Acoustic Guide
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G U I D E
ACOUSTIC Insulation Design Guide
A C O U S T I C
D E S I G N
A C O U S T I C
D E S I G N
Introduction.
Contents.
The Bradford Insulation Group forms part of the Building Materials Division of CSR Limited. CSR Bradford Insulation manufactures and markets an extensive range of insulation products offering outstanding thermal, acoustic and fire protection properties for use in all types of domestic and commercial buildings. Two mineral fibre insulation types are available; ‘Bradford Glasswool’, which is manufactured by controlled felting of biosoluble glass wool bonded with a thermosetting resin; and ‘Bradford Fibertex™ Rockwool’ which is spun from natural rock and bonded with a thermosetting resin. Both are available in sheet or roll form and as moulded pipe insulation. Bradford Thermofoil™ and Thermotuff™ are a range of aluminium foil laminates available in various grades. All CSR Bradford Insulation products are tested to meet stringent quality control standards incorporating quality management systems such as AS3902/ISO9002.
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Introduction Product Range, Applications & Selection Guides
3 – 13
Bradford Acoustic Solutions Party & Interior Walls Residential & Commercial External Walls Roof/Ceiling Systems Floor/Ceiling Systems Floors Plumbing Gutters & Downpipes Pipes, Tanks & Vessels Factories & Workshops Acoustic Baffles Acoustic Enclosures Vibration Damping Air Conditioning Systems
14 18 18 23 24 25 26 27 27 29 30 34 36
ABOUT THIS GUIDE. The purpose of this guide is to provide information on the technical benefits obtained with the inclusion of acoustic insulation materials in the construction of all types of buildings as well as noise control of machinery. The range of Bradford products and their applications is presented along with data and worked examples to illustrate design considerations. This Acoustic Design Guide also outlines the basic properties of sound, and methods for its control. It does not set out to provide a definitive solution to every conceivable noise problem. Rather, it aims to explain the principles involved, so that these principles can be applied along with common sense, to overcome common acoustic problems. Acoustics is however a complex science, and there will be many instances where the services of specialist acoustic consultants or noise control engineers are indispensable. The reader is cautioned against investing large sums of money in noise control without first seeking advice. This is particularly pertinent where compliance with noise abatement orders is concerned.
Bradford Acoustic Solutions for Specialty Applications Home Cinema Auditoriums Sports Complexes Canteens/Restaurants Karaoke/Night Clubs Shopping Centres Recording Studios Heavy Plant OEM Application Appendix A
The Nature of Sound Sound Transmission Flanking Paths Sound Absorption Reverberation Room Acoustics Industrial Acoustics Speech Privacy
46 47 48 50 50 51 52 53 53 54 57 59 59 61 64 67 68
Appendix B
Floor/Ceiling Systems
Appendix C
Product Data Sound Absorption Coefficients Static Insertion Loss/Silencers Air Flow Resistivity
71 74 77 78
Appendix D
Terminology
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CSR Bradford Insulation Regional Contact Details
G U I D E
TECHNICAL ASSISTANCE. To assist designers, a free and comprehensive technical service, as well as advice and assistance in specifying and using Bradford products is available from CSR Bradford Insulation offices in your region. Further technical data and product updates are also available on the CSR Building Solutions Website: www.csr.com.au/bradford Information included in this Design Guide relates to products as manufactured at the date of publication. As the CSR Bradford Insulation policy is one of continual product improvement, technical details as published are subject to change without notice.
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The Importance of Acoustic Insulation. The minimisation of noise has become a significant environmental issue in the modern world, whether at home, at work or on holidays. CSR Bradford Insulation manufacturers and distributes an extensive range of insulation products that provide excellent noise control properties, as well as the traditional thermal and fire control benefits. Although all fibrous insulation products can provide some acoustic benefits, CSR Bradford Insulation has a range of products specifically designed and tested for the acoustic insulation market, including:–
ACOUSTIC INSULATION PRODUCT
APPLICATIONS
Bradford Glasswool Partition Batts
Economical insulation for internal wall sound absorption in housing, residential apartments or commercial offices. Various systems are available to meet building codes.
Bradford SoundScreen™
Unique rockwool insulation system to reduce room-toroom noise transmission in houses.
Bradford ACOUSTICON™
Commercial and residential metal roofing insulation specially developed to reduce rain noise.
Bradford Glasswool R1.5 ACOUSTITUFF™ Ductliner
Air conditioning duct internal lining product offering full enclosure with excellent sound absorption properties.
Bradford Glasswool R1.5 ULTRAPHON™ Ductliner
High performance acoustic absorption product for ducting, silencers and other acoustic applications.
Bradford ACOUSTICLAD™
Wall absorber combining the superior acoustic properties of Bradford Fibertex™ Rockwool with a perforated metal panel system.
Bradford Glasswool ACOUSTILAG™
Pipe insulation product combining the noise barrier properties of loaded vinyl and the absorption benefits of glasswool. Ideal for noisy plumbing.
Bradford FIBERTEX™ Acoustic Baffle
Rockwool batt enclosed in white polymer film used for which is designed to be hung from the overhead structure to provide acoustic absorption in a room or workplace.
Bradford Glasswool SUPERTEL™
General purpose medium density glasswool acoustic insulation.
Bradford Rockwool FIBERTEX™ 450
General purpose premium rockwool acoustic insulation product.
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Acoustic Insulation for Homes.
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Metal Roof Insulation or Tiled Roof Sarking
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Ceiling Insulation
3
Internal Wall Insulation
4
External Wall Insulation/ Party Wall
5
Plumbing Insulation
6
7
Acoustic Floor/Ceiling & Floating Floor Insulation
Home Cinema Wall, Floor & Ceiling Insulation. Acoustic Absorbing Panels
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Bradford Insulation Application & Selection Guide for Homes. Insulation Application
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3 4 5 6
Ceiling
Acoustic Internal Walls
External Walls
Plumbing
Acoustic Floor/Ceilings
Floating Floors
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Product Range/Facings
Bradford ACOUSTICON™ Blanket
Medium, Heavy Duty or Specialty THERMOFOIL™
Bradford Glasswool ANTICON™ Blanket
R1.5, R2.0, R2.5 Faced Light, Medium, Heavy Duty or Specialty THERMOFOIL™
Bradford FIBERTEX™ Rockwool ANTICON™ Blanket
R1.5, R2.0, R2.5 Faced Light, Medium, Heavy Duty or Specialty THERMOFOIL™
Bradford THERMOFOIL™ Sarking
Medium, Heavy Duty, ANTIGLARE
Bradford THERMOTUFF™ Sarking
Medium, Extra Heavy Duty, Safety
Bradford Glasswool Gold Ceiling Batts
R2.0, R2.5, R3.0, R3.5, R4.0
Bradford FIBERTEX™ Rockwool Ceiling Batts
R2.0, R2.5, R3.0
Metal Roofing
Tiled Roof Sarking
2
Product Type
Home Cinema
Bradford ACOUSTILAG™
2.5 - 5.0mm Loose Fill Bags
Bradford Glasswool Partition Batts
50, 75 and 100mm
Bradford Rockwool SoundScreen™
75mm
Bradford Glasswool Gold Wall Batts
R1.5, R2.0
Bradford FIBERTEX™ Rockwool Wall Batts
R1.5, R2.0
Bradford FIBERTEX™ Rockwool Cavity Wall Granulated
Loose Fill Bags
Bradford ACOUSTILAG™ Pipe Insulation
ACOUSTILAG™ 20, 23 and 26
Bradford HANDITUBE™ Pipe Insulation
Stocked by CSR Bradford Insulation
Bradford FIBERTEX™ Rockwool Ceiling Batts
R1.5 - R2.0
Bradford Glasswool Wall/Floor Batts
R1.5 - R2.0
Bradford FIBERTEX™ Rockwool Wall/Floor Batts
R1.5 - R2.0
Bradford Rockwool SoundScreen™
75mm
Bradford Glasswool QUIETEL™
Specialty installation system
Bradford Glasswool SUPERTEL™
Specialty facings available
Bradford FIBERTEX™ Rockwool
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Acoustic Insulation for Homes.
1 2
Tiled Roof Sarking or Metal Roof Insulation
Ceiling Insulation
3
Internal Wall Insulation
4
External Wall Insulation
5
Plumbing Insulation
6
7
Acoustic Floor/Ceiling & Floating Floor Insulation
Home Cinema Wall, Floor & Ceiling Insulation. Acoustic Absorbing Panels
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Bradford Insulation Application & Selection Guide for Homes. Insulation Application
1
3 4 5 6
Ceiling
Acoustic Internal Walls
External Walls
Plumbing
Acoustic Floor/Ceilings
Floating Floors
7
Product Range/Facings
Bradford ACOUSTICON™ Blanket
Medium, Heavy Duty or Specialty THERMOFOIL™
Bradford Glasswool ANTICON™ Blanket
R1.5, R2.0, R2.5 Faced Light, Medium, Heavy Duty or Specialty THERMOFOIL™
Bradford FIBERTEX™ Rockwool ANTICON™ Blanket
R1.5, R2.0, R2.5 Faced Light, Medium, Heavy Duty or Specialty THERMOFOIL™
Bradford THERMOFOIL™ Sarking
Medium, Heavy Duty, ANTIGLARE
Bradford THERMOTUFF™ Sarking
Medium, Extra Heavy Duty, Safety
Bradford Glasswool Gold Ceiling Batts
R2.0, R2.5, R3.0, R3.5, R4.0
Bradford FIBERTEX™ Rockwool Ceiling Batts
R2.0, R2.5, R3.0
Bradford ACOUSTILAG™
25mm – 50mm
Bradford Glasswool Partition Batts
50, 75 and 100mm
Bradford Rockwool SoundScreen™
75mm
Bradford Glasswool Gold Wall Batts
R1.5, R2.0
Bradford FIBERTEX™ Rockwool Wall Batts
R1.5, R2.0
Bradford FIBERTEX™ Rockwool Cavity Wall Granulated
Loose Fill Bags
Bradford ACOUSTILAG™ Pipe Insulation
ACOUSTILAG™ 20, 23 and 26
ARMAFLEX™ Pipe Insulation
Stocked by CSR Bradford Insulation
Bradford FIBERTEX™ Rockwool Ceiling Batts
R1.5 - R2.0
Bradford Glasswool Wall/Floor Batts
R1.5 - R2.0
Bradford FIBERTEX™ Rockwool Wall/Floor Batts
R1.5 - R2.0
Bradford Rockwool SoundScreen™
75mm
Bradford Glasswool QUIETEL™
Specialty installation system
Bradford Glasswool SUPERTEL™
Specialty facings available
Metal Roofing
Tiled Roof Sarking
2
Product Type
Home Cinema
Bradford FIBERTEX™ Rockwool
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Acoustic Insulation for Commercial Buildings
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Air Conditioning Duct Insulation (Rigid & Flexible Ducts)
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Fan Silencer & Fan Casing Insulation
1
Ceiling Insulation (Suspended Grid Ceilings & Concrete Roof/Soffit)
2
Internal Partition Wall Insulation
3
Acoustic Absorbing Panels
4
Plumbing Insulation
5
Plant Room Wall & Ceiling Insulation
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Bradford Insulation Application & Selection Guide for Commercial Buildings. Insulation Application
Product Type
Product Range/Facings
Bradford Glasswool ANTICON and ACOUSTICON™ Blanket
™
1
Concrete Roof/Soffit
Bradford FIBERTEX™ Rockwool ANTICON™ Blanket Bradford Glasswool SUPERTEL™ Bradford FIBERTEX™ 350 Rockwool
Exposed Grid Ceiling Concealed Grid Ceilings
2
Acoustic Internal Partitions
3
Acoustic Absorbing Panels
4
Plumbing Insulation
5
