This is the Benefield Anechoic Facility in Edwards Air Force Base: the largest chamber of its kind in the world—a room in which RF and sound signals don't bounce off the walls, so you can get clean radio frequency testing on all kinds of gear. In this case, electronic warfare systems in huge toys like Hercules, B-1B and B-2 bombers, Raptor fighters and all kind of airplanes.
The Benefield Anechoic Facility is a gigantastic 250 x 264 x 70-foot steel plate box inside a metal hangar building. Inside, 816,000 pyramidal foams absorb any RF signal so they don't bounce off the walls and the testing equipment gets a clear signal. Where do they put the toys? Either they hang them, as you can see in the gallery, or they put them in a 160-feet diameter 360-degree turntable that can support up to 1 million pounds of gear.
Quite frankly, they should stop the testing and start doing massive rave parties in there. [AudioJunkies]