The 21st century is the century of radio electronics, the atom, the conquest of space and ultrasound. The science of ultrasound is relatively young these days. At the end of the 19th century, P.N. Lebedev, a Russian physiologist, conducted his first studies. After that, many outstanding scientists began to study ultrasound.
What is ultrasound?
Ultrasound is a propagating wave that is made by particles of the medium. It has its own characteristics, which differ from the sounds of the audible range. It is relatively easy to obtain directional radiation in the ultrasonic range. In addition, it focuses well, and as a result, the intensity of the vibrations performed increases. When propagating in solids, liquids and gases, ultrasound gives rise to interesting phenomena that have found practical application in many fields of technology and science. This is what ultrasound is, the role of which in various areas of life is very large today.
The role of ultrasound in science and practice
In recent years, ultrasound has begun to play an increasing role in scientific research. Experimental and theoretical studies in the field of acoustic flows and ultrasonic cavitation were successfully carried out, which allowed scientists to develop technological processes that occur when exposed to ultrasound in the liquid phase. It is a powerful method for studying a variety of phenomena in such a field of knowledge as physics. Ultrasound is used, for example, in semiconductor and solid state physics. Today, a separate area of \u200b\u200bchemistry is being formed, which is called "ultrasonic chemistry". Its application can speed up many chemical technological processes. Molecular acoustics was also born - a new branch of acoustics that studies molecular interaction with matter. New areas of ultrasound application have appeared: holography, introscopy, acoustoelectronics, ultrasonic phase measurement, and quantum acoustics.
In addition to experimental and theoretical work in this area, many practical ones have been performed today. Special and universal ultrasonic machines, installations that operate under increased static pressure, etc. have been developed. Ultrasonic automatic installations, included in production lines, have been introduced into production, which can significantly increase labor productivity.
More about ultrasound
Let's tell you more about what ultrasound is. We have already said that this elastic wave and ultrasound is more than 15-20 kHz. The subjective properties of our hearing determine the lower limit of ultrasonic frequencies, which separates it from the frequency of audible sound. This border, therefore, is conditional, and each of us defines in different ways what ultrasound is. The upper boundary is indicated by elastic waves, their physical nature. They propagate only in a material environment, that is, the wavelength should be significantly greater than the mean free path of molecules in the gas or the interatomic distances in solids and liquids. At normal pressure in gases, the upper limit of ultrasonic frequencies is 10 9 Hz, and in solids and liquids - 10 12 -10 13 Hz.
Sources of ultrasound
Ultrasound in nature is found both as a component of many natural noises (waterfall, wind, rain, pebbles rolled by the surf, as well as in the sounds accompanying thunderstorm discharges, etc.), and as an integral part of the animal world. Some species of animals use it for orientation in space, for detecting obstacles. It is also known that dolphins use ultrasound in nature (mainly frequencies from 80 to 100 kHz). The power of the location signals emitted by them can be very high. It is known that dolphins are able to detect those located at a distance of up to a kilometer from them.
Emitters (sources) of ultrasound are divided into 2 large groups. The first is generators in which oscillations are excited due to the presence of obstacles in them, installed in the path of a constant flow - a jet of liquid or gas. The second group, into which ultrasound sources can be combined, are electro-acoustic transducers, which convert specified oscillations of current or electrical voltage into mechanical oscillations performed solid bodyemitting acoustic waves into the environment.
Ultrasound receivers
On medium and ultrasound receivers, electro-acoustic transducers are most often of the piezoelectric type. They can reproduce the shape of the received acoustic signal, represented as the time dependence of the sound pressure. Devices can be either broadband or resonant, depending on what conditions they are intended for. Thermal receivers are used to obtain time-averaged sound field characteristics. They are thermistors or thermocouples coated with sound absorbing material. Sound pressure and intensity can also be estimated by optical methods such as diffraction of light by ultrasound.
Where is ultrasound used?
There are many areas of its application, using various features of ultrasound. These spheres can be roughly divided into three directions. The first of them is associated with the receipt of various information by means of ultrasound waves. The second direction is its active influence on the substance. And the third is related to signal transmission and processing. UZ of a certain is used in each case. We will only cover a few of the many areas in which it has found its application.
Cleaning with ultrasound
The quality of such cleaning cannot be compared with other methods. When rinsing parts, for example, up to 80% of contamination remains on their surface, about 55% - with vibration cleaning, about 20% - with manual cleaning, and with ultrasonic cleaning, no more than 0.5% of contamination remains. Parts that have a complex shape can only be cleaned well with ultrasound. An important advantage of its use is high productivity, as well as low costs of physical labor. What's more, you can replace expensive and flammable organic solvents with cheap and safe ones. aqueous solutions, use liquid freon, etc.
A serious problem is air pollution with soot, smoke, dust, metal oxides, etc. You can use the ultrasonic method of cleaning air and gas in gas outlets, regardless of the ambient humidity and temperature. If the ultrasound emitter is placed in a dust-settling chamber, its efficiency will increase hundreds of times. What is the essence of such cleaning? Dust particles randomly moving in the air hit each other more and more under the influence of ultrasonic vibrations. Moreover, their size increases due to the fact that they merge. Coagulation is the process of particle enlargement. Weighted and enlarged accumulations are captured by special filters.
Mechanical processing of fragile and superhard materials
If introduced between the workpiece and the working surface of the tool using ultrasound, the abrasive particles during the operation of the emitter will act on the surface of this part. In this case, the material is destroyed and removed, undergoing processing under the influence of a variety of directed micro-impacts. The kinematics of processing consists of the main movement - cutting, that is, the longitudinal vibrations performed by the tool, and the auxiliary - the feed movement that the apparatus carries out.
Ultrasound can do a variety of jobs. Longitudinal vibrations are the source of energy for abrasive grains. They destroy the processed material. The feed movement (auxiliary) can be circular, transverse and longitudinal. Ultrasound processing is highly accurate. Depending on what grain size the abrasive has, it ranges from 50 to 1 micron. Using tools of different shapes, you can make not only holes, but also complex cuts, curved axes, engrave, grind, make dies and even drill a diamond. Materials used as an abrasive are corundum, diamond, quartz sand, flint.
