Today, scoring theater plays and films is relatively simple. Most of the necessary noise exists in electronic form; the missing ones are recorded and processed on a computer. But half a century ago, amazingly ingenious mechanisms were used to imitate sounds.

Tim Skorenko

These amazing noise machines have been exhibited over the past years in a variety of places, for the first time a few years ago at the Polytechnic Museum. There we examined this entertaining exhibition in detail. Wood-metal devices that amazingly imitate the sounds of surf and wind, passing cars and trains, the clatter of hooves and the clanking of swords, the chirping of a grasshopper and the croaking of a frog, the clanging of tracks and exploding shells - all these amazing machines were developed, improved and described by Vladimir Aleksandrovich Popov - actor and the creator of noise design in theater and cinema, to whom the exhibition is dedicated. The most interesting thing is the interactivity of the exhibition: the devices are not, as is often our custom, behind three layers of bulletproof glass, but are intended for the user. Come, spectator, pretend to be a sound designer, whistle with the wind, make noise with a waterfall, play with the train - and it’s interesting, really interesting.

Harmonium. “The musical instrument harmonium is used to convey the noise of the tank. The performer simultaneously presses several lower keys (both black and white) on the keyboard and at the same time pumps air with the help of pedals” (V.A. Popov).

Noise master

Vladimir Popov began his career as an actor at the Moscow Art Theater, even before the revolution, in 1908. In his memoirs, he wrote that since childhood he was fond of sound imitation, trying to copy various noises, natural and artificial. Since the 1920s, he finally went into the sound industry, designing various machines for the sound design of performances. And in the thirties, his mechanisms appeared in films. For example, with the help of his amazing machines, Popov voiced the legendary painting by Sergei Eisenstein “Alexander Nevsky”.

He treated noise like music, wrote scores for the sound background of plays and radio shows - and invented, invented, invented. Some of the machines created by Popov have survived to this day, gathering dust in the back rooms of various theaters - the development of sound recording has made his ingenious mechanisms, which require certain handling skills, unnecessary. Today, the noise of a train is simulated using electronic methods, but in priestly times, a whole orchestra, according to a strictly specified algorithm, worked with various devices to create a reliable imitation of an approaching train. Popov's noise compositions sometimes involved up to twenty musicians.

Tank noise. “If a tank appears on the scene, then at that moment four-wheeled devices with metal plates come into action. The device is driven by rotation of the cross around an axis. The result is a strong sound, very similar to the clanging of the tracks of a large tank” (V.A. Popov).

The results of his work were the book “Sound Design of a Performance,” published in 1953, and the Stalin Prize received at the same time. We can cite here many different facts from the life of the great inventor - but we will turn to technology.

Wood and iron

The most important point, which exhibition visitors do not always pay attention to, is the fact that each noise machine is a musical instrument that you need to be able to play and which requires certain acoustic conditions. For example, during performances, the “thunder machine” was always placed at the very top, on the walkway above the stage, so that the peals of thunder could be heard throughout the entire auditorium, creating a feeling of presence. In a small room, it does not make such a bright impression, its sound is not so natural and is much closer to what it really is - the clanging of iron wheels built into the mechanism. However, the “unnaturalness” of some sounds is explained by the fact that many of the mechanisms are not intended for “solo” work - only “in an ensemble”.

Other machines, on the contrary, perfectly imitate sound regardless of the acoustic properties of the room. For example, the “Roll” (a mechanism that produces the sound of the surf), huge and clumsy, so accurately copies the impacts of waves on a gentle shore that, closing your eyes, you can easily imagine yourself somewhere by the sea, at a lighthouse, in windy weather.

Horse transport No. 4. “A device that reproduces the noise of a fire truck. In order to produce a weak noise at the beginning of the device’s operation, the performer moves the control knob to the left, due to which the noise intensity is softened. When the axis moves to the other side, the noise increases to a significant degree” (V.A. Popov).

Popov divided noises into a number of categories: battle, natural, industrial, household, transport, etc. Some universal techniques could be used to simulate various noises. For example, sheets of iron of various thicknesses and sizes suspended at a certain distance from each other could imitate the noise of an approaching steam locomotive, the clang of production machines, and even thunder. Popov also called a huge grumbling drum a universal device, capable of working in different “industries.”

But most of these machines are quite simple. Specialized mechanisms designed to imitate one and only one sound contain very interesting engineering ideas. For example, the fall of water drops is simulated by the rotation of a drum, the side of which is replaced by ropes stretched at different distances. As they rotate, they raise fixed leather whips, which slap the next ropes - and it really looks like drops. Winds of varying strength are also simulated using drums rubbing against all kinds of fabrics.

