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Octave sound pressure levels l. Reducing sound power levels along the path of noise propagation. Calculation of the effective area sounded by a horn loudspeaker

8.16. The total decrease in sound power levels in dB along the path of noise propagation should be determined sequentially for each element of the duct network and then summed up using the formula

(65)

where is the decrease in octave sound power levels in individual elements air ducts in dB, determined according to paragraphs. 8.17 - 8.22 of these standards;

n c- the number of elements of the duct network, which take into account the reduction in sound power levels.

8.17. The decrease in octave sound power levels in dB per 1 m of length in straight sections of metal air ducts of rectangular and circular cross-sections should be taken according to Table. twenty.

8.18. The decrease in octave sound power levels in dB on straight sections of brick and concrete channels is taken into account in the calculations.

Table 20

The form cross section duct	Hydraulic diameter in mm	Decrease in sound power levels and at the geometric mean frequency of the octave bands in Hz

Rectangular	75 to 200	0,6	0,6	0,45	0,3	0,3	0,3	0,3	0,3
"210" 400	0,6	0,6	0,45	0,3	0,2	0,2	0,2	0,2
"410" 800	0,6	0,6	0,3	0,15	0,15	0,15	0,15	0,15
"810" 1600	0,45	0,3	0,15	0,1	0,06	0,06	0,06	0,06
Round	75 to 200	0,10	0,1	0,15	0,15	0,3	0,3	0,3	0,3
"210" 400	0,06	0,1	0,1	0,15	0,2	0,2	0,2	0,2
"410" 800	0,03	0,06	0,06	0,1	0,15	0,15	0,15	0,15
"810" 1600	0,03	0,03	0,03	0,06	0,06	0,06	0,06	0,06

8.19. The decrease in octave sound power levels in dB in the bends of the air ducts should be determined from Table. 21. At an angle of rotation less than or equal to 45 °, the decrease in octave sound power levels is not taken into account.

For smooth turns of air ducts and turns of air ducts at right angles and equipped with guide blades, the decrease in octave sound power levels in dB should be taken from Table. 22.

Table 21

Turning width d in mm	Decrease in octave sound power levels in dB at the geometric mean frequency of the octave bands in Hz

Table 22

Turning width d in mm	Decrease in sound power levels in dB at the geometric mean frequency of the octave bands in Hz

125 - 250
260 - 500
510 - 1000
1100 - 2000

8.20. The decrease in octave sound power levels in dB with a change in the cross-section of the duct should, depending on the frequency and dimensions of the cross-section of the ducts, be determined:

a) when the cross-sectional dimensions of the duct in mm are less than those indicated in table. 23, according to the formula

(66)

Where t n- the ratio of the cross-sectional areas of the duct, equal to:

F 1 and F 2 - cross-sectional area of the duct before and after changing the cross-section in m 2;

b) with the dimensions of the cross-section of the duct in mm larger than those indicated in table. 23, according to the formulas:

(for> 1) (68)

(at<1) (69)

With a smooth transition of the duct from one section to another, the decrease in octave sound power levels is not taken into account.

8.21. The decrease in octave sound power levels in dB in the duct branch should be determined by the formula

(70)

Where t n- the ratio of the cross-sectional areas of the air ducts, equal to:

F - cross-sectional area of the duct before branching in m 2;

F hole, i- cross-sectional area of a separate branch duct in m 2;

The total cross-sectional area of the air ducts of all branches in m 2.

Table 23

Note. If the air duct of a separate branch in the branch is rotated by 90 °, then to the value in dB, obtained by the formula (70), the values of the decrease in octave sound power levels, determined according to table. 21 or 22.

8.22. The decrease in octave levels in sound power in dB as a result of sound reflection from the open end of the duct or grille should be determined from Table. 24.

Table 24

Duct diameter or square root of the cross-sectional area of the end of a rectangular duct or grille in mm	Decrease in octave sound power levels in dB at octave band center frequency in Hz




























2500
Note. The data in this table refers to the case when the duct ends flush with a wall or ceiling and is located, like an air distribution device (grille), at a distance of two or more duct diameters from other walls or ceilings. If the air duct or air distribution device (grille) ending flush with the enclosing structures is located closer to other enclosing structures of the room, then the decrease in octave sound power levels should be determined from Table. 24, assuming a value in dB for the diameter of the duct doubled.

Silencer design

8.23. In ventilation, air conditioning and air heating systems, tubular, plate and chamber silencers (Fig. 19) with sound-absorbing material should be used, as well as lining of air ducts and turns from the inside with sound-absorbing materials.

The choice of the muffler design should be made depending on the size of the duct, the permissible air flow rate and the required octave sound pressure level reduction.

Fig. 19. Scheme of muffler designs

a - lamellar with extreme plates; b - lamellar without edge plates; c - tubular rectangular section; g - tubular circular section; d - chamber; 1 - muffler casing; 2 - sound absorbing plate; 3 - channels for air; 4 - sound-absorbing lining; 5 - internal partition

8.24. Tubular silencers should be used for duct sizes up to 500 to 500 mm. For large air ducts, plate or chamber silencers should be used.

Note. Other types of mufflers may be used if justified. Honeycomb silencers are not allowed to be used in ventilation, air conditioning and air heating systems.

8.25. Plate mufflers should be designed from sound-absorbing plates installed in parallel at some distance from each other in a common casing.

The thickness of the sound-absorbing plates for mufflers should be taken according to table. 25.

Table 25

8.26. The decrease in octave sound power levels in dB in ducts and bends lined with sound-absorbing material from the inside and in mufflers should be determined from experimental data.

8.27. The decrease in octave sound pressure levels in dB in air intake devices (such as chambers) with sound-absorbing lining should be determined by the formula

(72)

Where - - full sound absorption of a separate chamber in m 2 (sound absorption of the floor is not taken into account);

Where Q- volumetric air flow through the muffler in m 3 / s;

Permissible air velocity in the muffler in m / s, taken depending on the available pressure loss and the level of noise generation in the muffler.

