Draft ventilation with acoustic calculation. Calculation of noise level
Ventilation indoors, especially in a residential or industrial, should function by 100%. Of course, many can say that you can simply open the window or the door to ventilate. But this option can work only in summer or spring. And what to do in winter when it's cold outside?
The need for ventilation
First, it is necessary to note that without fresh air Light people begin to function worse. It is also possible that the appearance of various diseases, which with a great percentage of the likelihood will turn into chronic. Secondly, if the building is a residential building in which children are, the need for ventilation increases even stronger, as some ailments that can infect the child, most likely will remain in his life. In order to avoid such problems, it is best to engage in the organization of ventilation. It is worth considering several options. For example, you can make a calculation supply system Ventilation and its installation. It is also worth adding that diseases are not all problems.
In a room or building where there is no permanent air exchange, all furniture and walls will be covered by a raid from any substance that is sprayed in the air. Suppose if this is a kitchen, then everything that fries is cooked, etc., will give your precipitate. In addition, the terrible enemy is dust. Even the cleaning agents that are designed to clean will still leave their precipitate, which will negatively affect the tenants.
Type of ventilation system
Of course, before proceeding with the design, the calculation of the ventilation system or its installation it is necessary to determine the type of network that is best suited. Currently distinguish three principal different types, the main difference between which in their functioning.
The second group is exhaust. In other words - it is normal exhaustwhich is most often installed in kitchen rooms building. The main task of ventilation is an air hood from the room outside.
Recycling. This system is perhaps the most efficient, as it simultaneously pumps the air out of the room, and at the same time it gives fresh from the street.
The only question that occurs from all next is, how does the ventilation system work, why air moves to one direction or another? This uses two types of aerial wakening source. They can be natural or mechanical, that is, artificial. To ensure their normal operation, it is necessary to carry out the correct calculation of the ventilation system.
Total network calculation
As mentioned above, just choose and install a certain type will be little. It is necessary to clearly determine how much air must be output from the room and how much you need to be downloaded back. Specialists call it an air exchange that needs to be calculated. Depending on the data obtained when calculating the ventilation system and must be repelled when the device type is selected.
Today it is known a large number of A variety of calculation methods. They are aimed at determining various parameters. Some systems make calculations to find out how much you need to delete warm air or evaporation. Some are carried out in order to find out how much air is necessary to dilute pollution if it is an industrial building. However, the minus of all these ways is the requirement of professional knowledge and skills.
What should I do if you need to calculate the ventilation system, but there is no such experience? The very first thing is that it is recommended to do is get acquainted with various regulatory documentsAvailable in each state or even a region (GOST, SNIP, etc.) in these papers there are all readings that any type of system must match.
Multiple calculation
One of the examples of ventilation can be the calculation of multiples. This method is quite complicated. However, it will fully accomplish and give good results.
The first thing you need to understand is what kind of multiplicity is. A similar term describes how many times the air indoors replaced fresh in 1 hour. This parameter depends on the two components is the specificity of the structure and its area. For a visual demonstration, the calculation of the formula for a building with a single air exchange will be shown. This suggests that a certain amount of air was derived from the premises and at the same time the fresh air was introduced such a quantity that corresponded to the volume of the same building.
The formula for calculation is used as: L \u003d n * V.
Measurement is carried out in cubic meters / hour. V is the volume of the room, and n is the value of the multiplicity that is taken from the table.
If there is a system calculation with several rooms, then in the formula you need to take into account the volume of the entire building without walls. In other words, you must first calculate the volume of each room, after which it is to fold all the results available, and the final value to substitute in the formula.
Ventilation with mechanical type of device
Calculation of a mechanical ventilation system, and its installation should pass on a specific plan.
The first stage is the definition of the numerical value of the air exchange. It is necessary to determine the amount of substance that should enter the inside of the structure to meet the requirements.
The second stage is the definition of the minimum dimensions of the air pipeline. It is very important to choose the correct cross-section of the device, since it depend on such things as purity and freshness of the air received.
The third stage is a choice of the type of system for mounting. This is an important point.
Fourth stage - and design of the ventilation system. It is important to clearly draw up a plan-scheme on which installation will be carried out.
The need for mechanical ventilation occurs only if the natural inflow does not cope. Any networks are calculated on parameters such as its air volume and the speed of this flow. For mechanical systems, this indicator can reach 5 m 3 / h.
For example, if necessary natural ventilation The area is 300 m 3 / h, it will be needed with a caliber of 350 mm. If a mechanical system is mounted, the volume can be reduced by 1.5-2 times.
Exhaust ventilation
Calculation like any other should begin with the fact that the performance is determined. Units of measurement of this parameter for the network - m 3 / h.
To carry out an effective calculation, you need to know three things: the height and area of \u200b\u200bthe rooms, the main purpose of each room, averaged number of people who will be at the same time in each room.
In order to begin to calculate the ventilation and air conditioning system of this type, it is necessary to determine the multiplicity. Numeric value This parameter is set to SNiP. It is important here to know that the parameter for residential, commercial or industrial premises will differ.
If the calculations are conducted for a household building, then the multiplicity is 1. If we are talking about installing ventilation in the administrative structure, the indicator is 2-3. It depends on some other conditions. To successfully calculate, you need to know the value of the exchange by multiplicity, as well as by the number of people. Need to take the greatest value Consumption to determine the required power of the system.
To find out the multiplicity of air exchanging, it is necessary to multiply the area of \u200b\u200bthe room at its height, and then to the value of multiplicity (1 for household, 2-3 for others).
In order to carry out the calculation of the ventilation and air conditioning system on a person, you need to know the amount of air consumed by one person and multiply this value to the number of people. On average, with minimal activity, one person consumes about 20 m 3 / h, with an average activity, an indicator increases to 40 m 3 / h, with intensive physical exertion, the volume increases to 60 m 3 / h.
Acoustic calculation of the ventilation system
Acoustic calculation is a mandatory operation that is attached to the calculation of any system ventilation system. Such an operation is carried out in order to perform several specific tasks:
- determine the octal spectrum of air and structural ventilation noise at the calculated points;
- compare the existing noise, with permissible noise by hygienic standards;
- determine the way to reduce noise.
All calculations must be carried out in strictly established calculation points.
After all the events on construction and acoustic standards were selected, which are designed to eliminate excessive noise in the room, the calculation of the entire system is carried out at the same points that were previously defined. However, it is necessary to add effective values \u200b\u200bobtained during this action to reduce noise.
