Can the bat sending a frequency signal. How bats navigate. Conservation status of the bat
Bats usually live in huge flocks in caves, in which they perfectly navigate in complete darkness. Flying in and out of the cave, each mouse makes sounds that are inaudible to us. At the same time, thousands of mice make these sounds, but this does not prevent them from perfectly navigating in space in complete darkness and flying without colliding with each other. Why can bats fly confidently in total darkness without bumping into obstacles? The amazing property of these nocturnal animals - the ability to navigate in space without the help of vision - is associated with their ability to emit and capture ultrasonic waves.
It turned out that during the flight, the mouse emits short signals at a frequency of about 80 kHz, and then receives reflected echoes that come to it from nearby obstacles and from insects flying nearby.
In order for the signal to be reflected by an obstacle, the smallest linear size of this obstacle must be no less than the wavelength of the sound being sent. The use of ultrasound makes it possible to detect smaller objects than could be detected using lower sound frequencies. In addition, the use of ultrasonic signals is due to the fact that with a decrease in the wavelength, the directionality of the radiation is easier to realize, and this is very important for echolocation.
The mouse begins to respond to a particular object at a distance of about 1 meter, while the duration of the ultrasonic signals sent by the mouse decreases by about 10 times, and their repetition rate increases to 100–200 pulses (clicks) per second. That is, having noticed the object, the mouse starts clicking more often, and the clicks themselves become shorter. The smallest distance a mouse can detect in this way is approximately 5 cm.
While approaching the object of hunting, the bat, as it were, estimates the angle between the direction of its speed and the direction to the source of the reflected signal and changes the direction of flight so that this angle becomes smaller and smaller.
Can a bat, by sending out a signal at 80 kHz, detect a 1 mm midge? The speed of sound in air is assumed to be 320 m/s. Explain the answer.
End of form
Form start
Ultrasonic echolocation of mice uses waves with a frequency
1) less than 20 Hz
2) 20 Hz to 20 kHz
3) over 20 kHz
4) any frequency
End of form
Form start
The ability to perfectly navigate in space is associated in bats with their ability to emit and receive
1) only infrasonic waves
2) only sound waves
3) only ultrasonic waves
4) sound and ultrasonic waves
Sound recording
The ability to record sounds and then play them back was discovered in 1877 by the American inventor T.A. Edison. Thanks to the ability to record and reproduce sounds, sound cinema was born. The recording of musical works, stories and even whole plays on gramophone or gramophone records has become a mass form of sound recording.
Figure 1 shows a simplified diagram of a mechanical sound recorder. Sound waves from a source (singer, orchestra, etc.) enter the horn 1, in which a thin elastic plate 2, called a membrane, is fixed. Under the action of a sound wave, the membrane vibrates. The vibrations of the membrane are transmitted to the cutter 3 associated with it, the tip of which draws a sound groove on the rotating disk 4. The sound groove twists in a spiral from the edge of the disk to its center. The figure shows a view of the sound grooves on the record, viewed through a magnifying glass.
The disc on which sound is recorded is made of a special soft wax material. A copper copy (cliché) is removed from this wax disc by electroforming. This uses the deposition of pure copper on the electrode when an electric current passes through a solution of its salts. The copper copy is then imprinted on plastic discs. This is how gramophone records are made.
When playing sound, a gramophone record is placed under a needle connected to the membrane of the gramophone, and the record is brought into rotation. Moving along the wavy groove of the plate, the end of the needle vibrates, and the membrane vibrates with it, and these vibrations quite accurately reproduce the recorded sound.
When recording sound mechanically, a tuning fork is used. With an increase in the sounding time of the tuning fork by 2 times
1) the length of the sound groove will increase by 2 times
2) the length of the sound groove will decrease by 2 times
3) the depth of the sound groove will increase by 2 times
4) the depth of the sound groove will decrease by 2 times
End of form
2. Molecular physics
Surface tension
In the world of everyday phenomena around us, there is a force at work that is usually ignored. This force is relatively small, its action does not cause powerful effects. Nevertheless, we cannot pour water into a glass, we cannot do anything at all with this or that liquid without setting in motion forces that are called surface tension forces. These forces play a significant role in nature and in our life. Without them, we could not write with a fountain pen, all the ink would immediately pour out of it. It would be impossible to soap your hands, because the foam could not form. A light rain would soak us through. The water regime of the soil would be disturbed, which would be disastrous for plants. Important functions of our body would suffer.
The easiest way to capture the nature of surface tension forces is with a poorly closed or faulty water tap. The drop grows gradually, over time a narrowing is formed - a neck, and the drop comes off.
