Light and sound - what is what? Interesting facts about sound Interesting facts about sound physics.
Sound is a calling and creative symbol. Many creation myths testify that the universe was created using sound. According to Hermes Trismegistus, sound was the first thing that disturbed the eternal silence, and therefore it was the cause of everything created in the world, preceding light, air and fire. In Hinduism, the sound Aum brought the cosmos into being.
The strength of sound is measured in units called bell, after Alexander Bell, the inventor of the telephone. However, in practice it turned out to be more convenient to use tenths of a bela, that is, decibels. The maximum threshold of sound intensity for a person is an intensity of 120 ... 130 decibels. The sound of such force causes pain in the ears.
The sound you hear when you "break" your joints is actually the sound of nitrogen gas bubbles bursting.
The first determination of the speed of sound propagation in air was made by the French physicist and philosopher Pierre Gassendi in the middle of the 17th century - it turned out to be 449 meters per second. The sound of a tiger's roar can be heard at a distance of 3 km.
An interesting fact: being deaf does not mean not hearing anything, and even more so does not mean not having an “ear of music”. The great composer Beethoven, for example, was generally deaf. He put the end of his reed to the piano, and pressed the other end to his teeth. And the sound went to his inner ear, which was healthy.
Thomas Edison considered his apparatus for recording and reproducing sound a toy unsuitable for serious practical use.
Loud music from headphones is very stressful on the nerves in the auditory system and in the brain. This fact leads to a deterioration in the ability to distinguish sounds, and the person himself does not even feel that his hearing health is deteriorating.
Grasshoppers make sound with their hind legs.
A rustle of leaves produces a noise of 30 decibels, loud speech 70 decibels, an orchestra 80 decibels, and a jet engine 120 to 140 decibels.
If you take a ticking wristwatch in your teeth and plug your ears, the ticking will turn into strong, heavy blows - it will become so much stronger.
Granite conducts sound ten times better than air.
Niagara Falls produces a noise comparable to that of a factory floor (90-100 decibels).
Loud snoring can reach the same sound level as a jackhammer. Hitting the eardrum in the ear, the sound vibrates it, and it repeats the vibrations of air waves.
A person is able to hear the sound, even if the eardrum under its influence has deviated to a distance equal to the radius of the nucleus of a hydrogen atom.
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All ideas of mankind about sound are obtained by observing the surrounding world, nature and conducting experiments. In ancient times, a primitive man, watching the leaves on a tree, saw how they sway from the wind and rustle, make a sound when they interact with each other. And if you knock on a tree with a stick, you get one sound, on another tree - a different one. 
Using stones, you can also get sounds, but different. Some sounds, such as the sound of a wave, were liked by primitive people, and some, such as thunder or the cry of an animal, were frightening. Now it is already difficult to reliably state how everything happened and how long it took to classify, but watching young children it is easy to track how the process of learning and mastering sounds takes place.
Sound and its perception is information transfer method. Any sound makes a person react. This happens imperceptibly for the person himself, if the sounds are familiar and constant. Some people, in order to increase attention, specifically concentrate on sound and analyze it, building logical chains and getting more information.
For a person, a quiet measured ringing sound is quite pleasant and comfortable, but a low buzz is alarming. High notes in a person's voice or in a song draw attention to themselves, but are not so pleasant to listen to. It has been scientifically determined that sound is measured in decibels, and arises from any movement of any objects, organisms and particles in airspace or any other medium. 
A person perceives, catches and hears some sounds, others - he cannot recognize and perceive, therefore he does not hear. This determines the range, that is, the area of human perception. This value is approximately in the middle of the scale of all the existing sounds known on the planet. Infrared sounds are considered the lowest, and ultrasounds are considered the highest. Conducting experiments with sound, humanity has identified unusual and interesting facts, namely:
- Some animals, such as dogs and geese, hear higher sounds than humans and respond to them. Therefore, they are considered the best guards.
- Sound is a reaction of exposure to air particles, which wave the applied force to the human auditory organs. In water, this process occurs faster and therefore sound is heard four times faster than in air.
- Calm human speech produces noise with a power of 60 decibels, a whisper - 30, and a loud song or scream - up to 80.
- Since childhood, everyone knows that if you bring a shell to your ear, you can hear the sound of the sea. In fact, we only hear the sound that the blood makes as it moves through our vessels, and the shell acts as a resonator, amplifying the sound.
