In Salford, no-one can you hear you scream...
The sound of absolute silence is something that few people have ever experienced. But at the University of Salford, they've built the quietest place in the world.
The University's anechoic chamber is a perfectly soundless room which makes it ideal for testing very quiet products or people hearing very quiet sounds.
The chamber was featured on the popular science TV programme Bang Goes the Theory [Monday, 24 August] as the team recorded the sound of a pin dropping as part of an acoustics experiment.
Professor Trevor Cox is Professor of Acoustic Engineering at Salford. He says the anechoic chamber really is the sound of silence.
"If you look at sound, it's measured on the decibel scale," he said. "Your threshold of hearing is zero decibels. This room is measured at about minus twelve decibels."
How it works
To prevent sounds entering from outside, the chamber is actually a room within a room and sits on the kind of rubber springs that the Bridgewater concert hall in Manchester is built on.
Background noise level of the Salford chamber is -12.4dB
the world's largest anechoic chamber in California is used to test aircraft for the US Air Force
And to remove any sound reflections, or echoes, the chamber is lined from floor to ceiling with soft foam wedges which absorb any vibrations in the air.
Even the bridge leading into the chamber is attached to the outer but not to the inner wall, to stop vibrations entering the room.
Because of its extreme soundproofing, the room in the University's Newton building has been used to test the response of things like loudspeakers, microphones or ear protectors.
Final year project student, Patrick Froment used it measure the sound of a single raindrop to simulate the sound of rain falling on rooftops.
The Anechoic Chamber is part of the University of Salford's Acoustics, Audio & Video Department.