what are the avantages and disadvantages of echo and reverberation?

Advantage and disadvantage of Echoes and reverberation:

It can be useful or a nuisance. In a concert hall, echoes can ruin a performance if the walls and ceiling are not properly designed. If the walls are too hard, or too flat, they make good reflecting surfaces for the sound waves.

It can be used to give vital information. A sonar (Sonar stands for sound navigation ranging) device sends out high frequency sound waves from a ship to find out how close the vessel is to the sea bed. An ultrasound scanner, particularly known for giving images of the unborn baby, works in roughly the same way.

Bats use echoes to navigate as they fly in the night. This works on the same principle as sonar and ultrasound scanner. The bat sends out tiny, high pitched squeaks, which bounce off the objects in the bat's flight path. The echoes reach the bat, which then adjusts its course to avoid the obstacles. Many bats have very large ears to catch as much of the reflected sound as possible.

When animals such as bats and dolphins use echoes, it is called echo location. They use it to find their way around or to locate prey. Echo location describes the way of how some animals detect the size and position of objects around them

At night, bats use echolocation to guide them in flight. They send out tiny 'clicks', which bounce off objects and return to the bat. It builds up a 'sound' picture of its surroundings.