The loudest sound ever heard on Earth

Lithograph of the 1883 volcanic eruption on Krakatoa.Parker & Coward, Britain (1888) via Wikimedia Commons

The science magazine Nautilus ran an irresistible article last week on “the most distant sound that has ever been recorded in human history.” Writer Aatish Bhatia, a physics PhD turned journalist, explains that a volcanic eruption on the Indonesian island of Krakatoa in 1883 released a noise that circled the planet four times and was audible thousands of miles away.

It’s an amazing kind of superlative, and virtually every detail associated with the eruption is jaw-dropping. One contemporaneous account from Rodrigues, an island in the Indian Ocean, described the sound as “coming from the eastward, like a distant roar of heavy guns”—and Rodrigues is 3,000 miles from Krakatoa. For comparison’s sake, Bhatia writes, “[this] is like being in Boston and clearly hearing a noise coming from Dublin, Ireland.”

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Once you’re introduced to the category of “the loudest sound ever,” it’s impossible not to start wondering what else might qualify. Many people of varying credibility have made their own lists, and Krakatoa does indeed top many of them, though a few nominate a different cataclysmic natural occurrence for producing the loudest sound ever: the “Tunguska event,” which occurred when a comet exploded over Siberia in 1908. In normal life, the loudest sounds tend to emanate from the sources you’d expect, like shotguns, jet engines, drag racers, and bombs. One surprise entrant is the friendly sperm whale, whose clicks, according to one biologist quoted in a 2003 National Geographic article, are equivalent to “a rifle shot three feet from your ear.”

An important fact about the “loudest sound” category is that the composition of the Earth’s atmosphere and the physics of sound production mean that no sound on Earth can ever be louder than 194 decibels — beyond that, the event creates a shock wave that actually pushes air forward, rather than creating sound waves that move through it. On other planets, though, louder sounds are theoretically possible. Six years ago a man named Mr. Milton Banana (presumably not the late bossa nova drummer) posted to a discussion board asking, “Which would be louder — Krakatoa’s explosion or a Saturnian thunderclap?” No definitive answer emerged, but the best reply was the most practical one: “Depending on how close you are, you likely wouldn’t hear anything . . . ever again.”

Watch: An eruption in Papua New Guinea