The Hum — A Sound That Is Slowly Driving Thousands of People Mad

It usually starts at night.

A low, persistent drone. Not loud enough to be a noise complaint, not quiet enough to ignore. It sits somewhere in the frequency range of an idling diesel engine two streets away, or a refrigerator heard through a wall, or — and this is the description that appears most often — a large vehicle with its engine running that never moves and never stops.

People have searched their neighbourhoods for the source. They have checked their appliances. They have had their ears examined by doctors who found nothing wrong. They have moved house. Some of them have moved to different cities, different countries, different continents — and the sound has followed them.

The phenomenon is called The Hum. It has been documented in the United Kingdom, the United States, Canada, Australia, and across Europe. Researchers have studied it since at least the 1970s. As of this writing, no one has identified its source. No one has explained why only certain people can hear it. No one has explained why it appears to be getting worse.

Bristol, 1970s

The first major documented outbreak of The Hum occurred in Bristol, England, in the late 1970s. Residents began reporting a persistent low-frequency sound that was interfering with their sleep, their concentration, and in some cases their health. Headaches, nausea, anxiety, and in extreme cases nosebleeds were reported in connection with the sound.

The BBC covered it. Scientists were consulted. Investigations were conducted. A report was eventually produced that acknowledged the sound was real — that is to say, real in the sense that something was causing it, not in the sense that it had been identified.

The source was never found.

The Bristol Hum, as it came to be known, affected approximately 2% of the local population. The other 98% heard nothing. Those who could hear it described it with remarkable consistency: a low, rhythmic drone, stronger indoors than outdoors, worse at night than during the day, and — this detail appears across almost every account — seeming to emanate from no particular direction. Not from the east or the west, but from everywhere and nowhere at once.

Taos, New Mexico, 1990s

In the early 1990s, residents of Taos, New Mexico, began reporting the same sound. The Taos Hum, as it became known, attracted significant media attention and eventually a formal investigation commissioned by the US Congress. Researchers from several universities and government agencies spent time in Taos measuring, recording, and analysing.

Their 1997 report is one of the most carefully qualified documents in the history of acoustic research. It confirmed that between 2% and 4% of Taos residents could hear the Hum. It confirmed that standard recording equipment could not capture it — despite multiple attempts, no microphone or measuring device detected a signal corresponding to what the hearers described. It considered and largely ruled out industrial sources, military activity, and geological phenomena.

Its conclusion, stated with scrupulous honesty, was that the source of the Taos Hum could not be identified.

The report also noted something that has since become one of the most discussed aspects of the Hum phenomenon: the complete failure of recording equipment to detect it. If the sound is real — if it is genuinely acoustic — it should be measurable. The fact that it is not suggests either that existing equipment is not sensitive to its specific frequency, or that something else is happening — something that affects human perception without producing a signal in the physical environment.

Neither explanation is comfortable.

Windsor, Ontario

The Windsor Hum is perhaps the most thoroughly investigated specific instance of the phenomenon. Residents of Windsor, Ontario, Canada, began reporting it in 2011. It was louder than most Hum cases — loud enough to rattle windows and disrupt sleep across significant portions of the city. Windsor's proximity to Zug Island, a heavily industrialised island on the American side of the Detroit River, made it a plausible candidate for an industrial source.

Canadian and American authorities investigated. In 2014, a joint investigation by the University of Windsor and a US government body concluded that Zug Island was, in fact, the most likely source — specifically, blast furnace operations producing low-frequency vibrations that carried across the water.

This finding was significant because it was the first time a specific source had been identified for a Hum outbreak. It was also limited: the Zug Island explanation accounted for Windsor specifically, but the Windsor Hum shared the same characteristics as the Bristol Hum, the Taos Hum, and dozens of others — including the inability of standard equipment to reliably record it, and the fact that only some residents could hear it.

If Zug Island explained Windsor, what explained everywhere else?

Who Can Hear It

The selectivity of The Hum is one of its most persistent mysteries. Across every documented case, between 2% and 4% of the local population reports hearing it. The rest hear nothing.

This selectivity has produced two broad explanations. The first is physiological: that certain people have an unusual sensitivity to very low frequency sound — frequencies below 100 Hz — that allows them to detect signals that most people cannot. Research into individual variation in low-frequency hearing has confirmed that such variation exists. Some people genuinely hear lower frequencies better than others.

The second explanation is more troubling: that The Hum is generated not in the environment but in the body itself — specifically, in the inner ear. Spontaneous otoacoustic emissions are sounds generated by the ear itself, without any external stimulus. They are usually high-pitched. But some researchers have proposed a variant — very low frequency spontaneous emissions — that could account for the Hum's characteristics, including its apparent omnidirectionality and its inaudibility to recording equipment.

If The Hum is generated inside the ear, then it is real to those who hear it and undetectable to those who do not, not because only some people have sensitive hearing, but because some people's ears are producing a sound that only they can hear.

This explanation has the advantage of accounting for the recording problem. It has the disadvantage of not explaining why, in multiple cases, people who move to a new location find the Hum there too — or why, in some cases, the Hum is heard by multiple members of the same household but not others.

The Human Cost

It would be easy to dismiss The Hum as a curiosity — an interesting scientific puzzle with no real consequences. The accounts of those who live with it make that dismissal impossible.

Long-term Hum hearers describe sleep disruption severe enough to cause health deterioration. They describe the psychological toll of hearing a sound that others cannot hear and that cannot be recorded — the particular isolation of having a real experience that is structurally impossible to prove. They describe relationships damaged by partners who believe they are imagining it. They describe jobs lost to exhaustion and anxiety.

At least two deaths have been connected, indirectly, to The Hum. A woman in the United Kingdom cited the sound, which she described as unbearable, in a note before her death. A man in the United States similarly referenced it. Neither case established The Hum as a direct cause, but both established that for some people, the experience is not a minor annoyance but a serious and life-altering condition.

The Hum hearers who have joined online communities — where thousands of sufferers share experiences, compare notes, and attempt to triangulate a source — describe the relief of knowing they are not alone as the single most significant factor in their ability to manage the condition. For many of them, simply being believed is the threshold they have spent years trying to cross.

What We Do Not Know

We do not know what The Hum is. We do not know why it affects some people and not others. We do not know whether it is the same phenomenon in every location or a cluster of different phenomena that share characteristics. We do not know whether it is getting more prevalent or whether it is simply being reported more.

We know it has been documented for at least fifty years. We know it has been formally investigated in multiple countries. We know it has resisted every attempt to identify its source.

We know that thousands of people — people who went to doctors and moved houses and gave up sleep and lost relationships — are hearing something.

We just don't know what.

• Sources and Further Reading: The 1997 Taos Hum investigation report is available through the University of New Mexico. The University of Windsor's investigation of the Windsor Hum was published in 2014 and is available through the University of Windsor's research office. For a comprehensive overview of the global Hum phenomenon, Dr. Glen MacPherson — himself a Hum hearer and researcher — maintains a research site at thehum.info. The Bristol Hum cases of the 1970s are documented in BBC archives and UK newspaper records from the period.