AU2005233209B2 - Construction elements - Google Patents

Description

WO 2005/100709 PC'TAU2005/000520 SOUND TRANSMISSION REDUCING CONSTRUCTION ELEMENTS Field of the Invention This invention relates to construction elements suitable for use in constructing internal or external walls, ceilings, roofs, floors and the like where reduction of transmission of sound from one side to another is important.

Background to the invention The sound transmission loss of a wall partition, ceiling, roofs or floor are determined by physical factors such as mass and stiffess. A complex interplay of factors works to prevent or allow the transmission of sound through surfaces. In a double layer assembly, such as plasterboard on wood or metal framing, the depth of air spaces, the presence or absence of sound absorbing material, and the degree of mechanical coupling between layers critically affect sound transmission losses.

The mass per unit area of a material is the most important factor in controlling the transmission of sound through the material The so-called mass law is worth repeating here, as it applies to most materials at most frequencies: TL= 20 logo (mf) 48.

where: TL transmission loss (dB) m, mass per unit area (kg/m 2 f= frequency of the sound (Hz) Stiffiess of the material is another factor which influences TL. Stiffer materials exhibit "coincidence dips" which are not explained by the above mass law. The coincidence or critical frequency is shown by: WO 2005/100709 PCT/AU2005/000520 f, A/t where: A is a constant for a material t is the thickness of the material (irn) There are other factors in wall, roof, ceiling floor design such as the mass-airmass resonance, which also affect transmission loss at different frequencies.

Generally, relying only on the mass law to achieve a specific TL results in a thick wall, ceiling or floor construction, which reduces usable floor area and ceiling height in an apartment dwelling. Attempts to avoid those coincidence dips noted above appear only to increase transmission loss slightly, if at alL Generally only very expensive and labour intensive solutions give an acceptable transmission loss. Building reglations are becoming more strict while more apartment blocks are being constructed, with cost being a preeminent factor.

The Sound Transmission Loss of a dividing structure separating two spaces varies with frequency, If the structure has a degree of stiffness, incident acoustic energy causes the structure to vibrate which re-radiates the acoustic energy on the other side of the structure. Low frequency re-radiation is mainly controlled by the structure stiffness, At about an octave above the lowest resonance frequency of the barrier, the mass of the structure takes over control of the re-radiation and dominates the sound reduction performance, and the mass law (above) indicates that doubling the mass of the structure increases the structure's noise attenuation performance by approximately 6dB.

High frequency incident acoustic energy causes ripple-, or bending-waves of the surfaces of the structure. Unlike compression waves, the velocity of bending waves increases with frequency. Every 'stiff panel construction' has a critical or coincidence frequency which considerably reduces the Sound Transmission Loss of structural panel construction.

PCT/AU2005/000520 Received 23 June 2005 P -WLX.WiCSX-NW Sp 4 'HlISti) Tn RC Qtcfx PCThi, J3SSIS -3- A common coincidence frequency occurs between 1000 4000 Hz and is caused by the bending wave speed in the material equaling the speed of sound in the medium surrounding the panel (in this case air). in this frequency range the waves coincide and reinforce each other in phase, greatly reducing the noise reduction performance of the panel at approximately the critical frequency.

The present invention seeks to ameliorate one or more of the abovementioned disadvantages of known methods of increasing TL such as higher cost, mass reduced available space.

Summary of the invention According to one aspect of the present invention there is provided an acoustic laminate suitable for use in wall, floor and ceiling assemblies and other dividing structure assemblies, the laminate including: a flat construction panel; a viscoelastic acoustic barrier material in the form of discrete viscoelastic acoustic portions spaced across a face of the construction panel, the viscoelastic material affixed to one or more panel faces of the construction panel.

Preferably the construction panel is plasterboard, medium-density fibreboard, plywood, fibre-cement sheeting or timber.

Throughout this specification, "construction panel" is to be taken to include those panels constructed from fibreglass, composites such as carbon fibre, sheets used in domestic construction of walls, glass-reinforced plastics, plasterboard, medium-density fibreboard, plywood, fibre-cement sheeting or timber. Excluded from the definition are steel sheets, aluminium, C-beams, I-beams, structural supports and the like. Furthermore, "panel" is to be taken to include a panel having contours or curvature such as for example, sinusoidal, or of course completely flat.

