AU2016100769A4 - IMPROVED SOUND TRANSMISSION LOSS BOARD The improved acoustically resistant composite board - Google Patents

Abstract

ON This invention relates to a single or multilayer sound transmission board for use in construction of the partition walls, ceilings or floors of buildings and as soundproof panel for aircraft engines or any place where noise reduction is required. A multilayer composite board (10) comprises layers (11) whose thickness determined by convergence of two functional dependences of a weighted sound reduction index Rx or sum of Rx and spectrum adaptation term Ctr from the surface mass and the critical frequency, wherein the critical frequency of the layer equals to or exceeds the threshold of 4000 Hz. The layers of the multilayer board are lightly fixed together mechanically by screws or by gaskets or suitable adhesive materials, providing layer by layer sound wave propagation through the board. 25 25 26 25 Figure 2

Description

IMPROVED SOUND TRANSMISSION LOSS BOARD

TECHNICAL FIELD

[0001] This invention relates to a single or multilayer sound transmission board for use in construction of the partition walls, ceilings or floors of buildings and as soundproof panel for aircraft engines or any place where noise reduction is required.

BACKGROUND

[0002] A very important problem of acoustic performance is an attainment of acceptable airborne sound transmission through constructive elements of different objects.

[0003] The invention is described in particular application for the building industry though it can be widely used in many fields where noise reduction is required. Building elements especially walls, ceilings, windows and doors have to satisfy the sound insulation requirements. Walls also make significant contribution to reduction of noise proliferation in residential and industrial buildings and areas. Constructions of wall lining boards and method of their production have significant impact on sound transmission loss.

[0004] State standards of many countries establish sound insulation rating of walls. For example, to comply with Building Code of Australia (BCA) walls must have an Rw + Ctr (airborne) not less than 50 if they separate sole-occupancy units. Rw is a weighted sound reduction index and Ctr is a spectrum adaptation term.

[0005] The most widely used construction of Partition Wall Systems is Single Stud Wall Construction, based on steel or wooden stud s with insulation filling and linings of plasterboards. However this method of construction cannot comply with the BCA Rating of Sound Insulation, because of the acoustic characteristics of the mainstream commercially available lining boards that cannot achieve required sound transmission loss.

[0006] To comply with BCA builders usually use Staggered Stud Walls, Double Stud Walls or apply Resilient Mounts and Furring Channels. These methods significantly increase cost of construction as well as increase thickness of walls thus reducing internal space of the buildings.

[0007] Acoustica’s QuietWave® wall system comprises 64 mm staggered studs in a 92 mm track with 50 mm thick insulation, two 13 mm thick plasterboard on both stud sides and two 1.2 mm thick QuietWave® visco-elastic membrane between each pair of plasterboards and achieves a compliance with BCA due to staggered studs and viscose-elastic membranes.

[0008] Patent #1998098256 “Acoustic wall” describes construction of wall including a supporting panel, a cavity, and at least one outer surface. The wall contents a reinforced masonry panel having a substantially unitary structure and a cavity defined by the space between the supporting panel and an outer surface. The cavity is wide enough to include an insulation material to increase a sound transmission loss. The outer surface defining the cavity is a single layer of plasterboard.

[0009] Patent application EP 1225126 A2 "Acoustic board with an improved composite structure” describes an acoustic board with improved composite structure, suitable for reducing sound transmission, in which a upper layer that consists out of fabric, with high sensitivity to sound velocity, and the supporting sheet with a preset porosity is combined with one or more intermediate honeycomb layers separated by a porous septum with a given resistance, and closed by a lower layer for the final covering of the structure.

[0010] The invention “Acoustical wall panels” US6698543 B2 relates to very structurally stable acoustical panels that may be of significant size and can be applied directly to the wall, or describes actually form the wall panel for a divider, to function dually as a divider, but more importantly, to dampen sound, and lessen the noise reversal of the ambient area.

[0011] United States Patent US 3621934 describes a sound-absorbing wall covering for regulating sound-absorption in a room is made in long sheets or rolls of a flexible laminate consisting of a flexible decorative skin such as vinyl adhered to a soft, porous backing material, preferably a foam polymeric material. Certain areas of the skin contain many very small perforations while the adjoining areas of the skin are imperforate. After installation, a room may be fine-tuned for sound by closing some of the holes in the perforated area.