- During a thunderstorm, you can easily calculate the distance to the epicenter of the elements if you calculate the time elapsed from the lightning flash to the nearest thunder and multiply by the speed of sound - 330 m/s. This value will not be accurate, but it will help to determine whether a thunderstorm is approaching or moving away.
- Sound therapy has recently been considered a very effective method of treatment. The use of nature sounds in a piece of music has a very calming effect on the body as a whole. Instruments that fully reproduce natural sounds include all bowed instruments, especially the cello, and wind instruments. The use of unnatural, artificial sounds, the clanging of metal, the noise of an approaching train, car, electronic processing is alien to the human body and makes you always stay in a tense state, increasing the overall tone of the body and adding adrenaline to the blood. But, a constant stay in this state adversely affects the body and the person quickly gets tired, becomes nervous and irritable. Classical music will help in this situation.
- The loudest of the plants is considered an ordinary cactus. In dry times, the plant begins to vibrate and make a sound at a very high frequency, knocking out water molecules from the soil. That is why the plant looks like a huge drum or like a huge pipe. It is impossible for a person to hear such a sound, but it is possible to fix it with instruments.
- Sound is always accompanied by a shock wave. Most often, a person feels high sounds precisely because of the shock wave, so there is a saying - I feel it with my skin. Indeed, it is the skin that feels the short-term impact of the shock wave, and the human brain defines it as sound. This happens in a fraction of milliseconds, so it is impossible to physically feel the impact. In some cases, the shock wave is so amplified by the sound that it harms the body, such as when struck with a saber or sword.
- The loudest sound, which was attributed to Guinness records, was received quite by accident, from the fall of a metal stand in a closed underground laboratory. The sound was heard at a distance of 161 km from the source.
- Sound and noise affect the human body as a whole. For example, getting used to the sounds of the city, being in the wild, many experience discomfort from unusual sounds. An interesting effect is also observed during flights on airplanes. Even the food seems less salty, more sweet, and the alcohol less strong.
The main function of sound waves - to propagate in any medium except vacuum, and fight off obstacles - is actively used by mankind as echolocation. A lot of devices for determining distance, density and even color are based on this principle. All animals to some extent use sound waves in the ultrasonic range, even fish. In bats, dolphins, butterflies, this phenomenon is simply vital and allows you to navigate in the world around you.
1. Their level is measured in decibels (dB). The maximum threshold for human hearing (when pain already sets in) is an intensity of 120–130 decibels. And death occurs at 200.
- Normal conversation is about 45–55 dB.
- Sounds in the office - 55-65 dB.
- Noises on the street - 70–80 dB.
- Motorcycle with silencer - from 85 dB.
- A jet aircraft emits a noise of 130 dB at launch.
- A rocket - from 145 dB.
2. Sound and noise are not the same thing. Although ordinary people think so. However, for specialists there is a big difference between these two terms. Sound is vibrations perceived by the sense organs of animals and humans. Noise is a random mixture of sounds.
3. Our voice in the recording is different because we hear "with the wrong ear." It sounds strange, but it's true. And the thing is that when we speak, we perceive our voice in two ways - through the external (auditory canal, eardrum and middle ear) and internal (through the tissues of the head, which amplify the low frequencies of the voice).
And while listening from the outside, only the outer channel is involved.
4. Some people can hear the sound of their eyeballs rolling. And also your breath. This is due to a defect in the inner ear, when its sensitivity is increased beyond the norm.
5. The sound of the sea, which we hear through the sea shell, really just the sound of blood flowing through our vessels. The same noise can be heard by putting an ordinary cup to your ear. Try it!
6. Deaf people can still hear. Just one example of this: the famous composer Beethoven was known to be deaf, but he could create great works. How? He listened...with his teeth! The composer put the end of the reed to the piano, and clamped the other end in his teeth - so the sound reached the inner ear, which the composer had absolutely healthy, unlike the outer ear.
7. Sound can turn into light. This phenomenon is called sonoluminescence. It occurs when a resonator is lowered into the water, which creates a spherical ultrasonic wave. In the rarefaction phase of the wave, due to very low pressure, a cavitation bubble appears, which grows for some time, and then quickly collapses in the compression phase. At this moment, blue light appears in the center of the bubble.
