The world’s quietest place is a match for the senses. You can hear your own heartbeat and the subtle movement of your bones rubbing together. The place is in an anechoic chamber, and it pushes the outer boundaries of sound.
This anechoic chamber, which means “no echo,” is located at Microsoft headquarters in Redmond, Washington, and it’s used to test microphones, speakers, and Cortana, Microsoft’s speech recognition software. The room broke the Guinness world record for the world’s quietest place on Earth in 2015 when it registered sound at an incredible -20.35 decibels (dB). It shattered the previous record held by Orfield Laboratories in Minneapolis, Minnesota, whose anechoic chamber measured -9.4 decibels. Their room was able to absorb 99.99% of the sound. Microsoft’s chamber clearly absorbs even more than that.
To put these numbers from Microsoft and Orfield Laboratories in perspective, rustling leaves measure at 20 dB (the decibel unit used to measure the intensity of a sound), and breathing is 10 dB. What is more incredible is that the theorized sound of Brownian motion, the random movement of particles in a gas or liquid, is measured at -23 dB. The only thing quieter than this is a vacuum, which has no sound at all. Zero decibels are theoretically the lowest an average human ear can hear.
The world’s quietest place at Microsoft has some unique engineering and design feats behind it that allow it to reach these super quiet levels. The anechoic chamber is surrounded by six layers of concrete, each 12 inches thick, that block outside noise. The room sits on 68 springs that dampen vibrations, and these are attached to a foundation independent of other rooms and buildings. The anechoic chamber is essentially a floating, enclosed cube.
The room is entered through a vault-like door that is connected to an adjacent room by a small gangplank. The room’s interior is fitted with sound-absorbing acoustic fiberglass wedges on the walls and ceiling, and the floor is made from a lattice of steel cable that has fiberglass wedges underneath. All these things absorb as much sound as possible in the room.
It’s so quiet in the room that you can hear sounds from your stomach, heart, and lungs, and even sounds that your ears make when sound is absent. The other senses are amplified without the reflection of sound off the walls. Without these reflections, balance can be affected, making someone feel unstable since cues for a person to orient are absent. Many people can’t last more than a few minutes, and some people can’t even make it inside the room at all. The complete disorientation is just too much for their systems to handle. One person was said to be able to handle the environment for about an hour, but it was reportedly done for charity.
The room isn’t just there to be the world’s quietest place. It is used to test the noise produced by various products so it can be isolated and corrected before being used in real-world applications. There are many anechoic chambers all over the country doing the same thing, testing the noise given off from products, so we’re not all inundated with noise. There are also radio frequency (RF) anechoic chambers that are similar to acoustic anechoic chambers. These chambers, however, are covered with radiation absorbent material instead of acoustic absorbing wedges and measure things like radar and antennas.