The present invention relates to the suppression of acoustic transmission through building construction panels and particularly, but not exclusively, to: (i) building panel(s) coupled with a vibration damping means; (ii) a wall, ceiling or floor construction manufactured from a plurality of building panels, each being coupled with a vibration damping means; and (iii) a method of manufacturing same.

The problem of unwanted airborne and impact noise transmission through dividing structures within buildings is well recognised. Much effort and investment has been expended by the building and construction industry towards addressing such noise transmission problems, particularly in respect of residential dwellings, not least due to the need for compliance with international standards and other associated legislative requirements imposed by national or regional governments.

In an effort to minimise unwanted sound transmission resulting from, e.g. plasterboard panel resonance, it is known to sandwich acoustic insulating materials such as plastic foams, mineral wools and the like between two plasterboard layers. However, such a solution necessarily increases both material and labour costs whilst decreasing room size as a consequence of the overall increase in thickness of the dividing structure.

A commonly adopted alternative is to directly adjoin two building panels of different densities, either by screwing, gluing, or both. The resultant laminated panel has additional mass, thickness and stiffness and two non-overlapping resonant frequencies, all of which combine to reduce sound transmission within critical audible frequency ranges. Whilst this represents a convenient solution which minimises the aforementioned reduction in room size, there is still a significant cost implication in terms of the additional materials involved as compared to constructions formed from single plasterboard layers. For example, the application of a layer of Green Glue™ viscoelastic sound dampening compound can add approximately two thirds to the cost of a single plasterboard panel, as well as requiring significant and repetitive manual effort to extrude the curable compound using a caulk gun.

A building panel according to the preamble of claim 1 or 10 is described in GB 730 899 A.

Accordingly, there is a requirement for a building panel which provides recognisable improvements in acoustic transmission properties whilst mitigating or obviating one or more of the aforementioned disadvantages.

According to a first aspect of the present invention, there is provided a building panel for attachment to a support frame, the building panel having opposing first and second panel faces wherein a layer is coupled to one of the panel faces; wherein the layer is of elastomer-modified bituminous material coupled to a panel face in an unconstrained manner and wherein it is provided in the form of an elongate band which extends generally longitudinally in between opposite perimeter edges of the panel without extending to any of its perimeter edges.

Optionally, the bituminous material is modified by a Styrene-Butadien-Styrene (SBS) elastomer.

Optionally, the bituminous material comprises a natural fibre or synthetic fibre carrier.

Optionally, the bituminous material is coupled to less than 50% of the whole surface area of at least one of the panel faces.

Optionally, the building panel is rectangular in shape.

Optionally, the band of bituminous material extends along the central longitudinal axis of the panel.

Alternatively, two or more bands of bituminous material extend generally longitudinally in between opposite perimeter edges of the panel.

Optionally, the bands of bituminous material are arranged in parallel and are spaced from each other by a distance equal to or greater than the width of a standard wall support frame member or stud.

Optionally, the bituminous material is arranged on the building panel in the form of one or more straight elongate bands.

Optionally, the elongate band of bituminous material is provided with a self adhesive surface for coupling to the building panel.

Optionally, the elongate band of bituminous material has a width in the range of 20 - 200 mm.

Most preferably, the elongate band of bituminous material have a width of 150 mm.

Optionally, the elongate band of bituminous material has a thickness in the range of 2 mm to 20 mm.

Optionally, the bituminous material has a tensile strength in the range of 100 - 400 N/50mm.

Most preferably, the bituminous material has a tensile strength of 300 N / 50 mm.

Optionally, the building panel is a plasterboard panel.

Optionally, the plasterboard panel has length of 2400 mm, a width of 1200 mm and a thickness in the range of 12-20 mm.

According to a second aspect of the present invention, there is provided a composite building panel comprising two superimposed building panel layers each having opposed first and second panel faces, and the composite building panel comprising a layer of elastomer-modified bituminous material sandwiched between the opposing building panel faces; wherein elongate bands of the elastomer-modified bituminous material extend around the perimeter edges of the opposing building panel faces whilst leaving a central portion uncovered so as to define an internal cavity between the opposing building panel faces and the surrounding elastomer-modified bituminous material.

