Largest anechoic test chamber

The Benefield Anechoic Facility at Edwards Air Force Base, California, USA, is a vast echo-free chamber whose interior surfaces do not reflect sound or electromagnetic waves. Constructed in 1988–1989, it is used for testing various aerospace and defence projects including aircraft, tanks and air defence systems. It measures 264 x 250 x 70 feet and has a volume of 4.62 million cubic feet. It is also insulated from external noise.