The anechoic chamber in Microsoft’s audio lab in Redmond, Washington is the quietest place in the world. The room, located in Microsoft’s Building 87 audio lab in Redmond, Washington, has been certified by the Guinness Book of World Records.

The anechoic chamber owes its silence to its construction. The walls are lined with sound absorbers that remove vibrations and dampen noise in the air and the room itself is separated from the rest of its building in order to keep noise and vibration at a distance. The resulting quiet is -20.3 decibels, jus 2.7 decibels short of -23, the sound of air molecules interacting and the quietest a non vacuum can be (on Earth anyway).

Used for voice recognition training and equipment testing, the chamber isn’t open to the public for good reason. Extended exposure to extreme quiet can have deleterious effects on one’s mental health. A similar chamber in Minnesota has witnessed a number of attempts by quasi-daredevils to sit in extreme silence. None of those attempts has lasted very long. It is, in short, deeply disconcerting to listen to air. Microsoft’s goals are, of course, more practical. The company wants to give tech a chance to hear the human voice with maximum clarity — and they’ve taken that logic to the extreme.