Optionally, an additional elongate band of elastomer-modified bituminous material extends along the central longitudinal axis of the building panels between their opposing perimeter edges to define two internal cavities between the opposing building panel faces.

Optionally, the width of the elongate bands is equal to or greater than the width of a standard wall support frame member or stud.

According to a third aspect of the present invention, there is provided a dividing structure in the form of a wall, ceiling or floor comprising one or more panels according to the first aspect.

According to a fourth aspect of the present invention, there is provided a dividing structure in the form of a wall, ceiling or floor comprising two or more composite panels according to the second aspect.

According to a fifth aspect of the present invention, there is provided a method of manufacturing a dividing structure according to the third aspect comprising the steps of:

1. (i) providing a plurality of building panels;
2. (ii) providing a length of elastomer-modified bituminous material;
3. (iii) coupling one or more bands of the elastomer-modified bituminous material to one face of each building panel such that it does not extend to any perimeter edges of the panel and does not overlap with an underlying support frame when in-situ; and
4. (iv) fixing the panels on a support frame to form a dividing structure;
   wherein steps (iii) and (iv) above may optionally be performed in reverse order.

Optionally, the elastomer-modified bituminous material is provided in the form of a roll and the coupling step is achieved by unrolling the roll such that an adhesive surface of the elastomer-modified bituminous material adheres to less than 50% of the whole surface area of one face of each building panel.

According to a sixth aspect of the present invention, there is provided a method of manufacturing a dividing structure according to the fourth aspect comprising the steps of:

1. (i) providing a plurality of building panels;
2. (ii) providing a length of elastomer-modified bituminous material;
3. (iii) fixing a first subset of the building panels on a support frame;
4. (iv) coupling bands of the elastomer-modified bituminous material around the entire perimeter edges of one face of the fixed building panels; and
5. (v) superimposing a second subset of the building panels over the first subset and fixing them on the support frame.

Optionally, the elastomer-modified bituminous material is provided in the form of a roll and the coupling step is achieved by unrolling the roll such that an adhesive surface of the elastomer-modified bituminous material adheres to less than the whole surface area of one face of the first subset of the building panels.

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which:

• Fig. 1 is a graphical representation of a typical Transmission Loss curve of a building wall or floor construction;
• Fig. 2 is a schematic representation of the bending wave displacement of a single sheet of plasterboard attached near its periphery to a timber frame;
• Fig 3a is a schematic representation of a single-skin building panel attached to a support frame and having strips of elastomer-modified bituminous material attached thereto in an unconstrained manner;
• Fig. 3b is a cross-sectional view through line A-A of Fig. 3a;
• Fig. 4a is a schematic representation of a double-skin building panel attached to a support frame and having strips of elastomer-modified bituminous material sandwiched between the two in a constrained manner;
• Fig. 4b is a cross-sectional view through line B-B of Fig. 4a;

The ability of a building panel to attenuate sound transmission can be assessed by plotting its Transmission Loss (dB) across a range of frequencies. The Transmission Loss, and hence the sound insulation curve, of any given panel is determined by a number of factors such as the panel's density, its stiffness, its thickness, its width and its height. The solid line in Fig. 1 is representative of a typical sound insulation curve of a building wall or floor construction. It can be seen that the sound insulation generally improves with increasing frequency with the exception of a marked reduction at higher frequencies centred around 2,000 Hz. This phenomenon occurs as a result of the panel resonances.