Plant Room Wall & Ceiling Insulation
6
Fan Casings
Fan Silencers
7
Rigid Ducting Internal Lining
Rigid Ducting External Wrap
Flexible Duct
Bradford Glasswool Ceiling Panel Overlays Bradford FIBERTEX™ Rockwool Ceiling Panel Overlays Bradford Glasswool Building Blanket Bradford FIBERTEX™ Rockwool Building Blanket Bradford Glasswool Partition Batts Bradford FIBERTEX™ Rockwool Partition Batts Bradford Glasswool ULTRATEL™ Board Bradford FIBERTEX™ 450 Rockwool Bradford ACOUSTILAG™ Pipe Insulation ARMAFLEX™ Pipe Insulation Bradford Rockwool/Glasswool ACOUSTICLAD™ Bradford Glasswool FLEXITEL™, SUPERTEL™, ULTRATEL™ Bradford FIBERTEX™ 350 Rockwool
R1.5, R2.0, R2.5 Faced Light, Medium, Heavy Duty or Specialty THERMOFOIL™ R1.5, R2.0 Faced Light, Medium, Heavy Duty or Specialty THERMOFOIL™ 25 – 75mm THERMOFOIL™ Facing 50 - 100mm THERMOFOIL™ Facing Factory Applied Acoustic Facings Factory Applied Acoustic Facings R1.2, R1.5, R1.8, R2.0, R2.5 50, 75mm, R1.5, R2.0 50, 75, 100mm 45, 70mm 25-100mm, Factory Applied Facings 25-100mm, Factory Applied Facings ACOUSTILAG™ 20, 23 and 26 Stocked by CSR Bradford Insulation Perforated 750P THERMOFOIL™ Perforated 750P THERMOFOIL™ Perforated 750P THERMOFOIL™ ACOUSTITUFF™ ULTRAPHON™ BMF, ULTRAPHON™ 25 – 100mm (Quietel 13mm - 50mm)
Bradford Glasswool FLEXITEL™ Bradford Glasswool SUPERTEL™ Bradford Glasswool QUIETEL™ Bradford FIBERTEX™ Rockwool DUCTLINER Bradford Glasswool SUPERTEL™ Bradford Glasswool ULTRATEL™ Bradford Glasswool QUIETEL™ Bradford FIBERTEX™ Rockwool DUCTLINER Bradford FIBERTEX™ 450 Rockwool Bradford Glasswool SUPERTEL™ Perforated 750P THERMOFOIL™ Bradford Glasswool DUCTLINER ULTRAPHON™, Bradford Glasswool ULTRATEL™ ACOUSTITUFF™ facings ™ Bradford FIBERTEX Rockwool DUCTLINER 25 – 100mm, R1.5 & R0.9 ™ Bradford Glasswool MULTITEL R1.5 & R0.9 Bradford Glasswool FLEXITEL™ 25 – 100mm ™ Bradford Glasswool THERMOGOLD DUCTWRAP Bradford FIBERTEX™ Rockwool DUCTWRAP Bradford Glasswool R1.0 SPECITEL™ R1.0. R1.5 Bradford FABRIFLEX™ Flexible Ducting Available ex-Singapore ™ Bradford ACOUSTIFLEX Flexible Ducting Available ex-Singapore
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Acoustic Insulation for Theatre, Sports & Multi-Purpose Buildings
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Auditorium/Theatre/Cinema • Roof/Ceiling Insulation • Wall Insulation • Acoustic Absorbing Panels
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Sports Centre • Roof/Ceiling Insulation • Floor Insulation • Acoustic Absorbing Panels
4
Air Conditioning System Insulation
3
Canteen • Wall Insulation • Ceiling Insulation • Acoustic Absorbing Panels • Metal Deck Rain Noise Insulation
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Bradford Insulation Application & Selection Guide for Theatre, Sports & Multi-Purpose Buildings. Insulation Application Walls
Product Type Bradford Glasswool Partition Batts Bradford Rockwool Partition Batts
Acoustic Absorbers
1
Bradford Glasswool FLEXITEL™, SUPERTEL™ ULTRATEL™ with BMF (Black Matt Facing Tissue), ULTRAPHON™ or other specialty facing. Bradford FIBERTEX™ Rockwool Bradford ACOUSTICLAD Wall/Ceiling Absorber
Theatre, Cinema & Auditorium
Roof/Ceiling Bradford Glasswool ACOUSTICON™ Bradford Glasswool Ceiling Batts Bradford Rockwool Ceiling Batts Acoustic Absorbers
2
Sports Buildings • Swimming • Basketball • Gymnasium
Bradford ACOUSTICLAD™ Wall/Ceiling Absorber Bradford FIBERTEX™ Rockwool Bradford Glasswool FLEXITEL™, SUPERTEL™ ULTRATEL™ with BMF (Black Matt Facing Tissue), ULTRAPHON™ or other specialty facing. Roof/Ceiling Bradford Glasswool ACOUSTICON™ Bradford Glasswool Ceiling Batts Bradford Rockwool Ceiling Batts Acoustic Absorbers
3
Canteen Facility
Bradford FIBERTEX™ Rockwool Bradford Glasswool FLEXITEL™, SUPERTEL™ ULTRATEL™ with BMF (Black Matt Facing Tissue), ULTRAPHON™ or other specialty facing. Bradford ACOUSTICLAD Wall/Ceiling Absorber Walls Bradford Glasswool Partition Batts Bradford Rockwool Partition Batts Roof/Ceiling
4
Air Conditioning Systems
Bradford Glasswool ACOUSTICON™ Bradford Glasswool Ceiling Batts Bradford Rockwool Ceiling Batts Refer to CSR Bradford Insulation Air Conditioning Design Guide and Product Guide.
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Acoustic Insulation for Industrial Applications.
2
Acoustic Enclosures for Plant & Machinery
1
Acoustic Baffles (suspended)
8
Acoustic Wall Absorbers
7
Metal Deck Roof Insulation
6
Ceiling Insulation
3
Bradford Insulation for OEM Applications
5
Acoustic Internal Wall Insulation
4
Acoustic Absorbing Screens
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Bradford Acoustic Insulation for Industrial Applications. Insulation Application
1 2
Acoustic Baffles
Product Type
Product Range/Facings
Bradford FIBERTEX™ Acoustic Baffle
Fully enclosed in white polymer film ready to hang.
Acoustic Enclosures for Plant & Machinery
Bradford FIBERTEX™ Rockwool
25 – 100mm
Bradford Glasswool FLEXITEL
Density 24 – 120kg/m3
™
Bradford Glasswool SUPERTEL™ Bradford Glasswool ULTRATEL™
3
OEM Applications
Bradford Glasswool Appliance Grade
Cut to size with specialty facings
Bradford Rockwool Appliance Grade
available
Bradford Glasswool QUIETEL
™
4
Acoustic Absorbing Screens
Bradford Glasswool SUPERTEL™
25 – 100mm
5
Acoustic Internal Walls
Bradford Glasswool Partition Batts
6
Ceilings
7
Metal Deck Roofs
Bradford Glasswool ACOUSTICON™
8
Acoustic Wall Absorbers
Bradford ACOUSTICLAD™
25 – 100mm
Bradford FIBERTEX™ Rockwool
Specialty facings available
Bradford FIBERTEX™ Rockwool To fit studs
Bradford FIBERTEX Rockwool Partition Batts ™
Bradford Glasswool Ceiling Batts
50 – 150mm
Bradford Rockwool Ceiling Batts 75mm
Bradford Rockwool ACOUSTICON
™
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Bradford Acoustic Solutions. Interior Walls.
The addition of denser wall sheeting products such as CSR Gyprock® Fyrchek™ or Soundchek™ plasterboard or CSR Fibre Cement together with Gyprock’ Resilient Mounts and furring channels can reduce noise levels.
RESIDENTIAL PARTY & INTERNAL WALLS. The Building Code of Australia (BCA) Sections F5 sets out Sound Transmission Class (STC) requirements for sound insulation of floors, walls, between units, walls between bathrooms, laundries, kitchens, between habitable and non-habitable rooms in multi-tenancy buildings. In late 1999, the BCA changed its acoustic rating from STC to Sound Reduction Index (Rw). This Acoustic Design Guide uses the STC rating units as Australasia and Asia are familiar with STC and it is very similar to Rw. An increase of either one STC unit or one Rw unit approximately equals a reduction of one decibel in noise level. Table 1 below shows common STC values of walls used in buildings. The expected audibility for a given STC level is also shown, based on guidelines for ambient sound levels
DOUBLE-LEAF WALLS. Higher transmission losses than those expected by the Mass Law can be obtained by using double-leaf walls with an air cavity. Further increases in sound transmission loss, particularly at low frequencies can be achieved by using wider air cavities. When a double leaf wall is uninsulated, the air in the cavity can act as a spring, efficiently transmitting sound energy from one side of the wall to the other. Significant improvement in STC is obtained by using Bradford Rockwool or Glasswool batts in the cavity. Acoustic tests of walls around the world have shown the use of glasswool batts or rockwool batts inside cavity walls reduces resonances between the two sheets and can significantly improve the acoustic performance by up to 10 STC. Generally the thicker and/or denser the insulation in the cavity, the higher the STC rating resulting in less noise transmitted to the other side of the wall. The actual improvement in STC depends on the type of wall construction. Insulation in the cavity will also lessen the effect of the ‘coincidence dip’ in double leaf walls.
TABLE 1. STC AND AUDIBILITY THROUGH WALLS AND FLOORS. STC Value
Audibility
30 - 35
Speech audible
40
Loud speech, still heard
45
Loud speech, just heard
50 – 55
Speech cannot be heard
The BCA Part F5.4 Sound Insulation Of Walls Between Units currently states a wall must have an STC not less than 45. It has been proposed to increase this to STC 55 in the future as STC 45 does not provide enough acoustic privacy. STC’s ≥50 are standard in Europe and USA.
FLANKING NOISE. It should be noted that actual installations, as compared to acoustic laboratories, exhibit flanking noise through doors, windows, ventilation ducting, air gaps at ceiling, wall and floor intersections. In addition, poor workmanship may degrade the acoustic performance of partitions. For these reasons, a building element constructed in the field will usually achieve a lower STC ratings than when tested in the laboratory. Maximum acoustic performance can be achieved by eliminating penetrations in walls, caulking gaps, and staggering electrical outlet or other necessary penetrations through the wall. Wall cavities should be completely filled with insulation and tightly fitted around pipes, conduits and other outlets.
Generally internal walls for residential applications in Australia use either rendered brick or lightweight double leaf walls using plasterboard and/or fibre cement construction on timber studs. To improve or increase the sound transmission loss (STL) hence the STC of these walls, the following is required:-
EXTRA MASS. Sound Transmission Loss (STL) depends heavily on the surface density of a building element (mass per square metre of surface). For every doubling of surface density, the sound transmission loss increases by about 5dB.
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STC data for some typical partition walls is given in Table 2. Further STC data for internal cavity walls is available the CSR Bradford brochure ‘Noise Reductions For Internal Partitions or the CSR Gyprock Fire & Acoustic Design Guide, ‘The Red Book’.
LOW FREQUENCY NOISE. Low frequency noise from sources such as fans, aircraft, road and rail traffic, and bass from amplified music can penetrate walls easier than high frequency noise. Therefore higher sound transmission loss (ie. higher STC) walls are required to ensure satisfactory acoustic performance. As a general rule, add at least 5 STC points to the acoustic requirement of the walls when low frequency noise is present.
TABLE 2. STC DATA FOR TYPICAL TIMBER FRAME PARTITION SYSTEMS.
Description
STC (Rw) No Insulation 33
STC 30 - 42 • 1 layer 10mm CSR Gyprock Plasterboard CD™ • 70/75mm Timber Studs • 1 layer 10mm CSR Gyprock Plasterboard CD™
STC (Rw) Bradford Glasswool Wall Batts
STC (Rw) Bradford Rockwool Wall Batts
38 (75mm Batts)
39 (45mm Batts) Test CSR 37/67
42 SoundScreen™
STC 40 - 50 • 2 layers 13mm CSR Gyprock Fyrchek™ plasterboard • 70/75mm Timber Studs • 1 layer 13mm CSR Gyprock Fyrchek™ plasterboard STC 50 - 60 • 2 layers 16mm CSR Gyprock Fyrchek™ plasterboard • 90 x 35mm Staggered Timber Studs • 2 layers 16mm CSR Gyprock Fyrchek™ plasterboard
43
47 (50mm Batts)
48 (45mm Batts)
51
58 (50mm Batts)
59 (45mm Batts)
* Refer to the CSR Bradford Noise Reduction of Internal Partitions brochure or the CSR Gyprock® Fire & Acoustic Design Guide (‘The Red Book’) which show a wide range of internal partitions and their STC ratings.