Ultrasound in radio electronics
Ultrasound in engineering is often used in the field of radio electronics. In this area, it is often necessary to delay an electrical signal relative to some other. Scientists have found a good solution by proposing to use ultrasonic delay lines (abbreviated as LZ). Their action is based on the fact that electrical impulses are converted into ultrasonic. How does this happen? The fact is that the speed of ultrasound is significantly less than that which is developed by electromagnetic oscillations. The voltage pulse after the reverse conversion into electrical mechanical vibrations will be delayed at the line output relative to the input pulse.
Piezoelectric and magnetostrictive transducers are used to convert electrical vibrations into mechanical ones and vice versa. LZ, respectively, are divided into piezoelectric and magnetostrictive.
Ultrasound in medicine
Various types of ultrasound are used to influence living organisms. In medical practice, its use is now very popular. It is based on the effects that occur in biological tissues when ultrasound passes through them. Waves cause vibrations of the particles of the medium, which creates a kind of tissue micromassage. And the absorption of ultrasound leads to their local heating. At the same time, certain physicochemical transformations take place in biological media. These phenomena in the case of moderate irreversible damage do not cause. They only improve the metabolism, and therefore contribute to the vital activity of the organism subject to them. Such phenomena are used in ultrasound therapy.
Ultrasound in surgery
Cavitation and strong heating at high intensities lead to tissue destruction. This effect is used today in surgery. Focal ultrasound is used for surgical operations, which allows for local destruction in the deepest structures (for example, the brain) without damaging the surrounding. In surgery, ultrasonic instruments are also used, in which the working end looks like a file, scalpel, needle. Vibrations applied to them give new qualities to these devices. The required effort is significantly reduced, therefore, the injury rate of the operation is reduced. In addition, an analgesic and hemostatic effect is manifested. Impact with a blunt instrument using ultrasound is used to destroy certain types of neoplasms that have appeared in the body.
The impact on biological tissues is carried out to destroy microorganisms and is used in the sterilization of medicines and medical instruments.
Examination of internal organs
Basically we are talking about the study of the abdominal cavity. For this purpose, a special one can be used to find and recognize various anomalies of tissues and anatomical structures. The task is often as follows: there is a suspicion of the presence of a malignant formation and it is required to distinguish it from a benign or infectious formation.
Ultrasound is useful in examining the liver and for solving other problems, which include detecting obstruction and diseases of the bile ducts, as well as examining the gallbladder to detect the presence of stones and other pathologies in it. In addition, studies of cirrhosis and other diffuse benign liver diseases can be used.
In the field of gynecology, mainly in the analysis of the ovaries and uterus, the use of ultrasound has long been the main direction in which it is carried out with particular success. Often, differentiation of benign and malignant formations is also needed here, which usually requires the best contrast and spatial resolution. Similar conclusions can be useful when examining many other internal organs.
The use of ultrasound in dentistry
Ultrasound has also found its way into dentistry, where it is used to remove tartar. It allows you to quickly, bloodlessly and painlessly remove plaque and stone. In this case, the oral mucosa is not injured, and the "pockets" of the cavity are disinfected. Instead of pain, the patient experiences a sensation of warmth.
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Introduction
1. Ultrasounds in nature
2. Echo finding
3. Types of natural sonars
4. Touch helps bats avoid obstacles
5. Fishing bats
6. And bats are wrong
7. Screams in the abyss
8. Water elephant radar
Conclusion
Literature
Introduction
The discovery of echolocation is associated with the name of the Italian naturalist Lazaro Spallanzani. He drew attention to the fact that bats fly freely in an absolutely dark room (where even owls are helpless), without touching objects. In his experience, he blinded several animals, however, even after that they flew on a par with the sighted. A colleague of Spallanzani J. Jurin conducted another experiment in which he plastered the ears of bats with wax - the animals stumbled upon all objects. From this, scientists concluded that bats are guided by hearing. However, this idea was ridiculed by contemporaries, since nothing more could be said - short ultrasonic signals at that time could not yet be recorded.
For the first time the idea of \u200b\u200bactive sound location in bats was expressed in 1912 by H. Maxim. He hypothesized that bats generate low-frequency echolocation signals by flapping their wings at a frequency of 15 Hz.
Ultrasound was guessed in 1920 by the Englishman H. Hartridge, who reproduced the experiments of Spallanzani. This was confirmed in 1938 thanks to the bioacoustics D. Griffin and the physicist G. Pearce. Griffin proposed the name echolocation (by analogy with radar) to refer to the way bats are oriented using ultrasound.
1. Ultrasounds in nature
Over the past ten to fifteen years, biophysicists have found with amazement that nature, apparently, was not very stingy when endowing its children with sonars. From bats to dolphins, from dolphins to fish, birds, rats, mice, monkeys, to guinea pigs, beetles, researchers moved with their instruments, detecting ultrasounds everywhere.
It turns out that many birds are armed with echo sounders. Tie plovers, curlews, owls and some songbirds, caught in flight by fog and darkness, scout the way with the help of sound waves. By shouting, they "feel" the ground and by the nature of the echo they learn about the flight altitude, the proximity of obstacles, and the terrain.
Obviously, for the purpose of echolocation, ultrasounds of a low frequency (twenty to eighty kilohertz) are emitted by other animals - guinea pigs, rats, marsupial flying squirrels and even some South American monkeys.
Mice and shrews in experimental laboratories sent swift-winged scouts - ultrasounds - ahead of them before setting off through the dark corners of the labyrinths in which their memory was tested. In complete darkness, they perfectly find holes in the ground. And here the echo sounder helps: from these holes the echo does not return!
Fat nightjars, or guajaro, as they are called in America, live in the caves of Peru, Venezuela, Guiana and the island of Trinidad. If you decide to pay them a visit, please be patient, and most importantly stairs and electric lamps. Some acquaintance with the basics of mountaineering is also necessary, because nightjars nest in the mountains and often, to get to them, you have to climb steep cliffs.
