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Sound Attenuators Of Shahrokhi MFG Co

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Page 1: Sound Attenuators

Bµo¼£ Akæ

SOUND ATTENUATORS

Page 2: Sound Attenuators

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Page 3: Sound Attenuators

SOUND ATTENUATORS

(FIGURE 1)

APPLICATION

Shahrokhi sound attenuators are designed

to suit H.V.A.C. Applications for sound

absorbing in ductworks such as sound

recording and broadcasting, Amphitheatres,

Conference halls and etc.Passing through the sound attenuator

provide uniform and quiet airflow patterns so

the sound level and air pressure decrease.The sound attenuators are used for supply,

return and exhaust air which installed inside

the main or branch ductworks (Figure 1).

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Page 4: Sound Attenuators

DESCRIPTION

These sound attenuators are made of a

casing with a number of sound baffles.The sound baffles installed parallel inside

the casing with different distances and

thicknesses (Figure 2).

The sound attenuator casing join to ductw-

ork line with flanges at both ends (Figure 3).These casings are constructed from 12 inch

up to 116 inch in increments 10 inch.

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(FIGURE 2)

(FIGURE 3)

L

DW

H

S S/2

1 1

6" 6"

1 /2" x 1 /2"

H

Page 5: Sound Attenuators

The baffles are filled with non-inflammable

sound absorbing material , erosion and

hygroscopic protected and allowing

velocities up to 20 m.p.s.These sound baffles frame is constructed in

two different shapes with screen mesh or

perforated sheets.Either the both ends of the sound baffles

may be constructed in conic or curved forms

to suit airflow lead (Figure 4).

It is possible to supply the sound baffles

separately to install them inside the ductw-

orks (Figure 5).

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(FIGURE 5)

(FIGURE 4)

L1"

1"

D

H

1"

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3mm

DUCT

SOUND

ABSORBING

PERFORATED

SHEET

GALV. FRAME

Page 6: Sound Attenuators

ORDERING CODE

Shahrokhi sound attenuators with following

ordering code are specified.

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SH : Shahrokhi manufacture

SDA : Sound attenuator

T : type : 24 : Air gap 2 inch and baffle thick. 4 inch

44 : Air gap 4 inch and baffle thick. 4 inch

48 : Air gap 4 inch and baffle thick. 8 inch

88 : Air gap 8 inch and baffle thick. 8 inch

W x H x L : Width (inch) x Height (inch) x Length (inch)

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: 24

: 44

: 48

: 88

: ������ "�� : T

f�?�GW�%�J "�'&�GW�%�J ��5�GW�%�Jx x : W x H x L

SH.SDA.T-W x H x L

MATERIAL

High quality 1.5mm. thickness iron

galvanized sheet for the sound casing and

1mm. thickness for the sound baffles finish.

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Page 7: Sound Attenuators

SOUND ATTENUATOR

SELECTION METHOD

1) From table No (1) noise criteria are esti-

mated in different spaces.

2) From table No (2) noise criteria in db. are

estimated in different frequencies in HZ.

3) Total sound creation which is effected by

Airhandling unit , motor power , airflow

quantity , fan static pressure and ambient

sound calculated by designer.

4) Some of this sound absorbed from the

total sound creation by floor area , type of

room surface , end cap duct , branch of main

duct , length duct , bends and connections.

5) The remain sound could be reduced up to

noise criteria by sound attenuator. Tables

No. (3-6) show sound absorption in db for

different frequencies for air gaps and sound

baffles thicknesses and attenuator length.

6) Tables No (7&8) show pressure drop and

sound creation in sound attenuator for

different velocities and frequencies.To non-increased sound level it is better

that the sound creation in sound attenator

would be equal or less than the remained

sound.Pressure drops in tabeles No (7&8) are

based on 40 inch sound attenuator length,

to correct it in other lengths see table

No (9).

7) Tables No (10-13) show sound atten-

uator area in square inches.

