Presentation on the topic of echolocation in physics. Echolocation in humans, animals and technology. sound sources and artificial

Echolocation (film). Ultrasound is widely used in technology. For example, directed narrow beams of ultrasound are used to measure sea depth. For this purpose, an ultrasound emitter and receiver are placed at the bottom of the vessel. The emitter gives short signals that reach the bottom and, reflected from it, reach the receiver. Formula for calculating sea depth: vt. h =. 2.

Physics 9th grade

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“Impact of infrasound” - Speed ​​of sound. Maximum vibrations. Disco influence. The emergence of infrasound. Sound. The action of infrasound. Infrasound. Action of the vestibular apparatus. The concept of sound. Child. Sound range. Using pulsations.

"Physicist Isaac Newton" - Isaac Newton was buried in Westminster Abbey. He was born premature, amazingly small and frail. Many scientific laws, theorems and concepts. “The greatest mathematician of all time!” Krylov A.N. Lagrange. Newton died in Kensington, near London, in March 1727. Isaac Newton Medal. In Cambridge. The first reflecting telescope was built by Isaac Newton in 1668. At the age of fourteen, Newton invented a water clock and a kind of scooter.

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"The Jet Way of Propulsion" - Neil Armstrong. Pulse. What kind of movement is called reactive. Get acquainted with the features and characteristics of jet propulsion. Near-Earth space. Astronauts on the Moon. Do something useful for people. Derivation of the formula for the speed of a rocket during takeoff. Two-stage space rocket. Jet motion and its manifestation in nature. The crew of the Apollo 11 spacecraft. The Soviet Mir station.

1. Introduction_____________________________________________3-4 pp.

2. Reflection of sound. Echo.____________________________4-5pp.

3. Types of echo_______________________________________________ 5-7 pp.

4. How to look for an echo?______________________________7-10pp.

5. Practical use. Echolocation._____________10-12pp.

5.1. Technical support for echolocation________________12p.

5.2. Echolocation in animals___________________________ 12-13pp.

Echolocation system of butterflies___________________________ 13-16pp.

Echolophy in dolphins__________________________________________16-20pp.

5.3. Echolocation of blind people______________________________20-21pp.

6. World echo__________________________________________21-24pp.

7. List of used literature________________24 pages.

1. Introduction:

Does the beast roar in the deep forest,

Does the horn blow, does the thunder roar,

Is the maiden behind the hill singing?

For every sound

Your response in the empty air

Suddenly you give birth...

A.S. Pushkin

These poetic lines describe an interesting physical phenomenon - echo. We are all familiar with him. We hear the echo when we are in a forest clearing, in a gorge, floating along a river between high banks, traveling in the mountains.

It is believed that the animate image of the echo is the image of a nymph who can be heard, but cannot be 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 entirely occupied with endlessly looking into the water, admiring his reflection. The poor nymph was petrified from grief, all that was left of her was her voice, which could only repeat the endings of the words spoken nearby.

I saw it, lit up and, mourning the rejected fate,
I became just a voice, an echo, the wind, nothing.

Translation from ancient Greek by Sergei Osherov

Alexander Kanabel, “Echo”, 1887

According to another legend, the nymph Echo was punished by Zeus’s wife, Hero. This happened because Echo tried with her speeches to distract 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 remain silent when others spoke. The myth of the nymph Echo reflected the attempts of the ancients to explain the physical phenomenon of 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 meter of iambics 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 Ausonia:

In your ears I, Echo, live, passing

everywhere,

write.

The image of the nymph Echo is found in one of A. A. Blok’s poems:

Lacy foliage!

Autumn gold!

I call - and three times

It sounds loud to me from afar

The nymph answers, the Echo answers...

In A.A. Fet’s poem 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.

Echo moaned quietly:

Yes, it won't...

2. Sound reflection. Echo:

An 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 sound. To do this, it is necessary that the time interval between the impact of these two sounds on the eardrum is at least 0.06 s.

To determine how long after a short exclamation is made by a person, the reflected sound reaches his ear if he stands 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, spreading at a speed of 340 m/s. This will require time t=s: v, i.e.

t= 4 m: 340 m/s ≈ 0.01 s.

In this case, the interval between the two sounds perceived by a person - pronounced and reflected - is significantly less than what is necessary to hear the echo. In addition, the formation of an echo in the room is prevented by the furniture, curtains and other objects in it that partially absorb the reflected sound. Therefore, in such a room, people’s speech and other sounds are not distorted by echoes, but sound clearly and intelligibly.

