The Most Powerful Sound Ever Documented, in 1883

August 27, 1883: when Krakatoa tears through the silence

On August 27, 1883, at around 10:02 a.m., in the middle of the Sunda Strait between Java and Sumatra, a volcano unleashes a cry humanity will never forget. Krakatoa erupts in a series of colossal detonations. The third, the most violent, is generally regarded as the most powerful sound in documented human history.

The sound wave is heard as far as Perth, Australia, more than 3,000 km away, and on Rodrigues Island, near Mauritius, about 4,800 km away. There, people first believe it to be cannon fire from a nearby ship. Imagine this: hearing an explosion happening at the distance of a Paris–Montreal trip.

Around the volcano, it’s not only the sound that kills. The explosion collapses a large part of the edifice and triggers tsunamis on the order of 30 to more than 40 meters high that sweep the coasts of Java and Sumatra. The official toll from the Dutch colonial authorities reports about 36,417 deaths; some studies suggest higher figures, but all agree on the cataclysmic scale of the disaster.

How do you measure a sound from 1883? Barographs and math

In 1883, nobody has a sound level meter on a beach in Java. What rescues modern acousticians are small, unassuming instruments: barographs, continuous atmospheric pressure recorders installed worldwide for weather monitoring. When Krakatoa erupts, air pressure jumps like the pulse of a panicked planet. Barograph needles draw sharp bumps on smoked paper charts.

The Royal Society in London then collects records from more than 50 stations. The traces show a pressure wave that circles the Earth multiple times. Some barographs detect up to seven passages, meaning the wave girdled the globe about three and a half times. It is from these tiny zigzags on paper that, decades later, scientists reconstruct the “volume” of the cry.

In Batavia (today’s Jakarta), about 160 km from the volcano, a gasometer records a pressure jump of more than 8.5 kilopascals, enough to run off the instrument’s scale. By linking this overpressure to acoustic intensity, some modern calculations estimate the sound pressure level reached roughly 172 to 180 dB at that distance.

For a sense of scale: a quiet conversation sits around 60 dB, a jackhammer close to 100 dB, and a jet at takeoff around 120 dB. Above 85 dB, prolonged exposure already begins to damage hearing. At about 194 dB in air, the sound wave turns into a true shock wave. It’s no longer really “sound,” but a brutal pressure discontinuity.

310 dB or 180 dB? A debate that still makes noise

And yet, the numbers are not a consensus. Some recent popular articles cite a level on the order of 300 to 310 dB for the Krakatoa explosion, extrapolating from the eruption’s total energy (equivalent to several hundred megatons of TNT) and the distance at which the sound was heard.

The problem is that 310 dB far exceeds what physics allows for an acoustic wave in the near-surface atmosphere. That pushes well beyond the classic “sound” regime into a quasi-explosive shock domain where simple decibel models no longer make much sense. Many researchers therefore prefer caution and speak of levels on the order of 170 to 180 dB at a few hundred kilometers, emphasizing magnitude more than a precise figure.

In other words, Krakatoa isn’t interesting because one blog claims 310 dB and another 180 dB, but because it sits at the limits of what our atmosphere can transmit in terms of acoustic pressure. It marks a boundary between the world of sound and the world of planetary shock waves.

Ruptured eardrums, but no “villages of the deaf”

Behind these abstract numbers, there are bodies. About sixty kilometers from the volcano, the steamship RMS Norham Castle takes the shock wave head-on. Accounts report that more than half the crew suffer perforated eardrums on the spot. Intense pain, bleeding, partial or total hearing loss for some sailors: the sound of Krakatoa leaves a brutal signature in dozens of human ears.

By contrast, stories of “entire villages made deaf” by the noise alone are closer to myth. Historians who have revisited the sources of the time point out that there is no systematic census of hearing loss linked to the event, and that most victims died in the tsunamis or were buried by volcanic deposits long before anyone took an interest in their hearing.

In other words, we know the death toll fairly well, but we know the number of deaf survivors very poorly. It is reasonable to assume that many people who survived close to the explosion suffered severe auditory trauma, but no reliable overall figure exists, and rigor requires that we not invent one.

When a volcano becomes a global acoustic laboratory

Krakatoa’s pressure wave didn’t just mark human ears. It turned the planet into a vast laboratory. The 1883 barograph records are still used today to study atmospheric wave propagation on very large scales, and they serve as a reference for interpreting modern events such as the 2022 Hunga Tonga eruption, whose waves also traveled around the globe multiple times.

By retracing the history of this “cry of the Earth,” we better understand how sound behaves at extreme scales: how an explosion can turn into a shock wave, how the atmosphere filters or amplifies certain frequencies, how instruments designed for meteorology become, by chance, the first planetary “ears.”

The next time you see a simple pressure curve on a graph, imagine that it could tell, as in 1883, the moment a volcano made the entire Earth howl. And you, what fascinates you most in this story: the physics of sound, or the way we managed, with the means of the time, to listen to and reconstruct this giant cry?