Maggie Koerth-Baker in FiveThirtyEight:
Q: I want to hear what the loudest thing in the world is! — Kara Jo, age 5
No. No, you really don’t. See, there’s this thing about sound that even we grown-ups tend to forget — it’s not some glitter rainbow floating around with no connection to the physical world. Sound is mechanical. A sound is a shove — just a little one, a tap on the tightly stretched membrane of your ear drum. The louder the sound, the heavier the knock. If a sound is loud enough, it can rip a hole in your ear drum. If a sound is loud enough, it can plow into you like a linebacker and knock you flat on your butt. When the shock wave from a bomb levels a house, that’s sound tearing apart bricks and splintering glass. Sound can kill you.
Consider this piece of history: On the morning of Aug. 27, 1883, ranchers on a sheep camp outside Alice Springs, Australia, heard a sound like two shots from a rifle. At that very moment, the Indonesian volcanic island of Krakatoa was blowing itself to bits 2,233 miles away. Scientists think this is probably the loudest sound humans have ever accurately measured. Not only are there records of people hearing the sound of Krakatoa thousands of miles away, there is also physical evidence that the sound of the volcano’s explosion traveled all the way around the globe multiple times.