BBC One drama The Listeners stars Rebecca Hall as a teacher pushed to the brink of mental collapse after she starts hearing a low hum that no one around her seems to pick up.
It may be adapted from a fictional novel by author Jordan Tannahill, but surprisingly is based on reality: a handful of people around the world have claimed they could hear ‘the Hum’, a mysterious and constant low hum.
Apparently the Hum most often happens at night, and those that can hear it report that it is louder indoors than when they go outside. It’s most frequently reported in urban areas. Descriptions vary, but the Hum is often likened to a rumbling or droning sound, like an idling truck engine.
There are a range of theories as to the origins of this mysterious sound: from machinery to tinnitus, power lines to phone masts... and even amorous fish.
Yes, really. In 2013, residents of Hythe near Southampton complained of a loud humming noise that was keeping them awake. Scientists suggested it could be male Midshipman fish, a nocturnal creature that makes a low frequency droning sound to warn off other males. Midshipman had previously been found to the culprit when houseboat residents in Sausalito Harbor, California, reported strange noises coming through their hulls.
There is currently no scientific consensus on what causes the Hum – or even if there is a singular cause versus different localised noises.
It has baffled scientists and been covered extensively in the media – including this 2021 article written by Tannahill, who also adapted the series for the screen. In a nice little Easter egg, Hall’s character Claire is even seen scrolling the story on The Guardian.
So where does fiction end and fact begin with The Listeners?
People who can hear the Hum don’t call themselves Listeners, as they do in the TV show, but some do self-identify as “hummers” or “hearers”.
Those that can hear the Hum have reported nosebleeds, headaches and sleeplessness as physical symptoms of hearing the hum (all covered in The Listeners), as well as diarrhoea (not in the BBC One show, thankfully).
While there isn’t a real cult that’s built around the phenomenon (that we know of, at least), there are several conspiracy theories about the Hum. Conspiracists believe it is caused by the military testing sonic weapons, mind-control devices or, of course, aliens.
Others blame ELF (extremely low frequency) radio waves, which can penetrate seawater to submarines at operating depths. However, only a few countries have the technology and they require very large and obvious masts.
The theory about lightning that Omar and Jo talk about in the second episode of The Listeners has been floated. The idea is that some of the eight million bolts of lightning that strike the Earth every day could cause vibrations, which might by audible. Other natural phenomena such as the jet stream or waves crashing on the ocean floor have also been posited.
Skeptics believe that it’s just people unwilling to accept they have tinnitus, or some kind of mass delusion.
It’s perhaps somewhat off-putting to serious scientists, although several have tried to find tangible causes for the noise, or an explanation for the reports from people who hear it. Geoscientist David Deming wrote a paper in 2004 titled ‘The Hum: An Anomalous Sound Heard Around the World’, while acoustic scientist Chris Barnes has been researching the topic for years.
The most prominent Hum scientist is Dr Glen MacPherson, a Hum hearer who set up the World Hum Map and Database Project to record instances of the hum. Dr MacPherson estimates that between two and four per cent of the population can hear the hum.
He divides Hum hearers into two types – those experiencing an as-yet-unexplained “type of otoacoustic phenomenon generated internally in the brain and auditory organs”, and those with “exceptionally sensitive hearing” who are picking up on environmental noises that most people can’t hear.
“This is not a place for pseudoscience or conspiracy theories. There are no discussions here regarding so-called ‘Targeted Individuals’ or microwave weapons,” he says of his project. “There are many other websites and forums for those interested in such things.”
The Hum only started to be heard around the Seventies, leading scientists to believe it could be related to technological developments. It was first reported by residents in Bristol, England, and was thought to be rattling factory vents. But Bristolians began reporting a Hum again in 2016 – long after the factories closed.
It was reported in Taos, New Mexico in the Nineties, then in Auckland, New Zealand in 2006. No one source was ever found.
Some Hums do have a real-life culprit, though. There was a Windsor Hum in Ontario in 2011, although that was pin-pointed to a steel mill on Zug Island. When the blast furnaces were decommissioned in 2022, the Hum went silent.
The Listeners is not the first time that the Hum has appeared in popular culture, either. In Drive, a 1998 episode of The X-Files, Agent Scully (played by Gillian Anderson) speculates that ELF radio waves “may be behind the so-called Taos Hum”. Criminal Minds ran a storyline in 2018 where the Hum causes people to go on a violent rampage.
For Tannahill, it was the mystery and multitude of explanations that provided such fertile grounds for fiction. “There are some people who believe it is a geoscientific phenomenon, which intrigues me. There's the idea that there’re aspects of the world of nature that we don't yet understand. There’re also theories that suggest that we could be living in conflict with nature,” he told the BBC.
“But going deeper than that, what intrigues me about the story is, do we have a shared reality in society?”
The Listeners is available now on BBC iPlayer