[0012] The invention 2009238349 describes a composite board comprising: “A first and seventh layer of a first thermoplastic material; a second and sixth layer of metal; a third and fifth layer of a second thermoplastic material; and a fourth layer made from a combination of thermoplastic material and a reinforcing filling agent, the fourth layer including at least one hollow void”.

[0013] Technical solutions of increasing the sound transmission loss (STL) via boards or walls described above achieved by a variety of designs. In order to increase the reduction of sound transmission wall constructions include a soundabsorbing wall covering or board having an improved composite structure or a supporting panel and a cavity or elastic membrane between each pair of plasterboards. Sometimes just many layers of different materials are used.

[0014] The behavior of board or partition wall under impact of sound waves can be described by three regions of frequency (Ben H. Sharp “Prediction Methods for the Sound Transmission Loss of Building Structures”): (i) the stiffness-controlled region, including the frequencies where resonance occurs; (ii) the mass-controlled region described Mass Low; and (iii) the wave-coincidence controlled region.

[0015] In all shown above inventions the frequency dependency of sound transmission loss is determined by chosen construction of boards and walls where each of three frequency regions are defined and fixed. In this case the minimum transmission loss takes place in both ranges the resonance frequency and the critical (coincidence) frequency.

[0016] The object of this invention is the creation of single and multilayers boards with increased transmission sound loss compared to the already known boards by design of optimal thickness and surface mass of board layer. In this invention surface mass and thickness at least one layer of the board determined by selecting the critical frequency at which STL indexes Rx and Rx + Ctr achieves the maximal value.

[0017] The present invention will ensure that the most simple Single Stud Wall Constructions could comply with the requirements of BCA and still remain at low cost with simplified design and decreased thickness of the walls. In other words, using these innovative boards will allow reaching a predetermined value of transmission sound loss, and at the same time to reduce the overall surface density of the boards, and overall weight and thickness of the wall.

SUMMARY OF INVENTION

TECHNICAL PROBLEM

[0018] Currently BCA sound requirements are achieved at the expense of complicating the structure and increase of the weight and the wall thickness and accordingly the cost of materials and labor. To improve soundproofing of a board by 6 dB in mass-controlled region it is necessary to either double the thickness of the board or use material that has twice more density. Majority of currently available boards and walls, which could provide builders with increased sound transmission loss are still bulky and expensive. The further improvement of the design of partition walls and achievement of required transmission loss and at the same time reducing the overall surface density of the boards, overall weight and thickness of the wall is an urgent task.

SOLUTION TO PROBLEM

[0019] The purpose of this invention is to design a board with increased sound transmission loss compared to the already known boards. Achieving this goal will ensure that the simplest Single Stud Wall Constructions could comply meet the requirements of BCA and still remain at low cost, simplified design and decreased thickness of the wall.

[0020] Value of sound transmission loss R through boards or walls is described by Mass Low as: R=20 log (fm) - 47 dB, Equation 1

Where: f - frequency (Hz), m - mass per unit area (kg/m2).

[0021] The Mass Law is efficiency running into the frequency diapason where sound transmission loss is provided about 6dB for each doubling of mass per unit area. This frequency diapason is limited by resonance frequency {fr) for low frequencies and coincidence frequency (fcr) for high frequencies. The wider a frequency diapason where Mass Low is efficiency running the more wall transmission sound loss. An extension of frequency diapason could be achieved by shifting fr towards lower frequencies and fcr to higher frequencies. To reach this goal it is necessary to increase the region of frequencies between fr and fcr. Hence fr should be shifted to lower frequencies, and fcr to higher frequencies.

[0022] For any building material with a given density p and Young's modulus E there is a dependency fcr of a layer thickness, which expressed as below.

Equation 2 or Equation 3

Where: d - layer thickness, m; K - a constant = 0.556; C - speed of sound in air, m/sec; fcr - critical frequency, Hz; p - density, kg/m3; E - Young's modulus, Pa.

[0023] By changing the thickness of a board fcr could be shifted to higher frequencies. As result the range of frequencies where the Mass Law is effective will be increased.

[0024] Considering the fact that physical characteristics of the board material such as thickness, critical frequency, surface density and elasticity define the value of STL it is easy to assume that there is an optimum layer thickness at which the STL is increased. Innovative research suggests the existence of the optimum layer thickness which provides boards with the increased value of STL.