For residential and public buildings, auxiliary buildings and premises of enterprises, it is allowed to take the speed of air movement in the mufflers according to table. 26, if the length of the duct section to the room is at least 5 - 8 m.

Table 26

8.29. When designing ventilation, air conditioning and air heating, it is necessary to provide for the installation of a central silencer and place it as close as possible to the fan at the beginning of the ventilation network.

To muffle the noise generated in the ducts during the movement of the air flow, as well as the noise penetrating into the ducts from the outside from other noise sources, additional installation of noise mufflers should be provided on the branches of the air duct according to the calculation.

8.30. In rooms for ventilation equipment, the outside air of the silencer and the air duct after it, located within the room for ventilation equipment, should be soundproofed outside so that the octave values of airborne sound insulation by the walls of the silencer and the air duct are not less than the required value in dB, determined by the formula

Where L- octave sound pressure level in the room for ventilation equipment in dB, determined by formula (6) and in accordance with clauses. 8.5 - 8.7 of these standards;

The surface area of the muffler and air duct within the room for ventilation equipment in m 2;

- octave sound power levels radiated by the fan into the duct in dB, determined by the formula (57);

- total decrease in octave sound power levels in the duct sections (including mufflers) from the fan to the exit from the room for ventilation equipment in dB, determined in accordance with paragraphs. 8.16 and 8.26 of these standards.

To reduce the value of the required insulation from airborne noise of the walls of the muffler and air ducts, sound-absorbing lining of the inner surfaces of the enclosing structures of the room for ventilation equipment can be used.

Similar information.

4.4. The octave sound pressure levels L in dB at design points of rooms where there are several noise sources should be determined:

a) in the zone of direct and reflected sound according to the formula

The octave sound power level in dB generated by the i-th noise source;

The same as in formulas (1) and (2), but for the i-th noise source;

m is the number of noise sources closest to the design point (i.e. noise sources for which, where is the distance in m from the design point to the acoustic center of the nearest noise source);

n is the total number of noise sources in the room;

B and - the same as in formulas (1) and (3);

b) in the zone of reflected sound according to the formula

(6)

The first term in formula (6) should be determined by summing the sound power levels of noise sources according to table. 5, and if all noise sources have the same sound power, then

Table 5

Difference of two added levels in dB

Addition to the higher level required to obtain the total level in dB

Note. When using the table. 5, the levels in dB (sound power or sound pressure) should be added sequentially, starting with the maximum. First, the difference between the two added levels should be determined, then the additive corresponding to this difference. Then the additive must be added to the higher of the stacking levels. The resulting level is added to the next, etc.

4.5. The octave sound pressure levels L in dB at design points, if the noise source and design points are located on the territory of a residential building or on the site of the enterprise, should be determined by the formula

where is the octave sound power level in dB of the noise source;

Ф - the same as in formulas (1) and (2);

r is the distance in m from the noise source to the design point;

Spatial angle of sound emission, taken for noise sources located:

in space -

on the surface of the territory or enclosing structures of buildings and structures -

in a two-sided corner formed by the enclosing structures of buildings and structures -

Attenuation of sound in the atmosphere in dB / km, taken from table. 6.

determined by formula (7), if the design points are located at distances

r in m, greater than twice the maximum size of the noise source.

2. At a distance of m, the attenuation of sound in the atmosphere in the calculations is not

taken into account.

Table 6

Average geometric frequencies of octave bands in Hz

4.6. The octave sound power level of noise in dB that has passed through an obstacle (enclosing structure of a room) (Fig. 4, a, b) or a channel connecting two rooms or a room with the atmosphere, if the noise is generated by a source in the room (Fig. 4, c), should be determined by the formula

where L is the octave sound pressure level in dB at the obstruction, determined according to the instructions in note. 3 and 4 to this paragraph;

The area of the barrier in sq. M;

The reduction in the sound power level of noise in dB when sound passes through an obstacle, determined according to the instructions in note. 1 and 2 to this paragraph;

Correction in dB, taking into account the nature of the sound field when sound waves are incident on an obstacle, determined according to the instructions in note. 3 and 4 to this paragraph.

Notes: 1. If the enclosing structure is an obstacle

premises, then, where R is the airborne sound insulation of the enclosing

by design in the octave band, determined according to the requirements

Section 6 of these standards.

2. If the obstacle is a channel with an inlet area,

it is equal to the total decrease in sound power in the octave band in

channel determined in accordance with the requirement of section 8 of these standards.

3. When sound waves fall on an obstacle from the atmosphere = 0, and L

should be determined by formulas (7) and (11).

Fig. 4. Layout of noise sources and design points

ISh - noise source; РТ - calculated point; A - intermediate point; I - room

with sources of noise; II - atmosphere; III - room protected from noise

4.7. The octave sound power level of the noise in dB transmitted through the channel, if the noise is radiated by the source directly into the channel connected to another room or to the atmosphere (Fig. 5), should be determined by the formula

where is the sound power level in dB emitted by the noise source into the channel, determined in accordance with the instructions in sections (8) and (9) of these standards;

The total reduction in octave sound power level in dB along the sound path.

Fig. 5. Layout of the source (IS), emitting noise into the channel, and the design point (RT),

located in a noise-protected room in another building

Distance from the outlet of the channel to the outer fence of the room to be protected from noise;

Distances from the center of the radiating surface to the outer fence of the room to be protected from noise

The total decrease in the octave sound power level of the noise source along the sound propagation path in dB should be determined:

when sound is emitted through the duct outlet - in accordance with the instructions in Section 8 of these standards as the sum of the sound power levels in the elements of a duct or duct system, for example, a network of ventilation ducts;

when sound is emitted through the channel walls - according to the formula

Decrease in the octave sound power level in dB along the path of sound propagation between the noise source and the initial section of the channel through which the noise is emitted, determined in accordance with the requirements of Section 8 of these standards;

Area in square meters of the channel cross-section;

The area in square meters of the outer surface of the channel walls through which noise is emitted;

Isolation of airborne noise in dB by channel walls;

Decrease in sound power level in dB along the length of the considered section of the channel, determined in accordance with the requirements of clause 8 of these standards.

