The sound of absolute silence is not what you’d expect. Inside Microsoft’s headquarters in Redmond, Washington, engineers have pushed acoustic science to its absolute limits, designing the quietest room in the world, completely cut off from any outside sounds. Those who enjoy their peace and quiet may rejoice at the thought of spending their Sunday afternoons in such a soundproof chamber, but the reality couldn’t be farther from the truth.
Rather than a blissful experience, the sheer lack of sound is actually unbearable, drawing attention to your bodily functions that are usually muffled by background noise, such as the sound of your own heartbeat or even the sound of blood pumping through your veins. Nobody has been able to bear more than an hour inside this room, could you?
The room designed by Microsoft in 2015 is what’s known as an “anechoic” chamber, which literally means “without echo”. Lining the inside of the room on all six sides are deep, fiberglass wedges whose shape was calculated to absorb and dampen certain frequencies. They cover a double wall of insulated steel and foot-thick concrete. The floor is made of steel cables that join together to form a trampoline net so that people may walk above the foam wedges.
Seals around the door and the surrounding rooms add an extra layer of insulation. Even the air conditioning and sprinkler system were specially built inside the concrete wall of the room so that they wouldn’t interfere with the acoustic damping.
As a result of this setup, 99.99% of sounds are absorbed, rendering them virtually silent to the human ear. Even if a jet was to take off right next to the building, you wouldn’t hear more than a whisper inside this bunker of silence.
Inside the echoless chamber, background noise measures negative decibels, -20.6 dB, well below the threshold of human hearing (0 dB). For comparison, a quiet bedroom measures 30 dBA. Since the decibel scale is logarithmic, this means the anechoic chamber is about 600 times quieter. That’s as close to absolute zero sound you can get without entering a vacuum.
Thanks to this staggering silence, Microsoft’s Redmond anechoic chamber was awarded the record for the quietest spot in the world by the Guinness Book of Records. Previously, the record-holder was an anechoic chamber developed at Orfield Laboratories in Minneapolis, which was around 10 times noisier at -9.4 dB.
All of this is to say that this chamber is too quiet for its own good. Most people don’t enjoy loudness, but if it’s too quiet, that messes with our body.
Our ears aren’t only good for identifying sounds and their sources. Loop-shaped canals in your inner ear contain fluid and fine, hairlike sensors that help you keep your balance. With no reverberations, our inbuilt spatial awareness is thrown off balance and you start feeling dizzy. But first, the silence manifests itself as an unbearable ringing in your ears, which is why most people don’t want to stay inside for more than a few seconds.
If the dizziness and the ringing of the tinnitus don’t get to you, you may feel disturbed by the sounds of your body. You’ll start hearing your heart beating, your stomach gurgling loudly, and even the grinding of your own joints as you perform simple movements. In the anechoic chamber, you become the sound.
However, Microsoft engineers didn’t design the room with torturing people in mind. The lab is nestled deep in Building 87, Microsoft’s iconic research facility where products such as Xbox, Hololens, or Surface have been developed in the past. The specially constructed chamber was originally meant for testing new equipment Microsoft was experimenting with. Capacitors and other electronic components produce tiny vibrations as current passes through them, and the objective is to minimize the noise they produce as much as possible. Microsoft engineers also used the chamber to test techniques meant to replicate 3-D sound for its virtual reality HoloLens display.
If you’re still curious about experiencing an anechoic chamber, the Orfield Laboratories room, the second quietest in the world, is open to the public and has become a tourist hot spot.