The loudest sound in history
At 10:02 AM on August 27, 1883, the island volcano of Krakatau produced its final, cataclysmic explosion. The sound it generated is the loudest ever recorded in modern history. It was clearly audible as "the distant roar of heavy guns" up to 4,800 kilometers (3,000 miles) away on Rodrigues Island, near Mauritius. People in Perth, Australia, some 3,110 kilometers distant, reported hearing what sounded like artillery fire. In all, the sound was heard across 50 different geographical locations, covering an estimated 1/13th of the Earth's surface.
Closer to the eruption, the sound was a a physical force. A barometer at the gasworks in Batavia (modern-day Jakarta), 160 kilometers away, measured a pressure spike equivalent to 172 decibels. For comparison, the human pain threshold is around 130 decibels. Sailors aboard the British ship Norham Castle, located 64 kilometers (40 miles) from the volcano, had their eardrums shattered by the pressure wave. At the source, the sound level is estimated to have been 310 decibels—a level at which acoustic energy is a shockwave.