Mrs. Ort

According to the Guinness Book of Records, the anechoic chamber at Orfield Laboratories in Minneapolis is the quietest place in the world, with a background noise reading of –9.4 decibels. Very few people have been able to bear it for more than 45 minutes without experiencing discomfort, claustrophobia, nausea and panic. If you chatted with someone, your speech would measure around 60 decibels on a sound-level meter. If you stood quietly on your own in a concert hall, the meter would drop down to a level of about 15 decibels. The threshold of hearing, the quietest sound a young adult can hear, is about 0 decibels. The test room at Orfield Laboratories, like the chamber at Salford University, is far quieter than that. You can hear each grind, crunch and squeak your skeleton makes. An anechoic chamber has an impressive silence because it simultaneously presents two unusual sensations: not only is there no external sound, but the room puts your senses out of kilter. An anechoic chamber is often isolated from energy entering from their surroundings. This combination means that a person or detector exclusively hears direct sounds (no reflected sounds), in effect simulating being outside in a free field. Through their eyes, visitors obviously see a room, but their ears hear nothing that indicates a room. Add the claustrophobic drama of being enclosed behind three heavy doors, and some begin to feel uneasy and ask to leave. And what this kind of room is useful for? Anechoic chambers are designed to stop reflections or echoes of sound. They are commonly used in acoustics to conduct experiments in nominally "free field" conditions, free field meaning that there are no reflected signals. All sound energy will be traveling away from the source with almost none reflected back.