“The Murray Hill anechoic chamber, built in 1940, is the world’s oldest wedge-based anechoic chamber. The interior room measures approximately 30 feet high by 28 feet wide by 32 feet deep. The exterior cement and brick walls are about 3 feet thick to reduce outside noise.”
Bell Telephone engineer in a research room designed to eliminate 99% of all outside sound. 1947 by Eric Schaal.
“The chamber absorbs over 99.995% of the incident acoustic energy above 200 Hz. At one time the Murray Hill chamber was cited in the Guinness Book of World Records as the world’s quietest room.”
Concert Hall acoustic simulation
“The chamber has also been used to measure loudspeaker and microphone directivity and frequency response functions, simulated concert hall acoustics and sound propagation over impedence surfaces. The invention of the electret microphone and further work in directional microphone systems were measured and verified in this chamber.” – via bell-labs.com