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COMMERCIAL INTERNAL PARTITIONS. Internal plasterboard or fibre cement walls using steel stud systems are widely used in commercial construction and offer a wide range of sound transmission loss performance.
Thinner gauge steel studs, with greater stud spacing and minimum fixing of sheets to studs also results in a wall which is able to flex more easily generally resulting in slightly higher acoustic performance.
The methods stated previously for improving acoustic performance of Residential Internal Walls also apply to the Commercial Internal Partitions.
If higher STC performance is required, there are a number of steps that can be incorporated at the time of construction to improve acoustic performance, as detailed in Table 3.
TABLE 3. INSULATION FOR NOISE REVERBERATION CONTROL. Addition
STC Improvement
Comments
Fit insulation into studs
Up to 10 STC points
Thicker and/or denser insulation such as Rockwool is beneficial. Light gauge or deeper steel studs give higher STC performance.
Use Gyprock® Fyrchek plasterboard
Up to 3 STC points if installed both sides
Use of 13mm or 16mm CSR Gyprock® Fyrchek™ improves performance due to extra mass.
Gyprock® Resilient Channel one side
6 – 8 STC points
Resilient Channel isolate the Gyprock® Plasterboard from the stud.
Bradford Quietel one side and insulation to stud
4 STC points
Quietel board acts as a sound isolator between the Gyprock® Plasterboard and the Stud.
Staggered and double studs
Up to 10 STC points
Provide sound breaks between solid studs and Gyprock®. Recommended where impact isolation is also required.
Gyprock® Resilient Mounts and Furring Channel
Up to 10 STC points
Used where high level reduction of airborne and impact noise is required.
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TABLE 4. STC RATINGS OF SOME COMMERCIAL INTERNAL PARTITIONS*. A sample of the STC ratings for commercial internal partitions using steel studs taken from the Tables in the CSR Bradford Insulation ‘Noise Reductions for Internal Partitions’ brochure, together with results from recent testing.
Description
STC (Rw) No Insulation
STC 30 - 40 • 1 layer 13mm Gyprock Plasterboard CD™ • 64mm Steel Studs • 1 layer 13mm Gyprock Plasterboard CD™
35
STC (Rw) Bradford Glasswool Partition Batts
STC (Rw) Bradford Rockwool Partition Batts
40 (50mm Batts)
41 (45mm Batts)
Test HAS 085
STC 40 - 50 • 1 layer 16mm Gyprock Fyrchek™ • 64mm Steel Studs • 1 layer 16mm Gyprock Fyrchek™ STC 50 - 60 • 1 layer 13mm Gyprock Fyrchek™ plasterboard • 64 x 0.75mm BMT Separated Steel Studs • 1 layer 13mm Gyprock Fyrchek™ plasterboard STC 55 - 60 • 1 layer 16mm Gyprock Fyrchek™ plasterboard • 64 x 0.75 BMT Separated Steel Studs • 1 layer 16mm Gyprock Fyrchek™ plasterboard STC 60 - 70 • 2 layers 16mm Gyprock Fyrchek™ plasterboard • 92 x 0.75mm BMT Separated Steel Studs • 2 layers 16mm Gyprock Fyrchek™ plasterboard
39
44 (50mm Batts)
45 (45mm Batts)
45
57 (75mm Wall Batts)
58 (75mm SoundScreen™)
45
55 (80mm Batts)
60 (75mm SoundScreen™)
55
63 (75mm Batts)
64 (70mm Batts)
* Refer to the CSR Bradford Insulation Noise Reduction of Internal Partitions brochure or CSR Gyprock® Fire & Acoustic Design Guide (‘The Red Book’) which show a wide range of internal partitions and their STC ratings.
ACOUSTIC PREDICTION SYSTEM. loss STC greater than 50, such as those used between recording studios or cinemas, flanking paths should be considered, as they can derate the acoustic performance of the partition. For cinema walls requiring a very high STC rating, contact CSR Bradford Insulation regarding the CSR Gyprock® Cinema Wall System, or other CSR systems.
CSR Bradford Insulation has available a sophisticated ‘Acoustic Predictor’ computer program, developed by CSR Gyprock®, which can predict the STC rating of many different internal partitions, in addition to those shown above and in the brochure. Note: For walls which require high sound transmission 17
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External Walls.
G U I D E
To improve STC performance of single timber studs, consider the use of Rondo resilient channels or CSR Gyprock® resilient mounts with furring channels, which can improve STC (or Rw) by 6 to 8.
External walls of residential buildings usually consist of • brick veneer construction, or lightweight concrete construction,
Buildings with double brick walls should use vibration isolated wall ties to reduce the amount of noise and vibration transmitted from one wall to the other.
• a cladding material, usually timber or fibre cement or • occasionally double brick.
Note that building elements of low acoustic performance will derate the improvements made to other building elements ie. walls and ceilings. For example, lightweight windows and doors can reduce the overall STC rating of the wall.
For better acoustic performance, use building materials with more mass. Clay bricks provide high surface density (or mass per square metre) to enable high transmission loss. The use of CSR Gyprock® Soundchek™ or Fyrchek™ plasterboard is recommended for interior walls. For even higher wall STC, the use of CSR Gyprock® Resilient Mounts and Furring Channels is recommended.
Products. Bradford Glasswool Wall Batts Bradford Rockwool Wall and Ceiling Batts
For brick veneer walls add the thickest possible rockwool or glasswool batts inside wall cavities during construction of the building.
Roof/Ceiling Systems. Roof/ceiling systems generally consist of either steel roofing or tile roofing. These roofing systems usually provide average to poor acoustic performance and can be an acoustically weak link in a building facade. It should be noted that consideration should be given to other weak links in the building extensions such as windows and doors.
Granulated rockwool can be retro-fitted into existing walls of a building using a special machine which blows granulated rockwool under pressure into the wall cavities. Wall sheeting usually has solid connections (ie screw or nail fixed) to the timber or steel studs and transmits noise through these solid connections. CSR Gyprock® Resilient Mounts can reduce both noise and vibration transmission.
Low frequency noise generated by aircraft, road and rail traffic can easily penetrate commonly used building materials including the roofing.
FIG 1. EXTERNAL WALL INSULATION.
Tile roofs are generally used in domestic applications. It is recommended that Bradford Rockwool or Glasswool Ceiling Batts be used in the roof cavity to improve both acoustic and thermal resistance. Note the higher the thermal resistance or R-value, the thicker the batt, and the better the acoustic absorption. The following points indicate methods to improve the acoustic performance of a typical tiled roof system. Tips on how to further improve the STC rating are provided in (brackets)
Bradford Thermofoil or Thermotuff Breather
• Rockwool or glasswool insulation batts on top of the ceiling, (the thicker the insulation or the higher the R-rating, the better the acoustic absorption)
Timber Frame
• Using a heavy THERMOFOIL ™ sarking as a condensation barrier under the roof tiles, the heavier the better the noise reduction.
Bradford Insulation Wall Batts External Cladding
• Adding Bradford SOUNDLAGG™ loaded vinyl over the ceiling joists, (the heavier the better). • Thicker and/or heavier plasterboard for the ceiling, (use fire rated plasterboard and multiple layers). Care should be taken to minimise all gaps in the roof ceiling to maximise the acoustic performance.
Gyprock® Plasterboard
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TILED ROOF SYSTEMS. rockwool or glasswool insulation will maximise noise absorption in the roof space, minimising the amount of noise entering the room/s below.
Figure 2 shows how to improve the acoustic performance of a typical tiled roof system. Note that the gaps inherent in tile roof construction allow noise to enter the roof cavity. Hence the use of
FIG 2. IMPROVING ACOUSTIC PERFORMANCE OF TILED ROOF SYSTEMS. Bradford Thermofoil 733 Sarking over rafters Monier Concrete Roof Tiles
STC/Rw
SYSTEM Monier concrete tile roof with one layer of Gyprock Supa-Ceil™ plasterboard fixed to ceiling joists spaced at 600mm centres.
33
Add Bradford R2.5 Glasswool Batts between joists.
41
Replace Bradford R2.5 Glasswool Batts with Bradford R3.0 FIBERTEX™ Rockwool Building Batts between joists, and install Bradford THERMOFOIL™ 733 over rafters.
45
Add Bradford SOUNDLAGG™ (6kg/m2) over ceiling joists.
50
Bradford Soundlagg (6kg/m2) over joists
Ceiling Joist Gyprock 10mm Supa-Ceil Plasterboard Ceiling
Bradford Glasswool or Rockwool Ceiling Batts (as indicated)
STEEL ROOFING SYSTEMS. installed directly underneath the metal decking to guard against condensation.
Steel roofing is used in both commercial and residential roofing systems in Australia, New Zealand and Asia.
Figure 3 shows the improvement in STC of a typical domestic roof with the addition of Bradford insulation in the roof/ceiling system.
Metal deck roofing systems require a layer of thermal insulation faced with a suitable vapour barrier to be
FIG 3. IMPROVING ACOUSTIC PERFORMANCE OF STEEL ROOF SYSTEMS.
SYSTEM
STC/Rw Metal Roofing
Metal roofing with 1 x 10mm Gyprock Supa-Ceil™ plasterboard fixed to ceiling joists spaced at 600mm centres.
34
Add Bradford ACOUSTICON™ foil faced building blanket over rafters under metal roofing.
41
Add Bradford R2.5 FIBERTEX™ Rockwool Building Batts between joists.
45
Replace Supa-Ceil plasterboard with 2 layers x 13mm Gyprock Plasterboard CD fixed to metal furring channels (at 600mm max. cts) attached by Gyprock Resilient Mounts
52
Metal roofing with one layer plasterboard fixed to ceiling joists spaced at 600mm cts. plus Bradford Ceiling Insulation between joist. (New Zealand only).
Bradford Acousticon Foil Faced Blanket
Ceiling Joist Gyprock 10mm Supa-Ceil Plasterboard Ceiling
39 – 41
19
Bradford Fibertex Rockwool Batts or (Bradford G lasswool Ceiling Insulation in New Zealand)
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Bradford ACOUSTICON ™ Glasswool Roofing Blanket is faced with THERMOFOIL ™ . ACOUSTICON ™ has been specially developed to provide cost effective rain noise reduction of 18dB(A) insertion loss under metal deck roofing. ACOUSTICON™ has BHP approval for use under all types of Lysaght steel roofing profiles, including Klip-Lok. For more infor mation refer to the Bradford ACOUSTICON™ ‘A Quiet Step Forward’ brochure, available from your nearest Bradford office.
The STC of a roof system (commercial, industrial or domestic) can also be improved with the addition of heavier building materials such as: • addition of insulation between the roof sheeting and Bradford batts above the ceiling, • thicker steel roof sheeting, • using heavier, fire rated plasterboard or multiple layers for the ceiling, • installing a layer of Bradford SOUNDLAGG™ beneath (4 kg/m2 or heavier).
For optimum rain noise reduction under steel roofing in commercial, industrial and residential applications, install 75mm Bradford ACOUSTICON™.
RAIN NOISE REDUCTION WITH METAL DECK ROOFING A common problem of steel roofing is that of rain noise, particularly in tropical climates with high levels of rainfall. Rain falling on metal deck roofing can cause unacceptably high noise levels in the space below the roof. The impact causes the stiff lightweight roof sheeting to vibrate, thus emitting noise. Damping the vibration of the roof sheeting reduces the emitted noise. Rockwool and glasswool blanket products have exceptional noise absorbing properties providing effective damping of the steel roof sheeting. CSR Bradford Insulation in conjunction with CSR Gyprock® have constructed a rain noise testing facility to simulate rain noise using conventional 0.42mm thick BHP Trimdek Hi-Ten metal roof cladding. The rain noise test rig has four nozzles spraying water at high pressure simulate high intensity rainfall. Continuous noise levels of 89dB(A) were created inside the test rig, this noise level was used for controlled testing purposes. Figure 4 shows the rain noise insertion losses achieved by using Bradford Insulation Blankets faced with Thermofoil 729. All tests used 0.42mm BMT BHP Trimdek Hi-Ten steel roofing.
