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A depiction of the ultrasound signals emitted by a bat, and the echo from a nearby object. Echolocation, also called bio sonar, is a biological active sonar used by several animal groups, both in the air and underwater. Echolocating animals emit calls and listen to the echoes of those calls that return from various objects near them. They use ...
Bats produce progressively shorter sounds, down to 0.5 ms, to avoid self-jamming when echolocating targets that they are approaching. [5] This is because echoes from nearby targets will return to the bat sooner than sounds from distant targets.
The idea that moths were able to hear the cries of echolocating bats dates back to the late 19th century. F. Buchanan White, in an 1877 letter to Nature [4] made the association between the moth's high-pitched sounds and the high-pitched bat calls and wondered whether the moths would be able to hear it.
When an echolocating bat approaches a target, its outgoing sounds return as echoes, which are Doppler shifted upward in frequency. In certain species of bats, which produce constant frequency (CF) echolocation calls, the bats compensate for the Doppler shift by changing their call frequency as they change speed towards a target.
Laryngeally echolocating bats, in general, produce ultrasonic waves with their larynx that is specialized to produce sounds of short wavelength. The larynx is located at the cranial end of the trachea and is surrounded by cricothyroid muscles and thyroid cartilage. For reference, in humans, this is the area where the Adam's apple is located ...
Echolocating bats couple sound production with the mechanisms engaged for flight, allowing them to reduce the additional energy burden of echolocation. Instead of pressurizing a bolus of air for the production of sound, laryngeally echolocating bats likely use the force of the downbeat of their wings to pressurize the air, cutting energetic ...
Frequency division (FD) bat detectors synthesise a sound which is a fraction of the bat call frequencies, typically 1/10. This is done by converting the call into a square wave, otherwise called a zero crossing signal. This square wave is then divided using an electronic counter by 10 to provide another square wave.
In addition to echolocating prey, bat ears are sensitive to sounds made by their prey, such as the fluttering of moth wings. The complex geometry of ridges on the inner surface of bat ears helps to sharply focus echolocation signals, and to passively listen for any other sound produced by the prey.