8. "A" is the most common sound in the world. It is found in all languages of our planet. And in total there are about 6.5-7 thousand of them in the world. Most people speak Chinese, Spanish, Hindi, English, Russian, Portuguese and Arabic.
9. It is considered normal when a person hears soft conversational speech. from a distance of at least 5–6 meters (if these are low tones). Or at 20 meters with elevated tones. If you have trouble hearing what they say from a distance of 2-3 meters, you should check with an audiologist.
10. We may not notice that we are losing our hearing. Because the process occurs, as a rule, not simultaneously, but gradually. Moreover, at first, the situation can still be corrected, but the person does not notice that “something is wrong” with him. And when an irreversible process sets in, nothing can be done.
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Sound is an integral part of the life of every person, animal and even technology. Many animals navigate in space precisely because of the sound waves that echo in space and return. Some scientists have even invented sound therapies that help people cope with various diseases. If a person did not have hearing, he would lose a lot. Mankind would not only miss Beethoven's sonatas, but would simply be poorly oriented, for example, when crossing the road, they did not hear a speeding car. Today we will tell you ten interesting facts about sound.
Why does a person hear the sound of a sea wave in a shell?
In fact, a person hears how blood flows in the vessels. Approximately such a sound can be heard by attaching an ordinary mug to your ear. 
A person hears his voice differently due to the unusual structure of the ear. When we speak, sound enters the cochlea in two ways: through the auditory canal (external perception) and through the tissues of the head (internal). The voice is slightly distorted in our perception. Others hear our voice as it is recorded on the audio recording. Deaf people can also hear
Beethoven is an example of how a deaf person can hear. The great composer used a small cane, which on one side touched the piano, and on the other was clamped in his teeth. In this way, the sound was delivered to the healthy inner ear. "Nightingale floors" used as an alarm
In Japan, people often used the unusual technology of building an alarm floor. Boards were nailed to the poles in the shape of the letter "V". This technology was called "nightingale floors". Under the pressure of the mass of man, the boards made a sound similar to the chirping of birds. The slower the person walked, the louder the sounds were made. "Whispering Wall" will reveal all your secrets
Barossa is a reservoir built in the 20th century, which is located near the small provincial town of Adelaide. The peculiarity of this place lies in the incredible acoustics. A person standing at one end of the wall will perfectly hear what the person at the other end is whispering. This unusual place was called the "Whispering Wall". Bats can fight off prey from their competitors with sound
The bat during the hunt constantly makes special sounds when it notices its prey. She begins to publish a whole series of calls to determine the exact location of the prey. Another mouse can knock down the exact coordinates, which also wants to enjoy a delicious lunch. It superimposes its sound waves on those emitted by a competitor. What special echo does the pyramid of Kukulkan emit?
Chichen Itza is a small Mayan city, which houses an amazing architectural structure - the pyramid of Kukulkan. If you stand in front of the steps that lead to the entrance of the pyramid, clap your hands, you can hear the “chirping” of the quetzal bird. It was this species that was revered by the Indians of Mesoamerica. Are you weak to repeat the barking of a dog?
Birds can recreate the sound of a chainsaw, a gunshot, and the screams of a crying baby. The lyrebird is an Australian bird with the most developed vocal cords of any bird. She can even imitate the barking of a dingo dog. Why does the human ear perceive sounds differently at night?
Have you noticed that some people can fall asleep during a party with loud music or watching an action movie? And some can't fall asleep because of a leaky faucet or typing on a keyboard. Scientists explain this anomaly by the work of the brain. When a person is at rest, the brain continues to function. Moreover, he has enough energy when the body is resting. At this moment, all senses are aggravated, especially hearing. And the way people hear sounds is because of the successive impulses that filter the sounds. The more frequent these impulses, the more soundly one sleeps, the less often the impulses, the worse. Headphones can be used as a microphone
Try plugging your headphones into the microphone jack. The design of the microphone and headphones is almost the same. Often headphones can be used as a microphone. Homemade phone from thread and matchboxes
Take 2 matchboxes (or any other boxes of suitable sizes: from powder, tooth powder, paper clips) and a thread several meters long (you can use the entire length of the school class). Pierce the bottom of the box with a needle and thread and tie a knot on the thread so that it did not jump out. Thus, both boxes will be connected with a thread. Two people participate in a telephone conversation: one speaks into the box, as if into a microphone, the other listens, putting the box to his ear. The thread during the conversation should be taut and should not touch any objects, including the fingers that hold the boxes. If you touch the thread with your finger, the conversation will immediately stop. Why?