Water is, as it were, enclosed in an elastic bag, and this bag breaks when gravity exceeds its strength. In reality, of course, there is nothing but water in the drop, but the surface layer of water itself behaves like a stretched elastic film.
The film of a soap bubble makes the same impression. It looks like a thin stretched rubber of a baby ball. If you carefully place the needle on the surface of the water, the surface film will bend and prevent the needle from sinking. For the same reason, water striders can glide across the surface of the water without falling into it.
In its attempt to shrink, the surface film would give the liquid a spherical shape if it were not for gravity. The smaller the droplet, the greater the role played by surface tension forces compared to gravity. Therefore, small droplets are close in shape to a ball. In free fall, a state of weightlessness occurs, and therefore raindrops are almost strictly spherical. Due to the refraction of the sun's rays, a rainbow appears in these drops.
Surface tension is caused by intermolecular interaction. Liquid molecules interact with each other more strongly than liquid molecules and air molecules, so the molecules of the surface layer of the liquid tend to get closer to each other and sink deep into the liquid. This allows the liquid to take a form in which the number of molecules on the surface would be minimal, and the ball has the minimum surface for a given volume. The surface of the liquid contracts and this leads to surface tension.
Everyone knows that bats use echolocation to move around. Even five year olds know this. To date, we know that this ability is not unique to bats. Dolphins, whales, some birds, and even mice also use echolocation. However, until recently, we had no idea how complex and powerful bat voices really are. Scientists have discovered that these unique creatures use their strange vocalizations in all sorts of startling ways. The night is filled with the chirping and squeaking of these aerial hunters, and we are only just beginning to learn all their secrets. If you think dolphin clicks and whistles are amazing, then get ready to learn about the real masters of sound.
10 Bats Can't Be Fooled
It was once thought that bats could only see moving insects. In fact, some moths freeze when they hear a bat approach. Apparently, the big-eared leaf bat from South America does not know about it. The study showed that they can spot sleeping dragonflies that don't move at all. The big-eared bat "shrouds" the target with a constant stream of echolocation. In three seconds, they can determine if their chosen target is edible. Thus, a bat can feast on a sleeping insect, which, apparently, does not hear how it is screaming at it.
Naturally, scientists initially considered this all impossible. There was no reason to assume that bat echolocation is so sensitive that it can detect various forms. They summed it up as follows: "Active perception of silent and motionless prey in the dense vegetation of the undergrowth was considered impossible." However, the big-eared leaf-bearer succeeds.
To further confuse scientists, the big-eared leaf bat can also tell a real dragonfly from an artificial one. The scientists tested the bats with real dragonflies and fake ones made from paper and foil. Despite the fact that initially all the bats became interested in fakes, none of them bit the artificial dragonfly. These bats can not only determine the shape of an object using echolocation, but also hear the difference in the material from which this object is made.
9 Bats Locate Plants Using Echolocation 
Photograph: Hans Hillewaert
A huge number of bats feed exclusively on fruits, but they fly out in search of food only at night. So how do they find food in the dark? Scientists initially believed that they find the target with the help of their nose. This is because it would be quite difficult to sort through the various forms of plants in a dense canopy using echolocation alone. Theoretically, everything would be as if in a fog.
Of course, it's possible that bats can see insects in trees, but no one would have thought that these winged rodents could use sound to determine the type of plant (bats aren't rodents, by the way). However, bats in the leaf-nosed subfamily known as the Glossophagine can do just that. They find their favorite plants with just a sound. Scientists have no idea how they accomplish this feat. "Echoes produced by plants are very complex signals bouncing off the many leaves of this plant." In other words, it's incredibly difficult. However, these bats have no problem using this method. They locate flowers and fruits without any problem. Some plants even have leaves shaped like satellite dishes specifically to attract bats. Once again, bats prove that we still have a lot to learn about sound.
8. High frequency
The ultrasonic bat chirp can be quite high. A person hears sounds in the range from 20 hertz to 20 kilohertz, which is quite good. For example, the best soprano singer can only reach a note at a frequency of approximately 1.76 kilohertz. Most bats can chirp between 12 and 160 kilohertz, comparable to dolphins.
The bright decorated smooth-nosed makes the highest frequency sound of all animals in the world. Their range starts at 235 kilohertz, which is much higher than the frequency that humans can hear, and ends at around 250 kilohertz. This little fluffy mammal can make sounds that are 120 times higher than the voice of the best singer in the world. Why do they need such powerful audio equipment? The scientists believe that these high frequencies "significantly concentrate the sonar of this bat species and reduce its range." In the dense jungles where these bats live, such echolocation can give them an advantage in detecting insects among all the rustling of leaves and branches. This species can focus its echolocation in a way that no other species can.
