"The duck's quack has no echo" runs a popular urban myth. How does this strange belief in a non-echoing quack arise?
Enter Trevor Cox , Professor of Acoustics at Salford University (Greater Manchester, UK) and Daisy the white duck. Daisy has quacked under test conditions. She has been tested in an anechoic chamber and in a reverberation chamber.
When Daisy is quacking in the anechoic chamber she sounds like any duck. However, in the reverberation chamber it is possible to change the acoustics to imitate those of different rooms or spaces. Once this is set to the acoustics of a large concert hall the sound is most odd. The Professor chose those of the Royal Festival Hall , a classical music venue by the National Theatre here. It is possible to discern an echo but the quack sounds most sinister, with a clashing sound like a dustbin (garbage)- can lid crashing.
The conclusions from all this is that the sound of the quack has 'a gradually decaying envelope' which means here that the sound of the echo is coming to us before the original sound has faded away. . This makes the echo difficult to hear as the sound is being masked in normal ( non-concert
) conditions. This seems the likely explanation for the belief.
Daisy's quack may be heard online ( hope this works !)
www.acoustics.salford.ac.uk/acoustics_world/duck/duck.htm That site gives a fuller explanation too.