Musical instruments.
If you take several empty identical bottles, line them up and fill them with water (the first with a small amount of water, the subsequent fill in increments, and the last fill to the top), you get a musical percussion instrument. By hitting the bottles with a spoon, we will make the water vibrate. Bottle sounds will vary in pitch.
We take a cardboard tube, insert into it, like a piston, a cork with a knitting needle stuck in and moving the piston, we blow into the edge of the tube. Flute sounds!
We take a box with non-creasing edges, put rubber bands on it (the tighter they wrap around the box, the better), and the harp is ready! Sorting through the rubber bands, like strings, we listen to the melody!
Another "musical" toy.
If you take a piece of corrugated plastic tube and spin it over your head, you will hear a musical sound. The higher the rotation speed, the higher the pitch of the sound. Experiment! I wonder what caused the appearance of sound in this case?
Do you know
An aircraft flying at supersonic speed outruns the sounds it creates. These sound waves merge into one shock wave. Reaching the surface of the earth, the shock wave knocks out glass, destroys buildings, and stuns.
The sound made by a blue whale is louder than the sound of a nearby heavy gun, or louder than the sound of a rocket launching.
When meteorites pass through the Earth's atmosphere, a shock wave is excited, the speed of which is a hundred times higher than the sound one, and a sharp sound appears, similar to the sound of tearing matter.
With a skillful blow with a whip, a powerful wave is formed along it, the propagation speed of which at the tip of the whip can reach enormous values! The result is a powerful shock sound wave, comparable to the sound of a gunshot.
Mysterious gallery of whispers
Lord Rayleigh was the first to explain the mystery of the whisper gallery located under the dome of London's St. Paul's Cathedral. Whispers are very audible in this large gallery. If, for example, your friend whispered something, turning to the wall, then you will hear him, no matter where you stand in the gallery.
Oddly enough, you hear him the better, the more “straight into the wall” he speaks and the closer he stands to it. Does this task come down to simply reflecting and focusing the sound? To investigate this, Rayleigh made a large model of the gallery. At one point of it, he placed a decoy - a whistle, which hunters lure birds, at the other - a sensitive flame that sensitively reacted to sound. When the sound waves from the whistle reached the flame, it began to flicker and thus served as an indicator of sound. You would probably draw the sound path as shown by the arrow in the picture. But, in order not to take this for granted, imagine that somewhere between the flame and the whistle, a narrow screen is placed against the wall of the gallery. If your assumption about the course of sound waves is correct, then when the whistle sounds, the flame should still flicker, since the screen, it would seem, is to the side! However, in reality, when Rayleigh installed this screen, the flame stopped flickering. Somehow, the screen blocked the sound. But how? After all, this is just a narrow screen and it seems to be located away from the sound path. The result provided Rayleigh with a clue to the secret of the whisper gallery.
Gallery of whispers (in section)
Rayleigh's model of the whisper gallery. The sound of the whistle makes the flame flicker.
If a thin screen is installed against the wall of the gallery model, the flame does not react to the sounds of whistles. Why? Continuously reflected from the walls of the dome, sound waves propagate in a narrow belt along the wall. If the observer stands inside this belt, he hears a whisper. Outside this belt, further from the wall, the whisper is not heard. Whispers are heard better than normal speech, as they are richer in high frequency sounds, and the “hearing zone” for high frequencies is wider. In this case, sound propagates as if in a cylindrical waveguide and its intensity decreases with distance much more slowly than when propagating in open space.
Noisy water pipes
Why do water pipes sometimes growl and groan when we turn on or turn off a faucet? Why doesn't this happen continuously? Where exactly does the sound originate: in the faucet, in the part of the pipe adjacent directly to the faucet, or in some bend of it somewhere farther away? Why does the noise only start at certain water flow rates? Finally, why can noise be eliminated by attaching a vertical tube closed at the other end, which contains air, to a water pipe? As the flow velocity increases, turbulence can occur at constrictions in the pipes, which leads to cavitation (the formation and bursting of bubbles). The vibrations of the bubbles are amplified by the pipes, as well as the walls, floors, ceilings to which the pipes are attached!. Sometimes noise can also be caused by periodic impacts of turbulent flow against obstacles (for example, restrictions) in the pipe.