And as you enter the cave with all this equipment, plug your ears in time, because thousands of birds, awakened by the light, will fall from the cornices and walls and, with a deafening cry, will rush over your head. The birds are large, up to a meter in wingspan, chocolate brown with large white spots. Looking at their virtuoso maneuvers in the gloomy grottoes of Hades's kingdom, everyone is amazed and asks the same question: how do these feathered troglodytes, flying in complete darkness, manage not to bump into walls, all sorts of stalactites and stalagmites that support the vaults of the dungeons?
Turn off the lights and listen. Having flown a little, the birds will soon calm down, stop screaming, and then you will hear the soft flapping of the wings and, as an accompaniment to them, a soft click. Here is the answer to your question!
Of course, this is what echo sounders work. Our ear also picks up their signals, because they sound in the range of relatively low frequencies - about seven kilohertz. Each click lasts one or two thousandths of a second. Donald Griffin, already known to us as a bats sonar researcher, plugged some of the guajaro's ears with cotton wool and released them into the dark hall. And the virtuosos of night flights, having gone deaf, immediately "went blind": helplessly stumbled upon all the objects in the room. Hearing no echo, they could not navigate in the dark.
Guajaro spends daytime in caves. They also arrange their clay nests, sticking them somehow to the cornices of the walls. At night, the birds leave the dungeons and fly to where there are many fruit trees and palms with soft plum-like fruits. Oil palm plantations are attacking in thousands in flocks. The fruits are swallowed whole, and the bones are then regurgitated after returning to the caves. Therefore, in the dungeons where guajaro nest, there are always many young fruit "seedlings", which quickly, however, perish: they cannot grow without light.
The belly of newly fledged guajaro chicks is covered with a thick layer of fat. When the young troglodytes are about two weeks old, people come to the caves with torches and long poles. They destroy nests, kill thousands of rare birds and immediately, at the entrance to the caves, melt fat from them. Although this fat is good food quality, it is mainly used as fuel in lanterns and lamps.
It burns better than kerosene and cheaper than it - this is the opinion of the bird in the homeland, which by the evil irony of fate is condemned to spend its entire life in the dark, in order to dying to give light to a person's home.
In South Asia, from India to Australia, there is another bird that uses sonar to find its way to the nest in the dark. She also nests in caves (sometimes, however, on rocks in the open air). This is the famous swiftlet, well known to all local swift gourmets: soup is made from its nests.
This is how the salangana makes a nest: it clings with its paws to a rock and smears a stone with sticky saliva, drawing a silhouette of a cradle on it. He moves his head to the right and to the left - the saliva immediately freezes, turns into a brownish crust. And the salangana greases it from above. The walls of the nest grow, and you get a small cradle on a huge rock.
This cradle, they say, is very tasty. People climb high cliffs, climb the walls of caves by torchlight and collect swiftlet nests. Then they boil them in boiling water (or chicken broth!), And the result is an excellent soup, as connoisseurs assure.
Quite recently, it was discovered that swiftlets are of interest not only for gastronomes, but also for biophysicists: these birds, flying in the dark, also send acoustic scouts ahead, which "crackle like a children's clockwork toy."
2. Echo bearing
From a physical point of view, any sound is oscillatory motion that propagates in waves in an elastic medium.
The more vibrations per second an oscillating body (or elastic medium), the higher the frequency of sound. The lowest human voice (bass) has a vibration frequency of about eighty times per second, or, as physicists say, its frequency reaches eighty hertz. The highest voice (for example, the soprano of the Peruvian singer Yma Sumac) is about 1400 hertz.
In nature and technology, sounds of even higher frequencies are known - hundreds of thousands and even millions of hertz. Quartz has a record high sound - up to one billion hertz! The sound power of a quartz plate vibrating in a liquid is 40 thousand times greater than the sound power of an aircraft engine. But we cannot become deaf from this "hellish rumble" because we do not hear it. The human ear perceives sounds with a vibration frequency of only sixteen to twenty thousand hertz. More high-frequency acoustic vibrations are usually called ultrasounds, bats “feel” their surroundings as waves.
Ultrasounds originate in the bat's larynx. Here, in the form of peculiar strings, the vocal cords are stretched, which, vibrating, produce sound. The larynx, after all, by its structure resembles an ordinary whistle: the air exhaled from the lungs rushes through it in a vortex - a "whistle" of a very high frequency occurs, up to 150 thousand hertz (a person cannot hear it).
The bat can periodically block the flow of air. Then he bursts out with such force, as if thrown out by an explosion. The pressure of air rushing through the larynx is twice that of a steam boiler. Not a bad achievement for an animal weighing 5 - 20 grams!
In the larynx of a bat, short-term high-frequency sound vibrations are excited - ultrasonic impulses. Per second follows from 5 to 60, and in some species even from 10 to 200 impulses. Each impulse, "explosion", lasts only 2 - 5 thousandths of a second (in horseshoe bats 5 - 10 hundredths of a second).
The brevity of the audio signal is a very important physical factor. Only thanks to it, accurate echo location is possible, that is, orientation using ultrasounds.
From an obstacle that is seventeen meters away, the reflected sound returns to the animal in about 0.1 seconds. If the sound signal lasts more than 0.1 seconds, then its echo, reflected from objects located closer than seventeen meters, will be perceived by the animal's hearing organs simultaneously with the main sound.
But it is precisely by the time interval between the end of the sent signal and the first sounds of the returning echo that the bat instinctively gets an idea of \u200b\u200bthe distance to the object that reflected the ultrasound. This is why the sound pulse is so short.
The Soviet scientist E. Ya. Pumper made a very interesting assumption in 1946, which explains well the physiological nature of echo location. He believes that the bat emits each new sound immediately after it hears the echo of the previous signal. Thus, the impulses reflexively follow each other, and the echo perceived by the ear serves as the stimulus that causes them. The closer the bat flies to the obstacle, the faster the echo returns and, therefore, the more often the animal emits new echo sounding "cries". Finally, when approaching the obstacle directly, the sound impulses begin to follow each other with exceptional speed. This is a danger signal. The bat instinctively changes its course of flight, avoiding the direction from which the reflected sounds come too quickly.
