Variable acoustic covering system for boundaries of a room

Abstract

The invention relates to an acoustic covering system for covering at least parts of a boundary (B) of a room, the acoustic covering system being configured to provide variable sound absorption, where the acoustic covering system comprises: a solid structure (2) configured to be attached to the boundary (B), such that the solid structure (2) and the boundary (B) form a space (S); and one or more boards (6) attached to the solid structure (2) and configured to selectively move relative to the solid structure (2), such that, in an open state of the acoustic covering system, one or more respective openings (45) are created between the one or more boards (6) and the solid structure (2) on at least part of a circumference of the respective one or more boards (6) to enable sound energy to pass through and reach sound absorbing means (12) within the space (S) between the one or more boards (6) and the boundary (B), wherein the sound energy is absorbed in the open state of the acoustic covering system to lower the reverberation time, RT, in the room when the acoustic covering system is installed.

Description

[0001] VARIABLE ACOUSTIC COVERING SYSTEM FOR BOUNDARIES OF A ROOM

[0002] TECHNICAL FIELD

[0003] The invention relates generally to the field of room acoustics and more particularly to devices, systems and methods for altering the reverberation time of rooms or other locations, in which various kinds of performances are to take place, such that the reverberation time can be optimized to each specific kind of performance.

[0004] The following background is intended solely to provide information necessary to understand the context of the inventive ideas and concepts disclosed herein. Thus, this background section may contain patentable subject-matter and should not be regarded as prior art per se.

[0005] BACKGROUND OF THE INVENTION

[0006] Many concert halls and spaces for music performance in general are created today with some sort of panels on walls and / or ceiling areas. This is due to the fact that such panels provide an attractive aesthetic with e.g. wood veneer surface as well as the right acoustics for either classical, unamplified music (the panels are not perforated) as well as for amplified music (the panels are perforated and there are porous absorption behind).

[0007] The two panel types give two different reverberation times in the halls they are installed in, which is a requirement for the two types of music to sound good and therefore the two types of panels are roughly used in two different types of halls for each of their respective musical genres.

[0008] Hence, it would be an advantage in the design of music halls to provide a solution where a single type of paneling could be used in a way so that both classical music and amplified music would sound good.

[0009] The techniques presented in this disclosure is the first ever solution to this challenge using non-perforated boards, and it is based on research into appropriate acoustics for amplified performances - an area that he has largely single-handedly developed.

[0010] As is well known within the field, passive variable acoustic techniques are used to bring down reverberation time (RT) from a high value (e.g. 1 ,9 sec.) suitable for un-amplified music (such as chamber music) to a lower value, (e.g. 1 ,1 sec) for amplified music (such as pop and rock, and also speech). By employing rather narrow (e.g. 5-60mm) openings, such as “slits” in a board (in front of some absorption material), which openings are spaced quite far from each other (e.g. 8-20 cm apart), a quite high degree of 125 Hz sound will be absorbed given a deep enough cavity with porous absorption behind it. Such an absorber is in acoustics referred to as a slit absorber. However, since it has always been assumed that the RT in the entire audible frequency spectrum, as mentioned needs to be lowered, slit absorbers have not been thought to make a sufficient variability of RT, since mid- and hi frequencies are not lowered as much as the lower frequencies in such a slitted board.

[0011] SUMMARY

[0012] This summary is provided to introduce a selection of features and concepts of the invention that are further described below in the description. This summary is not intended to identify key or essential features of the claimed subject-matter, nor is it intended to be used in limiting the scope of the claimed subject-matter.

[0013] As mentioned above, prior art techniques make use of a slitted / perforated board where the perforations are closed in the OFF state. The invention makes use of boards which are NOT slitted / perforated - and thus easier to integrate and also more aesthetic in design.

