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".
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.
• Echoes happen because sound bounces off things.• You probably knew that already. But something else has to happen as well; just bouncing wont make an echo.• After all, you dont hear an echo when you yell in your bedroom, even though the sound is bouncing off the walls.
• 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 ... thats what makes it eerie.• For our purposes, lets 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?•
Remember that it must go out and then comeback to you. At 300 meters per second, or 150meters per half-second, it needs to travel at least150 meters in total ... or 75 meters out and 75meters back.As a result, to get a good echo, the sound mustbounce off something at least 75 meters away.Otherwise, it will return in less than half a second,and wont make a good echo.