Echolocation

10 Key excerpts on "Echolocation"

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  Underwater Acoustics

  • Salah Bourennane(Author)
  • 2012(Publication Date)
  • IntechOpen

    (Publisher)

  Echolocation, often called biosonar, is used by bats and cetaceans (whales, manatees, dolphins etc.) using sound waves at ultrasonic frequencies (above 20 kHz). Based on the frequencies in the emitted pulses, some bats can resolve targets many times smaller than should be possible. They are clearly processing the sound differently to current sonar technology. Dolphins are capable of discriminating different materials based on acoustic energy, again significantly out-performing current detection systems. A complete review of this capabilities can be found in (Whitlow, 1993). Not only are these animals supreme in their detection and discrimination capabilities, they also demonstrate excellent acoustic focusing characteristics -both in transmission and reception. What we can gain from these animals is how to learn to see using sound. This approach may not lead us down the traditional route of signal processing in acoustic, but it may let us explore different ways of analyzing information, in a sense, to ask the right question rather than look for the right answer. This chapter presents a bio-inspired approach for ranging based on the use of phase measurement to estimate distance (or time delay). We will introduce the technique with examples done for sound in air than some experiments for validation are done in tank water. The motivation for this comes from the fact that bats have been shown to have very good resolution with regard to target detection when searching during flight. Jim Simmons (Whitlow & Simmons, 2007) has estimated for bats using a pulse signal with a centre frequency of about 80 kHz (bandwidth 40 kHz) can have a pulse/echo resolution of distance in air approaching a few microns. For this frequency, the wavelength ( λ ) of sound in air is about 4 mm, and so using the half wavelength ( λ /2) as the guide for resolution we see that this is about 200 times less than that achieved by the bat.

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  The Neuroethology of Predation and Escape

  • Keith T. Sillar, Laurence D. Picton, William J. Heitler(Authors)
  • 2016(Publication Date)
  • Wiley-Blackwell

    (Publisher)

  CHAPTER 5 The Biosonar System of Bats

  The main hurdle to using sound to locate objects is that it only works if the object of interest is making a noise. If animals keep still, they make very little noise and, since keeping still is a prime strategy for both ambush predators and alarmed prey, passive listening has its limitations. Furthermore, a passive listener does not necessarily know in advance what sort of noise an interesting object will make (squeak, rustle, grunt, thump, etc.), so it needs a rather generalised auditory capability to be prepared for a range of possibilities. Then it also faces the challenge that a noise of interest might be masked by background noise which swamps a broadband reception mechanism. The solution evolved by some animals is to use biosonar.

  In principle, this is very simple – send out a sound wave (‘ping’) into the environment, and then use the information encoded in the returning echo to locate objects of interest. Because the listener is also the noise-maker, it knows exactly what type of noise to listen for, and can develop specialised mechanisms to separate out that noise from background interference. The general mechanism is called Echolocation, and how it works is the subject of the present chapter. It turns out that biosonar requires particularly sophisticated computing hardware in the brain, and only a few animals have evolved a proper Echolocation capacity. However, two groups of mammals – bats and toothed whales – have done so, perhaps because, as mammals, they already possessed complex brains with an auditory cortex for evolution to act upon. Most of what we know about the neuroethology of Echolocation derives from experiments on bats, hopefully for fairly obvious reasons, so the focus of this chapter will be on this group.

  5.1 Bat Echolocation

  Echolocating bats belong to the order Chiroptera, a name deriving from Greek and meaning ‘hand wing’. Many bat species emit a series of ultrasonic pulses from their mouths or noses, and then detect the returning echoes to construct an auditory image of their environment. This image is used both for navigation and to detect potential prey. In this way, bats are able to exploit an ecological foraging niche of night-flying insects, in which they encounter little or no competition. Pursuing and capturing prey in flight is known as aerial hawking, and bats’ nocturnal prowess in this has made them highly successful; indeed, the Chiroptera rank among the most successful and diverse of all mammalian orders1 . Bats also glean – take stationary prey from leaves or the ground, and even trawl

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  Engineering Animals

  How Life Works

  • Mark Denny, Alan McFadzean(Authors)
  • 2011(Publication Date)
  • Belknap Press