7. Super ears
The pointy ears of bats never get enough attention. Everyone is interested only in the sound itself, and not in the receiving device. So the engineering department at Virginia Tech has finally studied the ears of bats. Initially, no one believed what they discovered. In one tenth of a second (100 milliseconds), one of these bats can "significantly change its ear shape so that it perceives different sound frequencies." How fast is it? It takes a human three times longer to blink than a horseshoe-nosed bat to reshape its ear to tune in to specific echoes.”
Bat ears are super antennas. Not only can they move their ears at lightning speeds, but they can also “process overlapping echoes that come in as little as 2 millionths of a second apart. They can also distinguish between objects that are only 0.3 millimeters apart.” To make it easier for you to imagine - the width of a human hair is 0.3 millimeters. Therefore, it is not at all surprising that the navy is studying bats. Their biological sonar is far superior to any technology invented by man.
6. Bats recognize their friends
Like humans, bats have best friends they love to hang out with. Each day, as hundreds of bats in a colony get ready for bed, they are assigned to the same social groups over and over again. How do they find each other in such a huge crowd? Of course, with the help of a cry.
The researchers found that bats can recognize the individual calls of members of their social group. Each bat has a "special vocalization that has its own acoustic image." Sounds like bats have their own names. These unique individual acoustic images are considered salutations. When friends meet, they sniff each other's armpits - after all, nothing strengthens friendship like inhaling the scent of bats' armpits.
Another way in which bats transmit individual signals is to hunt for food. When many bats hunt in the same area, they emit a prey signal that everyone else can hear. The purpose of this signal is a kind of statement: "Hey, this beetle is mine!". Surprisingly, these calls for finding food are also unique to each individual, so when one bat from an entire flock calls out “Mine!”, all the other bats in the colony know who found their food.
5. Telephone system
Madagascar suckerfoot colonies are nomadic and constantly move from place to place to avoid predators. They sleep in rolled heliconia and calathea leaves, each of which can hold several small bats. So how do these scurrying balls of fluff communicate with the rest of the colony if they spread throughout the forest? They use nature's public address system to communicate with their friends.
The leaf funnels help amplify the calls of the bats inside by as much as two decibels. Leaves are also great at directing sound. Research shows that bats that were already in their leaf shawls made a special sound to help their friends find them. The bats outside responded by screaming, playing a sort of game of Marco Polo until they found their kind. Usually they had no problem finding the right perch.
The leaves work even better in terms of amplifying the sound of incoming screams, increasing their volume by as much as 10 decibels. It's like living inside a megaphone.
4. Noisy wings
Not all bats have developed vocalizations. In fact, most bat species do not have the ability to create the same clicks and squeaks that most other bat species use for echolocation. However, this does not mean that they cannot move around the area at night. It has recently been discovered that many species of fruit bats can navigate in space using the flapping sounds they make with their wings. In fact, the researchers are so taken aback by this discovery that they have run multiple tests just to make sure the sounds are not coming from the mouths of these bats. They even went so far as to seal the mouths of bats and inject anesthetic into their tongues. These mice, with their mouths sealed with duct tape and lidocaine injected into their tongues, were subjected to such torture only so that scientists could be 100 percent sure that the bats weren't fooling them with their mouths.
So how do these bats use their wings to create the sounds they use for echolocation? Believe it or not, no one has figured it out yet. Flying and flapping at the same time is a secret that these smart mammals don't want to give away. However, this is the first discovery of the use of non-vocal sounds for navigation, and scientists are very excited about this.
3. Vision in a whisper
Photograph: Ryan Somma
Based on the fact that bats find their prey using echolocation, some animals, such as moths, have evolved the ability to determine the echolocation of bats. This is a prime example of the classic evolutionary battle between predator and prey. The predator develops a weapon, its potential prey finds a way to counteract it. Many moths fall to the ground and are immobile when they hear a bat approach.
The shrew-like, long-tongued vampire has found a way to bypass the sensitive hearing of moths. Scientists were surprised to find that these bats fed almost exclusively on moths, which must have heard their approach. So how do they catch their prey? The shrew-like long-tongued vampire uses a quieter form of echolocation that moths cannot detect. Instead of echolocation, they use "whisper location". They use the equivalent of bat stealth to snatch unsuspecting moths. A study of another species of whispering bat called the European broad-eared or snub-nosed ear bat showed that the vocalization of this species of bat is 100 times quieter than that of other species.