For computation, certain source data is needed. They became the noise characteristics of the equipment, which were called sound power levels (UZM). For calculation, medium-meter frequencies in Hz are used. If an approximate calculation is carried out, then you can use correction levels of noise in the dBA.
If we talk about the calculated points, they are located in the habitats of the person, as well as in the installation places of the fan.
Aerodynamic calculation of the ventilation system
This calculation process is performed only after the calculation of the air exchange for the structure has already been calculated, and it was also decided to trace the air ducts and channels. In order to successfully carry out these calculations, you need to make ventilation systems in which it is necessary to allocate such parts as the shaped parts of all air ducts.
Using information and plans, you need to determine the length of the individual branches of the ventilation network. It is important to understand that the calculation of such a system can be carried out to solve two different tasks - direct or reverse. The purpose of the calculation depends on the type of task:
- direct - it is necessary to determine the dimensions of the sections for all sections of the system, while setting a certain level of air consumption, which will pass through them;
- reverse - determine the air flow, setting a certain section for all parts of the ventilation.
In order to calculate this type, you need to split the entire system into several separate sections. The main characteristic of each selected fragment is permanent flow air.
Programs for calculation
Since it is a very time-consuming and a long process to carry out the calculations and build the ventilation scheme - this is a very time-consuming and long process, simple programs that are able to do all actions are developed independently. Consider several. One of these calculation programs for the ventilation system is Vent-Clac. What is it so good?
A similar program for calculating and designing networks is considered one of the most convenient and efficient. The algorithm of the work of this application is based on the use of Altshul formula. The feature of the program is that it copes well as with the calculation of ventilation natural typeand mechanical type.
Since the software is constantly updated, it is worth noting that the latest edition of the application is able to conduct such works as aerodynamic calculations of the resistance of the entire ventilation system. It can also be effectively calculated by other additional parameters that will help in the selection of preliminary equipment. In order to carry out these calculations, the program will need such data as air flow at the beginning and at the end of the system, as well as the length of the main air duct room.
Since it is manually to count on all this long and have to break the calculations to the steps, this application will provide substantial support and save a large amount of time.
Sanitary norms
Another option for calculating ventilation - by sanitary standards. Such calculations are held for public and administrative and domestic objects. To implement right calculationsYou need to know the average number of people who will constantly be inside the building. If we talk about constant consumers of air inside, then they need about 60 cubic meters per hour per one. But since public faces are visited and temporary faces are visited, then they also need to be taken into account. The amount of air consumed on such a person is about 20 cubic meters per hour.
If you carry out all calculations, relying on the source data from the tables, then upon receipt of the final results it will become clearly seen that the amount of air coming from the street is much larger than the building consumed inside the building. In such situations, most often resorted to the most simply decision - Hoods of about 195 cubic meters per hour. In most cases, adding such a network will create an acceptable balance for the existence of the entire ventilation system.
Calculation of ventilation
Depending on the mode of moving air, ventilation is natural and forced.
Air parameters entering the receiving holes and openings of local hydrochildren and other devices that are located in work zoneshould be taken in accordance with GOST 12.1.005-76. In the size of the room 3, 5 meters and a height of 3 meters, its volume is 45 cubic meters. Consequently, ventilation should provide air consumption in 90 cubic meters / hour. IN summer time The installation of the air conditioner should be provided to avoid the excess temperature in the room for the sustainable operation of the equipment. It is necessary to pay due attention to the amount of dust in the air, as it directly affects the reliability and resource of the operation of the computer.
Power (or rather cooling power) of the air conditioner is its main characteristic, it depends on what size it is designed. For approximate calculations, 1 kW is taken at 10 m 2 with a ceiling height of 2.8 - 3 m (in accordance with SNiP 2.04.05-86 "Heating, ventilation and air conditioning").
To calculate the heat-flow of this room, a simplified technique was used:
where: Q - heat transfer
S - Room Square
h - room height
q - coefficient equal to 30-40 W / m 3 (in this case 35 W / m 3)
For the room 15 m 2 and a height of 3 m, heat-tanks will be:
Q \u003d 15 · 3 · 35 \u003d 1575 W
In addition, it should be considered heat dissipation from office equipment and people, it is considered (in accordance with SNIP 2.04.05-86 "Heating, ventilation and air conditioning") that in a calm state, a person highlights 0.1 kW of heat, a computer or a copy machine 0.3 kW, adding these values \u200b\u200bto common heat trapping can be obtained necessary power cooling.
Q additional \u003d (h · s operas) + (С · s comp) + (p · s print) (4.9)
where: Q Dop - Amount of Additional Heatprit
C - Motion Computer
H - operator heat dissipation
D - the heat dissipation of the printer
S comp - number of workstations
S Print - Number of Printers
S operator - number of operators
Additional heat transfer places will be:
Q extra 1 \u003d (0.1 · 2) + (0.3 · 2) + (0.3 · 1) \u003d 1.1 (kW)
Total the amount of heat flow is equal to:
Q Ohch1 \u003d 1575 + 1100 \u003d 2675 (W)
In accordance with these calculations, it is necessary to select the appropriate power and number of air conditioners.
For the room for which the calculation is carried out, air conditioners with a nominal capacity of 3.0 kW should be used.
Calculation of noise level
One of adverse factors production environment in the IVT is high level Noise, created by printing devices, air conditioning equipment, cooling system fans in the EMM themselves.
To resolve issues of need and appropriateness, noise reduction needs to know noise levels at the operator's workplace.
The noise level arising from several non-coherent sources operating simultaneously is calculated on the basis of the principle of energy summation of the radiation of individual sources:
L \u003d 10 · LG (Li N), (4.10)
where Li is the level of sound pressure of the i-th source of noise;
n - Number of noise sources.
The calculation results obtained are compared with the valid noise level for this workplace. If the results of the calculation is higher than the valid noise level, special measures are needed to reduce noise. These include: wall cladding and ceiling by sound-absorbing materials, reduced noise in the source, correct equipment planning and rational organization of the operator's workplace.
The sound pressure levels of noise sources acting on the operator at its workplace are presented in Table. 4.6.
Table 4.6 - sound pressure levels of various sources
Usually workplace The operator is equipped with the following equipment: Winchester in the system unit, fan (s) PC cooling systems, monitor, keyboard, printer and scanner.