For residential applications, ensure the correct rating of thermal insulation is achieved for roof insulation in your region. At least R2.0 Bradford Rockwool or Glasswool Ceiling Batts should be installed between ceiling joists in conjunction with a Bradford ACOUSTICON™. CSR Bradford Insulation and CSR Gyprock® have conducted many tests using various foil faced roofing insulation blankets, ceiling tiles and fixed plasterboard ceilings. The results of these are shown in Table 5. In tropical climates, roofing insulation is generally installed foil face up, ie. the foil in direct contact with the metal deck roof sheeting. This reduces the insertion loss of the roofing blanket by 2dB. The use of Bradford Rockwool™ ACOUSTICON™ is therefore recommended. Rain noise tests were conducted using the same thickness/density glasswool blanket and varying the surface density of foil. It was found that the mass of the foil has no effect on the rain noise insertion loss achieved by the insulation. ACOUSTICON™ and ANTICON™ roofing blankets should be installed so the blanket is firmly in contact with the steel roofing as shown in Figure 5. This has the added benefit of damping the metal roof sheeting and reducing rain noise.
FIG 4 RAIN NOISE REDUCTION INSERTION LOSSES – FOIL FACED ROOFING BLANKETS.
FIG 5. REDUCTION OF RAIN NOISE – METAL DECK ROOF. 50mm Bradford Rockwool Metal Deck Roofing
Optimum
75mm Bradford ACOUSTICON
50mm Glasswool blanket Bradford Acousticon 50mm Polyester Blanket
10
11
12
13
14
Support Mesh (when specified) 15
16
17
18
19
Bradford Thermofoil Vapour Barrier Purlin
20
Insertion Loss db(A)
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TABLE 5. NOISE REDUCTION CEILING SYSTEMS. Ceiling System Description
Rain Noise Reduction Level dB(A)
• Bradford ANTICON™ R1.5 Blanket hard under metal deck roof
15
• Bradford ACOUSTICON™ hard under metal deck roof
18
• Bradford FIBERTEX™ Rockwool ACOUSTICON™ hard under metal deck roof
19
• Rondo Suspended Concealed Grid Ceiling System. • 1 layer x 13mm Gyprock Plasterboard CD.
22
• Bradford ANTICON™ R1.5 Blanket hard under metal deck roof • Rondo Suspended Exposed Grid Ceiling System. • CSR Gyprock Ecophon™ 20mm Lay-in Ceiling Tiles.
25
• Bradford ANTICON™ R1.5 Blanket hard under the roof. • RONDO Suspended Exposed Grid Ceiling System. • CSR Gyprock CELOTEX™ 16mm Lay-in Ceiling Tiles.
30
• Bradford ANTICON™ R1.5 Blanket hard under the roof. • RONDO Suspended Exposed Grid Ceiling System. • Gyprock 13mm Lay-in Ceiling Tiles.
34
• Bradford ANTICON™ R1.5 Blanket hard under the roof. • RONDO Suspended Concealed Grid Ceiling System. • 1 layer x 13mm Gyprock Plasterboard CD.
37
• • • •
45
Bradford ANTICON™ R1.5 Blanket hard under the roof. RONDO Suspended Concealed Grid Ceiling System. 1 layer x 13mm Gyprock Plasterboard CD. Bradford R1.5 GOLD BATTS or R1.5 Glasswool Building Blanket laid over the ceiling.
• Bradford ANTICON™ R1.5 Blanket hard under the roof. • RONDO Resiliently Mounted Suspended Concealed Grid Ceiling System. 51 • 2 layers x 13mm Gyprock Fyrchek™ Plasterboard. • Bradford R1.5 GOLD BATTS or R1.5 Glasswool Building Blanket laid over the ceiling. Refer to the CSR Gyprock® Fire & Acoustic Design Guide (‘The Red Book’) for additional information on rain noise reduction ceiling systems. See comments regarding: Tropical climate applications in Bradford ACOUSTICON™ brochure. Products for Metal Deck Roofing Systems.
ceiling cavity, the better the low frequency noise reduction.
• Bradford Glasswool Acousticon 75mm. (R1.8) ™
The ceiling can be an important area of a room to place sound absorption particularly, when the remainder of the rooms contains hard reflective surfaces. Rooms having no sound absorbent surfaces typically have high reverberation times. This results in poor acoustics, particularly if communication is required within the room.
• Bradford 50mm Commercial Grade Anticon™. • Bradford Glasswool R1.5 Anticon™ 55mm. • Bradford Glasswool R2.0 Anticon™ 75mm. • Bradford Glasswool R2.5 Anticon™ 95mm. • Bradford 50mm Rockwool ACOUSTICON™.
CEILINGS. Fixed plasterboard ceilings generally provide better sound transmission loss (ie. higher STC) than lightweight suspended ceiling tiles and even plasterboard ceiling tiles. This is because the fixed plasterboard ceiling is better sealed and has less gaps. Multiple layers of plasterboard with resilient mounting and rockwool or glasswool batts in the cavity can provide high STC rating. The larger the
Generally commonly used plasterboard ceilings, whether fixed or lay in ceiling tiles are not very effective at absorbing sound. Typically, sound absorptive ceilings generally consist of: • ceiling tiles made of high density rockwool or glasswool (typically NRC 0.70 – 0.95),
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• perforated plasterboard or perforated metal pan ceilings with Bradford Rockwool or Glasswool insulation (faced with a black tissue) above (good sound absorption NRC 0.60 – 0.90),
G U I D E
FIG 6. IMPROVING SOUND TRANSMISSION CONTROL THROUGH CEILING AREA WITH BRADFORD INSULATION. Poor sound privacy caused by sound flanking through lightweight suspended ceiling
• Mineral fibre ceiling tiles (average sound absorption NRC 0.50 – 0.60).
Ducting
Note that better low frequency acoustic absorption results when ceiling tiles are installed with an air cavity. The larger the air cavity, the better the low frequency acoustic absorption.
Ducting
In many commercial office buildings, noises such as conversations, telephones ringing etc can be heard from one office to another (also known as ‘Crosstalk’). This can cause disruption, annoyance, and decreased productivity. Crosstalk usually occurs from sound flanking via the ceiling. In commercial office buildings, the walls are built up to the underside of the lightweight suspended ceilings (usually a metal grid), not to the concrete slab above. The lightweight ceilings tiles used generally have a low STC rating. The void above wall and ceiling allows sound to ‘flank’ from one room to the next via the acoustically weak ceiling tiles. Ideally, the wall should be built up to the underside of the floor above without gaps for sound to pass from one side to the other.
Improved privacy with Bradford Rockwool or Glasswool Ceiling Batts in ceiling space over wall
Ducting
Ducting
To reduce the amount of sound flanking when a wall does not continue to the underside of the floor above, it is recommended that Bradford Rockwool or Glasswool Ceiling Batts be installed between the wall/ceiling and the underside of the floor above. The more compressed the insulation is when installed in this way, the better the acoustic performance. refer to Figure 6.
Bradford Rockwool or Glasswool Ceiling Batts compressed between ceiling and slab above
Alternatively, to reduce flanking via the ceiling, install Bradford Acoustilag™ from the underside of the concrete slab to the ceiling below as shown in Figures 7 and 8. Products - Ceilings. • Bradford Rockwool Ceiling Batts R1.5, R2.0, R2.5, R3.0. • Bradford Glasswool Ceiling Batts R2.0, R2.5, R3.0, R3.5, R4.0. • Bradford Glasswool Ceiling Panel Overlays (optional Black Matt Facing, or ULTRAPHON™) • Bradford Glasswool Absorption Blanket (optional Black Matt Facing or ULTRAPHON™
Ducting
• Bradford Fibertex™ Rockwool (optional Black Matt Facing or ULTRAPHON™)
Cabling
Bradford Rockwool or Glasswool Partition Batts
NOTE: Care must be taken when passing cables through insulation material due to possible overheating. Consult your electrician for more details.
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Floor/Ceiling Noise Control Systems.
FIG 7. IMPROVING SOUND TRANSMISSION CONTROL THROUGH CEILING AREA WITH BRADFORD ACOUSTILAG CURTAIN.
Bradford Acoustilag curtain continuous in ceiling area
Multi-storey buildings with hard flooring such as timber, parquetry or tiles etc., can efficiently transmit both airborne and impact noise (structure borne vibration) to the rooms below if appropriate techniques are not incorporated at the time of construction. Installing carpet and underlay on the floor can significantly reduce the impact noise to the room below.
250mm minimum
Installing R2.0 or greater, Bradford Rockwool or Glasswool batts between the floor joists will reduce airborne noise by approximately STC 4 – 6.
C-track or timber batten fixed to soffit 100mm minimum
At the time of printing this guide, The Building Code Of Australia (BCA) ‘Sound Insulation of Floors Between Units’ stated ‘a floor separating sole occupancy units must have an Rw of not less than 45’. (Note: Rw 45 approximately equals STC 45). Floors must also provide insulation against impact generated sound.
Suspended ceiling tiles/plasterboard
FIG 8. JOINTING A BRADFORD ACOUSTILAG CURTAIN.
It should be noted that STC 45 is not always adequate in reducing airborne sound through floors and walls. For better acoustic privacy, it is preferable to use a higher rating of say Rw 50 or preferably Rw 55.
75mm Bradford Reinforced Aluminium Tape
RETRO-FIT OF VIBRATION ISOLATED FLOOR. To reduce impact noise transmission through floor/ceiling systems on existing timber, concrete or tiled floors, a floating floor can be constructed on top of the existing floor. The floating floor should use a resilient damping material. Dense Bradford Rockwool, Glasswool or rubber materials can be used but care is needed to choose a material with the correct stiffness for the application and static load. The services of an acoustic consultant should be engaged to solve floor impact noise problems and for the design of ‘floating floors’. Floating floors should not be mechanical fixed (nailed or screwed) to the existing floor as this will couple the two floors resulting in very little damping. The resilient material should also be used between the edges of the floating floor and the walls of the building. Skirting boards should also be isolated or separated from the floating floor. Note the floor/ceiling and floor/door heights may be affected by the use of a floating floor. Doors may also need undercutting if a floating floor is retro-fitted. Therefore where clearances are important, the floating floor height should be kept to a minimum.
Bradford Acoustilag curtain
50mm min. overlap
PENETRATIONS THROUGH BRADFORD ACOUSTILAG CURTAIN. Cut Bradford Acoustilag curtain to allow installation around pipes, ducting etc.
G U I D E
A tight fit should be maintained to ensure acoustic integrity
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1.
2. 3.
4.
5.
D E S I G N
G U I D E
REDUCING NOISE TRANSMISSION THROUGH CONCRETE FLOOR/CEILING SYSTEMS. For concrete floor ceiling constructions, use vibration isolated ceiling hangers or resiliently mounted furring channels to support the plasterboard ceiling.
REDUCING NOISE TRANSMISSION THROUGH TIMBER FLOOR/CEILING SYSTEMS. Fit Bradford R2.0 (or greater) Floor Batts, or Rockwool/Glasswool Ceiling Batts tightly between ceiling joists. Fix one layer of 13mm or 16mm Gyprock Fyrchek™ plasterboard to furring channels. For better acoustic performance (to reduce airborne noise), choose a ceiling with more mass ie. multiple layers of Gyprock® plasterboard CD or Gyprock Fyrchek™ plasterboard. CSR Gyprock® Resilient Mounted Furring Channels will further improve acoustic performance as well as impact isolation. To improve impact isolation of floors, use carpet and good quality thick underlay over timber flooring.