Large, semi-empty rooms with smooth walls, floors and ceilings tend to reflect sound waves very well. In such a room, due to the impingement of previous sound waves onto subsequent ones, sounds are superimposed, and a hum 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, an expanding pipe usually of round or rectangular cross-section, is based on the property of sound being reflected from smooth surfaces. When using it, sound waves do not scatter in all directions, but form a narrowly directed 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 located at a distance L from the wall. Reflecting from the wall in the direction AB, the sound wave returns to the observer, and he hears an echo.

Multiple echo- this is an echo that occurs with some loud sound, which generates not one, but several successive sound responses.

Found in rocky areas, mountainous areas, and stone castles.

Multiple echoes occur when there are several reflective surfaces located at different distances from the sound source (observer). The figure shows how a double echo can occur. The first echo signal comes to the observer in the direction AB, and the second - in the direction CD. The arrival time of the first echo signal, counted from the beginning of the original signal, is 2L1/s; accordingly, the time of the second is equal to 2L2/s.

4.How to find an echo?

Nobody saw him

And everyone has heard,

Without a body, but it lives,

Without a tongue, he screams.

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 of ​​making himself a collection of echoes! The eccentric tirelessly bought up all those plots of land where multiple or otherwise remarkable 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 repairs: part of the cliff had collapsed. He thought that it could be repaired by completion; but the architect who took on this task had never built an echo and therefore completely ruined it - after processing it could only be suitable for sheltering the deaf and dumb..."

This, of course, is a joke, but wonderful echoes exist in various, mainly mountainous, areas of the globe, and some have long acquired worldwide fame.

Some famous multiple echoes: At Woodstock Castle in England, the echo clearly repeats 17 syllables. The ruins of Derenburg Castle near Halberstadt produced a 27-syllable echo, which, however, fell silent since one wall was blown up. The rocks, spread out in 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 shot 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 a sound source is placed in one of the two focuses 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 spoken by those imprisoned 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 confessional. Also known in this regard are the Mormon temple at Salt Lake in America and the grottoes in the Oliva monastery park near Danzig. In Olympia (Greece) in the Temple of Zeus, the “Porticus of the Echo” has survived to this day. In it, the voice is repeated 5...7 times. In In Siberia, on the Lena River north of Kirensk, there is an amazing place. The topography of the rocky shores there is such that the echo of the whistles of motor ships traveling along the river can be repeated up to 10 and 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 scream here generates up to 10 echo signals that sound for 10...15 s. It is curious that often the sound responses appear to the observer to come from somewhere above, as if the echo were picked up by the coastal hills.

Depending on the terrain, location and orientation of the observer, weather conditions, time of year and day, the echo changes its volume, timbre, and duration; the number of its repetitions changes. In addition, the frequency of the audio response may change; it may turn out to be higher or, conversely, lower compared to the frequency of the original sound signal.

It is not so easy to find a place where the echo is clearly heard 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’s worth shouting loudly in such a clearing that a more or less distinct echo can be heard from the forest wall.

In the mountains, echoes are more varied than on the plains, but they are much less common. It is more difficult to hear an echo in mountainous areas than on 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 sound waves propagating along the lines Ca, Cb, Cc, when reflected, will not reach his ear, but will be scattered in space in the directions aa, bb, cc.

It’s another matter if a person fits at the level of the obstacle or even slightly above it. Sound traveling down in the directions Ca, C b will return to it along broken lines C aaC or C bb C, reflecting off the soil once or twice. The deepening of the soil between both points further contributes to the clarity of the echo, acting like a concave mirror. On the contrary, if the soil 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 on uneven terrain requires some skill. Even having found a favorable place, you still need to be able to evoke an echo. First of all, you should not place yourself too close to the obstacle: the sound must travel a long enough path, otherwise the echo will return too early and merge with the sound itself. Knowing that sound travels 340 m per second, it is easy to understand that if we place ourselves at a distance of 85 m from an obstacle, we should hear an echo half a second after the sound.

Although the echo will give rise to “every sound its response in the empty air,” it does not respond equally clearly to all sounds. The echo is not the same, “whether a beast roars in a deep forest, a horn blows, thunder roars, or a maiden sings behind a hill.” The sharper and more abrupt the sound, the clearer the echo. The best way to create an echo is by clapping your hands. The sound of the human voice is less suitable for this, especially the voice of a man; high tones of women's and children's voices give a clearer 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 floor, between which there is a sound source. It's called flutter.

