Reflected Sound Waves are Echoes
Reflected Sound Waves are Echoes | Echo can be Heard only after One-Tenth of a Second
When we shout in the hills, those sounds are again heard after few seconds of time. This is called an echo. Sound travels in the form of waves. From the source, sound waves scatter in all directions. When the sound waves are obstructed, they get reflected. Those reflected waves travel back and they were heard by us again. Actually every sound wave gets reflected when met with an obstacle. But we cannot hear the echo in all cases. To hear the echo, sound waves generated from us should come back after the minimum time interval of one tenth of a second. Based on calculations in that aspect, the obstacle of the sound waves should be at least at a distance of 17 meters from the source. Moreover, there should not be any obstacles in between source and final obstacle. These conditions are well satisfied in hilly areas, big temples, empty rooms, deeper wells. Hence when shouted in those areas, one can hear the echoes. Time interval for the hearing of echo depends on the distance between the source of sound and obstacle.