Amended Sheet

IPEAAU

WO 2005/100709 PC 17AU2005/000520 -4- Preferably the construction panel is affixed to the viscoelastic acoustic barrier layer by adhesive.

Preferably the viscoelastic acoustic barrier is poured onto the construction panel and cures on the panel, bonding to the panel during curing.

Preferably the viscoelastic acoustic barrier layer is affixed to the construction panel in strips along an axis parallel to respective panel faces.

Preferably a matrix of viscoelastic pads are affixed to the construction panel across respective panel faces.

Preferably a second layer of construction panel is affixed to an outer face of the viscoelastic barrier or strips or pads in order to provide a three-layer laminate, for captive-, or constrained-layer damping-type effect.

Preferably the viscoelastic acoustic barrier layer has a density within a range of 1000 kg/m' to 3000kg/nm3 Preferably the viscoelastic acoustic barrier layer has a surface density of approximately kg/m 2 Preferably the viscoelastic oustic tic barrier layer has a thickness below 6mm.

Preferably the viscoelastic acoustic barrier layer has a thickness of 1.7mm.

Preferably the viscoelastic acoustic barrier layer has a density is 1470kg/m 3 Preferably the viscoelastic acoustic barrier layer is a polymeric elastomer impregnated with material which in preferred forms is a particulate material, WO 2005/100709 PCT/AU2005/000520 Preferably the filler material is calcium carbonate, Preferably the viscoelastic acoustic barrier layer is faced on one side with a nonwoven polyester of thickness approximately 0.05rmm Preferably the viscoelastic acoustic barrier layer is faced on the other side of the viscoelastic barrier or strips or pads by an alumninmn film reinforced with polyester as a water barrier.

Preferably the viscoelastic acoustic barrier layer has a Young's Modulus of less than 344kPa.

Preferably the acoustic laminate is incorporated into a wall structure utilising staggered studs and a cavity filled with polyester batts or other sound absorptive material.

Preferably the viscoelastic acoustic barrier layer is in the form of a composition which includes water, gelatine, glycerine and a filler material.

Preferably the composition includes: 5 40 wt% water 30 wt% gelatine 40 wt% glycerine; and 60 wt% filler material.

Preferably the composition includes 1 to 15 wt% of a group 1 metal chloride such as for example calcium chloride or magnesium chloride.

Preferably the composition includes 2 to 10 wt% magnesium chloride.

Preferably the composition futher includes 0.5 to 7 wt% starch or gluten.

WO 2005/100709 PCTAU2005/000520 Preferably the starch is provided from the addition of cornflour to the composition.

Preferably the filler material is a non-reactive material with a high density.

Preferably the density is greater than I gi/cm 3 Preferably the density of the filler material is approximately 2.0 to 3.0 g/cm.

Preferably the filler material is chosen from any non-reactive material with a high density such as for example barium sulphate or KAOLIN, Preferably the composition includes: 25 wt% water 20 wt% gelatine 10 25 wt% glycerine; 60 wt% filler material; 1 10 wt% magnesium chloride; and 3 wt% starch; Preferably the composition further includes constituents such as for example ethylene and/or propylene glycols; polyvinyl alcohols; deodorisers; ant i -oxidants and/or fungicides Preferably a wall construction is provided, incorporating additional layers of construction panel are provided, affixed to staggered studs.

Preferably the a wall construction is provided, which includes absorbent material in the form of polyester batts.

