Explain how echoes are used by bats to judge the distance of an obstacle in front of them.

To help them find their prey in the dark, most bat species have developed a remarkable navigation system called echolocation. Bats use echo in this process .A bat emits a ultrasound waves and listens carefully to the echoes that are returned. The ultrasound pulses are not echoed if way is clear. The bat's brain processes the returning information the same way we processed our shouting sound using a stopwatch and calculator. By determining how long it takes a noise to return, the bat's brain figures out how far away an object is. They compare the volume of echoes in their right and left ears, and turn away from the louder echo, since that obstacle would presumably be nearer this method allowed bats to avoid obstacles using just the first millisecond of the echo as a signal.

The figure below depicts the whole process.