Drum leather

Perhaps the most remarkable story associated with the reconstruction of Popov's machines happened during the manufacture of the large grunt drum. For a huge musical instrument with a diameter of almost two meters, leather was required - but it turned out that it was impossible to purchase dressed, but not tanned, drum skin in Russia. The musicians went to a real slaughterhouse, where they bought two freshly skinned bulls. “There was something surreal about it,” Peter laughs. “We drive up to the theater by car, and we have bloody skins in the trunk. We drag them onto the roof of the theater, we strip them, dry them - for a week the smell lingered throughout Sretenka...” But the drum was a great success in the end.

Vladimir Aleksandrovich provided each device with detailed instructions for the performer. For example, the “Powerful Crack” device: “Strong dry thunderstorm discharges are performed using the “Powerful Crack” device. Standing on the platform of the device, the performer, leaning his chest forward and placing both hands on top of the gear shaft, grabs it and turns it towards himself.”

It is worth noting that many of the machines used by Popov were developed before him: Vladimir Alexandrovich only improved them. In particular, wind drums were used in theaters back in the days of serfdom.

Graceful Life

One of the first films entirely scored using Popov’s mechanisms was the comedy “A Graceful Life” directed by Boris Yurtsev. Apart from the voices of the actors, in this film, released in 1932, there is not a single sound recorded from life - everything is simulated. It is worth noting that of the six full-length films shot by Yurtsev, this is the only one that has survived. The director, who fell into disgrace in 1935, was exiled to Kolyma; his films, except for La Fine Life, were lost.

New incarnation

After the advent of sound libraries, Popov's machines were almost forgotten. They have become relegated to the category of archaisms, a thing of the past. But there were people interested in the technology of the past not only “rising from the ashes,” but also becoming in demand again.

The idea of ​​making a musical art project (at that time not yet formalized as an interactive exhibition) had long been simmering in the minds of Moscow musician and virtuoso pianist Peter Aidu - and now it has finally found its material embodiment.

Device "frog". The instructions for the “Frog” device are much more complicated than similar instructions for other devices. The performer of the croaking sound had to have good command of the instrument so that the final sound imitation would be quite natural.

The team working on the project is partly based at the School of Dramatic Art theatre. Peter Aidu himself is the assistant to the chief director for the musical part, the coordinator of the production of exhibits Alexander Nazarov is the head of theater workshops, etc. However, dozens of people not connected with the theater took part in the work on the exhibition, but were ready to help and spend their time on strange cultural project - and all this was not in vain.

We talked with Peter Aidu in one of the rooms with the exhibition, in the terrible noise and commotion generated by visitors from the exhibits. “There are many layers to this exhibition,” he said. — A certain historical layer, since we brought to light the story of a very talented person, Vladimir Popov; interactive layer, because people enjoy what is happening; musical layer, since after the end of the exhibition we plan to use its exhibits in our performances, and not so much for scoring, but as independent art objects.” While Peter was speaking, the TV was playing behind him. On the screen is a scene where twelve people harmoniously play the composition “The Noise of a Train” (this is a fragment of the play “Reconstruction of Utopia”).

"Roll". “The performer activates the device by rhythmically rocking the resonator (device body) up and down. The quiet breaking of waves is accomplished by slowly pouring (not completely) the contents of the resonator from one end to the other. Having stopped pouring the contents in one direction, quickly move the resonator to a horizontal position and immediately move it to the other side. A powerful surge of waves is accomplished by slowly pouring out the entire contents of the resonator to the end” (V.A. Popov).

The machines were manufactured according to the drawings and descriptions left by Popov - the originals of some machines preserved in the Moscow Art Theater collection were seen by the creators of the exhibition after the completion of the work. One of the main problems was that parts and materials that were easily obtained in the 1930s are not used anywhere today and are not available for free sale. For example, it is almost impossible to find a brass sheet 3 mm thick and 1000x1000 mm in size, because the current GOST implies cutting brass only 600x1500. Problems arose even with plywood: the required 2.5-mm plywood, by modern standards, belongs to model aircraft and is quite rare, unless ordered from Finland.

Automobile. “The noise of a car is produced by two performers. One of them rotates the handle of the wheel, and the other presses the lever of the lifting board and opens the lids” (V.A. Popov). It is worth noting that with the help of levers and covers it was possible to significantly vary the sound of the car.

There was another difficulty. Popov himself repeatedly noted: in order to imitate any sound, you need to imagine absolutely exactly what you want to achieve. But, for example, none of our contemporaries have ever heard the sound of a semaphore switching from the 1930s live - how can you make sure that the corresponding device is made correctly? No way - you can only rely on intuition and old movies.

But in general, the creators’ intuition did not disappoint - they succeeded. Although noise machines were originally intended for people who knew how to operate them, and not for fun, they are very good as interactive museum exhibits. Rotating the handle of the next mechanism, looking at a silent movie broadcast on the wall, you feel like a great sound engineer. And you feel how under your hands not noise is born, but music.

