Anechoic chamber at the Harvard Acoustics Research Laboratory. "An anechoic chamber is also a kind of prosthesis, serving to eliminate sound reflections in a room. Bell Labs built the first one, and Harvard's Acoustics Research Laboratory also built one.
This is the world’s quietest room. Located in US, this room blocks about of the sound you usually hear. You can even hear your blood flowing and stomach gurgling when siting in this room. No person EVER has been able to spend more than 45 minutes here.