[0025] Unfortunately it is not possible to calculate the optimal thickness and surface mass by using traditional methods. The complexity of it lies in the multifunctional dependency of the characteristics of the material used, such as surface mass, thickness, density, elasticity, board size and a specified weighted sound reduction index Rx and spectrum adaptation term Ctr.

[0026] This is due to the fact that to increase the STL need to increase the surface mass and respectively the thickness or the density of the material used, however the critical frequency is automatically shifted toward lower frequencies, it consequently reduces the STL. For example to increase the STL by 6 dB it is necessary to increase the surface mass by two times, by 12 dB - 4 times, by 18 dB - 8 times, etc. respectively, but the critical frequency in this case is reduced which lowers a STL.

[0027] STL is inherence in two opposing functional dependencies from mass and critical frequency which achieve the point of convergence these two functions (the point of optimal impact) where critical frequency and surface mass have an optimal effect on the value of ST. This point is achieved by determine the thickness and surface mass by selecting the critical frequency at which a weighted sound reduction index Rx or the sum of Rx and spectrum adaptation term Ctr reaches optimal value. In this case each layer has a thickness at which the critical frequency of the layer equals to or exceeds the threshold of 4000 Hz. The critical frequency is variable that depends on the type of a layer material, but the critical frequency of the whole board and each layer can't be less than 4000 Hz.

[0028] At this point the indexes Rw or Rw + Ctr reach the optimal value. The characteristic of the optimal value is that increase in mass from this point leads to unproductive consumption of material, and increase of the critical frequency leads to necessity of overly thin layers for multilayer boards, which is also inefficient. Hence, there is an optimal thickness and surface mass for a single layer or multilayer board at which STL has the optimal value. Calculations, confirmed by the test results suggest that index Rx or sum of Rx and spectrum adaptation term Ctr achieve the optimal value at critical frequency equals to or exceeding the threshold of 4000 Hz.

[0029] Multilayer acoustic resistance board that consists out of layers of optimum thickness will have the optimal STL in terms of saving material, decrease weight and thickness of the partition walls... This assumption is true for any building material used for board design. The optimal layer thickness (OLT) at which the STL of the whole board reaches its optimal value is essential for each building material. The number of layers of a composite board is calculated with considerations of the desired STL value for the board as well as the number of boards for a whole wall construction. To reach optimal STL the board has to be made as a multilayer structure with optimum thickness of layers. The total thickness of the board should be chosen from the considerations of required STL.

[0030] The board consisting of layers of OLT will have the increased STL for any chosen type of materials regardless of its surface density. For any value of the density of the selected material there is its own unique optimum thickness of a layer and the surface mass of the layer where the composite board has an increased value of STL. The number of layers inside the board is defined by the ratio of surface density of the board and the surface density of the layer.

[0031] A lot of plasterboards having thickness of 10mm, 13mm and 16mm do not conform to the optimal thickness in terms of the optimum of STL value. Only a part of the layer thickness which is optimal affects STL. The remaining part of the layer is impractical because of the low efficiency. Making soundproof single or multilayers boards with optimum layer thickness provides building industry with saving up to 25% material.

[0032] In order to confirm and find out the OLT a series of predicted tests had been done on the same thickness boards containing layers of different thicknesses. The result of multiplication of the number of layers by their thickness was always equal to the board thickness. Tests of the most acceptable lining building boards used in the construction industry were conducted on using of INSUL Marshall Day Acoustics Ltd software that can predict the performance of Rw and Ctr for building materials. Tests were made for usual Single Stud Wall Constructions with lining boards which differed only by the number and thicknesses of layers.

[0033] The test results are shown in tables 1-4 below. TABLE 1 CSR Aquachek board, lining both sides of steel stud 76, p = 800kg/m3, E = 3.138GPa; Fcm = 26200 Hz kg/m2, insulation: 50 mm, 11 kg/m3 Bradford Gold R1.8 infill, board size: 2.7x 4 m, mass: 41.6 kg/m2.

TABLE 2

Boral Standard boards, lining both sides of steel stud 76, p = 650kg/m3, E =1,683GPa, Fcm = 26200 Hz kg/m2, insulation: 50 mm, 11 kg/m3 Bradford Gold R1.8 infill, board size: 2.7x 4 m, mass: 33.8 kg/m2.

