How do wind instruments work? Strange and unusual musical instruments that you just want to play A tool from the noise of waves and wind

Sound is sound waves that cause vibrations of tiny particles of air, other gases, and liquid and solid media. Sound can only arise where there is a substance, no matter what state of aggregation it is in. In vacuum conditions, where there is no medium, sound does not propagate, because there are no particles that act as distributors of sound waves. For example, in space. Sound can be modified, altered, turning into other forms of energy. Thus, sound converted into radio waves or electrical energy can be transmitted over distances and recorded on information media.

Sound wave

The movements of objects and bodies almost always cause fluctuations in the environment. It doesn't matter whether it's water or air. During this process, the particles of the medium to which the vibrations of the body are transmitted also begin to vibrate. Sound waves arise. Moreover, movements are carried out in forward and backward directions, progressively replacing each other. Therefore, the sound wave is longitudinal. There is never any lateral movement up and down in it.

Characteristics of sound waves

Like any physical phenomenon, they have their own quantities, with the help of which properties can be described. The main characteristics of a sound wave are its frequency and amplitude. The first value shows how many waves are formed per second. The second determines the strength of the wave. Low-frequency sounds have low frequency values, and vice versa. The frequency of sound is measured in Hertz, and if it exceeds 20,000 Hz, then ultrasound occurs. There are plenty of examples of low-frequency and high-frequency sounds in nature and the world around us. The chirping of a nightingale, the rumble of thunder, the roar of a mountain river and others are all different sound frequencies. The amplitude of the wave directly depends on how loud the sound is. The volume, in turn, decreases with distance from the sound source. Accordingly, the further the wave is from the epicenter, the smaller the amplitude. In other words, the amplitude of a sound wave decreases with distance from the sound source.

Sound speed

This indicator of a sound wave is directly dependent on the nature of the medium in which it propagates. Both humidity and air temperature play a significant role here. In average weather conditions, the speed of sound is approximately 340 meters per second. In physics, there is such a thing as supersonic speed, which is always greater than the speed of sound. This is the speed at which sound waves travel when an aircraft moves. The plane moves at supersonic speed and even outruns the sound waves it creates. Due to the pressure gradually increasing behind the aircraft, a shock wave of sound is formed. The unit of measurement for this speed is interesting and few people know it. It's called Mach. Mach 1 is equal to the speed of sound. If a wave travels at Mach 2, then it travels twice as fast as the speed of sound.

Noises

There is constant noise in human daily life. The noise level is measured in decibels. The movement of cars, the wind, the rustling of leaves, the interweaving of people's voices and other sound noises are our daily companions. But the human auditory analyzer has the ability to get used to such noise. However, there are also phenomena that even the adaptive abilities of the human ear cannot cope with. For example, noise exceeding 120 dB can cause pain. The loudest animal is the blue whale. When it makes sounds, it can be heard over 800 kilometers away.

Echo

How does an echo occur? Everything is very simple here. A sound wave has the ability to be reflected from different surfaces: from water, from a rock, from walls in an empty room. This wave returns to us, so we hear secondary sound. It is not as clear as the original one because some of the energy in the sound wave is dissipated as it travels toward the obstacle.

Echolocation

Sound reflection is used for various practical purposes. For example, echolocation. It is based on the fact that with the help of ultrasonic waves it is possible to determine the distance to the object from which these waves are reflected. Calculations are made by measuring the time it takes for ultrasound to travel to a location and return. Many animals have the ability to echolocation. For example, bats and dolphins use it to search for food. Echolocation has found another application in medicine. During ultrasound examinations, a picture of a person’s internal organs is formed. The basis of this method is that ultrasound, entering a medium other than air, returns back, thus forming an image.

Sound waves in music

Why do musical instruments make certain sounds? Guitar strumming, piano strumming, low tones of drums and trumpets, the charming thin voice of a flute. All these and many other sounds arise due to air vibrations or, in other words, due to the appearance of sound waves. But why is the sound of musical instruments so diverse? It turns out that this depends on several factors. The first is the shape of the tool, the second is the material from which it is made.

Let's look at this using string instruments as an example. They become a source of sound when the strings are touched. As a result, they begin to vibrate and send different sounds into the environment. The low sound of any stringed instrument is due to the greater thickness and length of the string, as well as the weakness of its tension. And vice versa, the more tightly the string is stretched, the thinner and shorter it is, the higher the sound obtained as a result of playing.

Microphone action

It is based on the conversion of sound wave energy into electrical energy. In this case, the current strength and the nature of the sound are directly dependent. Inside any microphone there is a thin plate made of metal. When exposed to sound, it begins to perform oscillatory movements. The spiral to which the plate is connected also vibrates, resulting in an electric current. Why does he appear? This is because the microphone also has built-in magnets. When the spiral oscillates between its poles, an electric current is generated, which goes along the spiral and then to a sound column (loudspeaker) or to equipment for recording on an information medium (cassette, disk, computer). By the way, the microphone in the phone has a similar structure. But how do microphones work on landlines and mobile phones? The initial phase is the same for them - the sound of the human voice transmits its vibrations to the microphone plate, then everything follows the scenario described above: a spiral, which, when moving, closes two poles, a current is created. What's next? With a landline telephone, everything is more or less clear - just like in a microphone, the sound, converted into electric current, runs through the wires. But what about a cell phone or, for example, a walkie-talkie? In these cases, the sound is converted into radio wave energy and hits the satellite. That's all.

Resonance phenomenon

Sometimes conditions are created when the amplitude of vibrations of the physical body increases sharply. This occurs due to the convergence of the values ​​of the frequency of forced oscillations and the natural frequency of oscillations of the object (body). Resonance can be both beneficial and harmful. For example, to get a car out of a hole, it is started and pushed back and forth in order to cause resonance and give the car inertia. But there have also been cases of negative consequences of resonance. For example, in St. Petersburg, about a hundred years ago, a bridge collapsed under soldiers marching in unison.

Thanks to musical instruments, we can produce music - one of the most unique creations of man. From trumpet to piano and bass guitar, they have been used to create countless complex symphonies, rock ballads and popular songs.
However, this list contains some of the strangest and most bizarre musical instruments that exist on the planet. And, by the way, some of them are from the category of “does this even exist?”
So here are 25 truly strange musical instruments - in sound, design or, most often, both.

25. Vegetable Orchestra

Formed almost 20 years ago by a group of friends interested in instrumental music, the Vegetable Orchestra in Vienna has become one of the strangest instrumental groups on the planet.
The musicians make their instruments before each performance - entirely from vegetables such as carrots, eggplants, leeks - to create a completely unusual performance that the audience can only see and hear.

24. Music Box

Construction equipment is most often noisy and annoying with its rumble, in strong contrast to a small music box. But one massive music box has been created that combines both.
This nearly one-ton vibratory compactor has been redesigned to spin just like a classic music box. He can play one famous tune - “The Star-Spangled Banner” (US anthem).

23. Cat piano

I would like to hope that the cat piano never becomes a real invention. Published in a book highlighting strange and bizarre musical instruments, the "Katzenklavier" (also known as the cat piano or cat organ) is a musical instrument in which cats are seated in an octave according to the tone of their voice.
Their tails are extended towards the keyboard with nails. When the key is pressed, the nail presses painfully on the tail of one of the cats, which produces the desired sound.

22. 12-neck guitar

It was pretty cool when Led Zeppelin's Jimmy Page played a double-neck guitar on stage. I wonder what it would be like if he played that 12-neck guitar?

21. Zeusaphone

Imagine creating music from electrical arcs. Zeusophone does just that. Known as the “Singing Tesla Coil,” this unusual musical instrument produces sound by altering visible flashes of electricity, creating a futuristic-sounding electronic instrument.

20. Yaybahar

Yaybahar is one of the strangest musical instruments that came from the Middle East. This acoustic instrument has strings connected to coiled springs that are stuck into the center of the drum frames. When the strings are played, the vibrations echo throughout the room, like echoing in a cave or inside a metal sphere, creating a hypnotic sound.

19. Sea organ

There are two large sea organs in the world - one in Zadar (Croatia) and the other in San Francisco (USA). They both work in a similar way - with a series of pipes absorbing and amplifying the sound of the waves, making the sea and its vagaries the main performer. The sounds that the sea organ makes have been compared to the sound of water entering the ears and the didgeridoo.

18. Pupa (Chrysalis)

The dolly is one of the most beautiful instruments in this list of strange musical instruments. Modeled after the massive, round, stone Aztec calendar, the instrument's wheel rotates in a circle with strings taut, producing a sound similar to a perfectly tuned zither.

17. Janko Keyboard

Janko's keyboard looks like a long, irregular chessboard. Developed by Paul von Jankó, this alternative arrangement of piano keys allows pianists to play pieces of music that would be impossible to play on a standard keyboard.
Although the keyboard looks quite difficult to play, it produces the same number of sounds as a standard keyboard and is easier to learn to play because changing the key only requires the player to move their hands up or down, without having to change fingerings.