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Page 8: Sound Attenuators

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Residences (suburbia)

Residences (urban)

Music Auditoriums

Radio and Tv Broadcasting

Theatres

Assembly Hall

Mosques, churches

Libraries and Schools

Laboratories

Recreation Halls

Public Libraries, Museums

Banks, Post Offices

Restaurants Night Clubs

Cafeterias

Dept. Stores (upper floors)

Clothing Stores

Dept. Stores (main floors)

Supermarket, Retail stores

Sports Coliseums

Bowling Alley

Swimming pools

Factories, Supt. offices

Light Manufacturing

Heavy Manufacturing

Offices Conference Rooms

Offices Executive

Office Private

Office General

Office Computer

Hospital Rooms

Hospital Operating Rooms, Wards

Hospital Public Spaces

Apartment, Buildings, Hotel Rooms

Hotels, Ballrooms, Bank Halls

Hotel Public Spaces

Kitchens, Laundries, Garages

APPLICATION

20

25

20

20

25

30

20

30

35

35

30

35

35

40

35

35

40

40

30

35

40

40

45

55

25

30

30

35

40

25

30

35

30

30

35

40

25

30

22

22

27

32

25

35

40

40

35

40

40

40

45

45

35

40

50

45

60

65

30

35

40

35

35

40

45

30

35

25

25

30

35

30

40

45

50

40

45

45

45

50

50

40

45

55

50

70

75

35

40

45

40

40

45

50

30

35

35

40

50

35

40

45

50

60

40

45

45

50

MINIMUM

IT��4

AVERAGE

.��0�

MAXIMUM

�[���4

Table No: 1 - Noise criteria (NC)

Page 9: Sound Attenuators

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70

65

60

55

50

45

40

35

30

25

20

15

63 125 250 500 1000 2000 4000 8000

80

83

77

74

71

67

64

60

57

54

51

47

79

75

71

67

64

60

57

53

48

45

40

36

75

71

67

63

59

54

51

46

41

38

33

29

72

68

63

58

54

49

45

40

35

31

26

22

71

66

61

56

51

46

41

36

31

27

22

17

70

64

59

54

49

44

39

34

29

24

19

14

69

63

58

53

48

43

38

33

28

22

17

12

68

62

57

52

47

42

37

32

27

21

16

11

OCTAVE BAND CENTER FREQUENCY (HZ)NC

LEVEL

Table No: 2 - Noise criteria (db)

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Page 10: Sound Attenuators

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ENGINEERING PERFORMANCE DATA NF0+�����������-���U����B�������I�FQ&���Q��v!#��K���-���

Table No: 3 - Sound absorption (db) - (s=2" & d=4")

10 26 34 45 75 89 84 48

9 22 29 38 63 81 73 40

8 18 24 31 52 71 62 32

7 14 19 24 40 60 47 25

5 10 12 17 28 42 35 18

63 125 250 500 1000 2000 4000 8000

Sound attenuatorLength (inch)

OCTAVE BAND CENTER FREQUENCY (HZ)

72

60

48

36

24

Table No: 4 - Sound absorption (db) - (s=4" & d=4")

7 15 20 27 44 53 49 28

6 13 17 23 38 48 42 24

5 11 14 18 30 42 36 19

4 8 11 14 24 35 28 15

3 6 7 10 17 25 21 11

63 125 250 500 1000 2000 4000 8000

OCTAVE BAND CENTER FREQUENCY (HZ)

24

72

60

48

36

Sound attenuatorLength (inch)

Table No: 5 - Sound absorption (db) - (s=4" & d=8")

12 27 28 38 60 79 65 38

11 23 24 34 51 65 54 34

10 20 21 24 42 56 42 28

7 15 15 21 32 41 34 20

5 11 11 15 22 29 22 15

63 125 250 500 1000 2000 4000 8000

OCTAVE BAND CENTER FREQUENCY (HZ)

24

72

60

48

36

Sound attenuatorLength (inch)

Table No: 6 - Sound absorption (db) - (s=8" & d=8")

8 16 17 23 35 47 38 22

7 14 14 20 29 39 31 20

6 12 13 17 24 32 24 16

4 9 9 13 19 23 20 12

3 7 7 9 13 17 13 9

63 125 250 500 1000 2000 4000 8000

OCTAVE BAND CENTER FREQUENCY (HZ)