[0014] Even though the variable acoustic technique described in the above documents provides the desired high sound absorption in the 125 Hz octave band, an even more visually attractive solution would be to have entire non-perforated plates / boards (size e.g., 60x120 cm or larger) open up to some absorption material in a cavity behind the plate / board. The notion, that such a configuration would be sufficiently acoustically effective may seem counterintuitive since it would be hard to imagine any significant absorption stemming from narrow openings spaced so far from each other, e.g. more than 40 cm. Yet laboratory tests have proven a surprisingly high absorption value from such a configuration.

[0015] It was further surprisingly found in these laboratory tests that even higher values of sound absorption coefficients in the 125 Hz octave band than those found by using traditional slits, were found by tilting a plate from its closed position out to an angle, creating a gap that can be more than 10 cm (or 15 cm, 20 cm or 30 cm). Such a large gap is not a traditional slit (see slit absorber) formed in a board / plate (typically between 1mm and 20mm gap, and e.g., not much wider than the thickness of the board / plate). It even creates an aesthetic design in the open state since the board is not perforated as well as the required sufficiently large absorption coefficient in the important 125 Hz octave band. A further advantage of the invention is, that the mechanics required to move the panels, is much more simple and thus less expensive to manufacture and less likely to malfunction, than the more complicated mechanics required to close perforations in perforated boards. Also, the challenge of avoiding residual absorption in the board due to a Helmholtz-type absorption in the perforations themselves when in the OFF state, can be overcome by the invention.

[0016] Aspects of the invention are defined in the independent claims. Specific embodiments are defined in the dependent claims.

[0017] Further, the following aspects are included in this disclosure.

[0018] An aspect may provide an acoustic covering system for covering at least parts of one or more boundaries of a room. The system may be configured to provide means for alteration of acoustic properties of the room. The system may comprise a plurality of boards. The boards may have a front face and a rear face. The boards may be mounted on a support structure (e.g. the solid structure herein). The support structure may be configured to be held in a fixed position relative to said boundary. The support structure may be configured to support the boards such that they can undergo a tilting, pivoting or displacing movement relative to the support structure. The boards may be configured to be tilted, pivoted or displaced from a closed state to an open state. In the closed state, sound energy may be prevented from passing from the front face of the panels (e.g. the boards) to sound absorbing means (e.g. the sound absorber) provided between the boards and the boundary. In the open state, an air passage may be created along a portion of the circumference or along the entire circumference of the boards. The air passage may provide access for the passage of sound energy (from the front face of the board and / or from the room) to the sound absorbing means provided between the boards and the boundary (relative to which the system is attached).

[0019] The system may be provided with means that are configured to prevent sound energy from reaching said sound absorbing means via other paths. These means may be rubber elastic materials such as ethylene propylene diene monomer (EPDM) rubber. The EPDM ruber may be arrange on the inner surface of a respective board along an edge portion thereof.

[0020] Further, the boards may be selectively moved to adapt an absorption curve of the acoustic covering system.

[0021] The system may be configured such that, in the open state of the boards, a specific board is tilted, pivoted or displaced differently than the adjacent boards. Adjacent boards may be separated from each other more than a minimum distance between edge portions of the adjacent boards. The boards in the open state of the system may be tilted, pivoted or displaced equally. The minimum distance may be 2cm (or 3cm or 4cm).

[0022] The support structure may comprise a plurality of support sections (e.g. the frame sections). Through the support sections, sound can pass through the support structure. For each of the support sections an associated board may be provided. The associated board may be configured to be tilted an angle relative to the corresponding support section in such a manner that in the first state of the system (e.g. the closed state), the respective associated board closes the corresponding support section and in the second state (e.g. the open state) of the system the respective associated board opens for the passage of sound through an opening formed between the associated board and the support structure, such that sound can pass through the support structure to the sound absorbing means.

[0023] Each of said sections may comprise a first contact region. The associated board may comprise a second contact region that in the closed state of the system overlaps the first contact region on the corresponding support section such that an acoustically tight closing is obtained between the associated board and the corresponding support section in the closed state of the system.