TABLE 3

MgO board (magnesium oxide), lining both sides of steel stud 76, p=1105 kg/m3, E = 5.9 GPa, Fcm =31000 Hz kg/m2, insulation: 50 mm, 11 kg/m3 Bradford Gold R1.8 infill, board size: 2.7x 4 m, mass: 53.0 kg/m2.

TABLE 4

Soundcheck boards, lining both sides of steel stud 76, p = 1000kg/m3, E = 6.129GPa, insulation: 50 mm,11 kg/m3 Bradford Gold R1.8 infill, board size: 2.7x 4 m, mass: 52.0 kg/m2 (for 26 mm) and 64.0 kg/m2 (for 32 mm).

[0034] Comparative results of Rw / Rw + Ctr for walls with single-layer and multilayer boards with optimum of layer thickness are shown in table 5. TABLE 5

Comparative results of Rw / Rw + Ctr for walls with single-layer and multilayer boards with optimum of layer thickness.

[0035] During the first stage, the tests were conducted to compare sound characteristics of traditional single layer and multilayer boards of the same thickness. The innovative boards were compared versus well- known in building industry plasterboards such as: Boral Soundstop, CSR Fyrchek, CSR Soundcheck Gypsum plasterboard and Lightweight concrete.

[0036] To confirm industrial applicability and embodiments of present invention tests were conducted for a wall construction shown in Figure 2. On this stage Rw and Ctr of walls were measured for both types of construction to compare the same thickness of wall construction using two traditional single layer boards and offered composite multilayer boards. Two single lining boards were chosen from most commonly used brands in building industry. Both types of boards have been used as lining board on steel studs.

ADVANTAGEOUS EFFECTS OF THE PRESENT INVENTION

[0037] For the most of the building materials used as multilayer lining board for partition walls there is the optimal thickness of the layer at which sound transmission loss of a board consisting of these layers reaches increased value. Test results represented in Figures 4-11 definitely confirmed the presence and the possibility of determining the optimal thickness of the layer at which sound transmission losses reach greater magnitude...

[0038] It is quite evident that Rw of composite boards exceeds Rw of single boards the same thickness and surface mass by 3-5 units. This corresponds to reduced intensity of sound level by 5-6 dB. Using innovative composite boards in the wall linings will reduce the sound level roughly by half.

[0039] In addition, a board consisting out of several layers has significantly greater sound STL than a single-layer board of the same thickness made by traditional method. Also additional increase of STL of composite board could be achieved by alternative arrangements of layers with the different densities.

[0040] It is necessary to note that a lot of plasterboards used in building industries have thickness of 10mm, 13mm and 16mm, that does not conform to the optimal thickness in terms of the optimum of STL value.

[0041] The Single Stud Wall Constructions lined by composite boards with optimal layer thickness compared with lined by single-layers boards have Rw increased up to 28% and Rw + Ctr up to 20%.

[0042] A composite board design provides additional increase of STL due to the inherent lower stiffness as compared with single-layered board. Reducing the stiffness provides a shift of fr towards lower frequencies, and thus extends the frequency range where the Mass Low law is observed.

[0043] Results of the predicting tests confirmed that walls with innovative composite boards in comparison with the well- known and used in building industry boards possess : - Greater transmission sound loss Rw/Rw+Ctr, less weight and wall thickness, and cheaper (Table 6). - Addition of extra living space (+m2) due to lower thickness if innovative composite walls are using instead traditional walls. (Table7). TABLE 6 comparative assessments of CSR Walls and Innovative Single Stud Walls.

TABLE 7

Additional living space (+m2) that could be having if Innovative Composite Walls (thickness 124 mm, weight 38.4 kg/m2) are using instead traditional walls.

[0044] Advantage of Invention lies in the fact that: - Definitely confirmed the presence and possibility of determining the optimal thickness of the layer at which sound transmission losses reach higher value.