Products. • Bradford Floor Batts. • Bradford Glasswool R2.0, R2.5, R3.0, R3.5, R4.0 Ceiling Batts. • Bradford Rockwool R1.5, R2.0, R2.5, R3.0 Wall/Ceiling Batts. • Bradford Glasswool Quietel™ (for impact isolation). FIG 10. TYPICAL METHODS FOR IMPROVING ACOUSTIC PERFORMANCE OF A CONCRETE FLOOR/CEILING SYSTEM. Carpet and underlay
FIG 9. TYPICAL METHODS FOR IMPROVING ACOUSTIC PERFORMANCE OF A TIMBER FLOOR/CEILING SYSTEM.
SYSTEM
Concrete slab floor
STC/Rw
19/20mm Timber Flooring, 200 x 50 Timber Joists at 450mm centres, 1 layer x 13mm Gyprock plasterboard CD.
35
Add Bradford R2.0 GOLD BATTS™ between joists.
39
Add Gyprock Resilient Mounts and Furring Channels at 600mm centres between joists and plasterboard.
52
Add Carpet and Underlay. Add second layer of 13mm Gyprock plasterboard CD
55
Bradford Rockwool or Glasswool Insulation Suspended ceiling system Gyprock resilient mount
Furring channel Higher density Gyprock plasterboard (Soundchek or Fyrchek) and/or multiple layers
Floors. Improved air-borne sound reduction and impact isolation can be achieved by using floating floors as shown in Figures 11, 12 and 13.
Carpet and underlay Timber flooring Bradford Glasswool or Rockwool Insulation
High density, resilient Bradford Rockwool or Glasswool Quietel™ can break the sound and vibration transmission paths while having sufficient compressive strength to support the floating floor and the room contents. Vibrational energy is absorbed in the resilient material rather than transmitted to the building structure. Not only does a floating floor achieve effective structureborne sound control, but it also reduces the air-borne sound transmission to and from the room below.
Timber joists Furring channel Gyprock resilient mount Use higher density Gyprock plasterboard (Soundchek or Fyrchek) and/or multiple layers
A large range of floor/ceiling systems incorporating alternative acoustic upgrades is detailed in Appendix B of this publication.
The Bradford Fibertex™ Rockwool or Glasswool Quietel™ board are laid flat on the floor, ensuring all joints are tightly butted. At the edges of the rooms, the batts continue up the walls. For the concrete floor, waterproof film is then used to cover the batts and a concrete screed floor of suitable thickness is poured.
Refer to the CSR Gyprock® Fire & Acoustic Design Guide ‘The Red Book’ for additional information on floor/ceiling systems. 24
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All equipment is then mounted on the screed floor which is acoustically isolated from the main building structure.
G U I D E
VIBRATION RESISTANCE. As Bradford Fibermesh™ Rockwool is stitched to wire mesh, the blankets are especially resistant to fallout under conditions where vibration is present. Bradford Fibermesh ™ is particularly suitable for applications involving both vibration and high temperature where standard bonded insulation materials are less resistant to the effects of vibration.
FIG 11 TYPICAL FLOATING FLOOR – TIMBER OVER CONCRETE. Particleboard or timber board flooring
Products. • Bradford Glasswool QUIETEL™. Timber battens
• Bradford FIBERTEX™ HD Rockwool. • Bradford FIBERTEX™ HD (High Density) Rockwool.
Plywood Sheeting
• Bradford FIBERMESH™ Rockwool.
Bradford Fibertex Rockwool or Glasswool Quietel
Structural floor
Plumbing.
Air gap at wall
Noisy pipe work is a common problem in many buildings. These days, pipe work building trends commonly use inexpensive, lightweight, easily to install mater ials with thin wall thicknesses which are unacceptably noisy. Offices, hotels, apartments and domestic houses can all benefit from reduced soil and waste pipe noise levels. Designers, hydraulic consultants, engineers, plumbers, owners and occupants of buildings should all take steps to insulate pipes and ducts to reduce noise.
FIG 12 TYPICAL FLOATING FLOOR – CONCRETE OVER CONCRETE.
50mm Concrete
Floor finish
Water flowing through commonly used PVC soil and waste pipes is predominantly high frequency noise. To effectively reduce pipe noise, lag the pipes with Bradford Acoustilag™ 20, 23 or 26 pipe insulation. The 20, 23, and 26 indicate the ‘A-weighted’ [dB(A)] insertion loss achieved by lagging PVC pipes with each of the Bradford Acoustilag™ product respectively. (Refer to Appendix B for additional information).
Wire mesh
Bradford Fibertex Rockwool or Glasswool Quietel
Structural floor
Waterproof film
FIG 13 TYPICAL FLOATING FLOOR – TIMBER OVER TIMBER JOIST CONSTRUCTION. Timber flooring
Note, the 20, 23 and 26dB(A) insertion losses only apply to water flowing through PVC pipes which have been correctly lagged with Acoustilag. Using Acoustilag for lagging other noise sources, eg., a fan casing or sheet metal air ducts, will generally result in lower insertion losses to those quoted, as these noise sources have more low frequency noise energy.
Plywood sheeting Bradford Quietel Board
To achieve the insertion losses quoted, Bradford Acoustilag™ should be installed with all joins of the lagging overlapped or butted, tightly and taped with Bradford 493 reinforced foil tape. Minimising all the gaps increases the acoustic performance of the lagging.
Plywood sheeting Gyprock plasterboard ceiling
Bradford Glasswool/Rockwool Ceiling Batts
NOTE: The upper plywood layer should not be nailed or screw fixed to the timber below. Instead, it should ‘float’ on the base floor to effectively damp vibration. The floor should also be isolated from the walls. CSR Bradford Insulation recommends consulting an acoustic engineer for the design of floating floor systems.
The Building Code of Australia (BCA) states that: ‘Soil and waste pipes are to be separated if a soil or waste pipe, including a pipe that is embedded in or passes through a floor, serves or passes through more than one sole-occupancy unit:
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(a) The pipe must be separated from the rooms of any sole-occupancy unit by construction with an STC not less than:
of lightweight plastic pipe to substantially reduce plumbing noise. The heavier, stiffer walls of cast iron pipes effectively reduce noise.
(i) STC 45 if the adjacent room is a habitable room (other than a kitchen); or
• If plastic waste water pipes must be used, use Bradford ACOUSTILAG™ to effectively reduce noise.
(ii) STC 30 if the adjacent room is a kitchen or any other room’.
• Insulate all pipes and plumbing that are chased into brick walls.
The Bradford ‘ACOUSTILAG™ Pipe Insulation’ brochure provides systems using CSR Gyprock ® plasterboard to achieve the STC noise criteria specified by the BCA. The STC 50 system specified in that brochure is intended for applications requiring better acoustic isolation from waste pipe noise than is specified in the BCA eg., board rooms, offices, apartments and hotels etc.
• Select quieter plumbing equipment and appliances eg. cisterns, washing machines, clothes dryers etc. Products. • Bradford ACOUSTILAG™ 20, 23 or 26. • Bradford 493 reinforced foil tape. • ARMAFLEX® insulation.
To achieve the STC’s specified in Table 6, it is imperative that the pipes be correctly lagged (no gaps to allow noise leakage), and the plasterboard ceiling and walls above be airtight with no gaps into the next room.
Quietening Box Gutters & Downpipes.
It is recommended the services of an acoustic consultant or acoustic engineer be used to achieve specified STC ratings. Penetrations, ducting, light fittings, gaps in ceilings etc., can degrade the acoustic rating of the lagging and ceiling system.
Box gutters should be insulated with Bradford FLEXITEL™ or SUPERTEL™ Glasswool (25mm thick) faced with heavy duty foil. Insulation can be attached to gutters using 45mm long Bradford self-adhesive fasteners and washers at 300 mm centres. Insulation should be held firmly against the metal surface for maximum dampening. For better noise reduction, use Bradford ACOUSTILAG™ 20.
To minimise annoyance from plumbing noise, it is advisable, at the design stage, to avoid placing bathrooms and laundries etc., adjacent to noise sensitive areas.
Noisy downpipes should be insulated with Bradford Glasswool Sectional Pipe Insulation faced with Heavy Duty Thermofoil. Alternatively a 25mm wall thickness ARMAFLEX ® pipe insulation or Bradford ACOUSTILAG™ 20 can be fitted around downpipes.
Methods for minimising plumbing noise include: • Select vibration isolated pipe hangers to support pipes and minimise transmission of vibration into the building structure. These will reduce ‘water hammer’ noise when turning the water taps on or off. Alternatively use ARMAFLEX® insulation between pipes and the building structure.
Products. • Bradford Glasswool FLEXITEL™ or SUPERTEL™. • Bradford ACOUSTILAG™ 20.
• Use water supply and drain pipes that are oversized, this may reduce line pressure and minimise flow noise. • Where possible, use cast iron waste water pipes in place
TABLE 6. ACOUSTIC INSULATION SYSTEMS FOR PLUMBING. System STC/Rw Bradford CSR Gyprock® ™ Nº Rating. ACOUSTILAG Plasterboard
Bradford Insulation
BAS 01
30
ACOUSTILAG™ 20
1 layer 10mm Gyprock CD™
Nil
BAS 02
45
ACOUSTILAG™ 20
2 layers 13mm CSR Gyprock CD™
75mm Bradford Glasswool R1.5
BAS 03
45
ACOUSTILAG™ 23
2 layers 10mm CSR Gyprock CD™
75mm Bradford Glasswool R1.5
BAS 04
50
ACOUSTILAG™ 23
2 layers 13mm CSR Gyprock CD™
100mm Bradford Glasswool, R2.0
BAS 05
50
ACOUSTILAG™ 26
2 layers 13mm CSR Gyprock CD™
75mm Bradford Glasswool R1.5
Refer to the Bradford ACOUSTILAG™ brochure for additional information. 26
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Insulation Cladding of Pipes, Tanks & Vessels.
G U I D E
FIG 14. BASIC NOISE CONTROL METHODS. Absorbent Lining reduces sound level within enclosure
The insertion loss achieved by cladding pipes, tanks and vessels will depend on a number of factors such as the frequency of the fluid in the pipe the type and mass of the cladding material, the thickness and density of the (rockwool or glasswool) insulation.
Insulation reduces sound flow to outside
Vibration Damping of fan casing reduces sound emission Vibration Isolation Mounting reduces vibration transmission to floor
It should be noted that some of these cladding systems can actually amplify the noise at lower frequencies, particularly if insulation with a high density is used. This generally happens as the tank now has a larger radiating surface. Therefore it is difficult to predict the insertion loss of cladding systems.
REVERBERATION CONTROL. Factories and engineering workshops usually are reverberant spaces due to the lack of sound absorption within the space. Areas with multiple noise sources, such as factories, engineering workshops, bottling plants, machine halls, plant rooms etc usually have a high level of reverberant noise often exceeding the safe regulatory noise level of 85dB(A). The use of sound absorbing materials (such as glasswool and rockwool) to reduce reflected or reverberant sound is the most effective means of reducing overall sound levels in enclosed areas. CSR Bradford Insulation manufacture a range of rockwool and glasswool products with outstanding sound absorption properties. These products have been tested in acoustic reverberation rooms to determine the sound absorption coefficients presented in the technical data section. A range of factory-applied facings is available, the most common being: • black fibreglass tissues (BMF), or ULTRAPHON™ • THERMOFOIL™ laminates (solid and perforated). An extremely effective acoustic absorber for walls and ceilings is Bradford ACOUSTICLAD™ – a roll formed panel, factory lined with Bradford FIBERTEX™ 350 Rockwool. Each panel interlocks with its neighbour forming a structurally reinforced joint. Bradford ACOUSTICLAD™ offers excellent test results with NRC ranges from 0.9 to 1.05. Contact CSR Bradford Insulation for a brochure or refer to Appendix C for the Bradford ACOUSTICLAD ™ absorption coefficients in 1/3 octave bands.
It should be noted that Bradford Rockwool or Glasswool SPI (sectional pipe insulation) will reduce pipe noise but not as effectively as Bradford ACOUSTILAG™ or insulation with a mass barrier. Higher density, means it is less resilient than Bradford ACOUSTILAG™ and more efficiently transfers noise and vibration from the pipe to the cladding/barrier. Note: Bradford ACOUSTILAG™ is not recommended for high temperature applications. Refer to the CSR Bradford Industrial Insulation Design Guide for installation details of cladding and pipe lagging.