4.8. The octave sound power levels in dB of noise passing through the barrier into the protected room from noise, if the noise sources are located in a room located in another building (Fig. 5), should be determined sequentially.

First, it is necessary to determine the octave sound power levels of noise, in dB, transmitted through various obstacles from a room with a source (or several sources) of noise into the atmosphere, using formulas (8) and (9). Then you should determine the octave sound pressure levels of noise in dB at the intermediate design point A at the outer enclosing structure of the room protected from noise according to the formula (7), replacing L in it with, and with. After that, one should determine the total octave sound pressure levels in dB at point A using formula (11), and then determine the octave sound power levels of the noise transmitted into the room protected from noise, PR in dB using formula (8), replacing L in it with and taking = 0.

4.9. The octave sound pressure levels at the design point in dB passed through the obstacle should be determined using formulas (3), (6) or (7), replacing L with and with.

4.10. The octave sound pressure levels from multiple noise sources in dB should be determined as the sum of the sound pressure levels in dB at a selected design point from each noise source (or each obstacle through which noise enters the room or atmosphere) using the formula

To simplify the calculations, the summation of the sound pressure levels should be made according to Table 5 is similar to the summation of the sound power levels of noise sources.

4.11. The octave sound pressure level in dB at the design point for intermittent noise from a single source should be determined using formulas (1) - (3) or (7) for each time interval in minutes during which the value of the octave sound pressure level in dB remains constant, replacing L in the indicated formulas with.

Then, the equivalent octave sound pressure level in dB for the total time of exposure to noise T in minutes should be determined using the formula

(12)

where is the time in minutes during which the sound pressure level in dB remains constant;

Constant value of the octave sound pressure level in dB of intermittent noise per time in min;

T is the total time of exposure to noise in minutes.

Note. For the total time of exposure to noise T in min, it should be taken:

in production premises - the duration of the work shift;

in areas for which noise levels are established - the duration of the day - (from 7 to 23 hours) or night (from 23 to 7 hours).

4.12. The octave sound pressure level in dB at the design point for impulse noise from a single source should be determined by formulas (1) - (3) or (7) for each individual impulse of duration in min with the octave sound pressure value in dB, replacing L on the .

Then, you should determine the equivalent octave sound pressure level in dB for the selected time interval T in minutes according to formula (12), replacing it with, and with.

4.13. Equivalent octave sound pressure levels in dB at the design point for intermittent and impulsive noise from several noise sources should be determined in accordance with clause 4.10 of these standards, replacing with a by.

5. Determination of the required noise reduction

5.1. The required reduction in octave sound pressure levels in dB should be determined separately for each noise source if noise from several noise sources arrives at the design point.

Note. This rule does not apply to the determination of the required noise reduction from noise sources in industrial premises (in the shops of the textile industry, woodworking, metalworking, etc.).

5.2. The required reduction in octave sound pressure levels in dB at a design point in a room or on the territory for one source of noise or several, differing from each other in octave sound pressure levels by less than 10 dB, should be determined:

a) for one noise source according to the formula

b) for several noise sources according to the formula

where L and are the octave sound pressure levels in dB generated by one or a separately considered noise source at the design point, respectively, determined in accordance with paragraphs. 4.2 - 4.8 of these standards;

Permissible octave sound pressure level in dB at the design point, determined in accordance with paragraphs. 3.4 and 3.5 of these standards;

n is the total number of noise sources taken into account, determined in accordance with paragraphs. 5.4 and 5.5 of these standards.

5.3. The required reduction in octave sound pressure levels in dB at a design point in a room or on the territory from several noise sources differing from each other in octave sound pressure levels by more than 10 dB should be determined:

a) for each noise source with higher sound pressure levels according to the formula

where is the total number of noise sources with higher sound pressure levels;

b) for each noise source with lower sound pressure levels according to the formula

= , (16)

where n is the total number of noise sources taken into account, determined in accordance with paragraphs. 5.4 and 5.5 of these standards.

5.4. The total number of noise sources n in determining the required reduction in octave sound pressure levels in dB at design points located on the territory of residential buildings or industrial sites should include all noise sources located in these areas (units, installations, etc.) ), as well as the number of elements of the enclosing structures of buildings and structures (walls or windows, coatings, etc.), oriented towards the design points through which the noise from the room enters the design point, as well as the outlets (openings) of channels and shafts emitting noise into the atmosphere.

When determining in dB for design points in a room protected from external noise sources, the total number n of noise sources taken into account should include the number of mechanically induced ventilation systems serving this room, as well as the number of elements of enclosing structures through which noise penetrates into premises.

Note. Noise sources located in a room protected from noise should not be taken into account, but the value should be increased by 5 dB.

5.5. In the total number of noise sources n, one should not take into account those noise sources that create at the design point the sound pressure levels in dB below the permissible values, in each octave band, i.e. for which the relation

In this case, the value in dB should be determined by the formula

where is the number of noise sources whose sound pressure levels are at least 10 dB lower.

5.6. When determining the octave sound pressure levels in dB from various noise sources using formula (7) for calculating the required reduction in sound pressure levels in dB at the design point using formulas (15) and (16), it is allowed to take the distances to noise sources the same and equal to the arithmetic mean in cases when 1.5 r min for different noise sources.

For noise sources of the same radiated power, in this case, it is sufficient to calculate the required decrease in the sound pressure level for one of the sources, taking

The required reduction in sound pressure level in dB will then be the same for all noise sources.

5.7. The required total reduction in octave sound pressure levels in dB in rooms with noise sources when all noise sources are operating simultaneously should be determined by the formula

where is the octave sound pressure level at the design point from all noise sources in dB, determined in accordance with clause 4.4 of these standards, replacing L with;

Permissible octave sound pressure level in dB at the design point, determined in accordance with paragraphs. 3.4. and 3.5 of these standards.

6. Sound insulation of building envelopes

Soundproofing standards for building envelopes

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

6.2. The airborne sound insulation index in dB by the enclosing structure with a known (calculated or measured) frequency characteristic of airborne sound insulation should be determined by the formula

where is the correction determined by comparing the frequency response of airborne noise insulation by the enclosing structure with the standard frequency response of airborne noise isolation (Fig. 6) according to the method described in Appendix. one.

