Physics
Echolocation
Echolocation is a biological sonar system used by animals, such as bats and dolphins, to navigate and locate objects in their environment. It involves emitting high-frequency sound waves and then interpreting the echoes that bounce back. This process allows the animals to "see" their surroundings through sound, demonstrating the principles of wave propagation and reflection.
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5 Key excerpts on "Echolocation"
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eBook - ePub- Akihiro Miyauchi, Masatsugu Shimomura, Akihiro Miyauchi, Masatsugu Shimomura(Authors)
- 2019(Publication Date)
- Jenny Stanford Publishing(Publisher)
Chapter 14Ikuo MatsuoEcholocation of Bats and Dolphins and Its Application
Department of Information Science, Tohoku Gakuin University, Tenjinzawa 2-1-1, Izumi-ku, Sendai, 9813193, Japan [email protected]Bats and dolphins can use Echolocation, which is called “biosonar.” Bats emit high-frequency broadband sound waves to track and catch flying insects. They perceive the locations of these moving objects in 3D space. Also dolphins emit intermittently broadband ultrasound clicks. It is possible that such Echolocation capabilities of bats and dolphins are applicable to the improvement of the artificial sounders that are used in acoustic surveys and so on. In this chapter, I describe the biomimetic model for a bat’s Echolocation and echo sounder system using the dolphin-like broadband signal.14.1 Introduction
Bats and dolphins can use Echolocation, which is called “biosonar.” Bats emit high-frequency sound waves that enable them to track and catch flying insects [1 , 2 ]. They perceive the locations of these moving objects in 3D space using frequency modulation (FM). For example, Japanese house bats, Pipistrellus abramus , emit intermittently broadband ultrasounds, which sweep from about 100 kHz to 40 kHz within several milliseconds. It was shown that bats are capable of locating static objects at high signal-to-noise ratios (SNRs), achieving submicrosecond accuracy [3 , 4 , 5 , 6 ]. On the other hand, dolphins emit intermittently broadband ultrasound clicks of around 100 kHz with almost 100 μs duration. It was found that bottlenose dolphins (Tursiops truncatus ) can determine the target size, material, and shape [7 , 8 ] and object characteristics [9 ] from echoes by behavioral experiment. Both bats and dolphins can perceive objects by using broadband sonar signals. It is possible that such Echolocation capabilities of bats and dolphins are applicable to the improvement of the artificial sounders that are used in acoustic surveys and so on. In Section 14.2 , the biomimetic model of a bat’s Echolocation is described. In Section 14.3
eBook - ePub- Ken Vos(Author)
- 2013(Publication Date)
- For Dummies(Publisher)
For frequencies below 1,700 hertz (longer wavelength), the sound wave doesn’t notice the head and travels around it. The brain picks up the lag in the crests reaching one ear compared to the other ear, allowing the brain to determine the direction of the source of the sound. When the frequency is greater than 1,700 hertz (shorter wavelength), the head acts like a brick wall reflecting sound waves and preventing the sound waves from reaching the ear on the backside. The difference in the volume of the sound allows the brain to determine the direction of the source of the sound wave. 1,700 hertz is an arbitrary frequency because every head is slightly different and sounds don’t come directly from the side. The brain uses both techniques for sound between 1,000 hertz and 4,000 hertz.This technique is applicable to mammals in general, but the frequency range changes for each animal. Therefore, animals can determine the direction of the source of the sound. Animals that use frequency modulated Echolocation go beyond this and use the echo to estimate the direction and distance. Their ears tell them the direction the echo is coming back from, and the brain estimates the distance by knowing the time delay between the chirp from the mouth and the echo reaching the ear:The factor of 2 is present because the chirp has to leave the animal’s mouth, travel to the object (prey), bounce off the object (prey), and travel back to the animal’s ears. Understanding the Limited Range of EcholocationWhen an animal is using sound waves to locate dinner, the echo needs enough power to drive the eardrum, which means the Echolocation technique has limited range. Here I discuss a bat, although it’s true for any animal using Echolocation. To understand this limited range, a few reasonable assumptions are necessary:
- Michael D. Breed(Author)
- 2017(Publication Date)
- Academic Press(Publisher)
Chapter 151941 Bat Echolocation
Abstract
Bats use reflected ultrasound to navigate in unlit landscapes.Keywords
Sensory; biology; navigation; orientation; D. R. Griffin; R. GalambosThe Concept
Bats use reflected ultrasound to navigate in unlit landscapes.The Explanation
In the late 1700s, the Italian physiologist, Lazzaro Spallanzani discovered that bats do not use vision to navigate in the dark; his work suggested that sound played a key role in bat orientation. The exact mechanism by which bats navigate so well without light remained unknown until 1941, when Donald Griffin and Robert Galambos (Griffin and Galambos, 1941 ) found that bats avoid obstacles in the dark by being able to produce and receive sounds. They specifically use ultrasounds, which are sounds pitched too high for human ears to perceive. The sounds bounce back to the bats, giving them information about obstacles in their flight path; this is Echolocation . This discovery led to a rich field of inquiry about how bats use ultrasounds for navigation, social communication, and predation.A paper published in 1960 further revolutionized our understanding of Echolocation and stimulated the growth of sensory physiology as a field (Griffin et al. 1960 ). Donald Griffin asked a very interesting question—do bats use their Echolocation abilities to find very small prey items? He combined still and motion picture photography with sound recording to give accurate accounts of the events that occurred right before a bat captured an insect. From a 21st century perspective this does not seem too remarkable, but at the time it was quite a feat of precision technology to be able to deliver these measurements.So what happens when a 6 g (0.2 ounce) bat pursues a 2 mg (0.000007 ounce) fruit fly? The flies are clueless about the bat’s approach, as they cannot perceive the bat’s sounds. At a critical distance from the fly—about 50 cm (20 inches) the bat produces a high-pitched buzz that gives it the critical Echolocation information about the fly’s location. After that, its all over the for fly, as the bat’s and fly’s paths converge.