Indeed, experiments have shown that bats emit only 5-10 ultrasonic pulses per second before launch. In flight, they are increased to 30. When approaching an obstacle, sound signals follow even faster - up to 50-60 times per second. Some bats, while hunting for nocturnal insects, overtake their prey, even emit 250 "cries" per second.
The bat sonar is a very accurate navigation "device": it is able to track even a microscopically small object - only 0.1 millimeter in diameter!
And only when the experimenters reduced the thickness of the wire stretched in the room where the bats fluttered to 0.07 millimeters, the animals began to bump into it.
Bats increase the rate of echo sounder signals about two meters from the wire. So, two meters away, they "grope" for her with their "shouts". But the bat does not immediately change direction, flies further directly to the obstacle and only a few centimeters away from it with a sharp flap of the wing deviates to the side.
With the help of sonars, which nature has endowed them, bats not only orient themselves in space, but also hunt for their daily bread: mosquitoes, moths and other nocturnal insects.
In some experiments, the animals were forced to catch mosquitoes in a small laboratory room. They were photographed, weighed - in a word, they kept track of how successfully they hunted. One bat weighing seven grams per hour caught a gram of insects. Another baby, who weighed only three and a half grams, swallowed mosquitoes so quickly that in a quarter of an hour she “got fat” by ten percent. Each mosquito weighs approximately 0.002 grams. That means 175 mosquitoes were caught in fifteen minutes of hunting - one mosquito every six seconds! Very fast pace. Griffin says that if it were not for sonar, then the bat, even flying all night with its mouth open, would have caught "by chance" a single mosquito, and then if there were many mosquitoes around.
3. Types of natural sonars
Until recently, it was thought that only small insectivorous bats like our bat and bat, and large flying foxes and dogs devouring tons of fruits in tropical forests, have natural sonars only. Perhaps this is so, but then, then, the rosettus is an exception, because flying dogs of this kind are endowed with sonars.
In flight, the rosettuses click their tongues all the time. Sound breaks out at the corners of the mouth, which are always ajar in the rosettus. The clicks are somewhat reminiscent of a kind of clatter of the tongue, which people sometimes resort to when condemning something. The primitive sonar of a flying dog works, however, quite accurately: it detects a millimeter wire from a distance of several meters.
Without exception, all small bats from the suborder Microchiroptera, that is, micro-bats, are endowed with echo sounders. But the models of these "devices" are different. Recently, researchers have distinguished mainly three types of natural sonars: whispering, chanting and chirping, or frequency modulating type.
Whispering bats live in the tropics of America. Many of them, like flying dogs, eat fruit. Insects are also caught, but not in the air, but on the leaves of plants. Their echo sounders are very short and very quiet clicks. Each sound lasts a thousandth of a second and is very weak. Only very sensitive devices can hear it. Sometimes, however, whisper bats "whisper" so loudly that a person hears them. But usually their sonar works at frequencies of 150 kilohertz.
The famous vampire is also a whisperer. Whispering "spells" unknown to us, he searches for exhausted travelers in the rotten forests of the Amazon and sucks their blood. They noticed that dogs are rarely bitten by vampires: a subtle ear warns them in advance about the approach of bloodsuckers. The dogs wake up and run away. After all, vampires attack only sleeping animals. Even such experiments were made. The dogs were trained: when they heard the "whisper" of a vampire, they immediately began to bark and wake people up. It is assumed that future expeditions to the American tropics will be accompanied by these trained "vampirolators".
The horseshoe bats are chanting. Some of them live in the south of our country - in the Crimea, the Caucasus and in Central Asia... Horseshoe bats are named for the growths on the muzzle, in the form of a leathery horseshoe with a double ring surrounding the nostrils and mouth. The growths are not idle decorations: they are a kind of horn that directs sound signals in a narrow beam in the direction where the bat is looking. Usually the animal hangs upside down and, turning (almost three hundred and sixty degrees!) First to the right, then to the left, feels the surroundings with the sound. The hip joints of tropical horseshoe bats are very flexible, so they can make their artistic turns. As soon as a mosquito or beetle enters the field of their locator, homing aircraft breaks down from a branch and sets off in pursuit of fuel, that is, for food.
And this "flying machine", it seems, is even able to determine, using the well-known Doppler effect to physicists, where the food is flying: whether it is approaching the bitch on which the horseshoe bush hangs or moving away from it. Pursuit tactics are changing accordingly.
Horseshoe bats are used for hunting very long (when compared with the "cries" of other bats) and monotonous sounds. Each signal lasts a tenth or twentieth of a second, and its frequency does not change - always equal to one hundred or one hundred twenty kilohertz.
But our regular bats and their North American cousins \u200b\u200becho the space with frequency modulated sounds, just like the best models of man-made sonar. The tone of the signal is constantly changing, so the pitch of the reflected sound also changes. This, in turn, means that at any given moment the pitch of the received echo does not match the tone of the sent signal. And it is clear to the layman that such a device greatly facilitates echo sounding.
4 . Feeling helps bats avoid obstacles
Scientists came to the solution of this interesting problem almost simultaneously in different countries.
Dutchman Sven Diygraaf decided to test whether the sense of touch really helps bats avoid obstacles. He cut the tactile nerves of the wings - the operated animals flew well. So the touch has nothing to do with it. Then the experimenter deprived the bats of hearing - they immediately went blind.
Diygraaf reasoned as follows: since the walls and objects encountered by bats in flight do not emit any sounds, it means that the mice themselves are screaming. The echo of their own voice, reflected from the surrounding objects, notifies the animals of an obstacle on the way.
Diygraaf noticed that the bat opened its mouth before taking flight. Obviously, it makes inaudible sounds for us, "feeling" their surroundings. In flight, bats also open their mouths every now and then (even when they are not hunting for insects).