Fig. 6. Standard frequency response of isolation

airborne noise enclosing structure

6.3. The index of the reduced impact noise level in dB under the overlap with a known (calculated or measured) frequency characteristic of the reduced impact noise level should be determined by the formula

where is the correction determined by comparing the frequency response of the reduced impact noise level under the overlap with the standard frequency response of the reduced impact noise level (Fig. 7) according to the method described in Appendix. one.

Fig. 7. Normative frequency response of the reduced level

impact noise under the ceiling

6.4. Regulatory indices of airborne noise insulation by enclosing structures in dB and the reduced level of impact noise under the ceiling in dB in residential and public buildings, as well as auxiliary buildings and premises of industrial enterprises, should be taken according to table. 7.

Table 7

The name and location of the enclosing structure

Airborne Sound Insulation Index

Index of the reduced level of impact noise in dB

Residential buildings

Overlapping between rooms of apartments

Overlappings between apartment rooms and unused attic spaces

Overlappings between the premises of the apartment and basements, hallways and used attic spaces

Overlappings between the premises of the apartments and the shops located below

Overlaps between the premises of the apartment and the restaurants located below, gyms, cafes and other similar premises

Overlapping between rooms in a two-story apartment

Overlaps separating the premises of cultural and consumer services of hostels from each other and from common areas (halls, lobbies, corridors)

Walls and partitions between apartments, between apartment premises and staircases, halls, corridors, lobbies

Walls between apartment premises and shops

Walls between the premises of the apartment and restaurants, gyms, cafes and other similar premises

Partitions without doors between rooms, between the kitchen and the room in the apartment

Partitions between rooms and a sanitary unit of one apartment

The entrance doors of the apartments, overlooking the stairwells, halls, lobbies and corridors

Stairwells and marches.

* The requirement should be made for the transmission of impact noise into a room protected from noise by impact on the floor of a room not protected from noise.

Walls and partitions separating the premises of cultural and consumer services of hostels from each other and from common areas (halls, lobbies, staircases)

Hotels

Overlapping between rooms:

Overlappings separating rooms from common areas (lobbies, halls, buffets):

"" second "

* The requirement should be made for the transmission of impact noise into a room protected from noise by impact on the floor of a room not protected from noise.

Overlaps separating rooms from restaurants, cafes, canteens, kitchens:

"" second "

* The requirement should be made for the transmission of impact noise into a room protected from noise by impact on the floor of a room not protected from noise.

Walls and partitions between rooms:

Walls and partitions separating rooms from common areas (staircases, lobbies, halls, buffets):

"" second "

Walls and partitions separating rooms from restaurants, cafes, canteens, kitchens:

"" second "

Buildings of administrations, party and public organizations

Overlapping between working rooms, offices, secretariats and separating working rooms, offices, secretariats from common areas (lobbies, halls)

Overlaps separating work rooms, offices from work rooms that are not protected from noise (machine bureau, teletype rooms, etc.)

Walls and partitions between working rooms

Walls and partitions separating work rooms, secretariats from common areas (staircases, lobbies, halls) and workers, not protected from noise of the premises

Walls and partitions separating offices from workers, premises and common areas not protected from noise

Hospitals and sanatoriums

Overlapping between wards, doctors' offices

Overlapping between operating rooms and separating operating rooms from wards and offices

Overlaps separating wards, doctors' offices from common areas (lobbies, halls)

Overlaps separating chambers, offices from dining rooms, kitchens

* The requirement should be made for the transmission of impact noise into a room protected from noise by impact on the floor of a room not protected from noise.

Walls and partitions between wards, doctors' offices

Walls and partitions between operating rooms and separating operating rooms from other rooms. Walls and partitions separating chambers and offices from dining rooms, kitchens

Walls and partitions separating chambers, offices from common areas (staircases, lobbies, halls)

Schools and other educational institutions

Overlaps between classrooms, classrooms and classrooms and separating classrooms, classrooms and auditoriums from common areas (corridors, lobbies, halls)

Overlapping music classes in secondary schools

Overlapping music classes in higher education institutions

Walls and partitions between classrooms, classrooms and classrooms and separating classrooms, classrooms and auditoriums from common areas (stairwells, lobbies, halls, recreation)

Walls and partitions between music classes of secondary educational institutions and separating them from common areas (staircases, lobbies, halls, recreation)

Walls and partitions between music classes in higher education

Nursery-kindergartens

Overlapping between group rooms, bedrooms and between other children's rooms

Overlaps separating group rooms, bedrooms from kitchens

Walls and partitions between group rooms, bedrooms and between other children's rooms

Walls and partitions separating group rooms, bedrooms from kitchens.

Auxiliary buildings and premises of industrial enterprises

Overlaps between rooms for recreation, training sessions, health centers, work rooms of departments and design bureaus, offices, premises of public organizations and separating these premises from common areas (lobbies, dressing rooms)

Overlappings between laboratory rooms, red corners, meeting rooms, dining rooms and separating these rooms from the rooms indicated in pos. 44 of this table

Walls and partitions between work rooms of offices and design bureaus, premises of public organizations

Walls and partitions between rooms for recreation, training sessions, health centers, separating these premises from the working rooms of departments and design bureaus, offices, premises of public organizations and separating all these premises from common areas (lobbies, dressing rooms, staircases)

Walls and partitions between laboratory rooms, red corners, meeting rooms, dining rooms and separating these rooms from the rooms indicated in pos. 44 of this table

Note. The values of the indices of airborne noise insulation by the enclosing structures and the reduced level of impact noise under the ceilings for living rooms of dormitories should be taken the same as for the enclosing structures of apartments in residential buildings.

