Have you ever been in a big, empty hall and heard your own voice repeated back to you? Congratulations, you’ve heard an echo! But have you ever wondered why echoes happen and what it takes to hear them? In this article, we’ll explore the science behind echoes and what conditions need to be met to hear them.
An echo is defined as the repetition of sound caused by the reflection of sound waves from a hard surface back to the listener. When we speak or laugh in a big empty hall, our sound waves get reflected from the walls of the hall back to us. This reflected sound that we hear is called an echo.
However, it’s not always easy to hear an echo. There are two ideal conditions that need to be met. Firstly, the time gap between the original sound and the reflected sound or echo should be at least 0.1 seconds. This is because when we utter sounds, some of our sound waves get reflected while some get absorbed. If the reflected sound waves reach our ears before the completion of 0.1 seconds, then our brain does not perceive the original and reflected sounds as separate sounds, and they are interpreted as one sound.
The second condition for an echo to be heard is that the minimum distance between the speaker and the reflecting surface should be at least 17.2 meters. When the distance is 17.2 meters and we start speaking, and the original sound reaches our ears at this time, the reflected sound should reach our ears at least 0.1 seconds later. This way, we will be able to hear an echo.
However, if there are soft furnishings like sofas, carpets, curtains, etc., in the room, they absorb most of the sound waves, and the sound waves do not get reflected. As a result, we are not able to hear an echo in such a room. Hence, if we want to hear an echo, there should be minimal use of such sound-absorbing materials.
In conclusion, echoes happen when sound waves get reflected from a hard surface back to the listener. To hear an echo, two conditions need to be met – the time gap between the original sound and the reflected sound or echo should be at least 0.1 seconds, and the minimum distance between the speaker and the reflecting surface should be at least 17.2 meters. So, next time you’re in a big empty hall, try and hear an echo, and impress your friends with your knowledge of the science behind it!