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  • What is an echo? Why an echo cannot be heard in a small room?

What is an echo? Why an echo cannot be heard in a small room?

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The sound which we hear after reflection is called echo or echo of sound. One can hear the echo by shouting loudly in a big hall. After shouting loudly, the same sound reaches the ears after reflecting from the surface of the wall. Echo of sound can be heard by producing sound at a place surrounded by hills or big buildings.

We know that persistence of sound in the human ears is 0.1 seconds. Thus, for a sound to echo, the minimum gap between the sounds to echo is 0.1 seconds.
Assuming the speed of a sound in an atmosphere of 22 degree celcius to be 344 m/s.
Now by using the distance speed time formula: speed = distance / time Or 344 = distance / 0.1
So, distance required for a sound to echo = 34.4m.
But in echo, the sound travels twice, i.e from source to an obstruction and back to the observer.

Thus, distance required for a sound to echo before reflecting from an obstruction = 34.4 / 2 = 17.2 or 17 m.
Since sound requires a minimum of 17.2 metres to echo, it is difficult to get this distance in a small room, that is why, echoes cannot be produced in a small room.

Posted by

shubham.krishnan

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