Animal echolocation presentation. Echolocation in humans, animals and technology. Sound reflection. Echo
"Ultrasound physics" - Application of infrasound. The study of animal behavior. Historical use of infrasound. Earthquake prediction. Bat. Not perceived by the human ear. Medicine. Ultrasonic waves affect the solubility of a substance and, in general, the course of chemical reactions. Large doses - a sound level of 120 dB or more give a striking effect.
"Using ultrasound" - Experience 4. Ultrasound creates wind. 1. Operations on the brain without opening the skull. Field of study: acoustics. Areas of application of ultrasound. Experiment 8. Ultrasound degasses a liquid. This phenomenon can be used to purify chlorinated water. Experience 1. Ultrasound reduces friction on an oscillating surface.
"Impact of ultrasound" - Endocrine system. Mechanical vibrations. General tonic action. Spasmolytic action. Cardiovascular system. Pain-relieving action. Historical use of infrasound. Anti-inflammatory action. Nervous system. Plankton. Ultrasound in small doses has a positive effect on the human body.
"Ultrasonic sensor" - Hertz (Hz, Hz) - frequency unit, corresponds to one cycle per second. Movements: Sliding Rotation Wiggle Pressure. Physical bases of ultrasound. What is ultrasound? Sound reflection. Interaction of waves. Radiation frequency. The strength (amplitude) of each reflected wave corresponds to the brightness of the displayed point.
"Ultrasound in Medicine" - Ultrasound. The birth of ultrasound. Ultrasound to help pharmacologists. Ultrasound treatment. Ultrasound in medicine. Is ultrasound harmful? Ultrasonic procedures. Children's encyclopedia. Is ultrasound treatment harmful? Plan.
"Ultrasound" - Using the ultrasound Doppler effect, they study the nature of the movement of the heart valves and measure the speed of blood flow. Ultrasonic peeling of facial skin. Spectral Doppler of the Common Carotid Artery. Bischofite-gel is applied and the working surface of the emitter is used for micro-massage of the affected area. In addition to being widely used for diagnostic purposes, ultrasound is used in medicine as a therapeutic agent.
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Contents Who are they? Family Dolphins are excellent swimmers Echolocation Social life Preparing for childbirth Chatterboxes and naughty people Representatives
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What are they? Dolphins are aquatic mammals, the dolphin family of the suborder of toothed whales; includes about 20 genera, about 50 species: sotalia, stenella, common dolphins, whale dolphins, short-headed dolphins, beak-headed dolphins, bottlenose dolphins (two species), gray dolphins, black killer whales, pilot whales, killer whales, porpoises, white-winged porpoises, featherless porpoises , comb-toothed dolphins (Steno bredanensis). Some can be found in any ocean. Many consider them intelligent beings seeking to communicate with humans.
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The length of dolphins is 1.2-10 m. Most have a dorsal fin, the muzzle is extended into a “beak”, and there are numerous teeth (more than 70). Dolphins are often kept in dolphinariums where they can breed. Dolphins have very large brains. They have a memory and an amazing ability to imitate and adapt. They are easy to train; capable of sound reproduction. The hydrodynamic perfection of body shapes, the structure of the skin, the hydroelastic effect of the fins, the ability to dive to a considerable depth, the reliability of the sonar, and other features of dolphins are of interest to bionics. One species of dolphins is listed in the International Red Book.
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Dolphin family DOLPHIN (dolphins; Delphinidae) - a family of marine mammals of the suborder of toothed whales; includes two subfamilies: narwhals (beluga and narwhal) and dolphins, which are sometimes considered as separate families. Often among the dolphins, a subfamily of porpoises is distinguished. The family includes small (1-10 m), predominantly mobile marine cetaceans of a slender build.
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Dolphins are excellent swimmers. Their speed of movement can reach 55 km/h. Sometimes they use the waves from the bow of the ship to move even faster and use less energy. At the top of the head, dolphins have a nostril, called a blowhole, through which they ventilate their lungs. Dolphins' eyes see just as well on the surface as they see underwater. A thick layer of fat is located under the skin, protects them from cold and heat, and also serves as a store of nutrients and energy. The pad of fat covering the top of the dolphin's head gives these animals a permanent smile. The skin of dolphins is extremely soft and elastic. It dampens the turbulence of the water around when moving and allows you to swim faster.
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Echolocation Dolphins have a natural resemblance to ultrasonic radar or sonar. It is located in their head and makes it easy to detect prey, obstacles and dangers, accurately determining the distance to them. This radar also serves as a compass. When it "goes wrong", dolphins can be washed ashore. Dolphins have tiny ears, but they pick up most of the sounds with the lower jaw, along the nerves of which these signals are transmitted to the brain.
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Social life Dolphins live in groups. The smallest herds number 6-20 individuals, the largest - more than 1000. The leader of the group, the oldest dolphin, leads the herd with the help of several males, whom he sends ahead as scouts. Dolphins always help each other and rush to the rescue as soon as one of them is in trouble. They usually elude killer whales trying to surround them and attack sharks that pose a danger to them.
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Preparing for childbirth Pregnancy of the female lasts 10-16 months, depending on the type of dolphin. Before giving birth, she swims away from the group, accompanied by an older female (“godmother”), who will help her during childbirth and look after the baby while the mother gets food. The baby is born tail first. To become an adult, he will need from 5 to 15 years
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Chatterboxes and naughty Dolphins are excellent acrobats. They communicate with each other by jumping, as well as the language of whistling, clicking and squeaking. Each dolphin has an individual voice, and each group has its own language.
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River dolphins A family of aquatic mammals of the suborder of toothed whales; includes 5–6 species living in the rivers of South Asia and South America, as well as in the Atlantic Ocean off the coast of South America. This is the oldest family of the suborder, which arose in the Miocene. The length of river dolphins is up to 3 m. The pectoral fins are short and wide, instead of the dorsal fin there is a low elongated crest. River dolphins feed on fish, shellfish and worms. In the rivers of South America, there is an Amazonian inia. The Gangetic dolphin is common in the rivers of India and Pakistan - the Ganges, the Brahmaputra and the Indus. The Indian dolphin (Platanista Indi) is close to it.
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BEAKED DOLPHINS (variegated dolphins, Serhalorhynchus) - a genus of marine animals of the dolphin subfamily; small (120-180 cm long) variegated animals of the temperate waters of the Southern Hemisphere. The beak is not pronounced, as it imperceptibly passes into the head. Mouth small, dorsal fin rounded or slightly pointed at apex. The color of the body is combined from white and dark tones; all fins are black. Teeth small, conical, 25-31 in each row. There are at least four species in the genus.
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SHORT-HEADED DOLPHINS A genus of marine animals of the dolphin subfamily; unites animals, the size of which is not more than 3 m. Their head is shortened, the beak is short, barely delimited from the fronto-nasal pillow. The large dorsal fin on the posterior margin is crescent-shaped, so deep that its apex points straight back. Pectoral fins of moderate size. The upper and lower edges of the caudal peduncle are high, in the form of ridges. The coloration of most species is bright, of contrasting black and white tones. A dark stripe runs from the base of the pectoral fin to the eye. Teeth numerous, 22-40 pairs above and below, 3-7 mm thick. The palate is flat. Short-headed dolphins are characterized by an increased number of vertebrae. The genus unites six species living in the temperate and warm temperate waters of the World Ocean; some of them go to the outskirts of the Antarctic and the Arctic.