As a result of multiple reflections at the receiving point, the sound periodically intensifies, and on short pulsed sounds, depending on the frequency components of the echo and the interval between them, it takes on the character of rattling, crackling, or a series of successive and fading echo signals.

5.Practical application. Echolocation:

For a long time, people did not derive any benefit from echoes until a way was invented to measure the depth of seas and oceans using it. This invention was born by chance. In 1912, the huge ocean steamer Titanic sank with almost all its passengers - it sank from an accidental collision with a large ice floe. To prevent such disasters, they tried to use 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 gave rise to another idea: to measure the depth of the seas using the reflection of sound from the seabed. The idea turned out to be very successful.

The figure below shows the installation diagram. At one side of the ship there is a cartridge placed in the hold, near the bottom, which produces a sharp sound when ignited. Sound waves rush through the water column, reach the bottom of the sea, are reflected and run back, carrying with them an echo. It is detected by a sensitive device installed, like the cartridge, at the bottom of the ship. An accurate clock measures the time interval between the occurrence of a sound and the arrival of an echo. Knowing the speed of sound in water, it is easy to calculate the distance to a reflecting obstacle, that is, 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. Using depth gauges of previous systems was only possible from a stationary vessel and required a lot of time. The lotlin has to be lowered from the wheel on which it is wound quite slowly (150 m per minute); The reverse ascent is almost equally slow. Measuring a depth of 3 km using this method takes 3/4 of an hour. 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 time intervals are determined with an accuracy of 3000th of a second).

If 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 a significant help in navigation, ensuring its safety: thanks to the echo sounder, the ship can safely and quickly approach the shore.

Modern echo sounders do not use ordinary sounds, but extremely intense “ultrasounds”, inaudible to the human ear, with a frequency of several million vibrations per second. Such sounds are created by vibrations of a quartz plate (piezoquartz) placed in a rapidly varying electric field.

Since sound waves in air have a constant speed of propagation (about 330 meters per second), the time it takes for sound to return can provide information about the removal of an object. To determine the distance to an object in meters, you need to measure the time in seconds before the echo returns, 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 reservoirs (in this case it is necessary to take into account that sound waves travel faster in water than in air). But it is incorrect to determine the distance to lightning by the time difference 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, based on the response delay, determined its distance, given the known speed of movement of this signal in a given environment and the ability of the obstacle to which the distance was measured to reflect this type signal. Inspecting a section of the bottom in this way using sound took

significant time.

Radio waves They 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 interference in audio recordings. Therefore, the walls of rooms in which songs, radio reports are recorded, as well as the texts of television reports are read, are usually equipped with sound-absorbing screens made of soft or ribbed materials that absorb sound. The principle of their operation is that a sound wave hitting such a surface is not reflected back and is attenuated inside due to viscous friction of the gas. This is especially facilitated by porous surfaces made in the form of pyramids, since even reflected waves are re-emitted deep into the cavity between the pyramids and are further attenuated with each subsequent reflection.

5.1.Technical support for 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, based on the response delay, determined its distance, given the known speed of movement of this signal in a given environment and the ability of the obstacle to which the distance was measured to reflect this type of signal. Inspecting the bottom area in this way using sound took considerable time.

Nowadays various technical solutions with the simultaneous use of signals of different frequencies, which significantly speed up the echolocation process.

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 (guajaros, swiftlets, etc.).

This method 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 depth.

Echolocation system of butterflies.

Cutworms (Noctuidae), or noctules, are the richest 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 hit the glass of country verandas, attracted by the light of the lamps. The family of cutworms also includes beautiful large butterflies - “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. Cutworms feed on the nectar of flowers or fermented plant sap, but in the caterpillar stage they often become worst pests Agriculture. Of these, the cabbage cutworm (Mamestra brassicae) and the winter cutworm (Agrotis segetum) are especially famous.

