CILIA - Customized Intelligent Life-inspired Arrays

Project funded by the Future and Emergent Technologies arm of the IST Programme in the 6th Framework Programme

6th Framework Programme
The Biosonar of Bats

Examples of bat biosonar systems studied in the project: Intermediate Roundleaf Bat (Hipposideros larvatus, profile and frontal view of noseleaf, top), Greater False Vampire Bat (Megaderma lyra, bottom left), and Harlequin Bat (Scotomanes ornatus, bottom right).

Biosonar is a sensory system which allows bats to live the life of active predators without depending for sight.

The biosonar system is a modified version of a hearing system which all mammals and humans have in common. At its center is an array of hair cells encapsulated in a fluid-filled compartment. Since sound cannot cross the border between air and the body fluids easily, a special apparatus (the middle ear) is needed to facilitate the transition. As a result, the hair cell array in the ear of mammals cannot by itself add spatial information to the incoming signal in the same way that is open to crickets and fish. To compensate for this, the external ears generate spatial information through a complicated diffraction process which depends on the direction of the impinging sound as well as on its frequency.

Bats use active as well as passive sonar. This means that they listen to the reflections of their own ultrasonic sonar pulses as well as to sound from other sources such as sounds through which prey animals may inadvertently betray their presence and location.