Substitting the level of sound pressure for each type of equipment in formula (4.4), we obtain:
L \u003d 10 · LG (104 + 104.5 + 101.7 + 101 + 104.5 + 104.2) \u003d 49.5 dB
The value obtained does not exceed permissible level Noise for the operator's workplace, equal to 65 dB (GOST 12.1.003-83). And if we consider that such peripheral devices are hardly like a scanner and the printer will be used simultaneously, then this figure will be even lower. In addition, when the printer is working, the direct presence of the operator is optional, because The printer is equipped with the mechanism of car feeding.
Acoustic calculation They produce for each of the eight octave bands of the auditory range (for which noise levels are normalized) with medium-meter frequencies 63, 125, 250, 500, 1000, 2000, 4000, 8000 Hz.
For central systems Ventilation and air conditioning with branched air ducts is allowed to carry out an acoustic calculation only for frequencies 125 and 250 Hz. All calculations are performed with an accuracy of 0.5 Hz and rounding the final result to an integer number of decibels.
When the fan is running in the efficiency of the efficiency of more or equal to 0.9 kPd maximum 6 \u003d 0. With the deviation of the fan mode, no more than 20% of the maximum of the efficiency take 6 \u003d 2 dB, and with a deviation of more than 20% - 4 dB.
It is recommended to reduce the level of sound power generated in the air ducts, take the following maximum air movements: in main air ducts public buildings and auxiliary premises industrial buildings 5-6 m / s, and in branches - 2-4 m / s. For industrial buildings, these speeds can be increased by 2 times.
For ventilation systems with an extensive network of air ducts, the acoustic calculation is made only for the branch to the nearest room (with the same permissible noise levels), at different levels of noise - for the branch with the smallest allowable level. Acoustic calculation for air-acting and emull mines are made separately.
For centralized Systems Ventilation and air conditioning with an extensive network of air ducts can only be made for frequencies 125 and 250 Hz.
When the noise is admitted to the room from several sources (from the supply and exhaust grilles, from the units, local air conditioners, they choose several calculated points in the workplaces closest to the sources of noise. For these points, the octave levels of sound pressure are determined from each source of noise separately.
With different regulatory requirements during the day, the acoustic calculation levels are performed on the lowest permissible levels.
IN common account Noise sources do not take into account the sources that create octave levels at 10 and 15 dB at the calculation point below the regulatory, with the number of them, respectively, not more than 3 and 10. Do not take into account the throttling devices in the fans.
Severally uniformly distributed over the premises of the supply or exhaust grilles from one fan can be viewed as one source of noise when the noise is penetrated from one fan.
When there is a location of several sources of the same sound power, the sound pressure levels in the selected calculation point are determined by the formula
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(Gosstroy USSR)
note CH 399-69
CH 399-69
Moscow - 1970.
Official edition
State Committee of the Council of Ministers of the USSR for Construction Affairs
(Gosstroy USSR)
Note
On acoustic calculation of ventilation plants
Approved State Committee. Council of Ministers of the USSR for Construction Affairs
Publisher of Literature on Construction Moscow - 1970
shibers, lattices, plaffones, etc.) should be determined by the formula
L p \u003d 601go + 301GC + 101G /? + Fi, (5)
where V is the average air velocity at the input into the device under consideration (element of the installation), calculated on the area of \u200b\u200bthe supply duct (nozzle) for throttling devices and plafones and overall dimensions for lattices in m / s;
£ - coefficient aerodynamic resistance the element of the ventilation network, related to the air velocity at the entrance to it; for vanity disk plaffones (tear-off jet) £ \u003d 4; For anemostat and ceiling of VNIIGS (floor jet) £ \u003d 2; For supply and exhaust grilles, the resistance coefficients are accepted according to graphics in Fig. 2;
Supply grid.
Exhaust grille
Fig. 2. The dependence of the lattice resistance coefficient from its living section
F - cross-sectional area of \u200b\u200bthe supply duct in m 2;
B - amendment depending on the type of element in dB; For throttling devices, anemostat and disk plaffones B \u003d 6 dB; For the plaffones of the design of VNIIGS B \u003d 13 dB; For gratings B \u003d 0.
2.10. The octave levels of sound power of the noise emitted to the duct by throttling devices should be determined by formula (3).
At the same time, the formula (5) is calculated, the Al 2 correction is determined by table. 3 (In the calculation, the cross-sectional area of \u200b\u200bthe duct should be taken, in which the element or device is mounted), and the Al \\ corrections according to Table_5, depending on the value of the frequency parameter F, which is determined by the equation
! = < 6 >
where F is the frequency in Hz;
D is the average transverse size of the duct (equivalent diameter) in m; V is the average speed at the entrance to the element in question in m / s.
Table 5.
Al) Amendments to determine the octave levels of sound power of the noise of throttling devices in dB
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Note Intermediate values \u200b\u200bin Table 5 should be interpolation |
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2.11. The octave levels of the sound power of the noise generated in the beams and lattices should be calculated by formula (2), taking Ali amendments according to Table. 6.
2.12. If the speed of air movement in front of the air-distribution or air intake device (ceiling, grille, etc.) does not exceed the permissible amount of additional, then the noise of the procedure created in them
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Table 6. Ali amendments that take into account the distribution of sound power of the noise of plafones from grids by octave strips in dB |
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need to reduce sound pressure levels (see section 5) can not be taken into account
2.13. The allowable air movement speed in front of the air distribution or air intake unit of installations should be determined by the formula
y d op \u003d 0.7 10 * m / s;
^ Dop + 101E ~ -301ge-Mii-
where b extra is the permissible octave level of sound pressure in dB; n - the number of plafoons or lattices in the premises under consideration;
B is a permanent room in the octavest band in the m 2, received in accordance with paragraphs. 3.4 or 3.5;
AZ-I is amendment that takes into account the distribution of the sound power levels of plafoons and grilles by octave bands received by Table. 6, in dB;
D - amendment on the location of the noise source; at the location of the source in the working area (not higher than 2 m from the floor), and \u003d 3 dB; If the source is above this zone, A * ■ 0;
0.7 - stock coefficient;
F, b - designations are the same as in paragraph 2.9, formula (5).
Note. The determination of the permissible air movement rate is made only for one frequency, which is equal to the plafoons of VNIIGS 250, for 500 Hz disc plaffones, for anemostates and lattices of 2000 Hz.