Noctuids got their name because of their resemblance to owls, and appearance Both are largely determined by the specifics of the nocturnal lifestyle. There are other elements of convergent similarity: vision adapted to very low light levels, a highly sensitive auditory system and, as a necessary condition for the realization of hearing capabilities, the ability to fly silently. Both owls and moths use hearing for passive location: birds determine the position of prey by the characteristic rustling sound, 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 echolocator of bats is an active system, since they themselves emit ultrasonic probing pulses. With the help of an echolocator, mice are well oriented 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 the loud clicks of mice from a distance of 35 m; this is five to six times the detection range of an insect by a mouse. This ratio forced predators to rebuild their hunting strategy. Some species of mice, when approaching a prey, do not use an echolocator, but rely on the noise of the flight of the insect itself; others rearrange their location system to reduce the volume of probing signals and shift 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 50s 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 basic quantitative relationships in the “echolocation counteraction” system 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, cutworms living on the islands (Hawaiian and Faroe Islands), where there are no bats, nevertheless perceive ultrasound just as well as their continental counterparts. Perhaps the ancestors of island butterflies once coexisted with bats, but their spatial isolation from predators has lasted for several tens of thousands of years. The preservation of high acoustic sensitivity in a wide range of frequencies in island cutworms indicates that their auditory system can perform not only the function of protection from bats. Interestingly, butterflies that switched from a nocturnal to a diurnal lifestyle showed signs of reduction in the auditory system.

Even in the last century, it was known that many moths in flight make short clicks themselves. The signals of bears (Arctiidae) are now attributed to a protective and warning function, since, unlike most others, these insects are inedible. Noctuid owls (both males and females) can also click while 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 moths to produce acoustic emissions cannot be explained within the framework of the existing concept of protective behavior, since by emitting ultrasounds, they only unmask themselves in front of bats, which use the same frequency range for echolocation.

The assumption about the ability of moths to echolocation was first made by the English entomologist G.E. Hinton at a meeting of the Royal Entomological Society of London in 1955. The idea caused a resonance: several works appeared, including theoretical calculations of the possible range of the moth echolocator. The estimates of different researchers differed by more than an order of magnitude - from 10 cm to 2 m. And although the technology 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 perform active acoustic location. “It is generally accepted that the tympanic organs of butterflies serve to intercept ultrasonic impulses from a hunting bat. However, this is hardly their main role, much less the only one. In our opinion, butterflies flying in the darkest hours of the day should, like bats, have an echolocation system in which the tympanic organs could serve as receivers of reflected signals”1.

In order to illustrate the flight dynamics of a medium-sized moth (3 cm long) at a speed of 1 m/s on a scale familiar to humans, we will carry out a simple calculation: in 1 s a butterfly flies 1 m or 33 times its size. A car 3 m long, traveling 33 times its length in 1 s, moves at a speed of 100 m/s or 360 km/h. What kind of vision do you need to have to navigate at such speed using the light from the stars? It should be noted that cutworms fly in open spaces at speeds significantly exceeding 1 m/s. However, in thickets, butterflies usually fly slowly, but the illumination there, due to shading by leaves, is approximately an order of magnitude less than under the starry sky. Thus, even very sensitive vision may not be enough to navigate a rapidly changing environment. It must be admitted, however, that unlike a car, a collision between an insect and an obstacle will not be such a catastrophic event.

When planning experiments to study the echolocation abilities of butterflies, we had to decide the whole complex mutually contradictory tasks. The first and perhaps most difficult is how to separate orientation based on echolocation and visual information? If you cover the eyes of butterflies with some kind of paint, they stop flying, and if experiments are carried out in the dark, then how to record the behavior of the insect? We did not use infrared technology, since moths have long been suspected of having the ability to perceive long-wavelength optical radiation. Secondly, butterflies greatly disturb the air environment during flight. Air vortices are formed next to and behind the flying insect from each stroke. Objects falling into the zone of these vortices inevitably distort air flows, and the butterfly can, in principle, sense 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.

Twenty years ago, dolphins were all the rage. There was no shortage of fantastic speculation on any topic relating to these animals. Over time, fashion has passed, and speculation is deservedly forgotten.

What's left? Something that has attracted scientists from the very beginning. Dolphins are very unique animals. Due to the exclusively aquatic lifestyle, all systems of the dolphin’s body - sensory organs, respiratory systems, circulatory systems, etc. - operate under completely different conditions than similar systems of terrestrial mammals. Therefore, studying dolphins allows us to take a fresh look at many body functions and gain a deeper understanding of the fundamental mechanisms underlying them.