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WHALE DOLPHINS A genus of marine animals of the dolphin subfamily; they are distinguished by a thin and slender body 185-240 cm long without a dorsal fin, a moderately long pointed beak, which is smoothly demarcated from a low, sloping frontal fat pad. The pectoral fins are crescent-shaped, small, convex along the lower edge, concave along the upper edge. The tail stalk is thin and low. The teeth are small, about 3 mm thick, 42-47 pairs at the top and 44-49 pairs at the bottom. The sky is flat, without grooves. There are two rare species in the genus - the northern right whale dolphin and the southern right whale dolphin.
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ATLANTIC WHITE-SIDED DOLPHIN Species of a marine animal of the genus of short-headed dolphins; body length 2.3-2.7 m. The entire upper body of this dolphin is black, the bottom from the chin to the end of the tail is white. The pectoral fins, like the dorsal, are black, attached to the light part of the body, and a black strap runs from them to the eye. An elongated white field stands out on the sides in the posterior half of the body. From above it borders on black, below - on gray. Teeth 30-40 pairs at the top and bottom, up to 4 mm thick.
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BELLOWBONK A genus of marine mammals of the dolphin family; includes two types. Length up to 2.6 m, males are slightly larger than females. The back and fins are dark, the sides are gray with white patches; long beak. Dolphins are common in warm and temperate waters, including the Black Sea; unlike the bottlenose dolphin, it prefers the open sea. Several subspecies live within Russia: the Black Sea (the smallest), the Atlantic and the Far East. Dolphins feed on schooling fish (hamsa, haddock, red mullet, herring, capelin, sardine, anchovy, hake) and cephalopods. The Black Sea subspecies feeds at a depth of up to 70 m, but the oceanic subspecies dive to a depth of 250 m.
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bottlenose dolphin Marine mammal of the dolphin family. Body length up to 3.6-3.9 m, weighs 280-400 kg. A moderately developed beak is clearly demarcated from a convex fronto-nasal pad, the color of the body is dark brown above, light (from gray to white) below; the pattern on the sides of the body is not constant, often not at all pronounced. Teeth strong, conically pointed. The bottlenose dolphin is widely distributed in temperate and warm waters, including the Black, Baltic and Far Eastern seas. There are four subspecies in the oceans: Black Sea, Atlantic, North Pacific, Indian (which is sometimes distinguished as an independent species). The bottlenose dolphin can reach speeds of up to 40 km/h and jump out of the water to a height of up to 5 m.
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Grinds Genus of marine mammals of the dolphin subfamily; includes three types. The length of pilot whales is up to 6.5 m, weight is up to 2 tons. They are distinguished by a spherically rounded head, almost devoid of a beak. Narrow and long pectoral fins set low. The dorsal fin is bent back and shifted to the anterior half of the body. Pilot whales are widely distributed (excluding the polar seas), they are an object of fishing in the northern part of the Atlantic Ocean. The most studied is the common pilot whale. She is almost all black, on her belly there is a white pattern in the form of an anchor. She has a highly developed herd instinct and the instinct to preserve the species. It is capable of speeds up to 40 km/h.
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Killer Whale The only species of the eponymous genus of marine mammals of the dolphin subfamily. Length up to 10 m, weight up to 8 tons. The head is moderate in size, wide, slightly flattened from above, equipped with powerful chewing muscles. The fronto-nasal pillow is low, the beak is not pronounced. All fins are greatly enlarged, especially the dorsal (up to 1.7 m in old males). The teeth are massive, 10-13 pairs at the top and bottom. The body is black above and on the sides, with an oval spot above each eye, and a light saddle behind the dorsal fin (females do not). The white color of the throat on the belly turns into a stripe. A variety of sound signals: from high tones to groans and screams play an important communication role: they warn of danger, call for help, etc. They can move at speeds up to 55 km / h.
Checking homework.
1. What vibrations are called ultrasonic?
A) mechanical vibrations, the frequencies of which are higher 20000 Hz;
b) mechanical vibrations with a frequency above 16 Hz;
c) mechanical vibrations, the frequencies of which lie in the range from 16 to 20,000 Hz.
2. Can sound waves propagate in vacuum?
a) can, for example, the sound of a shot in a vacuum;
b) cannot: sound waves propagate only in matter;
c) they can, if the sound waves are transverse.
3. What quantities does the pitch depend on?
a) on the amplitude;
b) on frequency;
c) from loudness;
d) on the speed of sound propagation.
4. How does sound propagate in a homogeneous medium?
a) sound travels in a straight line at a constant speed in one direction;
b) sound propagates in all directions, the speed decreases with distance;
V) Sound travels in a straight line and at a constant speed in all directions.
5. What determines the speed of sound in air? a) from the volume of the sound;
b) on the pitch of the sound;
c) on temperature;
d) on the speed of the sound source.
6. What determines the pitch of the sound?
a) on the amplitude of oscillations;
b) on the wavelength;
c) on the vibration frequency of the sound source.
7. What is infrasound?
a) fluctuations below 16 Hz;
b) fluctuations above 16 Hz;
c) fluctuations above 20,000 Hz.
8. Transverse elastic waves are possible: a) only in solids;
b) only in gases;
c) in gases, solids and liquids.
lesson topic:"Reflection of sound. Echo".
Without a body - but it lives, Without a language - screams!.......
Echoes are sound waves reflected from an obstacle and returning to their source.
The name "echo" is associated with the name of the mountain nymph Echo
The ancient Greeks came up with a very beautiful legend to explain the echo. Long ago, there lived a beautiful nymph named Echo. She had only one drawback - she talked too much. As punishment, the goddess Hera forbade her to speak unless spoken to. The nymph could only repeat what she was told. One day, Echo saw a handsome young Narcissus and immediately fell in love with him. However, Narcissus did not notice her. The nymph was seized with such sadness that Echo vanished into thin air, leaving only her voice. And we hear her voice, which repeats everything we say.
echo formation
The echo is formed as a result of the reflection of sound from various obstacles - the walls of a large empty room, a forest, the vaults of a high arch in a building. We hear an echo only when the reflected sound is perceived separately from the spoken one. To do this, it is necessary that the time interval between the impact of these two sounds on the ear eardrum be at least 0.06 s.
Echo in the mountains
The most amazing echo "lives" in the mountains. There it is repeated many times, as a result of repeated reflection of sound.
What is an echo like?
Echo is of several types:
- once e is the wave reflected from the obstacle and received by the observer.
2) Multiple - this is an echo that occurs at some loud sound, which gives rise to not one, but several successive sound responses.
cons of echo
The big disadvantage of echo is that it is a significant hindrance to audio recording. Therefore, the walls of the rooms in which songs are recorded, radio reports are usually equipped with sound-damping screens made of soft or ribbed materials that absorb sound.
Styrofoam
echo application
Since sound waves in air have a constant propagation speed (about 340 meters per second), the time it takes for the sound to return can serve as a source of data on the removal of an object.
