The ears and brain cells in bats are especially tuned to the frequencies of the sounds they emit and the echoes that result. The middle ear muscle relaxes 2 to 8 ms later. At this point, the ear is ready to receive the echo of an insect one meter away, which takes only 6 ms. The external structure of bats' ears also plays an important role in receiving echoes. The large variation in sizes, shapes, folds and wrinkles are thought to aid in the reception and funneling of echoes and sounds emitted from prey.
Echolocation is a highly technical and interesting tactic.
To truly understand the concepts and complexity of this subject is to begin to understand the amazing nature of these animals. For interested readers, an excellent resource is M. Brock Fenton's book Bats .