Among all the systems of the dolphin's body, one of the most interesting is the auditory system. The fact is that underwater vision is limited due to the low transparency of the water. Therefore, the dolphin receives basic information about its surroundings through hearing. At the same time, it uses active location: it analyzes the echo that occurs when the sounds it produces 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 in dolphins is tens of times larger than in humans (although the total volume of the brain 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 whose power is 10-30 times lower than that accessible to human hearing. But to navigate the environment with the help of hearing, it is not enough to hear sounds. You also need to subtly distinguish one sound from another. And the ability of dolphins to distinguish sound signals has been poorly studied. We 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 vibrations of different frequencies. Its pitch and timbre depend on the vibrations of which frequencies the sound is made of, i.e. how one sound differs from another. The ear of an animal or a person is capable of analyzing sound, that is, determining 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 its own vibration frequency. For the analysis to be accurate, the frequency filter settings must be “sharp”. The sharper the tuning, 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 still changes over time: it becomes stronger, sometimes weaker. The auditory system must be able to track these rapid changes in sound, and the better it does this, the richer the information about the properties of sound. Therefore, in addition to TRS, time resolution (TRS) is very important. FRS and HRV determine the ability to distinguish one sound from another. It is these hearing characteristics 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 hearing property. 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 resolution, the set of test sounds should be more complex, 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 heard, we used recordings of electrical activity in the brain. When exposed to sound, many cells are simultaneously excited, and the electrical potentials they produce add up to a fairly 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. Such experiments on highly organized animals are prohibited. The total activity of many cells (i.e., EP) can be recorded by touching the surface of the head with an electrode. This procedure is completely harmless. EP is a good indicator of whether a dolphin can hear a sound. If an EP is registered after the sound is given, it means that the auditory system reacts to this sound. If the VP value drops, the sound is perceived at the limit of what is possible. If there is no VP, most likely the sound is not perceived. And now about the test signals that are used to measure heart rate. To measure, 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 from the brain - EP. Then another sound is added to the sound - interference. The interference drowns out the test signal, which becomes less audible, and the amplitude of the EP decreases. The stronger the interference, the stronger the jamming, and at a certain intensity of interference the VP completely disappears: the masking threshold has been reached. Masking is used to measure FRS because it depends on the frequency-selective properties of hearing. At different frequencies of the sample and interference, the interference is needed much more strongly for masking than when the frequencies coincide. This is a manifestation of frequency selectivity: the auditory system is able to distinguish between the frequencies of the test signal and interference if they differ. The sharper the frequency selectivity, the more sharply the masking weakens when the frequencies of the sample and interference differ. To obtain accurate quantitative data, it is necessary to find how masking thresholds depend on the frequency difference between the sample and the noise.

The main result obtained when measuring FRS using the masking method: the acuity of auditory filters tuned to different sound frequencies. To characterize the sharpness of filters, a metric called the ratio of tuning frequency to equivalent filter width is used here. We won't go into detail about how it is calculated: the important thing is that it is a single estimate for all tuning curves, and the higher this indicator, the sharper the tuning. What do these results say?

First of all, about the exceptionally high FRS, especially in the high frequency range (tens of kHz). Here the FRS level reaches 50 units, i.e. A dolphin's hearing can distinguish frequencies that differ by only 1/50. This is 4-5 times better than in other animals and humans. But such a high FRS is observed only in the region of high frequencies inaccessible to human hearing. In the range that is accessible to the hearing of both humans and dolphins, the FRS of a dolphin’s hearing is noticeably lower - approximately the same as that of a human. 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 the pulses in a pair is greater than a certain value, then they are heard separately, and if less, they merge into one click. The minimum interval at which two separate pulses can be heard is a measure of HRV. You can use a sound whose intensity rhythmically pulsates (sound modulation): the maximum 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 the 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. How can you tell if an animal hears a repeated sound pulse, or a pulsation in volume, or a short pause? Also registering the VP. As the duration of the pause decreases, the VP also decreases until it disappears completely. The audibility of other test signals is also determined. The experiments yielded impressive results. The dolphin's HRV turned out to be not 2-3, or even 10, but tens (almost 100) times higher than that of humans. Human hearing allows one 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 in 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 for FRS and HRV? The simplest answer: because this is the limit of what is possible for nature. This is exactly the impression that was created as a result of studying the hearing of humans and many laboratory animals: in all of them, FRS and HRV are quite close. But 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 reach such indicators? Apparently, the whole point is in the inevitable contradiction between frequency and time resolution: the better the FRS, the worse the HRV, and vice versa. This is a purely mathematical law, 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 low time resolution. This can be expressed by a simple ratio: Q = F/B, where Q is the frequency selectivity (sharpness), F is the frequency to which the filter is tuned, B is the filter bandwidth (i.e., the range of frequencies that it passes). The rate at which the signal amplitude can change depends on B: the larger it is, the faster the signal changes the filter passes, but the “dumber” it is (smaller Q). Therefore, the auditory system must find some compromise between FRS and HRV, limiting both of these characteristics at some level. Improvement of one of them is possible only at the expense of the deterioration of the other. The contradiction between FRS and HRV becomes less dramatic as the F frequency increases: At high frequencies, it is possible to combine a wide B band with sharp Q selectivity. This is exactly what is observed in the dolphin, which has mastered the ultrasonic frequency range. For example, with a sound frequency of 100 kHz and Q = 50 (very high selectivity), the filter bandwidth is B = 2 kHz, i.e. It is possible to transmit very fast, up to 2 kHz, sound modulations. And at a frequency of 1 kHz, a filter with the same selectivity would allow modulations with a frequency of only 20 Hz to pass through - this is too low. A compromise is necessary here: for example, with a frequency selectivity of 10, it is possible to transmit modulations up to 100 Hz, this is already acceptable. And indeed, this is exactly what FRS and HRV are at this frequency in both humans and dolphins. This means that the FRS and HRV of hearing are actually determined not by the limit of what is possible for the auditory system, but by a reasonable compromise between these two characteristics. Thus, the study of a seemingly exotic animal allows us to understand the fundamental principles of building the auditory system of all animals and humans.