February 18, 2016

The world of home entertainment is quite varied and can include: watching movies on a good home theater system; exciting and exciting gameplay or listening to music. As a rule, everyone finds something of their own in this area, or combines everything at once. But whatever a person’s goals for organizing his leisure time and whatever extreme they go to, all these links are firmly connected by one simple and understandable word - “sound”. Indeed, in all of the above cases, we will be led by the hand by sound. But this question is not so simple and trivial, especially in cases where there is a desire to achieve high-quality sound in a room or any other conditions. To do this, it is not always necessary to buy expensive hi-fi or hi-end components (although it will be very useful), but a good knowledge of physical theory is sufficient, which can eliminate most of the problems that arise for anyone who sets out to obtain high-quality voice acting.

Next, the theory of sound and acoustics will be considered from the point of view of physics. In this case, I will try to make this as accessible as possible to the understanding of any person who, perhaps, is far from knowing physical laws or formulas, but nevertheless passionately dreams of realizing the dream of creating a perfect acoustic system. I do not presume to say that in order to achieve good results in this area at home (or in a car, for example), you need to know these theories thoroughly, but understanding the basics will allow you to avoid many stupid and absurd mistakes, and will also allow you to achieve the maximum sound effect from the system any level.

General theory of sound and musical terminology

What is it sound? This is the sensation that the auditory organ perceives "ear"(the phenomenon itself exists without the participation of the “ear” in the process, but this is easier to understand), which occurs when the eardrum is excited by a sound wave. The ear in this case acts as a “receiver” of sound waves of various frequencies.
Sound wave it is essentially a sequential series of compactions and discharges of the medium (most often the air medium under normal conditions) of various frequencies. The nature of sound waves is oscillatory, caused and produced by the vibration of any body. The emergence and propagation of a classical sound wave is possible in three elastic media: gaseous, liquid and solid. When a sound wave occurs in one of these types of space, some changes inevitably occur in the medium itself, for example, a change in air density or pressure, movement of air mass particles, etc.

Since a sound wave has an oscillatory nature, it has such a characteristic as frequency. Frequency measured in hertz (in honor of the German physicist Heinrich Rudolf Hertz), and denotes the number of oscillations over a period of time equal to one second. Those. for example, a frequency of 20 Hz indicates a cycle of 20 oscillations in one second. The subjective concept of its height also depends on the frequency of the sound. The more sound vibrations occur per second, the “higher” the sound appears. A sound wave also has another important characteristic, which has a name - wavelength. Wavelength It is customary to consider the distance that a sound of a certain frequency travels in a period equal to one second. For example, the wavelength of the lowest sound in the human audible range at 20 Hz is 16.5 meters, and the wavelength of the highest sound at 20,000 Hz is 1.7 centimeters.

The human ear is designed in such a way that it is capable of perceiving waves only in a limited range, approximately 20 Hz - 20,000 Hz (depending on the characteristics of a particular person, some are able to hear a little more, some less). Thus, this does not mean that sounds below or above these frequencies do not exist, they are simply not perceived by the human ear, going beyond the audible range. Sound above the audible range is called ultrasound, sound below the audible range is called infrasound. Some animals are able to perceive ultra and infra sounds, some even use this range for orientation in space (bats, dolphins). If sound passes through a medium that is not in direct contact with the human hearing organ, then such sound may not be heard or may be greatly weakened subsequently.

In the musical terminology of sound, there are such important designations as octave, tone and overtone of sound. Octave means an interval in which the frequency ratio between sounds is 1 to 2. An octave is usually very distinguishable by ear, while sounds within this interval can be very similar to each other. An octave can also be called a sound that vibrates twice as much as another sound in the same period of time. For example, the frequency of 800 Hz is nothing more than a higher octave of 400 Hz, and the frequency of 400 Hz in turn is the next octave of sound with a frequency of 200 Hz. The octave, in turn, consists of tones and overtones. Variable vibrations in a harmonic sound wave of the same frequency are perceived by the human ear as musical tone. High-frequency vibrations can be interpreted as high-pitched sounds, while low-frequency vibrations can be interpreted as low-pitched sounds. The human ear is capable of clearly distinguishing sounds with a difference of one tone (in the range of up to 4000 Hz). Despite this, music uses an extremely small number of tones. This is explained from considerations of the principle of harmonic consonance; everything is based on the principle of octaves.

Let's consider the theory of musical tones using the example of a string stretched in a certain way. Such a string, depending on the tension force, will be “tuned” to one specific frequency. When this string is exposed to something with one specific force, which causes it to vibrate, one specific tone of sound will be consistently observed, and we will hear the desired tuning frequency. This sound is called the fundamental tone. The frequency of the note “A” of the first octave is officially accepted as the fundamental tone in the musical field, equal to 440 Hz. However, most musical instruments never reproduce pure fundamental tones alone; they are inevitably accompanied by overtones called overtones. Here it is appropriate to recall an important definition of musical acoustics, the concept of sound timbre. Timbre- this is a feature of musical sounds that gives musical instruments and voices their unique, recognizable specificity of sound, even when comparing sounds of the same pitch and volume. The timbre of each musical instrument depends on the distribution of sound energy among overtones at the moment the sound appears.

