Silence machine. Professor Selwyn Wright listening to his silence machine. Wright developed his ECASS (Electronic Controlled Acoustic Shadow System) to cancel out unwanted sounds. This machine, like other silence machines, uses a computer to analyse the noise and generate a reverse sound to cancel out the original noise. The ECASS improves on other silence machines in that it can be used outdoors as well as indoors. It also casts its acoustic shadow over a wider area. Its projected cost is cheaper than conventional noise reduction methods. The ECASS is being developed at the University of Huddersfield, UK. Photographed in 2002.