24

72

60

48

36

Sound attenuatorLength (inch)

Page 11: Sound Attenuators

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63

400

500

600

700

800

900

1000

1100

1200

125 250 500 1000 2000 4000 8000

43

50

55

57

59

61

62

64

65

0.10

0.12

0.14

0.16

0.18

0.20

0.22

0.24

0.26

0.20

0.25

0.30

0.35

0.40

0.45

0.50

0.55

0.60

37

44

48

51

54

56

58

61

63

32

37

41

45

49

52

54

57

60

28

35

39

43

46

50

53

56

58

25

32

38

41

44

48

51

54

56

15

22

29

34

38

42

46

49

52

5

13

20

25

29

33

37

40

43

0

5

10

15

20

24

27

31

34

OCTAVE BAND CENTER FREQUENCY (HZ)FaceVelocity

f.p.m.

Press.dropin.w.g.

s=2"d=4"

s=4"d=8"

Table No: 7 - Sound creation (db) & pressure drop (in.w.g.)(s=2" & d=4" - )s=4" & d=8"

63

600

700

800

900

1000

1100

1200

1300

1400

125 250 500 1000 2000 4000 8000

38

41

44

46

48

50

52

54

55

0.14

0.16

0.18

0.20

0.22

0.24

0.26

0.28

0.30

0.30

0.35

0.40

0.45

0.50

0.55

0.60

0.65

0.70

34

37

40

42

44

47

49

51

53

29

33

36

38

40

43

46

48

49

25

29

32

35

38

41

44

46

48

21

25

28

32

36

39

42

44

46

12

16

20

25

30

33

36

38

40

4

8

12

16

20

23

26

29

31

0

2

4

7

9

12

16

19

22

OCTAVE BAND CENTER FREQUENCY (HZ)FaceVelocity

f.p.m.

Press.dropin.w.g.

s=4"d=4"

s=8"d=8"

Table No: 8 - Sound creation (db) & pressure drop (in.w.g.)(s=4" & d=4" - )s=8" & d=8"

Sound attenuator length (inch)

Multiply by

40

1.00

30

0.95

20

0.90

50

1.07

60

1.13

70

1.20

80

1.25

100

1.40

120

1.60

Table No: 9 - pressure drop correction factor

Page 12: Sound Attenuators

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Table No: 10 - Sound attenuator area (sq.in) - (s=2" & d=4")

72

60

48

36

24

4752 5184

3600 3960 4320

1728 2016 2304 2592 2880 3168 3456

1080864 1296 1512 1728 1944 2160 2376 2592

720576432 864 1008 1152 1296 1440 1584 1728

360288216144 432 504 576 648 720 792 86412

72Width (inch)

Height (inch)

66605448423630241812

Table No: 11 - Sound attenuator area (sq.in) - (s=4" & d=4")

72

60

48

36

24

2304 2688 3072 3456

4320

4608

38403360

5184

1440

1920

1152 1728 2016 2304 2592

960768576

864

1152 1344 1536 1728

480384288192

384

576 672 768 86412

7264564840322416

Width (inch)

Height (inch)

Table No: 12 - Sound attenuator area (sq.in) - (s=4" & d=8")

72

60

48

36

24

3456 4032 4608 5184

6480

691260485184

43203600 57605040

7776

2160

2880

1728

2304

2592 3024 3456 3888

14401152864

1296

1728

1728 2016 2304 2592

720576432288

576

864

864 1008 1152 129612

10896847260483624Width (inch)

Height (inch)

Table No: 13 - Sound attenuator area (sq.in) - (s=8" & d=8")

72

60

48

36

24

4608 5568

83526912

57604800

5760

6960

2880

3840

2304

3072

3840

3456 4176

192015361152

1728

2304

2304 2784

960768576384

768

1152

1152 139212

1169680644832Width (inch)

Height (inch)

Page 13: Sound Attenuators

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k

k

k kCFM=A x V

The area of grille utilized by the air stream at

the point of the outlet velocity, V (See

outlet velocity) as measured with an

appropriate meter.CFM=A x V

The point of measurement and type of

meter must be defined to accurately

determine CFM.

k

k

k k

Outlet Area (A ):

TERMINOLOGY

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x�M�&�0����AB ( )P

e�+A��yi4�M%������!���(�W�%���U4����� #[���AB

3���F�����������=+��3�����4��5�;>��9�D-����% -�������

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x��0?����AB (P )

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v

The compressive pressure in inches of H O

that exists in the grille collar area at a given

air volume with or without specific

designated accessories.

