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)

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.

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

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, throttle-valves, sewers, air distribution and air intake (lattices, plafones, anemostats, etc.), sharp changes in the cross section of air ducts, turns and tees should produce 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

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

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.

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.

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.

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 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 approximate calculations, corrected levels of sound power of noise sources can be 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.

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

where L Pokti is an octal sound power level of noise source, dB;

ΔL Pineeti - a total reduction in sound power level along the path of propagation of sound in the air duct in the octave strip under consideration, dB;

ΔL ni is an indicator of the radiation orientation 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.

Engineering and Construction Magazine, N 5, 2010
Rubric: Technology

D.T., Professor I.I. Bogolepov

GOU St. Petersburg State Polytechnic University
and GOU St. Petersburg State Maritime Technical University;
Magister A.A. Powety,
GOU St. Petersburg State Polytechnic University

The ventilation and air conditioning system (BVKV) is the most important system for modern buildings and structures. However, in addition to the necessary high-quality air, the system transports noise to the premises. It comes from the fan and other sources, spreads through the air duct and emitted to the ventilated room. Noise is incompatible with a normal sleep, educational process, creative work, high-performance work, full-fledged rest, treatment, obtaining quality information. In the construction norms and rules of Russia there was such a situation. The method of acoustic calculation of the CBS of the buildings used in the old SNIVE II-12-77 "noise protection", outdated and did not enter the new SNiP 23-03-2003 "Noise Protection". So, the old method is outdated, and there is no new generally accepted. Below is a simple approximate method of acoustic calculation of the CBS in modern buildings, designed using better production experience, in particular, on maritime courts.

The proposed acoustic calculation is based on the theory of long audio propagation lines in an acoustically narrow pipe and on the theory of space of rooms with a practically diffuse sound field. It is performed in order to evaluate sound pressure levels (hereinafter referred to as high) and the corresponding values \u200b\u200bof the values \u200b\u200bof the valid values \u200b\u200bof permissible noise. It provides for the definition of UDD from the BVKV due to the operation of the fan (hereinafter - "Machine") for the following typeranges of the premises:

1) indoors where the car is located;

2) in rooms through which the ducts pass in transit;

3) in the premises serviced by the system.

Source data and requirements

The calculation, design and control of the protection of people from noise is proposed to be performed for the most important frequencies for the human perception of octave bands, namely: 125 Hz, 500 Hz and 2000 Hz. An octave band of frequencies 500 Hz is a medium-beometric value in the range of irrigated frequency bands of 31.5 Hz - 8000 Hz. For permanent noise, the calculation provides for the definition of UPD in octave frequency bands by sound power levels (usm) in the system. The values \u200b\u200bof WSD and uh are associated with a common relation \u003d - 10, where - WSD relative to the threshold value 2 · 10 N / m; - UZM relative to the threshold value of 10 W; - area of \u200b\u200bpropagation of the front of the sound waves, m.

WSDS should be determined in the calculated points of the noise of the noise of the premises according to the formula \u003d +, where - the um of the source of noise. The value that takes into account the influence of the placement on the noise in it is calculated by the formula:

where is the coefficient that takes into account the impact of the near field; - the spatial angle of radiation of the source of noise, is happy.; - the radiation rate coefficient is adopted according to experimental data (in the first approximation equal to one); - the distance from the center of the noise emitter to the calculated point in m; \u003d - acoustic permanent room, m; - average sound absorption coefficient of internal surfaces of the room; - the total area of \u200b\u200bthese surfaces, m; - coefficient taking into account the violation of the diffuse sound field indoors.

The specified values, the calculated points and the norms of permissible noise are governed for the premises of various buildings by SNIP 23-03-2003 "Noise Protection". If the design values \u200b\u200bof the WSDD exceed the rate of permissible noise at least in one of the indicated three frequency bands, it is necessary to design measures and noise reduction tools.

The source data for the acoustic calculation and the design of the BVKV are:

- layout schemes used in the design of the structure; sizes of machines, air ducts, adjusting reinforcement, knees, tees and air distributors;

- air movements in highways and branches - according to the technical task and aerodynamic calculation;

- Drawings of the overall location of the premises serviced by the BVKV - according to the construction project of the structure;

- noise characteristics of machines, adjusting reinforcement and air distributors of the BVKV - according to the technical documentation for these products.

The noise characteristics of the machine are the following levels of air noise in octave frequency bands in dB: - NUMS NUMA, propagating from the car into suction air duct; - um of noise propagating from the car into the air duct injection; - SSM Summa emitted by the machine body into the surrounding space. All noise characteristics of the machine are currently determined on the basis of acoustic measurements according to relevant national or international standards and other regulatory documents.

The noise characteristics of silencers, air ducts, adjustable reinforcement and air distributors are air noise in octave frequency bands in dB:

- the um of noise generated by the elements of the system when passing the air flow through them (noise generation); - The um of noise, scattered or absorbed in the elements of the system when the flow of sound energy (noise reduction) is passed.

The effectiveness of generation and reduction of noise by elements of the CVS is determined on the basis of acoustic measurements. We emphasize that values \u200b\u200bof values \u200b\u200band must be listed in the relevant technical documentation.

Proper attention is paid to the accuracy and reliability of acoustic calculation, which are laid in the error of the result of values \u200b\u200band.

