Text: Problem Solved - Daisy's Quacked It By Roger Highfield, Science Editor and David Derbyshire The Telegraph - UK 9-8-3 Daisy the duck has helped a professor of acoustics solve the puzzle of whether quacks echo, Europe's largest general science meeting will be told today. " 'A duck's quack doesn't echo, and no one knows the reason why,' is an oft-quoted phrase," said Prof Trevor Cox of the University of Salford. Daisy's quack is analysed in a recording studio Today, Prof Cox will tell the British Association in Salford that his quack research has revealed that there is some truth to this myth, after putting Daisy through her paces at The Acoustics Research Centre at Salford and recreating her as a "virtual quack". Despite problems caused by droppings, Prof Cox managed to record Daisy's quack in an echo-free anechoic chamber, then compare it with the noise in a reverberation chamber. "Given the right conditions a duck quack really echoes. The sound produced is rather sinister," he said. But where did the myth of the echo-free quack come from? Prof Cox uncovered the secret while simulating the sound of the quack, creating a virtual quack and then seeing how it fared near a cliff by a technique called auralisation, the acoustic equivalent of visualisation. "Placing our virtual duck close to a large cliff clearly produces an echo," he said. Lay people found this surprising, he added, explaining that the reason might be because of the shape of the quack sound. A quack has a gentle decay. As a result, its echo fades so quickly that it is "rather difficult to hear". "This is the reason the myth arises," said Prof Cox. He specialises in developing ways to prevent echoes in stadiums, railway stations and churches, where they make announcements difficult to understand. Rather than absorb sound, which reduces overall volume, he diffuses the sound with corrugated surfaces and "sonic crystals", a set of reflecting objects (such as spheres). © Copyright of Telegraph Group Limited 2003. http://www.telegraph.co.uk/news/main.jhtml?xml=/news/2003/09/08/n sci08.xml&sSheet=/news/2003/09/08/ixhome.html

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