Noise - This is a combination of sounds of different frequency and intensity (forces) arising from the oscillatory movement of particles in elastic media (solid, liquid, gaseous).
The process of propagation of the oscillatory movement in the medium is called a sound wave, and the area of \u200b\u200bthe medium in which sound waves are applied - the sound field.
Distinguish shock, mechanical, aerohydrodynamic noise. Impact noise occurs when stamping, riveting, forging, etc.
Mechanical noise There occurs with the friction and bias of the nodes and parts of machines and mechanisms (crushers, mills, electric motors, compressors, pumps, centrifuges, etc.).
Aerodynamic noise It occurs in devices and pipelines at high speeds of air, gas or liquid and with sharp changes in the direction of their movement and pressure.
The main physical characteristics of the sound:
- Frequency F (Hz),
- sound pressure P (PA),
- intensity or sound strength i (W / m2),
- Sound power? (W).
Speed \u200b\u200bSpeed \u200b\u200bWave Speed In the atmosphere at 20 ° C is 344 m / s.
Human hearing organs perceive sound oscillations in the frequency range from 16 to 20,000 Hz. The fluctuations with a frequency below 16 Hz (infrasonic) and with a frequency above 20,000 (ultrasound) are not perceived by hearing organs.
When the sound of sound oscillations in the air periodically appear areas of the permit and increased pressure. The pressure difference in the perturbed and unperturbed media is called sound pressure P, which is measured in Pascal (PA).
The propagation of the sound wave is accompanied by energy transfer. The amount of energy carried by the sound wave per unit of time through the surface unit oriented perpendicular to the direction of the wave propagation is called the intensity or power of sound I and is measured in W / m 2.
The work is called the specific acoustic resistance of the medium, which characterizes the degree of reflection of sound waves during the transition from one medium to another, as well as the soundproofing properties of materials.
Minimum sound intensitywhich is perceived by the ear is called the threshold of hearing. As a standard comparison frequency, a frequency of 1000 Hz is adopted. With this frequency, the threshold of hearing I 0 \u003d 10-12 W / m 2, and the corresponding sound pressure p 0 \u003d 2 * 10 -5 pa. Maximum sound intensityin which the hearing body begins to experience a painful feeling called the threshold painful feelingequal to 10 2 W / m 2, and the corresponding sound pressure p \u003d 2 * 10 2 pa.
Since changes in the intensity of sound and sound pressure of hearing people are huge and constitute 10 14 and 10 and 10 times, respectively, to use the absolute values \u200b\u200bof the intensity of sound or sound pressure are extremely uncomfortable.
For the hygienic assessment of noise, it is customary to measure its intensity and sound pressure not with absolute physical quantities, but logarithms of these values \u200b\u200bto a conditional zero level corresponding to the threshold of the standard tone of a frequency of 1000 Hz. These logarithms of relations are called intensity and sound pressure levels expressed in Belarus (b). Since the human hearing body is able to distinguish the change in the level of sound intensity by 0.1 Bela, then for practical use it is more convenient than one 10 times less - decibel (dB).
The level of intensity of the sound L in decibels is determined by the formula

L \u003d 10LG (I / I O) .

Since the intensity of the sound is proportional to the square of the sound pressure, then this formula can also be written as ^

L \u003d 10LG (P 2 / P O 2) \u003d 20LG (P / P O), dB.

The use of a logarithmic scale for measuring the noise level allows you to lay a large range of values \u200b\u200bI and P in a relatively small range of logarithmic values \u200b\u200bfrom 0 to 140 dB.
Sound pressure threshold P 0 corresponds to the threshold of hearing l \u003d 0 dB, the threshold of the painful sensation is 120-130 dB. Noise, even when it is small (50-60 dB) creates a significant burden on the nervous system, providing a psychological impact. Under the action of noise, more than 140-145 dB is possible a breakpatch breakpoint.
Summer sound pressure L created by multiple sound sources with the same Li sound pressure level, calculated by the formula

L \u003d L i + 10lg n. , dB,

where n is the number of noise sources with the same sound pressure level.
For example, if the noise creates two identical noise sources, then their total noise is 3 dB more than each of them separately.
In terms of the intensity of the sound, it is still impossible to judge the physiological sensation of this sound, since our hearing body is not very sensitive to the sounds of different frequencies; Sounds are equal in force, but of different frequencies, it seems unequal loud. For example, the sound of a frequency of 100 Hz and a force of 50 dB is perceived as an equal sound with a frequency of 1000 Hz and a force of 20 dB. Therefore, to compare the sounds of different frequencies, along with the concept of the intensity level of the sound, the concept of volume level with a conditional unit is introduced - background. One background is the sound volume at a frequency of 1000 Hz and the level of intensity in 1 dB. At the frequency of 1000 Hz, the volume levels are taken with equal sound pressure levels.
In fig. 1 shows the curves of equal volume of sounds obtained according to the results of the study of the properties of the hearing body to estimate the sounds of different frequencies on a subjective sensation of volume. From the graph, it can be seen that our ear has the greatest sensitivity of 800-4000 Hz, and the smallest - at 20-100 Hz.