Overtones form a specific coloring of the fundamental tone, by which we can easily identify and recognize a specific instrument, as well as clearly distinguish its sound from another instrument. There are two types of overtones: harmonic and non-harmonic. Harmonic overtones by definition are multiples of the fundamental frequency. On the contrary, if the overtones are not multiples and noticeably deviate from the values, then they are called non-harmonic. In music, operating with multiple overtones is practically excluded, so the term is reduced to the concept of “overtone,” meaning harmonic. For some instruments, such as the piano, the fundamental tone does not even have time to form; in a short period of time, the sound energy of the overtones increases, and then just as rapidly decreases. Many instruments create what is called a "transition tone" effect, where the energy of certain overtones is highest at a certain point in time, usually at the very beginning, but then changes abruptly and moves on to other overtones. The frequency range of each instrument can be considered separately and is usually limited to the fundamental frequencies that that particular instrument is capable of producing.

In sound theory there is also such a concept as NOISE. Noise- this is any sound that is created by a combination of sources that are inconsistent with each other. Everyone is familiar with the sound of tree leaves swaying by the wind, etc.

What determines the volume of sound? Obviously, such a phenomenon directly depends on the amount of energy transferred by the sound wave. To determine quantitative indicators of loudness, there is a concept - sound intensity. Sound intensity is defined as the flow of energy passing through some area of ​​space (for example, cm2) per unit of time (for example, per second). During normal conversation, the intensity is approximately 9 or 10 W/cm2. The human ear is capable of perceiving sounds over a fairly wide range of sensitivity, while the sensitivity of frequencies is heterogeneous within the sound spectrum. This way, the frequency range 1000 Hz - 4000 Hz, which most widely covers human speech, is best perceived.

Because sounds vary so greatly in intensity, it is more convenient to think of it as a logarithmic quantity and measure it in decibels (after the Scottish scientist Alexander Graham Bell). The lower threshold of hearing sensitivity of the human ear is 0 dB, the upper is 120 dB, also called the “pain threshold”. The upper limit of sensitivity is also perceived by the human ear not in the same way, but depends on the specific frequency. Low-frequency sounds must have much greater intensity than high-frequency sounds to trigger the pain threshold. For example, the pain threshold at a low frequency of 31.5 Hz occurs at a sound intensity level of 135 dB, when at a frequency of 2000 Hz the sensation of pain will appear at 112 dB. There is also the concept of sound pressure, which actually expands the usual explanation of the propagation of a sound wave in the air. Sound pressure- this is a variable excess pressure that arises in an elastic medium as a result of the passage of a sound wave through it.

Wave nature of sound

To better understand the system of sound wave generation, imagine a classic speaker located in a pipe filled with air. If the speaker makes a sharp movement forward, the air in the immediate vicinity of the diffuser is momentarily compressed. The air will then expand, thereby pushing the compressed air region along the pipe.
This wave movement will subsequently become sound when it reaches the auditory organ and “excites” the eardrum. When a sound wave occurs in a gas, excess pressure and excess density are created and particles move at a constant speed. About sound waves, it is important to remember the fact that the substance does not move along with the sound wave, but only a temporary disturbance of the air masses occurs.

If we imagine a piston suspended in free space on a spring and making repeated movements “back and forth”, then such oscillations will be called harmonic or sinusoidal (if we imagine the wave as a graph, then in this case we will get a pure sinusoid with repeated declines and rises). If we imagine a speaker in a pipe (as in the example described above) performing harmonic oscillations, then at the moment the speaker moves “forward” the well-known effect of air compression is obtained, and when the speaker moves “backwards” the opposite effect of rarefaction occurs. In this case, a wave of alternating compression and rarefaction will propagate through the pipe. The distance along the pipe between adjacent maxima or minima (phases) will be called wavelength. If the particles oscillate parallel to the direction of propagation of the wave, then the wave is called longitudinal. If they oscillate perpendicular to the direction of propagation, then the wave is called transverse. Typically, sound waves in gases and liquids are longitudinal, but in solids waves of both types can occur. Transverse waves in solids arise due to resistance to change in shape. The main difference between these two types of waves is that a transverse wave has the property of polarization (oscillations occur in a certain plane), while a longitudinal wave does not.

Sound speed

The speed of sound directly depends on the characteristics of the medium in which it propagates. It is determined (dependent) by two properties of the medium: elasticity and density of the material. The speed of sound in solids directly depends on the type of material and its properties. Velocity in gaseous media depends on only one type of deformation of the medium: compression-rarefaction. The change in pressure in a sound wave occurs without heat exchange with surrounding particles and is called adiabatic.
The speed of sound in a gas depends mainly on temperature - it increases with increasing temperature and decreases with decreasing temperature. Also, the speed of sound in a gaseous medium depends on the size and mass of the gas molecules themselves - the smaller the mass and size of the particles, the greater the “conductivity” of the wave and, accordingly, the greater the speed.