[0024] The rear face of the board that may face the support structure may be provided with a cover plate made of steel or other material that can be attracted by a magnetic force. The first contact region on the corresponding support section may be provided with magnetic means configured to attract the cover plate and to maintain an acoustically tight contact between the board and the corresponding support section in the closed state of the system. The steel plate may be magnetic. In the closed state, a rubber casket may (circularly / loop-wise) connect the board and the frame section. Each of the boards may have a rubber casket. The rubber casket may be arranged along an edge portion of the board to form a closed ruber casket loop between board and support structure.

[0025] Each respective associated board can be tilted an respective angle relative to the corresponding support section. The angle may be in the range 0 to 60 degrees, preferably 0 to 45 degrees, or preferably 0 to 20 degrees or preferably 0 to 10 degrees. The respective angle can be different for different associated boards.

[0026] Also frequency variability can be created by opening the board(s) between 0 and 180 degrees.

[0027] So, the board can be titled in the range between 0 and 90 degrees (or even 0 and 180 degrees) where a certain absorption curve (absorption coefficient versus frequency) can be chosen. The frontside of the board(s) can be designed to diffuse or scatter sound. The board(s) may be formed in a convex or concave shape, e.g. along one or multiple dimensions of the board(s).

[0028] One edge portion of each respective board when the board is tilted may remain in contact with the corresponding portion of the respective section of the solid structure.

[0029] The first contact region may be provided with magnetic means, such as a magnetic ribbon. The second contact region may be provided with means that is / are attracted by the magnetic force from the magnetic means provided in the first contact region.

[0030] The second contact region may be provided with magnetic means, such as a magnetic ribbon, and said first contact region is provided with means that is / are attracted by the magnetic force from the magnetic means provided in the second contact region.

[0031] The system may be provided with one or more tilting mechanisms. The one or more tilting mechanisms may be configured to allow all boards of the system to be tilted using one single drive means, such as an electric motor, pneumatic motor or the like.

[0032] The system may be provided with one or more tilting mechanisms. The one or more tilting mechanisms may be configured to allow one or more subsets of boards of the system to be tilted using one drive means for each subset of boards, such as an electric motor, pneumatic motor or the like.

[0033] The tilt angle of the individual boards may be determined based on the direction in which sound reflection should be directed, when the system is mounted in a specific room.

[0034] The support structure may comprise a plurality of pivot axes. A number of boards may be provided adjacent to each other along the pivot axis such that the individual boards can undergo a pivotal movement. Two adjacent boards at the respective edge portions that face each other may be provided with cooperating closure means. The closure means may be configured to enter into an acoustically tight engagement, when the system is in the closed state.

[0035] The closure means may be formed as mutually corresponding recesses formed in the respective edge portions of the adjacent boards.

[0036] The closure means may comprise magnetic means. The magnetic means may be configured such that a force of attraction is obtained between the respective closure means such that the respective closure means thereby establishes an acoustic tight closing between the two adjacent boards. For example, the system may comprise said support structure. For example, the system may comprise a plurality of boards configured to be displaced a distance d, where 0 < d < dMAX in such a manner that the rear face of the board is substantially the same distance from the front face of the corresponding part of the support structure for any value of d in the range 0 < d < dMAX. dMAX may be larger than 2cm (or 5cm or 10cm). dMAX may be smaller than 60cm (or 50cm or 40cm or 30cm).

[0037] The frame support structure and said boards may be substantially planar (for example at several surfaces of the respective frame sections and boards).

[0038] The width of the, not necessarily rectangular board, when measured between two equally opened sides, can be either 70-140 cm or 170 -240 cm. The boards with a same width (or width range) can be intermittently or alternately arranged with other boards having a same second width (or width range) along a (e.g. horizontal) row or multiple rows of the acoustic covering system. The multiple rows may be arranged parallely such that boards width same width (or width range) are place directly next to each other (e.g in a column of the acoustic covering system). In other words, the acoustic covering system may comprise compartments arranged in a matrix of multiple rows and columns.