2.14. In order to reduce the sound power level of noise generated by turns and tees of air ducts, sections of a sharp change in the cross-sectional area, etc., it is necessary to limit air movement speeds in the main air ducts of public buildings and auxiliary buildings of industrial enterprises to 5-6 m / s, and On branches up to 2-4 m / s. For production building, these velocities can be increased accordingly twice, if on technological and other requirements it is permissible.
3. Calculation of octave sound pressure levels at the calculated points
3.1. The octave levels of sound pressure on permanent jobs or indoors (at the calculated points) should not exceed the rules established by the norms.
(N n n n n i: 1. If regulatory requirements for sound pressure levels are different during the day, the acoustic calculation of the settings should be made to the lowest permissible levels of sound pressure.
2. Levels of sound pressure on permanent jobs or indoors (at the calculated points) depend on the sound power and the location of noise sources and sound-absorbing qualities of the room under consideration.
3.2. When determining octave sound pressure levels, the calculation should be made for permanent jobs or calculated points in the premises, the most close to noise sources (heating and air intake units, air distribution or air intake devices, air or air-thermal curtains, etc.). On the adjacent territory for the calculated points, points close to noise sources should be taken (fans open on site, exhaust or air intake mines, emissions of ventilation units, etc.), for which sound pressure levels are normalized.
a - noise sources (autonomous air conditioning and ceiling) and the calculated point is in the same room; b - noise sources (fan and installation elements) and the calculated point is in different rooms; B - the source of noise - the fan is indoors, the calculated point is on the arrival of the territory by nixie; 1 - autonomous air conditioning; 2 - the calculated point; 3 - generating noise cemeter; 4 - vibrozolyiro-breed fan; 5 - flexible insert; in - central muffler; 7 - a sudden narrowing of the cross section of the duct; 8 - branching of the air duct; 9 - rectangular turn with guide blades; 10 - smooth turn of the air duct; 11 - rectangular turn of the air duct; 12 - lattice; /
3.3. The octave / sound pressure levels in the calculation points should be defined as follows.
Case 1. Noise source (generizing noise Grille, ceiling, autonomous air conditioning, etc.) is in the premises under consideration (Fig. 3). Octave soundproof levels created at the calculation point with one source of noise should be determined by the formula
L-L, + I0! G (- £ - + - i-L (8)
oct \\ 4 i g g in t)
PR and M E C A N E. For ordinary rooms to which special acoustics requirements are presented - by the formula
L \u003d lp - 10 lg in sh -4- d - (- 6, (9)
where LP OKT is an octave noise source sound level (determined according to section 2) in dB \\
In the w - constant room with a source of noise in the octave strip under consideration (it is determined by paragraphs. 3.4 or 3.5) V 2;
D - correction to the location of the noise source if the noise source is located in the working area, then for all frequencies d \u003d 3 dB; if above the working area, d \u003d 0;
F - the radiation pattern of the noise source (determined by the curves in Fig. 4), dimensionless; G is the distance from the geometric center of the noise source to the calculated point in w.
The graphical solution of equation (8) is given in Fig. five.
Case 2. The calculated points are indoors, isolated from noise. The noise from the fan or the installation element propagates through the air ducts and is emitted to the room through an air distribution or air intake (grid). Octave soundproof levels created at the calculated points should be determined by the formula
L \u003d L P -DL P + 101G (-% + - V (10)
PR. For conventional premises, which are not predes are special requirements for acoustics, - by the formula
L - L P -A LP -10 LGIJ H ~ b a -f- 6, (11)
where L p B is an octal level of the sound power of the fan noise emitted into the air duct or the installation element in the octave band in dB (determined in accordance with paragraphs. 2.5 or 2.10);
AL R B - the total reduction in the level (loss) of the sound power of the fan noise or ele-
installation of the installation in the octave band in question along the path of sound propagation in dB (determined in accordance with clause 4.1); D - amendment on the location of the noise source; If the air distribution or air actuator is located in the working area, a \u003d 3 dB, if it is higher, - d \u003d 0; F and is the installation factor of the installation element (hole, grille, etc.), emitting noise into an islable room, dimensionless (determined by graphics in Fig. 4); Г "-Accoperation from an element of the installation that emit noise into an islable room to the calculated point in M \u200b\u200b\\
In and - permanent room insulated with noise in the octave band in m 2 (determined by paragraphs. 3.4 or 3.5).
Case 3. Estimated points are located on the territory adjacent to the building. The fan noise spreads through the air duct and emits into the atmosphere through the grid or mine (Fig. 6). Octave sound pressure levels created at the calculated points should be determined by the formula
I \u003d L P -AL P -201GR A -i ^ - + A-8, (12)
where g and is distround from the installation element (grille, hole), emitting noise into the atmosphere, to the calculated point in M \u200b\u200b\\ r and the sound of sound in the atmosphere, received by table. 7 in dB / km \\
A - correction in dB, taking into account the location of the calculated point relative to the axis of the radiating noise of the installation element (for all frequencies is taken in Fig. 6).
1 - ventilation shaft; 2 - Lubricated grille
The remaining values \u200b\u200bare the same as in Formulas (10)
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Table 7. Sound attenuation in the atmosphere in dB / km |
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3.4. Permanent premises in should be determined by schedules in Fig. 7 or Table. 9, taking the table. 8 To determine the characteristics of the room.
3.5. For premises to which special acoustics requirements are presented (unique audience
halls, etc.), constant premises should be determined in accordance with the instructions on the acoustic calculation for these premises.
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Permanent room at the calculated frequency is equal to constant room at a frequency of 1000 Hz multiplied to the frequency factor ^ £ \u003d £ 1000 |
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3.6. If there is noise from several sources of noise in the calculation point (for example, supply and recycling lattices, autonomous air conditioner, etc.), then for the estimated calculation point according to the corresponding formulas clause 3.2, octave levels of sound pressure, created by each of the noise sources, should be determined separately , and the total level in
Real "Instructions on Acoustic Calculation of Ventilation Installations" developed NII-building physics Gosstroy the USSR together with the institutes of Santechproject of the USSR Gosstroy and Gimatiaprom's hyperniaviaprom.
The instructions are designed to develop the requirements of the head of SNIP I-G.7-62 "Heating, ventilation and air conditioning. Design standards "and" sanitary standards of the design of industrial enterprises "(CH 245-63), which establishes the need to reduce the noise of ventilation installations, air conditioning and air heating of buildings and structures of various purposes when it exceeds the audio pressure levels permissible.