1. Acoustic echo is used in sonar, as well as in navigation, where echo sounders are used to measure the depth of the bottom.
2) ultrasonic flaw detection (detection of defects, cavities, cracks in cast metal products),
3) echo research in medicine
Famous echoes of the world
At Woodstock Castle 17 syllables(destroyed during the Civil War).
Ruins Derenburg Castle near Halberstadt gave 27-difficult an echo that, however, has been silenced since one wall was blown up.
rocks spread out in a circle near Adersbach in Czechoslovakia, repeat, in a certain place, triple 7 syllables; but a few steps from this point, even the sound of a gunshot does not give any echo.
A very multiple echo was observed in one (now defunct) castle near Milan : shot, produced from the window of the wing, echoed 40 - 50 times, A big word - times 30 .
At Woodstock Castle in England the echo distinctly repeated 17 syllables(destroyed during the Civil
Sound reflection. Echo.
MOU secondary school No. 66, Magnitogorsk
Shcherbakova Yu.V.
Physics teacher
Repetition, checking homework.
1. What are oscillations? Which
Do you know the types of oscillations?
2. What are the magnitudes of fluctuations?
3. What are called waves? What types of waves do you know?
4. In what medium can longitudinal and transverse waves propagate and why?
5. What is the formula for calculating wavelength?
6. Give examples of natural
sound sources and artificial.
What is the common property
all sound sources?
7. Fluctuations of what range are called sound? ultrasonic? infrasonic?
- 8. Swing sound
flying wings
we hear a mosquito
but flying
birds are not. Why?
10. Tell us about the experience shown in the picture. What conclusion can be drawn from this experience?
Why do we not hear the roar of powerful processes occurring on the Sun?
9. Tell us about measuring the depth of the sea using echolocation.
Subject:
"Reflection of sound. Echo."
Anchoring
1. At what distance is the obstacle from the person if the sound signal sent by him was received after 3 seconds? The speed of sound in air is 340m/s.
2. The thickness of the steel plate is 4 cm. The product is examined using an ultrasonic flaw detector. The reflected signal arrived at one place after 16 μs. And in another place - after 12 microseconds. Is there a defect in the plate? If yes, what size is it?
1. The sound must travel twice the distance - to the obstacle and back
Answer: 510 m
2. The difference in signal transit time can be used to judge the presence of a defect. The signal must travel twice the distance to the end of the plate or defect and back.
S 1 =V*t 1 /2 S 2 =V*t 2 /2 S=S 1 -S 2
Answer: 1 cm
Questions:
1. What causes an echo?
2. Why doesn't echo occur in a small room full of furniture?
3. How can the sound properties of a large hall be improved?
4. Why does sound travel a greater distance when using a horn?
1. Introduction ____________________________________________ 3-4 pp.
2. Sound reflection. Echo.____________________________ 4-5pp.
3. Types of echo _______________________________________ pp. 5-7
4. How to search for an echo? _____________________________ 7-10p.
5. Practical use. Echolocation._____________ 10-12pp.
5.1. Technical support of echolocation ________________12p.
5.2. Echolocation in animals
Echolocation system of butterflies
Echolophy in dolphins
5.3. Echolocation of blind people _____________________________ 20-21p.
6. World echo __________________________________________ 21-24pp.
7. List of used literature ________________ 24 p.
1. Introduction:
Does the beast roar in the deaf forest,
Does the horn blow, does the thunder rumble,
Does the maiden sing beyond the hill
For every sound
Your response in the empty air
You suddenly give birth ...
A.S. Pushkin
These poetic lines describe an interesting physical phenomenon - an echo. We are all familiar with him. We hear the echo, being in a forest clearing, in a gorge, floating along the river between high banks, traveling in the mountains.
It is believed that the animated image of the echo is the image of a nymph that can be heard but not seen.
According to the legend of the ancient Greeks, the forest nymph Echo fell in love with the beautiful young man Narcissus. But he did not pay any attention to her, he was completely occupied with endlessly looking into the water, admiring his reflection. The poor nymph was petrified with grief, all that remained of her was a voice that could only repeat the endings of words spoken nearby.
I saw, lit up and, mourning the rejected fate,
I became only a voice, an echo, a wind, nothing.
Translation from ancient Greek by Sergei Osherov
Alexander Kanabel, "Echo", 1887
According to another legend, the nymph Echo was punished by the wife of Zeus - the Hero. This happened because Echo tried with her speeches to divert Hera's attention from Zeus, who at that time was courting other nymphs. Noticing this, Hera became angry and made it so that Echo could not speak when others were silent, and could not be silent when others were talking. The myth of the nymph Echo reflected the attempts of the ancients to explain the physical phenomenon of the echo, which consists in the repeated reflection of sound waves.
According to another legend, Echo was in love with the forest deity Pan and they had a common daughter, Yamba, after whom the poetic size of iambs is named.
The image of a nymph, sometimes cheerful, and more often sad, can be found in poems by poets of various eras. So, we meet him in a poem by a Roman poet of the 4th century. Decima Magna Ausonius:
In your ears I, Echo, live, passing
everywhere,
write.
The image of the nymph Echo is found in one of the poems of A.A. Blok:
The leaves are lacy!
Autumn gold!
I call - and three times
I was loudly
The nymph answers, the echo answers ...
In the poem by A.A. Fet, the echo sighs, even groans:
The same bird that sang
At night he sings his song,
But that song became sadder
There is no joy in the heart.
The echo groaned softly:
Yes, it won't...
2.Reflection of sound. Echo:
The echo is formed as a result of the reflection of sound from various obstacles - the walls of a large empty room, a forest, the vaults of a high arch in a building.
We hear an echo only when the reflected sound is perceived separately from the spoken one. To do this, it is necessary that the time interval between the impact of these two sounds on the ear eardrum be at least 0.06 s.
To determine how long after a short exclamation uttered by a person, the reflected sound will reach his ear if he is standing at a distance of 2 m from this wall. The sound must travel twice the distance - to the wall and back, i.e. 4 m, propagating at a speed of 340 m/s. This will take time t=s: v, i.e.
t= 4 m: 340 m/s ≈ 0.01s.
In this case, the interval between two sounds perceived by a person - spoken and reflected - is much less than what is needed to hear the echo. In addition, the formation of an echo in the room is prevented by the furniture, curtains and other objects located in it, which partially absorb the reflected sound. Therefore, in such a room, people's speech and other sounds are not distorted by the echo, but sound clear and legible.
Large, semi-empty rooms with smooth walls, floors, and ceilings tend to reflect sound waves very well. In such a room, due to the incursion of the previous sound waves onto the subsequent ones, an overlay of sounds is obtained, and a rumble is formed. To improve the sound properties of large halls and auditoriums, their walls are often lined with sound-absorbing materials.
The action of a horn is based on the property of sound to be reflected from smooth surfaces - an expanding pipe, usually of a round or rectangular cross section. When using it, sound waves do not scatter in all directions, but form a narrow beam, due to which the sound power increases and it spreads over a greater distance.
3. Types of echo:
Single Multiple
Single echo is a wave reflected from an obstacle and received by an observer.