[0039] The construction depth may be less since the closing mechanism takes up less depth. This is due to the fact that a closing mechanism for closing perforation I slits from the inside takes up more space, wherefore the construction will be deeper (typical more than 20 cm or even 25 cm. A less deep construction may be more aesthetically implementable in a room and takes up less concert hall space. Since space is evidently expensive to build, costs may be reduced.

[0040] Another advantage of a slim construction may be, that the inherent, unwanted absorption in the closed state of the absorber, due to membrane absorption, becomes lesser. This is because the half-power bandwidth (Q-value) may get smaller in a membrane absorber the less deep it is. The absorption curve may be narrower. Therefore, the total absorption of a less deep construction may be smaller. It may be a goal to attain a value as low as possible since any absorption in the closed state is unwanted.

[0041] There may be an advantage of a steel plate mount to the back-side of the board (or backside of the fiber plate). It may add weight to the board without making it much thicker. The board construction being heavy may allow less low frequency sound energy to enter the sound absorption means in the closed state of the construction. This means that the inherent, unwanted absorption of the construction may be reduced. Also, the steel plate can be welded. Thus the board construction can be provided with means for attaching actuator etc. The plate may also be provided with threaded rods. The threaded rods may be welded to the steel plate to which actuator etc. can be screwed and securely fastened. The actuator may be or be part of the electrical drive or drive means.

[0042] The opening between adjacent boards may be created by tilting boards at approximately the same angle. There may be a distance of at least 3 cm between adjacent boards. The distance between adjacent boards may be larger than 4cm (or 6cm or 8cm). The distance between adjacent boards may be smaller than 20cm (or 15cm or 10m). The opening between adjacent boards may be created by the boards being tilted at different angles.

[0043] The system may comprise a plurality of separate enclosures (e.g. frame sections). Each of the separate enclosures may be provided with a corresponding board. The corresponding board may be configured to be tilted, pivoted or displaced relative to the corresponding enclosure between said closed state and open state. The respective enclosure may form a cavity in which there is provided sound absorbing means.

[0044] An aspect may provide a method for obtaining a desired reverberation time and especially a desired Early Decay Time (EDT) of a room as a function of frequency. The method may comprise providing at least one system as described above on one or more chosen boundaries of the room in such a manner that the boards of the at least one system in the open state of the system can be tilted or pivoted downwards towards the floor of the room. The front face of the boards may face the floor of the room. Further, the method may comprise tilting or pivoting the boards in the open state of the system in such a manner that a part of the sound emitted by a sound source, such as an orchestra or band playing music, may be reflected from the front face of at least a number of the boards making up the system towards the area in the room in which an audience is seated.

[0045] All technical and scientific terms used herein have the meaning which corresponds to the general understanding of the skilled person in the technical field of technical acoustics; they are to be understood based on the definition in a lexicon or technical jargon about this technical field. If technical terms are used incorrectly herein, and thus do not reflect the technical concept of the present invention, these may be replaced by technical terms which convey a correct understanding to the skilled person.

[0046] In the present disclosure, if a component is "connected to” another component, this can mean that these components can also be directly connected with each other. The term "directly" indicates that there is no other component in between. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Other objects, features, advantages and applications will become apparent from the following description of non-limiting embodiments with reference to the accompanying drawings. The same or similar components are always provided with the same or similar reference signs. Detailed explanations of known functions or structures are omitted, insofar as they are unnecessarily distracting from the invention.