This observation gave Diygraaf the idea to do the following experiment. He put a paper cap on the head of the animal. In front, like a visor at a knight's helmet, a small door in the cap opened and closed.
A bat with a closed door on the cap could not fly, bumped into objects. As soon as the visor was lifted in a paper helmet, the animal was transformed, its flight again became accurate and confident.
Diygraaf published his observations in 1940. And in 1946, the Soviet scientist Professor A.P. Kuzyakin began a series of experiments on bats. He covered their mouth and ears with plasticine and released them into the room with ropes stretched far and wide - almost all the animals could not fly. The experimenter established interesting fact: bats, first launched into a test flight with their eyes open, “repeatedly and with great strength, as the newly caught birds hit the glass of the uncurtained windows. " This happened during the day. In the evening, under the light of an electric lamp, the mice no longer bumped into the glass. This means that during the day, when it is clearly visible, bats trust their eyes more than other senses. But many researchers were inclined to ignore the vision of bats at all.
Professor A.P. Kuzyakin continued his experiments in the forest. On the heads of the animals - red noctresses - he put on caps made of black paper. The animals could now neither see nor use their acoustic radar. The bats did not dare to fly into the unknown. They opened their wings and descended on them, as with parachutes, to the ground. Only a few desperate ones flew at random. The result was sad: they hit the trees and fell to the ground. Then three holes were cut in the black caps: one for the mouth, two for the ears. The animals flew without fear. AP Kuzyakin came to the conclusion that the organs of sound orientation of bats "can almost completely replace vision, and the organs of touch do not play any role in orientation, and the animals do not use them in flight."
A few years earlier, American scientists D. Griffin and R. Galambos applied a different method to study the mysterious abilities of bats.
They started by simply bringing these animals to Pierce's apparatus - a device that could "hear" ultrasounds. And it immediately became clear that bats "make a lot of cries, but almost all of them fall into the range of frequencies that lie beyond the threshold of the human ear," Donald Griffin wrote later.
With the help of electrical equipment, Griffin and Galambos were able to discover and investigate the physical nature of the "cries" of bats. It was also established, by introducing special electrodes into the inner ear of the experimental animals, what frequency sounds are perceived by their hearing organs.
5 . Fishing bats
The little red bat begins its chirping with a sound with a frequency of about ninety kilohertz, and ends with a note of forty-five kilohertz. In two thousandths of a second, while its "cry" lasts, the signal runs along the frequency scale twice as long as the entire spectrum of sounds perceived by the human ear! There are about fifty sound waves in the "scream", but among them there are not two of the same length. There are ten or twenty such frequency-modulated "screams" every second. When approaching an obstacle or an escaping mosquito, the bat increases its signals. Now it chirps not 12, but 200 times per second.
Griffin writes: "In one of the handy types of eavesdropping equipment, every high-frequency squeak emitted by a bat will sound like a click on the phone." If you come with this device to the edge of the forest, where bats hunt for mosquitoes, then when one of them flies by, we will hear in the headphones a not very hasty tapping "putt-putt-putt-putt", "like from an old lazy gasoline engine ".
But then the bat set off in pursuit of a moth or decided to examine a pebble thrown up - immediately "pit-pit-pit-pit-bizzz" began to patter. Now "sounds follow each other, like the exhaust of a speeding motorcycle."
The moth felt a pursuit and was trying to save his life with deft maneuvers. But the bat is no less dexterous, writing bizarre pirouettes in the sky, overtakes him - and in the phone there are no longer fractional exhausts, but the monotonous buzzing of an electric saw.
Fishing bats have been discovered relatively recently. Their sonar is also a frequency modulation type. Four species of such mice have already been described. They live in tropical America. At dusk (and some even in the afternoon) they fly out to hunt and hunt all night. They flutter low over the water, suddenly put their paws into the water, snatch the fish out and immediately send it into the mouth. The legs of bats are long and their claws are sharp and crooked, like those of the osprey - their feathered competitor, only, of course, not so large.
Some fish-eating bats are called hare-lipped bats. The forked lower lip hangs down from them, and it is believed that through this channel a mouse fluttering over the sea directs its sounding sounds straight down into the water.
Having broken through the water column, "chirping" is reflected from the fish's swim bladder and its echo returns to the fisherman. Since the body of a fish is more than ninety percent water, it almost does not reflect underwater sounds. But a swim bladder filled with air is a screen that is rather "opaque" for sound.
When sound from air enters water and, conversely, from water to air, it loses more than 99.9 percent of its energy. This has long been known to physicists. Even if the sound hits the water surface at right angles, only 0.12 percent of its energy travels under the water. This means that the signals of a bat, having made a double trip across the air-water border, must lose so much energy due to the high tariffs that exist here that the sound power will become one and a half million times weaker!
In addition, there will be other losses: not all of the sound energy will be reflected from the fish, and not all, having made its way back into the air, will fall into the ears of the echo sounding animal.
After all this reasoning, it's hard to believe that air-water echolocation is not a myth, but a reality.
However, Donald Griffin calculated that the fisherman gets back from under the water only four times less powerful echo than a regular bat that sounders insects in the air. It's not that bad anymore. Moreover, if we assume that the sonars of bats detect insects not two meters away, as he assumed in his calculations, but already from two meters eighty centimeters (which is quite possible), then the intensity of the return signal will be the same for both - and for the angler , and the mosquito.
“Common sense,” concludes Griffin, “and first impressions can be misleading when we deal with issues that lie outside the realm of ordinary human experience, on which, after all, what we call common sense is built.”
6. And bats are wrong
Like humans, bats can be wrong too. And this often happens when they are tired or have not yet really woken up after a day spent in dark corners. This is proved by the mutilated corpses of bats crashing against the Empire Building and other skyscrapers every night.
If the wire is pulled low over the river, then the bats usually touch it when they descend to the water to quench their thirst with a few drops licked off on the fly. The animals hear two echoes at the same time: loud from the surface of the water and weak from the wire - and do not pay attention to the latter, which is why they break on the wire.