Factories & Engineering Workshops. The basic methods by which industrial noise may be controlled are: • Sound absorption – absorbing the noise using mineral fibre materials which can dissipate the sound energy as heat. • Sound insulation (enclosing) – containing the noise in one area so that it does not cause annoyance in other areas. • Vibration damping – damping vibrating surfaces to reduce air borne sound emission. • Vibration isolation – preventing acoustic energy from entering the building structure. These processes are illustrated in Figure 14. As the figure shows, treatment of a factory noise problem often involves a combination of the basic processes.
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TABLE 7. ACOUSTICLAD TEST RESULTS. ™
Acousticlad™ Perforated % Open Area
Test Sample Configuration
15%
50mm thick Bradford FIBERTEX™ 350 Rockwool (60kg/m3) Insulation with black matt facing (BMF) between the Rockwool and Acousticlad face.
1.00
25%
as above
0.95
40%
as above
1.00
15%
23mm thick Mylar film between unfaced Bradford FIBERTEX™ 350 Rockwool and ACOUSTICLAD™ perforated aluminium.
0.90
50mm thick Bradford FIBERTEX™ 350 Rockwool Insulation with black matt tissue between the Rockwool and perforated aluminium. Timber spacers supporting panels with average air gap 30mm.
1.05
15%
Noise Reduction Coefficient NRC Rating
Notes – All acoustic tests were conducted with ACOUSTICLAD™ perforated aluminium panels (0.7mm thick), with Bradford 50mm thick FIBERTEX™ 350 Rockwool (60kg/m3) insulation. – Acoustic tests were conducted in the reverberation room at the National Acoustic Laboratories, Chatswood, Sydney, Australia. – See Appendix C for absorption coefficients at each 1/3 Octave band frequency.
A commonly used cost effective method for fixing insulation (generally faced with perforated foil) on walls and ceilings uses drive pins and speed clips. These eliminate the need for battens or furring channels. The drive pins are fixed to the wall usually at 450mm centres. The insulation is pushed through the pins and held onto the pin by the speed clips of a suitable size.
Bradford ACOUSTICLAD™ perforated metal is available with percentages of open area ranging from 10% to 55% and in a number of finishes including: • galvanised steel, • powder coated steel, • stainless steel and • aluminium.
Rigid facings such as perforated metal or pegboard are unsuitable for this application method. The advice of adhesive suppliers should be sought before using adhesively fixed pins in lieu of drive pins.
Fixing details for Bradford ACOUSTICLAD™ are available from your nearest Bradford office. Bradford Rockwool and Glasswool insulation is available with a range of facings, including:
Ceilings may be lined by the same methods as walls. An alternative approach is to use a fully exposed metal suspension grid which makes it a simple matter to achieve any air gap required behind the batts
• perforated metal or expanded metal. • perforated foils, • pegboard,
Factories contain noise which predominantly has most energy at low frequencies which is difficult to absorb unless very thick insulation is used. To increase the low frequency sound absorption of perforated noise absorbers (such as Bradford ACOUSTICLAD™), introduce an air gap behind the insulation. This can be achieved by using larger battens or furring channels with chicken wire to retain the batts in position, as shown in Figure 15 below. Better acoustic absorption results when the depth of the air cavity is at least as thick as the insulation.
• wire, • plastic mesh. Any perforated sheet facing should have an open area greater than 10% to maximise acoustic absorption. Other common methods for acoustic wall treatment involve: • fixing timber battens or steel furring channels or ‘Z’ sections at a spacing to suit the facing sheets. Bradford Rockwool and Glasswool batts are cut to size if necessary and friction fitted between the supports. The protective facing (e.g. perforated or expanded metal, plastic mesh, pegboard, wire etc.) is fixed to the furring sections or battens by nails, screws, or rivets as appropriate. Cover strips are used to improve the appearance.
Alternatively, rockwool or glasswool insulation greater than 75mm can be used with acoustically transparent facings mentioned above.
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FIG 15. ABSORPTIVE LINING WITH AIR GAP TO BOOST LOW FREQUENCY ABSORPTION (PLAN VIEW). Chicken wire
Bradford Fibertex Batts
Structual wall
G U I D E
FIG 16. BRADFORD ‘ACOUSTIC BAFFLES’ USED TO ABSORB SOUND FROM NOISY EQUIPMENT.
Air gap
Battens
Facing eg. perforated metal
Products. • ACOUSTICLAD™ with perforated metal facing is available in various thicknesses and open area percentage to accommodate acoustic absorption requirements. The following Bradford products can also be used: • Bradford Rockwool FIBERTEX™ 350, 450.
Installation Method 1.
• Bradford Glasswool FLEXITEL , SUPERTEL , ULTRATEL™ with perforated metal, expanded metal, wire, meshes or perforated heavy duty grade foil facings. ™
™
The baffles can be individually suspended from the roof structure using ‘S’ hooks, galvanised wire or fine chain. In this case, suspend baffles approximately 1 metre below the ceiling level if possible.
Bradford Acoustic Baffles.
FIG 17. ACOUSTIC BAFFLES SUSPENDED AND ARRANGED IN A CROSS-HATCH PATTERN.
Large factories or buildings may need a greater area of acoustic absorbing insulation than just the wall area, or may need it concentrated in a particularly noisy section of the building.
Roof framing
Bradford Rockwool Acoustic Baffles may be suspended in any desired pattern to achieve extra sound absorption in a building. Refer to Figure 16 and 17.
Suspension wire or chain
'S' Hook
Sound absorption coefficients of Bradford Rockwool Acoustic Baffles are shown in Table 8.
BAFFLE INSTALLATION. Two popular methods of installation are detailed. Baffles may be installed at any height, and do not need to be all in the same plane. A regular pattern such as parallel rows or a staggered, cross-hatched pattern is most easily installed using a suspended ceiling grid. Determine the number of acoustic baffles to be installed to meet the noise reduction required. The typical number of baffles is 1 baffle per square metre of ceiling area. Allowance should be made for lights and sprinklers.
Bradford Acoustic Baffles in cross-hatch pattern
TABLE 8. SOUND ABSORPTION COEFFICIENTS OF BRADFORD ACOUSTIC BAFFLES. Product
Density Thickness Facing (kg/m3) (mm) 125 Bradford Acoustic Baffle 60 50 30µm 0.18 plastic film 29
250 0.44
Frequency (Hz) 500 1000 2000 4000 5000 0.83 1.25 1.14 0.96 0.94
NRC 0.90
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noise level by about 5dB more than a 1mm sheet steel enclosure, assuming all other conditions are equal.
Installation Method 2. Inverted 50mm x 12mm aluminium U-channels are fixed to the underside of a ceiling grid. The baffles are then secured to the U-channel using self tapping screws.
Enclosures do not attenuate all frequencies of sound equally, so the transmission loss achieved will depend on the frequency spectrum of the noise source. High frequency noise is more easily attenuated than low frequency noise.
FIG 18. ACOUSTIC BAFFLES FIXED IN ALUMINIUM TRACK AND ARRANGED IN A PARALLEL PATTERN.
Thus, while a lightweight enclosure may provide effective transmission loss for a high frequency noise source, it could however be inadequate for low frequency noise sources.
Main suspension grid
Flanking transmission paths permit sound to by-pass the acoustic enclosure. Typical examples are air gaps, windows, doors, service penetrations etc. To avoid severe reductions in insulation performance, steps should be taken to eliminate these flanking paths as far as practical. Caulking of air gaps and penetrations, use of door seals or even double doors, resiliently mounted double glazing, use of flexible couplings on pipes and ducting which penetrate the enclosure are all means of reducing flanking transmission.
Aluminium channel
Bradford Acoustic Baffles arranged in parallel pattern
Products.
Flanking through the floor of an enclosure can limit the transmission loss. Sound and vibration entering the floor on the noisy side of the enclosure can be re-radiated to some extent on the other side.
• Bradford Rockwool Acoustic Baffles.
Acoustic Enclosures.
The sound insulation performance of lightweight enclosures may be significantly improved by the use of double-leaf construction with a core of sound absorbing rockwool or glasswool as shown in Figure 20. The performance will be further enhanced if the two leaves are of different surface densities eg: one leaf may be 1.6mm steel sheet while the other is 1.2mm steel sheet. This reduces resonant coupling between the sheets.
Enclosures are an effective method of reducing noise emitted from a particular machine or noise source. They should be constructed of solid materials such as bricks, sheet steel, timber, plasterboard etc. Enclosures reduce noise more effectively when they are airtight, with no gaps or openings. This is not always possible as the machinery inside may need to be accessed by other machines or people, or require air flow for cooling.
The sound reduction achieved depends on the surface density of the enclosure. Heavy materials like steel sheet greater than 1.0mm, 16mm plywood or 19mm particle board are typically used.
Enclosures built around machiner y actually concentrate the noise inside the enclosure. Therefore it is good practice to line the inside of enclosures with Bradford Rockwool or Glasswool to reduce reverberant noise levels inside.
As well as trapping sound, enclosures of the type shown in Figure 19 and 20 will also trap heat. It is often necessary therefore to ventilate these enclosures to avoid overheating of the enclosed machinery. Ventilation openings must also be acoustically treated to reduce the escape of sound through these openings. The use of packaged attenuators, insulation lined ducts or acoustic louvres are commonly used.
A simple acoustic enclosure is shown in Figure 19. It has three main components: (i) an internal lining of sound absorbent rockwool or glasswool insulation to reduce the noise level inside the enclosure. (ii) a heavy barrier to reduce sound transmission to the outside.
Absorptive treatment may include not only lining the walls and ceiling of an enclosure but also the use of discrete screens or baffles. The latter are of particular value where it is important that the absorptive treatment does not interfere with the dissipation of heat. Where heat could cause a problem, then Bradford Rockwool Acoustic Baffles are specially designed for suspension below existing
(iii) a resilient pad of felt or rubber to isolate the enclosure from the floor (optional). Broadly speaking, the sound transmission loss of an enclosure improves by about 5dB for every doubling of the surface density (mass per square metre or kg/m2). Thus, a 2mm thick sheet steel enclosure will reduce the 30
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factory roofs. Their sound absorption performance is detailed in the previous section. Baffles will not however be as effective at reducing noise as an enclosure.
FIG 19. ACOUSTIC ENCLOSURE. Bradford Fibertex 450 Rockwool or Ultratel
G U I D E
Heavy Gauge Steel Sheet
An example of an acoustic enclosure for very high acoustic insulation is detailed in Fig 21. It shows a room within a room. These rooms are vibration isolated from each other.
INSTALLATION DETAILS. Installation of the sound absorbing rockwool or glasswool batts to the inside surfaces of the enclosure proceeds in a similar manner to that previously described for reverberation control. Where double-leaf construction is employed a larger number of variations are possible. One simple yet effective procedure follows: Construct a suitable frame using steel angles, channels, or box sections to provide at least 63mm clearance between the two leaves. (Note the wider the cavity, the better the low frequency sound transmission loss). Mount this frame on a continuous thick rubber mat. The outer steel sheeting should then be fixed to the frame as shown in Figure 21, using rubber strips to reduce sound transmission from the frame to the sheet.
Rubber Mounting
FIG 20. ACOUSTIC ENCLOSURE WITH DOUBLE-LEAF CONSTRUCTION. Bradford Fibertex 450 Rockwool or Ultratel
Heavy Gauge Steel Sheet
Rubber Mounting
FIG 21. ACOUSTIC ENCLOSURE WITH VERY HIGH ACOUSTIC INSULATION. Heavy duty flexible pipe connection, and resilient mounted pipe/ductwork
Minimum cavity of 200mm
Bradford Insulation Blanket Two steel soundproof doors with all edges sealed
Existing window
Small double glazed viewing window
Bradford Insulation Blanket in cavity
Main structure of building Resilient/floating floor system
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Fix 50mm thick FIBERTEX R350 to the inside of the sheeting using weld pins and speed clips. Bend over the ends of the pins if necessary to avoid contact with the inner steel sheeting when installed.
