AU2008207636A1

AU2008207636A1 - Sound transmission loss-increasing construction panels

Info

Publication number: AU2008207636A1
Application number: AU2008207636A
Authority: AU
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-04-15
Filing date: 2008-08-29
Publication date: 2008-09-25
Also published as: AU2006225188A1

Description

Australian Patents Act 1990 Regulation 3.2 ORIGINAL COMPLETE SPECIFICATION STANDARD PATENT 1rO

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Invention Title: Sound transmission loss-increasing construction panels The following statement is a full description of this invention, including the best method of performing it known to me:- P/00/011 5951 Our Ref:12715501 P/00/011 Regulation 3:2

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Applicant(s): Address for Service: Invention Title: Philippe Pierre Marie Joseph Doneux Acoustica Pty Limited Ground Floor 6A Nelson Street Annandale New South Wales 2038 Australia DAVIES COLLISON CAVE Patent Trade Mark Attorneys 255 Elizabeth Street Sydney, New South Wales, Australia, 2000 Sound transmission loss-increasing construction panels The following statement is a full description of this invention, including the best method of performing it known to me:- 5951 P IWPDOCSe\XS\LNM\2pt6pepiU \DONEI X\2 SMI_12715501 Dvlo.k Slua Di,'do.2W09106 00 O-1- SOUND TRANSMISSION LOSS-INCREASING CONSTRUCTION PANELS 0 Field of the Invention SThis invention relates to construction elements suitable for use in constructing 0 0 internal walls, ceilings, roofs, floors and the like where reduction of transmission of Ssound 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 stiffness. 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 loglo(msf)- 48.

where: TL transmission loss (dB) ms mass per unit area (kg/m 2 f frequency of the sound (Hz) P \WPDOCS\GXSUNM\2006\1spkifONEUX\9 Sv. 12715501 Do~ Ncw S- d Divdo-2909/06 00 -2- Stiffness 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:

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I 5 fc A/t 00 where: A is a constant for a material St is the thickness of the material (mm) 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 regulations 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 P WPDOCSNGXS\LNiM\2OO6ftpm,'DON4EUX\29 S~pr 12'1 5O r itu New S-ud.wd D. do-29109/06 00 -3 increases with frequency. Every 'stiff panel construction' has a critical or coincidence frequency which considerably reduces the Sound Transmission Loss of structural panel construction.

IC 5 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 00 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. The present invention seeks to provide a construction partition panel laminate which improves acoustic transmission loss from one side to another.

Throughout this specification, the phrase "construction panel" is to be taken to include those flat panels constructed from plasterboard, plywood, glass -reinforced plastics, medium-density fibreboard, fibre-cement sheeting, timber, fibreglass, composites such as carbon fibre, and other sheets used in domestic construction of partition walls. Excluded from the definition are steel sheets, aluminium and aluminiumn honeycomb, C-beams, Ibeams, structural supports and the like.

Summary of the invention According to one aspect of the present invention there is provided a construction panel laminate having improved acoustic properties suitable for use in partition wall assemblies, the construction panel laminate including: a first flat construction panel; a viscoelastic acoustic barrier material layer affixed to the first flat construction panel.

PkWPDOCSNXS\NM,00fteri\DONELIX9Scp. 271250 Do.- NeS wdld t- do.29096 00 O -4- Preferably a second construction panel is affixed to an outer face of the viscoelastic barrier in order to provide a three-layer laminate, for captive-, or constrained-layer damping-type effect.

D 5 Preferably, the first and second construction panels are in the form of plasterboard, Smedium-density fibreboard, plywood, fibre-cement sheeting or timber.

00 Preferably, the viscoelastic acoustic barrier material layer is constructed from a polymeric elastomer impregnated with particulate material.

Preferably the particulate material is calcium carbonate.

Preferably, the first and second construction panels are affixed to the viscoelastic acoustic barrier material portions by adhesive.

Preferably, the viscoelastic acoustic barrier material is poured onto the first or second construction panel and cures on the panel, bonding to the panel during curing, providing increased bonding strength after cooling.

Preferably the viscoelastic acoustic barrier layer has a density within a range of 1000 kg/m 3 to 3000kg/m 3 Preferably the viscoelastic acoustic barrier layer has a surface density of approximately 2.5 kg/m 2 Preferably the viscoelastic acoustic 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 P %wPDOCSGXSU.NMI20O6\spu\DONEJX\29 Sep. 2715501 D-eol Ne. Slvmdad D.i.doc.29/09/06 00 O Preferably the viscoelastic acoustic barrier layer is faced on one side with a nonwoven polyester of thickness approximately 0.05mm.

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sO 5 Preferably the viscoelastic acoustic barrier layer is faced on the other side of the r- Sviscoelastic barrier or strips or pads by an aluminium film reinforced with polyester as a 00 water barrier.

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

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

Description of Preferred Embodiment 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); P \WPDOCS\XS \LNM2006\vmlONELf\29 Sc,_ 127 13501 Doaeu Ne.. S,.,dld D, dox29109/06 00 O -6- Figure 4 is a graph showing results of transmission loss testing of the wall shown in SFigure 2 (an STC63 curve is superposed on the test results); and IN Figure 5 is a graph showing graphs in Figures 3 and 4 superposed on similar axes; ID t"- SFigure 6 is a graph showing expected coincidence effects of prior art stiff panels; 00 SFigure 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; 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 1 kg/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 13mm 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/m 3 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.

P %WPDOCS\GXS.LNM\2O06\p\iDONEUX\29 Sept _12?$01 Nc- d D. do.-29/09/06 00 ;ZO -7- Experimental data utilising preferred embodiments of the present 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 glasswool and the reference wall used I lkg/m 3 glasswool to infill one side of the cavity.