1. Calculation of the expected sound pressure levels at the design point and the required noise reduction.

If there are several noise sources with different levels of radiated sound power in the room, then the sound pressure levels for geometric mean frequencies of 63, 125, 250, 500, 1000, 2000, 4000 and 8000 Hz and the calculated point should be determined by the formula:

L - expected octave pressure levels at the design point, dB; χ is an empirical correction factor taken depending on the ratio of the distance r from the design point to the acoustic center to the maximum overall size of the source 1max, Fig. 2 (guidelines). The acoustic center of a noise source located on the floor is the projection of its geometric center onto the horizontal plane. Since the ratio r / lmax is in all cases, we will take and

determined by table. 1 (guidelines). Lpi - octave sound power level of the noise source, dB;

Ф - directional factor; for sources with uniform radiation, F = 1 is taken; S is the area of an imaginary surface of regular geometric shape surrounding the source and passing through the calculated point. In the calculations, take, where r is the distance from the calculated point to the noise source; S = 2πr 2

2	x	3,14	x	7,5
2	x	3,14	x	11
2	x	3,14	x	8
2	x	3,14	x	9,5
2	x	3,14	x	14	2 = 1230.88 m 2

ψ- coefficient taking into account the violation of the diffuseness of the sound field in the room, taken according to the graph in Fig. 3 (guidelines), depending on the ratio of the constant room B to the area of the enclosing surfaces of the room

B is the constant of the room in the octave frequency bands, determined by the formula, where according to the table. 2 (guidelines); m - frequency factor determined from the table. 3 (guidelines).

For 250 Hz: μ = 0.55; m 3

For 250 Hz: μ = 0.7; m 3

For 250 Hz: ψ = 0.93

For 250 Hz: ψ = 0.85

t is the number of noise sources closest to the design point, for which (*). In this case, the condition is satisfied for all 5 sources, therefore m = 5.

n is the total number of noise sources in the room, taking into account the coefficient

simultaneity of their work.

Find the expected octave sound pressure levels for 250 Hz:

L = 10lg (1x8x10 / 353.25 + 1x8x10 / 759.88 + 1x3.2x10 / 401.92 + 1x2x10 / 566.77 + 1x8x10 / 1230.88 + 4 x 0.93 x (8x10 + 8x10 +

3.2x10 + 2x10 + 8x10) / 346.5) = 93.37dB

Find the expected octave sound pressure levels for 500 Hz:

L = 10lg (1x1.6x10 / 353.25 + 1x5x10 / 759.88 + 1x6.3x10 / 401.92 +

1x 1x10 / 566.77 + 1x1.6x10 / 1230.88 + 4 x 0.85 x (1.6x10 + 5x10 +

6.3x10 + 1x10 + 1.6x10) / 441) = 95.12 dB

The required reduction in sound pressure levels at the design point for eight

octave bands by the formula:

where

Required reduction of sound pressure levels, dB;

Calculated octave sound pressure levels, dB;

L add - permissible octave sound pressure level insulated from noise

premises, dB, tab. 4 (guidelines).

For 250 Hz: ΔL = 93.37 - 77 = 16.37 dB For 500 Hz: ΔL = 95.12 - 73 = 22.12 dB

2. Calculation of soundproof fences, partitions.

Soundproof fences, partitions are used to separate "quiet" rooms from adjacent "noisy" rooms; are made of dense, other materials. It is possible to arrange doors and windows in them. The selection of the construction material is made according to the required soundproofing ability, the value of which is determined by the formula:

- total octave sound power level

emitted by all sources determined using the table. 1 (guidelines).

For 250Hz: dB

For 500 Hz:

B and - constant of the isolated room

B 1000 = V / 10 = (8x20x9) / 10 = 144 m 2

For 250 Hz: μ = 0.55 V And = V 1000 μ = 144 0.55 = 79.2 m 2

For 500 Hz: μ = 0.7 V And = V 1000 μ = 144 0.7 = 100.8 m 2

t - the number of elements in the fence (partition with a door t = 2) S i - area of the fence element

S walls = BxH - S doors = 20 9 - 2.5 = 177.5 m 2

For 250 Hz:

R required wall = 112.4 - 77 - 10lg79.2 + 10lg177.5 + 10lg2 = 41.9dB

R required door = 112.4 - 77 - 10lg79.2 + 10lg2.5 + 10lg2 = 23.4dB

For 500 Hz:

R required wall = 115.33 - 73 - 10lg100.8 + 10lg177.5 + 10lg2 = 47.8dB

R required door = 112.4 - 73 - 10lg100.8 + 10lg2.5 + 10lg2 = 29.3dB

Soundproof fencing consists of a door and a wall, we will select the material

structures according to table. 6 (guidelines).

Door - a blind panel door 40mm thick, lined on both sides with 4mm plywood with sealing gaskets. Wall - brickwork 1 brick on both sides.

3.3 sound absorbing linings

They are used to reduce the intensity of reflected sound waves.

Sound-absorbing facings (material, sound absorption design, etc.) should be made according to the data in Table. 8 depending on the required noise reduction.

The value of the possible maximum reduction in sound pressure levels at the design point when using the selected sound-absorbing structures is determined by the formula:

В - permanent premises before installation of sound-absorbing cladding in it.

B 1 is the constant of the room after installing a sound-absorbing structure in it and is determined by the formula:

A = α (S ogr - S obl)) - the equivalent area of sound absorption of surfaces not occupied by sound-absorbing lining;

α is the average sound absorption coefficient of surfaces not occupied by sound-absorbing lining and is determined by the formula:

For 250Hz: α = 346.5 / (346.5 + 2390) = 0.1266

For 500 Hz: α = 441 / (441 + 2390) = 0.1558

Sobl - the area of sound-absorbing facings

Sobl = 0.6 S limit = 0.6 x 2390 = 1434 m 2 For 250 Hz: A 1 = 0.1266 (2390 - 1434) = 121.03 m 2 For 500 Hz: A 1 = 0.1558 (2390 - 1434) = 148.945 m 2

ΔА is the value of additional sound absorption introduced by the structure of the sound-absorbing lining, m 2 is determined by the formula:

Reverb sound absorption coefficient of the selected cladding design in the octave frequency band, determined according to Table 8 (guidelines). Choosing a super thin fiber

ΔА = 1 x 1434 = 1434 m 2

structures, determined by the formula:

For 250 Hz: = (121.03 + 1434) / 2390 = 0.6506;

B 1 = (121.03 + 1434) / (1 - 0.6506) = 4450.57 m 2

ΔL = 10lg (4450.57 x 0.93 / 346.5 x 0.36) = 15.21 dB ".