Description of Preferred Embodiment WO 2005/100709 PCT/A112005/000520 In order to enable a clearer understanding of the invention, drawings illustrating example embodiments are attached, and in those drawings: Figure 1 is a schematic representation of a reference wall (typical of current construction method) used in testing to give a benchmark for measured results; Figure 2 is a schematic representation of a wall constructed in part using components of a preferred embodiment of the present invention; Figure 3 is a graph showing results of benchmark transmission loss testing of the reference wall shown in Figure 1 (an STC60 curve is superposed on the test results); Figure 4 is a graph showing results of transmission loss testing of the wall shown in Figure 2 (an STC63 curve is superposed on the test results); and Figure 5 is a graph showing graphs in Figures 3 and 4 superposed on similar axes; Figure 6 is a graph showing expected coincidence effects of prior art stiff panels; Figure 7 shows Transmission Loss (TL) test results of a reference wall of the prior art displaying coincidence dip effects; Figure 8 shows TL test results of a wall treated with preferred embodiments of the present invention, showing the much reduced coincidence dips, if detectable at all; Figure 9 shows TL test results of a wall treated with another preferred embodiment of the present invention ie spaced viscoelastic strips (an STC curve is superposed on the results, and corrected data is also shown in broken line); Figure 10 shows the composition of the reference wall tested in Figure 9; WO 2005/100709 PCT/AU205/000520 -8- Figure 11 shows TL test results of a wall treated with yet another preferred embodiment of the present invention ie viscoelastic pads spaced on a matrix (an STC curve is superposed on the results, and corrected data is also shown in broken line); Figure 12 shows the composition of the reference wall tested in Figure 11.

Referring to Figure 1 there is shown a reference wall generally indicated at 1. The reference wall is a composite wall consisting of two layers of 13mm thick fire rated plasterboard directly secured to 64mm, 0,75mm steel studs on one side. The wall is wholly repeated in mirror image about a centreline extending between the studs, with a gap separating the studs. An infill cavity insulation of 50mm glasswool 11kg/m 3 is located between one set of the steel studs.

A composite wall assembly utilising a preferred embodiment of the present invention is shown at Figure 2 item 20. The composite wall assembly includes a laminate assembly 12 including a layer of 13mmn high density plasterboard 14, adhered to one face of a centre lamina of 2.5kg loaded polymeric elastomer shown at 16, which is itself on its other side adhered to a 13mm standard density plasterboard 18. The laminate assembly 12 is affixed to 64mm, 0.6mm thick steel studs 22. A cavity 24 is provided, filled on one side with 50mm thick 48kg/im polyester insulation batts 26. On the other side of the cavity 24, studs 23 are provided, the studs 23 being staggered from studs 22. Affixed to the studs 23 is a laminate assembly 13, a mirror image of the laminate assembly 12.

LExerimental data utilisin preferred embodiments of the resent invention A reference wall and a composite wall, each in accordance with the above descriptions and Figures were constructed, and their sound transmission performance was tested. A 1-.OdB correction was applied during testing to the reference wall to align its glasswool performance with that of the composite wall. The composite wall utilised 48kg/m 3 and the reference wall used 1 Ikg/m' glasswool to infill one side of the cavity.

WO 2005/100709 PCT/AU2005/000520 Description 1/3 Octave Band Centre Frequency 100 125 160 200 250 315 400 500 630 Composite Wall 45 45 48 50 53 1 56 57 59 61 Reference Wall 37 42 44 47 51 51 55 58 61 Improvement 8 3 4 3 2 5 2 0 Table 1: Comparison Results of the Testing Conducted, Description 1/3 Octave Band Centre Frequency 800 1000 1250 1600 2000 2500 3150 4000 5000 Composite Wall 64 66 67 67 68 70 73 77 78 Reference Wall 62 64 66 68 64 61 64 64 64 Inprovement 2 2 1 -1 3 9 3 14 L Figures 3, 4 and 5 show the tabulated results graphically.

The table above and the graphs show the improvement in acoustic performance that occurs in the nominated frequency regions due to the addition of a lamina of loaded polymeric elastomer 16, surface density of 2.5kg/m 2 between a sheet of 13mm highdensity plasterboard 14 and a sheet of 13mm normal density plasterboard 18, Normal experience teaches that a very small improvement of performance in a so-called coincidence dip frequency region (2500Hz in this case) can occur where plasterboards of differing densities are adhered together. This improvement is nonnally only of the order of 2 to 3dB. However, the performance gain in this experiment for the composite wall assenmbly 20 is 9dB, with significant gains in performance occurring above this frequency.

