The anechoic (meaning echo-free) chamber at Orfield Labs in Minnesota absorbs 99.99% of sound, making it the quietest place in the world, according to the Guinness Book of World Records. To absorb all possible noise, the chamber walls are made from 3ft of sound-proofing fibreglass wedges and insulated steel and concrete, and the floors are covered in a semi-permeable, trampoline-like mesh.