Confirmed an existence of the optimal thickness of the layer at which sound transmission loss of a board consisting of these layers reach greater magnitude value for the most of building materials used single as well multilayer lining boards for partition walls. - Established method how to determine and identify the optimal thickness of the layer of composite board for increased sound transmission losses. - The Single Stud Wall Constructions lined by composite boards with the optimum layer thickness compared with lined by traditional single-layers boards have Rw increased up to 28% and Rw + Ctr up to 20%. - Rw of composite boards exceeds Rw of single boards by 3-5 units. This corresponds to reduced intensity of sound level by 5-6 dB. Lining of walls by composite boards correspondingly allows reducing the sound penetration by approximately 50%. - Innovative boards provide increased sound transmission loss at reduced weight, wall thickness and cost. - Using innovative boards in building industry instead traditional walls can provide industrial and residential buildings with additional living space (+m2). - Currently using a line-up of thickness 10,13,16 mm for most soundproof boards of different materials, regardless of their density, elasticity and other characteristics is practically undesirable. Only a part of the layer thickness which is optimal affects STL. The remaining part of the layer is impractical because of the low efficiency. Making soundproof single or multilayers boards with optimum layer thickness will save up to 25% material.

DESCRIPTION OF EMBODIMENTS

[0045] Embodiments of a composite board and a partition wall in accordance with the present invention will be described by way of example only with reference to the accompanying drawings. Figure 1 is a composite board with gasket material between layers. Figure 2 is an embodiment of single metal stud partition wall including the innovative composite boards. Figure 3 is a view of the composite board locations into partition wall. Figures 4 -11 depict test results of embodiment composite board (Fig.4-8) and walls (Fig.9-11) in competition with traditional boards and walls.

[00461] Referring to Figures 1, composite board 10 containing layers 11 is shown with only three layers. Every layer has the optimal value of surface mass and thickness. Layers of composite board are lightly fixed together mechanically by screw or with using gasket or suitable adhesive material 12. Any chosen a way of fixing must ensure a layering passage the sound waves through the thickness of the board. As gasket material can be a paper or the like.

[0047] Figure 2 is perspective view of a Single Stud Wall 20. It is the embodiment of the part of partition wall area of 6.48 m2, size of wall is 3600 x 1800 x 123 mm. Shown wall contents three 75mm Steel Stud 25, 70.0 mm Bradford Gold R1.8 insulation 26 and four assemblies of composite boards. Every board comprises three layers of magnesium oxide material.

[0048] All board assemblies represented in Figure 3 have the same area. First of four assemblies consists out of 9 full size composite boards 1200x600x12 mm. In the second assembly the boards are shifted by one-fourth of the length and width of the full board size. Accordingly for third and fourth assemblies the boards are shifted by half and three-fourths of board size in both directions. Positioning of the boards location in every assembly allows avoiding an overlap of the liner joints between boards. As the result the assembly 30 prevents the passage of the sound waves 31 along a straight line through the matching joints of the boards.

[0049] Figures 4-8 show a functional dependency of Sound Reduction Index from the sound frequency for traditional single-layer boards (1) and embodiment of multilayer composite boards (2) with the same material and board thicknesses.

[0050] Figure 4 represents Sound Transmission Loss of a single-layer board (1): 1 x 20.0 mm Boral Soundstop plasterboard, measurement result: Rw = 30, Ctr = -3 and composite board (2): 5 x 4.0 mm Boral Soundstop plasterboard, measurement result: Rw = 34, Ctr = -4 with the same board thicknesses of 20 mm.

[0051] Figure 5 represents Sound Transmission Loss of a single-layer board (1): 1 x 16.0 mm CSR Fyrchek plasterboard, measurement result: Rw =29, Ctr= -3 and composite board (2): 4 x 4.0 mm CSR Fyrchek plasterboard, measurement result: Rw = 32, Ctr= -4 with the same board thicknesses of 16 mm.

[0052] Figure 6 represents Sound Transmission Loss of a single-layer board (1): x 16.0 mm CSR Soundchek plasterboard, measurement result: Rw = 29, Ctr= -2 and composite board (2): 4 x 4.0 mm CSR Soundchek plasterboard, measurement result: Rw=34, Ctr= -4 with the same board thicknesses of 16 mm.

[0053] Figure 7 represents Sound Transmission Loss of a single-layer board (1): 1 x 16.0 mm Gypsum plasterboard, measurement result: Rw= 28, Ct r= -2 and composite board (2): 4 x 4.0 mm Gypsum plasterboard, measurement result: Rw =31, Ctr = - 4 with the same board thicknesses of 16 mm.

