If LeSalle Munroe stands still for a few moments in his “office”, something unsettling can happen – he can hear the blood rushing around his body and his eyes squelch as they move in his skull.

While many people work in places filled with the tip-tap of keyboards, the hubbub of chatter from colleagues and a constant hum of computers, Munroe is surrounded by almost total silence. His office is the quietest place on the planet.

The specially constructed chamber is hidden in the depths of Building 87 at Microsoft’s headquarters in Redmond, Washington, where the firm’s hardware laboratories are based. Products like the Surface computers, Xbox and Hololens have all been developed here. Microsoft’s engineers built the room – known as an anechoic chamber – to help them test new equipment they were developing and in 2015 it set the official world record for silence when the background noise level inside was measured at an ear-straining -20.6 decibels.

To put that in context, a human whisper is about 30 decibels while the sound of someone breathing normally comes in at just 10 decibels. It gets close to the limit of what should be possible to achieve without creating a vacuum – the noise produced by air molecules colliding with each other at room temperature is estimated to be about -24 decibels. The limit of human hearing is thought to be around 0 decibels, although just because our ears cannot pick it up, it does not mean no sound present, hence it is possible to get a negative value.

“It is a very unique experience inside with the door closed,” says Munroe. “When you stop breathing, you can hear your heart beating and the blood flowing in your veins. I don’t stay inside with the door closed very often.”