Washington: If you stand in it for long enough, you start to hear your heartbeat. A ringing in your ears becomes deafening. When you move, your bones make a grinding noise. Eventually you lose your balance, because the absolute lack of reverberation sabotages your spatial awareness.
In this room at 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 ‘anechoic’ chamber, because it creates no echo at all — which makes the sound of clapping hands downright eerie.
The background noise in the room is so low that it approaches the lowest threshold theorized by mathematicians, the absolute zero of sound — the next step down is a vacuum, or the absence of sound.
An anechoic chamber is literally a chamber without an echo. It’s a room that’s been designed in such a way that it cuts out almost all noise inside. And no, we don’t mean that you just won’t hear the birds or people outside or anything of the sort. It’s in fact so quiet that you can hear your own heartbeat, the creaking of your bones as you move, the blood pumping in your veins.
There is so little ambient sound in the anechoic chamber that it approaches the lowest audio threshold known to man, that of vacuum. This is done using a number of design tricks.
Firstly, six layers of concrete and steel insulate the room from outside sound. Meanwhile, vibrations are diminished by setting the room on a foundation of damping springs. Indoors, wedges of fibreglass cover the walls and ceiling of the room, to break up sound waves before they bounce back and absorb them. Even the floor a giant net, suspended above sound-absorbing material.
The design and construction of the room took a little over a year and a half, but the effort has paid off. Previously, the quietest place in the world was an anechoic chamber at Orfield Laboratories in Minneapolis, with a sound level of negative 9.4 decibels. By comparison, Microsoft’s chamber reads -20.3dBA.
To make a comparison, a whisper measures about 30 decibels, while steady breathing registers about 10 decibels. Essentially, the sound level in Microsoft’s anechoic chamber is about 20 decibels below the threshold of human hearing. It’s not something you might notice, except for a feeling of a pressure against your ears, similar to if you’re deep underwater.
While Microsoft’s chamber is quieter than the one in Minneapolis, it’s not open to the public. And while the latter uses it for research into hearing disabilities and neuro-degenerative conditions, Microsoft instead uses its chambers to test electronic devices like microphones, headphones, and speakers, or even the hum from displays and fans within devices. It’s Surface tablets, Xbox, and HoloLens headset have all been tested here.