G U I D E FIG 22. A PARTIAL ENCLOSURE.
™
The inner sheeting may now be fixed to the frame, again as shown in Figure 21. The sound absorbing rockwool or glasswool batts may now be fixed to the inside of the inner sheet using weld pins, speed clips, and a suitable facing (wire, meshing, perforated foil). Alternatively, a perforated metal (such as Bradford ACOUSTICLAD™) or expanded metal can be used, or for an aesthetically pleasing finish. Any gaps, openings or joins in the outer leaf of the enclosure, should be caulked and doors should use acoustic door seals. Products. • Bradford Rockwool FIBERTEX™ 350, 450. • Bradford Glasswool FLEXITEL™, SUPERTEL™, ULTRATEL™. • Bradford ULTRAPHON™ facing. FIG 23. TYPICAL NOISE PROBLEM WITHOUT ACOUSTIC ENCLOSURE .
Partial Enclosures & Screens. It is not always practical to totally enclose a noisy machine. However, the use of a partial enclosure or screening will still achieve some reduction in noise levels particularly close to the screens. The previous discussion on total enclosures also applies to partial enclosures. However the overall noise reduction of partial enclosures will not be as great, due to the openings. As far as is practical, employee work stations should be located in the shadow zone of the screening and not in line with the openings in the enclosure. Reflective surfaces near openings in a partial enclosure should be treated with rockwool or glasswool insulation to absorb noise.
FIG 24. IMPROVED NOISE CONTROL WITH A PARTIAL ENCLOSURE.
Where a particular noise source contr ibutes significantly to the overall noise level in a room, it may be controlled by a partial enclosure of the type shown in Figure 22. Much of the sound produced within the enclosure is absorbed, thus reducing the amount of sound radiated into the room. Partial enclosures can be simply fabricated by sandwiching FIBERTEX™ Rockwool or Glasswool Batts between an outer sheet of plywood and an inner lining of pegboard. Alternatively, plain hardboard, particleboard, plasterboard, or sheet metal may be used for the outer sheet, while the inner lining may be perforated or expanded metal. The effectiveness of a partial enclosure depends in part on the weight of the outer sheet and the percentage of the machinery that is enclosed. 32
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The choice of which type of Bradford FIBERTEX Rockwool or Glasswool to use should be based on the frequency spectrum of the noise source. Select the material with the highest sound absorption for the dominant frequency bands of the noise source. High frequency sound absorption will be affected by the inner lining. Should the dominant frequency bands of the noise source be above 1000 Hz, the inner lining should have a perforated open area of 11% or more to ensure optimum sound absorption.
concerned. However, local absorption permits reduction in sound levels without significantly altering the room reverberation time.
The effect of local absorption will be limited by the need to provide access or ventilation to the equipment
• Bradford Glasswool FLEXITEL™, SUPERTEL™, ULTRATEL™.
™
Figures 23 and 24 show a typical application of a partial enclosure to reduce noise reaching an operator. Figure 23 and 24 illustrate the use of partial acoustic enclosures in a car assembly line application. Products. • Bradford Rockwool FIBERTEX™ 350, 450.
• Bradford ULTRAPHON™ or HD Perf. facings. FIG 25. TYPICAL NOISE PROBLEM WITHOUT ACOUSTIC ENCLOSURE.
FIG 26. TYPICAL PARTIAL ACOUSTIC ENCLOSURE APPLICATION.
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Vibration Damping.
ACOUSTIC SCREENS. Simple acoustic screens may be fabricated as shown in Figure 27, and these may be supported in any framing suitable to the particular application. Screens can act in three ways: • As local sound absorbers (i.e. a simple partial enclosure), • As reverberation control (i.e. more absorption is introduced to the room), • As a partial barrier (i.e. an acoustic shadow zone is created behind the screen). For maximum effect, acoustic screens should be located as close as practical to the noise source or to people affected by the noise. They should be as large as possible, at least the height or width of the machine or noise source. Air flow requirements should be considered.
Vibrating surfaces such as fan casings, pipes, and ducting can be a major source of noise. Lagging these surfaces will significantly reduce the noise radiated from the sources. When treating such surfaces in this manner, it is essential that lagging be applied over the entire sound-radiating surface. It is also necessary to avoid bridging connections between the radiating surface and the outer cladding. Otherwise, the vibration will be transmitted directly to the cladding which will itself become a sound-radiating surface. FIG 28. FIXING STEEL SHEET TO MINIMISE NOISE TRANSMISSION.
Products. • Bradford Rockwool FIBERTEX™ 350, 450. Enclosure Frame
• Bradford Glasswool SUPERTEL™, ULTRATEL™.
Other steel Sheet
• Bradford ULTRAPHON™ facing. FIG 27. A SIMPLE ACOUSTIC SCREEN.
Fixing Screw
Decorative, non-reflective fabric
Rubber Grommet
VIBRATION ISOLATION. Vibration isolation involves the isolation of vibrating machinery from the building structure. In practice this is achieved by using flexible, resilient mountings, such as rubber-in-shear rubber or steel springs. Where equipment is mounted on inertia blocks, there are often advantages in using a continuous layer of dense rockwool or rubber as the vibration isolator.
Heavyweight plywood or metal core
Fibertex Rockwool or Glasswool Protective metal edges
FIG 29. FIBERTEX™ ROCKWOOL AS A VIBRATION ISOLATOR.
NOTE: Where the noise level emitted by a factory is above acceptable community standards, it is wise to engage the services of a noise control engineer. Environmental noise legislation is quite complex, and failure to comply with the relevant noise criteria may result in severe penalties. Each situation presents its own unique problems which must be identified and then corrected.
Resilient Fibertex Rockwool HD Inertia Block Z-Section Waterproof Film
Plant Room Floor
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By acting equally under the entire area of the block, the layer of rockwool dampens the rocking motion that may be present and eliminates point loading on the structural floor. The static deflection characteristics of CSR Bradford Insulation products are shown in Product Guides.
G U I D E
FIG 31. TYPICAL APPLICATIONS OF ARMAFLEX® (a) PIPE SUPPORT.
The use of rockwool as an isolator is not recommended where the required static deflection exceeds 10mm. In such cases it is advisable to use rubber or steel springs.
VIBRATION RESISTANCE. Bradford FIBERMESH™ is particularly suitable for applications involving both vibration isolation as well as high temperature, where standard bonded insulation materials are less resistant to the effects of vibration. Bradford FIBERMESH™ rockwool is stitched to wire mesh making the blankets especially resistant to fallout under conditions where vibration is present.
FIG 32. TYPICAL APPLICATIONS OF ARMAFLEX® (b) PENETRATION THROUGH SOUND INSULATING WALL.
FIG 30. DENSE GLASSWOOL BOARD USED FOR VIBRATION ISOLATION OF MACHINES. Sound Insulating Wall
Use vibration absorbing flexible couplings on all rigid connections to the vibration source
False flange (must not contact pipe)
Pipe
Bradford Armaflex Flexible Pipe Insulation
Flexible Mastic (sealing gap between flange and pipe)
INSTALLATION RECOMMENDATIONS. Installation commences with the laying of a suitable water proof film on the plant room floor. The FIBERTEX™ Rockwool batts are laid flat on the film, ensuring all joints are tightly butted. The area covered by the batts should exceed the dimensions of the inertia block by at least 50mm on each side. The waterproof film should be wrapped around the outer edges of the FIBERTEX™ Rockwool batts and retained in position by metal U-channels, timber battens, or other suitable protective treatment. The edging material, when installed, must allow for a 3mm gap between itself and the inertia block. This gap, and any gaps or joins in the edging material should be sealed with a flexible, waterproof mastic.
Bradford Quietel Glasswool Board for vibration isolation
Isolation of machinery from the floor structure will not achieve its design performance if flanking vibration paths remain. All connections to the equipment, such as piping, ductwork, and electrical conduits, should incorporate a vibration absorbing flexible coupling, and should also be isolated from the building structure by flexible mounts. ARMAFLEX® flexible pipe insulation, a closed cell nitrite rubber tubing, provides an excellent vibration isolation gasket for piping and conduit. Typical applications are shown in Figures 31 and 32.
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based on the selected Noise Rating number plus corrections for the characteristics of the room and the distance to the nearest occupant. If the design goals have not been achieved, the additional attenuation needed at each frequency band must be designed into the system. Duct attenuators can be used, however the most economical approach where space permits is using internal duct liners.
Air Conditioning Noise Control. Noise arises in air handling systems principally from fans and from air flow generated noise in both ducts and through registers. It is sometimes necessary to deal with sound transmitted along a duct from one room to another. This section provides methods and data to assist in the design of internal duct lining to control noise.
FAN NOISE. Generally the fan manufacturer will provide data on fan noise characteristics. However if no data is available, the following empirical formulae developed by Beranek may prove useful: SWL = 77 + 10 log kW + 10 log P SWL = 25 + 10 log Q + 20 log P SWL = 130 + 20 log kW - 10 log Q Where: SWL = overall fan sound power level, dB kW = rated motor power, kW P = static pressure developed by fan, mm w.g. Q= volume flow delivered, m3/h Octave band sound power levels are then found by subtracting correction factors from the overall sound power level calculated by any one of the above formulae. Maximum noise usually occurs from the blade tip frequency of the fan. This is determined from the number of blades on the fan rotor multiplied by the number of revolutions per second. The octave band in which the blade tip frequency falls will have the highest sound power level and therefore the smallest correction factor to be subtracted from the overall sound power level. A fan’s rotating blades produce tones at the blade pass frequency (BPF).
The fan in air conditioning systems is generally the main noise source. The types of fans used are either axial type or centrifugal type fans. Axial fans generate a higher proportion of high frequency noise but less low frequency noise than centrifugal fans of similar duty. The fan manufacturer should be able to supply sound power spectrums of fan noise. Noise also arises from airflow generated in both the ducts and registers (also known as regenerated noise). Usually the greater the velocity of the air through the ducts, the higher the regenerated noise level.
NOISE CRITERIA. Noise Criteria curves (NC) and Noise Rating numbers (NR) have been developed to approximate loudness contours and speech interference levels at particular frequencies. These criteria graphs indicate a sound pressure level at each frequency that will be appropriate in a particular environment. Noise Rating numbers are covered by Australian Standard AS1469 : 1983 ‘Acoustics – Methods For The Determination Of Noise Rating Numbers’. Sound levels are often expressed in A-weighted decibels. Australian Standard AS2107 : 1987 ‘Acoustics – Recommended Design Sound Levels And Reverberation Times For Building Interiors’ covers the recommended background sound levels for occupied spaces makes use of the dB(A) weighting. It is recommended that design calculations of noise reduction use Noise Rating numbers and then convert to dB(A) at the end of the calculations.
BPF =
rpm x 60 N
Where: BPF = blade pass frequency (Hz)
GENERAL PROCEDURE. The fan sound power level is first established, then each duct path is examined separately. Noise generated by 90° elbows and branches is estimated using data from the Sound and Vibration section of the ASHRAE Guide and Data Book and added to the fan noise. From this is deducted any branch take-off losses and the natural attenuation due to straight runs of duct work, elbows and end reflections losses, again using the data tabulated in the ASHRAE Guide. The resultant sound power level represents the noise reaching the conditioned space. This is compared to the design requirements for the space
rpm = revolutions per minute N = number of fan blades Har monics and sub-har monics may result at frequencies which are multiples of the blade pass frequencies. The recommended correction factors are indicated in Table 9.
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TABLE 9. CORRECTIONS FOR FAN SOUND POWER LEVELS. Blade Tip Frequency Fan Type Centrifugal Backward Curved Blades Forward Curved Blades Radial Blades Axial Mixed Flow
Band 4 2 3 7 0
1st Octave 6 6 5 9 3
DUCT ATTENUATION. Air handling duct work is internally lined using rockwool or glasswool insulation boards or blankets faced with an acoustically transparent facing to provide adequate sound absorption by the insulation. In addition the facing must provide minimal airflow resistance inside the duct and may also need to act as a vapour barrier. For maximum sound absorption, the duct liner’s facing should be as light and porous as possible to allow sound to penetrate it. Internal duct liners commonly use Bradford R-rated Ductliners, SUPERTEL™ or ULTRATEL™ Glasswool faced with: • Bradford ACOUSTITUFF™ • Bradford ULTRAPHON™ woven glass fabric, • Lightweight THERMOTUFF™ , • Heavy Duty 750P THERMOFOIL™ perforated, • Black or clear fibreglass tissue or • Fine, lightweight polyester films (Mylar or Melinex). Appendix C, Table C7, Contains comparative noise reduction coefficients for Bradford products.
