Reflection of sound or an echo: If we stand in front of a suitable reflecting object such as a tall building or a mountain and shout or clap our hands once, we will hear the exact sound repeat after a short moment.
Echo Definition: The repetition of the sound after reflection is known as an echo. An echo is distinct from the original sound because of the time delay between them.
0.1-second time difference is the minimum time required for the human ear to distinguish an echo from the original sound.
Total Distance Traveled: Hence, the total distance covered by the sound from the point of production to the reflecting surface and back should be at least distance = speed x time. Using the given values, this is calculated as:
- d = 340 m/s x 0.1 s
- d = 34 m.
This total distance of 34 meters represents the round trip from the source to the reflector and back to the listener.
Minimum Obstruction Distance: Thus, for hearing clear echoes, the minimum distance of the obstruction from the source of sound should be half of this distance, that is, 17 m. This is because the calculated total distance is a two-way trip,