Editors: A. №1. Koshkin (Gosstroy USSR), Dr. Tehn. Sciences, prof. E. Ya. Yudin and Tehn candidates. Sciences E. A. Leskov and G. L. Osipov (Research Institute of Construction Physics), Cand. tehn Sciences I. D. Researi
In the instructions, the general principles of acoustic settlements of ventilation, air conditioning and air heating with mechanical motivation are presented. Ways to reduce sound pressure levels at permanent workplaces and in rooms (at the calculated points) to the values \u200b\u200bestablished by the norms are considered.
on (hyperminiaviaprom) and Ing. | g. A. Katsnelson / (GPI Santhekproekt)
1. General Provisions............ - . . , 3.
2. Sources of installation noise and their noise characteristics 5
3. Calculation of octave levels of sound pressure in the calculated
points .................... 13.
4. Reduced levels (loss) sound power noise in
various elements of air ducts ........ 23
5. Determination of the desired reduction of sound pressure levels. . . * ............... 28.
6. Events to reduce sound pressure levels. 31.
Application. Examples of acoustic calculation of ventilation installations, air conditioning and air heating with mechanical motivation ...... 39
Plan I quarter. 1970, № 3
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Characteristics of rooms Table 8. |
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each octave strip. The total sound pressure level should be determined in accordance with paragraph 2.7. Note. If the noise of the fan (or throttle) from one system (inlet or exhaust) penetrates the room through several lattices, then the distribution of sound power between them should be considered uniform. |
3.7. If the calculated points are located in the room, according to which the "noisy" air duct passes, and the noise into the room penetrates through the air duct walls, then octave sound pressure levels should be determined by the formula
L - L P -AL P + 101G --R B - 101GB "-J-3, (13)
where LP 9 is an octal level of sound power of the noise source emitted to the duct in dB (determined in accordance with PP 2 5 and 2.10);
ALP B - the total reduction in the levels (loss) of sound power along the path of sound propagation from the noise source (fan, choke, etc.) prior to the beginning of the area of \u200b\u200bthe duct, emitting noise into the room in dB (defined in accordance with section 4);
State Committee of the Council of Ministers of the USSR for Construction Affairs (Gosstroy USSR)
1. GENERAL PROVISIONS
1.1. These instructions are designed to develop the requirements of the head of SNIP I-G.7-62 "Heating, ventilation and air conditioning. Design standards "and" sanitary standards of design of industrial enterprises "(CH 245-63), which establishes the need to reduce the noise of ventilation installations, air conditioning and air heating with mechanical motivation to sound pressure levels permissible according to standards.
1.2. The requirements of these indications are applied to acoustic calculations of air (aerodynamic) noise formed during the installation of the installations listed in clause 1.1.
Note. In these instructions, the calculations of the vibration insulation of fans and electric motors (exciting of concussions and sound oscillations transmitted by building structures), as well as the calculations of the sound insulation of the enclosing vents of the ventilation chambers are not considered.
1.3. The procedure for calculating air (aerodynamic) noise is based on determining the sound pressure levels of noise generated when the installations specified in clause 1.1, on permanent workplaces or indoors (at the calculated points), determining the need to reduce these noise levels and measures to reduce sound levels of sound Pressures up to values \u200b\u200ballowed by norms.
Notes: 1. Acoustic calculation should be included in the projects of ventilation installations, air conditioning and air heating with mechanical motivation for buildings and structures of various purposes.
Acoustic calculation should be done only for premises about the normalized noise levels.
2. Air (aerodynamic) fan noise and noise generated by air flow in air ducts have broadband spectra.
3. In these instructions, under noise, it is necessary to yonize any kind of sounds that prevent the perception of useful sounds or disturbing silence, as well as sounds that have a harmful or irritant effect on the human body.
1.4. With acoustic calculation of the central installation of ventilation, air conditioning and air heating, the shortest branch of air ducts should be considered. If the central installation serves several rooms for which the regulatory requirements for noise are different, then additional calculation should be calculated for the branch of the air ducts serving the room with the smallest noise level.
Separately, calculation should be calculated for autonomous heating and ventilation units, autonomous air conditioners, airborne units or air vessels, local suns, air stroke installation units that are closest to settlement points or have the greatest performance and sound power.
Separately, the acoustic calculation of the branches of air ducts overlooking the atmosphere (suction and air emissions by installations).
In the presence of throttling devices between the fan and the premises, the apertures, throttles, seams, air distribution and air intake (lattices, plafones, anemostats, etc.), sharp changes in the cross section of air ducts, turns and tees should be produced by the acoustic calculation of these devices and installation elements.
1.5. Acoustic calculation should be produced for each of the eight octave bands of the auditory range (for which noise levels are normalized) with medium-meter frequencies of octave bands 63, 125, 250, 500, 1000, 2000, 4000 and 8000 Hz.
PRES HAPPY: 1. For central air heating systems, ventilation and air conditioning, with an extensive air duct network, it is allowed to calculate only for frequencies 125 and 250 Hz.
2. All intermediate acoustic calculations are performed with an accuracy of 0.5 dB. The end result is rounded to an integer number of decibels.
1.6. The required noise reduction activities created by installing ventilation, air conditioning and air heating, if necessary, should be defined for each source separately.
2. Sources of installation noise and their noise characteristics
2.1. Acoustic calculations to determine the level of sound pressure of air (aerodynamic) noise should be made with regard to noise generated:
a) fan;
b) when the air flow moves in the elements of installations (diaphragms, chokes, chirates, turns of air ducts, tees, lattices, plaffones, etc.).
In addition, there should be noise transmitted by ventilation air ducts from one room to another.
2.2. Noise characteristics (octave levels of sound power) Noise sources (fans, heating units, indoor air conditioners, throttling, air distribution and air actuators, etc.) should be taken on passports for this equipment or by catalog data
In the absence of noise characteristics, they should be determined experimentally on the customer's task or calculation, guided by the data given in these instructions.
2.3. The overall sound power level of the fan noise should be determined by the formula
L p \u003d z + 251g # + L01GQ-K (1)
where 1 ^ p - the overall sound power of the veins noise
tilator in dB relative to 10 "12 W;
L-criterion noness, depending on the type and design of the fan, in dB; You should be taken on Table. one;
A full pressure generated by a fan in kg / m 2;
Q - fan performance in m ^ / sec;
5 - amendment to fan mode in dB.
Table 1
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Criteria values \u200b\u200bof noise L for fans in dB |
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Notes: 1. Value 6 When the fan mode is rejected by no more than "A 20% of the maximum mode to. P. D. Should be taken to be 2 dB. In the mode of operation of the fan with a maximum to. P. 6 \u003d 0.