16. Symphony House

Most musical instruments are portable, and the Symphony House is definitely not one of them! In this case, the musical instrument is an entire house in Michigan with an area of ​​575 square meters.
From the opposite windows that allow the sounds of nearby coastal waves or the noise of the forest to penetrate, to the wind blowing through the long strings of a distinctive harp, the entire house resonates with sound.
The largest musical instrument in the house is two 12-meter horizontal beams made of anegri wood with strings stretched along them. When the strings are played, the entire room vibrates, giving the person the feeling of being inside a giant guitar or cello.

15. Theremin

Theremin is one of the very first electronic instruments, patented in 1928. Two metal antennas determine the position of the performer's hands, changing the frequency and volume, which are converted from electrical signals into sounds.

14. Uncello

More like the model of the universe proposed by Nicolaus Copernicus in the 16th century, the unzello is a combination of wood, pegs, strings and an amazing custom resonator. Instead of a traditional cello body that amplifies the sound, the unzello uses a round fishbowl to produce sounds as the bow is played across the strings.

13. Hydrolophone

The hydrolophone is a new age musical instrument created by Steve Mann that emphasizes the importance of water and serves the visually impaired as a sensory exploration device.
Essentially, it is a massive water organ that is played by plugging small holes with your fingers, from which water slowly flows, hydraulically creating the traditional organ sound.

12. Bikelophone

The Baiklophone was built in 1995 as part of a project to explore new sounds. Using a bicycle frame as a base, this musical instrument creates layered sounds using a loop recording system.
It is constructed with bass strings, wood, metal telephone bells and more. The sound it produces is truly incomparable because it produces a wide range of sounds from harmonious melodies to sci-fi intros.

11. Earth Harp

Somewhat similar to the Symphony House, the Earth Harp is the world's longest stringed instrument. A harp with stretched strings 300 meters long produces sounds similar to a cello. A musician wearing cotton gloves coated with violin rosin plucks the strings with his hands, creating an audible wave of compression.

10. Great Stalacpipe Organ

Nature is full of sounds that are pleasant to our ears. Combining human ingenuity and design with natural acoustics, Leland W. Sprinkle installed a custom lithophone in Luray Caverns, Virginia, USA.
The organ produces sounds of varying tones using tens of thousands of years old stalactites that have been converted into resonators.

9. Serpent

This bassy wind instrument, with a brass mouthpiece and finger holes similar to a woodwind, was so named because of its unusual design. The curving shape of the Snake allows it to produce a unique sound, reminiscent of a cross between a tuba and a trumpet.

8. Ice organ

The Swedish Ice Hotel, built entirely of ice in winter, is one of the most famous boutique hotels in the world. In 2004, American ice sculptor Tim Linhart accepted an offer to build a musical instrument that would fit the hotel's theme.
As a result, Linart created the world's first ice organ - an instrument with pipes entirely carved from ice. Unfortunately, the life of this unusual musical instrument was short-lived - it melted last winter.

7. Aeolus

Looking like an instrument modeled after Tina Turner's bad hairstyle, the aeolus is a huge arch with many pipes that catches every breath of wind and converts it into sound, often produced in the rather eerie tones associated with a UFO landing.

6. Nellophone

If the previous unusual musical instrument resembles Tina Turner's hair, then this one can be compared to the tentacles of a jellyfish. To play a nellophone, which is constructed entirely of curved pipes, the performer stands in the center and strikes the pipes with special paddles, thereby producing the sound of the air resonating within them.

5. Sharpsichord

One of the most complex and strange musical instruments on this list, the sharpsichord has 11,520 holes with pegs inserted into them and resembles a music box.
When the solar-powered cylinder turns, a lever rises to pluck the strings. The power is then transferred to the jumper, which amplifies the sound using a large horn.

4. Pyrophone Organ

This list covers many different types of repurposed organs, and this one might be the best of them all. Unlike using stalactites or ice, the pyrophonic organ produces sounds by creating mini-explosions with each keystroke.
Hitting the key of a propane and gasoline-powered pyrophonic organ provokes exhaust from the pipe, like a car engine, thereby creating sound.

3. Fence. Any fence.

Few people in the world can claim to be a “fence-playing musician.” In fact, only one person can do this - Australian Jon Rose (already sounds like the name of a rock star), creating music on fences.
Rose uses a violin bow to create resonant sounds on tightly strung "acoustic" fences, ranging from barbed wire to chain link fence. Some of his most provocative performances include playing on the border fence between Mexico and the United States, and between Syria and Israel.

2. Cheese Drums

A combination of two human passions - music and cheese - these cheese drums are a truly wonderful and very strange group of instruments.
Their creators took a traditional drum kit and replaced all the drums with massive round heads of cheese, placing a microphone next to each to produce more delicate sounds.
For most of us, their sound will be more like the drumsticks of an amateur drummer sitting in a local Vietnamese restaurant.

1. Loophonium

As a small tuba-like bass musical instrument that plays a leading role in brass and military bands, the euphonium is not such a strange instrument.
That is, until Fritz Spiegl of the Royal Liverpool Philharmonic Orchestra created the toiletphonium: a fully functioning combination of a euphonium and a beautifully painted toilet.

One of the main arguments against the use of wind generators is noise . Wind power plants produce two types of noise: mechanical and aerodynamic. The noise from modern wind generators at a distance of 20 m from the installation site is 34 - 45 dB. For comparison: background noise at night in a village is 20 - 40 dB, noise from a passenger car at a speed of 64 km/h is 55 dB, background noise in an office is 60 dB, noise from a truck at a speed of 48 km/h at a distance from it at 100m is 65 dB, the noise from a jackhammer at a distance of 7 m is 95 dB. Thus, wind generators are not a source of noise that has any negative impact on human health.
Infrasound and vibration - another issue of negative impact. During operation of the windmill, vortices are formed at the ends of the blades, which, in fact, are sources of infrasound; the greater the power of the windmill, the greater the vibration power and the negative impact on wildlife. The frequency of these vibrations - 6-7 Hz - coincides with the natural rhythm of the human brain, so some psychotropic effects are possible. But all this applies to powerful wind power plants (this has not even been proven in relation to them). Small wind energy in this aspect is much safer than railway transport, cars, trams and other sources of infrasound that we encounter every day.
Relatively vibrations , then they no longer threaten people, but buildings and structures; methods for reducing it are a well-studied issue. If a good aerodynamic profile is chosen for the blades, the wind turbine is well balanced, the generator is in working order, and technical inspection is carried out in a timely manner, then there is no problem at all. Except that additional shock absorption may be needed if the windmill is on the roof.
Opponents of wind generators also refer to the so-called visual impact . Visual impact is a subjective factor. To improve the aesthetic appearance of wind turbines, many large companies employ professional designers. Landscape designers are hired to justify new projects. Meanwhile, when conducting a public opinion poll, the question “Do wind turbines spoil the overall landscape?” 94% of respondents answered negatively, and many emphasized that from an aesthetic point of view, wind generators fit harmoniously into the environment, unlike traditional power lines.
Also, one of the arguments against the use of wind generators is harm to animals and birds . At the same time, statistics show that per 10,000 individuals, less than 1 die due to wind generators, 250 due to television towers, 700 due to pesticides, 700 due to various mechanisms, and 700 due to power lines. - 800 pcs., because of cats - 1000 pcs., because of houses/windows - 5500 pcs. Thus, wind generators are not the biggest evil for representatives of our fauna.
But in turn, a 1 MW wind generator reduces annual emissions into the atmosphere by 1800 tons of carbon dioxide, 9 tons of sulfur oxide, 4 tons of nitrogen oxide. Perhaps the transition to wind energy will influence the rate of decline of the ozone layer, and, accordingly, the rate of global warming.
In addition, wind turbines, unlike thermal power plants, produce electricity without using water, which reduces the use of water resources.
Wind generators produce electricity without burning traditional fuels, which reduces demand and fuel prices.
Analyzing the above, we can say with confidence that From an environmental point of view, wind generators are not harmful. The practical confirmation of this is thatThese technologies are gaining rapid development in the European Union, USA, China and other countries of the world. Modern wind energy today generates more than 200 billion kWh per year, equivalent to 1.3% of global electricity production. At the same time, in some countries this figure reaches 40%.

Have you ever thought that sound is one of the most striking manifestations of life, action, and movement? And also about the fact that each sound has its own “face”? And even with our eyes closed, without seeing anything, we can only guess by sound what is happening around us. We can distinguish the voices of friends, hear rustling, roaring, barking, meowing, etc. All these sounds are familiar to us from childhood, and we can easily identify any of them. Moreover, even in absolute silence we can hear each of the listed sounds with our inner hearing. Imagine it as if in reality.

What is sound?

Sounds perceived by the human ear are one of the most important sources of information about the world around us. The noise of the sea and wind, birdsong, human voices and animal cries, thunderclaps, sounds of moving ears, make it easier to adapt to changing external conditions.