In liquid and solid media, the principle of propagation and the speed of sound are similar to how a wave propagates in air: by compression-discharge. But in these environments, in addition to the same dependence on temperature, the density of the medium and its composition/structure are quite important. The lower the density of the substance, the higher the speed of sound and vice versa. The dependence on the composition of the medium is more complex and is determined in each specific case, taking into account the location and interaction of molecules/atoms.

Speed ​​of sound in air at t, °C 20: 343 m/s
Speed ​​of sound in distilled water at t, °C 20: 1481 m/s
Speed ​​of sound in steel at t, °C 20: 5000 m/s

Standing waves and interference

When a speaker creates sound waves in a confined space, the effect of waves being reflected from the boundaries inevitably occurs. As a result, this most often occurs interference effect- when two or more sound waves overlap each other. Special cases of interference phenomena are the formation of: 1) Beating waves or 2) Standing waves. Wave beats- this is the case when the addition of waves with similar frequencies and amplitudes occurs. The picture of the occurrence of beats: when two waves of similar frequencies overlap each other. At some point in time, with such an overlap, the amplitude peaks may coincide “in phase,” and the declines may also coincide in “antiphase.” This is how sound beats are characterized. It is important to remember that, unlike standing waves, phase coincidences of peaks do not occur constantly, but at certain time intervals. To the ear, this pattern of beats is distinguished quite clearly, and is heard as a periodic increase and decrease in volume, respectively. The mechanism by which this effect occurs is extremely simple: when the peaks coincide, the volume increases, and when the valleys coincide, the volume decreases.

Standing waves arise in the case of superposition of two waves of the same amplitude, phase and frequency, when when such waves “meet” one moves in the forward direction and the other in the opposite direction. In the area of ​​space (where the standing wave was formed), a picture of the superposition of two frequency amplitudes appears, with alternating maxima (the so-called antinodes) and minima (the so-called nodes). When this phenomenon occurs, the frequency, phase and attenuation coefficient of the wave at the place of reflection are extremely important. Unlike traveling waves, there is no energy transfer in a standing wave due to the fact that the forward and backward waves that form this wave transfer energy in equal quantities in both the forward and opposite directions. To clearly understand the occurrence of a standing wave, let’s imagine an example from home acoustics. Let's say we have floor-standing speaker systems in some limited space (room). Having them play something with a lot of bass, let's try to change the location of the listener in the room. Thus, a listener who finds himself in the zone of minimum (subtraction) of a standing wave will feel the effect that there is very little bass, and if the listener finds himself in a zone of maximum (addition) of frequencies, then the opposite effect of a significant increase in the bass region is obtained. In this case, the effect is observed in all octaves of the base frequency. For example, if the base frequency is 440 Hz, then the phenomenon of “addition” or “subtraction” will also be observed at frequencies of 880 Hz, 1760 Hz, 3520 Hz, etc.

Resonance phenomenon

Most solids have a natural resonance frequency. It is quite easy to understand this effect using the example of an ordinary pipe, open at only one end. Let's imagine a situation where a speaker is connected to the other end of the pipe, which can play one constant frequency, which can also be changed later. So, the pipe has its own resonance frequency, in simple terms - this is the frequency at which the pipe “resonates” or makes its own sound. If the frequency of the speaker (as a result of adjustment) coincides with the resonance frequency of the pipe, then the effect of increasing the volume several times will occur. This happens because the loudspeaker excites vibrations of the air column in the pipe with a significant amplitude until the same “resonant frequency” is found and the addition effect occurs. The resulting phenomenon can be described as follows: the pipe in this example “helps” the speaker by resonating at a specific frequency, their efforts add up and “result” in an audible loud effect. Using the example of musical instruments, this phenomenon can be easily seen, since the design of most instruments contains elements called resonators. It is not difficult to guess what serves the purpose of enhancing a certain frequency or musical tone. For example: a guitar body with a resonator in the form of a hole mating with the volume; The design of the flute tube (and all pipes in general); The cylindrical shape of the drum body, which itself is a resonator of a certain frequency.

Frequency spectrum of sound and frequency response

Since in practice there are practically no waves of the same frequency, it becomes necessary to decompose the entire sound spectrum of the audible range into overtones or harmonics. For these purposes, there are graphs that display the dependence of the relative energy of sound vibrations on frequency. This graph is called a sound frequency spectrum graph. Frequency spectrum of sound There are two types: discrete and continuous. A discrete spectrum plot displays individual frequencies separated by blank spaces. The continuous spectrum contains all sound frequencies at once.
In the case of music or acoustics, the usual graph is most often used Amplitude-Frequency Characteristics(abbreviated as "AFC"). This graph shows the dependence of the amplitude of sound vibrations on frequency throughout the entire frequency spectrum (20 Hz - 20 kHz). Looking at such a graph, it is easy to understand, for example, the strengths or weaknesses of a particular speaker or acoustic system as a whole, the strongest areas of energy output, frequency dips and rises, attenuation, and also to trace the steepness of the decline.

