Answer: Redmond, Washington

There are places on Earth that are naturally quiet due to their isolation and lack of environmental disturbances, such as the barren snowfields of Antarctica or the sprawling and deep limestone caves located under the U.S. state of Kentucky. As eerily quiet to the human ear as these places are, however, they’re practically a busy city street compared to the silence found in a man-made chamber located in Redmond, Washington.

In Building 87 on Microsoft’s campus, you’ll find an anechoic chamber—a space designed to absorb and isolate sound—built by Eckel Industries and certified by the Guinness Book of World Records as the quietest place on Earth in 2015. The chamber is so effective that the ambient level of noise inside is actually -20.6 decibels. To put that in perspective, the ambient sound level of a person in a very quiet room breathing as a resting rate is around 10 decibels and a very quiet library is between 30-40 decibels. So why would Microsoft want to create a room this quiet? They use it to test various devices and products to create quieter and more user-friendly products.

Visitors to anechoic chambers report that it can be extremely disconcerting to spend any length of time in them since the walls do such an effective job of absorbing even the tiniest environmental sounds (like the rustling of clothing or a cough). The silence disorients the brain enough that some people report vertigo, nausea, and other unpleasant reactions while standing inside the chambers. To give you an idea of how odd of an experience it is: it’s one of the few places on Earth (outside of other anechoic chambers that is) where you can listen to your own heartbeat without a stethoscope.

Photo by Andrew Eckel/Wikimedia.