Description 1/3 Octave Band Centre Frequency 100 125 160 200 250 315 400 500 630 Composite Wall 45 45 48 50 53 56 57 59 61 Reference Wall 37 42 44 47 51 51 55 58 61 Improvement 8 3 4 3 2 S 2 1 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 Improvement 2 2 1 -1 3 9 9 13 114 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 P \WPDOSGXS\NM006\spcc.\DONE LXU9 SrplI2715501 Dw N-I S7.,d Div dC.29/09/06 00 -8- ;Z differing densities are adhered together. This improvement is normally only of the order of 2 to 3dB. However, the performance gain in this experiment for the composite wall assembly 20 is 9dB, with significant gains in performance occurring above this frequency.

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

00 SWhen the concept of Acoustic Performance Index is applied to the composite wall assembly 20 (Figure 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 280mm wide or more. The composite wall system has a high Acoustic Performance Index of Rw greater than or equal to The combination of the construction panel and viscoelastic barrier material layer 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 6kg/m 2 (as we have shown above in the testing) we are expected to produce a gain in transmission loss of 2dB (see Also Figure 6).

However, in the testing above, at that frequency, we see TL gain of21dB.

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 a layer of viscoelastic material to the construction panels in the form 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. Also, an important effect, known as the P, WPDOC \XS\LNM\006\pcci\DONEUXU9 Slpr 1271 201 Dow- Nc Svdid Div dm.29/09/06 00 -9knocking syndrome effect, is affected. This effect is known in the field of plasterboard 0 dividing or partition walls, where a person knocks on the partition wall and is given a sensation that the building or wall is not solid because the wall returns a mid to high IO frequency knock. Some potential customers will not purchase or rent a dwelling if they are 0 5 given the sensation that the wall is not solid, even though the acoustic performance of the t"- Swall itself may be better than, say, a double brick wall. Partition walls incorporating the 00 laminate of the present invention or its preferred embodiments return a low-frequency, O solid knock when tapped or knocked upon. This engenders a sense of security regarding the performance of the dwelling and wall.

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

Advantageously, preferred embodiments of the invention may be incorporated in wall structures such as for example that shown in Fig 2 of this specification and function via the following mechanism: Most rigid materials will be sympathetic to vibration at one or more frequencies, and damping materials are an efficient 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 layer 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.

P\WP DOCSSXSL1NM20067\spc\DONEUX\29SC. l271I 501 x Ncw WIduvdd Div doc-29/09/06 00 0-10- ;Z Although not shown in the drawings, an improved method of adhering the 0i\ construction panel and viscoelastic barrier together has shown excellent adhering properties, and is one method, but not an essential method, of affixing the viscoelastic IND barrier material to the construction panels. The method is to utilise a pouring head which N 5 pours a hot or warm viscoelastic acoustic barrier composition directly onto the t"- 0 construction board. The composition cools and then grips the face of the board. This may 00 be used to make sandwiches of the compound, ie the second layer of construction board on 0to an upper surface of the cooling or curing composition.

Finally, it is to be understood that various alterations, modifications and/or additions may be incorporated into the various constructions and arrangements of parts without departing from the spirit or ambit of the invention.

Claims

1. A construction panel laminate suitable for use in partition wall assemblies and IND having improved acoustic properties, the construction panel laminate including: a ND 5 first flat construction panel; a viscoelastic acoustic barrier material layer affixed to lr- 0 the first flat construction panel. 00

2. A construction panel laminate in accordance with claim 1 wherein a second flat construction panel is affixed to an outer face of the viscoelastic barrier in order to provide a three-layer laminate so as to provide a type of captive, or constrained- layer effect.

3. A construction panel laminate in accordance with claim 1 or 2 wherein the flat construction panel is in the form of plasterboard, medium-density fibreboard, plywood, fibre-cement sheeting or timber.

4. A construction panel laminate in accordance with any previous claim wherein the viscoelastic acoustic barrier material layer is constructed from a polymeric elastomer impregnated with particulate material.

A construction panel laminate in accordance with claim 4 wherein the particulate material is calcium carbonate.

6. A construction panel laminate in accordance with any previous claim wherein the viscoelastic acoustic barrier material layer is affixed to an adjacent flat construction panel by adhesive.

7. A construction panel laminate in accordance with any previous claim wherein the viscoelastic acoustic barrier material layer is poured onto the first construction panel and cures on the panel, bonding to the panel during curing, providing increased bonding strength after cooling. ?:\WPDOCSGXSMLNM\006MpCi\DONEUX29 Scpl_12715501 Docux Ncw Stlrdad Div.doc.2910906 00 -12-

8. A construction panel laminate in accordance with any previous claim wherein the viscoelastic acoustic barrier layer has a density within a range of 1000 kg/m to N 3000kg/m 3 IND r~- 0

9. A construction panel laminate in accordance with any previous claim wherein the 00 viscoelastic acoustic barrier layer has a thickness below 6mm.

A construction panel laminate in accordance with any previous claim wherein the viscoelastic acoustic barrier layer is faced on one side with a nonwoven polyester of thickness approximately 0.05mm.

11. A construction panel laminate in accordance with any previous claim wherein the viscoelastic acoustic barrier layer is faced on the other side of the viscoelastic barrier material layer by an aluminium film.

12. A partition or dividing wall incorporating a construction panel laminate in accordance with any previous claim wherein the partition wall includes staggered studs and a cavity filled with polyester batts or other sound absorptive material.

13. A construction panel laminate substantially as hereinbefore described with reference to the attached drawings.

14. A partition wall substantially as hereinbefore described with reference to the attached drawings.