2. The fastest mouth ever
There are ordinary, unremarkable muscles, but there are also those that can only be described as super muscles. Rattlesnakes have extreme tail muscles that allow them to rattle the tip of their tail at incredible speed. The swim bladder of the pufferfish is the fastest twitch muscle of all vertebrates. If we talk about mammals, then there is no faster muscle than the pharynx of a bat. It can contract at a rate of 200 times per minute. It's 100 times faster than you can blink. With each contraction, a sound is produced.
Scientists have wondered what the upper limit of bat sonar is. Based on the fact that the echo returns to the bat in just one millisecond, their calls begin to overlap each other at a speed of 400 echoes per minute. Studies have shown that they can hear up to 400 echoes per second, so only the larynx stops them.
In theory, it is quite possible that there are those who are able to break this record. None of the mammals known to science possess muscles that can move so quickly. The reason they can perform these amazing sonic feats is because they actually have more mitochondria (the body's batteries) as well as calcium-carrying proteins. This gives them more power and allows their muscles to contract much more frequently. Their muscles are literally super charged.
1. Bats go fishing
Some bats prey on fish. This seems completely ridiculous, because echolocation does not travel through water. It bounces off her like a ball hitting a wall. So how do fish-eating bats do it? Their echolocation is so sensitive that they can detect ripples on the surface of the water that give away fish swimming right at the surface of the water. The bat does not actually see the fish. Their echolocation never reaches the prey itself. They find fish swimming near the surface of the water by reading the splashes of water on the surface with the help of sound. It's just an amazing ability.
It turns out that some bats use the same technique to catch frogs. If a frog sitting in the water sees a bat, it freezes. But she is betrayed by the ripples spreading through the water from her body. Another interesting fact about bats and water is that from birth they are programmed to believe that any acoustically smooth surface is water and they descend on it to drink. Apparently, if you put a large smooth plate in the middle of the jungle, young bats will dive face down into it in an attempt to quench their thirst. Therefore, on the one hand, the echolocation of bats is so sensitive that they can read the surface of the lake like a book. On the other hand, young bats cannot tell a tray from a puddle.
Butterfly bear Bertholdia trigona- the only animal known in nature that can defend itself against bats by jamming their location signals. Mice cannot learn to catch this type of bear that emits characteristic ultrasonic clicks. However, how exactly do butterfly clicks work? B. trigona on bats was unknown. American biologists set up behavioral experiments in which they tested three possible mechanisms. It turned out that the signals emitted B. trigona, reduce the accuracy with which the bat determines the distance to it. As a result of the clicks emitted by the butterfly, the bat changes the nature of its signals, which makes it even more difficult to catch the butterfly. The authors believe that this behavior B. trigona could have arisen from an older method of defense known in some butterflies - when acoustic signaling is accompanied by the release of chemicals that repel predators.
Bats and moths have been in an evolutionary race for at least 50 million years. In the process of this struggle, butterflies have developed a fairly simple design of auditory organs, which contributes to a quick warning of an approaching danger and launching a predator avoidance reaction. Butterflies in the Ursa family, or Arctiidae, are also capable of emitting ultrasonic clicks, with different species doing so in different ways. Many of them make clicks quite rarely, but the acoustic signal is accompanied by the release of odorous substances that repel bats. Other species have learned to imitate these inedible butterflies by clicking and emitting no odors (Barber and Conner, 2007). Another method of defense is clicking in order to frighten an inexperienced bat. This method, however, is not very reliable, because the mice learn and after a few attempts they stop paying attention to the clicking of the butterfly.
Recently, American scientists from Wake Forest University have shown that one species of she-bear, Bertholdia trigona, can emit frequent ultrasonic signals that jam the echolocation signals of bats (Corcoran et al., 2009). It is remarkable that bats are not able to learn how to deal with this obstacle: after numerous attempts, the mouse still fails to catch the butterfly. Now the same authors have set the task of elucidating the mechanism by which B. trigona so skillfully defends itself (Corcoran et al., 2011). They proposed three hypotheses.
According to the first illusory echo hypothesis, - the bat may confuse the butterfly signals with an echo of its own signal from an object that does not exist. In this case, the mouse must change its flight path, flying away from a non-existent object. According to the second - remote interference hypothesis, - the signals emitted by the butterfly can reduce the accuracy of the bat in determining the distance to the prey. This can happen if the butterfly's clicks precede the echo from the bat's own signal. Finally, according to the third masking hypothesis, - butterfly signals can completely mask it, and it becomes "invisible" to the bat.