Resonance is an inherent characteristic of any given panel and this is exemplified with reference to Fig. 2 which shows a single sheet of plasterboard attached near its periphery to a timber frame via six screw fixings. Incident acoustic energy travelling along one side of a typical plasterboard panel generates a bending wave which causes the non-fixed portions of the panel to be displaced with the maximum displacement occurring furthest from the screw fixings. The consequent vibration of the plasterboard panel radiates unwanted sound - in the manner of a diaphragm - on the opposite side of the panel within the audible frequency range. If incident sound matching a panel's own characteristic fundamental frequency strikes the panel, the resultant vibro-acoustic sound energy emitted from its opposite surface reaches its greatest level. The vibro-acoustic sound transmitted at each subsequent harmonic frequency is progressively reduced.

The present invention derives from the discovery that a surprisingly effective degree of building panel resonance damping can be achieved through the strategic coupling of elastomer-modified bituminous material to only a partial portion of a building panel's surface area.

For example, Figs. 3a and 3b are representative of a standard rectangular gypsum plasterboard panel (10) - having a thickness of 19 mm - with two elongate strips or bands (12) of elastomer-modified bituminous material attached thereto longitudinally and in parallel between its opposite edges (14, 16). In the nonlimiting example shown, the elastomer-modified bituminous material measures 4 mm thick by 15 mm wide and its inner panel-facing surface is provided with a self-adhesive substance. Preferably, the bituminous material is modified by blending it with a thermoplastic elastomer. Most preferably, the thermoplastic elastomer is styrene-butadiene-styrene (SBS). Suitable SBS thermoplastic elastomers are manufactured by Asahi Kasei Chemicals Corporation and sold under the trademarks Tufprene® and Asaprene®. In a preferred embodiment, the SBS elastomer-modified bituminous material has an SBS content of 5% to 80% by weight; an air permeance of <0.01m³/m²hPa; a water vapour permeability of 0.37 m; and a tensile strength of approximately 300N / 50 m. The SBS elastomer-modified bituminous material may be applied to a natural fibre or synthetic fibre carrier, e.g. a polyethylene felt.

The strips (12) of elastomer-modified bituminous material are attached to the plasterboard panel (10) so as to coincide with the two maximum nodal points of displacement (i.e. centrally between the underlying supporting framing members (18) shown in dashed lines) during resonance at their fundamental or 1^st harmonic frequencies. It can be seen that a significant proportion of the surface area of the plasterboard panel is left exposed.

The positioning of the strip(s) of elastomer-modified bituminous material on plasterboard panels can be varied depending upon the particular arrangement of the supporting structure to which they are attached. In each case, the placement of the elastomer-modified bituminous material can be optimised so as to coincide with the region of the panel exhibiting the maximum amount of displacement during resonance at its fundamental or 1^st harmonic frequency. No part of the elastomer-modified bituminous material extends to any of the perimeter edges of the plasterboard panels. Importantly, this avoids any bowing of the panel which would otherwise result from a localised increase in thickness at the point where the elastomer-modified bituminous material would engage an underlying timber frame. As well as being undesirable from a structural and aesthetic standpoint, such bowing has been found to contribute to decreased sound insulation performance during testing. Given that timber wall studs are generally provided in standard widths of between 36mm and 47mm, it is therefore necessary to ensure that no part of the elastomer-modified bituminous material extends to within a corresponding distance from any of the perimeter edges of the plasterboard panels.

In an alternative embodiment of the present invention - represented best by Fig. 4b - a composite structure comprises two superimposed building plasterboard panels (20, 22) of the type described above with reference to Figs. 3a and 3b. A first plasterboard panel (20) is fixed to a supporting structure (24) comprising vertical and horizontal framing members. Strips (26) of elastomer-modified bituminous material are adhered to the opposite face of the first plasterboard panel (20) at regions coinciding with the panel's attachment to the vertical and horizontal framing members (24), i.e. using the central fixing positions of the first panel (20) to the framing members (24) as a guide for proper placement. A second plasterboard panel (22) is fixed to the supporting structure (24) through the regions of elastomer-modified bituminous material and the underlying first plasterboard panel (20) such that the panels (20, 22) are superimposed. By virtue of the thickness of the interposed strips (26) of elastomer-modified bituminous material, a cavity is formed between the two plasterboard panels (20, 22). Typically, the spacing of the two plasterboard panels (20, 22) may be between 2mm and 10mm thick.