The signals emitted by dolphins are used for communication and orientation based on reflected sounds. Signals vary within the same species. It turned out that there are signals of nutrition, anxiety, fear, distress, mating, pain, etc. Species and individual differences in cetacean signals have also been noted. Using high-frequency signals, catching the echo of these signals, animals orient themselves in space. With the help of 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 shore, and submerged objects. A person perceives their echolocation impulses as the creaking of a door turning on rusty hinges. Whether echolocation is characteristic of baleen whales, which emit signals with a frequency of only up to several kilohertz, has not yet been clarified.

Dolphins send sound waves directionally. 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 located object. Experimental evidence of the action of such an ultrasonic spotlight was obtained in the USSR (E.V. Romanenko, A.G. Tomilin, B.A. Artemenko) and abroad (V. Evans, D. Prescott, V. Sutherland, R. Bale). The formation of an echolocation apparatus with a system of air sacs may have led to the asymmetry of the skull: the bones of the snout of toothed whales on the right and left are developed unequally, especially in the zone of sound emission. This is due to the fact that one sound passage is used more for making sounds, and the other for breathing.

5.3.Echolocation of blind people.

To navigate the world, people with visual impairments can easily use echolocation, their own, “natural” one, which does not require the use of any technical devices. It’s 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 or dolphins use it. A person can be taught to recognize sound waves reflected by surrounding objects, to determine the position, distance and even size of objects located nearby.

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 method has already been developed and is being taught to blind people.

Developer and popularizer 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 only be used “to the extent”, because the echo is barely audible. However, this is not at all true: 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 extrasensory in nature. For example, such a person, walking along an alley, can feel “pressure” from every tree he passes by. The reason for this is quite understandable: obviously, the matter is in the echo from their steps, which is processed by the subconscious. Moreover, as it turns out, this is an experience that can be adopted.

6. World Echo:

Delays of radio signals that have been repeatedly recorded since the very beginning of the radio era are called the “Stoermer paradox”, “world echo”, “long delayed echoes” (LDE). This refers to radio echoes with very long delays and abnormally low energy losses. In contrast to the well-known echoes with delays of a fraction of a second, the mechanism of which has long been explained, delays of radio signals of seconds, tens of seconds and even minutes remain one of the most long-standing and intriguing mysteries of ionospheric physics. It’s hard to imagine now, but at the beginning of the century, any recorded radio noise was first of all, and with the ease of the era of storm and pressure, considered as signals of an extraterrestrial civilization:

“The changes I noted occurred at a certain time, and the analogies between them and the numbers were so clear that I could not link them with any reason known to me. I'm familiar with natural electrical interference arising from the sun, polar blue and telluric currents, and I was confident, as only one can be confident in facts, that these disturbances were not due to any of the usual causes... Only after some time it dawned on me that the disturbances I observed could arise as a result of conscious actions. The premonition that I was the first to hear a greeting from one planet to another is gripping me more and more... Despite the weakness and vagueness, it gave me deep conviction and faith that soon all people as one will look at the sky above us, filled with love and respect, captured by the good news : Brothers! We received a message from another planet, unknown and distant. And it sounded: one... two... three...”
Nikolai Tesla, 1900

But that wasn't the case with LDE - the idea that a radio echo could be an artificial phenomenon is peculiar business card; extraterrestrial satellite attracting our attention, this idea was put forward only after the publication of a short note by astronomer Ronald Bracewell in the journal Nature in 1960. In the beginning, LDEs were perceived as evidence of the presence in outer space of specific clouds of fast-moving plasma, capable of not only reflecting radio signals, like the earth's 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 engineer Jörgen Hals to the famous astrophysicist Karl Stoermer.