2. To facilitate the calculations in Fig. 1 shows a graph to determine the value of 251GTF + 101GQ.
3, obtained by formula (1), the magnitude characterizes the sound power emitted by an open input or output path of the fan in one direction to the free atmosphere or to the room in the presence of a smooth supply of air to the inlet nozzle.
4. With an empty air supply to the inlet nozzle or setting the throttle in the inlet of the pipe to the values \u200b\u200bspecified in
table. 1, should be added for axial vesiters 8 dB, for centrifugal fans 4 dB
2.4. Octave levels of sound power of the fan noise emitted by open input or outlet fan nozzle L R A, in the free atmosphere or room, should be determined by the formula
(2)
where - the overall sound power level of the fan in dB;
ALI - amendment that takes into account the distribution of the sound power of the fan by octave bands in dB, taken depending on the type of fan and the speed of the Table. 2.
table 2
ALU amendments that take into account the distribution of the sound power of the fan by octave stripes, in dB
|
Centrifugal fans | |||
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Medium meterometric hour |
Axial veins |
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tots of octave stripes in Hz |
with blades, for |
with blades, zag |
citizens |
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bent forward |
chicky back | ||
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(16 000) (3 2 000) | |||
Notes: 1. Led in Table. 2 Data without brackets is valid when the number of fan speed is in the range of 700-1400 rm) min.
2. With the speed of the fan 1410-2800, the entire spectrum should be shifted to octave down, and with an octave of 350-690 rpm to octave up, taking for extreme octave values \u200b\u200bindicated in the brackets for frequencies 32 and 16000 Hz.
3. When the fan turns, more than 2800 rpm, the entire spectrum should be moved into two octaves down.
2.5. Octave sound power levels of the fan noise emitted to the ventilation network should be determined by the formula
Lp - L p ■ - a l- ± - | ~ l i-2,
where Al 2 is amendment that takes into account the effect of the fan attachment to the air duct network in the dB, defined in Table. 3.
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Table 3. Amendment d £ 2\u003e Taking into account the effect of the fan and throttling device to the air duct network in dB |
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2.6. The overall sound power level of noise emitted by the fan through the walls of the casing (housing) into the aircraft room should be determined by the formula (1), provided that the noise criterion value is taken in Table. 1, as its average value for suction and discharge side.
The octave noise sound levels emitted by the fan to the ventilation chamber can be determined by formula (2) and Table. 2.
2.7. If several fans work simultaneously in the ventilation chamber, then for each octave band, it is necessary to determine the total level.
sound power noise emitted by all fans.
The total sound power level of the noise L CYU when working on the identical fans should be determined by the formula
£ Sum \u003d z.j + 10 IGN, (4)
where Li is the sound power level of the noise of one fan in dB-, P - the number of identical fans.
To summarize the sound power levels of noise or sound pressure generated by two noise sources of different levels, Table should be used. four.
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Table 4. Addition of sound power or sound pressure levels |
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Note. With the number of different noise levels, more than two additions are performed sequentially, starting from two large levels. |
2.8. The octave levels of the sound power of the noise emitted to the room with autonomous air conditioners, the heating and ventilation units, airborne aggregates (without air ducts) with axial fans, should be determined by formula (2) and Table. 2 with a higher correction 3 dB.
For autonomous units with centrifugal fans, the octave noise power levels emitted by the suction and pumping nozzles of the fan should be determined by formula (2) and Table. 2, and the total noise level is the table. four.
Note. With air intake, installations are not required from the outside by an empty correction.
2.9. The overall sound power level of noise generated by throttling, air distribution and air intake devices (throttle valves.
Description:
In force in the country, the norms and rules are not allowed that the projects should provide measures to protect against the noise of equipment used for human life support. Such equipment includes ventilation and air conditioning systems.
Acoustic calculation as a basis for designing a low noise ventilation system (air conditioning)
V.P. Gusev, Doctor Tehn. Sciences, head. Laboratory protection against noise of ventilation and engineering and technological equipment (Niizf)
In force in the country, the norms and rules are not allowed that the projects should provide measures to protect against the noise of equipment used for human life support. Such equipment includes ventilation and air conditioning systems.
The basis for designing the noiselessness of ventilation systems and air conditioning is an acoustic calculation - a mandatory application to the ventilation project of any object. The main tasks of this calculation: determination of an octave spectrum of air, structural ventilation noise at the calculated points and its required reduction by comparing this spectrum with a permissible spectrum by hygienic standards. After the selection of construction and acoustic measures to ensure the required reduction in noise, the calculation of the expected sound pressure levels is carried out in the same settlement points, taking into account the effectiveness of these activities.
The following materials do not claim to complete the presentation of the technique of acoustic calculation of ventilation systems (installations). They contain information that clarify is complemented or in a new way reveal various aspects of this technique on the example of the acoustic calculation of the fan as the main source of noise of the ventilation system. Materials will be used in the preparation of the Code of Rules for the calculation and design of the noiselessness of the ventilation plants to the new SNiP.
The source data for acoustic calculation is the noise characteristics of the equipment - the levels of sound power (usm) in octave stripes with medium meterometric frequencies 63, 125, 250, 500, 1,000, 2,000, 4,000, 8,000 Hz. For indicative calculations, the corrected levels of sound power of noise sources in dBA are sometimes used.
The calculated points are located in the habitats of a person, in particular, at the place of installation of the fan (in the ventilation chamber); indoors or in zones bordering the place of installation of the fan; in the premises serviced by the ventilation system; indoors where air ducts pass in transit; In the zone of device reception or emission, or only air intake for recycling.
The calculated point is located in the room where the fan is installed
In general, the levels of sound pressure in the room depend on the sound power of the source and the radiation pattern of noise, the number of noise sources, on the location of the calculated point relative to the source and enclosing building structures, from the size and acoustic quality of the room.
Octave soundproof levels created by a fan (fans) at the installation site (in a ventkamer) are equal to:
where FI is the focus of the noise source (dimensionless);
S is the area of \u200b\u200bthe imaginary sphere or its part surrounding the source and passing through the calculation point, m 2;
B - Acoustic permanent room, m 2.
The calculated point is indoors, adjacent to the room where the fan is installed.
