The quietest Room on earth?

 If you stand in it for long enough , you start to hear your heartbeat when you moves your bones make a grinding noise. Eventually you lose your balance , because the absolute lack of reverberation sabotages your spatial awareness.                                                                                             In this room of Microsoft's headquarters in Redmond , Washington , all sound from the outside world is locked out and any sound produced inside is stopped cold. It's called an "anechonic" chamber , because it creates no echo at all - which makes the sound of clapping hands downright ceric.                                                                                 The background noise in the room is so low that it approaches the lowest threshold theorised by mathematicians , the absolute zero of sound - the next step down is a vaccum , or the absence of sound.