Bats, getting used to flying along long-tested tracks, choose their memory as a guide and then do not listen to sonar protests. The researchers carried out the same experiments with them as with the bees at the old airfield. (Remember?) They set up all sorts of obstacles on the well-trodden paths that bats used to hunt every night and return at dawn. The animals stumbled upon these obstacles, although their sonars worked and gave early warning signals to the pilots. But they believed their memory more than their ears. Bats often make mistakes because the insects they hunt are also not simpletons: many of them have acquired anti-sonars.
In the process of evolution, insects have developed a number of devices protecting against ultrasound. Many nocturnal moths, for example, are densely covered with fine hairs. The fact is that soft materials: down, cotton wool, wool - absorb ultrasound. This means that shaggy moths are more difficult to track. Some nocturnal insects have developed ultrasound-sensitive hearing organs that help them to know in advance about impending danger. Once within the range of the bat's echo sounder, they begin to rush from side to side, trying to get out of the danger zone. Moths and beetles tracked by a bat even use such a tactical technique: fold their wings and fall down, freezing motionless on the ground. In these insects, the hearing organs usually perceive sounds of two different ranges: low-frequency, on which their relatives "speak", and high-frequency, on which sonars of bats work. They are deaf to intermediate frequencies (between these two ranges).
7. Screams in the abyss
echolocation echo direction finding dolphin radar
On the afternoon of March 7, 1949, the research vessel Atlantic was listening to the sea one hundred and seventy miles north of Puerto Rico. There were great depths below the ship. Five kilometers of salt water filled a giant depression in the ground.
And from this abyss came loud screams. One scream, then his echo. Another scream, and another echo. Many shouts in a row with an interval of about one and a half seconds. Each one lasted about a third of a second, and its pitch was five hundred hertz.
It was immediately calculated that the unknown creature was practicing vocal solos at a depth of about three and a half kilometers. The echo of his voice was reflected from the seabed and therefore reached the ship's instruments with some delay.
Since whales do not dive that deep, and crayfish and crabs do not make such loud sounds, the biologists assumed that some fish were screaming in the abyss. And she screamed with a purpose: she probed the ocean with sound. Measured, quite simply, its depth. Studied the terrain, bottom topography.
This idea now seems incredible to few people. For it has already been established that fish, which have long been considered dumb, emit thousands of all kinds of sounds, striking their swim bladders with special muscles like a drum. Others grind their teeth, snap the knuckles of their armor. Many of these crackles, creaks and squeaks sound in the ultra-short range and are used, apparently, for echolocation and orientation in space. So, like bats, fish have their own sonars.
Fish sonars have not yet been studied, but they are well researched in dolphins. Dolphins are very talkative. They won't be silent for a minute. Most of their shouts are colloquial, so to speak, lexicon, but we are not interested in it now. Others clearly serve sonar.
The bottlenose dolphin whistles, clicks, grunts, barks, squeals at different voices in the frequency range from one hundred and fifty to one hundred and fifty-five thousand hertz. But when he swims “silently”, his sonar constantly feels the surroundings with a “rain” of rapid screams, or, they say, klaks. They last no more than a few milliseconds and are usually repeated fifteen to twenty times a second. And sometimes hundreds of times!
The slightest splash on the surface - and the dolphin immediately increases its cries, "feeling" with them a submerging object. The dolphin's sonar is so sensitive that even a small pellet, carefully lowered into the water, will not escape its attention. Fish thrown into the pond is immediately detected. The dolphin sets off in pursuit. Not seeing prey in the muddy water, it unmistakably pursues it. Following the fish, it accurately changes course. Listening to the echo of its voice, the dolphin slightly tilts its head in one direction or the other, like a person trying to more accurately establish the direction of the sound.
If several dozen vertical rods are lowered into a small pool, the dolphin quickly swims between them without touching them. However, he, apparently, cannot detect coarse-mesh networks with his sonar. Fine-meshed "gropes" easily.
The point here, apparently, is that the large cells are too "transparent" for sound, while the small ones reflect it, almost like a solid barrier.
William Sheville and Barbara Lawrence-Sheville, researchers at the Woodshole Oceanographic Institute, have shown in a series of interesting experiments how delicate the dolphin's acoustic “touch” is.
The dolphin swam in a small cove fenced off from the sea and "creaked" all the time. And sometimes the device rattled wildly from too fast, pattering claps. This happened when pieces of fish were thrown into the water. Not just thrown, but quietly, without any splash, laid to the bottom. But it was difficult to hide from the dolphin the quietest throwing of food into the pond, even if he swam at its other end twenty meters from the place of sabotage. And the water in this puddle was so cloudy that when a metal plate was immersed in it for half a meter, it seemed to dissolve: even the keenest human eye could not see it.
The experimenters lowered small fish about fifteen centimeters long into the water. The dolphin instantly spotted the fish with the sonar, although it was barely submerged: the man was holding her by the tail.
It is believed that the clacks serve the dolphin for close orientation. General reconnaissance of the area and the feeling of more distant objects are produced by whistling. And this whistle is frequency modulated! But unlike the same type of bat sonar, it starts with lower notes and ends with high notes.
Other whales - sperm whales, fin whales, and beluga whales - also appear to be guided by ultrasound. They just don't know yet how they make these sounds. Some researchers think that it is the blowhole, that is, the nostrils and air sacs of the respiratory canal, others - that the throat. Although whales do not have real vocal cords, they can be successfully replaced by - as some believe - special growths on the inner walls of the larynx.
Or maybe both the blowhole and the larynx serve the sonar transmission system in equal measure.
8. Water elephant radar
Among the many sacred animals Ancient egypt there was one fish with completely unique abilities.
This fish is mormyrus, or water elephant. Her jaws are extended into a small proboscis. The Mormir's inexplicable ability to see the invisible seemed like a supernatural miracle. The invention of the radar helped solve the mystery.
It turns out that nature has endowed the water elephant with the most amazing organ - the radar!
Many fish are known to have electrical organs. Mormyrus also has a small "pocket battery" in its tail. The voltage it generates is small - only six volts, but that's enough.