Let's look at the picture:
The sound source O is at a distance L from the wall. Reflected from the wall in the direction AB, the sound wave returns to the observer, and he hears the echo.
multiple echo- this is an echo that occurs with some kind of loud sound, which gives rise to not one, but several successive sound responses.
It is found in rocky areas, mountainous areas, in stone castles.
Multiple echo occurs when there are several reflective surfaces at different distances from the sound source (observer). The figure shows how a double echo can occur. The first echo signal arrives at the observer in the direction AB, and the second - along CD. The time of arrival of the first echo-signal, counted from the beginning of the original signal, is equal to 2L1/s; accordingly, the time of the second one is equal to 2L2/s.
4.How to search for an echo?
Nobody saw him
And to hear - everyone heard,
Without a body, but it lives,
Without a tongue - screaming.
Nekrasov.
Among the stories of the American humorist Mark Twain there is a funny fiction about the misadventures of a collector who had the idea to create a collection of echoes for himself! The eccentric indefatigably bought up all those plots of land where repeated or otherwise wonderful echoes were reproduced.
“First of all, he bought an echo in Georgia, which was repeated four times, then six times in Maryland, then 13 times in Maine. The next purchase was a 9x echo in Kansas, followed by a 12x echo in Tennessee, purchased cheaply because it needed repair: part of the cliff had collapsed. He thought that it could be repaired by completion; but the architect who undertook this business had never yet built an echo and therefore ruined it to the end - after processing it could only be suitable for a deaf-mute shelter ... "
This, of course, is a joke, but wonderful echoes exist in various, mostly mountainous, areas of the globe, and some have long gained worldwide fame.
A few famous multiple echoes: at Woodstock Castle in England, the echo clearly repeats 17 syllables. The ruins of Derenburg Castle near Halberstadt gave a 27-syllable echo, which, however, was silent since one wall was blown up. The rocks, spread out in the form of a circle near Adersbach in Czechoslovakia, repeat in a certain place, three times 7 syllables; but a few steps from this point, even the sound of a gunshot does not give any echo. A very multiple echo was observed in one (now defunct) castle near Milan: a shot fired from an outbuilding window was echoed 40-50 times, and a loud word - 30 times ... In a particular case, the echo is the concentration of sound by reflecting it from concave curved surfaces. So, if the sound source is placed in one of the two foci of the ellipsoidal vault, then the sound waves are collected in its other focus. This explains, for example, the famous " ear of Dionysus"in Syracuse - a grotto or recess in the wall, from which every word uttered by prisoners in it could be heard in some place remote from it. One church in Sicily had a similar acoustic property, where in a certain place one could hear whispered words in Also known in this regard are the Mormon temple at the Salt Lake in America and the grottoes in the Oliva monastery park near Danzig. In Olympia (Greece) in the temple of Zeus, the "Porch of Echo" has survived to this day. In it, the voice is repeated 5 ... 7 times. In In Siberia, there is an amazing place on the Lena River north of Kirensk.The relief of the rocky shores there is such that the echo of the horns of motor ships going along the river can be repeated up to 10 or even 20 times (under favorable weather conditions).Such an echo is sometimes perceived as a gradually fading sound, and sometimes as sound fluttering from various directions.Multiple echoes can also be heard on Lake Teletskoye in the Altai Mountains.This lake is 80 km long and only a few kilometers wide; its banks are high and steep, covered with forests. A shot from a gun or a sharp loud cry generates here up to 10 echo signals that sound for 10 ... 15 s. It is curious that often sound responses appear to the observer as coming from somewhere above, as if the echo were picked up by coastal heights.
Depending on the terrain, the location and orientation of the observer, weather conditions, time of year and day, the echo changes its volume, timbre, and duration; the number of iterations changes. In addition, the frequency of the audio response may also change; it may turn out to be higher or, conversely, lower than the frequency of the original audio signal.
It is not so easy to find a place where the echo is clearly audible even once. In Russia, however, it is relatively easy to find such places. There are many plains surrounded by forests, many clearings in the forests; it is worth shouting loudly in such a clearing so that a more or less distinct echo comes from the wall of the forest.
In the mountains, the echo is more diverse than on the plains, but it is much less common. It is more difficult to hear an echo in a mountainous area than in a forest-fringed plain.
If we imagine that a person is at the foot of a mountain, and an obstacle that should reflect the sound is placed above him, for example, in AB. It is easy to see that the sound waves propagating along the lines Ca, Cb, C c, being reflected, will not reach his ear, but will be scattered in space along the directions aa, bb, cc.
Another thing is if a person fits at the level of an obstacle or even slightly above it. The sound going down along the directions Ca, C b, will return to it along the broken lines C aaC or C bb C, reflected from the soil once or twice. The deepening of the soil between both points further enhances the clarity of the echo, acting like a concave mirror. On the contrary, if the ground between points C and B is convex, the echo will be weak and will not even reach the human ear at all: such a surface scatters sound rays like a convex mirror.
Finding echoes in uneven terrain requires some skill. Even having found a favorable place, one must still be able to evoke an echo. First of all, one should not be placed too close to the obstacle: the sound must travel a long enough way, otherwise the echo will return too soon and merge with the sound itself. Knowing that sound travels 340 meters per second, it is easy to understand that, if we are placed at a distance of 85 meters from an obstacle, we should hear an echo half a second after the sound.
Although the echo will give birth "to every sound its response in the empty air", but it does not respond to all sounds equally clearly. The echo is not the same, “whether a beast roars in a deaf forest, whether a horn blows, whether thunder rumbles, whether a maiden sings beyond the hill.” The sharper, jerkier the sound, the clearer the echo. The best way to evoke an echo is by clapping your hands. The sound of the human voice is less suitable for this, especially the voice of a man; the high tones of women's and children's voices give a more distinct echo.
There is a fluttering echo effect in large rooms measuring 20 meters or more, when there are two parallel smooth walls, or a ceiling and a floor, between which there is a sound source. It's called Flutter.
As a result of multiple reflections at the receiving point, the sound is periodically amplified, and on short impulse sounds, depending on the frequency components of the echo and the interval between them, it acquires the character of a bounce, crackles or a series of successive and fading echo signals.
5.Practical application. Echolocation:
For a long time, people did not derive any benefit from the echo, until a method was invented to measure the depth of the seas and oceans with its help. This invention was born by accident. In 1912, the huge ocean steamer Titanic sank with almost all the passengers - it sank from an accidental collision with a large ice floe. To prevent such catastrophes, they tried to use the echo in fog or at night to detect the presence of an ice barrier ahead of the ship. The method did not justify itself in practice, “but it prompted another idea: to measure the depth of the seas by reflecting sound from the seabed. The idea turned out to be very successful.
The figure below shows the setup diagram. At one side of the ship is placed in the hold, near the bottom, a cartridge that generates a sharp sound when ignited. Sound waves rush through the water column, reach the bottom of the sea, are reflected and run back, carrying an echo with them. It is captured by a sensitive device installed, like the cartridge, at the bottom of the ship. Precise clocks measure the time between the appearance of a sound and the arrival of an echo. Knowing the speed of sound in water, it is easy to calculate the distance to the reflecting barrier, that is, to determine the depth of the sea or ocean.