[0054] Figure 8 represents Sound Transmission Loss of a single-layer board (1): 1 x 100.0 mm Lightweight concrete, measurement result: Rw = 44, Ctr= -3 and composite board (2): 5 x 20.0 mm Lightweight concrete, measurement result: Rw = 49, Ctr= -2 with the same board thicknesses of 100 mm.

[0055] Figures 9-11 show Sound Transmission Loss of walls containing on both sides of the stud two single traditional plasterboards (1) and embodiment walls containing the multilayer boards (2) with the same material and wall thickness.

[0056] Figure 9 represents Sound Transmission Loss of walls containing the single boards (1) and composite multilayer boards (2) of CSR Soundcheck plasterboards. Common characteristics of Walls: Lining material of CSR Soundcheck plasterboard, density = 1000 kg/m3, Young Modulus= 6.129 Gpa, surface density = 48.0 kg/m2. Insulation material is of 70.0 mm Bradford Gold R1.8. Wall thickness = 123mm.

Steel Stud Wall 1: 2x12.0 mm CSR Soundcheck plasterboard +75 Steel Stud with insulation material + 2 x 12.0 mm CSR Soundcheck plasterboard. Measurement result: Rw = 56, Ctr = - 6.

Steel Stud Wall 2: 8 x 3.0 mm CSR Soundcheck plasterboard +75 Steel Stud with insulation material + 8 x 3.0 mm CSR Soundcheck plasterboard. Measurement result: Rw= 61, Ctr = -10.

[0057] Figure I0 represents Sound Transmission Loss of walls containing the single boards (1) and composite multilayer boards (2) of plasterboards of MgO (magnesium oxide).

Common characteristics of Walls: Lining material of MgO board, density = 1105 kg/m3, Young Modulus= 5.907 Gpa, surface density = 53.0kg/m2. Insulation material is of 70.0 mm Bradford Gold R1.8. Wall thickness = 123mm.

Steel Stud Wall 1: 2 x 12.0 mm MgO board + 75 Steel Stud with insulation material + 2 x 12.0 mm MgO board. Measurement result: Rw=57, Rw+Ctr =51.

Steel Stud Wall 2: 6 x 4.0 mm MgO board + 75 Steel Stud with insulation material + 6 x 4.0 mm MgO Board. Measurement result: Rw=63, Rw+Ctr = 53.

[0058] Figure 11 represents Sound Transmission Loss of walls containing the single boards (1) and composite multilayer boards (2) of CSR Aquacheck plasterboards. Common characteristics of Walls: CSR Aquacheck plasterboard, density= 800 kg/m3, Young Modulus= 3.138 Gpa, surface density = 51,2kg/m2. Insulation material is of 70.0 mm Bradford Gold R1.8. Wall thickness = 139mm.

Steel Stud Wall 1: 2x16.0 mm CSR Aquacheck plasterboard +75 Steel Stud with insulation material + 2 x 16.0 mm CSR Aquacheck plasterboard. Measurement result: Rw= 56, Ctr=-5.

Steel stud Wall 2: 8 x 4.0 mm CSR Aquacheck plasterboard + 75 Steel Stud with insulation material + 8 x 4.0 mm CSR Aquacheck plasterboard. Measurement result: Rw = 62, Ctr=-10.

Claims (5)

1. The single or multilayer sound transmission loss board comprising at least one layer whose thickness determined by convergence of two functional dependences of a weighted sound reduction index Rx or sum of Rx and spectrum adaptation term Ctr from the surface mass and the critical frequency , wherein critical frequency equals to or exceeds the threshold of 4000 Hz.

2. The ratio between a surface mass and a critical frequency of layer according to claim 1 is variable in dependence to density, elasticity of using materials as well as size of whole board and ensures maximal impact on the sound transmission loss .

3. The number of layers in the multilayer board according to claim 1 is defined by the ratio of specified surface mass of the board and the surface mass of a layer which provides the board with the optimal value of Rw or Rw +Ctr.

4. The layers of the composite board according to claim 1 are lightly fixed together mechanically by screws or by gaskets or suitable adhesive materials, providing layer by layer sound wave propagation through the board.

5. Composite boards according to claim 1 placed inside of the partition walls are installed in assemblies therefore positioning of the boards in every assembly allow avoiding an overlap of the liner joints between boards.