    (Publisher)

  animal sonar 213 Echolocation systems to help them navigate in the dark, to help them locate moving prey, and to direct them toward their prey and move in for the kill. We will move, metaphorically speaking, from Echolocation basement to penthouse —from birds to bats—and while riding this elevator we will, along the way, learn more about remote sensor engineering in the animal world. Bird Echolocation We have seen that an echolocator emits sounds, which reflect back from the environment and are then processed; we saw earlier that this technique con-trasts with, say, the owls’ acoustic locating skills when silently hunting prey. In the jargon of acoustics engineers, owls and most other birds constitute passive sonar systems (only receivers—no transmitter), whereas echolocators are active sonar systems (receivers and transmitter). Microchiropteran (small insectivorous) bats and odontocete (toothed) whales are the best animals on the planet at Echolocation or sonar signal pro-cessing. Humans lag behind a little, but are catching up fast (bats have a head start of some 50 million years). Birds are also in the race, though a distant fourth, and are represented by two groups: the Oilbirds of South America and the family of cave swiftlets in South Asia and Australasia. Oilbirds ( Steatornis caripensis ) are quite big birds (they have a wingspan of 90 cm and weigh 400 g—one yard and 14 ounces); they are related to nightjars and live in cave colonies. They emerge at night to feed, locating the pungent fruit that forms the bulk of their diet by eyesight and perhaps also by smell. Thus Oilbirds never see daylight. To avoid bumping into one another and into the cave walls, they have evolved a simple type of Echolocation. It seems that Oilbirds echo-locate only within their caves—outside they rely on their excellent night vision. Cave swiftlets are much smaller birds (10 g—a third of an ounce) and, as their name suggests, they also live in caves, where they nest.

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  Contributions to Sensory Physiology

  Volume 6

  • William D. Neff(Author)
  • 2013(Publication Date)
  • Academic Press

    (Publisher)

  Griffin, 1944 ). Thus, the mystery of Spallanzani’s bat problem was finally solved.

  Since the early 1940s, investigations of the Echolocation system of bats have ramified into many different scientific disciplines such as ethology, mammalogy, neurophysiology, acoustics, and even the mathematical theory of signal detection. Consequently, many papers on the Echolocation system of bats have been published (see Busnel and Fish, 1980 ). The purpose of this contribution is to review only those studies in which I have participated.

  II Introduction

  Bats of the suborder Microchiroptera sense their environment by emitting ultrasonic signals and listening to the echoes. By analyzing the returning echoes with its highly developed auditory system, a bat can precisely adjust its flight pattern to catch prey or to avoid obstacles.

  Figure 1 is a simplified block diagram of the Echolocation system of a bat (Jen, 1982 ). Basically, the system consists of three parts: audition, vocalization, and orientation. Audition is responsible for the reception of the self-emitted signals, the returning echoes, and signals emitted by other animals. Vocalization produces species-specific airborne signals, and orientation regulates motor activities of different parts of the body to produce a specific flight pattern. To echolocate effectively these three parts should work coordinately so that a bat can (1) emit a repertoire of orientation signals and systematically change the signal parameters (duration, frequency, intensity, and repetition rate); (2) have its own ears protected from the intense self-emitted signals and yet remain highly sensitive to the returning echoes; and (3) coordinate activities of different groups of muscles for proper orientation. In short, Echolocation requires effective signal processing and highly coordinated motor activities.

  Fig. 1

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  Sonar Systems

  • N. Z. Kolev(Author)
  • 2011(Publication Date)
  • IntechOpen

    (Publisher)

