I'm afraid it's an urban myth albeit a very common one.
"A duck's quack doesn't echo" is a much quoted scientific myth. In spring 2003 it was quoted on Home Truths on BBC Radio 4 and Shooting Stars on BBC 2. You can listen to our sound files on Home Truths by going to the BBC4 web site and "listening again". Salford Acoustics was the source of the story being presented in the national and international media when we proved that a duck's quack does echo as part of the British Association Festival of Science.
The myth
So a duck's quack certainly echoes around our reverberation chamber, so a duck's quack does echo. Which leads to the most interesting question, why did the myth arise? The are a few possible explanations that I can think of:
The quack does echo, but it is usually too quiet to hear. When you want to hear an echo, you usually make a very loud noise to make sure the reflection can be heard. But a duck quacks too quietly, so the reflection is too quiet to hear.
Ducks don't quack near reflecting surfaces. You need a large reflecting surface, a mountain or building for the sound to reflect off. Maybe ducks don't hang around reflecting surfaces.
It is hard to hear the echo of a sound which fades in and fades out.
It has been widely quoted in incorrect lists of facts that a duck's quack does not echo. This statement is incorrect as a duck's quack does in-fact echo.
Wikipedia defines an echo as:
A reflection of sound, arriving at the listener some time after the direct sound. Typical examples are the echo produced by the bottom of a well, by a building, or in a room, by the walls. A true echo is a single reflection of the sound source. The time delay is the extra distance divided by the speed of sound.
In tests done in an echo chamber, it was proved that a ducks quack does echo. It only takes someone to be around a cliff populated with ducks to find this out. Which leads to the most interesting question, why did the myth arise? The are a few possible explanations that could explain it are:
The quack does echo, but it is usually too quiet to hear. When you want to hear an echo, you usually make a very loud noise to make sure the reflection can be heard. But a duck quacks too quietly, so the reflection is too quiet to hear.
Ducks don't quack near reflecting surfaces. You need a large reflecting surface, a mountain or building for the sound to reflect off. Maybe ducks don't hang around reflecting surfaces.
It is hard to hear the echo of a sound which fades in and fades out.