Typically, noise and vibration parameters are estimated in octave bands. Oktawa is accepted for the bandwidth, i.e. The frequency interval in which the highest frequency F 2 is twice as much lower F 1. As a frequency characterizing the band as a whole, the medium meterometric frequency is taken. Medium meterometric frequencies of octave stripes Standardized GOST 12.1.003-83 " Noise. General safety requirements"and make up 63, 125, 250, 500, 1000, 2000, 4000 and 8000 Hz with the corresponding boundary frequencies of 45-90, 90-180, 180-355, 3,55-710, 710-1400, 1400-2800, 2800- 5600, 5600-11200.
The dependence of the values \u200b\u200bcharacterizing the noise from its frequency is called the frequency spectrum of noise. For the convenience of the physiological assessment of the effects of noise per person, low-frequency (up to 300 Hz), mid-frequency (300-800 Hz) and high-frequency (above 800 Hz) noise are distinguished.
GOST 12.1.003-83 and CH 9-86 RB 98 " Noise in workplaces. Extremely permissible levels "Classifies the noise by the character of the spectrum and the time of action.
By the nature of the spectrum:
- broadband, if it has a continuous spectrum of more than one octave width,
-Tone, if there are pronounced discrete tones in the spectrum. In this case, the tonal nature of noise for practical purposes is set to measurement in the third-rigging bands of the frequency (for the third-string band to pre-void the sound pressure level in one band above the adjacent no less than 10 dB.
By temporary characteristics:
- permanent, whose sound level for 8-hour work is changing in time no more than 5 dB,
- a non-permanent, the sound level of which for the 8-hour Ra-Bochy day varies in time by more than 5 dB.
Non-permanent noises are divided into:
fluctant in time, the sound level of which continuously changes in time;
intermittent, the sound level of which stepwise changes (5 dB or more);
pulse, consisting of one or more audible signals, each duration less than 1 s.
The greatest danger to humans are the on-mall, high-frequency and non-permanent noises.
Ultrasound according to the distribution method is divided into:
- distributed airway (air ultrasound);
- propagated by contact path with solid and liquid environments (contact ultrasound).
Ultrasonic frequency range is divided into:
- low-frequency oscillations (1.12 * 10 4 - 1 * 10 5 Hz);
- High-frequency (1 * 10 5 - 1 * 10 9 Hz).
Sources of ultrasound is the production equipment in which ultrasound fluctuations are generated to perform the technological process, technical control and measurement, as well as equipment, during the operation of which ultrasound occurs as an accompanying factor.
Characteristic of air ultrasoundin the workplace in accordance with GOST 12.1.001 " Ultrasound. General safety requirements"and CH 9-87 RB 98" Ultrasound transmitted by air. Maximum permissible levels on workplaces"There are levels of sound pressure in third-party stripes with medium-meter frequencies 12.5; 16.0; 20.0; 25.0; 31.5; 40.0; 50.00; 63.0; 80.0; 100.0 kHz.
Characteristic of contact ultrasound In accordance with GOST 12.1.001 and CH 9-88 RB 98 " Ultrasound transmitted by contact path. Maximum permissible levels on workplaces"There are peak values \u200b\u200bof vibration and vibrational levels in octave bands with medium-meter frequencies 8; 16; 31.5; 63; 125; 250; 500; 1000; 2000; 4000; 8000; 16000; 31500 kHz.
Vibration - These are the oscillations of solid bodies - parts of the apparatuses, machinery, equipment, structures, perceived by the human body as concussion. Often vibrations are accompanied by audible noise.
According to the method of transmission per person Vibration is divided by lAN and General.
The total vibration is transmitted through the supporting surfaces on the body of the standing or sitting person. The most dangerous frequency of general vibration lies in the range of 6-9 Hz, since it coincides with its own frequency of oscillations of the internal organs of a person, as a result of which resonance may occur.
Local (local) vibration Transmitted through man's hands. The vibration acting on the legs of a seated person and on the forearm in contact with the vibrating surfaces of desktops can be attached to the local vibration.
Sources of local vibration transmitted on working, can be: manual machines with a motor or a manual mechanized tool; controls of machinery and equipment; Hand tools and processed parts.
Total vibration Depending on the source of its occurrence, it is divided into:
the total vibration of the category 1 is a transport, affecting person in the workplace in self-propelled and trailed machines, vehicles when driving around the terrain, roads and agrofons;
the total vibration of the category 2 is a transport and technological, affecting a person in workplaces in machines moving on specially prepared surfaces of industrial premises, industrial sites, mining workings;
the total vibration of 3 categories is a technological, affecting person in the workplace in stationary cars or transmitted to jobs that do not have vibration sources.
The total vibration of category 3 at the place of action is divided into the following types:
3A - at permanent workplaces of industrial premises of enterprises;
3B - in workplaces in warehouses, in the canteens, household, duty and other auxiliary industrial premises, where there are no cars generating vibration;
3B - in workplaces in administrative and official premises of plant management, design bureaus, laboratories, training points, computing centers, health care, office premises and other premises of mental work workers.
According to temporary characteristics, vibration is divided into:
- permanent, for which spectral or frequency corrected by the normalized parameter during observation (at least 10 minutes or the time of the technological cycle) changes no more than 2 times (6 dB) when measuring with a time constant 1 s;
- non-permanent vibration, for which spectral or frequency corrected normalized parameter during observation (at least 10 minutes or time of the technological cycle) varies more than 2 times (6 dB) when measured with a time constant 1 s.
The main parameters characterizing vibration:
- Frequency F (Hz);
- the amplitude of the displacement A (M) (the magnitude of the greatest-blonde of the oscillating point from the equilibrium position);
- oscillatory speed V (m / s); oscillatory acceleration A (m / s 2).
As for noise, the entire spectrum of frequencies of vibrations, re-accepted by a person, is divided into octave bands with medium meterometric frequencies 1, 2, 4, 8, 16, 32, 63, 125, 250, 500, 1000, 2000 Hz.
Since the range of changes in vibration parameters from threshold values, under which it is not dangerous, to real - large, it is more convenient to measure the invalid values \u200b\u200bof these parameters, and the logarithm of the actual values \u200b\u200bto the thresholds. Such a magnitude is called the logarithmic level of the parameter, and the unit of its measurement is decibel (dB).