Astrophysicist Stoermer, physicist Van der Pol (the famous Van der Pol equation) and engineer Hals organized a series of experiments whose purpose was to test the presence of the phenomenon and its frequency of occurrence.

In 1927, a transmitter located in Eindhoven began transmitting pulses that 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 occurred in the proceedings of the conference and in a limited volume. On October 11, 1928, a series of radio echoes were finally registered, Van der Pol reports this in his telegram to Stoermer and Hulse: “Last night our signals were accompanied by echoes, the echo time varied between 3 and 15 seconds, half the echo more than 8 seconds! » Hulse and Stoermer, in turn, confirmed receipt of these echoes in Oslo. Several series of echoes were received. The recorded radio delays ranged from 3 seconds to 3.5 minutes! In November 1929, the experiment was completed. There were 5 series of radio delays that were accurately 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 particularly long radio echoes and series, similar to those observed in the 20-30s, were not detected. Delays with times of 2 and 8 seconds were often encountered, 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 known LDE data leads to another interesting observation - in any new radio wave range, 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 are no longer recorded.

The English astronomer Lunen noted that the echoes observed in the 1920s were free of time compression, and there was no Doppler frequency shift, and the intensity of the Sturmer frequencies remained constant, regardless of the delay time. Last fact it is very difficult to explain, remaining within the framework of assumptions about the naturalness of the signal - natural radio echoes with a delay of 3 seconds and 3 minutes fundamentally cannot 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 Sturmer series is a signal from an interstellar probe and the change in delay time is an attempt to transmit some information. Assuming that this information was about the location of the planetary system from which the probe arrived, he, based on an analogy with the picture of constellations on the stellar sphere, came to the conclusion that the home star of the probe senders is Epsilon Bootes. He examined one of Stoermer's 1928 series.

The arbitrariness of Lunen’s geometric constructions was shown almost immediately, not by skeptics, but by the enthusiasts themselves - Bulgarian astronomy lovers, using a different decryption method, received another “homeland” of the senders - the star Zeta Leo, and A. Shpilevsky’s decryption method finally made it possible to obtain the well-known , so expected by everyone, Tau Keith.

The current situation was very similar to the one described in his novel “The Voice of the Lord” by Stanislav Lem - a short note that appeared in the press and contained a hint about 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 already mentioned, by the enthusiasts themselves... The fact that such “pictures” can be produced without special labor shows the picture below.

It depicts the coordinates of pulses recorded in the META experiment and published in the Astrophysical Journal. Each of these impulses was similar to the well-known “signal” Wow! and they were registered on that same “hot” line – a wave 21 cm long! If you combine the celestial coordinates of the signals in the order determined by the dates, you get the “trajectory” of a certain spacecraft.

It would seem that's it - 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 9th grade / A.V. Peryshkin, E.M. Gutnik - Moscow: “Bustard”, 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 / Transl. K. Mishina, A. Zykova - Moscow: "EXMO - Press", 2002;

5. Theory of sound 2 volume / R e le and J. lane from English - Moscow, 1955; 6. Echo in the life of people and animals / G r i f f i n D. trans. from English - Moscow, 1961;

7. Great Encyclopedia of Cyril and Methodius; 2 CD – 2002;

8. European poets of the Renaissance. - Moscow;: Fiction; 1974;

9. Echoes in the lives of people and animals, trans. from English, Griffin D., 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, “Equipment and weapons”, Tolmachev D., Fedorov I., 1977;

13. Echolocation in nature, 2nd ed., Airapetyants E. Sh., Konstantinov A. I, 1974.

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 range from 16 to 20,000 Hz.

2. Can sound waves travel in airless space?

a) can, for example, the sound of a gunshot in airless space;

b) cannot: sound waves propagate only in matter;

c) they can if the sound waves are transverse.

3. What quantities does pitch depend on?

a) on amplitude;

b) from frequency;

c) from volume;

d) on the speed of sound.

4. How does sound propagate in a homogeneous medium?

a) sound travels linearly at a constant speed in one direction;

b) sound travels in all directions, speed decreases with distance;

V) sound travels straight and at constant speed in all directions.

5. What does the speed of sound in air depend on? a) on the volume of sound;

b) from the pitch of the sound;

c) on temperature;

d) on the speed of the sound source.