The echo sounder, as this installation was called, made a real revolution in the practice of measuring sea depths. The use of depth gauges of the previous systems was possible only from a stationary vessel and required a lot of time. Lotlin has to be lowered from the wheel on which it is wound rather slowly (150 m per minute); the reverse rise is almost as slow. Measuring a depth of 3 km in this way takes 3/4 hours. With the help of an echo sounder, measurements can also be made in a few seconds, at full speed of the ship, while obtaining a result that is incomparably more reliable and accurate. The error in these measurements does not exceed a quarter of a meter (for which the time intervals are determined with an accuracy of up to 3000th of a second).
If the accurate measurement of great depths is important for the science of oceanography, then the ability to quickly, reliably and accurately determine the depth in shallow places is an essential help in navigation, ensuring its safety: thanks to the echo sounder, the ship can safely and quickly approach the shore.
In modern echo sounders, not ordinary sounds are used, but extremely intense "ultrasounds" that are inaudible to the human ear, with a frequency of the order of several million vibrations per second. Such sounds are created by vibrations of a quartz plate (piezoquartz) placed in a rapidly changing electric field.
Since sound waves in air have a constant propagation speed (about 330 meters per second), the time it takes for the sound to return can serve as a source of data on the removal of an object. To determine the distance to an object in meters, it is necessary to detect the time in seconds before the return of the echo, divide it by two (the sound travels the distance to the object and back) and multiply by 330 - you get the approximate distance in meters. Based on this principle echolocation, used mainly for measuring the depth of water bodies (in this case, it must be taken into account that sound waves propagate faster in water than in air). But it is wrong to determine the distance to lightning by the difference in time between lightning and thunder. The shock wave travels faster than the speed of sound.
Echolocation can be based on the reflection of signals of various frequencies - radio waves, ultrasound and sound. The first echolocation systems sent a signal to a certain point in space and, by the response delay, determined its distance at a known speed of movement of a given signal in a given environment and the ability of an obstacle to which the distance is measured to reflect this type of signal. Inspection of a section of the bottom in this way with the help of sound took
considerable time.
radio waves also have the ability to be reflected from surfaces that are opaque to radio waves (metal, ionosphere, etc.) - radar is based on this property of radio waves.
Echo is a significant hindrance to audio recording. Therefore, the walls of the rooms in which the recording of songs, radio reports, as well as the recitation of the texts of television reports are usually equipped with sound-damping screens made of soft or ribbed materials that absorb sound. The principle of their operation is that a sound wave, falling on such a surface, is not reflected back, it decays inside due to the viscous friction of the gas. This is especially facilitated by porous surfaces made in the form of pyramids, since even reflected waves are re-radiated deep into the cavity between the pyramids and are additionally attenuated with each subsequent reflection.
5.1. Technical support of echolocation:
Echolocation can be based on the reflection of signals of various frequencies - radio waves, ultrasound and sound. The first echolocation systems sent a signal to a certain point in space and, by the response delay, determined its distance at a known speed of movement of a given signal in a given environment and the ability of an obstacle to which the distance is measured to reflect this type of signal. Inspection of a section of the bottom in this way with the help of sound took a considerable amount of time.
Now various technical solutions are used with the simultaneous use of signals of different frequencies, which can significantly speed up the process of echolocation.
5.2 Echolocation in animals:
Animals use echolocation to navigate 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 species of pinnipeds (seals), birds (guajaro, salangans, etc.).
This way 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.
Butterfly echolocation system.
Scoops (Noctuidae), or night bats, are the most species-rich family of Lepidoptera, which includes more than 20 thousand species (in our country there are about 2 thousand species). On warm summer evenings, these fluffy butterflies with sparkling yellow eyes often beat against the glass of country verandas, attracted by the light of lamps. Beautiful large butterflies also belong to the scoop family - “ribbons”, or “order ribbons”, (Catocalinae) with a red, yellow or blue pattern on the hind wings. These completely harmless creatures most often suffer from collectors for their beauty. Scoops feed on the nectar of flowers or fermented plant sap, but in the stage of caterpillars they often become the worst pests of agriculture.Cabbage cutworms (Mamestra brassicae) and winter cutworms (Agrotis segetum) are especially famous among them.
The scoops got their name because of the resemblance to owls, and the appearance of both is largely determined by the specifics of the nocturnal lifestyle. There are other elements of convergent similarity: vision adapted to very low light, a highly sensitive auditory system, and, as a necessary condition for the realization of hearing capabilities, the ability to fly silently. Both owls and scoops use their hearing for passive location: birds determine the position of their prey by their characteristic rustling, and butterflies, perceiving the echolocation signals of bats, can maneuver in time and get away from their main enemy.
Unlike the passive location system of owls, the bat sonar is an active system, since they themselves emit ultrasonic probing pulses. With the help of an echolocator, mice orient themselves well in complete darkness; when flying in dense thickets, they pick up acoustic reflections from small insects even against the background of foliage. Butterflies can hear loud clicks of mice from a distance of 35 m; this is five to six times the insect detection range of a mouse. This ratio forced predators to reorganize their hunting strategy. Some species of mice, flying up to the victim, do not use an echolocator, but are guided by the noise of the flight of the insect itself; others reorganize their location system in the direction of lowering the volume of probing signals and shifting the dominant frequencies to those areas of the ultrasonic range in which cutworms are less sensitive.
The systematic study of the acoustic relationships between bats and butterflies began in the 1950s with the advent of adequate equipment. These studies are inextricably linked with the names of American scientists K. Reder, E. Treat, G. Agee, W. Adams, Canadian J. Fullard and Danish bioacoustics under the leadership of A. Michelsen. Thanks to the efforts of these and many other researchers, the main quantitative relationships in the system of "echolocation countermeasures" of moths and bats were established.
However, not all known facts fit well into the concept of the protective function of the auditory system of butterflies. In particular, scoops that live on islands (Hawaiian and Faroe), where there are no bats, nevertheless perceive ultrasounds as well as their continental counterparts. Perhaps the ancestors of island butterflies once coexisted with bats, but their spatial isolation from predators has been going on for several tens of thousands of years. The preservation of high acoustic sensitivity in the island cutworms in a wide frequency range indicates that their auditory system can perform not only the function of protection against bats. It is interesting that butterflies that have switched from a nocturnal to a diurnal lifestyle showed signs of a reduction in the auditory system.
Even in the last century, it was known that many night butterflies themselves emit short clicks in flight. The signals of bears (Arctiidae) are now credited with a protective and warning function, since, unlike most others, these insects are inedible. Scoops (both males and females) may also click in flight. A person is able to hear these sounds, reminiscent of quiet discharges of static electricity. The subjectively low volume of clicks can be explained by the fact that only a small part of the spectral components of the signal is concentrated in the frequency range that is accessible to our hearing. The ability of scoops for acoustic emission cannot be explained within the framework of the established concept of protective behavior, since, by emitting ultrasounds, they only unmask themselves in front of bats, which use the same frequency range during echolocation.