If, for example, a stone fell in the mountains, and there was no one nearby who could hear the sound of its fall, did the sound exist or not? The question can be answered both positively and negatively in equal measure, since the word “sound” has a double meaning. Therefore, it is necessary to agree. Therefore, it is necessary to agree on what is considered sound - a physical phenomenon in the form of the propagation of sound vibrations in the air or the sensation of the listener. The first is essentially is a cause, the second is an effect, while the first concept of sound is objective, the second is subjective. In the first case, sound is really a stream of energy flowing like a river stream. Such a sound can change the medium through which it passes, and is itself changed by it ". In the second case, by sound we mean those sensations that arise in the listener when a sound wave acts on the brain through a hearing aid. Hearing sound, a person can experience various feelings. A wide variety of emotions are evoked in us by that complex complex of sounds that we call music. Sounds form the basis of speech, which serves as the main means of communication in human society.And finally, there is a form of sound called noise. Analysis of sound from the standpoint of subjective perception is more complex than with an objective assessment.

How to create sound?

What all sounds have in common is that the bodies that generate them, i.e., the sources of sound, vibrate (although most often these vibrations are invisible to the eye). For example, the sounds of the voices of people and many animals arise as a result of vibrations of their vocal cords, the sound of wind musical instruments, the sound of a siren, the whistle of the wind, and the sound of thunder are caused by vibrations of air masses.

Using a ruler as an example, you can literally see with your own eyes how sound is born. What movement does the ruler make when we fasten one end, pull the other and release it? We will notice that he seemed to tremble and hesitate. Based on this, we conclude that sound is created by short or long vibrations of some objects.

The source of sound can be not only vibrating objects. The whistling of bullets or shells in flight, the howling of the wind, the roar of a jet engine are born from breaks in the air flow, during which rarefaction and compression also occur.

Also, sound vibrational movements can be noticed using a device - a tuning fork. It is a curved metal rod mounted on a leg on a resonator box. If you hit a tuning fork with a hammer, it will sound. The vibrations of the tuning fork branches are imperceptible. But they can be detected if you bring a small ball suspended on a thread to a sounding tuning fork. The ball will periodically bounce, which indicates vibrations of the Cameron branches.

As a result of the interaction of the sound source with the surrounding air, air particles begin to compress and expand in time (or “almost in time”) with the movements of the sound source. Then, due to the properties of air as a fluid medium, vibrations are transferred from one air particle to another.

Towards an explanation of the propagation of sound waves

As a result, vibrations are transmitted through the air over a distance, i.e., a sound or acoustic wave, or, simply, sound, propagates through the air. Sound, reaching the human ear, in turn, excites vibrations in its sensitive areas, which are perceived by us in the form of speech, music, noise, etc. (depending on the properties of the sound dictated by the nature of its source).

Propagation of sound waves

Is it possible to see how the sound “runs”? In transparent air or water, the vibrations of particles themselves are imperceptible. But you can easily find an example that will tell you what happens when sound propagates.

A necessary condition for the propagation of sound waves is the presence of a material medium.

In a vacuum, sound waves do not propagate, since there are no particles there that transmit the interaction from the source of vibration.

Therefore, due to the lack of atmosphere, complete silence reigns on the Moon. Even the fall of a meteorite on its surface is not audible to the observer.

The speed of propagation of sound waves is determined by the speed of transmission of interactions between particles.

The speed of sound is the speed of propagation of sound waves in a medium. In a gas, the speed of sound turns out to be of the order of (more precisely, somewhat less than) the thermal speed of molecules and therefore increases with increasing gas temperature. The greater the potential energy of interaction between the molecules of a substance, the greater the speed of sound, therefore the speed of sound in a liquid, which, in turn, exceeds the speed of sound in a gas. For example, in sea water the speed of sound is 1513 m/s. In steel, where transverse and longitudinal waves can propagate, their speed of propagation is different. Transverse waves propagate at a speed of 3300 m/s, and longitudinal waves at a speed of 6600 m/s.

The speed of sound in any medium is calculated by the formula:

where β is the adiabatic compressibility of the medium; ρ - density.

Laws of propagation of sound waves

The basic laws of sound propagation include the laws of its reflection and refraction at the boundaries of various media, as well as the diffraction of sound and its scattering in the presence of obstacles and inhomogeneities in the medium and at the interfaces between media.

The range of sound propagation is influenced by the sound absorption factor, that is, the irreversible transition of sound wave energy into other types of energy, in particular heat. An important factor is also the direction of radiation and the speed of sound propagation, which depends on the medium and its specific state.

From a sound source, acoustic waves propagate in all directions. If a sound wave passes through a relatively small hole, then it spreads in all directions, and does not travel in a directed beam. For example, street sounds penetrating through an open window into a room are heard at all points, and not just opposite the window.

The nature of the propagation of sound waves near an obstacle depends on the relationship between the size of the obstacle and the wavelength. If the size of the obstacle is small compared to the wavelength, then the wave flows around this obstacle, spreading in all directions.

Sound waves, penetrating from one medium to another, deviate from their original direction, that is, they are refracted. The angle of refraction may be greater or less than the angle of incidence. It depends on what medium the sound penetrates into. If the speed of sound in the second medium is greater, then the angle of refraction will be greater than the angle of incidence, and vice versa.

When meeting an obstacle on their way, sound waves are reflected from it according to a strictly defined rule - the angle of reflection is equal to the angle of incidence - the concept of echo is connected with this. If sound is reflected from several surfaces at different distances, multiple echoes occur.

Sound travels in the form of a diverging spherical wave that fills an increasingly larger volume. As the distance increases, the vibrations of the particles of the medium weaken and the sound dissipates. It is known that to increase the transmission range, sound must be concentrated in a given direction. When we want, for example, to be heard, we put our palms to our mouths or use a megaphone.

Diffraction, that is, the bending of sound rays, has a great influence on the range of sound propagation. The more heterogeneous the medium, the more the sound beam is bent and, accordingly, the shorter the sound propagation range.

Properties of sound and its characteristics

The main physical characteristics of sound are the frequency and intensity of vibrations. They influence people's auditory perception.

The period of oscillation is the time during which one complete oscillation occurs. An example can be given of a swinging pendulum, when it moves from the extreme left position to the extreme right and returns back to its original position.

Oscillation frequency is the number of complete oscillations (periods) per second. This unit is called the hertz (Hz). The higher the vibration frequency, the higher the sound we hear, that is, the sound has a higher pitch. According to the accepted international system of units, 1000 Hz is called a kilohertz (kHz), and 1,000,000 is called a megahertz (MHz).

Frequency distribution: audible sounds – within 15Hz-20kHz, infrasounds – below 15Hz; ultrasounds - within 1.5 (104 - 109 Hz; hypersound - within 109 - 1013 Hz.

The human ear is most sensitive to sounds with frequencies between 2000 and 5000 kHz. The greatest hearing acuity is observed at the age of 15-20 years. With age, hearing deteriorates.

The concept of wavelength is associated with the period and frequency of oscillations. The sound wavelength is the distance between two successive condensations or rarefactions of the medium. Using the example of waves propagating on the surface of water, this is the distance between two crests.

Sounds also differ in timbre. The main tone of the sound is accompanied by secondary tones, which are always higher in frequency (overtones). Timbre is a qualitative characteristic of sound. The more overtones are superimposed on the main tone, the “juicier” the sound is musically.

The second main characteristic is the amplitude of oscillations. This is the largest deviation from the equilibrium position during harmonic vibrations. Using the example of a pendulum, its maximum deviation is to the extreme left position, or to the extreme right position. The amplitude of the vibrations determines the intensity (strength) of the sound.

The strength of sound, or its intensity, is determined by the amount of acoustic energy flowing in one second through an area of ​​one square centimeter. Consequently, the intensity of acoustic waves depends on the magnitude of the acoustic pressure created by the source in the medium.

Loudness is in turn related to the intensity of sound. The greater the intensity of the sound, the louder it is. However, these concepts are not equivalent. Loudness is a measure of the strength of the auditory sensation caused by a sound. A sound of the same intensity can create auditory perceptions of different loudness in different people. Each person has his own hearing threshold.

A person stops hearing sounds of very high intensity and perceives them as a feeling of pressure and even pain. This sound intensity is called the pain threshold.

The effect of sound on the human hearing organs

The human hearing organs are capable of perceiving vibrations with a frequency from 15-20 hertz to 16-20 thousand hertz. Mechanical vibrations with the indicated frequencies are called sound or acoustic (acoustics is the study of sound). The human ear is most sensitive to sounds with a frequency of 1000 to 3000 Hz. The greatest hearing acuity is observed at the age of 15-20 years. With age, hearing deteriorates. In a person under 40 years of age, the greatest sensitivity is in the region of 3000 Hz, from 40 to 60 years old - 2000 Hz, over 60 years old - 1000 Hz. In the range of up to 500 Hz, we are able to distinguish a decrease or increase in frequency of even 1 Hz. At higher frequencies, our hearing aids become less sensitive to such small changes in frequency. So, after 2000 Hz we can distinguish one sound from another only when the difference in frequency is at least 5 Hz. With a smaller difference, the sounds will seem the same to us. However, there are almost no rules without exceptions. There are people who have unusually fine hearing. A gifted musician can detect a change in sound by just a fraction of a vibration.

