how is echo formed?????????
Echo is the second sound produced after reflection of sound waves on a rigid object . Echo is produced only if the distance between the object producing the sound and the reflecting surface is long Enough to allow the reflected waves to reach our ears 0.1seconds after the original sound is heard.this is because the sensation of hearing lasts only for 0.1 seconds after which the exciting stimulus ceases to act.
When you make a sound, you'll hear the sound waves the first time (when the sound travels from your vocal chords to your eardrum). Now, if there is a surface nearby, the sound will reflect from it, come back to you, and register in your eardrums a second time. This effect is called an echo.
You won't hear an echo in a small room, because the time between the first and second time the sound registers in your ear is too small for your ear to tell the difference.