An assumption about the ability of night butterflies to echolocation was first proposed by the English entomologist G.E. The estimates of different researchers differed by more than an order of magnitude - from 10 cm to 2 m. And although the technique of the 50s already made it possible to experimentally test the echolocation hypothesis, for some reason this direction was not developed.
Russian entomologist G.N. Gornostaev wrote about the ability of moths to active acoustic location. “It is generally accepted that the tympanal organs of butterflies serve to intercept the ultrasonic impulses of a hunting bat. However, this role of theirs is hardly the main, and even more so the only one. In our opinion, butterflies flying at the darkest time of the day should, like bats, have an echolocation system in which the tympanic organs could perform the function of receivers of reflected signals.
In order to illustrate the dynamics of the flight of a scoop of medium size (3 cm long) at a speed of 1 m / s on a scale familiar to humans, we will carry out a simple calculation: for 1 s, a butterfly flies 1 m or 33 of its dimensions. A car with a length of 3 m, passing in 1 s 33 of its length, moves at a speed of 100 m/s or 360 km/h. What kind of eyesight is needed to navigate at such a speed, using the light from the stars? It should be noted that scoops in open spaces fly at a speed significantly exceeding 1 m/s. However, butterflies usually fly slowly in thickets, but the illumination there due to shading by foliage is approximately an order of magnitude less than under the starry sky. Thus, even very sensitive vision may not be sufficient for orientation in a rapidly changing environment. True, it must be admitted that, unlike a car, a collision of an insect with an obstacle will not be such a catastrophic event.
When planning experiments to study the echolocation abilities of butterflies, we had to solve a whole range of mutually contradictory problems. The first, and perhaps most difficult, is how to separate orientation based on echolocation and visual information? If butterflies cover their eyes with some kind of paint, they stop flying, and if experiments are carried out in the dark, then how to register the behavior of an insect? We did not use infrared technology, since moths have long been suspected of being able to perceive long-wavelength optical radiation. Secondly, butterflies during the flight strongly disturb the air environment. Next to the flying insect and behind it, air vortices are formed from each stroke. Objects falling into the zone of these vortices inevitably distort the air currents, and the butterfly can, in principle, feel such changes with the help of numerous mechanoreceptors located on its wings and body. And finally, when setting up experiments, it is desirable to have some a priori information about the parameters of a hypothetical echolocation system, since experimental setups based on an estimated range of 10 cm and 2 m can be structurally completely different.
Echolocation in dolphins.
About twenty years ago dolphins were in great fashion. There was no shortage of fantastic speculation on any subject concerning these animals. Over time, fashion has passed, and speculation is deservedly forgotten.
And what is left? Something that attracted scientists from the very beginning. Dolphins are very peculiar animals. Due to the exclusively aquatic lifestyle, all systems of the dolphin's body - the sense organs, respiratory systems, blood circulation, etc. - work in completely different conditions than similar systems of terrestrial mammals. Therefore, the study of dolphins allows us to take a fresh look at many body functions and gain a deeper understanding of the fundamental mechanisms that underlie them.
Among all the systems of the dolphin's body, one of the most interesting is auditory. The fact is that under water the possibilities of vision are limited due to the low transparency of the water. Therefore, the dolphin receives basic information about the environment through hearing. At the same time, he uses an active location: he analyzes the echo that occurs when the sounds he emits are reflected from surrounding objects. Echo provides accurate information not only about the position of objects, but also about their size, shape, material, i.e. allows the dolphin to create a picture of the surrounding world no worse or even better than with the help of vision. The fact that dolphins have unusually developed hearing has been known for decades. The volume of the brain regions responsible for auditory functions is ten times larger in dolphins than in humans (although the total brain volume is approximately the same). Dolphins perceive frequencies of acoustic vibrations almost 8 times higher (up to 150 kHz) than humans (up to 20 kHz). They are able to hear sounds, the power of which is 10-30 times lower than that available to human hearing. But in order to navigate the environment with the help of hearing, it is not enough to hear sounds. We still need to subtly distinguish one sound from another. And the ability of dolphins to distinguish between sound signals has been poorly studied. We have tried to fill this gap.
Sound - vibrations of air, water or other medium with frequencies from 16 to 20,000 Hz. Any natural sound is a set of oscillations of different frequencies. From what vibrations of what frequencies the sound is composed, its height, timbre, i.e. how one sound differs from another. The ear of an animal or a person is able to analyze a sound, that is, to determine what set of frequencies it consists of. This is due to the fact that the ear works as a set of frequency filters, each of which responds to a different frequency of oscillation. For the analysis to be accurate, the tuning of the frequency filters must be "sharp". The sharper the setting, the smaller the frequency difference the ear distinguishes, the higher its frequency resolution (FRS). But sound is not just a collection of vibrations of different frequencies. Each of them is still changing over time: it becomes stronger, then weaker. The auditory system must keep up with these rapid changes in sound, and the better it does, the richer the information about the properties of the sound. Therefore, in addition to FRS, temporal resolution (VRS) is very important. HR and HRV determine the ability to distinguish one sound from another. It is these characteristics of hearing that are measured in dolphins.
To measure any characteristic of hearing, you need to solve two problems. First, you need to select test signals, that is, sounds with such properties that the ability to hear them depends on the measured property of hearing. For example, to measure sensitivity, you need to use sounds of different intensities: the weaker the sound that can be heard, the higher the sensitivity. To measure the resolution, the set of test sounds should be more complicated, but more on that below. Secondly, you need to find out whether the animal hears or does not hear the test signal. Let's start with the second task. To find out what the dolphin hears, we used the registration of the electrical activity of the brain. When exposed to sound, many cells are simultaneously excited, and the electrical potentials produced by them add up to a rather powerful signal called an evoked potential (EP). The electrical activity of an individual nerve cell can only be recorded by inserting a microscopic sensor-electrode into the animal's brain. On highly organized animals, such experiments are prohibited. The total activity of many cells (i.e., EP) can be recorded by touching the electrode to the surface of the head. This procedure is completely harmless. VP is a good indicator of whether a dolphin can hear a sound. If an EP is registered after a sound is given, it means that the auditory system is responding to this sound. If the value of the VP falls - the sound is perceived at the limit of the possible. If there is no VP, most likely, the sound is not perceived. And now about the test signals that are used to measure the heart rate. For measurement, a technique called masking is used. First, a test signal is given - sending a sound of a certain frequency. This sound causes an electrical response in the brain - EP. Then another sound is added to the sound - interference. The interference muffles the test signal, which becomes less audible, and the EP amplitude drops. The stronger the interference, the stronger the jamming, and at a certain intensity of the interference, the EP completely disappears: the masking threshold has been reached. Masking is used to measure HR because it depends on the frequency-selective properties of hearing. With different probe and noise frequencies, noise is much more needed for masking than when the frequencies are the same. This is a manifestation of frequency selectivity: the auditory system is able to distinguish between the frequencies of the test signal and noise, if they differ. The sharper the frequency selectivity, the sharper the masking weakens when the probe and noise frequencies differ. To obtain accurate quantitative data, one must find how the masking thresholds depend on the frequency difference between probe and noise.
