How does hearing help bats survive?

The eye sight of the bats is very poor. They do not need to see anything; when they fly in night. Survival of this mammal is totally depend on the faculty of hearing. They fly in the night and produce a sound. They get the echo of the sound produced by them. From this echo, they can locate the insects, flying in the air. They can eat the same as food. They can also locate the dangers and other objects, to protect themselves.