Propagation of sound waves, phase and antiphase

The process of propagation of sound waves occurs in all directions from the source. The simplest example to understand this phenomenon is a pebble thrown into water.
From the place where the stone fell, waves begin to spread across the surface of the water in all directions. However, let’s imagine a situation using a speaker in a certain volume, say a closed box, which is connected to an amplifier and plays some kind of musical signal. It is easy to notice (especially if you apply a powerful low-frequency signal, for example a bass drum) that the speaker makes a rapid movement “forward”, and then the same rapid movement “backward”. What remains to be understood is that when the speaker moves forward, it emits a sound wave that we hear later. But what happens when the speaker moves backward? And paradoxically, the same thing happens, the speaker makes the same sound, only in our example it propagates entirely within the volume of the box, without going beyond its limits (the box is closed). In general, in the above example one can observe quite a lot of interesting physical phenomena, the most significant of which is the concept of phase.

The sound wave that the speaker, being in the volume, emits in the direction of the listener is “in phase”. The reverse wave, which goes into the volume of the box, will be correspondingly antiphase. It remains only to understand what these concepts mean? Signal phase– this is the sound pressure level at the current moment in time at some point in space. The easiest way to understand the phase is by the example of the reproduction of musical material by a conventional floor-standing stereo pair of home speaker systems. Let's imagine that two such floor-standing speakers are installed in a certain room and play. In this case, both acoustic systems reproduce a synchronous signal of variable sound pressure, and the sound pressure of one speaker is added to the sound pressure of the other speaker. A similar effect occurs due to the synchronicity of signal reproduction from the left and right speakers, respectively, in other words, the peaks and troughs of the waves emitted by the left and right speakers coincide.

Now let’s imagine that the sound pressures still change in the same way (have not undergone changes), but only now they are opposite to each other. This can happen if you connect one speaker system out of two in reverse polarity ("+" cable from the amplifier to the "-" terminal of the speaker system, and "-" cable from the amplifier to the "+" terminal of the speaker system). In this case, the opposite signal will cause a pressure difference, which can be represented in numbers as follows: the left speaker will create a pressure of “1 Pa”, and the right speaker will create a pressure of “minus 1 Pa”. As a result, the total sound volume at the listener's location will be zero. This phenomenon is called antiphase. If we look at the example in more detail for understanding, it turns out that two speakers playing “in phase” create identical areas of air compaction and rarefaction, thereby actually helping each other. In the case of an idealized antiphase, the area of ​​compressed air space created by one speaker will be accompanied by an area of ​​rarefied air space created by the second speaker. This looks approximately like the phenomenon of mutual synchronous cancellation of waves. True, in practice the volume does not drop to zero, and we will hear a highly distorted and weakened sound.

The most accessible way to describe this phenomenon is as follows: two signals with the same oscillations (frequency), but shifted in time. In view of this, it is more convenient to imagine these displacement phenomena using the example of an ordinary round clock. Let's imagine that there are several identical round clocks hanging on the wall. When the second hands of this watch run synchronously, on one watch 30 seconds and on the other 30, then this is an example of a signal that is in phase. If the second hands move with a shift, but the speed is still the same, for example, on one watch it is 30 seconds, and on another it is 24 seconds, then this is a classic example of a phase shift. In the same way, phase is measured in degrees, within a virtual circle. In this case, when the signals are shifted relative to each other by 180 degrees (half a period), classical antiphase is obtained. Often in practice, minor phase shifts occur, which can also be determined in degrees and successfully eliminated.

Waves are plane and spherical. A plane wave front propagates in only one direction and is rarely encountered in practice. A spherical wavefront is a simple type of wave that originates from a single point and travels in all directions. Sound waves have the property diffraction, i.e. ability to go around obstacles and objects. The degree of bending depends on the ratio of the sound wavelength to the size of the obstacle or hole. Diffraction also occurs when there is some obstacle in the path of sound. In this case, two scenarios are possible: 1) If the size of the obstacle is much larger than the wavelength, then the sound is reflected or absorbed (depending on the degree of absorption of the material, the thickness of the obstacle, etc.), and an “acoustic shadow” zone is formed behind the obstacle. . 2) If the size of the obstacle is comparable to the wavelength or even less than it, then the sound diffracts to some extent in all directions. If a sound wave, while moving in one medium, hits the interface with another medium (for example, an air medium with a solid medium), then three scenarios can occur: 1) the wave will be reflected from the interface 2) the wave can pass into another medium without changing direction 3) a wave can pass into another medium with a change in direction at the boundary, this is called “wave refraction”.

