Look at this amazing photo above the European Space Agency issued a few days ago. It was taken in one of the agency's anechoic chambers, in the "zone of silence" as the title of the press release says. So what is an anechoic chamber? It is an echo-free room where the walls coated with special materials absorb all reflections of sound or electromagnetic waves and insulate any noise coming from outside, thus it simulates a quiet open-space of infinite dimension, which is quite useful in the aerospace industry.
For your viewing pleasure here comes almost 30 images from air and space related anechoic chambers from around the world, from the most silent places on Earth.
ESA's Compact Payload Test Range (CPTR) for antenna testing in Noordwijk, The Netherlands. Metal walls form a ‘Faraday cage’ to block all external signals, isolating the facility from TV and radio broadcasts, aircraft and ship radars, and even mobile calls. Spiky foam cladding absorbs radio signals internally to create conditions simulating the infinite void of space.