The Longest Echo Ever Recorded Lasted 112 Seconds

Hidden deep beneath the Scottish Highlands lies a relic of World War II: the Inchindown oil storage tanks. This colossal, bomb-proof facility was constructed in secret to hold a massive fuel reserve for the Royal Navy. While its original purpose is now obsolete, the vast, cavernous space has an unintended and record-breaking characteristic. Its enormous size, nearly twice the length of a football field, combined with perfectly smooth, non-porous concrete walls, created an environment unlike any other on Earth for sound to travel.

In 2014, acoustic engineer Trevor Cox ventured into one of the tanks to measure its properties, firing a blank from a pistol to create a sharp report. The resulting sound waves, with nowhere to escape and little to absorb them, reflected between the hard surfaces thousands of times. This phenomenon, known as reverberation, is the persistence of sound after its source has stopped. In a typical room, sound energy is absorbed by soft surfaces and fades in a second or two, but in the near-perfect reflective chamber of the tank (Review), the sound decayed incredibly slowly, sustaining for a full 112 seconds and shattering the previous world record of 15 seconds.