The behavior of a bat in an experiment can show which hypothesis is correct. The mouse will either change its flight path, or it will try to catch the butterfly and miss, or it will not perceive the butterfly at all and will continue flying.
Behavioral experiments were carried out for seven nights in a soundproof room measuring 5.8 x 4.0 x 3.0 m. Eptesicus fuscus, belonging to the family of smooth-nosed bats. Experiments were carried out on three individuals E. fuscus.
It was preliminary shown that all three mice willingly ate the studied species of she-bears if the butterflies did not make sounds (the absence of acoustic signals was recorded in 22% of the butterflies). Before each experiment, we checked how reliably the mouse caught control butterflies that did not emit signals. As a control, we used Galleria melonella. After that, every night 16 butterflies (4 - B. trigona, 4 - other types of bears that do not make a sound, 8 - G. melonella) were randomly presented to one bat. The butterflies were attached to a 60 cm long thread. The mouse could attack the butterfly several times, but only the first attack was taken into account for analysis.
All experiments were recorded on two high-speed video cameras (250 frames per second). These records were analyzed using a computer program (MATLAB), which made it possible to calculate the three-dimensional coordinates of objects in the field of view of the cameras. As a result, the flight vector, the minimum distance between the mouse and the butterfly, and the vector from the mouse to the butterfly were calculated at each moment of each interaction. The angle φ was determined as the angular deviation between the mouse flight vector and the vector between the mouse and the butterfly (Fig. 1).
butterflies B. trigona, like the rest of the she-bear, they make clicks with the so-called timbal organs (see Tymbal). These organs have been well studied in song cicadas, but in butterflies they have a slightly different structure. She bears have grooves on their tymbar sclerites, which allow them to generate clicks at a high frequency. A series of clicks are generated during both active inward bending of the thymbal sclerite (active cycle) and passive return of the sclerite (passive cycle, Fig. 2). Average interval between clicks B. trigona, equal to 325 µs, turns out to be less than the resolution of the ear of a bat (400 µs), so the entire series of clicks is perceived by the mouse as a continuous sound. On fig. 2 also shows that the frequency spectrum of the butterfly signal surprisingly mimics the spectrum of the bat signal.
In behavioral experiments, the authors observed three types of behavior in bats. First, a direct attack, when the mouse flew up and tried to grab the butterfly (Fig. 3A); second, a close-range attack where the mouse did not try to grab the butterfly but continued to attack after the butterfly started clicking (Fig. 3B); third, avoidance, when the mouse stopped attacking shortly after the butterfly started clicking and also did not try to grab it (Fig. 3C). The three types of behavior differed in the magnitude of the angle φ (Fig. 3D–F). In the case of a direct attack, the values of φ did not exceed the confidence interval of control attacks. In a close-range attack, the values of φ decreased or remained constant after the start of the butterfly clicking, but at the end there was a strong jump that exceeded the confidence interval. In avoidance, the φ values began to increase immediately after the moth started to click.
Mouse echolocation signals also differed in all three cases (Fig. 3G–I). In the case of a direct attack, the signal ended with a typical trill, which was always present in attacks on the control butterfly (Fig. 3G, 4A). The interval between mouse clicks was on average 6 ms. The close-range attack was dominated by normal clicks following at intervals of 10–40 ms, which are usually emitted by mice in search behavior. If a trill was produced, it was very short (Fig. 3H, 4B). In avoidance, the mouse began making occasional clicks shortly after the moth started clicking and did not trill at all (Fig. 4C).
The experience of the bat in the experiments was of great importance. Avoidance behavior dominated during the first two nights (Fig. 5), while close range attacks dominated from nights 3 to 7. This suggests that at first the mice were afraid of clicking butterflies, but then they got used to it. However, only 30% of the attacks ended successfully, and the attacks were successful only in cases where the butterflies clicked little. This confirms the assumption made by the authors that butterfly clicks are effective for jamming mouse signals only if they are generated at a high frequency. In close-range attacks, the mouse missed by an average of 16 cm.
These results, according to the authors, are consistent with the predictions of the remote interference hypothesis. The low percentage of avoidance within 3–7 nights suggests that mice do not try to avoid illusory interference. The approach of the mouse to the butterfly at a relatively short distance and attempts to attack show that the butterfly is not completely camouflaged, and therefore, the camouflage hypothesis can also be rejected.
