Question

WHY DOES DUCK SOUND NOT PRODUCE ECHO? ​

Answer 1

Scientists have solved one of the acoustic world's riddles. It is a myth, they will announce today, that a duck's quack has no echo.
But they will also add, a trifle sheepishly, that the echo of a duck's quack is very difficult to hear.
Trevor Cox, of the acoustics research centre at the University of Salford, is an expert in techniques used to diffuse echoes. These are a challenge for station announcers, concert hall conductors, cathedral choirs and sound engineers.

So he was puzzled when he began to hear, on television and radio programmes, that a duck's quack did not echo and no one knew the reason why. He was galvanised into action when journalists began ringing him to find out if the recently minted myth was true.
Today he will reveal the results of his tricky experiments involving Daisy the Duck.
"If we are going to test a duck, we really need to know what a duck sounds like with no echoes - remembering that an echo is a late-delayed reflection from a surface like a cliff," said Prof Cox.
So first Daisy did her solo performance in an anechoic chamber - a space designed to suppress all sound reflection. The noise sounded just like a quack.
Daisy then repeated her aria in a reverberation chamber, designed to produce the kind of echo that Elvis Presley exploited with Heartbreak Hotel.
"The sound produced is rather sinister," Prof Cox said. "It does indeed echo, so we shouldn't be too surprised there."

The next question was: how did the myth arise? He decided to test the hypothesis in outdoor and concert hall conditions.
He could not take his web-footed friend on to the podium at the Royal Festival Hall, so he used a computer to put the duck in a virtual concert hall. The quack was prolonged, though not as drawn out as the one in the echo chamber.
The next step was to hear what a duck sounded like as its quack echoed off a cliff. This tricky topographical challenge, too, had to be solved with virtual reality. But it yielded a pleasing sound pattern, in which experts could see both the original quack and the reflection of the sound as it bounced off the "cliff".

"There is a small difference, but in this room it would be very difficult to hear," said Prof Cox. " This is the reason the myth arises. A duck's quack is rather quiet, and the echo isn't heard."