For 500 Hz: = (148.945 + 1434) / 2390 = 0.6623;

B 1 = (148.945 + 1434) / (1 - 0.6623) = 4687.43 m 2

ΔL = 10lg (4687.43 x 0.85 / 441 x 0.35) = 14.12 dB.

For 250 Hz and 500 Hz, the selected sound-absorbing lining will not provide the required noise reduction in octave bands because:

Given: In a working room with a length of A m, a width of B m, and a height of N m
placed noise sources - ISH1, ISH2, ISH3, ISH4 and ISH5 with sound power levels. The ISh1 noise source is enclosed in a casing. At the end of the workshop there is an auxiliary service room, which is separated from the main workshop by a partition with an area door. The calculated point is located at a distance r from the noise sources.

4. Sound pressure levels at the design point - PT, compare with the permissible standards, determine the required noise reduction at workplaces.

5. Soundproofing ability of the partition and doors in it, choose the material for the partition and the door.

6. Soundproofing capacity of the casing for the ISh1 source. The noise source is installed on the floor, its dimensions in plan are (a x b) m, and its height is h m.

4. Reducing noise when installing sound-absorbing cladding at the site of the workshop. Acoustic calculations are carried out in two octave bands at geometric mean frequencies of 250 and 500 Hz.

Initial data:

The quantity	250Hz	500Hz	The quantity	250Hz	500Hz
	103	100
	97	92
	100	99
	82	82
	95	98

Design points in production and auxiliary premises of industrial enterprises are selected at workplaces and (or) in areas of permanent residence of people at a height of 1.5 m from the floor. In rooms with one source of noise or with several sources of the same type, one design point is taken at the workplace in the area of direct sound of the source, the other - in the area of reflected sound at the place of permanent residence of people who are not directly related to the operation of this source.

In a room with several sources of noise, the sound power levels of which differ by 10 dB or more, the design points are selected at workplaces at the sources with the maximum and minimum levels. In a room with group placement of equipment of the same type, design points are selected at the workplace in the center of groups with maximum and minimum levels.

The initial data for the acoustic calculation are:

plan and section of the premises with the location of technical and engineering equipment and design points;

(material, thickness, density, etc.); information about the characteristics of the building envelope

noise characteristics and geometric dimensions of noise sources.

Noise characteristics of technological and engineering equipment in the form of octave sound power levels, corrected sound power levels, as well as equivalent and maximum corrected sound power levels for intermittent noise sources must be specified by the manufacturer in the technical documentation.

It is allowed to represent noise characteristics in the form of octave sound pressure levels or sound levels at the workplace (at a fixed distance) with single operating equipment.

Octave sound pressure levels, dB, at the design points of commensurate rooms (with the ratio of the largest geometric size to the smallest not more than 5) when operating one noise source should be determined by the formula

where is the octave sound power level, dB;

Coefficient taking into account the influence of the near field in cases where the distance is less than twice the maximum size of the source (taken according to Table 2);

Ф - directivity factor of the noise source (for sources with uniform radiation Ф = 1);

Spatial angle of radiation of the source, glad. (taken according to table 3);

Distance from the acoustic center of the noise source to the design point, m (if the exact position of the acoustic center is not known, it is assumed to coincide with the geometric center);

The coefficient taking into account the violation of the diffuseness of the sound field in the room (taken according to Table 4, depending on the average sound absorption coefficient);

B is the acoustic constant of the room, m ^ 2, determined by the formula

where A is the equivalent area of sound absorption, m ^ 2, determined by the formula

where is the sound absorption coefficient of the i-th surface;

The area of the i-th surface, m ^ 2;

Equivalent sound absorption area of the j-th piece absorber, m ^ 2;

Number of j-th piece absorbers;

Average sound absorption coefficient, determined by the formula

where is the total area of the enclosing surfaces of the room, m ^ 2.

Table 4

Table 6

Boundary radius m, in a room with one noise source - the distance from the acoustic center of the source, at which the energy density of the direct sound is equal to the energy density of the reflected sound, is determined by the formula

If the source is located on the floor of the room, the boundary radius is determined by the formula

The calculated points at a distance of up to 0.5 can be considered as being in the range of direct sound. In this case, the octave sound pressure levels should be determined using the formula

Octave sound pressure levels L, dB, at design points of a commensurate room with several noise sources should be determined by the formula

where is the octave sound power level of the i-th source, dB;

The same as in formulas (3.1) and (3.6), but for the i-th source;

m is the number of noise sources closest to the design point (located at a distance, where is the distance from the design point to the acoustic center of the nearest noise source);

n is the total number of noise sources in the room;

k and B are the same as in formulas (3.1) and (3.8).

If all n sources have the same sound power, then

If the noise source and the design point are located on the territory, the distance between them is greater than twice the maximum size of the noise source and there are no obstacles between them screening noise or reflecting noise in the direction of the design point, then the octave sound pressure levels L, dB, at design points, should be determined :

with a point source of noise (separate installation on site, transformer, etc.) according to the formula

with an extended source of limited size (wall of an industrial building, a chain of ventilation system shafts on the roof of an industrial building, a transformer substation with a large number of openly located transformers) - according to the formula

where is the same as in formulas (2.1) and (2.7);

Attenuation of sound in the atmosphere, dB / km, taken according to Table 5.

Table 7

At a distance of m, the attenuation of sound in the atmosphere is not taken into account.

When noise penetrates the insulated room from the territory, the octave sound pressure level outside at a distance of 2 m from the enclosing structure is determined by formulas (3.11) and (3.12);

R - airborne noise insulation by the enclosing structure through which noise penetrates, dB;

S is the area of the enclosing structure, m ^ 2;

Acoustic constant of the insulated room, m ^ 2;

If the enclosing structure consists of several parts with different sound insulation (for example, a wall with a window and a door), R is determined by the formula

where is the area of the i-th part, m ^ 2;

Isolation of airborne noise with the i-th part, dB.