The combined graph (Figure 5) and table shows an improvement in the frequency regions of 100Hz to 400Hz and from 2000Hz to 5000Hz.

WO 2005/100709 W01J0PCT!AU20051000520 When the concept of Acoustic Performance Index is applied to the composite wall assembly 20 (Figure 2) the score is extremely high. Acoustic Performance Index takes into account the cost of the wall compared to its acoustic performance and to the thickness of the wall and the floor space cost. Thickness is a very important consideration as floor space in a typical apartment is AU$6000 per square metre. The composite wall assembly is only 206mm wide and has an acoustic performance that can only be matched by expensive wall systems which are 280nun wide or more. The composite wall system has a high Acoustic Performance Index of R, greater than or equal to The combination of the construction panel and viscoelastic barrier provide an unexpected synergy. It would be expected that adding a very thin layer of dense material would only provide a small benefit according to the mass law. For example, at 1250 Hz, increasing the mass by 6kgm 2 (as we have shown above in the testing) we are expected to produce a gainn n transmission loss of 2dB (see Also Figure However, in the testing above, at that frequency, we see TL gain of 2dB.

Furthermore, the expected coincidence dip does not eventuate. We would have expected that the change in stiffness would have given us a change in transmission loss of 1.6dB at 2500Hz. However, we demonstrated at that frequency, a change of 18dB.

By affixing viscoelastic material to construction panel in the forn of plasterboard the panel resonance at low frequencies was reduced and stiff panel 'Coincidence effects' were greatly reduced at higher frequencies, especially the frequencies at which the ear is most sensitive.

Other embodiments have been tested: In one embodiment, strips ofviscoelastic material covering 25 50% of the panel surface were affixed to the stiff construction panel.

The strips were paced by air gaps which formed small voids of less than 4mm thickness, The resulting damping is apparently as effective as having a full sheet of viscoelastic barrier material on the construction panel, in the sense that shear strains within the viscouselastic material are still induced which greatly reduces or eliminates the stiff panel WO 2005/100709 PCT/A U20051000520 -11construction 'Coincidence effect' in the band width 1000 4000 Hz, which is the ear's most sensitive region.

It is believed that the small spaced air gaps (2-4mm in thicdness) between the construction panels, spaced also between viscoelastic strips or pads appear to act the same way as the actual viscoelastic material. That is, they do not allow the bending wave generated in the panel to reach the speed of sound in the medium surrounding the panel and thus avoid coincidence dips and phase reinforcement.

It should be noted that shear strains in the viscoelastic treatment actually transform bending waves into heat energy which is noiseless.

Advantageously, preferred embodiments such as for example that shown at Figs and 12 of this invention ftimtion via the following mechanism: Most rigid materials will be sympathetic to vibration at one or more frequencies, and damping materials are an efcient and effective means to control vibration and structure-borne radiated noise.

'Damping' is the energy dissipation properties of a material or system under cyclic stress, and damping vibration can significantly reduce the creation of secondary noise problems.

With the above two paragraphs in mind, the specially formulated non slip viscoelastic strips or pad matrix situated on the construction panel are in contact with the construction panel effectively increasing the vibrations' decay rate. Decay rate is the speed in dB/second at which the vibration reduces after panel excitation has ceased the higher the decay rate, the better the acoustic performance.

WO 2005/100709 PCT/AU2005/00S020 -12- By applying viscoelastic barrier material in strips and pads to construction board in the form of plasterboard the panel resonance at low frequencies was reduced and 'Coincidence effects' were also substantially eliminated, Although not shown in the drawings, a method of adhering the construction panel and viscoelastic barrier together has shown excellent adhering properties, and that is to utilise a pouring head which pours a hot or warm viscoelastic composition directly onto the construction board. The composition cools and then grips the face of the board. This may be used to make sandwiches of the compound, ie a second layer of construction board on to an upper surface of the cooling or curing composition.