The outer ear consists of the pinna and the auditory canal, which connect it to the eardrum. The main function of the outer ear is to determine the direction of the sound source. The auditory canal, which is a two-centimeter long tube tapering inwards, protects the inner parts of the ear and plays the role of a resonator. The auditory canal ends with the eardrum, a membrane that vibrates under the influence of sound waves. It is here, on the outer border of the middle ear, that the transformation of objective sound into subjective occurs. Behind the eardrum there are three small interconnected bones: the malleus, the incus and the stirrup, through which vibrations are transmitted to the inner ear.

There, in the auditory nerve, they are converted into electrical signals. The small cavity, where the malleus, incus and stapes are located, is filled with air and connected to the oral cavity by the Eustachian tube. Thanks to the latter, equal pressure is maintained on the inner and outer sides of the eardrum. Usually the Eustachian tube is closed, and opens only when there is a sudden change in pressure (yawning, swallowing) to equalize it. If a person’s Eustachian tube is closed, for example due to a cold, then the pressure is not equalized and the person feels pain in the ears. Next, the vibrations are transmitted from the eardrum to the oval window, which is the beginning of the inner ear. The force acting on the eardrum is equal to the product of pressure and the area of ​​the eardrum. But the real mysteries of hearing begin with the oval window. Sound waves travel through the fluid (perilymph) that fills the cochlea. This organ of the inner ear, shaped like a cochlea, is three centimeters long and is divided along its entire length by a septum into two parts. Sound waves reach the partition, go around it and then spread towards almost the same place where they first touched the partition, but on the other side. The septum of the cochlea consists of a main membrane, which is very thick and tight. Sound vibrations create wave-like ripples on its surface, with ridges for different frequencies lying in very specific areas of the membrane. Mechanical vibrations are converted into electrical ones in a special organ (organ of Corti), located above the upper part of the main membrane. Above the organ of Corti is the tectorial membrane. Both of these organs are immersed in a fluid called endolymph and are separated from the rest of the cochlea by Reissner's membrane. The hairs growing from the organ of Corti almost penetrate the tectorial membrane, and when sound occurs they come into contact - the sound is converted, now it is encoded in the form of electrical signals. The skin and bones of the skull play a significant role in enhancing our ability to perceive sounds, due to their good conductivity. For example, if you put your ear to the rail, the movement of an approaching train can be detected long before it appears.

The effect of sound on the human body

Over the past decades, the number of various types of cars and other sources of noise, the spread of portable radios and tape recorders, often turned on at high volume, and the passion for loud popular music have increased sharply. It has been noted that in cities every 5-10 years the noise level increases by 5 dB (decibels). It should be borne in mind that for distant human ancestors, noise was an alarm signal, indicating the possibility of danger. At the same time, the sympathetic-adrenal and cardiovascular systems, gas exchange were quickly activated, and other types of metabolism changed (blood sugar and cholesterol levels increased), preparing the body for fight or flight. Although in modern man this function of hearing has lost such practical significance, the “vegetative reactions of the struggle for existence” have been preserved. Thus, even short-term noise of 60-90 dB causes an increase in the secretion of pituitary hormones, stimulating the production of many other hormones, in particular catecholamines (adrenaline and norepinephrine), the work of the heart increases, blood vessels constrict, and blood pressure (BP) increases. It was noted that the most pronounced increase in blood pressure is observed in patients with hypertension and people with a hereditary predisposition to it. Under the influence of noise, brain activity is disrupted: the nature of the electroencephalogram changes, the acuity of perception and mental performance decrease. Deterioration of digestion was noted. It is known that prolonged exposure to noisy environments leads to hearing loss. Depending on individual sensitivity, people evaluate noise differently as unpleasant and disturbing. At the same time, music and speech that interests the listener, even at 40-80 dB, can be tolerated relatively easily. Typically, hearing perceives vibrations in the range of 16-20,000 Hz (oscillations per second). It is important to emphasize that unpleasant consequences are caused not only by excessive noise in the audible range of vibrations: ultra- and infrasound in ranges not perceived by human hearing (above 20 thousand Hz and below 16 Hz) also causes nervous tension, malaise, dizziness, changes in the activity of internal organs, especially the nervous and cardiovascular systems. It has been found that residents of areas located near major international airports have a distinctly higher incidence of hypertension than those living in a quieter area of ​​the same city. Excessive noise (above 80 dB) affects not only the hearing organs, but also other organs and systems (circulatory, digestive, nervous, etc.). etc.), vital processes are disrupted, energy metabolism begins to prevail over plastic metabolism, which leads to premature aging of the body.

With these observations and discoveries, methods of targeted influence on humans began to appear. You can influence the mind and behavior of a person in various ways, one of which requires special equipment (technotronic techniques, zombification.).

Soundproofing

The degree of noise protection of buildings is primarily determined by the permissible noise standards for premises for a given purpose. The normalized parameters of constant noise at design points are sound pressure levels L, dB, octave frequency bands with geometric mean frequencies 63, 125, 250, 500, 1000, 2000, 4000, 8000 Hz. For approximate calculations, it is allowed to use sound levels LA, dBA. The normalized parameters of non-constant noise at design points are equivalent sound levels LA eq, dBA, and maximum sound levels LA max, dBA.

Permissible sound pressure levels (equivalent sound pressure levels) are standardized by SNiP II-12-77 “Noise Protection”.

It should be taken into account that permissible noise levels from external sources in premises are established subject to the provision of standard ventilation of premises (for residential premises, wards, classrooms - with open vents, transoms, narrow window sashes).

Airborne sound insulation is the attenuation of sound energy as it is transmitted through an enclosure.

The regulated parameters of sound insulation of enclosing structures of residential and public buildings, as well as auxiliary buildings and premises of industrial enterprises are the airborne noise insulation index of the enclosing structure Rw, dB and the index of the reduced impact noise level under the ceiling.

Noise. Music. Speech.

From the point of view of the hearing organs' perception of sounds, they can be divided mainly into three categories: noise, music and speech. These are different areas of sound phenomena that have information specific to a person.

Noise is an unsystematic combination of a large number of sounds, that is, the merging of all these sounds into one discordant voice. Noise is considered to be a category of sounds that disturbs or annoys a person.

People can only tolerate a certain amount of noise. But if an hour or two passes and the noise does not stop, then tension, nervousness and even pain appear.

Sound can kill a person. In the Middle Ages, there was even such an execution when a person was put under a bell and they began to beat it. Gradually the ringing of the bells killed the man. But this was in the Middle Ages. Nowadays, supersonic aircraft have appeared. If such a plane flies over the city at an altitude of 1000-1500 meters, then the windows in the houses will burst.

Music is a special phenomenon in the world of sounds, but, unlike speech, it does not convey precise semantic or linguistic meanings. Emotional saturation and pleasant musical associations begin in early childhood, when the child still has verbal communication. Rhythms and chants connect him with his mother, and singing and dancing are an element of communication in games. The role of music in human life is so great that in recent years medicine has attributed healing properties to it. With the help of music, you can normalize biorhythms and ensure an optimal level of activity of the cardiovascular system. But you just have to remember how soldiers go into battle. From time immemorial, the song was an indispensable attribute of a soldier's march.

Infrasound and ultrasound

Can we call something that we cannot hear at all sound? So what if we don't hear? Are these sounds inaccessible to anyone or anything else?

For example, sounds with a frequency below 16 hertz are called infrasound.

Infrasound is elastic vibrations and waves with frequencies lying below the range of frequencies audible to humans. Typically, 15-4 Hz is taken as the upper limit of the infrasound range; This definition is conditional, since with sufficient intensity, auditory perception also occurs at frequencies of a few Hz, although the tonal nature of the sensation disappears and only individual cycles of oscillations become distinguishable. The lower frequency limit of infrasound is uncertain. Its current area of ​​study extends down to about 0.001 Hz. Thus, the range of infrasound frequencies covers about 15 octaves.

Infrasound waves propagate in air and water, as well as in the earth's crust. Infrasounds also include low-frequency vibrations of large structures, in particular vehicles and buildings.

And although our ears do not “catch” such vibrations, somehow a person still perceives them. At the same time, we experience unpleasant and sometimes disturbing sensations.

It has long been noticed that some animals experience a sense of danger much earlier than humans. They react in advance to a distant hurricane or an impending earthquake. On the other hand, scientists have discovered that during catastrophic events in nature, infrasound occurs - low-frequency air vibrations. This gave rise to hypotheses that animals, thanks to their keen sense of smell, perceive such signals earlier than humans.

Unfortunately, infrasound is generated by many machines and industrial installations. If, say, it occurs in a car or airplane, then after some time the pilots or drivers become anxious, they get tired faster, and this can be the cause of an accident.

Infrasonic machines make noise, and then it’s harder to work on them. And everyone around will have a hard time. It’s no better if the ventilation in a residential building “buzzes” with infrasound. It seems to be inaudible, but people get irritated and may even get sick. A special “test” that any device must pass allows you to get rid of infrasound adversities. If it “phonates” in the infrasound zone, it will not receive access to people.

