An echo is simply a reflection of the original sound wave which arrives at the listener with a delay after the original sound. Sound waves can be reflected, that is bouncing off objects in the same manner a solid object can bounce off the ground. The echo sounds entirely the same as the original sound but the direction of the sound is altered.
The things that a scientist should consider while observing
the force is the environmental conditions,the force that is expected to act on
the dam, the means to contain that force,
and compare different types of designs in accordance with the location
of the dam