Further experiments have been conducted on other preferred embodiments: In one embodiment, a wall was constructed as shown in Figure 10, starting on the outside: 13mm standard plasterboard panel 114; viscoelastic barrier 116 in strips 50mm wide, spaced at 50mm intervals along the panel 114; 13mmn standard plasterboard panel 118; 64mm staggered studs 122 in 9a0mm track; 20kg/'m polyester batt 126, 13mm standard plasterboard panel 115; viscoelastic barrier in strips 50rn wide 117, spaced at intervals; 13mm standard plasterboard panel 119. This wall underwent TL testing and the results are shown at Figure 9. Only a slight coincidence dip occurs at 1000 4000H1-z.

Overall, the STC and corrected transmission loss data are unexpectedly high for this type of construction.

Similarly, a wall constructed as shown in Figure 12 has a plurality of 50mm viscoelastic strips 216 spaced with a 150mm gap between each. The TL results appear at Figure 11 and they seem very similar to those shown in Figure 10, the only difference being the spacing between the viscoelastic strips. These results show the mechanism of the trapped air apparently working as a viscoelastic medium which reduces the buildup of transverse waves in the panel, without the mass or expense of an actual viscoelastic medium. Again, the STC and corrected transmission loss data are unexpectedly high for this type of construction.

WO 2005/10)709 PCT/AU2005/000520 -13 Some wall constructions do not include any absorptive batt material, and the results appear to be better than similar walls without absorptive batts.

A feature of a preferred embodiment of the present invention will become better understood from the following example of a preferred but non-limiting embodiment thereof Example 100 g of water together with 100 g of glycerine and 10 g of starch was mixed and then heated to a temperature of 85 tC. 80 g of gelatine and 20 g of magnesium chloride was then dissolved into the mixture and a gel was formed. 310 g of barium sulphate was then added to the gel providing a composition with good flexibility, elasticity, tensile strength, and density with good film fomning properties. The composition had the following composition by weight: 16% water; 16% glycerine; 1.5% starch; 13% gelatine; magnesium chloride; and barium sulphate.

The composition was then extruded into a flat sheet and bonded onto an aluminium film and then brought down to room temperature whereby the composition cured to form a sheet of composite material of 4mm in thickness that showed excellent sound dampening properties.

Finally, it is to be understood that various alterations, modifications and/or WO 2005/100709 PCT/AU2005/000520 -14additions may be incorporated into the various constructions and arrangements of parts without departing from the spirit or ambit of the invention,

Claims (33)

1. An acoustic laminate suitable for use in wall, floor and ceiling assemblies and other dividing structure assemblies, the laminate including: a flat construction panel; a viscoelastic acoustic barrier material in the form of discrete viscoelastic acoustic portions spaced across a face of the construction panel, the viscoelastic material affixed to one or more panel faces of the construction panel.

2. An acoustic laminate according to claim 1, wherein the construction panel is plasterboard, medium-density fibreboard, plywood, fibre-cement sheeting or timber,

3. An acoustic laminate according to claim I or 2, wherein the construction panel is affixed to the viscoelastic acoustic barrier material portions by adhesive.

4. An acoustic laminate according to any previous claim wherein the viscoelastic acoustic barrier material is poured onto the construction panel and cures on the panel, bonding to the panel during curing, providing increased bonding strength after cooling.

5. An acoustic laminate according to any previous claim wherein the viscoelastic acoustic barrier material portions are affixed to the construction panel in strips along an axis parallel to respective panel faces.

6. An acoustic laminate according to any previous claim wherein a matrix of viscoelastic pads are affixed to the construction panel across respective panel faces.

7. An acoustic laminate according to any previous claim wherein a second layer of construction panel is affixed to an outer face of the viscoelastic barrier material portions in order to provide a three-layer laminate, for captive-, or constrained-layer damping-type effect. Ar nsAsA.A Chp- PCT/AU2005/000520 Received 23 June 2005 I Ms;LNM ss'fKt%$ r -16-

8. An acoustic laminate according to any previous claim wherein the viscoelastic acoustic barrier material portions have a density within a range of 1000 kg/m 3 to 3000kg/rm 3

9. An acoustic laminate according to any previous claim wherein the acoustic laminate inhibits transmission at the frequencies typically forming a coincidence dip in construction panels, being approximately 1000 4000Hz.