The main result obtained in the measurement of HR by the masking method: the sharpness of auditory filters tuned to different sound frequencies. To characterize the sharpness of the filters, a measure is used here called the ratio of the tuning frequency to the equivalent filter width. We will not go into the details of how it is calculated: it is important that this is a single estimate for all tuning curves, and the higher this figure, the sharper the tuning. What do these results say?
First of all - about the exceptionally high HR, especially in the high frequency region (tens of kHz). Here the HR level reaches 50 units, i.e. dolphin hearing distinguishes frequencies that differ by only 1/50. This is 4-5 times better than in other animals and in humans. But such a high HR is observed only in the region of high frequencies, inaccessible to human hearing. In the range that is available to the hearing of both humans and dolphins, the frequency response of dolphin hearing is noticeably lower - about the same as in humans. How to measure the temporal resolution of hearing? There are several ways to do this. You can use pairs of short sound pulses: if the interval between pulses in a pair is greater than a certain value, then they are heard separately, and if less, then they merge into one click. That minimum interval at which two separate impulses can be heard is a measure of HRV. You can use a sound whose intensity pulsates rhythmically (sound modulation): the limiting frequency of pulsations at which they do not yet merge into a monotonous sound is also a measure of HRV. Another way: a short pause is made in a continuous sound. If the duration of the pause is very short, then it "slips" unnoticed. The minimum duration of a pause at which it can be detected is also a measure of HRV. And how do you know if the animal hears a repeated sound pulse, or pulsations of volume, or a short pause? Also registering the VP. With a decrease in the duration of the pause, the EP also decreases until it disappears completely. The audibility of other test signals is also determined. The experiments gave impressive results. The HRV in a dolphin turned out to be not 2-3, and not even 10, but dozens (almost 100) times higher than in humans. Human hearing allows you to distinguish time intervals of more than one hundredth of a second (10 ms). Dolphins distinguish intervals of ten-thousandths of a second (0.1-0.3 ms). Pulsations of sound volume cause EP when their frequency approaches 2 kHz (in humans - 50-70 Hz).
Why does the auditory system generally have one or another limit of HR and HRV? The simplest answer is: because this is the limit of what is possible for nature. This is the impression that was created as a result of studying the hearing of humans and many laboratory animals: in all of them, HR and HRV are quite close. But the dolphins show that the auditory system actually has both much sharper frequency tuning and better discrimination of time intervals. Why did the auditory system of other animals not achieve such indicators? Apparently, the whole point is in the inevitable contradiction between the frequency and time resolution: the better the FRS, the worse the VRS, and vice versa. This is a purely mathematical regularity, valid for any oscillatory system, and not just for the ear: if the system is sharply tuned to a certain frequency (high frequency selectivity), then it has a low temporal resolution. This can be expressed as a simple relationship: Q = F/B, where Q is the frequency selectivity (sharpness), F is the frequency to which the filter is tuned, B is the filter's bandwidth (i.e. the frequency range it passes). The rate at which the signal amplitude can change depends on B: the larger it is, the more rapid changes in the signal the filter passes, but the “dumberer” it is (less Q). Therefore, the auditory system must find some compromise between HR and HRV, limiting both of these characteristics to some level. The improvement of one of them is possible only at the expense of the deterioration of the other. The contradiction between HR and HRV becomes less dramatic as the F frequency increases: At high frequency, one can combine a wide B band with a sharp Q selectivity. This is exactly what is observed in a dolphin that has mastered the ultrasonic frequency range. For example, at an audio frequency of 100 kHz and Q = 50 (very high selectivity), the filter bandwidth B = 2 kHz, i.e. transmission of very fast, up to 2 kHz, sound modulations is possible. And at a frequency of 1 kHz, a filter with the same selectivity would allow only 20 Hz modulations to pass - this is too small. A compromise is needed here: for example, with a frequency selectivity of 10, it is possible to transmit modulations up to 100 Hz, this is already acceptable. Indeed, these are exactly the HR and HRV at this frequency in both humans and dolphins. This means that the FRS and HRV of hearing are actually caused not by the limit of what is possible for the auditory system, but by a reasonable compromise between these two characteristics. So the study of a seemingly exotic animal allows us to understand the fundamental principles of building the auditory system of all animals and humans.
Signals emitted by dolphins are used for communication and orientation by reflected sounds. The signals of the same species are varied. It turned out that there are signals of nutrition, anxiety, fear, distress, mating, pain, and so on. Species and individual differences in the signals of cetaceans have also been noted. According to high-frequency signals, catching the echo of these signals, animals orient themselves in space. With the help of an echo, dolphins, even with their eyes closed, can find food not only during the day, but also at night, determine the depth of the bottom, the proximity of the coast, and submerged objects. A person perceives their echolocation impulses as the creak of a door turning on on rusty hinges. Whether echolocation is characteristic of baleen whales, which emit signals with a frequency of only a few kilohertz, has not yet been clarified.
Dolphins send sound waves in a direction. The fat pad lying on the jaw and premaxillary bones and the concave anterior surface of the skull act as a sound lens and reflector: they concentrate the signals emitted by the air sacs and direct them in the form of a sound beam to the object being located. Experimental evidence of the operation of such an ultrasonic projector was obtained in the USSR (E.V. Romanenko, A.G. Tomilin, B.A. Artemenko) and abroad (V. Evans, D. Prescott, V. Suterland, R. Bale). The formation of an echolocation apparatus with a system of air sacs may have led to the asymmetry of the skull: the snout bones of toothed whales are developed differently on the right and left, especially in the sound emission zone. This is attributed to the fact that one sound passage is more used for making sounds, and the other for breathing.
5.3 Echolocation of blind people.
For orientation in the world, people with visual impairments may well use echolocation, moreover, their own, “natural”, which does not require the use of any technical devices. It is amazing that a person with such skills can do a lot, even ride bicycles or roller skates.
It seems incredible, but people can use echolocation, in general, in the same way that animals like bats and dolphins use it. A person can be taught to recognize sound waves reflected by surrounding objects, to determine the position, distance, and even the size of nearby objects.
Accordingly, if a person had the opportunity to find out where and what is located, then he could move in space without any problems. This orientation technique has already been developed and taught to blind people.
Developer and promoter of human echolocation ( human echolocation- this is the name of this technique) - Daniel Kish ( Daniel Kish). He himself is completely blind and has learned to navigate the world around him with the help of sounds. The essence of the method is very simple: he clicks his tongue and listens to the echo that occurs when sounds are reflected from different surfaces.
It would seem that this technique can be used only "in so far as", because the echo is barely audible. However, this is not at all the case: with its help, Daniel can move through overgrown areas and even - which is hard to believe! - ride a bike.
Some blind people believe that some of their sensations are psychic in nature. For example, such a person, walking along the alley, can feel the “pressure” from every tree that he passes. The reason for this is quite understandable: obviously, it's the echo from their steps, which is processed by the subconscious. Moreover, as it turns out, this is such an experience that it is quite possible to adopt.