It is known that when a bat approaches its prey, the intervals between clicks, the duration and intensity of the signal decrease. These changes in mouse signaling are extremely adaptive. The high click rate allows the mouse to update its "location information" quickly, while the short signal duration prevents the signal from overlapping with the echo, which begins to arrive faster as it gets closer to the victim. In experiments with B. trigona the authors observed the opposite situation: the duration of the signals and the intervals between clicks E. fuscus increased. This reaction of the mouse should make it even more difficult to find a potential victim. The authors compare this behavior with that of other mammals, which change their signal in the same way under high noise conditions. It is shown that in this case signal recognition is improved.
It is believed that she-bears originally generated rare clicks to disperse chemicals to warn them of their inedibility. Obviously, the evolution of acoustic signaling in butterflies followed the path of improving the sound organs, in particular, the development of grooves on the timbal membrane and the successive activation of tymbals, which allowed them to generate clicks at a high frequency. As a result, some species (and the authors believe that B. trigona- not the only species of butterfly that can jam the signals of bats) have developed such a wonderful way to protect themselves from a fairly sophisticated predator.
Bats usually live in huge flocks in caves, in which they
navigate in total darkness. Flying in and out of the cave, each mouse emits
sounds we can't hear. At the same time, thousands of mice make these sounds, but this is by no means
prevents them from perfectly navigating in space in complete darkness and flying without
colliding with each other. Why bats can confidently fly at full speed
darkness without bumping into obstacles? The amazing property of these nocturnal animals -
the ability to navigate in space without the help of vision is associated with their ability
emit and receive ultrasonic waves.
It turned out that during the flight, the mouse emits short signals at a frequency of about 80
kHz, and then receives the reflected echoes that come to it from the nearest
obstacles and from flying insects.
In order for the signal to be reflected by an obstacle, the smallest linear dimension
this obstacle should be no less than the wavelength of the sound being sent.
The use of ultrasound makes it possible to detect objects smaller than
could be detected using lower audio frequencies. Besides,
the use of ultrasonic signals is due to the fact that with a decrease in the wavelength
the directivity of the radiation is easier to realize, and this is very important for echolocation.
The mouse begins to react to a particular object at a distance of about 1 meter,
while the duration of the ultrasonic signals sent by the mouse decreases
about 10 times, and their repetition rate increases to 100–200 pulses
(clicks) per second. That is, having noticed the object, the mouse starts clicking more often, and
the clicks themselves become shorter. The smallest distance a mouse can
determined in this way is approximately 5 cm.
While approaching the object of hunting, the bat, as it were, estimates the angle between
direction of its speed and direction to the source of the reflected signal and
changes the direction of flight so that this angle becomes smaller and smaller.
Can a bat, sending a signal at a frequency of 80 kHz, detect a midge the size of
1 mm? The speed of sound in air is assumed to be 320 m/s. Explain the answer.
Ultrasonic echolocation of mice uses waves with a frequency
1) less than 20 Hz 3) more than 20 kHz
2) 20 Hz to 20 kHz 4) any frequency
The ability to perfectly navigate in space is associated in bats with their
Dolphin Hearing
Dolphins have an amazing ability to navigate the depths of the sea. This ability is due to the fact that dolphins can emit and receive signals of ultrasonic frequencies, mainly from 80 kHz to 100 kHz. At the same time, the signal strength is sufficient to detect a school of fish at a distance of up to a kilometer. The signals sent by the dolphin are a sequence of short pulses with a duration of the order of 0.01–0.1 ms.
In order for the signal to be reflected by an obstacle, the linear size of this obstacle must be no less than the wavelength of the sound being sent. The use of ultrasound makes it possible to detect smaller objects than could be detected using lower sound frequencies. In addition, the use of ultrasonic signals is due to the fact that the ultrasonic wave has a sharp radiation directivity, which is very important for echolocation, and decays much more slowly when propagating in water.
The dolphin is also able to perceive very weak reflected audio signals. For example, he perfectly notices a small fish that appeared from the side at a distance of 50 m.
We can say that the dolphin has two types of hearing: it can send and receive ultrasonic signals in a forward direction, and it can perceive ordinary sounds coming from all directions.
To receive sharply directed ultrasonic signals, the dolphin has an elongated lower jaw, through which the echo signal waves arrive at the ear. And to receive sound waves of relatively low frequencies, from 1 kHz to 10 kHz, on the sides of the dolphin's head, where once the distant ancestors of dolphins living on land had ordinary ears, there are external auditory openings that are almost overgrown, but they let the sounds through wonderful.
Can a dolphin detect a small 15 cm fish on its side? Speed
sound in water is taken equal to 1500 m/s. Explain the answer.
