What do we know about “hum”, this mysterious noise that some people hear in several cities around the world?

“I didn’t hear it until I started listening to it, and now it’s impossible not to hear it,” Bernie, a resident of Omagh, Northern Ireland, told the Ulster Herald. She talks about a noise nicknamed “hum” (buzzing, whirring). Since the end of October 2023, many residents of the town have complained about this. So much so that Fermanagh and Omagh District Council has promised to investigate. But “given the vague nature of this noise and its extent, locating and identifying its exact source may take time,” he warns.

The people of Omagh are far from being the…

“I didn’t hear it until I started listening to it, and now it’s impossible not to hear it,” Bernie, a resident of Omagh, Northern Ireland, told the Ulster Herald. She talks about a noise nicknamed “hum” (buzzing, whirring). Since the end of October 2023, many residents of the town have complained about this. So much so that Fermanagh and Omagh District Council has promised to investigate. But “given the vague nature of this noise and its extent, locating and identifying its exact source may take time,” he warns.

Omagh residents are far from the only ones to hear that famous “hum”, described as a dull noise, a hum similar to the engine of an idling truck or a low-flying plane. United States, England, Europe, Australia: this mysterious sound is heard in various places around the world. The first testimonies date back to the 1970s and 80s and they have multiplied in recent decades.

Neither tinnitus nor a collective hallucination

Each time, the scenario is the same: part of the population complains of hearing a persistent noise that appears suddenly. It vibrates in the ears of people who are sensitive to it, mainly at night, whether they are indoors or outdoors. Using earplugs or noise-cancelling headphones doesn’t change anything. And very often, it is impossible to know where this noise is coming from.

Studies were notably carried out in Taos (New Mexico) and Kokomo (Indiana), in order to identify and locate this mysterious noise. First certainty, the “um” has nothing to do with tinnitus. The latter are internal noises (felt in the ears or head) which are not emitted by an external source. What’s more, people who suffer from them hear them all the time, wherever they are. However, the “hum” generally seems linked to a geographical area (a city, a state). “Most people who hear it no longer hear it when they leave the area,” according to James P. Cowan, a noise control engineer who led the Kokomo study. Knowing that the area can be very large, as proven by the example of the “hum” of Windsor (Canada), where the hum is not only limited to the city but would be heard as far as Cleveland, more than 144 kilometers away.

And even if the fraction of the population capable of hearing it is quite small (between 2% and 10%), “these people are not crazy,” says James P. Cowan. “What they hear is real.” At best, the “um” is extremely painful for them. But in a number of cases, it can even be accompanied by headaches, nausea, diarrhea, fatigue and memory loss. It remains to be seen where it comes from. And that is the problem.

Difficult to locate

In Taos, the battery of measurements carried out revealed a high electromagnetic field, caused by local power lines, as well as malfunctions of electrical appliances in and around the homes of the “hum” “victims”, but no acoustic signal was not detected. Conclusion: the “Taos Hum” could not be located.

In Kokomo, in addition to a high magnetic field, scientists detected low-frequency sounds coming from two industrial facilities. Once the intensity of these was reduced, some of the residents who complained of hearing the “hum” no longer felt it. But most of those affected continued to be affected. Conclusion: the “Kokomo Hum” has not been clearly identified either.

In Bristol (UK), British media attributed the ‘hum’ to waves emitted by wave action on the seabed. However, “this has nothing to do with it,” sighs Fabrice Ardhuin, one of the authors of the study on the subject, published in 2015. “What we call the hum of the Earth are vibrations which correspond to the movement of the earth’s crust, which rises and falls at frequencies measured in milli-hertz,” he explains. “We are far from something that vibrates several times per second. So when we talk about the noise of the Earth, it is not in the audible sense of the term. »

As for Windsor, where the “hum” had been rampant since 2011, experts suspected that the culprits could be the blast furnaces of the American steel producer US Steel located on Zug Island, on the American side of the Detroit River. They ended up having confirmation when they stopped, in April 2020, in the middle of the Covid pandemic. The “um” fell silent with them.

So many examples which show that if the experts have serious clues concerning the “hum”, they do not really have certainties, except that its origin is certainly human and that its sources are multiple.

Why can’t everyone hear it?

For the moment, the most commonly accepted explanation is that of the geophysicist David Deming, author of a global study on the subject in 2004. According to him, “hum is more than a simple noise since it can also manifest itself in the form of vibrations felt throughout the body. The most likely explanation is that some people have the ability to interpret radio transmissions at certain wavelengths (especially low frequencies) as sound. »

This is why not everyone is sensitive to “um”. According to David Deming, only 2% to 10% of people are able to hear it, or rather feel it, since it is not a sound strictly speaking. And the fact that they are radio waves would also explain why “hum” can appear in various places on the planet and why the phenomenon is recent.

And to the extent that the “hum” is only “audible” to a fraction of the population, it should not be confused with other “noises” that can occur occasionally. Like the mysterious “beep” heard by the Inuit in the Arctic at the end of 2016 and for which the Canadian army has not found an explanation. Or the grunt emitted by male toadfish during the breeding season.