2nd Octave 9 13 11 7 6
3rd Octave 11 18 12 7 6
4th Octave 13 19 15 8 10
5th Octave 16 22 20 11 15
6th Octave 19 25 23 16 21
The most important octave bands where fan noise is concerned are the 125Hz and 250Hz bands. Ducts internally lined with a suitable length and at least 50mm thickness of Bradford Glasswool or FIBERTEX ™ Ductliner can effectively reduce the low frequency component of fan noise. The thicker the internal duct liner, the better the low frequency sound absorption. The thermal performance of the insulation for air conditioning ducts can be calculated using the data in the CSR Bradford Insulation Air Conditioning Design Guide. Table 10 is a guide to the attenuation achieved by lining two opposite sides of a duct with Bradford Glasswool ULTRATEL™ at 50mm and 100mm thickness. The distance ‘D’ is the depth in mm between the linings. It is assumed that any facing material used is deemed acoustically transparent. If the duct is to be lined on all four sides, the total attenuation may be obtained by arithmetically adding the attenuation achieved by lining the other two opposite sides.
TABLE 10. CALCULATED LINED DUCT ATTENUATION, dB/m. Lining Thickness 50mm
Depth Between Linings ‘D’ mm 200 300 400 600 800 1000 100mm 200 300 400 600 800 1000 Limit of Attenuation
125 1.3 1.2 1.2 1.0 0.6 0.5 4.3 3.2 2.1 1.7 1.3 0.8 26
250 4.5 3.3 2.6 1.5 1.2 1.1 8.8 6.5 5.4 3.8 2.9 2.0 31
Frequency (Hz) 500 1000 10.8 15.8 7.7 9.2 5.8 8.0 3.5 3.4 2.4 2.0 2.0 1.1 14.5 15.8 10.2 9 7.9 8.0 5.2 3.4 4.0 2.0 3.1 1.1 38 42
2000 15.4 6.8 3.8 1.6 1.0 0.6 15.4 6.8 3.8 1.6 1.0 0.6 50
4000 7.7 3.4 1.9 0.9 0.4 0.3 7.7 3.4 1.9 0.9 0.4 0.3 60
Table 10, shows that the smaller the duct dimensions, the higher the attenuation per length of duct. 1 Sound Research Laboratories, Noise Control in Building Services, Pergamon Press, First Edition 1988.
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A C O U S T I C Straight Duct Circular/Oval or Rigid Walled (unlined)
x
Straight Duct Rectangular (unlined) x
x
D E S I G N
G U I D E
TABLE 11. ATTENUATION OF UNLINED DUCTS. Duct Dimensions Octave Band Centre Frequency Hz) ‘x’ (mm) 63 125 250 500 1k 2k Attenuation dB/metre run 0.07 0.10 0.10 0.16 0.33 0.33 75 – 200 0.07 0.10 0.10 0.16 0.23 0.23 200 – 400 0.07 0.07 0.07 0.10 0.16 0.16 400 – 800 0.03 0.03 0.03 0.07 0.07 0.07 800 – 1500 Duct Dimensions ‘x’ (mm)
63
75 – 200 200 – 400 400 – 800 800 – 1500
0.16 0.49 0.82 0.66
Octave Band Centre Frequency Hz) 125 250 500 1k 2k Attenuation dB/metre run 0.33 0.49 0.33 0.33 0.33 .66 0.49 0.33 0.23 0.23 0.66 0.33 0.16 0.16 0.16 0.33 0.16 0.10 0.07 0.07
4k 0.33 0.23 0.16 0.07 4k 0.33 0.23 0.16 0.07
TABLE 12. IN-DUCT ATTENUATION WITHIN EXTERNALLY LAGGED DUCTS. Straight Duct Duct Dimensions Octave Band Centre Frequency Hz) Circular/Oval or ‘x’ (mm) 63 125 250 500 1k 2k 4k (externally lagged) Attenuation dB/metre run 0.14 0.20 0.20 0.32 0.33 0.33 0.33 75 – 200 x 0.14 0.20 0.20 0.32 0.23 0.23 0.23 200 – 400 0.14 0.14 0.14 0.20 0.16 0.16 0.16 400 – 800 0.06 0.06 0.06 0.14 0.07 0.07 0.07 800 – 1500 Straight Duct Rectangular (externally lagged) x
x
Duct Dimensions ‘x’ (mm)
63
75 – 200 200 – 400 400 – 800 800 – 1500
0.33 1.00 1.64 1.32
Octave Band Centre Frequency Hz) 125 250 500 1k 2k Attenuation dB/metre run 0.66 1.00 0.66 0.33 0.33 1.32 1.00 0.66 0.23 0.23 1.32 0.66 0.32 0.16 0.16 0.66 0.32 0.20 0.07 0.07
4k 0.33 0.23 0.16 0.07
TABLE 13. ATTENUATION OF RADIUS BENDS. Straight Duct Circular/Oval or Rigid Walled (unlined) D
D
Duct Dimensions ‘D’ (mm)
63
150 – 250 250 – 500 500 – 1000 1000 – 2000
-
Octave Band Centre Frequency Hz) 125 250 500 1k 2k Attenuation dB 1 2 1 2 3 1 2 3 3 1 2 3 3 3
4k 3 3 3 3
There are positive steps that can be taken to counter the effect of flanking transmission but for the purpose of this guide it is recommended that, in using these Tables, reliance should not be placed on achieving attenuation in excess of the limiting values shown. If attenuation beyond these limits is required, it should be achieved by other acoustic treatment or lining at a location remote from the length of duct under consideration.
For more examples of duct losses, refer to ASHRAE (American Society Of Heating Refrigeration Engineers) publications. It should be noted, that a limit to the attenuation of sound in duct work may be imposed by flanking transmission or noise breakout. This particularly occurs when the aim is to achieve high attenuation in a short length of straight duct. 38
CSR BRADFORD INSULATION
A C O U S T I C
D E S I G N
G U I D E
TABLE 14. ATTENUATION OF MITRE (90°) BENDS. Mitre Bend (unlined)
D
Mitre Bend (lined) D Lining Thickness = 10 Lining to extend distance 2D or greater
D
Duct Dimension ‘D’ (mm)
63
75 – 200 100 – 150 150 – 200 200 – 250 250 – 300 300 – 400 400 – 500 500 – 600 600 – 700 700 – 800 800 – 900 900 – 1000 1000 – 1100 1100 – 1200 1200 – 1300 1300 – 1400 1400 – 1500 1500 – 1600 1600 – 1800 1800 – 2000
1 1 1 2 2 3 5 6
Duct Dimension ‘D’ (mm)
63
75 – 200 100 – 150 150 – 200 200 – 250 250 – 300 300 – 400 400 – 500 500 – 600 600 – 700 700 – 800 800 – 900 900 – 1000 1000 – 1100 1100 – 1200 1200 – 1300 1300 – 1400 1400 – 1500 1500 – 1600 1600 – 1800 1800 – 2000
1 1 1 2 2 3 4 5
39
Octave Band Centre Frequency Hz) 125 250 500 1k 2k Attenuation dB 1 7 5 8 1 7 7 5 8 4 1 7 7 4 2 8 5 3 5 8 4 3 6 8 4 3 1 7 7 4 3 2 8 5 3 3 3 8 5 3 3 5 8 4 3 3 6 8 4 3 3 7 7 4 3 3 7 7 4 3 3 8 7 3 3 3 8 6 3 3 3 8 5 3 3 3 8 4 3 3 3 8 4 3 3 3
Octave Band Centre Frequency Hz) 125 250 500 1k 2k Attenuation dB 2 13 1 7 16 4 13 18 1 7 16 18 2 11 18 18 4 14 18 18 1 5 16 18 16 1 8 17 18 16 2 13 18 18 17 3 14 18 17 16 4 15 18 18 17 5 16 18 17 17 7 17 18 16 17 8 17 18 16 17 10 17 18 16 18 11 18 18 16 18 12 18 18 16 18 14 18 18 17 18 15 18 18 17 18 16 18 17 17 18
4k 7 4 4 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3
4k 18 18 18 16 17 17 17 17 18 18 18 18 18 18 18 18 18 18 18 18
CSR BRADFORD INSULATION
A C O U S T I C
D E S I G N
MEASURED SOUND ATTENUATION IN DUCTS. CSR Bradford Insulation has carried out extensive research to establish the real performance of duct liners in reducing noise levels. Tests have been carried out on Bradford Insulation 25mm and 50mm duct liners using different duct sizes and lengths of lined duct. Figures 33, 34 and 35 have been plotted from measurements of sound levels taken in standard sheetmetal ducts using 25mm duct liners. The graphs present a conservative guide to the performance of all Bradford Glasswool and Fibertex™ Rockwool duct liners at 25mm thickness. Four different lengths of lining are shown for each of three duct sizes.
G U I D E
FIG 34. SOUND ATTENUATION IN DUCT SIZE 406 x 813mm. 60
Insertion Loss (dB)
50
40
30
20
Bend
4.9m 3.7m 2.4m 1.2m
10
0
63
125
250
500
1000
2000
4000
Frequency (Hz)
FIG 35. SOUND ATTENUATION IN DUCT SIZE 508 x 610mm.
60
60
50
50
40
40
4.9m
30
3.7m 2.4m
20
63
125
250
500
1000
2000
30
20 Bend
Bend 1.2m
10
0
Insertion Loss (dB)
Insertion Loss (dB)
FIG 33. SOUND ATTENUATION IN DUCT SIZE 254 x 305mm.
4.9m 3.7m 2.4m 1.2m
10
0
4000
Frequency (Hz)
63
125
250
500
1000
2000
4000
Frequency (Hz)
TABLE 15. INSERTION LOSS CHARACTERISTICS OF FACED DUCTLINERS. (INTERNAL DUCT LINING) Insertion Loss (dB loss 600x600x4000 test duct) Product Facing Thickness Octave Band Centre Frequency (Hz) mm 63 125 250 500 1000 2000 4000 Bradford Glasswool BMF 50 1.4 4.6 16.8 53.2 51.6 32.4 24.4 ™ DUCTLINER THERMOFOIL 50 1.6 5.3 18.9 53.4 48.3 31.8 24.6 32 kg/m3 HD Perf. 23µm Melinex + THERMOFOIL™ 50 1.9 5.7 21.1 26.6 16.7 12.9 12.8 HD Perf. ACOUSTITUFF™ 50 2.5 4.7 21.3 46.8 39.3 23.3 17.4 ™ ULTRAPHON 50 2.0 5.0 20.9 51.5 46.6 30.3 27.5 Bradford Premium Ductliner ULTRATEL ACOUSTITUFF™ 50 – 4.9 14.2 39.0 37.0 22.4 18.6 48 kg/m3 Bradford FIBERTEX™ THERMOFOIL™ DUCTLINER HD Perf. 50 2.8 5.8 19.9 56.6 49.1 32.4 24.6 3 60 kg/m 40
CSR BRADFORD INSULATION
A C O U S T I C
D E S I G N
Research has also been carr ied out on sound attenuation characteristics of different facing materials used on duct liners. Insertion Loss measurements carried out in accordance with Australian Standard AS1277 : 1983 ‘Acoustics - Measurement Procedure For Ducted Silences’ demonstrate the effect of typical facing materials on the acoustic performance of Bradford Glasswool and FIBERTEX™ duct liners, as shown in Table 15.
G U I D E
Constraints accuracy = ± 10% frequency range, 250 to 2000Hz α ≤ 0.8 for circular ducts, Diameter > 0.15m for rectangular ducts, width or height ≤ 900mm and width
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