If the building envelope consists of two parts with different sound insulation, R is determined by the formula

At a certain ratio of areas, it is allowed, instead of sound insulation of the enclosing structure R, when calculating according to formula (3.13), to introduce sound insulation of the weak part of the composite fence and its area.

Equivalent and maximum sound levels, dB, generated by external transport and penetrating into premises through an external wall with a window (s), should be determined by the formula

where is the equivalent (maximum) sound level outside two meters from the fence, dBA;

Isolation of external traffic noise outside the window, dBA;

Window (s) area, m ^ 2;

k is the same as in formula (3.1).

For premises of residential and office buildings, hotels, hostels, etc. with an area of up to 25 m ^ 2, dB, is determined by the formula

The octave sound pressure levels in the room to be protected from noise, in cases where the noise sources are located in another building, should be determined in several stages:

determine the octave sound power levels of noise, dB, transmitted through an external fence (or several fences) into the territory, according to the formula

where is the octave sound power level of the i-th source, dB;

Acoustic constant of the room with the source (s) of noise, m ^ 2;

S is the area of the fence, m ^ 2;

R - isolation of airborne noise by a fence, dB;

determine the octave sound pressure levels for the auxiliary design point at a distance of 2 m from the outer fence of the room protected from noise according to formulas (3.10) or (3.11) from each of the noise sources (ISH 1 and ISH 2, Figure 1). When calculating, it should be borne in mind that for the design points within the plane of the building wall (in Figure 1 - complex noise source IS 1), a correction is introduced for the radiation directivity dB. determine the total octave sound pressure levels, dB, at an auxiliary design point (two meters from the outer fence of the room protected from noise) from all noise sources according to the formula

where is the sound pressure level from the i-th source, dB;

determine the octave sound pressure levels L, dB, in the room protected from noise according to the formula (3.13), replacing it with.

With unstable noise, octave sound pressure levels, dB, at the design point should be determined by formulas (3.1), (3.7), (3.8), (3.9), (3.11), (3.12) or (3.13) for each time interval, min ., during which the level remains constant, replacing L in the indicated formulas with.

Equivalent octave sound pressure levels, dB, for the total exposure time T, min., Should be determined by the formula

where is the exposure time of the level, min;

Octave level over time, dB.

For the total exposure time, time T is taken: and in production and office premises - the duration of the work shift; in residential and other premises, as well as in areas where the norms are set separately for day and night - the duration of the day is 7.00-23.00 and the night is 23.00-7.00.

In the latter case, it is allowed to take for the exposure time T during the day - a four-hour period with the highest levels, at night - a period of 1 hour with the highest levels.

Equivalent sound levels of intermittent noise, dBA, should be determined by formula (3.20), replacing with and with.

Sound levels of process and ventilation equipment

The acoustic characteristics of ventilation equipment are given in the appendix and technological separately for ventilation systems and separately for different areas. When determining the parameters of these sources, the following simplifying assumptions were made towards increasing the acoustic characteristics of these sources:

all terminal branches of ventilation systems are brought out to the roof of the corresponding buildings, which, firstly, excludes the effects of shielding when sound propagates over long distances, and, secondly, overestimates the sound levels of the total noise sources, because some ventilation systems of a technological type operate in a closed cycle.

All technological equipment is located inside hangar-type buildings without soundproof / sound-absorbing barriers and near the walls / windows of these premises. In this case, it is assumed that all the windows of these buildings are affected from the inside by the noise of the maximum level of all the measured noises at the workplaces.

The total sound levels of technological equipment will make it possible to calculate the acoustic power of sound sources, which are the windows of the corresponding buildings. The calculation results are presented in the appendix.

Pairwise comparison of the sound power levels (USM) emitted by the process equipment through the windows of the enclosures with USM from the ventilation equipment of the corresponding enclosures is given in Table 8.

Tab. 8. UZM from technological and ventilation equipment

Body no.
Lw outside windows, dBA
Lw veins, dBA

The analysis of the calculations presented in Table 5 shows that the noise from the operation of technological equipment, with all the assumptions made in the direction of increasing noise, is noticeably lower than the noise of ventilation systems and meets the requirements of the remote control. It can be seen from the table that against the background of the noise of the ventilation systems of each of the buildings, the contribution of the noise of the technological equipment penetrating through the windows and openings of the buildings can be neglected. As the acoustic characteristics of the equipment (Cyclone), the estimates of the sound pressure levels are taken. Data refer to sound levels measured at a distance of 1m from the equipment.

AT CALCULATION POINTS

7.1. Design points in production and auxiliary premises of industrial enterprises are selected at workplaces and (or) in areas of permanent residence of people at a height of 1.5 m from the floor. In a room with one source of noise or with several sources of the same type, one design point is taken at the workplace in the area of direct sound of the source, the other - in the area of reflected sound at the place of permanent residence of people who are not directly related to the operation of this source.

7.2. The initial data for the acoustic calculation are:

Plan and section of the premises with the location of technological and engineering equipment and design points;

Information about the characteristics of the building envelope (material, thickness, density, etc.);

Noise characteristics and geometric dimensions of noise sources.

7.3. Noise characteristics of technological and engineering equipment in the form of octave sound power levels, corrected sound power levels, as well as equivalent and maximum corrected sound power levels for intermittent noise sources must be indicated by the manufacturer in the technical documentation.

It is allowed to represent noise characteristics in the form of octave sound pressure levels L or sound levels at the workplace (at a fixed distance) with single operating equipment.