Physiological characteristics Sounds are called the subjective characteristics of the auditory sensation of sound by a human hearing aid. The physiological characteristics of the sound refers to the minimum and maximum frequency of oscillations perceived by this person, the threshold of hearing and threshold of the pain, volume, height, sound timbre.

1. The minimum and maximum frequency of oscillations perceived by this person. The frequencies of the sounds are in the range of 20-20000 Hz. However, the smallest perceived frequency by this person is usually greater than 20 Hz, and the greatest - less than 20,000 Hz, which is determined by the individual characteristics of the structure. humorcraft man. For instance: n min \u003d 32 Hz, N Max \u003d 17900 Hz.

2. Threshold hearingness called the minimum intensity perceived by the human ear I O.. It is considered that I o \u003d 10 -12 W / m 2 for n \u003d 1000 Hz. However, usually for a particular person the threshold of hearing more I O..

The threshold of hearing depends on the frequency of sound oscillation. At some frequency (usually 1000-3000 Hz), depending on the length of the auditory channel of the human hearing aid, there is a resonant increase in sound in the human ear. In this case, the feeling of sound will be the best, and the threshold of hearing will be minimal. When the oscillation frequency is reduced or increasing the resonance condition deteriorates (removal by frequency from the resonant frequency) and the hearing threshold increases accordingly.

3. Threshold of pain called the painful feeling of the painful feeling with the intensities of sound above some value I pore(The sound wave at the same time as the sound is not felt). Threshold of painful feeling I pore It depends on the frequency (albeit to a lesser extent than the threshold of hearingness). At low I. high frequencies The threshold of pain is reduced, i.e. Pain sensations are observed at large intensities.

4. Volume sound It is called the level of auditory sensation by a person of this sound. The volume depends primarily from a person who perceives sound. For example, with sufficient intensity at a frequency of 1000 Hz, the volume can be equal to zero (for a deaf person).

For a given specific person, perceiving sound, the volume depends on the frequency, the intensity of the sound. As for the threshold of hearing, the volume is maximum usually at a frequency of 1-3 kHz, and with a decrease or increasing frequency, the volume is reduced.

The volume of the sound depends on the intensity of the sound complex. In accordance with the psychophysical law Weber-Ferehner Volume E. Directly proportional to the level of intensity:

E \u003d K. . LG (I / I 0), Where k. Depends on the frequency and intensity of the sound.

Sound volume is measured in floors. It is believed that the volume in the backgrounds is numerically equal to the level of intensity in decibels at frequency 1000 Hz. For example, the volume of sound E \u003d 30 background; This means that this person in terms of perception feels the specified sound as well as the sound, frequency 1000 Hz and sound strength 30 dB.. Graphically (see tutorial) build curves of equal volume, which are individual for each particular person.

In order to diagnose the state of the human hearing aid using an audiometer, remove audiogram - The dependence of the threshold of hearing frequency.

5. Sound height called the sensation of a man of pure tone. The tone height increases with increasing frequency. With an increase in intensity, the height of the tone is slightly reduced.

6. Temmbra sound It is called a sense of a person of this complex sounding. Sound timbre is color Sound, according to which we distinguish the voice of a person. The timbre depends on the acoustic spectrum of sound. However, the same acoustic spectrum is perceived by various people in different ways. So, if two people have a hearing apparatus, and leave the brain analyzer sound the same, then the color of the sound from people familiar to him will seem another, i.e. He may not know the voice of a person or voice will seem modified.

Task on UIRS

1. To learn from the textbooks the device of the hearing aid, the theory of sound perception and the physical foundations of sound research methods in the clinic.

2. Find the sound volume in the backgrounds, if there is a sound oscillation with a frequency of 50 Hz and the level of power of 100 dB.

Procedure for performing work

Exercise number 1. Determining the most perceived sound frequency you

(The minimum perceived frequency with this sound generator cannot be determined due to the passage of the headphones interference mainly from a frequency of 50 Hz.)

Put the switches to the following position:

-Tubler network - in position " OFF";

-frequency factor (left below) to the position " 100 ";

- "output resistance"To position" 50 ";

Switches dozens and units of decibel to the position " 0 ".

Turn on the plug of the network cord of the generator in the network 220 V, toggle switch " network"Put in the Regulation" Incl": Headphones Connect to the generator output.

Handle adjustment output voltage " Reg. out"Put on a voltmeter 20 V.

Check the frequency of 20,000 Hz (frequency limb to position

200 Hz and frequency multiplier stands in the position "100", i.e. 200 Hz × 100 \u003d 20 000 Hz).

Smoothly reducing the frequency, determine this value at which hear the sound. Write down its value. This is the top boundary frequency you are perceived ( ν 1 Top).

To clarify this boundary, increase the frequency from 10,000 Hz to the disappearance of the sound, defining the second value of the upper boundary frequency ν 2 Top.

The value of the top boundary frequency you are perceived, as the arithmetic average of the two frequency values \u200b\u200bobtained: ν Upper \u003d (ν 1 Top + ν 2 Top) / 2.

Exercise number 2.. Determining the dependence of the threshold of hearing frequency

Conduct measurements at the following frequencies: 50, 100, 200, 400, 1000, 2000, 4000 and 8000 Hz. For the initial level, take such a sound intensity at a frequency of 1000 Hz (when attenuation of 0 dB), at which the sound volume does not cause you unpleasant sensations.

Put the frequency of 50 Hz, the switch of dozens of decibel to achieve the disappearance of the sound, then reduce the attenuation by 10 dB and the knob of the Decibel unit to enter the attenuation before the sound disappears. Record the result in Table 1.