The ratio of the excess pressure of a sound wave to the oscillatory volumetric velocity is called wave resistance. In simple words, wave impedance of the medium can be called the ability to absorb sound waves or “resist” them. The reflection and transmission coefficients directly depend on the ratio of the wave impedances of the two media. Wave resistance in a gaseous medium is much lower than in water or solids. Therefore, if a sound wave in air strikes a solid object or the surface of deep water, the sound is either reflected from the surface or absorbed to a large extent. This depends on the thickness of the surface (water or solid) on which the desired sound wave falls. When the thickness of a solid or liquid medium is low, sound waves almost completely “pass”, and vice versa, when the thickness of the medium is large, the waves are more often reflected. In the case of reflection of sound waves, this process occurs according to a well-known physical law: “The angle of incidence is equal to the angle of reflection.” In this case, when a wave from a medium with a lower density hits the boundary with a medium of higher density, the phenomenon occurs refraction. It consists in the bending (refraction) of a sound wave after “meeting” an obstacle, and is necessarily accompanied by a change in speed. Refraction also depends on the temperature of the medium in which reflection occurs.

In the process of propagation of sound waves in space, their intensity inevitably decreases; we can say that the waves attenuate and the sound weakens. In practice, encountering a similar effect is quite simple: for example, if two people stand in a field at some close distance (a meter or closer) and start saying something to each other. If you subsequently increase the distance between people (if they begin to move away from each other), the same level of conversational volume will become less and less audible. This example clearly demonstrates the phenomenon of a decrease in the intensity of sound waves. Why is this happening? The reason for this is various processes of heat exchange, molecular interaction and internal friction of sound waves. Most often in practice, sound energy is converted into thermal energy. Such processes inevitably arise in any of the 3 sound propagation media and can be characterized as absorption of sound waves.

The intensity and degree of absorption of sound waves depends on many factors, such as pressure and temperature of the medium. Absorption also depends on the specific sound frequency. When a sound wave propagates through liquids or gases, a friction effect occurs between different particles, which is called viscosity. As a result of this friction at the molecular level, the process of converting a wave from sound to heat occurs. In other words, the higher the thermal conductivity of the medium, the lower the degree of wave absorption. Sound absorption in gaseous media also depends on pressure (atmospheric pressure changes with increasing altitude relative to sea level). As for the dependence of the degree of absorption on the frequency of sound, taking into account the above-mentioned dependences of viscosity and thermal conductivity, the higher the frequency of sound, the higher the absorption of sound. For example, at normal temperature and pressure in air, the absorption of a wave with a frequency of 5000 Hz is 3 dB/km, and the absorption of a wave with a frequency of 50,000 Hz will be 300 dB/m.

In solid media, all the above dependencies (thermal conductivity and viscosity) are preserved, but several more conditions are added to this. They are associated with the molecular structure of solid materials, which can be different, with its own inhomogeneities. Depending on this internal solid molecular structure, the absorption of sound waves in this case can be different, and depends on the type of specific material. When sound passes through a solid body, the wave undergoes a number of transformations and distortions, which most often leads to the dispersion and absorption of sound energy. At the molecular level, a dislocation effect can occur when a sound wave causes a displacement of atomic planes, which then return to their original position. Or, the movement of dislocations leads to a collision with dislocations perpendicular to them or defects in the crystal structure, which causes their inhibition and, as a consequence, some absorption of the sound wave. However, the sound wave can also resonate with these defects, which will lead to distortion of the original wave. The energy of the sound wave at the moment of interaction with the elements of the molecular structure of the material is dissipated as a result of internal friction processes.

In this article I will try to analyze the features of human auditory perception and some of the subtleties and features of sound propagation.

Recently, there has been a lot of debate about the dangers and benefits of wind generators from an environmental point of view. Let's consider several positions that are primarily cited by opponents of wind energy.

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 of interest to 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, then 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 strip

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, and 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.

The idea of ​​singing water came to the minds of the medieval Japanese hundreds of years ago and reached its peak by the mid-19th century. Such an installation is called “shuikinkutsu”, which loosely translated means “water harp”:

According to the video, shukinkutsu is a large empty vessel, usually installed in the ground on a concrete base. There is a hole in the top of the vessel through which water drips inside. A drainage tube is inserted into the concrete base to drain excess water, and the base itself is made slightly concave so that there is always a shallow puddle on it. The sound of the drops reflects off the walls of the vessel, creating a natural reverberation (see picture below).

Shuikinkutsu in section: a hollow vessel on a concave concrete base at the top, a drainage tube to drain excess water, a backfill of stones (gravel) at the base and around it.