What is a very high sound called? Such a squeak that is inaccessible to our ears? This is ultrasound. Ultrasound is elastic waves with frequencies from approximately (1.5 – 2)(104 Hz (15 – 20 kHz) to 109 Hz (1 GHz); the region of frequency waves from 109 to 1012 – 1013 Hz is usually called hypersound. Based on frequency, ultrasound is conveniently divided into 3 ranges: low-frequency ultrasound (1.5 (104 - 105 Hz), mid-frequency ultrasound (105 - 107 Hz), high-frequency ultrasound (107 - 109 Hz). Each of these ranges is characterized by its own specific characteristics of generation, reception, propagation and application .

By its physical nature, ultrasound is elastic waves, and in this it is no different from sound, therefore the frequency boundary between sound and ultrasonic waves is arbitrary. However, due to higher frequencies and, therefore, short wavelengths, a number of features of ultrasound propagation occur.

Due to the short wavelength of ultrasound, its nature is determined primarily by the molecular structure of the medium. Ultrasound in gas, and in particular in air, propagates with high attenuation. Liquids and solids are, as a rule, good conductors of ultrasound; the attenuation in them is much less.

The human ear is not capable of perceiving ultrasonic signals. However, many animals accept it freely. These are, among other things, dogs that are so familiar to us. But, alas, dogs cannot “bark” with ultrasound. But bats and dolphins have the amazing ability to both emit and receive ultrasound.

Hypersound is elastic waves with frequencies from 109 to 1012 – 1013 Hz. By its physical nature, hypersound is no different from sound and ultrasonic waves. Due to higher frequencies and, therefore, shorter wavelengths than in the field of ultrasound, the interactions of hypersound with quasiparticles in the medium - with conduction electrons, thermal phonons, etc. - become much more significant. Hypersound is also often represented as a flow of quasiparticles - phonons.

The frequency range of hypersound corresponds to the frequencies of electromagnetic oscillations in the decimeter, centimeter and millimeter ranges (the so-called ultrahigh frequencies). The frequency of 109 Hz in air at normal atmospheric pressure and room temperature should be of the same order of magnitude as the free path of molecules in air under the same conditions. However, elastic waves can propagate in a medium only if their wavelength is noticeably greater than the free path of particles in gases or greater than the interatomic distances in liquids and solids. Therefore, hypersonic waves cannot propagate in gases (in particular in air) at normal atmospheric pressure. In liquids, the attenuation of hypersound is very high and the propagation range is short. Hypersound propagates relatively well in solids - single crystals, especially at low temperatures. But even in such conditions, hypersound is capable of traveling a distance of only 1, maximum 15 centimeters.

Sound is mechanical vibrations propagating in elastic media - gases, liquids and solids, perceived by the organs of hearing.

Using special instruments, you can see the propagation of sound waves.

Sound waves can harm human health and, conversely, help cure ailments, it depends on the type of sound.

It turns out that there are sounds that are not perceived by the human ear.

Bibliography

Peryshkin A. V., Gutnik E. M. Physics 9th grade

Kasyanov V. A. Physics 10th grade

Leonov A. A “I explore the world” Det. encyclopedia. Physics

Chapter 2. Acoustic noise and its impact on humans

Purpose: To study the effects of acoustic noise on the human body.

Introduction

The world around us is a wonderful world of sounds. The voices of people and animals, music and the sound of the wind, and the singing of birds are heard around us. People transmit information through speech and perceive it through hearing. For animals, sound is no less important, and in some ways even more important, because their hearing is more acutely developed.

From the point of view of physics, sound is mechanical vibrations that propagate in an elastic medium: water, air, solids, etc. A person’s ability to perceive sound vibrations and listen to them is reflected in the name of the study of sound - acoustics (from the Greek akustikos - audible, auditory). The sensation of sound in our hearing organs occurs due to periodic changes in air pressure. Sound waves with a large amplitude of sound pressure changes are perceived by the human ear as loud sounds, and with a small amplitude of sound pressure changes - as quiet sounds. The volume of the sound depends on the amplitude of the vibrations. The volume of the sound also depends on its duration and on the individual characteristics of the listener.

High frequency sound vibrations are called high pitch sounds, low frequency sound vibrations are called low pitch sounds.

The human hearing organs are capable of perceiving sounds with frequencies ranging from approximately 20 Hz to 20,000 Hz. Longitudinal waves in a medium with a pressure change frequency of less than 20 Hz are called infrasound, and with a frequency of more than 20,000 Hz - ultrasound. The human ear does not perceive infrasound and ultrasound, that is, does not hear. It should be noted that the indicated boundaries of the sound range are arbitrary, since they depend on the age of people and the individual characteristics of their sound apparatus. Typically, with age, the upper frequency limit of perceived sounds decreases significantly - some older people can hear sounds with frequencies not exceeding 6,000 Hz. Children, on the contrary, can perceive sounds whose frequency is slightly higher than 20,000 Hz.

Vibrations with frequencies greater than 20,000 Hz or less than 20 Hz are heard by some animals.

The subject of the study of physiological acoustics is the organ of hearing itself, its structure and action. Architectural acoustics studies the propagation of sound in rooms, the influence of sizes and shapes on sound, and the properties of the materials with which walls and ceilings are covered. This refers to the auditory perception of sound.

There is also musical acoustics, which studies musical instruments and the conditions for them to sound best. Physical acoustics deals with the study of sound vibrations themselves, and has recently embraced vibrations that lie beyond the limits of audibility (ultraacoustics). It widely uses a variety of methods to convert mechanical vibrations into electrical ones and vice versa (electroacoustics).

Historical reference

Sounds began to be studied in ancient times, because humans are characterized by an interest in everything new. The first acoustic observations were made in the 6th century BC. Pythagoras established a connection between the pitch of a tone and the long string or pipe that produces the sound.

In the 4th century BC, Aristotle was the first to correctly understand how sound travels through air. He said that a sounding body causes compression and rarefaction of air; he explained the echo by the reflection of sound from obstacles.

In the 15th century, Leonardo da Vinci formulated the principle of independence of sound waves from various sources.

In 1660, Robert Boyle's experiments proved that air is a conductor of sound (sound does not travel in a vacuum).

In 1700-1707 Joseph Saveur's memoirs on acoustics were published by the Paris Academy of Sciences. In this memoir, Saveur examines a phenomenon well known to organ designers: if two pipes of an organ produce two sounds at the same time, only slightly different in pitch, then periodic amplifications of the sound are heard, similar to the roll of a drum. Saveur explained this phenomenon by the periodic coincidence of vibrations of both sounds. If, for example, one of two sounds corresponds to 32 vibrations per second, and the other corresponds to 40 vibrations, then the end of the fourth vibration of the first sound coincides with the end of the fifth vibration of the second sound and thus the sound is amplified. From organ pipes, Saveur moved on to the experimental study of string vibrations, observing the nodes and antinodes of vibrations (these names, which still exist in science, were introduced by him), and also noticed that when the string is excited, along with the main note, other notes sound, length the waves of which are ½, 1/3, ¼,. from the main one. He called these notes the highest harmonic tones, and this name was destined to remain in science. Finally, Saveur was the first to try to determine the limit of perception of vibrations as sounds: for low sounds he indicated a limit of 25 vibrations per second, and for high sounds - 12,800. Then, Newton, based on these experimental works of Saveur, gave the first calculation of the wavelength of sound and came to the conclusion, now well known in physics, that for any open pipe the wavelength of the emitted sound is equal to twice the length of the pipe.

Sound sources and their nature

What all sounds have in common is that the bodies that generate them, i.e., the sources of sound, vibrate. Everyone is familiar with the sounds that arise from the movement of leather stretched over a drum, waves of sea surf, and branches swayed by the wind. They are all different from each other. The “coloring” of each individual sound strictly depends on the movement due to which it arises. So if the vibrational motion is extremely fast, the sound contains high frequency vibrations. A less rapid oscillatory motion produces a lower frequency sound. Various experiments indicate that any sound source necessarily vibrates (although most often these vibrations are not noticeable to the eye). For example, the sounds of the voices of people and many animals arise as a result of vibrations of their vocal cords, the sound of wind musical instruments, the sound of a siren, the whistle of the wind, and the sound of thunder are caused by vibrations of air masses.

But not every oscillating body is a source of sound. For example, an oscillating weight suspended on a thread or spring does not make a sound.

The frequency at which the oscillations repeat is measured in hertz (or cycles per second); 1Hz is the frequency of such a periodic oscillation, the period is 1s. Note that frequency is the property that allows us to distinguish one sound from another.

Research has shown that the human ear is capable of perceiving as sound mechanical vibrations of bodies occurring with a frequency from 20 Hz to 20,000 Hz. With very fast, more than 20,000 Hz or very slow, less than 20 Hz, sound vibrations we do not hear. That is why we need special instruments to record sounds that lie outside the frequency range perceived by the human ear.

If the speed of the oscillatory movement determines the frequency of the sound, then its magnitude (the size of the room) determines the volume. If such a wheel is rotated at high speed, a high-frequency tone will appear; slower rotation will produce a tone of lower frequency. Moreover, the smaller the teeth of the wheel (as shown by the dotted line), the weaker the sound, and the larger the teeth, that is, the more they force the plate to deflect, the louder the sound. Thus, we can note another characteristic of sound - its volume (intensity).