Table 1

Physical and physiological characteristics of sound.

Physical and physiological characteristics of sound. Chart of hearingness. Intensity levels and sound volume levels, the connection between them and the units of their measurement.
Acoustics - a section of physics in which the sound and related phenomena are studying. The sound is a longitudinal mechanical wave, which extends to elastic media (solid bodies, liquids and gases) and is perceived by the human ear. The sound corresponds to the frequency range from 16 Hz to 20000 Hz. Frequency oscillations\u003e 20000Hz - ultrasound, and< 16Гц – инфразвук. В газах звуковая волна – только продольная, в жидкостях и твёрдых телах – продольная и поперечная. Человек слышит только продольную механическую волну. Скорость звука в среде зависит от св-в среды (температуры, плотности среды и т.д.). В воздухе =340м/с; в жидкостях и кровенаполненных тканях = 1500м/c; в твердых телах =3000-5000м/c. Для твёрдых тел скорость равна: v=√E/p, где Е – модуль упругости (Юнга); р – плотность тела. Для воздуха скорость (м/с) возрастает с увеличением температуры: м=331,6+0,6t. Звуки делятся на тоны (простые и сложные), шумы и звуковые удары. Простой (чистый) тон – звук, источник которого совершает гармонические колебания (камертон). Простой тон имеет только одну частоту v.Сложный тон – звук, источник которого совершает периодические негармонические колебания (муз. звуки, гласные звуки речи), можно разложить на простые тона по т. Фурье. Спектр сложного тона линейчатый. Шум – сочетание беспорядочно меняющихся сложных тонов, спектр – сплошной. Звуковой удар – кратковременное звуковое воздействие (взрыв, хлопок). Различают объективные (физические), характеризующие источник звука, и субъективные (физиологические), характеризующие приёмник (ухо). Физиологические характеристики зависят от физических. Интенсивность I (Вт/м2) или уровень интенсивности L (дБ)– энергия звуковой волны, приходящаяся на площадку единичной площади за единицу времени. Эта физическая характеристика определяет уровень слухового ощущения (громкость Е [фон], уровень громкости). Громкость показывает уровень слухового ощущения. Гармонический спектр – тембр звука. Частота звука v (Гц) – высота звука. Порог слышимости – min интенсивность I0, которую человек ещё слышит, но ниже которого звук ухом не воспринимается. Человек лучше слышит на частоте 1000Гц, значит порог слышимости на этой частоте min (I0=Imin) и I0=10-12Вт/м2. Порог болевого ощущения – max интенсивность, воспринимаемая без болевых ощущений. При I0>Imax occurs damage to the hearing body. IMAX \u003d 10W / M2. The concept of the intensity levels L \u003d LGI / I0 is introduced, where I0 is the intensity of sound on the threshold of hearingness. [B - BELAX]. 1 Bel is the level of intensity of such sound, the intensity of which is 10 times\u003e threshold intensity. 10DB \u003d 1B. L \u003d 10LGI / I0, (dB). A person hears sounds in the range of sound intensity levels from 0 to 130 dB. The audibility diagram is the dependence of the intensity or the level of intensity from the sound frequency. On it, the threshold (BP) and the threshold of hearing (PS) are presented in the form of curves, do not depend on the frequency. MIN Threshold of hearing 10-12 W / m2, and the pain threshold imax \u003d 1-10W / m2. These values \u200b\u200bat a frequency of 1000 Hz. Near this frequency, a person hears best. Therefore, in the frequency range of 500-3000 Hz with intensity 10-8-10-5W / m2 - the area of \u200b\u200bspeech. (I, W / m2: 10, 1, 10-12, empty; V, Hz: 16, 1000, 20000; L, dB: 130, 120.0). Audiometry is a method for studying the hearing acuteness using the hearing chart. The sound sensation (volume) grows in arithmetic progression, and intensity - in geometric. E \u003d KLGI. Weber-Ferehner law: Changing the volume is directly proportional to the LG intensity ratio of the sounds that caused this volume change: ΔE \u003d k1lgi2 / i1, where k1 \u003d 10k.
Active transport of ions through the membrane. Types of ionic processes. Principles of operation Na + -K + pump.
Active transport - the transfer of molecules and ions through the membrane, which is performed by the cell due to the energy of metabolic processes. It leads to an increase in the potential difference on both sides of the membrane. In this case, the transfer of BA is carried out from the region of its lower concentration to the region greater. Energy to perform work is obtained when splitting aTF molecules On ADP and phosphate group under the action of specials. Proteins - Enzymes - Transport ATP-Ase. ATP \u003d ADF + F + E, E \u003d 45CH / mol. Active transport: ions (Na + -K + -TF-AZA; Ca2 + -atf-Aza; N + -TF-Aza; proton transfer when working. Mitochondria chains) and organic in-in. Sodium-potassium pump. Under the action of Na + in cytoplasm, on the inner side of the membrane, the transport ATP-AZA is activated and splits to ADP and F. At the same time, 45KJ / mol of energy extended to attach three Na + and change due to this conformation of ATP-Ase. 3 Na + is transferred through the membrane. To return to the initial conformation, ATP-AZ has to be transferred 2k + through the membrane to the cytoplasm. For one cycle from the cell one positive charge is made. The inner side of the cell is a negative charge, external - positive. The separation of electrical charges occurs and an electrical voltage occurs, therefore Na + -K + pump is an isogenic.
Determine the velocity of electrons falling on the anticatode of the X-ray tube if the MIN wavelength in the solid X-ray spectrum is 0.01NM.
eu \u003d hc / lmin; EU \u003d MV2 / 2; HC / LMIN \u003d MV2 / 2; v2 \u003d 2hc / mlmin \u003d 437.1 * 1014m / c; V \u003d 20.9 * 107m / s.
The optical force of the lens is 10 DPTR. What increase does it give?
D \u003d 1 / f; R \u003d d0 / f \u003d 0.25m / 0.1 \u003d 2.5.
Evaluate the hydraulic resistance of the vessel if, at a blood flow rate of 0.2 liters / min (3.3 * 10-6m3 / s), the pressure difference at its ends is 3mm.rt. (399pa, because 760mm.rt.st . \u003d 101kpa)
X \u003d Δp / q \u003d 399 / 3,3 * 10-6 \u003d 121 * 106 PA * C / m3
What equations are called differential, how are its common and private solutions differ?
Differential - equation connecting the argument, the desired function of y and its derivatives in ', y,, ..., yn of various orders. Pro order DIF. The equations are determined by the highest procedure of the derivative included in it. Consider the second law of Newton F \u003d MA, acceleration is the first derivative of speed. F \u003d MDV / DT - DIF. The first order equation. Acceleration is the second derivative of the path. F \u003d MD2S / DT2 - DIF. The second order equation. Decision DIF. The equations are a function that draws this equation into identity. Resolving equation: U'-x \u003d 0; DY / DX \u003d X; dy \u003d xdx; ᶘdy \u003d ᶘxdx; y + c1 \u003d x2 / 2 + c2; Y \u003d X2 / 2 + C is a general solution of DIF. equations. With any particular value of constant with the function, we get a private solution, there may be indefinitely a lot. To select one, you need to set an additional condition.

