'The Hum': the real-life noise behind The Listeners

A "surreal" new BBC drama about a strange phenomenon known as 'the Hum' is "not as far-fetched as you think", said Radio Times.

"The Listeners", adapted from Jordan Tannahill's novel of the same name, follows a group of people who are plagued by a mysterious, persistent, rumbling sound. And it's estimated that "4% of the global population are affected by the Hum", wrote Tannahill for The Guardian.

The TV drama is "freaky, brilliant TV", said the i news site. It "keeps you finely unbalanced throughout", said Lucy Mangan in The Guardian, as "our capacity for collective delusion and denial" are "dissected and laid out for horrified inspection".

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Real and severe disturbance

The "earliest reliable reports" of the Hum emerged in the UK in the mid-1970s, wrote Tannahill, "most notably from Bristol", where letters began appearing in a local paper about a "low rumble" heard by dozens of city residents.

Then a series of Sunday Mirror articles about the Hum prompted a "flood of mail" from readers across Britain who had been suffering from "the same maddening sound", said How Stuff Works. Scientists at Southampton's Institute of Sound and Vibration Research noted the news reports and, in 1977, published a study in Applied Acoustics about a "particular environmental noise phenomenon which appears to be a cause of real and severe disturbance to certain people".

The Hum makes sufferers anxious and depressed, said How Stuff Works, and "in one tragic case" has been "linked to suicide". The sound has been compared to the rumble of a lorry idling and becomes "worse at night, making it hard to sleep". It can also "cause crippling headaches, nausea, nosebleeds and diarrhoea".

But what causes this phenomenon? Early theories about the Bristol Hum suggested it "came from large industrial fans used at a nearby warehouse", wrote Tannahill. Then marine scientists argued that an outbreak in Hythe might have been caused "by the mating call of male midshipman fish", which "emit ever-louder drones, sometimes for hours".

At "an Institute of Biology conference in 1973", it was even posited that "the jet stream, shearing against slower-moving air" might be causing a very low-frequency sound "that could then be amplified by electricity pylons".

Extreme fringe theories

In the decades since, more theories have been put forward. In 2015, a team of French scientists suggested that the Hum was caused by "ocean waves extending down to the ocean floor and shaking the Earth", while others concluded that "vibrations caused by volcanic eruptions and earthquakes" might be the culprit.

"Yet another theory", said Tannahill, centres on the "nearly eight million lightning strikes" that hit the earth every day, "building up an electromagnetic charge" that causes the air "between the surface of the earth and the ionosphere to resonate – much like the inside of a bottle when one blows across its top".

"As with any mystery", wrote Ellie Harrison for The Independent, the hum has been used "as a jumping-off point for wild conspiracy theories". These include everything from 5G masts to "extreme fringe theories around military and government sonic weaponry and mind control", Tannahill told the outlet.