eBook - ePub- Hugh J. Foley(Author)
- 2019(Publication Date)
- Routledge(Publisher)
In fact, researchers had to develop extremely sensitive sound-recording instruments, so that they could unravel the complexities of bat spatial perception. Researchers have learned that echolocating bats actually emit very high-intensity signals (i.e., above 100 dB). However, those signals have a fundamental frequency above 20,000 Hz, which is why we can’t hear them in spite of all the energy. Various species of bats emit different types of signals. Some use a single frequency, combined with a sweep of frequencies, and others use only the sweep of frequencies (Moss & Sinha, 2003 ; Schuller & Moss, 2004). When they approach a flying meal, bats emit a series of very short bursts of sound, referred to as a feeding buzz. Echoes of those brief signals allow the bat to home in on its prey, especially against background clutter, such as vegetation (Moss et al., 2006). The bat is flying along as it emits sounds. Therefore, any returning echoes will be compressed, or Doppler-shifted, just as a train’s whistle changes pitch as it comes toward you (Behrend & Schuller, 2004). Because many bats emit calls with very high fundamental frequencies (e.g., above 20,000 Hz), they must be sensitive to even higher returning frequencies (e.g., above 60,000 Hz). Because of those high frequencies, interaural intensity differences play a vital role in Echolocation. Although bats have auditory systems that are basically the same as ours, differences in the outer ear, middle ear, inner ear, and brain produce these auditory capabilities (Vater, 2004 ; Vater & Kössl, 2004). Although the bat’s brain is roughly pea-sized, its auditory system is similar to that found in other mammals (Moss & Sinha, 2003). As you should predict, the inferior colliculus plays a vital role in Echolocation. Moreover, the superior colliculus contains a three-dimensional map of auditory space. Echolocation is a very sensitive navigational instrument
- Brent D. Ruben, Brent D. Ruben(Authors)
- 2018(Publication Date)
- Routledge(Publisher)
The ability of animals to find their way about where man cannot (e.g., bats and owls in the dark), and their aggregation, dispersion, or migration without signals that are obvious to us, have led to postulation of use of channels other than those already discussed. In the case of bats, the discovery of their use of ultrasonic pulses inaudible to man to guide their nocturnal flight made an extrasensory channel unnecessary as an explanation. This type of location of obstacles and prey, using a form of sonar (Echolocation), has now been found also in porpoises, sea lions, and oil birds. Some biologists consider it to be a type of autocommunication. It involves no supernormal receptive capacities, except possibly extended frequency ranges for hearing.Electrical and magnetic fields have been postulated many times as agents in animal behavior, but generally the evidence is negative. Recently, however, it has been shown that fish produce electrical discharges and have receptors for them. These are used as means for detecting objects in the external environment through alterations by the objects of the external fields. And, recently, reactions of various animals to magnetic fields have also been reported. It is difficult to see how an animal could produce magnetic signals, but the possibility is there.It is rather surprising that there are no reported cases of communication in thermal channels. It must be admitted that thermal changes would seem to have little virtue over other more readily controllable types. Thermal changes are hard to produce (almost impossible in water). They would have very short ranges, and they do not lend themselves to pulsed coding. It is possible that changes in body temperature in mammals during sexual excitement (the common language notes these with the term “in heat”) might be involved in courtship and mating, but so far no clear-cut evidence has been presented. Pit vipers have temperature receptors of astonishing sensitivity, capable of detecting differences of as little as 0.1 degree Centigrade between external objects. These are near the mouth and enable them to strike prey accurately. Similarly, mosquitoes respond to the heat given off by their hosts, and moths seem to respond to infrared emanations of food plants. But these cases would not represent communication in the usual sense. However, the generality of temperature sensitivity among animals and the existence of specialized thermoreceptors in many groups suggest that this channel for communication may be exploited too.
