A specially built audio lab at Microsoft's headquarters in Redmond, Washington has just been declared the quietest place on the planet by the Guinness World Records. The silence inside the anechoic ("free from echo") chamber has been measured at -20.6 dBA (decibels A-weighted), and that's "unimaginably quiet", according to testers.

Building 87 on the Microsoft campus actually has three anechoic sound chambers, but the largest and the quietest sits on its own foundation of springs to keep vibrations to an absolute minimum.

The tech giant developed these chambers in order to test its devices and audio technology, and along the way it's managed to smash through the previous record for silence: -13dBA, recorded at the Anechoic Test Chamber at Orfield Laboratories in Minneapolis in 2012.

The walls of the room are covered in wedges made of sound-proofed material, designed to absorb every last drop of sound vibrating through the chamber. "All the sounds are absorbed," says Microsoft's Gopal Gopal. "To give you a rough idea, the Brownian motion - that is, a random air particle in space - is around -23dBA. You can't get any quieter because that's just the air particles moving. We are on the edge of what [are] the limits of physics."

Human beings can hear all the way down to zero decibels, and anything below that is beyond the scope of our ears, so to hit -20.6dBA is an impressive achievement. At the moment, Microsoft's engineers are using Building 87 to improve the Cortana digital assistant app, training the underlying software to better handle audio inputs and outputs. 

Noise reduction technology is improving all the time: the Guinness World Records reports that back in 2004 the record was -9.4dBA. How close we can get to the -23dBA 'floor' remains to be seen, but that's only a theoretical baseline - in the vacuum of deep space, without any moving air particles, it might be possible to go even lower.

It's unlikely that Microsoft is going to be offering tours any time soon: at that level of quiet, our ears adapt to take in every small sound, and the noise made by our own bodies quickly becomes disconcerting. In other words, you become the sound.