Echo is most commonly heard in mountains and valleys.Why?

Answer 1

echo is to hear the sound you make again after sometime
you have no something to understand this
the sound is kept in our ears for 0.1 s. so during this time even if the sound reflects back to us we wouldn't notice it.
so for us to sense the reflected wave it should be heard after some time. So the distance to the reflecting surface should be more than a specific value.

if the reflecting surface is x m s away
S = ut
2x = 340 * 0.1 -------------the wave have to go and come again that's why we use 2x for S
x =17 m
so the reflecting surface of the sound wave should be at least 17m s away.
that's why we don't hear echo's in small distances.

Now you should be wondering there's many other places which you don't hear echoes where the reflecting surface is more than 17 m away.
the reason is the wave should go the distance and come back to you without losing it's energy. and the distance shouldn't very much more than the specified value if that happens the sound waves energy get distributed to a larger area and it's intensity decreases when sound intensity become very low you wouldn't be able to hear the sound. Also when it interfere with many other sound's you woudn't be able to identify it.

In the places you stated reflecting surfaces are finely available and there is no other sound's to interfere with it and you can hear the echoes easily.

Answer 2

Echo is heard only if the reflecting surface is flat, large and at least 17 m away from the source of sound. This is found only in hilly areas not in cities. Hence echo is commonly heard there.

Answer 3

An echo is like a reflection of sound. Mountainsides provide a surface against which sounds can reflect or bounce and get redirected back to the source.

In flat terrain, sound waves merely carry on until they dissipate.

Answer 4

You need something to reflect the sound wave back to the source. Mountains and valleys have enough "reflectors" to do this. On a flat terrain, the sound wave is not reflected back.

Answer 5

sound waves bouncing of hard surfaces . The same thing will happen in an empty room, but you do not notice it as much as the rebounding sound waves have less distance to travel and return to your ears sooner

Answer 6

Because that is where it works.