  Part 3 Biology and Marine Science Sonar Applications 1. Introduction Sonar system operating in gas medium (air) are based on Echolocation phenomenon (active sonar). Many scientist and specialists in the field of air coupled ultrasound localisation systems have been inspired by Echolocation mechanism of bats. Those mammals mastered Echolocation perfectly using ultrasound waves. A resolution of so called real time biosonar is out of range of human made equivalent due to scientific and technological limitations. The main aim of the chapter presented below is to introduce book readers with the Echolocation mechanism, evolved in bats, which are an example of animals that have achieved perfection in biosonar usage. The next problem that authors cover is an evolution of sonar systems from simple one beam ranging Echolocation devices to advanced multibeam array beamformers operating with digital signal as serviceable form of information representation. Some properties of ultrasound waves in gas medium and physical phenomena involved with air coupled ultrasound waves generation, transmission and detection are described in the chapter as follows: (1) generation of ultrasound wave in gas medium, (2) a short review of air operating transducers including piezoceramics, sandwich, electrostatic, EMFi and MEMS, (3) problem of ultrasound wave transmission in gas medium (the influence of temperature and static pressure on speed of sound, attenuation in air) and range equation, (4) reception and detection of ultrasound waves, target strength. Considering the fact that the detection of echo signal does not give us an information about target a review of signal processing methods is also presented. Taking into account global trend in applying digital signal processing methods to sonar application authors describe some of DSP solutions which are adaptation of echo signal processing by bats at higher level of their auditory system.

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  The Fundamentals of Imaging

  From Particles to Galaxies

  • Michael Mark Woolfson(Author)
  • 2011(Publication Date)
  • ICP

    (Publisher)

  µs, the time discrimination in the auditory cortex of a bat is remarkable. It can align its flight with the direction of the target by making the sound arrive simultaneously at its two ears. For up-and-down directional information the bat depends on the physical structure of the ear itself. The ear has several folds in its surface and sounds coming from above and below strike these folds at different parts of the ear, giving different sonic signatures that the auditory cortex interprets as vertical direction. Other items of information provided by the auditory cortex are the size of the target, estimated by the strength of the returning signal, and the speed and direction of the motion by a combination of transverse speed of travel and radial speed from Doppler-shift information.

  Once the insect has been approximately located, the bat can start flying towards it; since it is a rapidly moving target the bat must make constant adjustments to its direction of flight. As it closes in, the requirements on the Echolocation system change. The configuration of the bat relative to the insect is changing very rapidly so it is necessary to receive information more frequently. To enable this to happen the pulse frequency is increased although the condition must always be satisfied that the interval between pulses must be greater than the return time for the echo pulses. In the final approach stage the pulse frequency is about 200 per second, giving a maximum detection range of 85 cm — but by this time the insect’s fate is sealed.

  Other creatures that make extensive use of Echolocation are the sea-mammals dolphins and whales, collectively known as cetaceans. They sometimes operate in murky environments, including deep under the sea or in muddy estuaries, and they can locate prey and obstructions by emitting sound pulses and detecting the echoes. Sound travels at more than 1,500 metres per second in seawater and can travel great distances — hundreds of kilometres — and still be detectable by a whale. The general principles that operate are similar to those that apply for bats. The emitted signals are in the form of clicks, one to five ms in duration, that are emitted at intervals of 35–50 ms, thus giving an Echolocation range of up to about 38 m. The rate at which clicks are emitted is increased as the distance between the cetacean and the target reduces. The direction of the target is assessed by the difference in the strength of the signal received by the ears, which are different from human ears in that they are located internally and sound is transmitted to them through bones or fatty cavities in the jaw region. Different species of dolphin and whale have slightly different characteristics in the frequency of the sound in the emitted clicks and the range of sounds they emit. Beluga whales, sometimes called sea canaries

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  Fundamentals Of Imaging, The: From Particles To Galaxies

  From Particles to Galaxies

  • Michael Mark Woolfson(Author)
  • 2011(Publication Date)
  • ICP

    (Publisher)

  Other creatures that make extensive use of Echolocation are the sea-mammals dolphins and whales, collectively known as cetaceans . They sometimes operate in murky environments, including deep under the sea or in muddy estuaries, and they can locate prey and obstructions by emitting sound pulses and detecting the echoes. Sound travels at more than 1,500 metres per second in seawater and can travel great distances — hundreds of kilometres — and still be detectable by a whale. The general principles that operate are similar to those that apply for bats. The emitted signals are in the form of clicks, one to five ms in duration, that are emitted at inter-vals of 35–50 ms, thus giving an Echolocation range of up to about 38 m. The rate at which clicks are emitted is increased as the dis-tance between the cetacean and the target reduces. The direction of the target is assessed by the difference in the strength of the sig-nal received by the ears, which are different from human ears in that they are located internally and sound is transmitted to them through bones or fatty cavities in the jaw region. Different species of dolphin and whale have slightly different characteristics in the fre-quency of the sound in the emitted clicks and the range of sounds they emit. Beluga whales, sometimes called sea canaries because of the twittering noises they make, have been extensively studied. They emit frequencies in the range 40–120 kHz, well above the human auditory range; the actual frequency seems to depend on the ambi-ent noise, the emitted frequency being as different as possible from that of the noise. Eleven different kinds of sound have been detected 260 The Fundamentals of Imaging: From Particles to Galaxies from Beluga whales, including clicks, whistles, squeals, chirps, mews, clucks, bell-like sounds and trills — all of which probably have some different information content for other Beluga whales.