1. Characteristics of the auditory, their connection with physical

sound characteristics. The dependence of the volume from the frequency.

Weber-Ferehner law.

The sound tone is characterized by a frequency (period), a harmonic spectrum, intensity, or sound strength and sound pressure. All these sound characteristics are physical or objective characteristics. However, the sound is the object of the auditory feeling, therefore, it is estimated by a person subjectively, i.e. The sound has both physiological characteristics that are reflected in its physical characteristics. The task of the sound measurement system is to establish this connection and thus enable the hearing study different people It is uniformly to compare a subjective assessment of the auditory sensation with the data of objective measurements.

The frequency of oscillations of the sound wave is estimated as the height of the sound (tone height). The greater the frequency of oscillations, the more high the sound is perceived.

Another physiological characteristic is the timbre, which is determined by the spectral composition of complex sound. The complex tones of the same basic frequencies may differ in the form of oscillations and, accordingly, according to the harmonious spectrum. This difference is perceived as the timbre (sound color). For example, the ear distinguishes the same melody reproduced on different musical instruments.

Volume - another subjective sound assessment, which characterizes the level of the auditory. It depends first of all, from the intensity and frequency of sound.

Consider first the dependence of the ear sensitivity from the frequency. The human ear is not equally sensitive to different frequencies at the same intensity. The frequency range is perceived by them - 16Hz-20kHz. The ability of a person to perceive high-frequency sounds is worsening with age. A young man can hear sounds with a frequency of up to 20,000 Hz, but at the middle age the same person is not able to perceive sounds with a frequency above 12-14 kHz. Within the frequency of 1,000-3,000 Hz, the sensitivity is the largest. It decreases to the frequencies of 16 Hz and 20 kHz. Obviously, the nature of the change in the threshold of hearingness is treated with the change in the sensitivity of the ear, i.e. With increasing frequency from 16 Hz, it is first reduced, in the frequency range 1000-3000 Hz remains almost unchanged, then rises again. This is reflected in the chart of the dependence of the change in the threshold of hearing frequency (see Fig. 1).

The schedule is built in a logarithmic scale. The upper curve on the graph corresponds to the painful threshold. The lower chart is called the threshold volume curve, i.e. J 0 \u003d F (ν).

The volume of the sound depends on its intensity. It is a subjective sound characteristic. These two concepts are unequal. The loudness dependence on the intensity of sound is complex, due to the sensitivity of the ear to the action of sound waves. A person can only approximately estimate the absolute intensity of the sensation. However, it definitely establishes the difference when comparing two sensations of various intensity. It caused the appearance of a comparative volume of volume measurement. In this case, the absolute amount of volume is measured, but its ratio with some other value, which is accepted for the initial or zero volume level.

In addition, it was agreed when comparing the intensity and volume of sound to proceed from the tone, with a frequency of 1,000 Hz, i.e. Read the volume of tone with a frequency of 1,000 Hz benchmark for volume scales. As already mentioned, the comparative method is used and when measuring the intensity (strength) of sound. Therefore, there are two scales: one to measure intensity levels; The second is to measure the volume levels. The creation of the volume of volume levels is the important psychophysical law of Weber-Ferehner. According to this law, if you increase irritation in geometric progression (that is, in the same number of times), the feeling of this irritation increases in arithmetic progression (on the same value). For example, if the audio intensity takes a number of consecutive values: a J 0, A 2 J 0, A 3 J 0 (A\u003e 1 is some coefficient), then the corresponding volume changes to them will be equal to E 0, 2E 0, 3E 0. Mathematically, this means that the sound volume is directly proportional to the logarithm of intensity.

If the sound irritant is acting with the intensity J, then on the basis of the Weber-Fehener law, the volume level E is associated with the level of intensity as follows:

E \u003d Kl \u003d KLG, (1)

where - the relative force of irritation, K, some proportionality coefficient, depending on the frequency and intensity, adopted equal to one for ν \u003d 1000 Hz. Therefore, if we take K \u003d 1 at all frequencies, then in accordance with the formula (1) we obtain the scale of intensity levels; with ≠ 1 - the volume scale, where the unit of measurement will no longer decibel, but background. Given that at the frequency of 1 kHz, the volume and intensity scales coincide, it means that the e f \u003d 10.

