sound attenuators
DESCRIPTION
Sound Attenuators Of Shahrokhi MFG CoTRANSCRIPT
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SOUND ATTENUATORS
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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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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
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S S/2
1 1
6" 6"
1 /2" x 1 /2"
H
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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"
1"
3mm
DUCT
SOUND
ABSORBING
PERFORATED
SHEET
GALV. FRAME
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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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: 44
: 48
: 88
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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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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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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
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MAXIMUM
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Table No: 1 - Noise criteria (NC)
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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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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)
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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
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������ ����� �����SHAHROKHI MANUFACTURING CO.SHAHROKHI HY
ENGINEERING PERFORMANCE DATA NF0+�����������p$Q��C$��!#��K���-���
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)
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��B�<�4w$��
x��-���p$Q��C$� (A )
��������!%@��#?� ���!����������!_%��M%� 4�U�
!��������-���� ?���!�J ��-���� ?���!���!$Q�V
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2���������T�3��'0��
!#��K�CFM �0U%������3>�����3�K��-����3>�����!$Q�
2�%�`��e+A����Z�T��3��
k
k
k kCFM=A x V
The area of grille utilized by the air stream at
the point of the outlet velocity, V (See
outlet velocity) as measured with an
appropriate meter.CFM=A x V
The point of measurement and type of
meter must be defined to accurately
determine CFM.
k
k
k k
Outlet Area (A ):
TERMINOLOGY
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x�M�&�0����AB ( )P
e�+A��yi4�M%������!���(�W�%���U4����� #[���AB
3���F�����������=+��3�����4��5�;>��9�D-����% -�������
2�������-�!_%�
S
x��0?����AB (P )
yi4�M�%�����!���(�W�%���U4������0?����������AB
2�������-�!_%��M% �����e+A�3���F���
v
The compressive pressure in inches of H O
that exists in the grille collar area at a given
air volume with or without specific
designated accessories.
2
sStatic Pressure (P ):
The pressure in inches of H O equated to a
velocity that exists for a given air volume in
the grille collar area.
V
2
Velocity Pressure (P ):
x�I��AB (P )
!� ��0?�������A�B�- M��&�0����AB�"�`i�(P ) (P )
2�������-�!_%���3���F����e+A������yi4�M%����
T
SVThe sum of the static pressure (P ) and the
velocity pressure (P ) that exists in the grille
collar for a given air volume.
T
S
V
Total Pressure (P ):
x���j� #U�
2�������!_%��!1#��"�'&��!��f�?� #U�
Aspect Ratio:
The ratio of width to height of the grille core.
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������ ����� �����SHAHROKHI MANUFACTURING CO.SHAHROKHI HO
x����<�T�C$� (L )
x�����AB�C$� (L )
.%�����M%� K&�!�_%��M%�.��&�3�����9��&�I�����
3�P0���M%����3�����r���]�&���%�*%��>(�]�&���������AB
���3>�������-�1���YhYYYO���#���������C$�����3>����
2�����
3�����E�9��(�M%����-��0������������ ���81`�������AB
-���0�����������;�`&���I��������AB��%�-���0����������
2��������3>����
-��0�����������7�����B�*������D-���������4����z���
2�������]�&��z�=+��M�0���(�3��������%��Q� !$����
2�����<�-�HY��-���HY���8����0U%���{�����#�
W
P
W
P
The total sound created by a grille under a
specific condition of opreation not including
specific room acoustic absorption value
reductions per frequency octave bounds.
The basis of rating must be stated re
10 watts, or 10 watts.
The sound pressure measured in the test
room or occupied room with a sound level
meter referenced to 0.0002 microbar.Sound pressure may be measured in octove
bands with an octave band analyzer or total
sound pressure in all octave bands can be
measured.
Sound Power Level (L ):
Sound Pressure Level (L ):
-12 -13
|HO|HS
A grille sound rating in pressure level at a
given condition of operation , based on
established criteria and a specific room
acoustic absorption value. Catalog NC
ratings are based on sound power level (LW)
minus an 18db room attenuation all octave
bands.
Noise Criteria (NC) : x�����D�E�� (NC)
��.%����M%� K&��AB�C$���U4����!_%������{��
��Q��-��������T�D�E�����!��!����������=+A��������4
2����P0U��]�&��z�=+��M�0���� ���
Hg����� ����<�T�C$��!������D�E���{����%��Q�(LW)
2�����P0U��-�0����������;�`&���]�&��� *����I����D(
The measured velocity at a stated point with
a specified meter. The rated outlet velocity is
typically an average of several prescribed
velocity measurements.CFM =A x V (see outletArea)
K
k k
Outlet Velocity (V ): x���-��� ?�� (V )
M%�.���& !$Q���M%����3������3>������ ?��8���
2�������z�=+� 3�P�0��
�����&�.�-��0���)�-���0��<�=������-���� ?���{����
2�������3������3>������8��� ?��
G����!��������-���p$Q��C$��!�Jk k
k
CFM = A x V
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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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