It is impossible not to mention such a property of sound as quality. Quality is closely related to structure, which can range from overly complex to extremely simple. The tone of a tuning fork supported by a resonator has a very simple structure, since it contains only one frequency, the value of which depends solely on the design of the tuning fork. In this case, the sound of a tuning fork can be both strong and weak.

It is possible to create complex sounds, so, for example, many frequencies contain the sound of an organ chord. Even the sound of a mandolin string is quite complex. This is due to the fact that a stretched string vibrates not only with the main one (like a tuning fork), but also with other frequencies. They generate additional tones (harmonics), the frequencies of which are an integer number times higher than the frequency of the fundamental tone.

The concept of frequency is inappropriate to apply to noise, although we can talk about some areas of its frequencies, since they are what distinguish one noise from another. The noise spectrum can no longer be represented by one or several lines, as in the case of a monochromatic signal or a periodic wave containing many harmonics. It is depicted as a whole stripe

The frequency structure of some sounds, especially musical ones, is such that all overtones are harmonic in relation to the fundamental tone; in such cases, sounds are said to have a pitch (determined by the frequency of the fundamental tone). Most sounds are not so melodic; they do not have the integer relationship between frequencies characteristic of musical sounds. These sounds are similar in structure to noise. Therefore, to summarize what has been said, we can say that sound is characterized by volume, quality and height.

What happens to sound after it occurs? How does it reach our ear, for example? How is it distributed?

We perceive sound with the ear. Between the sounding body (sound source) and the ear (sound receiver) there is a substance that transmits sound vibrations from the sound source to the receiver. Most often, this substance is air. Sound cannot travel in airless space. Just like waves cannot exist without water. Experiments confirm this conclusion. Let's consider one of them. Place a bell under the air pump bell and turn it on. Then they begin to pump out the air. As the air becomes thinner, the sound becomes audible weaker and weaker and, finally, almost completely disappears. When I begin to let air under the bell again, the sound of the bell again becomes audible.

Of course, sound travels not only in air, but also in other bodies. This can also be verified experimentally. Even a sound as faint as the ticking of a pocket watch lying at one end of the table can be clearly heard when one puts one's ear to the other end of the table.

It is well known that sound is transmitted over long distances over the ground and especially over railway rails. By placing your ear to the rail or the ground, you can hear the sound of a far-reaching train or the tramp of a galloping horse.

If we hit a stone against a stone while underwater, we will clearly hear the sound of the impact. Consequently, sound also travels in water. Fish hear footsteps and voices of people on the shore, this is well known to fishermen.

Experiments show that different solids conduct sound in different ways. Elastic bodies are good conductors of sound. Most metals, wood, gases, and liquids are elastic bodies and therefore conduct sound well.

Soft and porous bodies are poor conductors of sound. When, for example, a watch is in a pocket, it is surrounded by soft fabric, and we do not hear its ticking.

By the way, the propagation of sound in solids is related to the fact that the experiment with a bell placed under a hood did not seem very convincing for a long time. The fact is that the experimenters did not isolate the bell well enough, and the sound was heard even when there was no air under the hood, since the vibrations were transmitted through various connections of the installation.

In 1650, Athanasius Kirch'er and Otto Hücke, based on an experiment with a bell, concluded that air was not needed for sound propagation. And only ten years later, Robert Boyle convincingly proved the opposite. Sound in the air, for example, is transmitted by longitudinal waves, i.e., alternating condensations and rarefactions of air coming from the sound source. But since the space around us, unlike the two-dimensional surface of water, is three-dimensional, then sound waves propagate not in two, but in three directions - in the form of diverging spheres.

Sound waves, like any other mechanical waves, do not propagate through space instantly, but at a certain speed. The simplest observations allow us to verify this. For example, during a thunderstorm, we first see lightning and only some time later hear thunder, although the vibrations of the air, which we perceive as sound, occur simultaneously with the flash of lightning. The fact is that the speed of light is very high (300,000 km/s), so we can assume that we see a flash at the moment it occurs. And the sound of thunder, formed simultaneously with lightning, requires quite noticeable time for us to travel the distance from the place of its origin to an observer standing on the ground. For example, if we hear thunder more than 5 seconds after we see lightning, we can conclude that the thunderstorm is at least 1.5 km away from us. The speed of sound depends on the properties of the medium in which sound travels. Scientists have developed various methods for determining the speed of sound in any environment.

The speed of sound and its frequency determine the wavelength. Observing waves in a pond, we notice that the radiating circles are sometimes smaller and sometimes larger, in other words, the distance between wave crests or wave troughs can vary depending on the size of the object that created them. By holding our hand low enough above the surface of the water, we can feel every splash that passes us. The greater the distance between successive waves, the less often their crests will touch our fingers. This simple experiment allows us to conclude that in the case of waves on the water surface, for a given speed of wave propagation, a higher frequency corresponds to a smaller distance between the wave crests, that is, shorter waves, and, conversely, a lower frequency corresponds to longer waves.

The same is true for sound waves. The fact that a sound wave passes through a certain point in space can be judged by the change in pressure at this point. This change completely repeats the vibration of the sound source membrane. A person hears sound because the sound wave exerts varying pressure on the eardrum of his ear. As soon as the crest of the sound wave (or high pressure area) reaches our ear. We feel the pressure. If areas of increased pressure of a sound wave follow each other quickly enough, then the eardrum of our ear vibrates quickly. If the crests of the sound wave lag significantly behind each other, then the eardrum will vibrate much more slowly.

The speed of sound in air is a surprisingly constant value. We have already seen that the frequency of sound is directly related to the distance between the crests of the sound wave, that is, there is a certain relationship between the frequency of sound and the wavelength. We can express this relationship as follows: wavelength equals speed divided by frequency. Another way to put it is that wavelength is inversely proportional to frequency, with a coefficient of proportionality equal to the speed of sound.

How does sound become audible? When sound waves enter the ear canal, they vibrate the eardrum, middle ear, and inner ear. Entering the fluid filling the cochlea, air waves affect the hair cells inside the organ of Corti. The auditory nerve transmits these impulses to the brain, where they are converted into sounds.

Noise measurement

Noise is an unpleasant or undesirable sound, or a set of sounds that interfere with the perception of useful signals, break silence, have a harmful or irritating effect on the human body, reducing its performance.

In noisy areas, many people experience symptoms of noise sickness: increased nervous excitability, fatigue, high blood pressure.

The noise level is measured in units,

Expressing the degree of pressure sounds, decibels. This pressure is not perceived infinitely. A noise level of 20-30 dB is practically harmless to humans - this is a natural background noise. As for loud sounds, the permissible limit here is approximately 80 dB. A sound of 130 dB already causes pain in a person, and 150 becomes unbearable for him.

Acoustic noise is random sound vibrations of different physical nature, characterized by random changes in amplitude and frequency.

When a sound wave, consisting of condensations and rarefactions of air, propagates, the pressure on the eardrum changes. The unit for pressure is 1 N/m2 and the unit for sound power is 1 W/m2.

The hearing threshold is the minimum sound volume that a person perceives. It is different for different people, and therefore, conventionally, the hearing threshold is considered to be a sound pressure equal to 2x10"5 N/m2 at 1000 Hz, corresponding to a power of 10"12 W/m2. It is with these values ​​that the measured sound is compared.

For example, the sound power of engines during takeoff of a jet aircraft is 10 W/m2, that is, it exceeds the threshold by 1013 times. It is inconvenient to operate with such large numbers. About sounds of different loudness they say that one is louder than the other not by so many times, but by so many units. The loudness unit is called Bel - after the inventor of the telephone A. Bel (1847-1922). Loudness is measured in decibels: 1 dB = 0.1 B (Bel). A visual representation of how sound intensity, sound pressure and volume level are related.

The perception of sound depends not only on its quantitative characteristics (pressure and power), but also on its quality - frequency.

The same sound at different frequencies differs in volume.

Some people cannot hear high frequency sounds. Thus, in older people, the upper limit of sound perception decreases to 6000 Hz. They do not hear, for example, the squeak of a mosquito or the trill of a cricket, which produce sounds with a frequency of about 20,000 Hz.

The famous English physicist D. Tyndall describes one of his walks with a friend as follows: “The meadows on both sides of the road were swarming with insects, which to my ears filled the air with their sharp buzzing, but my friend did not hear any of this - the music of the insects flew beyond the boundaries of his hearing.” !

Noise levels

Loudness - the level of energy in sound - is measured in decibels. A whisper equates to approximately 15 dB, the rustle of voices in a student classroom reaches approximately 50 dB, and street noise during heavy traffic is approximately 90 dB. Noises above 100 dB can be unbearable to the human ear. Noises around 140 dB (such as the sound of a jet plane taking off) can be painful to the ear and damage the eardrum.

For most people, hearing acuity decreases with age. This is explained by the fact that the ear bones lose their original mobility, and therefore vibrations are not transmitted to the inner ear. In addition, ear infections can damage the eardrum and negatively affect the functioning of the ossicles. If you experience any hearing problems, you should immediately consult a doctor. Some types of deafness are caused by damage to the inner ear or auditory nerve. Hearing loss can also be caused by constant noise exposure (for example, in a factory floor) or sudden and very loud sound bursts. You should be very careful when using personal stereo players, as excessive volume can also cause deafness.