The dependence of the volume from the intensity and frequency of oscillations in the sound measurement system is determined based on the experimental data using graphs that are called equal volume curves, i.e. J \u003d f (ν) at e \u003d const. We have built a curve of the zero volume level or the threshold of hearingness. This curve is the main (zero volume level - e f \u003d 0).

If you build similar curves for different levels of louds, for example, steps through 10 backgrounds, then the graph of graphs will be obtained (Fig. 2), which makes it possible to find the dependence of the intensity level from frequency at any volume level. These curves are built on the basis of medium data, which were obtained in people with normal hearing. The lower curve corresponds to the threshold of hearingness, i.e. For all frequencies e f \u003d 0 (for frequency ν \u003d 1 kHz, the intensity J 0 \u003d W / m 2). The study of hearing acuity is called audiometry. With an audio system on a special instrument, an audiometer is determined by the surveyed threshold of the auditory sensation at different frequencies. The resulting schedule is called an audiogram. Hearing loss is determined by comparing it with a normal threshold curve of hearing.

2. Sound research methods in the clinic.

Sound phenomena accompany a number of processes occurring in the body, for example, the work of the heart, breathing, etc. Direct listening to sounds arising inside the body make up one of the most important techniques of clinical research and are called auscultation (listening). This method is known since the 2nd century BC. e. For this purpose, a stethoscope is used - the device in the form of a straight wooden or plastic tube with a small field at one end and a flat base on the other for applying the ear. The sound from the body surface to the ear is carried out both by the pillar of air and the walls of the tube.

For auscultation use a phonenadoscope consisting of a hollow capsule with a membrane applied to the patient's body. There are two rubber tubes from the capsule, which are inserted into the ears of the doctor. The resonance of the air column in the capsule enhances the sound.

To diagnose the state of the cardiovascular system, the method is used - phonocardiography (FKG) - graphic registration of tones and sound noise with the aim of their diagnostic interpretation. The record is made using a phonocardograph consisting of a microphone, amplifier, frequency filter systems and a recorder device.

The percussion is different from the two methods - the method of studying internal organs by tapping on the body surface and the analysis of sounds arising from this. The nature of these sounds depends on the method of tapping and properties (elasticity, density) of fabrics located near the place where the tapping is made. Tapping can be made by a special hammer with a rubber head, a plate of elastic material, called a plaster, or tapping the tip of the bent finger of one hand along the finger phalanner, superimposed on the human body. When the body is impaired, oscillations occur, the frequencies of which have a wide range. Some oscillations will quickly plump, others, due to resonance, will increase and will be heard. According to the tone of the percussion sounds, the condition and topography of the internal organs determine.

3. Ultrasound (UZ), sources of UZ. Features of the propagation of ultrasound waves.

Ultrasound call sound oscillations whose frequency occupies a range of 20 kHz to 10 10 Hz. The upper limit is made quite conditionally from such considerations that the wavelength in substance and tissues for such a frequency is commensurate with intermolecular distances, taking into account the fact that the rate of propagation of ultrasound in water and tissues is the same. The displacement in the bond wave is described by the previously considered wave equation.

Piezoelectric emitters of ultrasound received the greatest distribution both in the technique and in medical practice. Piezoelectric emitters serve as crystals of quartz, barium titanate, segmental salt, and other piezoelectric effect (straight) call the phenomenon of the occurrences of the mentioned crystalline plates opposed on the sign of charges under the action of mechanical deformations (Fig. 3a). After removal of deformation, charges disappear.

There is also a reverse piezoeffect, which has found application and in medical practice for obtaining high-frequency bonds. If there is a variable voltage from the generator on the silver plated edge of the surface of the plates of the piezoelectric elector, then the quartz plate will go to oscillation in the variable voltage of the generator. The amplitude of oscillations will be maximum when the self-frequency of the quartz plate (ν 0) coincides with the generator frequency (ν g), i.e. The resonance will come (ν 0 \u003d ν g). Receiver UZ can be created on the basis of a direct piezoelectric effect. In this case, under the influence of Uz-waves, the crystal deformation occurs, which leads to the appearance of an alternating voltage, which can be measured or recorded on the screen of the electronic oscilloscope after its preinstatement.

Ultrasound can be obtained using devices based on the phenomenon of magnetostriction (for low frequencies), which consists in changing the length (elongation and shortening) of the ferromagnetic rod placed in a high-frequency magnetic field. The ends of this rod will emit low-frequency bonds. In addition to these sources, UZ has mechanical sources (sirens, whistles), in which the mechanical energy is converted into the energy of the oscillations.

By nature, nod, as well as the sound, is a mechanical wave propagating in an elastic environment. The speed of propagation of sound and ultrasonic waves is about the same. However, the wavelength of the UZ is significantly less than sound. This makes it easy to focus the oscillations.

The ultrasonic wave has a much greater intensity than sound, due to the high frequency, it can reach several watts per square centimeter (W / cm 2), and when focusing, it is possible to obtain ultrasound with the intensity of 50 W / cm 2 or more.

The spread of UZ in the medium is different (due to the low wavelength) and another feature of the liquid and solid bodies are good versions of UZ, and the air and gas are bad. So, in water, with other things being equal, the UZ fades 1,000 times weaker than in the air. In the propagation of UZ in an inhomogeneous medium, it is reflected and refracted. The reflection of the bonds on the border of two media depends on the ratio of their wave resistances. If the Uz in medium with W 1 \u003d R 1 j 1 falls perpendicular to the flat surface of the second medium with W 2 \u003d R 2 J 2, then part of the energy will pass through the boundary surface, and the part will reflect. The reflection coefficient will be zero if R 1 j 1 \u003d R 2 J 2 i.e. Uz-energy will not reflect on the boundary of the surface partition, and will move from one medium to another without loss. For the boundaries of the air-liquid, air, liquid-air, solid air and, on the contrary, the reflection coefficient will be equal to almost 100%. This is explained by the fact that the air has very small acoustic resistance.

