An echo is the reflection of sound caused when a sound wave bounces off a surface back to the listener. For an echo to be distinguishable, the sound needs to travel at least 75 meters away from the source and back, taking over half a second. This is because sound closer than that distance will overlap with the original sound and not be a separate reflection. Examples of echoes include those produced by wells, buildings, and enclosed rooms.

1. What is echo?
By- Master Rohan Chakraborty

2. Dictionary meaning of echo?
• ech·o/ˈekō/
• Noun: A sound or series of sounds caused by
the reflection of sound waves from a surface
back to the listener: "the walls threw back
echoes".

4. What’s exactly an ECHO?
• An echo Is a reflection of sound.
• Typical examples are the echo produced by
the bottom of a well, by a building, or by the
walls of an enclosed room and an empty
room. A true echo is a single reflection of the
sound source. The time delay is the extra
distance divided by the speed of sound.

5. • Echoes happen because sound bounces off
things.
• You probably knew that already. But
something else has to happen as well; just
bouncing won't make an echo.
• After all, you don't hear an echo when you yell
in your bedroom, even though the sound is
bouncing off the walls.

6. • The first requirement for an echo is distance.
• Sound travels fast ... about 300 metres in one second.
• A really good echo will return to you after several long
seconds ... that's what makes it eerie.
• For our purposes, let's suppose that any sound that
returns within half a second will overlap with your own
voice and not make a distinguishable echo.
So how far must an echo travel in order to return at
least half a second later?
•

7. Remember that it must go out and then come
back to you. At 300 meters per second, or 150
meters per half-second, it needs to travel at least
150 meters in total ... or 75 meters out and 75
meters back.
As a result, to get a good echo, the sound must
bounce off something at least 75 meters away.
Otherwise, it will return in less than half a second,
and won't make a good echo.