The ability to perfectly navigate in space is associated with dolphins with their
ability to send and receive
1) only infrasonic waves 3) only ultrasonic waves
2) only sound waves 4) sound and ultrasonic waves
Dolphins use echolocation
1) only infrasonic waves 3) only ultrasonic waves
2) only sound waves 4) sound and ultrasonic waves
seismic waves
During an earthquake or a large explosion in the crust and thickness of the Earth, mechanical
waves called seismic. These waves propagate in the Earth and
can be recorded using special instruments - seismographs.
The action of a seismograph is based on the principle that a freely suspended load
During an earthquake, the pendulum remains practically motionless relative to the Earth. On the
The figure shows a diagram of a seismograph. The pendulum is suspended from the post, firmly
fixed in the ground, and connected to a pen that draws a continuous line on paper
belt of a uniformly rotating drum. In case of soil vibrations, a rack with a drum
also come into oscillatory motion, and a wave graph appears on paper
movement.
There are several types of seismic waves, of which for studying the internal
the structure of the Earth, the most important longitudinal wave P and transverse wave S.
A longitudinal wave is characterized by the fact that particle oscillations occur in the direction
wave propagation; these waves arise in solids, liquids, and gases.
Transverse mechanical waves do not propagate in liquids or gases.
The propagation velocity of a longitudinal wave is approximately 2 times higher than the velocity
transverse wave propagation and is several kilometers per second. When
waves P and S pass through a medium whose density and composition change, then the velocities
waves also change, which is manifested in the refraction of waves. In denser layers
Earth's wave speed increases. The nature of the refraction of seismic waves allows
explore the interior of the earth.
Which statement(s) is(are) true?
A. During an earthquake, the weight of the seismograph pendulum oscillates relative to
the surface of the earth.
B. A seismograph installed at some distance from the epicenter of an earthquake,
will first capture the P wave, and then the S wave.
seismic wave P is
1) mechanical longitudinal wave 3) radio wave
2) mechanical transverse wave 4) light wave
The figure shows graphs of the dependence of seismic wave velocities on the depth of immersion in the bowels of the Earth. Graph for which of the waves ( P or S) indicates that the core of the Earth is not in a solid state? Explain the answer.
Sound analysis
With the help of sets of acoustic resonators, it is possible to establish which tones are included in a given sound and what their amplitudes are. Such an establishment of the spectrum of a complex sound is called its harmonic analysis.
Previously, sound analysis was performed using resonators, which are hollow balls of various sizes with an open process inserted into the ear and a hole on the opposite side. It is essential for the analysis of sound that whenever the analyzed sound contains a tone whose frequency is equal to the frequency of the resonator, the latter begins to sound loud in this tone.
Such methods of analysis, however, are very inaccurate and laborious. At present, they have been superseded by much more advanced, accurate, and fast electroacoustic methods. Their essence boils down to the fact that the acoustic vibration is first converted into an electrical vibration with the same shape, and therefore having the same spectrum, and then this vibration is analyzed by electrical methods.
One of the essential results of harmonic analysis concerns the sounds of our speech. By timbre, we can recognize the voice of a person. But how do sound vibrations differ when the same person sings different vowels on the same note? In other words, what is the difference in these cases between periodic air vibrations caused by the vocal apparatus at different positions of the lips and tongue and changes in the shape of the oral cavity and pharynx? Obviously, in the spectra of vowels there must be some features characteristic of each vowel sound, in addition to those features that create the timbre of the voice of a given person. The harmonic analysis of vowels confirms this assumption, namely: vowel sounds are characterized by the presence in their spectra of overtone regions with large amplitude, and these regions always lie for each vowel at the same frequencies, regardless of the height of the sung vowel sound.
Is it possible, using the spectrum of sound vibrations, to distinguish one vowel from another? Explain the answer.
The harmonic analysis of sound is called
A. establishing the number of tones that make up a complex sound.
B. establishing the frequencies and amplitudes of tones that make up a complex sound.
1) only A 2) only B 3) both A and B 4) neither A nor B
What physical phenomenon underlies the electroacoustic method of sound analysis?
1) conversion of electrical vibrations into sound
2) decomposition of sound vibrations into a spectrum
3) resonance
4) conversion of sound vibrations into electrical
Tsunami
Tsunami is one of the most powerful natural phenomena - a series of sea waves up to 200 km long, capable of crossing the entire ocean at speeds up to 900 km / h. Earthquakes are the most common cause of tsunamis.
The amplitude of the tsunami, and hence its energy, depends on the strength of the tremors, on how close the epicenter of the earthquake is to the bottom surface, and on the depth of the ocean in the area. The wavelength of a tsunami is determined by the area and topography of the ocean floor where the earthquake occurred.
