Experts in acoustics have debunked one of the more esoteric myths of the modern age - that a duck's quack is the only sound that does not produce an echo.
The myth has been promulgated as fact by a number of television and radio shows, from Shooting Stars on BBC2 to Steve Wright on Radio 2 and John Peel's Home Truths on Radio 4.
Now scientists have definitively shown that the quack of a duck does obey the laws of physics and can, just like any other sound, produce an echo when it bounces off a solid surface.
With the help of Daisy the duck and an anechoic chamber - a room with jagged-edged walls where sound cannot be reflected - Professor Trevor Cox of Salford University precisely recorded the exact sounds that constitute a quack.
He then recorded Daisy's quack in a reverberation chamber with cathedral-like acoustics. This generated long reflections, causing Daisy's quack to take on a sinister echoey sound, Professor Cox said. "It proved that a duck's quack does, indeed, produce an echo."
The recordings were used to create simulations of Daisy performing at the Royal Albert Hall, and quacking as she flew past a cliff face. The conclusion was that a duck's quack definitely echoes, just like any other sound.
However, people could be forgiven for thinking that a quack does not echo because of the way that a duck's call tails off at the end, making any echo difficult to discern.
"The biggest mystery is why this myth should have arisen at all. One theory is that the envelope of the duck's quack has a gradual decay, which makes echoes difficult to hear," Professor Cox said.
"A duck quacks rather quietly, so the sound coming back is at a low level and might not be heard," he said.
"A quack is a fading sound. It has a gradual decay, so it's hard to tell the difference between the actual quack and the echo. That's especially true if you haven't previously heard what it sounds like with no reflections."
Another reason the belief might have grown is that ducks are normally found in open-water areas and seldom congregate around echoey cliffs.
"You'd have to find a mountain duck," said Professor Cox, who discusses his findings today at the British Association for the Advancement of Science at Salford University.Reuse content