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  Basic Mechanisms in Hearing

  • Aage Moller(Author)
  • 2012(Publication Date)
  • Academic Press

    (Publisher)

  In this area of behavioral discrimination experi-ments, as in the comparative neurophysiological ex-periments reviewed above, space has not permitted mention of all of the important experiments that have been reported, and the papers cited above will be rewarding to readers interested in appreciating the full capabilities of Echolocation as it has evolved in bats. The history of research on echolo-cation has included a long series of surprises in which the discovery of a new behavioral capability has opened our eyes to the probable existence of an unanticipated neural mechanism. Given the enthusi-astic momentum of so much new talent that has been attracted to these problems, I am confident that we are far from having reached the end of the road. References Airapetjantz, E. Sh., and Konstantinov, A.I. (1970). Echolocation in nature. Nauka, Leningrad. Airapetjantz, E. Sh., Konstantinov, A.I., and Mat-jushkin, D.P. (1969). Brain Echolocation mecha-nisms and bionics. Acta Physiol. Acad. Sci. Hungar. 35, 1-17. Bass, H.E., Bauer, 3., and Evans, L.B. (1972). At-mospheric absorption of sound: analytical ex-pressions. 3. Acoust. Soc. Amer. 52, 621-825. Bradbury, 3.W. (1970). Target discrimination by the echolocating bat Vampyrum spectrum. J. Exp. Zool. 173, 23-46. 879 DONALD FL GRIFFIN 880 Buchler, E. (1972). The use of Echolocation by the wandering shrew, Sorex vagrans Baird. Thesis. Univ. Montana. Missoula, Montana. Bullock, T.H., Grinnell, A.D., Ikezono, E., Kameda, Κ., Katsuki, Y., Nomoto, M., Sata, 0., Suga, N., and Tanagisawa, Κ. (1968). Electrophysiological studies of central auditory mechanisms in ceta-ceans. Z. Vergl. Physiol. 59, 117-156. Bullock, T.H., Ridgway, S.H., and Suga, N. (1971). Acoustically evoked potentials in midbrain audi-tory structures in sea lions (Pinnipedia) . Z. Vergl. Physiol. 74, 372-367. Bullock, T.H., and Ridgway, S.H. (1972). Evoked po-tentials in the central auditory system of alert porpoises to their own and artificial sounds.

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  Neuroethological Studies Of Cognitive And Perceptual Processes

  • Cynthia Moss, Sara J Shettleworth(Authors)
  • 2018(Publication Date)
  • Routledge

    (Publisher)

  In most animals, spatial information about objects is derived from the direct correspondence between the physical world and the topography of the brain. For example, the size, shape and location of a visual stimulus is conveyed by the relative activation of neighboring retinal areas that send projections to the retinotopically organized thalamic nuclei and primary visual cortical areas. Indeed, changes across a visual scene produce concomitant changes in activity across the surface of the brain (e.g. Tootell et al. 1982). However, for some animals, spatial information about the physical world cannot be obtained reliably through visual channels. One example is the echolocating bat, an animal that perceives the world through sensory experiences far removed from our own. The echolocating bat has evolved a biological acoustic imaging system which permits it to orient in the environment and capture flying insect prey in the dark. The bat emits ultrasonic sounds and listens to the echoes of these sounds reflecting off of objects in the path of the sound beam (Griffin, 1958). Echoes provide the bat with information about the size, location, and perhaps even the shape of a target, in effect allowing the bat to “see” with its ears.