Shuikinkutsu have traditionally been an element of Japanese garden design and rock gardens in the spirit of Zen. In the old days, they were placed on the banks of streams near Buddhist temples and houses for the tea ceremony. It was believed that after washing one’s hands before the tea ceremony and hearing magical sounds from underground, a person tunes into an elevated mood. The Japanese still believe that the best, purest-sounding shuikinkutsu should be made from solid stone, although this requirement is not observed these days.
By the middle of the twentieth century, the art of constructing shuikinkutsu was almost lost - only a couple of shuikinkutsu remained throughout Japan, but in recent years interest in them has experienced an extraordinary rise. Today they are made from more affordable materials - most often from ceramic or metal vessels of a suitable size. The peculiarity of the sound of shuikinkutsu is that in addition to the main tone of the drop inside the container, due to the resonance of the walls, additional frequencies (harmonics) arise, both above and below the main tone.
In our local conditions, you can create shuikinkutsu in different ways: not only from a ceramic or metal container, but also, for example, by laying it directly in the ground from red brick along method of making Eskimo igloos or cast from concrete according to t technology for creating bells– these options will sound closest to all-stone shuikinkutsu.
In the budget version, you can get by with a piece of large-diameter steel pipe (630 mm, 720 mm), covered at the top end with a lid (thick metal sheet) with a hole for water drainage. I would not recommend using plastic containers: plastic absorbs some sound frequencies, and in shuikinkutsu you need to achieve their maximum reflection from the walls.
Prerequisites:
1. the entire system must be completely hidden underground;
2. The base and filling of the side sinuses must be made of stone (crushed stone, gravel, pebbles) - filling the sinuses with soil will negate the resonant properties of the container.
It is logical to assume that the height of the vessel—more precisely, its depth—is of decisive importance in the installation: the faster a drop of water accelerates in flight, the louder its impact on the bottom will be, the more interesting and fuller the sound will be. But there is no need to reach the point of fanaticism and build a missile silo - a height of the container (a piece of metal pipe) of 1.5-2.5 times the size of its diameter is quite sufficient. Please note that the wider the volume of the container, the lower the sound of the main tone of the shuikinkutsu will be.
Physicist Yoshio Watanabe studied the characteristics of the reverberation of suikinkutsu in the laboratory; his study “Analytic Study of Acoustic Mechanism of “Suikinkutsu”” is freely available on the Internet. For the most meticulous readers, Watanabe offers, in his opinion, the optimal dimensions of traditional shukinkutsu: a ceramic vessel with a wall 2 cm thick, bell-shaped or pear-shaped, a free drop height of 30 to 40 cm, a maximum internal diameter of about 35 cm. But the scientist fully allows any arbitrary dimensions and shapes.
You can experiment and get interesting effects if you make a shuikinkutsu like a pipe within a pipe: insert a pipe of a smaller diameter (630 mm) and a slightly smaller height inside a steel pipe of a larger diameter (for example, 820 mm), and additionally cut several holes in the walls of the inner pipe at different heights with a diameter of approximately 10-15 cm. Then the empty gap between the pipes will create additional reverberation, and if you are lucky, then an echo.
A lightweight option: during pouring, insert a pair of thick metal plates 10-15 centimeters wide and a height higher than half the internal volume of the container vertically and slightly at an angle into the concrete base - due to this, the area of ​​the internal surface of the shukinkutsu will increase, additional sound reflections will arise, and, accordingly, a little The reverberation time will increase.
You can modernize the shuikinkutsu even more radically: if you hang bells or carefully selected metal plates in the lower part of the container along the axis of falling water, then you can get a euphonious sound from the drops hitting them. But keep in mind that in this case the idea of ​​shuikinkutsu, which is to listen to the natural music of water, is distorted.
Now in Japan, shuikinkutsu is performed not only in Zen parks and private properties, but even in cities, in offices and restaurants. To do this, a miniature fountain is installed near the shuikinkutsu, sometimes one or two microphones are placed inside the vessel, then their signal is amplified and fed to speakers disguised nearby. The result looks something like this:

A good example to follow.

Shuikinkutsu enthusiasts have released a CD containing recordings of various Shuikinkutsu created in different parts of Japan.
The idea of ​​shuikinkutsu found its development on the other side of the Pacific Ocean:

This American “wave organ” is based on conventional long-length plastic pipes. Installed with one edge exactly at the level of the waves, the pipes resonate from the movement of water and, due to their bending, also act as a sound filter. In the Shukinkutsu tradition, the entire structure is hidden from view. The installation is already included in tourist guides.
The next British device is also made from plastic pipes, but is not intended to generate sound, but to change an existing signal.
The device is called the Organ of Corti and consists of several rows of hollow plastic pipes fixed vertically between two plates. Rows of pipes act as a natural sound filter similar to those installed in synthesizers and guitar “gadgets”: some frequencies are absorbed by the plastic, others are repeatedly reflected and resonate. As a result, the sound coming from the surrounding space is transformed randomly:

It would be interesting to put such a device in front of a guitar amp or any speaker system and listen to how the sound changes. Truly, “...everything around is music. Or he can become one with the help of microphones” (American composer John Cage). …I’m thinking of creating a shuikinkutsu in my country this summer. With lingam.