Permissible noise in the premises

With regard to noise levels, it is worth noting that such a concept is not ephemeral and unregulated from the point of view of legislation. Thus, in Ukraine, the Sanitary standards for permissible noise in residential and public buildings and in residential areas, adopted back in the days of the USSR, are still in effect. According to this document, in residential premises the noise level must not exceed 40 dB during the day and 30 dB at night (from 22:00 to 8:00).

Often noise carries important information. A car or motorcycle racer listens carefully to the sounds made by the engine, chassis and other parts of a moving vehicle, because any extraneous noise can be a harbinger of an accident. Noise plays a significant role in acoustics, optics, computer technology, and medicine.

What is noise? It is understood as random complex vibrations of various physical natures.

The noise problem has been around for a long time. Already in ancient times, the sound of wheels on cobblestone streets caused insomnia for many.

Or maybe the problem arose even earlier, when the neighbors in the cave began to quarrel because one of them was knocking too loudly while making a stone knife or ax?

Noise pollution in the environment is increasing all the time. If in 1948, when surveying residents of large cities, 23% of respondents answered affirmatively to the question of whether noise in their apartment bothered them, then in 1961 the figure was already 50%. In the last decade, noise levels in cities have increased 10-15 times.

Noise is a type of sound, although it is often called “unwanted sound.” At the same time, according to experts, the noise of a tram is estimated at 85-88 dB, a trolleybus - 71 dB, a bus with an engine power of more than 220 hp. With. - 92 dB, less than 220 l. With. - 80-85 dB.

Scientists from The Ohio State University concluded that people who are regularly exposed to loud noises are 1.5 times more likely than others to develop acoustic neuroma.

Acoustic neuroma is a benign tumor that causes hearing loss. Scientists examined 146 patients with acoustic neuroma and 564 healthy people. They were all asked how often they encountered loud noises of at least 80 decibels (traffic noise). The questionnaire took into account the noise of appliances, engines, music, children's screams, noise at sporting events, in bars and restaurants. Study participants were also asked whether they used hearing protection devices. Those who regularly listened to loud music had a 2.5-fold increased risk of developing acoustic neuroma.

For those exposed to technical noise – 1.8 times. For people who regularly listen to children scream, the noise in stadiums, restaurants or bars is 1.4 times higher. When wearing hearing protection, the risk of developing an acoustic neuroma is no greater than in people who are not exposed to noise at all.

Impact of acoustic noise on humans

The impact of acoustic noise on humans varies:

A. Harmful

Noise leads to the development of a benign tumor

Long-term noise adversely affects the organ of hearing, stretching the eardrum, thereby reducing sensitivity to sound. It leads to disruption of the heart and liver, and to exhaustion and overstrain of nerve cells. Sounds and noises of high power affect the hearing aid, nerve centers, and can cause pain and shock. This is how noise pollution works.

Artificial, man-made noises. They negatively affect the human nervous system. One of the most harmful city noises is the noise of motor vehicles on major highways. It irritates the nervous system, so a person is tormented by anxiety and feels tired.

B. Favorable

Useful sounds include the noise of leaves. The splashing of waves has a calming effect on our psyche. The quiet rustle of leaves, the murmur of a stream, the light splash of water and the sound of the surf are always pleasant to a person. They calm him down and relieve stress.

C. Medicinal

The therapeutic effect on humans using the sounds of nature arose among doctors and biophysicists who worked with astronauts back in the early 80s of the twentieth century. In psychotherapeutic practice, natural noises are used as an aid in the treatment of various diseases. Psychotherapists also use so-called “white noise”. This is a kind of hissing, vaguely reminiscent of the sound of waves without the splash of water. Doctors believe that “white noise” calms and lulls you to sleep.

The effect of noise on the human body

But is it only the hearing organs that are affected by noise?

Students are encouraged to find out by reading the following statements.

1. Noise causes premature aging. In thirty cases out of a hundred, noise reduces the life expectancy of people in large cities by 8-12 years.

2. Every third woman and every fourth man suffer from neuroses caused by increased noise levels.

3. Diseases such as gastritis, stomach and intestinal ulcers are most often found in people living and working in noisy environments. For pop musicians, stomach ulcers are an occupational disease.

4. A sufficiently strong noise after 1 minute can cause changes in the electrical activity of the brain, which becomes similar to the electrical activity of the brain in patients with epilepsy.

5. Noise depresses the nervous system, especially when it is repeated.

6. Under the influence of noise, there is a persistent decrease in the frequency and depth of breathing. Sometimes cardiac arrhythmia and hypertension appear.

7. Under the influence of noise, carbohydrate, fat, protein, and salt metabolisms change, which manifests itself in changes in the biochemical composition of the blood (blood sugar levels decrease).

Excessive noise (above 80 dB) affects not only the hearing organs, but also other organs and systems (circulatory, digestive, nervous, etc.), vital processes are disrupted, energy metabolism begins to prevail over plastic metabolism, which leads to premature aging of the body .

NOISE PROBLEM

A large city is always accompanied by traffic noise. Over the past 25-30 years, in major cities around the world, noise has increased by 12-15 dB (i.e., the noise volume has increased by 3-4 times). If there is an airport within the city, as is the case in Moscow, Washington, Omsk and a number of other cities, then this leads to multiple excesses of the maximum permissible level of sound stimuli.

And yet, road transport is the leading source of noise in the city. It is this that causes noise of up to 95 dB on the sound level meter scale on the main streets of cities. The noise level in living rooms with closed windows facing the highway is only 10-15 dB lower than on the street.

The noise of cars depends on many reasons: the make of the car, its serviceability, speed, quality of the road surface, engine power, etc. The noise from the engine increases sharply when it starts and warms up. When the car is moving at first speed (up to 40 km/h), the engine noise is 2 times higher than the noise it creates at second speed. When the car brakes sharply, the noise also increases significantly.

The dependence of the state of the human body on the level of environmental noise has been revealed. Certain changes in the functional state of the central nervous and cardiovascular systems caused by noise have been noted. Coronary heart disease, hypertension, and increased cholesterol levels in the blood are more common in people living in noisy areas. Noise significantly disrupts sleep, reducing its duration and depth. The time it takes to fall asleep increases by an hour or more, and after waking up people feel tired and have a headache. Over time, all this turns into chronic fatigue, weakens the immune system, contributes to the development of diseases, and reduces performance.

It is now believed that noise can shorten a person's life expectancy by almost 10 years. There are more and more mentally ill people due to increasing sound stimuli; noise has a particularly strong effect on women. In general, the number of hard of hearing people in cities has increased, and headaches and increased irritability have become the most common phenomena.

NOISE POLLUTION

Sound and high-power noise affect the hearing aid, nerve centers and can cause pain and shock. This is how noise pollution works. The quiet rustling of leaves, the murmur of a stream, bird voices, the light splash of water and the sound of the surf are always pleasant to a person. They calm him down and relieve stress. This is used in medical institutions, in psychological relief rooms. The natural noises of nature are becoming increasingly rare, disappearing completely or are drowned out by industrial, transport and other noises.

Long-term noise adversely affects the hearing organ, reducing sensitivity to sound. It leads to disruption of the heart and liver, and to exhaustion and overstrain of nerve cells. Weakened cells of the nervous system cannot sufficiently coordinate the work of various body systems. This is where disruptions in their activities arise.

We already know that noise of 150 dB is harmful to humans. It was not for nothing that in the Middle Ages there was execution under the bell. The roar of the bells tormented and slowly killed.

Each person perceives noise differently. Much depends on age, temperament, health, and environmental conditions. Noise has an accumulative effect, that is, acoustic irritations, accumulating in the body, increasingly depress the nervous system. Noise has a particularly harmful effect on the neuropsychic activity of the body.

Noises cause functional disorders of the cardiovascular system; has a harmful effect on the visual and vestibular analyzers; reduce reflex activity, which often causes accidents and injuries.

Noise is insidious, its harmful effects on the body occur invisibly, imperceptibly, damage to the body is not immediately detected. In addition, the human body is practically defenseless against noise.

Increasingly, doctors are talking about noise illness, which primarily affects the hearing and nervous system. The source of noise pollution can be an industrial enterprise or transport. Heavy dump trucks and trams produce especially loud noise. Noise affects the human nervous system, and therefore noise protection measures are taken in cities and enterprises. Railway and tram lines and roads along which freight transport passes need to be moved from the central parts of cities to sparsely populated areas and green spaces created around them that absorb noise well. Airplanes should not fly over cities.

SOUNDPROOFING

Sound insulation helps to avoid the harmful effects of noise

Reducing noise levels is achieved through construction and acoustic measures. In external building envelopes, windows and balcony doors have significantly less sound insulation than the wall itself.

The degree of noise protection of buildings is primarily determined by the permissible noise standards for premises for a given purpose.