In the ocean, tsunami waves do not exceed 60 cm in height - they are even difficult to determine from a ship or aircraft. But their length is almost always much greater than the depth of the ocean in which they spread.
All tsunamis are characterized by a large amount of energy that they carry, even in comparison with the most powerful waves generated by the action of the wind.
The whole life of a tsunami wave can be divided into four successive stages:
1) the origin of the wave;
2) movement across the expanses of the ocean;
3) interaction of the wave with the coastal zone;
4) collapse of the wave crest on the coastal zone.
To understand the nature of a tsunami, consider a ball floating on water. When a ridge passes under it, it rushes forward with it, but immediately slips off it, lags behind and, falling into a hollow, moves back until the next ridge picks it up. Then everything repeats, but not completely: each time the object moves forward a little. As a result, the ball describes a trajectory close to a circle in the vertical plane. Therefore, in a wave, a particle of the water surface participates in two movements: it moves along a circle of a certain radius, decreasing with depth, and translationally in a horizontal direction.
Observations have shown that there is a dependence of the speed of wave propagation on the ratio of the wavelength and the depth of the reservoir.
If the length of the generated wave is less than the depth of the reservoir, then only the surface layer takes part in the wave motion.
With a wavelength of tens of kilometers for tsunami waves, all seas and oceans are “shallow”, and the entire mass of water, from the surface to the bottom, takes part in the wave movement. Friction on the bottom becomes significant. The lower layers (near-bottom) are strongly slowed down, not keeping up with the upper layers. The propagation speed of such waves is determined only by depth. The calculation gives a formula by which you can calculate the speed of waves in "shallow" water: υ = √gH
Tsunamis run at a speed that decreases with decreasing ocean depth. This means that their length must change as they approach the shore.
Also, when the near-bottom layers slow down, the amplitude of the waves increases, i.e. the potential energy of the wave increases. The fact is that a decrease in the wave speed leads to a decrease in the kinetic energy, and part of it is converted into potential energy. Another part of the decrease in kinetic energy is spent on overcoming the friction force and is converted into internal energy. Despite such losses, the destructive power of the tsunami remains enormous, which, unfortunately, we have to periodically observe in various regions of the Earth.
Why does the amplitude of waves increase when a tsunami approaches the coast?
1) the wave speed increases, the internal energy of the wave is partially converted into kinetic energy
2) the wave speed decreases, the internal energy of the wave is partially converted into potential energy
3) the wave speed decreases, the kinetic energy of the wave is partially converted into potential energy
4) the wave speed increases, the internal energy of the wave is partially converted into potential energy
The movements of water particles in a tsunami are
1) transverse vibrations
2) the sum of translational and rotational motion
3) longitudinal vibrations
4) only forward movement
What happens to the wavelength of a tsunami as it approaches the shore? Explain the answer.
Human hearing
The lowest tone perceived by a person with normal hearing has a frequency of about 20 Hz. The upper limit of auditory perception varies greatly from person to person. Age is of particular importance here. At the age of eighteen, with perfect hearing, you can hear sound up to 20 kHz, but on average, the limits of audibility for any age lie in the range of 18 - 16 kHz. With age, the sensitivity of the human ear to high-frequency sounds gradually decreases. The figure shows a graph of the dependence of the level of perception of sound on frequency for people of different ages.
The sensitivity of the ear to sound vibrations of different frequencies is not the same. It
especially sensitive to medium frequency fluctuations (in the region of 4000 Hz). As
decrease or increase in frequency relative to the average range of hearing acuity
gradually decreases.
The human ear not only distinguishes between sounds and their sources; both ears working together
able to accurately determine the direction of sound propagation. Because the
ears are located on opposite sides of the head, sound waves from the source
sound reach them not at the same time and act with different pressure. Due
even this insignificant difference in time and pressure, the brain quite accurately determines
direction of the sound source.
Perception of sounds of different loudness and frequency at the age of 20 and 60
There are two sources of sound waves:
BUT. Sound wave with a frequency of 100 Hz and a volume of 10 dB.
B. Sound wave with a frequency of 1 kHz and a volume of 20 dB.
Using the graph shown in the figure, determine the sound of which source
will be heard by the person.
1) only A 2) only B 3) both A and B 4) neither A nor B
What statements made on the basis of the graph (see figure) are true?
BUT. With age, the sensitivity of human hearing to high-frequency sounds
gradually falls.
B. Hearing is much more sensitive to sounds in the 4 kHz region than to sounds lower or
higher sounds.
1) only A 2) only B 3) both A and B 4) neither A nor B
Is it always possible to accurately determine the direction of sound propagation and