An echolocating bat registers each outgoing sound pulse and compares the originals to returning echoes. The time lapsed between generating the outgoing sound and receiving an incoming echo provides an accurate assessment of a target's distance from the bat. All microchiropteran bats produce echolocation calls using vocal cords in their voice boxes, or larynges. In contrast, echolocating Egyptian fruit bats make echolocation sounds by clicking their tongues. Different species broadcast calls in different ways, some emitting calls from the mouth and others through their nostrils.
Oral emitters fly with their mouths open, and nasal emitters fly with their mouths closed.
Remarkably, both kinds of bats can chew food and vocalize at the same time. Incoming sounds, including echoes, are collected by the bat's external ears, or pinnae, before they are funnelled into the rest of a bat's hearing system. The great variation in bat ear design reflects differences in sound-collecting ability and the requirements of different species, and this in turn reveals something about the diversity of bat echolocation strategies. Processing information from returning echoes involves an overwhelming array of complex operations in a bat's brain. In this respect, bats are biotechnical marvels, and not surprisingly, the subject of considerable study by biologists, medical doctors, the U.S. military, and others interested in the study of how animals hear.