The octave levels of air noise penetrating through the fencing to the insulated room, adjacent to the room, where the fan is installed, are determined by the soundproofing ability of the noisy room fences and the acoustic qualities of the protected room, which is expressed by the formula:
| (3) |
where L Ш is an octave level of sound pressure indoor with noise source, dB;
R is an isolation from air noise by a enclosing structure through which noise penetrates, dB;
S is the area of \u200b\u200bthe enclosing structure, m 2;
B U - acoustic constant of the insulated room, m 2;
k is a coefficient that takes into account the violation of the diffusion of the sound field indoors.
The calculated point is located in the room serviced by the system
The noise from the fan spreads through the air duct (aircraft), partially fades in its elements and through air distribution and air-actuate lattices penetrates the serviced room. The octave levels of sound pressure indoors depend on the amount of noise reduction in the air canal and the acoustic qualities of this room:
| (4) |
where L PI is the level of sound power in the i-th octave emitted by the fan in the air channel;
D L network - attenuation in the air canal (on the network) between the noise source and the room;
D l Pomi is the same as in formula (1) - formula (2).
Attitude on the network (in the aircraft) D L R network is the sum of the attenuation in its elements that are sequentially located in the course of sound waves. The energy theory of the propagation of sounds in the pipes suggests that these elements do not affect each other. In fact, the sequence of the shaped elements and direct sections form a single wave system, in which the principle of independence of attenuation in the general case cannot be justified on pure sinusoidal colors. At the same time, in octave (wide) bands, the standing waves created by individual sinusoidal constituents compensate each other, and therefore an energy approach that does not take into account the wave pattern in the air ducts and the flow of sound energy can be considered justified.
The attenuation on the direct portions of the air ducts from the sheet material is due to losses for the deformation of the walls and the radiation of the sound outward. The reduction in the level of sound power D l p per 1 m of the length of the direct sections of metal air ducts, depending on the frequency, can be judged by fig. one.
As can be seen, in the air ducts of the rectangular section, the attenuation (decrease in UZM) with increasing sound frequency decreases, and the round cross section increases. In the presence of thermal insulation on metal ducts, shown in Fig. 1 values \u200b\u200bshould be increased by about twice.
The concept of attenuation (decrease) of the flow of sound energy cannot be identified with the concept of changing the sound pressure level in the air canal. When the sound wave is moving along the channel, the total amount of energy that it bears is reduced, but it is not necessarily associated with a decrease in sound pressure level. In the narrowing canal, despite the attenuation of the total energy flow, the sound pressure level may increase due to an increase in the density of sound energy. In the expanding channel, on the contrary, the energy density (and the sound pressure level) can decrease faster than the overall sound power. The attenuation of the sound on the plot with a variable cross section is:
 |
(5) |
where L 1 and L 2 are the average levels of sound pressure in the initial and finite during the sound waves of the sections of the channel section;
F 1 and F 2 - cross-sectional areas, respectively, at the beginning and end of the channel section.
Attitude on the turns (in the knees, removals) with smooth walls, the cross section of which is less than the wavelength, is determined by the reactive resistance of the type of additional mass and the appearance of a higher order mod. The kinetic energy of the flow on the rotation without changing the channel cross section is increasing due to the emergence of the velocity field. The rectangular turn acts like a low frequency filter. The amount of noise reduction on the rotation in the range of flat waves gives an accurate theoretical solution:
 |
(6) |
where k is the sound factor module.
With a ≥ L / 2, the value K is zero and the incident flat sound wave is theoretically completely reflected by the rotation of the channel. The maximum reduction of noise is observed when the depth of rotation is approximately half the wavelength. The magnitude of the theoretical module of the coefficient of passing sound through rectangular turns can be judged by fig. 2.
In real structures, according to work, the maximum attenuation is 8-10 dB, when half the wavelength is stacked in the width of the channel. With an increase in frequency, the attenuation decreases to 3-6 dB in the field of wavelengths close to the doubted channel width. It then increases again in high frequencies, reaching 8-13 dB. In fig. 3 shows the noise attenuation curves on the corners of the channels for flat waves (curve 1) and for a random, diffuse sound drop (curve 2). These curves are obtained based on theoretical and experimental data. The presence of a noise reduction maximum with a \u003d L / 2 can be used to reduce noise with low-frequency discrete components, adjusting the size of the channels on the rotations on the frequency of interest.
Reducing noise on turns whose angle is less than 90 °, approximately proportional to the angle of rotation. For example, a decrease in noise on a rotation with an angle of 45 ° equal to half of its reducing on the rotation with an angle of 90 °. On the corner of the angle less than 45 °, noise reduction is not taken into account. For smooth turns and straight knees of air ducts with guide blades, noise reduction (sound power level) can be determined using curves Fig. four.
In the ramifications of the channels, the transverse dimensions of which are less than half of the length of the sound wave, the physical reasons for attenuation are similar to the reasons for attenuation in the knees and taps. This attenuation is defined as follows (Fig. 5).
Based on the continuity equation:
From the condition of pressure continuity (R P + R 0 \u003d R PR) and equations (7), the passage of sound power can be represented by the expression
a decrease in sound power level with branch cross section
 |
(11) |
 |
(12) |
(13) |
In case of a sudden change in the cross section of the channel with transverse dimensions, less than half-filled lengths (Fig. 6 A), the reduction in the sound power level can be defined in the same way as with branching.
The estimated formula for such a change in the cross section of the channel has the form
 |
(14) |
where M is the ratio of a larger channel cross section to the smaller.
Reducing sound power levels when the channel dimensions are greater than the length of the half-fees of non-planar waves with a sudden congestion of the channel, equal
If the channel is expanding or smoothly narrows (Fig. 6 b and 6 g), then the reduction in the sound power level is zero, since the reflection of the waves with a length of a smaller channel sizes does not occur.
In simple elements of the ventilation systems, the following decrease values \u200b\u200bare taken at all frequencies: calorificates and 1,5 dB air coolers, central air conditioners 10 dB, mesh filters 0 dB, place of fan adjoining to the air duct network 2 dB.
The reflection of sound from the end of the duct occurs if the transverse size of the air duct is less than the length of the sound wave (Fig. 7).
If a flat wave is spread, there is no reflection in a large air duct, and we can assume that there is no reflection losses. However, if the opening connects the premises of large sizes and open space, then only diffuse sound waves appear to the opening, which is equal to the fourth part of the diffuse field energy. Therefore, in this case, there is a weakening of the level of the intensity of the sound by 6 dB.
The characteristics of the radiation of the sound with air distribution grids are listed in Fig. eight.