An acoustic laminate according to any previous claim wherein acoustic barrier material portions have a thickness below 6mm.

11. An acoustic laminate according to any previous claim wherein acoustic barrier material portions have a thickness of 1.7mm. the viscoelastic the viscoelastic

12. An acoustic laminate according to any previous claim wherein the viscoelastic acoustic barrier material portions have a density is 1470kg/m.

13, An acoustic laminate according to any previous claim wherein the viscoelastic acoustic barrier material portions are constructed from a polymeric elastomer impregnated with material which in preferred forms is a particulate'material.

14. An acoustic laminate according to claim 13 wherein the filler material is calcium carbonate.

15. An acoustic laminate according to any previous claim wherein the viscoelastic acoustic barrier material portions have a Young's Modulus of less than 344kPa.

16. An acoustic laminate according to any previous claim wherein the acoustic laminate is incorporated into a sandwich of: construction board/viscoelastic barrier material portions/construction board. PCT/AU2005/00Q062 Fwfoo3SNMiws s Ea -2a Received 23 June 005

17- 17. An acoustic laminate according to any previous claim wherein the acoustic laminate is incorporated into a wall construction utilising studs and a cavity filled with polyester batts or other sound absorptive material.

18. An acoustic laminate according to any previous claim wherein the viscoelastic acoustic barrier material portions are in the form of a composition which includes water, gelatine, glycerine and a filler material.

19. An acoustic laminate according to claim 18 wherein the composition includes: 5 40 wt% water 30 wt% gelatine 40 wt% glycerine; and 60 wt% filler material.

20. An acoustic laminate according to claim 18 or 19 wherein the composition includes 1 to 15 wt% of a group II metal chloride such as for example calcium chloride or magnesium chloride.

21, An acoustic laminate according to any one of claims 18-20 wherein the composition includes 2 to 10 wt% magnesium chloride,

22. An acoustic laminate according to any one of claims 18-21 wherein the composition further includes 0.5 to 7 wt% starch or gluten.

23. An acoustic laminate according to any one of claims 18-22 wherein the starch is provided from the addition of cornflour to the composition.

24. An acoustic laminate according to any one of claims 18-23 wherein the filler material is a non-reactive material with a high density.

An acoustic laminate according to any one of claims 18-24 wherein the density is A manded (Rhi-t PCT/AU2005/000520 PPaX'.DOCsiMI. I PCTDIoca-3.0.. Received 23 June 2005 18- greater than 1 g/cm 3

26. An acoustic laminate according to claim 24 or 25 wherein the density of the filler material is approximately 2.0 to 3.0 g/cm 3

27. An acoustic laminate according to any one of claims 18-26 wherein the filler material is chosen from any non-reactive material with a high density such as for example barium sulphate or KAOLIN,

28. An acoustic laminate according to any one of claims 18-27 wherein the composition includes: 25 wt% water 20 wt% gelatine 25 wt% glycerine; 40 60 wt% filler material; 1 10 wt% magnesium chloride; and 3 wt% starch;

29. An acoustic laminate according to any one of claims 18-28 wherein the composition further includes constituents such as for example ethylene and/or propylene glycols; polyvinyl alcohols; deodorisers; anti-oxidants and/or fungicides.

A wall construction including an acoustic laminate according to any previous claim and including layers of construction panel affixed to staggered studs.

31. A wall construction including an acoustic laminate according to any previous claim and including absorbent material in the form of polyester baits.

32. An acoustic laminate substantially as hereinbefore described with reference to the attached drawings. PCT/AU2005/00052 Received 23 June 2005 WC~C~'Ud'Spc\US~RITht R, FCT -o-2).IXdt 19-

33. A wvall construction substantially as hereinbefore described withi reference to the attached drawings. DATED this 23 r day of June 2005 PHILIPPE PIERRE MARIE JOSEPH DONEUX By His Patent Attorneys DAVIESCOLLISON CAVE Amended Sheet IPEA/ALU