7.4. Octave sound pressure levels L, dB, at design points of commensurate rooms (with the ratio of the largest geometric size to the smallest not more than 5) when operating one noise source should be determined by the formula

, (1)

where is the octave sound power level, dB;

The coefficient taking into account the influence of the near field in cases where the distance r is less than twice the maximum size of the source (r< 2) (принимают по таблице 2);

Ф - directivity factor of the noise source (for sources with uniform radiation Ф = 1);

Spatial angle of radiation of the source, glad. (taken according to table 3);

r is the distance from the acoustic center of the noise source to the design point, m (if the exact position of the acoustic center is unknown, it is assumed to coincide with the geometric center);

k is the coefficient taking into account the violation of the diffuseness of the sound field in the room (taken according to Table 4, depending on the average sound absorption coefficient);

B is the acoustic constant of the room, m2, determined by the formula

A is the equivalent sound absorption area, m2, determined by the formula

, (3)

Sound absorption coefficient of the i-th surface;

Area of the i-th surface, m2;

Equivalent sound absorption area of the j-th piece absorber, m2;

Number of j-th piece absorbers, pcs;

Average sound absorption coefficient, determined by the formula

The total area of the enclosing surfaces of the room, m2.

table 2

┌─────────────────────┬────────────────────┬─────────────────────┐

│ r │ chi │ 10 lg chi, dB │

│ ----- │ │ │

│ l │ │ │

│ max │ │ │

│0,6 │3 │5 │

├─────────────────────┼────────────────────┼─────────────────────┤

│0,8 │2,5 │4 │

├─────────────────────┼────────────────────┼─────────────────────┤

│1,0 │2 │3 │

├─────────────────────┼────────────────────┼─────────────────────┤

│1,2 │1,6 │2 │

├─────────────────────┼────────────────────┼─────────────────────┤

│1,5 │1,25 │1 │

├─────────────────────┼────────────────────┼─────────────────────┤

│2 │1 │0 │

└─────────────────────┴────────────────────┴─────────────────────┘

Table 3

Radiation conditions	Omega, glad.	10 lg Omega, dB
Into space - a source on a column in a room, on a mast, a pipe
Into half-space - a source on the floor, on the ground, on the wall
In 1/4 of the space - a source in a dihedral angle (on the floor close to one wall)
In 1/8 of the space - a source in a triangular angle (on the floor close to two walls)

Table 4

┌────────────────────┬────────────────────┬──────────────────────┐

│ alpha │ k │ 10 lgk, dB │

│ Wed │ │ │

│0,2 │1,25 │1 │

├────────────────────┼────────────────────┼──────────────────────┤

│0,4 │1,6 │2 │

├────────────────────┼────────────────────┼──────────────────────┤

│0,5 │2,0 │3 │

├────────────────────┼────────────────────┼──────────────────────┤

│0,6 │2,5 │4 │

└────────────────────┴────────────────────┴──────────────────────┘

7.5. Boundary radius, m, in a room with one noise source - the distance from the acoustic center of the source, at which the energy density of the direct sound is equal to the energy density of the reflected sound, is determined by the formula

If the source is located on the floor of the room, the boundary radius is determined by the formula

. (6)

The calculated points at a distance of up to 0.5 can be considered as being in the range of direct sound. In this case, the octave sound pressure levels should be determined using the formula

The calculated points at a distance of more than 2 can be considered as being in the range of the reflected sound. In this case, the octave sound pressure levels should be determined using the formula

7.6. Octave sound pressure levels L, dB, at design points of a commensurate room with several noise sources should be determined by the formula

, (9)

where is the octave sound power level of the i-th source, dB;

The same as in formulas (1) and (6), but for the i-th source;

m is the number of noise sources closest to the design point (located at a distance<= 5, где- расстояние от расчетной точки до акустического центра ближайшего источника шума);

n is the total number of noise sources in the room;

k and B - the same as in formulas (1) and (8).

If all n sources have the same sound power, then

. (10)

7.7. If the noise source and the design point are located on the territory, the distance between them is greater than twice the maximum size of the noise source and there are no obstacles between them screening the noise or reflecting noise in the direction of the design point, then the octave sound pressure levels L, dB, at the design points should be determined:

with a point source of noise (a separate installation on the territory, a transformer, etc.) - according to the formula

where, r, Ф, - the same as in formulas (1) and (7);

Attenuation of sound in the atmosphere, dB / km, taken according to Table 5.

Table 5

┌──────────────────────┬────┬────┬─────┬────┬────┬─────┬────┬────┐

│ Geometric mean │63 │125 │250 │500 │1000│2000 │4000│8000│

│ octave frequencies │ │ │ │ │ │ │ │ │

│ bands, Hz │ │ │ │ │ │ │ │ │

├──────────────────────┼────┼────┼─────┼────┼────┼─────┼────┼────┤

│beta, dB / km │0 │0.7 │1.5 │3 │6 │12 │24 │48 │

│ a │ │ │ │ │ │ │ │ │

└──────────────────────┴────┴────┴─────┴────┴────┴─────┴────┴────┘

At distance r<= 50 м затухание звука в атмосфере не учитывают.

7.8. The octave sound pressure levels L, dB, at design points in the insulated room, penetrating through the enclosing structure from the adjacent room with the noise source (s) or from the territory, should be determined by the formula

where is the octave sound pressure level in a room with a noise source at a distance of 2 m from the fence dividing the room, dB, determined by formulas (1), (8) or (9); in case of noise penetrating into the insulated room from the territory, the octave sound pressure level outside at a distance of 2 m from the enclosing structure is determined by formulas (11) or (12);

R - insulation of airborne noise by the enclosing structure through which noise penetrates, dB;

S is the area of the enclosing structure, m2;

Acoustic constant of the insulated room, m2;

If the enclosing structure consists of several parts with different sound insulation (for example, a wall with a window and a door), R is determined by the formula

, (14)

where is the area of the i-th part, m2;

Isolation of airborne noise with the i-th part, dB.

If the building envelope consists of two parts with different sound insulation (>), R is determined by the formula

. (15)

When >> at a certain ratio of areas, it is allowed to introduce sound insulation of the weak part of the composite fence and its area instead of sound insulation of the enclosing structure R when calculating using formula (13).

Equivalent and maximum sound levels, dBA, generated by external transport and penetrating into premises through an external wall with a window (s), should be determined by the formula

where is the equivalent (maximum) sound level outside at a distance of 2 m from the fence, dBA;

Isolation of external traffic noise by a window, dBA;

Window (s) area, m2;

k is the same as in formula (1).

For premises of residential and office buildings, hotels, hostels, etc. with an area of up to 25 m2, dBA, is determined by the formula

. (17)