When the noise source is located in space (for example, on a large-room column) S \u003d 4P R 2 (radiation in the full sphere); in the middle part of the wall, the overlap S \u003d 2p R 2 (radiation in the hemisphere); in a dihedral corner (radiation in 1/4 of the sphere) S \u003d P R 2; In the triggered corner of S \u003d P R 2/2.
The weakening of the noise level indoors is determined by formula (2). The calculated point is selected at the place of permanent residence of people, close to the noise source, at a distance of 1.5 m from the floor. If noise at the calculation point is created by several lattices, the acoustic calculation is made according to their total impact.
When the source of noise is a portion of a transit duct passing through the room, the source data for the calculation by formula (1) serve as octave noise levels of the noise emitted by them, determined by the approximate formula:
(16) |
where L pi is the sound power level of the source in the i-th octave band of the frequency, dB;
D L 'RSeti - attenuation in the network between the source and the transit section under consideration, dB;
R Ti - sound insulation of the design of the transit duct section, dB;
S T - surface area of \u200b\u200bthe transit site, exiting the room, m 2;
F T is the cross-sectional area of \u200b\u200bthe duct area, m 2.
Formula (16) does not take into account the increase in the density of sound energy in the air duct due to reflections; The conditions of falling and passing the sound through the design of the air duct differ significantly from the passage of diffuse sound through the roofing of the room.
Estimated points are located on the territory adjacent to the building.
The fan noise spreads through the air duct and emits into the surrounding space through the grille or mine, directly through the walls of the fan body or the open nozzle when installing the fan outside the building.
When the distance from the fan before the calculated point, there is a lot of more than its size source, the noise source can be considered point.
In this case, the octave levels of sound pressure at the calculation points are determined by the formula
(17) |
where L Pokti is an octal sound power level of noise source, dB;
D l Pineseti - a total reduction in sound power level along the path of sound propagation in the air duct in the octave strip under consideration, dB;
D L HI - the indicator of the radiation direction of the sound, dB;
r is the distance from the noise source to the calculated point, m;
W is the spatial angle of radiation of the sound;
b A - Sound attenuation in the atmosphere, dB / km.
If there are a number of several fans, lattices or another long-dimensional nozzle source of limited sizes, then the third term in formula (17) is accepted equal to 15 LGR.
Calculation of structural noise
Structural noise in rooms adjacent to ventilation chambers, arises as a result of transmitting dynamic forces from the fan to overlap. A octal level of sound pressure in the adjacent insulating room is determined by the formula
For fans located in the technical room outside the overlap over the insulated room:
 |
(20) |
where L PI is an octal level of air noise sound power emitted by a fan to the ventilation chamber, dB;
Z c - the total wave resistance of the elements of the vibration insulators, on which the refrigeration machine is installed, n s / m;
Z lane - input impedance of overlapping - carrier plate, in the absence of sex on an elastic base, floor slabs - if available, n s / m;
S is the conditional area of \u200b\u200bthe operating room over the insulated room, m 2;
S \u003d s 1 at s 1\u003e s u / 4; S \u003d S u / 4; at s 1 ≤ s u / 4, or if the technical room is not above the insulated room, but has one common wall with it;
S 1 - the area of \u200b\u200bthe technical room above the insulated room, m 2;
S U - an insulated room area, m 2;
S B is the total area of \u200b\u200bthe technical room, m 2;
R - Own isolation of air noise overlap, dB.
Determination of the required reduction of noise
The required decrease in octave sound pressure levels is calculated separately for each noise source (fan, shaped elements, reinforcement), but at the same time take into account the number of noise sources of the noise and the magnitude of the sound pressure levels created by each of them at the calculation point. In the general case, the required reduction in noise for each source must such as total levels in all octave frequency bands from all noise sources did not exceed the permissible levels of sound pressure.
In the presence of one noise source, the required decrease in octave sound pressure levels is determined by the formula
where n is the total number of noise sources taken into account.
In the total number of noise sources n, when determining the D L TI, the required reduction in octave sound pressure levels on the territory of the urban building should include all sources of noise, which create at the calculation point of sound pressure levels that differ in less than 10 dB.
When determining D L TRI for calculated points in a room that protects against the noise of the ventilation system, in the total number of noise sources should include:
When calculating the required reduction of the fan noise - the number of systems serving the room; The noise generated by air distributing devices and the shaped elements is not taken into account;
When calculating the required reduction in noise generated by air distribution devices of the ventilation system under consideration, the number of ventilation systems serving the room; The noise of the fan, air distribution devices and the shaped elements are not taken into account;
When calculating the required reduction in noise generated by the shaped elements and air distribution devices of the branch, the number of shaped elements and chokes, whose noise levels differ from one of the other by less than 10 dB; The noise of the fan and the lattice is not taken into account.
At the same time, in the total number of noise sources taken into account, noise sources are not taken into account, creating the level of sound pressure on 10 dB smaller than the permissible, during their number of no more than 3 and 15 dB less than permissible under their number 10.
As can be seen, the acoustic calculation is not a simple task. The necessary accuracy of its solutions is ensured by acoustics specialists. The effectiveness of the noiselessness and the cost of its implementation depends on the accuracy of the acoustic calculation. If the value of the desired reduction of noise is underestimated, the events will not be effective enough. In this case, it will be necessary to eliminate the deficiencies on the current object, which is inevitably associated with significant material costs. With an overwhelmed noise reduction, unnecessary costs are laid directly into the project. So, only by installing silencers, the length of which is larger than the required 300-500 mm, the additional costs of medium and large objects can be 100-400 thousand rubles and more.
Literature
1. SNIP II-12-77. Protection against noise. M.: Stroyzdat, 1978.
2. SNiP 23-03-2003. Protection against noise. Gosstroy Russia, 2004.
3. Gusev V.P. Acoustic requirements and rules for the design of low noise ventilation systems // Avok. 2004. No. 4.
4. Guide for calculating and designing the noiselessness of ventilation plants. M.: Stroyzdat, 1982.
5. Yudin E. Ya., Terekhin A.S. Fight against the noise of mine ventilating plants. M.: Nedra, 1985.
6. Reducing noise in buildings and residential areas. Ed. G. L. Osipova, E. Ya. Yudina. M.: Stroyzdat, 1987.
7. Khoroshev S. A., Petrov Yu. I., Egorov P. F. Fight against the noise of fans. M.: Energoisdat, 1981.