That is why in all cases of communication of the emitter of bonds with an irradiated medium, for example, with a person's body, it is necessary to strictly monitor so that there is no minimum air layer between the emitters and the cloth (the wave resistance of biological media is 3000 times larger air resistance). To exclude the air layer, the surface of the emitter of the emitter is covered with a layer of oil or it is applied with a thin layer on the surface of the body.

When spreading UZ in the medium, sound pressure arises, which fluctuates, taking a positive value in the compression area and negative in the next region of the discharge. For example, under the intensity of ultrasound 2 W / cm 2 in human tissues, pressure is created in the compression area + 2.6 atm., Which in the next region passes into the discharge - 2.6 atm. (Fig.4). The compression and discharge created by ultrasound leads to the formation of breaks of a solid fluid to form microscopic cavities (cavitation). If this process occurs in fluid, the voids are filled with liquid in pairs or gas dissolved in it. Then, a substance compression site is formed at the cavity site, the cavity slaughters quickly, a significant amount of energy is distinguished in a small volume, which leads to the destruction of the microstructures of the substance.

4. Medico-biological ultrasound use.

The biological effect of the UZ is very diverse. So far, it is impossible to further give an exhaustive explanation of the actions of the bonds on biological objects. It is not always easy to highlight from numerous effects caused by ultrasound, basic. However, it is shown that during the irradiation of bonds of biological objects, it is necessary to be considered mainly with the following actions of UZ:

thermal; mechanical action; indirect, in most cases, physico-chemical action.

The thermal effect of UZ is important, because The process of metabolism in biological objects is characterized by a significant temperature dependence. The thermal effect is determined by the absorbed energy. At the same time, small intensities are used (about 1 W / cm 2). The thermal effect causes the expansion of tissues, blood vessels resulting in the exchange of substances, the blood flow is enhanced. Thanks to the thermal effect of the focused ultrasound, it can be used as a scalpel for cutting not only soft tissues, but also bone tissue. Currently, the "welding" method of damaged or transplanted bone tissues has been developed.

Mechanical action. Mechanical oscillations of particles of a substance in an ultrasound field can cause a positive biological effect (micromassage of tissue structures). To this type of impact refers to microvibration at the cellular and sub-bottle level, the destruction of biomacomolecules, the destruction of microorganisms of fungi, viruses, destruction malignant tumors, stones B. bladder bubble and kidneys. Ultrasound is used for crushing substances, for example, in the manufacture of colloidal solutions, highly dispersed medicinal emulsions, aerosols. By the destruction of plant and animal cells, biologically active substances (enzymes, toxins) are distinguished. UZ causes damage and adjustment of cell membranes, changing their permeability.

Physico-chemical action ultrasound. Ultrasound action can be accelerated by some chemical reactions. It is believed that this is due to the activation of the molecules of water, which then disintegrate, forming active radicals H + and it.

Medico-biological application UZ can be divided mainly into two directions: diagnosis and therapy. The first is the location methods using mainly impulse radiation. This is an echohetephalography - determination of tumors and brain swelling.

Located methods are based on reflection of ultrasound from the boundary of the medium-based medium with different density. This method also includes ultrasound cardiography - measurement of heart size in the dynamics. Ultrasound location is used in ophthalmology to determine the size of the eye media. Ultrasonic Doppler effect is used to study the nature of the movement of cardiac valves and blood flow velocities.

A very large future of ultrasound holographic methods for obtaining an image of such organs as a kidneys, heart, stomach, etc.

The second direction includes ultrasound therapy. Ultrasounds are usually used with a frequency of 800 kHz and the intensity of 1 W / cm 2 and less. Moreover, the primary mechanisms of action are mechanical and thermal effect on the fabric. For ultrasound therapy purposes, the device UTP-ZM, etc.

5. Infrasound (from), the features of its distribution.

The effect of infrasounds on biological objects.

Infrasound (from) call sound oscillations, the upper range of which does not exceed 16 - 20 Hz. Lower range of 10 -3 Hz. Of great interest are from the frequency of 0.1 and even 0.01 Hz. From the noise. Sources from are movement (storm) marine or river water, forest noise, wind, thunderstorms, earthquakes and ribs, oscillations of buildings, machine tools, roads from moving transport. From occurs during the vibrations of the mechanisms, when blowing the wind buildings, trees, pillars, when man and animal movement.

The characteristic property of its small absorption of media. Therefore, it spreads over long distances. It is well propagated in the tissue of the human body, especially in bone tissue. The speed of the waves in the air is 1200 km / h, in water 6000 km / h.

The small absorption of it allows to spread it in the earth's crust to detect explosions and earthquakes at a large distance from the source. According to the measured from oscillations, the tsunami is predicted. Currently, sensitive receivers are developed from which, for example, it is possible to predict a storm for many hours before its offensive.

From oscillations have biological activity, which is explained by the coincidence of their frequency with alpha rhythm of the brain.

From the frequency of 1-7 Hz with an intensity of 70 dB for 8-10 minutes. Exposures cause: dizziness, nausea, difficulty breathing, feeling of oppression, headache, suffocity. All these factors are enhanced by re-exposure from. From a certain frequency may result in death.