Calculation for premises where the machine is installed

Suppose in the room 1 where the machine is installed, there is a fan, the sound power level emitted to the suction pipe, injection and through the machine body, there are values \u200b\u200bin dB, and. Suppose that the fan on the part side of the discharge pipe is installed with noise silencer with fuel efficiency in dB (). The workplace is located at a distance from the car. The separating room 1 and room 2 wall is located at a distance from the machine. Permanent sound absorption of the room 1: \u003d.

For room 1, the calculation provides for the solution of three tasks.

1st task. Performance of valid noise.

If the suction and discharge nozzles are removed from the room of the machine, then the calculation of the Wedge in the room where it is located, is made according to the following formulas.

The octave WSDs at the calculation point of the room are determined in the DB by the formula:

where - the um of noise emitted by the machine with the accuracy and reliability using. The value mentioned above is determined by the formula:

If indoors are posted n. Sources of noise, UDD from each of which at the calculation point is equal, then the total WWDE from all is determined by the formula:

As a result of the acoustic calculation and design of the BBV for the room 1, where the machine is installed, it must be executed in the calculated points of the values \u200b\u200bof permissible noise.

2nd task. Calculation of the value of urban in the air duct injection from the room 1 to the room 2 (the room through which the air duct passes transit), namely, the values \u200b\u200bin the dB are produced by the formula

3rd task. Calculation of the value of urban radiated by the wall with sound insulation of the room 1 to the room 2, namely, the values \u200b\u200bin dB, executed according to the formula

Thus, the result of calculating indoors 1 is the performance of noise standards in this room and obtaining the source data for calculating indoors 2.

Calculation for premises through which the air duct passes transit

For room 2 (for premises through which the air duct passes transit) the calculation provides for the solution of the following five tasks.

1st task. Calculation of the sound power emitted by the air duct walls to the room 2, namely the definition of the value in the DB by the formula:

In this formula: - See above the 2nd task for the room 1;

\u003d 1.12 - the equivalent diameter of the duct section with cross-sectional area;

- Length of room 2.

Soundproofing of the walls of the cylindrical duct in the dB is calculated by the formula:

where is the dynamic modulus of the elasticity of the material of the air duct wall, n / m;

- the inner diameter of the air duct in m;

- wall thickness of the air duct in m;


Soundproofing the walls of the rectangular air ducts is calculated according to the following formula in dB:

where \u003d - the mass of the surface of the surface of the air duct wall (the product of the material density in kg / m on the wall thickness in m);

- Medium meterometric frequency of octave bands in Hz.

2nd task. The calculation of the USP at the calculated point of room 2, located at a distance from the first source of noise (air duct) is performed according to the formula, dB:

3rd task. The calculation of the WWD at the calculated point of the room 2 from the second source of noise (UZM, the radiated wall of the room 1 to the room 2, the value in dB) is performed according to the formula, dB:

4th task. Performance of valid noise.

The calculation is carried out according to the formula in dB:

As a result of the acoustic calculation and the design of the BBV for the room 2, through which the air duct passes transit, it must be fulfilled in the calculated points of the valid noise. This is the first result.

5th task. Calculation of the value of urban in the air duct of injection out of the room 2 to the room 3 (room serviced by the system), namely, the values \u200b\u200bin the DB according to the formula:

The magnitude of the loss of radiation of the sound power of the noise by the walls of the air ducts in the rectilinear areas of the air ducts of a single length in dB / m is presented in Table 2. The second result of the calculation in the room 2 is to obtain the source data for the acoustic calculation of the ventilation system in the room 3.

Calculation for the premises serviced by the system

In rooms 3 serviced by the BVKV (for which the system ultimately is intended), the calculated points and the values \u200b\u200bof permissible noise are accepted in accordance with the SNiP 23-03-2003 "noise protection" and the technical task.

For room 3, the calculation provides for the solution of two tasks.

1st task. Calculation of sound power emitted by the air duct through the outlet air distribution hole to the room 3, namely the definition of the value in dB, is proposed as follows.

Private task 1 for low-speed system with air velocity V<< 10 м/с и = 0 и трех типовых помещений (см. ниже пример акустического расчета) решается с помощью формулы в дБ:

Here



() - losses in the silencer of noise indoors 3;

() - losses in the tee in the room 3 (see below formula);

- loss as a result of reflection from the end of the duct (see Table 1).

Total task 1. It consists in solving for many of three sample premises using the following formula in dB:



Here - the um of noise spreading from the car into the air duct injection into the dB, taking into account the accuracy and reliability of the value (taken according to the technical documentation for the machine);

- the um of noise generated by air flow in all elements of the system in dB (accepted according to technical documentation for these elements);

- the um of noise absorbed and dissipating when the flow of sound energy through all the elements of the system in dB (accepted according to the technical documentation for these elements);

- the value that takes into account the reflection of sound energy from the end outlet of the air duct in dB is taken according to Table 1 (this value is zero, if already includes);

- a value equal to 5 dB for low-speed CVS (air velocity in highways less than 15 m / s), equal to 10 dB for the medium-speed CBV (air velocity in highways less than 20 m / s) and equal to 15 dB for high-speed CBS (speed in highways less 25 m / s).

Table 1. Value in dB. Octave strips

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 methods of technological and other devices that are located in the working area should 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, an air conditioner should be provided with the aim of avoiding the temperature of the room for stable 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, By adding these values \u200b\u200bto common heat-flowing, you can get the required cooling power.

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 the adverse factors of the production environment in the IVC is the high level of noise created by printing devices, air conditioning equipment, fans of cooling systems 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 - the 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, the operator's workplace 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 resulting value does not exceed the permissible noise level 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.