This room in Building 87 at Microsoft's headquarters in Redmond, Washington, is currently recognized in Guinness World Records as the quietest room in the world, with a measured background noise of -20.35 dBA, 20 decibels below the threshold of human hearing.
Microsoft
Chambers like these are called "anechoic" because they produce no echo: sound is absorbed immediately by the walls and doesn't bounce back into the room.
Microsoft
Microsoft uses the chamber to test switches and functions in wide range of products, like keyboards and computers.
Microsoft
Hundraj Gopal, a speech and hearing scientist and the principal designer of the anechoic chamber at Microsoft, stands inside the room. Construction took one and a half years.
Microsoft
Anechoic chambers are all built with a similar structure. This one at Orfield Labs in Minneapolis, which is open to the public, is certified to have 1/20th of the noise level of a very quiet bedroom at night.
Orfield Labs
The Orfield Labs room was recognized as the quietest in the world in the Guinness World Records twice, in 2004 and 2012, before losing the title to Microsoft in 2015.
Orfield Labs
Both rooms are built like a nest of steel and concrete shells, disconnected from one another and separated by sound-absorbing empty layers. The walls are up to 12 inches thick.
Orfield Labs
The floor is made of wire mesh derived from the aviation industry, which reduces sound reflections.