Every minute the Mormyrus radar sends eighty to one hundred electrical impulses into space. The electromagnetic oscillations arising from the discharges of the "battery" are partially reflected from the surrounding objects and in the form of a radio echo again return to the mormir. The "receiver" that catches the echo is located at the base of the dorsal fin of this amazing fish. Mormirus "probes" the surroundings using radio waves!
The report on the unusual properties of mormyrus was made in 1953 by the East African Ichthyological Institute. The institute noted that the mormiruses kept in the aquarium began to rush restlessly when an object with a high electrical conductivity, such as a piece of wire, was lowered into the water. It looks like Mormyrus has the ability to sense change. electromagnetic fieldexcited by his electrical organ? Anatomists examined the fish. Paired branches of large nerves passed along her back from the brain to the base of the dorsal fin, where, branching into small branches, they ended in tissue formations at equal intervals from each other. Apparently, an organ is placed here that catches the reflected radio waves. Mormyrus, with the severed nerves serving this organ, lost sensitivity to electromagnetic radiation.
Mormyrus lives on the bottom of rivers and lakes and feeds on insect larvae, which it extracts from the silt with long jaws, like tweezers. While searching for food, the fish is usually surrounded by a thick cloud of agitated silt and sees nothing around. Ship captains know from their own experience how irreplaceable a radar is in such conditions.
Mormyrus is not the only "living radar" in the world. A remarkable radio eye was also found in the tail of an electric eel in South America, the "batteries" of which develop a record voltage - up to five hundred volts, and according to some sources, up to eight hundred volts!
American researcher Christopher Coates, after a series of experiments carried out in the New York Aquarium, came to the conclusion that the small warts on the head of an electric eel are radar antennas. They catch electromagnetic waves reflected from surrounding objects, the emitter of which is located at the end of the eel's tail. The sensitivity of the radar system of this fish is such that the eel, obviously, can establish what nature the object was in the field of the locator. If it is an edible animal, the electric eel immediately turns its head in its direction. Then it activates the powerful electrical organs of the front part of the body - throws at the victim of "lightning" - and slowly devours the prey killed by the electric discharge.
In the same rivers, where electric eels doze lazily at the bottom, elegant knife-fish - eigenmania - scurry about in the thickets. They look strange: there are no dorsal fins and no tail fins either (only a bare thin spire on the tail). And these fish behave unusually: they twirl this very spire in all directions, as if sniffing their tail. And before crawling under a snag or into a cave at the bottom, they first stick their tail into the gap, and then, if the examination gives positive, so to speak, results, they themselves get there. But they climb not head first, but tail. It looks like the fish trust him more than their eyes.
Everything was explained very simply: at the very end of the filamentous tail of Aigenmania, scientists discovered an electric “eye”, like that of a Mormyrus.
Gymnotids, very similar to the Aigenmania of tropical American fish, appear to have radars too, although this has not yet been proven.
Recently, Dr. Lissman of Cambridge has again become interested in the long-studied electric catfish that lives in the rivers of Africa. This fish, capable of developing a voltage of up to two hundred volts, hunts at night. But she has very "myopic" eyes, and in the dark she sees poorly. How then does catfish find prey? Dr. Lissman proved that, like an electric eel, the electric catfish also uses its powerful batteries as a radar.
Conclusion
From the above, we can conclude that nature, apparently, was not very stingy when endowing its children with sonars. From bats to dolphins, from dolphins to fish, birds, rats, mice, monkeys, to guinea pigs, beetles, researchers moved with their devices, detecting ultrasounds everywhere. Animals use echolocation for orientation in space and to determine the location of objects around them, mainly using high-frequency sound signals. It is most developed in bats and dolphins, it is also used by shrews, a number of pinnipeds (seals), birds (guajaro, swiftlets, etc.).
The origin of echolocation in animals remains unclear; it probably arose as a substitute for vision for those who live in the darkness of caves or the depths of the ocean. Instead of a light wave, sound was used for location.
This method of orientation in space allows animals to detect objects, recognize them and even hunt in conditions of complete absence of light, in caves and at considerable depths.
Ultrasound - sound waves with a frequency above 20 thousand Hertz v, Hz Infrasound Sound Ultrasound Hypersound
Ultrasound is used by many animals to communicate with each other using echolocation: dogs, dolphins, whales, bats, some species of insects and birds. Ultrasound is used by many animals to communicate with each other using echolocation: dogs, dolphins, whales, bats, some species of insects and birds.
Bats using echolocation for navigation at night emit signals of extremely high intensity through their mouth or nose. Sound waves are reflected from surrounding objects, outlining their contours, and bats catch them with their ears and perceive the sound picture of the surrounding world. Bats using echolocation for navigation at night emit signals of extremely high intensity through their mouth or nose. Sound waves are reflected from surrounding objects, outlining their contours, and bats catch them with their ears and perceive the sound picture of the surrounding world.
Moths from the bear family have developed an ultrasonic noise generator that "knocks off the trail" of bats pursuing these insects. Moths from the bear family have developed an ultrasonic noise generator that "knocks off the trail" of bats pursuing these insects.
Dolphins excel in the art of echolocation. The sophisticated brains of these animals are able to accurately analyze the data obtained by echolocation and present them in three dimensions. Interestingly, dolphins not only “see” space and objects in space with the help of ultrasound, but are also able to determine the weight of objects or animals, their size and other important characteristics. Dolphins excel in the art of echolocation. The complex brains of these animals are able to accurately analyze the data obtained by echolocation and present them in three-dimensional form. It is interesting that dolphins not only "see" space and objects in space with the help of ultrasound, but are also able to determine the weight of objects or animals, their size and other important characteristics.
We perceive vibrations of frequent from 20 to 20,000 Hz, as sound. But sound is not only limited to the frequency range that the human ear perceives. In the zone with frequencies below the audible ones, there is a clap of infrasound, and above - ultrasound.
Definition 1
Ultrasound - elastic vibrations of the medium, waves lying in the range above the audible region of sounds (from 20,000 Hz).