  The focus of this chapter is on the bat’s target-ranging behavior and what psychophysical data on range discrimination can tell us about spatial information processing in bats. Specifically, it describes research findings that have allowed us to map the perceptual image of a sonar target perceived by bats, albeit the image of the simplest possible target, a point target that reflects an exact replica of the bat’s sonar emission. This chapter begins by providing a general overview of sonar signals used by bats and écholocation behavior in these animals. This introduction also briefly covers some theory on echo information processing, emphasizing research findings that pertain to the bat’s perception of a point target along the range axis.

  Echolocation Behavior

  Sonar sounds emitted by bats can be described broadly in terms of their frequency modulated or constant frequency components. Figure 11.1 shows some spectrograms of écholocation sounds made by different species of bats. Frequency is plotted on the Y-axis and time on the X-axis. Note that the bat’s écholocation signals are ultrasonic, i.e. above the upper limit of human hearing at around 20 kHz. In the spectrograms of Eptesicus fuscus’s and Phyllostomus hastus’s écholocation sounds, there is a rapid decrease in sound frequency over time. These are frequency modulated (FM) sounds. By contrast, the spectrograms of Pteronotus’s and Rhinolophus’s écholocation sounds show a constant frequency (CF) signal followed by an FM sweep. Overall, CF sounds are best suited to carry information in the frequency domain, referring to a representation based on which neural elements are activated in a tonotopically organized auditory system. By contrast, FM sounds are best suited to carry information in the time domain, referring to a representation based on the time-of-occurrence of neural discharges and the temporal pattern of neural firing in response to an auditory stimulus. The FM sweep of Eptesicus

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  Volume 2: The Flight of Bats. Morphologie und Funktion der sensorischen Systeme bei Chiropteren Aktivitätsperiodik der Chiroptera

  • Ulla M. Lindhe Norberg, Uwe Schmidt, Hans Erkert(Authors)
  • 2020(Publication Date)
  • De Gruyter

    (Publisher)

  A.; Lawrence, B. D. (1984): Echolocation and hearing in the mouse-tailed bat, Rhinopoma hardwickev. acoustic evolution of echo-location in bats. - J. Comp. Physiol. A 154: 347-356. Simmons, J. A.; Freedman, E. G.; Stevenson, S. B.; Chen, L.; Wohlgenant, T. J. (1989): Clutter interfe-rence and the integration time of echoes in the echolocating bat, Eptesicus fuscus. - J. Acoust. Soc. Am. 86: 1318-1332. Simmons, J. A.; Moss, C. F.; Ferragamo, M. (1990a): Convergence of temporal and spectral information into acoustic images of complex sonar targets per-ceived by the echolocating bat, Eptesicus fuscus. -J. Comp. Physiol. A 166: 449-470. Simmons, J. A.; Ferragamo, M.; Moss, C. F.; Steven-son, S. B.; Altes, R.A. (1990 b): Discrimination of jittered sonar echoes by the echolocating bat, Epte-sicus fuscus : the shape of target images in echoloca-tion. -J. Comp. Physiol. A 167: 589-616. Simmons, N. B. (1995): Bat relationships and the ori-gin of flight. - Symp. zool. Soc. Lond. 67: 27—43. Sisk, M. O. (1957): A study of the sudoriparous glands of the little brown bat, Myotis lucifugus lucifugus. - J. Morph. 101: 425-455. Sjöstrand, F. S. (1958): Ultrastructure of retinal rod synapses of the Guinea pig eye as revealed by three-dimensional reconstructions from serial sections. — J. Ultrastruct. Res. 2: 122-170. Starck, D. (1958): Beitrag zur Kenntnis der Armta-schen und anderer Hautdrüsenorgane von Saccop-teryx bilineata Temminck 1838 (Chiroptera, Embal-lonuridae). - Morphol. Jahrb. 99: 3-25. Stephan, H.; Pirlot, P. (1970): Volumetrie comparisons of brain structures in bats. — Z. Zool. Syst. Evol.-Forsch. 87: 200-236. Stephan, H.; Pirlot, P.; Schneider, R. (1974): Volume-tric analysis of pteropid brains. - Acta Anat. 87: 161-192. Sterbing, S. J.; Schmidt, U.; Rübsamen, R.(1994): The postnatal development of frequency-place code and tuning characteristics in the auditory midbrain of the phyllostomid bat, Carollia perspicillata.

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