A room in Building 87 of Microsoft's headquarters, which is located in Redmond, Washington, USA, is the quietest place on Earth. The room, which is an anechoic chamber, was built by Microsoft engineers to test newly developed equipment. In fact, the chamber is so quiet that physiological sounds can be heard, which is highly unusual. For example, individuals in the chamber reported hearing their joints grinding, hearts beating, and blood gushing through their veins. Background noise is estimated at -20.6 decibels, setting the official record as the world’s quietest place. To put that noise level into context, scientists estimate that a human whisper is about 30 decibels, the sound of human breathing is about 10 decibels, while the limit of human hearing is 0 decibels. The noise produced by air molecules colliding with each other at room temperature is about -24 decibels. The chamber achieves the limit of what is possible to achieve without creating a vacuum.
Anechoic Chamber Design
The anechoic chamber is cube-shaped and each side measures 21 ft. The design and construction of the chamber took nearly two years and identifying a suitable building involved almost eight months of testing. The chamber is located at the center of six concrete onion layers, and each layer measures 12 inches in thickness, which helps to cut about 110 decibels from reaching the chamber. The chamber also floats on 68 vibration damping springs which are fitted on a separate foundation slab that eliminates any contact with the surrounding building. Clusters of sound absorbent wedges, which are 4 ft long, line all six surfaces of the room to prevent echoes from bouncing off the walls when sound is produced inside the room. The floor consists of steel cables that are knitted together to form a net above the sound absorbent wedges at the bottom. Doors leading to the chamber, and those of the surrounding room, are lined with seals to prevent sound from leaking in.
Experts use the room for listening to electronic equipment and checking for vibrations made by capacitors when current passes through them. Results from such tests are used to identify sources of noise or hum, which can be unpleasant to customers. The chamber also helps in the detection and analysis of sounds produced by other electronic components, such as displays, cooling fans, speakers, and keyboards.
The anechoic chamber in Microsoft's Building 87 is not accessible to the public. However, those interested in experiencing a similar state of quietness can visit the world's second quietest place, which is located in the Orfield Laboratories in the US state of Minnesota. Visits to the anechoic chamber in the Orfield Laboratories can be booked online through the company's website, although it warns that most visitors cannot remain in the chamber for an extended period of time without supervision. The chamber has a background noise level that measures -9.4 decibels, which is less than the -20.6 decibel record set by Microsoft. The longest amount of time anyone has spent in the chamber at Orfield Laboratories is 45 minutes.