Definition 2
Infrasound - sound waves with a frequency lower than the threshold of perception by the human ear (below 20 Hz).
Here is the entire spectrum of elastic waves in physics:
Ultrasound and infrasound in nature
In nature, ultrasound and infrasound are as widespread as audible sound.
For example, ultrasound is a component of the spectrum of many natural sounds: the noise of a waterfall, thunder. Ultrasound decays quickly in air, but spreads well in liquid media. Another example is bats and some rodents, which use ultrasound to hunt and navigate in the dark. Whales and dolphins also generate ultrasonic signals for various purposes: hunting, orientation in troubled waters.
Natural sources of infrasound include earthquakes, hurricanes, lightning strikes. Many animals feel the influence of infrasound and, registering the growing infrasonic noise, go into the shelter, since infrasound is a harbinger of a storm or storm. Infrasonic signals in wildlife are also used by some animals for communication: whales, elephants. Infrasound propagates over long distances in all environments and is not easily absorbed.
Application of ultrasound and infrasound
Ultrasound has been known to people for a long time, but only relatively recently it is actively used in medicine, production and scientific research.
Sources of obtaining ultrasound are divided into natural and man-made. Among the methods of obtaining ultrasound:
- Mechanical - strings, pipes, elastic plates.
- Thermal - impulse current and electrical discharges in liquids and gases with a constant rise in temperature.
- Otpichny - laser.
Infrasound finds less practical application and has negative consequences from effects on the body. At high levels of infrasound, excessive fatigue, drowsiness, aggression, and a feeling of pressure in the ears may occur. The impact of infrasound on a person is especially harmful if the intensity of infrasound is high. At a level of 180-190 dB, the action of infrasound is fatal. Nevertheless, the sensitivity of each person to infrasound is individual, and the usual levels of infrasound in everyday life can not cause serious harm to health.
Example
The bat emits ultrasound with a frequency of ϑ \u003d 45 kHz and flies perpendicular to the wall at a speed of v \u003d 6 m / s. What is the frequency of the reflected ultrasound that the mouse will hear? The speed of sound in air is taken equal to c \u003d 340 m / s.
According to the Doppler effect, the frequency of the reflected sound is determined by the ratio:
ϑ 1 \u003d c + v c - v ϑ \u003d 340 + 6 340 - 6 45 10 3 \u003d 46.6 kHz.
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Zolkina Alexandra.
This project was completed by a 9th grade student. This project looks at ultrasound in nature. The concept of ultrasound, its location on the scale of electromagnetic waves is given. The work is carried out at the level of the 9th grade of secondary school.
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Ultrasound is elastic vibrations and waves, the frequency of which exceeds 15 - 20 kHz
In nature, ultrasound is found as a component of many natural noises: wind, waterfall, rain, and lightning discharges. The locating abilities of bats, nocturnal insects and marine animals are well known to all. The existence of such sounds was discovered with the development of acoustics in the late 19th century. From a physical point of view, any sound is oscillatory motion that propagates in waves in an elastic medium. The more vibrations per second an oscillating body (or elastic medium), the higher the frequency of sound. The lowest human voice (bass) has a vibration frequency of about eighty times per second, or, as physicists say, its frequency reaches eighty hertz. The highest voice (for example, the soprano of the Peruvian singer Yma Sumac) is about 1400 hertz.
In sailing and fishing, the Sounder is mounted in the bottom of a ship or boat and ensures the safety of sailors, ships and passengers. Only when using the echo sounder can the ship sail safely. After all, the bottom becomes "visible".
Modern echo sounders allow not only to measure the depth, but to search for fish, find out the size of the fish, the distance to the fish and the depth of the school or individual. For example, a modern echo sounder HUMMINBIRD 580.
In nature and technology, sounds of even higher frequencies are known - hundreds of thousands and even millions of hertz. Quartz has a record high sound - up to one billion hertz! The sound power of a quartz plate vibrating in a liquid is 40 thousand times greater than the sound power of an aircraft engine. But we cannot become deaf from this "hellish rumble" because we do not hear it. The human ear perceives sounds with a vibration frequency of only sixteen to twenty thousand hertz. More high-frequency acoustic vibrations are usually called ultrasounds; bats “feel” their surroundings as waves.
Dolphins A dolphin uses ultrasonic waves to focus them in the desired direction, thanks to the convex shape of the skull and the fatty layer in the form of an outgrowth on the head. The echo returns to the dolphin in the form of a sound image, by which he can recognize the prey in front of him or the predator
Bats The expression "blind as a bat" is quite true - scientists have found that when these animals rely only on sight, they bump into surrounding objects much more often than when using ultrasound for navigation.
Ultrasounds originate in the bat's larynx. Here, in the form of peculiar strings, the vocal cords are stretched, which, vibrating, produce sound. The larynx, after all, by its structure resembles an ordinary whistle: the air exhaled from the lungs rushes through it in a vortex - a "whistle" of a very high frequency occurs, up to 150 thousand hertz (a person cannot hear it).
The bat can periodically block the flow of air. Then it bursts out with such force, as if thrown out by an explosion. The pressure of air rushing through the larynx is twice that of a steam boiler. Not a bad achievement for an animal weighing 5 - 20 grams! In the larynx of a bat, short-term high-frequency sound vibrations are excited - ultrasonic impulses. Per second follows from 5 to 60, and in some species even from 10 to 200 impulses. Each impulse, "explosion", lasts only 2 - 5 thousandths. The brevity of the audio signal is a very important physical factor. Only thanks to it, accurate echo location is possible, that is, orientation using ultrasounds.
Moths from the bear family have developed an ultrasonic noise generator that "knocks off the trail" of bats pursuing these insects. Butterflies
Ultrasonic echolocation of moths
Depth of penetration of ultrasonic waves The depth of penetration of ultrasound is understood as the depth at which the intensity is reduced by half. This value is inversely proportional to absorption: the stronger the medium absorbs ultrasound, the smaller the distance at which the ultrasound intensity is attenuated by half.
Work performed by: Alexandra Zolkina, student of grade 9 A