The discovery marks a resounding defeat for the previous record-holder for the longest echo found in a man-made structure, the Hamilton Mausoleum, also in Scotland, where the sound of the doors being slammed shut took 15 seconds to die away to silence.
Guinness World Records has certified the findings made by Trevor Cox, Professor of Acoustic Engineering at the University of Salford and author of Sonic Wonderland: A Scientific Odyssey of Sound. Prof Cox had received a tip that the Inchindown complex near Invergordon might prove fertile territory for an echo test. Excavated out of solid rock between 1939 and 1941, the tanks were dug deep into the hillside amid concerns about the strengthening of Germany’s armed forces and the threat posed by long-range bombers.
The tunnels were to provide a huge bomb-proof reserve supply of furnace oil for the warships of the home fleet at Invergordon, a key Royal Navy anchorage. Prof Cox had to enter the tank through one of the 18 inch diameter oil pipes because there are no doors. The tank was designed to hold 25.5 million litres of fuel and has walls 45 cm thick. The space is about twice the length of a football pitch, 9m wide and 13.5 metres high.
Allan Kilpatrick, an archaeological investigator for the Royal Commission on the Ancient and Historical Monuments of Scotland, fired a pistol loaded with blanks about a third of the way into the storage tank. The results stunned Prof Cox, who recorded the response picked up by the microphones about a third of the way from the far end. “It was like going underground into a Bond villain’s lair. But never before had I heard such a rush of echoes and reverberation,”; Prof Cox said. “I started off just playing around, whooping and hollering. The sound just goes on and on and on.”;
“Then when we fired the pistol my initial reaction was disbelief; the reverberation times were just too long. I knew immediately we had a new world record.”
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