum in the 1970s. Later, it was heard in Taos, New Mexico; Windsor, Ontario; and Bondi, an area in Australia. About 100 people filed complaints about the Hum between 1999 and 2002 in Kokomo, Indiana.

Dr. Glen MacPherson is a scientist and lecturer at the University of British Columbia who started the World Hum Map and Database as a way to consolidate research and data about the Hum. It includes a database where people who have heard the hum can fill out a survey and map their location.

MacPherson also delves into why it is so difficult for researchers to study this phenomenon, and why not much serious research has been completed to date.

The first reason, he explains, is that are no external metrics available to quantify it. Anybody can claim to hear the Hum and it can often be subjective. The possibility of other low frequency noises, like trains, traffic, and heavy industrial activity, can muddle the analysis as well.

"Further confounding the issue is the reasonable claim that the Hum may not in fact be a sound in the typical sense of the word, but rather a bioacoustical reaction rooted in some combination of electromagnetic, geomagnetic, infrasonic, and other factors," MacPherson wrote.

Until scientists are able to dig more deeply into the causes of the Hum, sufferers are left to drown out the noise with music or other white noise.

"When we examine the history of the Hum and its worldwide distribution, we are left with no convincing explanations for its cause," MacPherson said.

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