Vibrations of mechanisms are the source of. Due to the unfavorable effect of vibration and from the human body, a vibrational disease occurs (WB). The WB occurs with the long-term effects of the indicated factors on a certain portion of the tissue or human body and leads to fatigue not only individual organs, but also the entire body of the person. It first leads to the atrophing of the muscles of the hands and other organs, to a decrease in sensitivity to mechanical vibrations, to the appearance of cramps of the fingers, legs and other organs.

It is assumed that the primary mechanism of action from the body has a resonant nature. Internal organs A person has its own oscillation frequency. When exposed to from the frequency equal to its own, there is a resonance, which causes the specified easy sensations, In some cases, it may lead to difficult consequences: a heart stop or breaking blood vessels.

The frequency of the human body fluctuations in the position is lying - (3 - 4 Hz), standing - (5 - 12 Hz), chest - (5 -8 Hz), abdominal cavity - (3 - 4 Hz) and other organs correspond to the frequency of.

Sound- fluctuations in the frequency range of human hearing, propagating in the form of waves in elastic media. Noise - erratic combination of various strength and frequency of sounds. The source of noise is any process that causes a local change in pressure or mechanical oscillations in solid, liquid and gaseous media.

Sound sensations are perceived by human hearing organs when exposed to sound waves with a frequency in the range from 16 Hz to 20 thousand Hz. The fluctuations with a frequency below 16 Hz are called an infrasound, and above 20,000 Hz - ultrasound.

By origin, noise may be mechanical, aerohydrodynamic and electromagnetic.

Mechanical noise It occurs as a result of shocks in the articular parts of the machines, their vibrations, in the mechanical processing of parts, in the gears in rolling bearings, and the like. The power of the sound radiation of the surface performing the oscillation depends on the intensity of oscillations of vibrating surfaces, their size, forms, fastening methods, etc.

Aerohydrodynamic noise It appears as a result of pressure pulsation in gases and liquids when they are moved in pipelines and channels (turbomachines, pumping units, ventilation systems, etc.).

Electromagnetic noise It is the result of stretching and bending ferromagnetic materials when exposed to variables of electromagnetic fields (electric machines, transformers, chokes, etc.).

The impact of noise per person manifests itself from subjective irritation to objective pathological changes in the function of hearing organs, central nervous system, cardiovascular system, internal organs.

The nature of the noise influence is due Its physical characteristics (level, spectral composition, etc.), the length of the impact and the psychophysiological state of a person.

Under the influence of noise decreases Attention, performance. The noise violates the sleep and rest of people.

All variety of neurotic and cardiological disorders, disorders of the gastrointestinal tract, hearing, etc., which arise under the influence of noise, combine in a symptom complex "noise disease" .

From a physical point of view, the sound is characterized the frequency of oscillations, sound pressure, intensity, or sound power. In accordance with Sanitary rules and standards 2.2.4 / 2.1.8.10-32-2002 "Noise in the workplace, in the premises of residential, public buildings and in the residential building" The main characteristics of noise are frequency of oscillations, sound pressure and sound level.

Sound pressure R (PA) is a variable component of air pressure or gas resulting from sound oscillations, pa.

When the sound wave is propagated, energy is transferred. Energy, transferred by sound wave per unit of time through the surface, perpendicular to the direction of propagation of the wave, is called sound intensity I. (W / m 2) :

,

where R - sound pressure, PA; ρ – the density of the sound environment, kg / m 3; C - sound speed in the air, m / s.

The human auditory apparatus has unequal sensitivity to the sounds of different frequencies. The auditory body of man is able to perceive sound oscillations in a certain range of intensities, limited to the upper and lower thresholds, depending on the sound frequency (Fig. 1).

Threshold of hearingness It has a minimum value at approximately the frequency of 1000 Hz. In the intensity or power of sound I O. It is equal to 10 -12 W / m 2, and on sound pressure P O. - 2x10 -5 Pa. Threshold of painful feeling at a frequency of 1000 Hz in intensity I Max equal to 10 W / m 2, and on sound pressure - R Max \u003d 2x10 -5 Pa. Therefore, for reference A sound with a frequency of 1000 Hz is adopted. The threshold is heard and the painful threshold lies checkered area .

The person's ear reacts not to the Oblit, but on the relative change in sound. Under the Law of Weber-Fekhner, the irritating effect of noise per person is proportional to the decimal logarithm of the sound pressure square. Therefore, the characteristics of noise use logarithmic levels:

sound intensity level L I. and sound pressure level L p. They are measured in decibels and are determined accordingly by formulas:

, dB,

, dB,

where I. and I o - The actual and threshold intensity of the sound, respectively, W / m 2; R and R O. - actual and threshold sound pressure, respectively, PA.

unit of measurement bel.named in honor Alexander Grayam Bella - scientist, inventor and businessman of Scottish origin, one of the founders of telephony (English. Alexander Graham Bell.; March 3, 1847 (18470303), Edinburgh, Scotland - August 2, 1922, Buddek, Province of New Scotland, Canada).

Fig 1. Human perception area of \u200b\u200bman

One is an extremely low value, barely noticeable on the rumor, the volume change corresponds to 1 dB (corresponds to the change in the intensity of the sound by 26% or sound pressure by 12%).

The logarithmic scale in dB (0 ... 140) allows you to determine the purely physical characteristic of noise regardless of the frequency. At the same time, the greatest sensitivity of the human hearing aid takes place at frequencies of 800 ... 1000 Hz, and the smallest at 20 ... 100 Hz. Therefore, to approach the results of subjective measurements to subjective perception, the concept corrected sound pressure level. The essence of the correction is to introduce amendments to the measured sound pressure level depending on the frequency. The most applied correction AND.Corrected sound pressure level L a \u003d l p - Δl acalled sound level.