6. World echo:
Repeatedly fixed from the very beginning of the era of radio delays of radio signals are called the "Stormer's paradox", "world echo", "long delayed echoes" (LDE). These are radio echoes with very long delays and anomalously low energy losses. Unlike the well-known echoes with fractional second delays, the mechanism of which has long been explained, radio signal delays of seconds, tens of seconds, and even minutes remain one of the oldest and most intriguing mysteries of ionospheric physics. Now it is hard to imagine, but at the beginning of the century, any recorded radio noises were first of all and with the ease of the assault and onslaught era, considered as signals of an extraterrestrial civilization:
“The changes I noted occurred at a certain time, and the analogy between them and the numbers was so clear that I could not link them to any reason known to me. I am familiar with natural electrical disturbances due to the sun, polar blue and telluric currents, and I was sure, as far as one can be sure of the facts, that these disturbances are not caused by any of the usual causes ... It was only after a while that it dawned on me, that the interference I observed could have been the result of conscious action. More and more, I have a premonition that I was the first to hear a greeting from one planet to another ... Despite the weakness and indistinctness, it gave me deep conviction and faith that soon all people, as one, will look at the sky above us, overflowing with love and reverence, captured by the joyful news : Brothers! We have received a message from another planet, unknown and distant. And it sounded: one ... two ... three ... "
Nikolai Tesla, 1900
But this was not the case with LDE, the idea that radio echo could be an artificial phenomenon, a kind of calling card; extraterrestrial satellite that attracts our attention, this idea was put forward only after the publication by astronomer Ronald Bracewell of a brief note printed in the journal Nature, in 1960. At the beginning, LDEs were perceived as evidence of the presence in outer space of specific clouds of rapidly moving plasma, capable of not only reflecting radio signals, like the terrestrial ionosphere, but also focusing the original signal so that the power of the reflected signal exceeds a third of the power of the original! The starting point was a letter from the engineer Jörgen Hals to the famous astrophysicist Karl Sterner.
Astrophysicist Stormer, physicist Van der Pol (the famous Van der Pol equation) and engineer Hals organized a series of experiments, the purpose of which was: to check the presence of the phenomenon and its frequency of manifestation.
In 1927, a transmitter located in Eindhoven began transmitting impulses, which were recorded by Hals in Oslo. Initially, each signal was a sequence of three Morse dots. These signals were repeated every 5 seconds. In September, the transmitter mode was changed: the intervals were increased to 20 seconds. The details of the experiment are not described in sufficient detail, since the publication of the experimental conditions took place in the proceedings of the conference and in a limited amount. On October 11, 1928, a series of radio echoes were finally recorded, as Van der Pol reports in his telegram to Stormer and Hals: “Last night our signals were accompanied by an echo, the echo time varied between 3 and 15 seconds, half of the echo is more than 8 seconds! » Hals and Stormer, in turn, confirmed receipt of these echoes in Oslo. Several series of echoes were received. Recorded radio delays ranged from 3 seconds to 3.5 minutes! In November 1929 the experiment was completed. There were exactly 5 series of radio delays recorded. In May of the same 1929, J. Gaulle and G. Talon conducted a new successful study of the LDE phenomenon.
In 1934, the phenomenon of "delayed radio echo" was observed by the Englishman E. Appleton and his data, presented in the form of a histogram, are one of the most clearly presented materials on LDE experiments.
In 1967, experiments to detect LDE were carried out at Stanford University by F. Crawford. The phenomenon was confirmed, but especially long radio echoes and series similar to those observed in the 1920s and 1930s were not detected. Often there were delays with times of 2 and 8 seconds, with a frequency shift and compression of the time between echo pulses compared to the time between pulses of the main signal. The experience of studying the known LDE data leads to another curious observation - in any new radio wave band, i.e. in the range that is just beginning to be used, the phenomenon manifests itself clearly and serially, just as in the 20s, then, after several years, the echoes “blur” and the series cease to be recorded.
The English astronomer Lunen drew attention to the fact that the echoes observed in the 1920s were free from temporal compression, and there was no Doppler frequency shift, and the intensity of the Störmer frequencies remained constant, regardless of the delay time. The last fact is very difficult to explain, remaining within the framework of the assumptions about the naturalness of the signal - natural radio echoes with a delay of 3 seconds and 3 minutes cannot fundamentally be of the same intensity - the signal is scattered, since the wave emitted by the transmitter is still not a coherent laser pulse!
It was Duncan Lunen who put forward the hypothesis that the echo of the Sterner series is a signal from an interstellar probe and the change in the delay time is an attempt to transmit some information. Assuming that this information is about the location of the planetary system from which the probe arrived, he, based on an analogy with the picture of the constellations on the stellar sphere, came to the conclusion that the home star of the senders of the probe is Epsilon Bootes. He considered one of the Shtermer series of 1928.
The arbitrariness of Lunen's geometric constructions was shown almost immediately and not by skeptics, but by the enthusiasts themselves - Bulgarian astronomy lovers, using a different decoding method, received another "homeland" of senders - the Leo zeta star, and A. Shpilevsky's decoding method finally made it possible to obtain the well-known , so expected by all, tau Kita.
The current situation was very similar to the one described in his novel "The Voice of the Lord" by Stanislav Lem - a brief note that flashed through the press and contained a hint of Contact was drowned in a sea of pseudoscientific publications, after which any serious person did not consider the entire array of information without bias . True, in the case of Lunen, the participation of special services was not needed, and disinformation was not needed - everything that happened can be considered as a verification procedure carried out, as we have already mentioned, by the enthusiasts themselves ... The fact that such “pictures” can be produced without much difficulty is shown by the figure depicted below.
It shows the coordinates of the pulses registered in the META experiment and published in the Astrophysical Journal. Each of these impulses was like the well-known Wow! and they were registered on the same "hot" line - a wave length of 21 cm! If we connect the celestial coordinates of the signals in the order determined by the dates, then we get the "trajectory" of a certain spacecraft.
It would seem that everything - here they are! But, unfortunately, this is just an artifact - the device with which the sky was scanned scanned only a very small vertical interval, and day by day this interval rose up, and then, having reached the maximum vertical mark, began to fall down.
7. List of used literature:
1. Physics textbook Grade 9 / A.V. Peryshkin, E.M. Gutnik - Moscow: "Bustbust", 2004;
2. Entertaining physics; book 1 / Ya.I. Perelman - Moscow: "Science", 1986;
3. Physics in nature; book for students / L.V. Tarasov - Moscow: "Enlightenment", 1988;
4. What? For what? Why? big book of questions and answers / Per. K. Mishina, A. Zykova - Moscow: "EKSMO - Press", 2002;
5. Theory of sound 2 volume / R e l e and J. per. from English. - Moscow, 1955; 6. Echo in the life of people and animals / Gr and f f and n D. per. from English - Moscow, 1961;
7. Great Encyclopedia of Cyril and Methodius; 2 CD - 2002;
8. European Poets of the Renaissance. - Moscow;: Fiction; 1974;
9.
Echo in the life of people and animals, trans. from English, D. Griffin, Moscow, 1961;
10.
Navigation echo sounders, Fedorov I.I., Moscow, 1948;
11. Echo sounders and other hydroacoustic means, Fedorov I. I., 1960;
12. Navigation echo sounders, “Technique and armament”, D. Tolmachev, I. Fedorov, 1977;
13. Echolocation in nature, 2nd ed., Airapetyants E. Sh., Konstantinov A. I, 1974.