2

sStatic Pressure (P ):

The pressure in inches of H O equated to a

velocity that exists for a given air volume in

the grille collar area.

V

2

Velocity Pressure (P ):

x�I��AB (P )

!� ��0?�������A�B�- M��&�0����AB�"�`i�(P ) (P )

2�������-�!_%���3���F����e+A������yi4�M%����

T

SVThe sum of the static pressure (P ) and the

velocity pressure (P ) that exists in the grille

collar for a given air volume.

T

S

V

Total Pressure (P ):

x���j� #U�

2�������!_%��!1#��"�'&��!��f�?� #U�

Aspect Ratio:

The ratio of width to height of the grille core.

Page 14: Sound Attenuators

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x����<�T�C$� (L )

x�����AB�C$� (L )

.%�����M%� K&�!�_%��M%�.��&�3�����9��&�I�����

3�P0���M%����3�����r���]�&���%�*%��>(�]�&���������AB

���3>�������-�1���YhYYYO���#���������C$�����3>����

2�����

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2��������3>����

-��0�����������7�����B�*������D-���������4����z���

2�������]�&��z�=+��M�0���(�3��������%��Q� !$����

2�����<�-�HY��-���HY���8����0U%���{�����#�

W

P

W

P

The total sound created by a grille under a

specific condition of opreation not including

specific room acoustic absorption value

reductions per frequency octave bounds.

The basis of rating must be stated re

10 watts, or 10 watts.

The sound pressure measured in the test

room or occupied room with a sound level

meter referenced to 0.0002 microbar.Sound pressure may be measured in octove

bands with an octave band analyzer or total

sound pressure in all octave bands can be

measured.

Sound Power Level (L ):

Sound Pressure Level (L ):

-12 -13

|HO|HS

A grille sound rating in pressure level at a

given condition of operation , based on

established criteria and a specific room

acoustic absorption value. Catalog NC

ratings are based on sound power level (LW)

minus an 18db room attenuation all octave

bands.

Noise Criteria (NC) : x�����D�E�� (NC)

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��Q��-��������T�D�E�����!��!����������=+A��������4

2����P0U��]�&��z�=+��M�0���� ���

Hg����� ����<�T�C$��!������D�E���{����%��Q�(LW)

2�����P0U��-�0����������;�`&���]�&��� *����I����D(

The measured velocity at a stated point with

a specified meter. The rated outlet velocity is

typically an average of several prescribed

velocity measurements.CFM =A x V (see outletArea)

K

k k

Outlet Velocity (V ): x���-��� ?�� (V )

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G����!��������-���p$Q��C$��!�Jk k

k

CFM = A x V

Page 15: Sound Attenuators

AHMAD SHAHROKHI was born in 1932 and began working in Sholeh Khavar Company in 1950. At that time, Iranian Industry was very young and most of the industrial parts and equipment were imported from foreign countries and Sholeh Khavar Company, active in the field of installation industry, was of no exception to this rule, thus it imported the air adjustable grilles required for its projects from USA supplied by T&B American Company.In 1951, a cargo ordered by Sholeh Khavar was sent by T&B Company for the said Company transported by vessel. this vessel broke down in a fire accident while in its way and therefore caused the Company to encunter problems in meeting its obligations. Thereupon, Ahmad Shahrokhi , assisted by financial support of the Company`s authorities, began sampling and manufacturing grilles from foreign models and was able to put into operation the production line of air adjustable grilles within a period of six months.Since then, being half a century, this Company has improved its quality and quantity day by and is proud to announce that on its 50 anniversary of its establishment, has proceeded in publishing the most comprehensive technical catalogue of its various products together with a CD of the computations.

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Page 16: Sound Attenuators