The total surface area coverage of the elastomer-modified bituminous material constitutes a minority of the overall surface area of the plasterboard panel's face. For example, in the first arrangement shown in Fig. 3a the total surface area coverage of the elastomer-modified bituminous material constitutes approximately 47% of the total 2.88 sq. m surface area of the plasterboard panel. In the arrangement shown in Fig. 4a the total surface area coverage of the elastomer-modified bituminous material constitutes less than 43% of the total 2.88 sq. m surface area of the plasterboard panel.

In use, the apparatus and method of the present invention is capable of providing significant efficiencies and cost savings to the building and construction industry. In the example of Figs. 3a and 3b, the strips of elastomer-modified bituminous material act as an unconstrained damping layer to reduce the amplitude of the resonant frequency of a single-skin building panel (10). Accordingly, plasterboard panels of a lower thickness and/or density may be employed without compromising on acoustic insulation. Indeed, in certain circumstances, an improvement in acoustic insulation performance could even be achieved whilst using fewer materials, e.g. by avoiding the need for a secondary panel, or reducing the thickness of any required insulation quilt between superimposed panels. To illustrate this point, it is known that - across certain frequencies - the use of a 100 mm thick insulating quilt provides a 2-3 dB improvement in terms of acoustic insulation as compared to use of a 25 mm quilt. As such, a similar level of acoustic improvement found in the present invention (as noted below) will permit a reduction in thickness of insulation quilt of up to 75%.

In the example of Figs. 4a and 4b, the strips of elastomer-modified bituminous material act as a constrained damping layer to reduce the amplitude of the resonant frequency of a double-skin or composite building panel (20, 22). The formation of a cavity between the two panels serves to increase mid and high frequency sound insulation performance.

In practice, the presence of the strategically positioned strips of elastomer-modified bituminous material significantly reduces the degree of resonance over a broad range of higher audible frequencies. This is achieved by means of viscoelastic properties inherent in the SBS elastomer-modified bituminous material which aid conversion of the bending wave experienced in the panel to a shear wave such that energy is lost in the form of heat rather than as sound. Clearly, the highest amount of energy loss (and hence sound suppression) will occur when the elastomer-modified bituminous material is adhered to the part of the panel which bends the most at resonant frequencies. An improvement in sound insulation of 2-3 dB (DnTw rating) has been observed during testing.

Modifications and improvements may be made to the foregoing without departing from the scope of the present invention as defined by the accompanying claims. For example, whilst the supporting frames or studs have been described throughout as being made from timber, alternatives are of course possible, e.g. steel frames. Whilst the present invention has been described with reference to plasterboard panels, it is equally applicable to other types of building panels of different shapes, sizes, thicknesses etc. Indeed, throughout this specification the terms "building construction panel" or "building panel" are to be understood to include flat, curved or corrugated panels, sheets or boards which are thin in relation to their length and breadth, and which comprise, inter alia, one or more of the following materials: gypsum plaster, fibreglass, medium density fibreboard, magnesium oxide board, fibre cement, plywood, timber, glass-reinforced plastics; or any other sheeted materials used in the construction of walls, ceilings and floors.

Moreover, it will be appreciated that the term "strip" and "band" used throughout the foregoing description relates to a piece of material which is a comparatively long and narrow. The terms "strip" and "band" are to be distinguished from a "sheet" or "panel" in terms of their relative dimensions. For example, in the context of the present invention, a "sheet" or "panel" will always be wider than a "strip" or "band" attached thereto. As a general rule, a "strip" or "band" will be less than 50% of the width of a "sheet" or "panel" attached thereto. Since a standard plasterboard panel has a width of 1200 mm, then a "strip" or "band" will have a width of less than 600mm. As noted above, in certain embodiments the width of a "strip" will fall within the range 20mm to 200mm and - in preferred embodiments - may be equal to, or greater than, the width of a standard wall support frame member or stud which measures approximately between 36mm and 47mm.