COMBAT ACOUSTIC NOISE

The Acoustics Laboratory of MNIIP is developing sections “Acoustic Ecology” as part of the project documentation. Projects are being carried out on soundproofing premises, noise control, calculations of sound reinforcement systems, and acoustic measurements. Although in ordinary rooms people increasingly want acoustic comfort - good protection from noise, intelligible speech and the absence of the so-called. acoustic phantoms - negative sound images formed by some. In designs designed to additionally combat decibels, at least two layers alternate - “hard” (plasterboard, gypsum fiber). Also, acoustic design should occupy its modest niche inside. Frequency filtering is used to combat acoustic noise.

CITY AND GREEN PLACES

If you protect your home from noise by trees, then it will be useful to know that sounds are not absorbed by leaves. Hitting the trunk, sound waves are broken, heading down to the soil, where they are absorbed. Spruce is considered the best guardian of silence. Even along the busiest highway you can live in peace if you protect your home with a row of green fir trees. And it would be nice to plant chestnuts nearby. One mature chestnut tree clears a space up to 10 m high, up to 20 m wide and up to 100 m long from car exhaust gases. Moreover, unlike many other trees, the chestnut decomposes toxic gases with almost no damage to its “health.”

The importance of landscaping city streets is great - dense plantings of shrubs and forest belts protect from noise, reducing it by 10-12 dB (decibels), reduce the concentration of harmful particles in the air from 100 to 25%, reduce wind speed from 10 to 2 m/s, reduce the concentration of gases from cars up to 15% per unit volume of air, make the air more humid, lower its temperature, i.e. make it more acceptable for breathing.

Green spaces also absorb sound; the taller the trees and the denser their planting, the less sound is heard.

Green spaces in combination with lawns and flower beds have a beneficial effect on the human psyche, calm the eyesight and nervous system, are a source of inspiration, and increase people’s performance. The greatest works of art and literature, discoveries of scientists, arose under the beneficial influence of nature. This is how the greatest musical creations of Beethoven, Tchaikovsky, Strauss and other composers, paintings by wonderful Russian landscape artists Shishkin, Levitan, and works of Russian and Soviet writers were created. It is no coincidence that the Siberian scientific center was founded among the green spaces of the Priobsky forest. Here, in the shade from the city noise and surrounded by greenery, our Siberian scientists successfully conduct their research.

The greenness of cities such as Moscow and Kyiv is high; in the latter, for example, there are 200 times more plantings per inhabitant than in Tokyo. In the capital of Japan, over 50 years (1920-1970), about half of all green areas located within a radius of ten kilometers from the center were destroyed. In the United States, almost 10 thousand hectares of central city parks have been lost over the past five years.

← Noise has a detrimental effect on a person’s health, primarily by deteriorating hearing and the condition of the nervous and cardiovascular systems.

← Noise can be measured using special instruments - sound level meters.

← It is necessary to combat the harmful effects of noise by controlling noise levels, as well as using special measures to reduce noise levels.

Due to the energy turnaround, renewable energies are becoming increasingly important in Baden-Württemberg. The central element in this is the use of wind energy. In 2011, local wind power generated about one percent of the land's electricity. There were a total of 380 wind power plants in operation. By 2020, the total capacity of wind turbines should increase from 500 megawatts (as of 2012) to 3,500 megawatts. About ten percent of all electricity will have to be generated by wind power plants. One typical wind turbine with a nominal power of 2 MW, located in a favorable area in Baden-Württemberg, can theoretically supply over 1,000 households with electricity.

When developing wind energy, the impact on people and the environment must be taken into account. Wind power plants create noise. With proper planning and a sufficient distance from residential developments, wind energy installations do not cause any acoustic disturbance. Already at a distance of several hundred meters, the noise of a wind turbine is almost no higher than the natural noise of wind in vegetation. Along with sound waves, wind turbines produce, due to air flowing around the rotating blades, noise of a lower frequency, the so-called infrasound or extremely low tone. Hearing in this range is extremely insensitive. Yet within the framework of wind energy development, there are concerns that these infrasonic waves cause harm to humans or may be hazardous to their health. This brochure is intended to promote discussion on this issue.

What is sound?

Sound consists, simply put, of compression waves. As these pressure fluctuations propagate, sound is transmitted through the air. Human hearing is able to detect sound with a frequency of 20 to 20,000 Hertz. Hertz is a unit of frequency that is determined by the number of vibrations per second. Low frequencies correspond to low tones, high frequencies correspond to high tones. Frequencies below 20 Hz are called infrasound. Noise above the audio range, i.e. above 20,000 Hz is known as ultrasound. Low frequencies are sounds whose predominant part is in the range below 100 Hz. Periodic fluctuations in air pressure travel at the speed of sound, about 340 m/sec. Low frequency vibrations have a long wavelength, and high frequency vibrations have a short wavelength. For example, the wavelength of a 20-Hz tone is 17.5 m, and at a frequency of 20,000 Hz it is 1.75 cm.

How does infrasound travel?

The propagation of infrasound is subject to the same physical laws as all types of waves propagating in the air. A separate sound source, for example a wind power generator, emits waves that propagate spherically in all directions. Since the sound energy is distributed over an increasingly larger area, the sound intensity per square meter has an inverse geometric relationship: with increasing distance, the sound becomes quieter (see figure).

Along with this, there is the effect of absorption of waves in the air. A small part of the sound energy during propagation is converted into heat, resulting in an additional reduction in sound. This absorption depends on frequency: sounds of lower frequencies are reduced less, sounds of higher frequencies are reduced more. The decrease in sound intensity with distance significantly exceeds its loss due to absorption. The peculiarity is that low-frequency vibrations very easily pass through walls and windows, as a result of which the impact occurs inside the building.

Where does infrasound occur?

Infrasound is a normal part of our environment. It is emitted by a huge number of different sources. These include both natural sources, such as wind, waterfall or sea surf, and technical ones, such as heaters and air conditioners, street and rail transport, airplanes or audio systems in discos.

The noise of wind power plants.

Modern wind power plants produce noise over the entire frequency range, depending on the wind strength, including low-frequency tones and infrasound. This occurs due to the breakdown of turbulence, especially at the tips of the blades, as well as at the edges, crevices and struts. The air flowing around the blade creates a noise similar to the noise of a glider wing.

The sound emission increases with increasing wind speed until the unit reaches its rated power. After that it remains constant. Specific infrasound radiation is comparable to radiation from other technical installations.

Studies have shown that infrasound radiation from a wind power plant is below the threshold of human perception. The green line of the graph shows that at a distance of 250 meters the measured values ​​are below the perception threshold.

At the same time, a strong wind, passing through natural obstacles, can create infrasound of greater intensity. For comparison, inside an administrative building, according to measurements carried out by LUBW, the infrasound level lies below the green line. The wind speed in both cases was exactly 6 m/s. Many everyday noises contain significantly more infrasound.

The graph above shows an example of noise inside a passenger car. At a speed of 130 km/h, infrasound becomes even audible. When the side windows are open, the noise is felt as unpleasant. Its intensity is 70 decibels, i.e. 10,000,000 times stronger than near a wind turbine in strong winds.

Low-frequency noise assessment.

In the range of low-frequency oscillations below 100 Hz there is a smooth transition of auditory perception from hearing the strength of sound and pitch to sensation. Here the quality and method of perception changes. The perception of pitch decreases and disappears completely with infrasound. In general, it works like this: the lower the frequency, the stronger the sound intensity must be in order for the noise to be heard at all. Low-frequency exposures of higher intensity, such as the above noise from inside a car, are often perceived as pressure on the ears and vibrations. Prolonged exposure to vibrations of this frequency can cause noise in the head, a feeling of pressure or rocking. Along with hearing, there are also other sense organs that perceive low frequencies. This is how sensitive skin cells perceive pressure and vibration. Infrasound can also affect spaces in the body such as the lungs, nostrils and middle ear. Very high intensity infrasound has a masked effect in the mid and lower sound range. This means: With very strong infrasound, the hearing is not able to simultaneously perceive a quiet sound in this higher frequency range.

Health effects

Laboratory studies of the effects of infrasound show that high intensities above the threshold of perception can cause fatigue, loss of concentration and exhaustion. The body's most well-known reaction is increased fatigue after hours of exposure. The sense of balance may also be affected. Some researchers felt a sense of uncertainty and fear, while others experienced a decrease in breathing rate.

Further, as with sound radiation, at very high intensity there is a temporary decrease in hearing, this effect is known to visitors to discos. Long-term exposure to infrasound can cause long-term hearing loss. The noise level in the immediate vicinity of a wind generator is very far from such effects. Due to the fact that the hearing threshold is clearly exceeded, irritation from infrasound is not expected. There is no scientific documentation about the effects we talked about.

Conclusions:

The ultrasound produced by wind turbines is definitely below the limit of human sensitivity. According to the current state of science, harmful effects of ultrasound from wind power plants are not expected.

Compared to vehicles like a car or an airplane, the infrasound from wind power plants is negligible. Observing the overall range of sound frequencies, we see that the noise from a wind power plant already a few hundred meters away is almost inaudible against the background of the wind in the vegetation.

It is necessary to pay attention to the compatibility of wind power plants and residential buildings. The Baden-Württemberg Wind Energy Regulations stipulate a safety distance of 700 m between wind energy installations and residential buildings for local and land use planning. As an exception, with careful study of individual cases, the distance can be either increased or decreased.