Around the turn of the twentieth century, an Italian physics teacher and meteorologist named Tito Alippi undertook a curious piece of citizen science. He mailed survey forms to contacts across Italy asking a very unexpected question: do the people in your part of the country ever hear an unexplained booming noise, like a low rumble or the distant sound of cannon fire? If they do, what do the locals there call it?
Alippi was not the only researcher interested in this phenomenon. In the 1890s scholarly journals like Nature discussed phenomena such as the ‘Barisal Guns’ of Bangladesh, and other such noises from across the world. Many places, it seems, were plagued by sounds like far-off thunder or artillery, but with no apparent cause.
As responses to Alippi’s survey started to come in, it became clear that these unsettling noises haunted much of the Italian peninsula and some Swiss cantons too. Within a short time Alippi had collected not just an impressive number of reports, but also a fascinating inventory of local names for these strange sounds. Around Arezzo people called them baturlìo della marina (naval batteries), while in the Apennines they were variously called bonniti and bombiti. Near Bologna and Modena, people spoke of the ‘Sassuolo Rumble’.
This linguistic diversity wasn’t confined to Italy. Across the world, unexpected booming noises had a variety of names: from the Mistpoeffers heard on the Belgian and Dutch side of the English Channel, to the Gouffre of Haiti and the Uminari of Japan. Noises could occur on inland bodies of water, such as the Lake Guns of Lough Neagh in Northern Ireland and the Seneca Guns of New York State, or along the coast, such as the Cape Barren Guns of Tasmania. Or they could occur many miles inland, like the ‘Desert Sounds’ or ‘Bulldarg’ heard in the Australian outback. Some noises were fairly widespread, while others, such as the Moodus Noises of Connecticut or Pat Hanley’s Guns in south-eastern Australia, were far more localised.
To a scientist, this diversity of names looks both tantalising and hopelessly untidy. If these bizarre noises were to become a respectable object of study, they needed a unified name. Alippi christened them brontidi, ‘thunder-like’. Within a few years, English-speaking meteorologists and seismologists had anglicised this into ‘brontides’.
You may be wondering why you’re only hearing about brontides for the first time just now. The answer is that nobody seems terribly interested in these sounds anymore – largely because nobody seems to hear them anymore, either. A few, like the Moodus Noises, are still reported, and one-off, loud explosive sounds sometimes called ‘skyquakes’ still happen from time to time; in 2011, for instance, the Indian city of Jodhpur was rattled by a sonic shock that was never explained. (Such noises may well be due to meteors, undetected seismic activity, or distant weather noise carried by freakish atmospheric conditions.)
For the most part, however, it seems people today either don’t hear their local brontidi, or don’t comment on them if they do.
Even the Barisal Guns, the most famous of these noises, supposedly fell silent in the 1950s. There are still a handful of folks living in the spa country northwest of Melbourne who have heard Pat Hanley’s Guns. They all agree these sounds, resembling distant underground explosions and said to be a harbinger of poor weather, also stopped sometime around the middle of the last century.
How could noises that were heard often enough to have a plethora of local names have vanished so recently? While there is surely no one single cause for all these global booms and rumbles (one such sound in Florida in recent years turned out to be the mating calls of a local fish!), they mostly seem to be either seismic or meteorological in origin. It seems improbable that the earth and the sky themselves have changed in such a short period. What seems more likely is that these sounds haven’t changed at all. Instead, we have lost our ability to notice them.
Philosophers have tended to treat hearing as an afterthought, a poor cousin of vision. At the heart of the Western philosophical tradition, at least, stands Plato’s famous analogy of the cave, in which shackled prisoners mistake shadows on the wall for the things that cast those shadows. Philosophy’s task is to lead us out of this cavern of illusion and into the light of truth. Notice that there is no easy aural equivalent to this metaphor (let alone for our other senses); even echoes are not shadows. A few philosophers since have paid attention to the distinctive problems posed by sound: for instance, where are sounds? Is a sound located at its point of origin, or at the hearer, or between the two, or somehow nowhere? Yet for the most part, philosophers have remained in thrall to visual metaphors and paid hearing much less mind.
Perhaps that cultural bias is why we’ve been so slow to notice the crowded sonic world we’ve built for ourselves. Industrialisation has made the world drastically noisier than it once was. As the biologist David George Haskell has recently argued in his book Sounds Wild and Broken, the din of human life is making life on earth a lot harder for the species we share it with.
Even the oceans have become an unbearably noisy place for many animals due to human activity. Sound propagates radically differently through water than air, a fact that governments exploit by using underwater microphones to detect military activity hundreds or even thousands of miles away. Animals like whales have evolved to exploit this too, communicating by song over vast distances, and changing course in response to sounds like the grinding of distant icebergs.
So when humans fill up the oceans with noise from shipping, sonar, and resource exploration, whales are both stressed by the volume and unable to hear sonic cues they need in order to navigate successfully. The results include delayed migrations, unnatural behavioural changes, and strandings.
We might be forgiven for being unaware of what happens far out at sea. But on land, too, humans have failed to notice how loud we have made our world.
If you’ve ever had the experience of noticing that the air conditioning has just shut down, you will know that sounds are sometimes only salient to us when they stop. Under normal conditions, cities project vast amounts of sound in all directions. For city dwellers, this simply becomes the background buzz of their days and nights. Yet during the COVID epidemic lockdowns, seismologists noticed that the sudden absence of city noise – traffic, machinery, and so on – meant the earth was temporarily quieter, making it easier for sensors to pick up certain faint sounds that would normally be overwhelmed.
Animal behaviour changed during what scientists christened the ‘anthropopause’ or ‘COVID-19 quietus’ too. As just one example, some Californian sparrows changed their vocalisations to take advantage of the sudden quiet. Without human sounds to compete with, they could begin communicating across greater distances. High noise levels are not only stressful for animals, they bury information that allows for deeper understanding of what is going on too. When the air is no longer overloaded with noise, animals can attune themselves to what the environment around them is telling them. And what is true of sparrows is perhaps true of us too.
Did brontidi really stop sounding? Or have we simply filled our world with so much clamour that these earth noises can’t get our attention – just one more ill-defined thud in a soundscape overcrowded with loud shocks? Could it be we are no longer aware of calls from the deep that once filled us with awe and fear, now drowned out in a cacophony of our own making? And if we can no longer hear these booms, just what else might be getting lost in the racket?