6. What does the pitch of sound depend on?

a) on the amplitude of vibrations;

b) on the wavelength;

c) on the frequency of vibration 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 tongue - it screams!.......

Echoes are sound waves reflected from an obstacle and returned to their source.

The name "echo" is associated with the name of the mountain nymph Echo

The ancient Greeks came up with a very a beautiful legend to explain the echo. Once upon a time 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 the handsome young Narcissus and immediately fell in love with him. However, Narcissus did not notice her. The nymph was overcome by such sadness that Echo disappeared into the air, leaving only her voice. And we hear her voice, which repeats everything we say.

Education echo

An 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 sound. To do this, it is necessary that the time interval between the impact of these two sounds on the eardrum is at least 0.06 s.

Echo in the mountains

The most amazing echo “lives” in the mountains. There it is repeated many times, due to multiple reflections of sound.

What is an echo like?

There are several types of echo:

• One time e is a wave reflected from an obstacle and received by an observer.

2) Multiple - this is an echo that arises from some loud sound, which generates not one, but several sound responses following each other.

Cons of echo

The big disadvantage of echo is that it is a significant interference in audio recording. Therefore, the walls of the rooms in which songs and radio reports are recorded are usually equipped with sound-absorbing screens made of soft or ribbed materials that absorb sound.

Styrofoam

Application of echo

Since sound waves travel at a constant speed in air (about 340 meters per second), the time it takes for sound to return can provide information about the removal of an object.

1.Acoustic echo is used in sonar, as well as in navigation, where echo sounders are used to measure bottom depth.

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 they gave 27-syllable an echo that, however, has fallen silent since one wall was blown up.

Rocks, spread out in the shape 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 shot does not give any echo.

Quite multiple echoes were observed in one (now defunct) castle near Milan : shot, produced from the outbuilding window, echoed 40 - 50 times, A big word - 30 times .

At Woodstock Castle in England the echo clearly repeated 17 syllables(destroyed during the Civil War

Echolocation. Ultrasonic waves can be obtained using special high-frequency emitters. A narrow parallel beam of ultrasonic waves expands very little during propagation. Thanks to this, an ultrasonic wave can be generated in a given direction. Directional narrow beams of ultrasound are used, in particular, to measure sea depth. For this purpose, an ultrasound emitter and receiver are placed at the bottom of the vessel. The emitter gives short signals that are sent towards the bottom. In this case, the time of sending each signal is recorded by the device. Reflecting from the seabed, the ultrasonic signal reaches the receiver after some time. The moment the signal is received is also recorded. Thus, during the time t that passes from the moment the signal is sent to the moment it is received, the signal propagating at speed v travels a path equal to twice the depth of the sea, i.e. 2h: From here it is easy to calculate the depth of the sea: The described method for determining the distance to an object is called echolocation.

Dimensions: 720 x 540 pixels, format: .jpg. To download a slide for free to use in class, right-click on the image and click “Save Image As...”. You can download the entire presentation “Infrasound and Ultrasound.ppt” in a zip archive of 765 KB in size.

"Ultrasonography"- Ultrasonic facial skin peeling. In ophthalmology, ultrasound location is used to determine the size of the ocular media. Using ultrasound, you can also determine the number of embryos or determine the death of the fetus. Application of ultrasound in medicine. The use of ultrasound for diagnosis of serious head injuries allows the surgeon to determine the location of hemorrhages.

“Ultrasound in medicine” - Is ultrasound treatment harmful? Ultrasound treatment. Children's encyclopedia. Ultrasound in medicine. Is ultrasound harmful? Ultrasonography. The birth of ultrasound. Plan. Ultrasound procedures. Ultrasound to help pharmacologists.

"Ultrasound Physics"- The influence of infrasound on the human body. Ultrasonic peeling. Predicting storms at sea. Wide Application at home. Geology and geophysics. Application of ultrasound. Ultrasonic waves accelerate the diffusion processes. Forensics. Anti-inflammatory effect. Properties of ultrasound. Mechanical vibrations.

“Infrasound and ultrasound” - Sources of infrasound waves. Ultrasound. Infrasound. Ultrasound and infrasound.

"Ultrasound and infrasound physics"- How do some sounds differ from others? SOUND Man lives in a world of sounds. But isolated vibrations of one body do not exist. The sounds of running cars, moving vehicles, etc. What is sound? Diagram depicting sound waves. Overlay of sound waves. Ultrasound has also found application in medicine.

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