The world's quietest room is -9 decibels and is quiet enough to hear your blood flowing. The silence is so maddening it can cause hallucinations and the longest anyone has been able to bear to the room was 45 minutes ! A Minnesota lab has a room that is said to be the quietest in the world. It's so quiet in fact that the only sound you'd hear is your own body. You can eavesdrop on your heart beating, your stomach gurgling - sometimes you can even hear your lungs. Orfield Laboratories president Steven Orfield told the Daily Mail when there's nothing to hear, the ear produces "auto emissive" noises, acting as a microphone and loudspeaker. "'In the anechoic chamber, you become the sound," he said. The walls are double, made of insulated steel, concrete and fiberglass acoustic wedges that are a metre thick (about 3 feet). The floor is mesh, "like a trampoline" all of which make the room 99.99% sound-proof. Orfield said the experience is definitely weird and many people who tour the room walk out within seconds. In fact, if you're in there for any length of time, you have to sit down because it can be so disorienting. Orfield said the longest anyone's held out is 45 minutes. In a study published in the Journal of Nervous and Mental Disease, subjects exposed to this type of chamber, for as little as 15 minutes in the dark, reported psychosis-like experiences. Generally though, the room is used for far less scary, more practical reasons. Orfield said many companies, such as Harley Davidson, use it to test how loud their products are. NASA uses a similar chamber for its astronauts, who are placed in a water-filled tank to see how well they respond to hallucinations. Guinness has recognized the room in Minnesota as the world's quietest chamber, but unofficially a chamber at the University of Salford in Manchester, England has claimed to record even lower decibels. In honour of the world's quietest rooms, we thought this musical tribute 4'33" by experimental composer John Cage would be appropriate. The musical score instructs the performer "not to play" for its duration, so the audience can hear and be aware of their environment. With all due respect to Simon