[0048] The drawings show in:

[0049] Figs. 1 (a) and (b) renderings of acoustic covering systems;

[0050] Figs. 2 (a) and (b) further renderings of acoustic covering systems;

[0051] Figs. 3 (a) to (d) different tilting patterns of the boards of acoustic covering systems;

[0052] Fig. 4 a schematic perspective view on the acoustic covering system;

[0053] Fig. 5 (a) a schematic perspective view on the acoustic covering system with tilted boards;

[0054] Fig. 5 (b) a front view of the acoustic covering system in Fig. 5(a);

[0055] Fig. 6 a solid structure for the acoustic covering system;

[0056] Fig. 7 an example of the tilt and hinge mechanism;

[0057] Fig. 8 an example of the tilt without hinge mechanism;

[0058] Fig. 9 an example of the displace mechanism;

[0059] Fig. 10 a schematic perspective view of a single section of the solid structure;

[0060] Figs. 11 (a) and (b) another acoustic covering system;

[0061] Fig. 12 a plot of sound absorption coefficient over frequency;

[0062] Figs. 13 (a) and (b) a cross-sectional views of a room with a single board of the acoustic covering system; and

[0063] Fig. 14 (a) and (b) schematic perspective views of single frame sections and multiple frame sections in a row; Fig. 15 a photo of an acoustic covering system on the floor;

[0064] Fig. 16 a photo of an acoustic covering system without boards on the wall;

[0065] Fig. 17 a photo of a board with a steel plate and mounted actuators; and

[0066] Fig. 18 certified measurement results.

[0067] DETAILED DESCRIPTION OF THE INVENTION

[0068] The acoustic covering system will now be described with respect to the embodiments. In particular, without being restricted thereto, specific details are set forth to provide a thorough understanding of the invention.

[0069] Moreover, spatially relative terms such as "bottom", "below", "lower" "down", "top", "above", "upper", “top”, “left”, “right”, “front”, “back” and the like, may be simply used to describe the relationship of components to one another as shown in the drawings. It is clear that these spatially relative descriptors are intended to include additional orientations of the device when in use or in service. In particular, the device may be reoriented (e.g., rotated 90 degrees or in a different orientation), and the spatially relative descriptors used herein may therefore be interpreted accordingly.

[0070] Fig. 1(a) and (b) shows renderings of acoustic covering systems mounted on boundaries (a portion of a side wall and on the back wall) of a room. Specifically, Fig. 1 (a) shows the acoustic covering systems in a closed state, in which sound is not absorbed by the acoustic covering system according to the invention, and Fig. 1(b) shows the same systems as in Fig. 1(a), but in an open state, in which sound is absorbed by the acoustic covering system according to the invention.

[0071] As it appears from Fig. 1 (a), the acoustic covering system in the closed state has aligned surfaces on the side wall portion and the rear wall. When the acoustic covering system is in the open state, as shown in Fig. 1 (b), only narrow side openings between adjacent boards will be visible to the audience seated in the room, at the side edges of the respective boards.

[0072] In the renderings shown in Figs. 1(a) and 1(b) the ceiling of the room is provided with a traditional sound absorbing system comprising numerous through openings that are clearly visible to an audience. Compared to traditional systems, the acoustic covering system of the invention vastly improves the visual appearance of the room in both states of the invention.

[0073] Figs. 2(a) and (b) show renderings of the acoustic covering systems mounted on boundaries (a portion of a side wall and on the back wall) of a room; specifically, Fig. 2(a) shows the acoustic covering systems in a closed state, in which sound is not absorbed by the acoustic covering system according to the invention, and Fig. 2(b) shows the same systems as in Fig. 2(a), but in an open state, in which sound is absorbed by the acoustic covering system according to the invention. In this embodiment several smaller boards are used on the upper part of the wall areas, close to the ceiling in order to create a higher degree of sound absorption due to more opened area for the sound to enter per area unit wall.

[0074] It is understood that the acoustic covering system as shown in the following figures when installed in a room can be oriented as desired relative to those boundaries on which they are installed. Thus, the orientations shown in the various Figs, are generally non-limiting.

[0075] Figs. 3 (a) to (d) show different tilting patterns of the boards 6 relative to the solid structure 2 (e.g. a frame). In Figs. 3(a) and (b) the respective boards 6 are configured to be able to undergo a tilting movement about a hinge member 15 provided at the interface between the board 6 and the solid structure 2 such that the boards in Fig. 3(a) in the open state of the acoustic covering system open at the bottom whereas the boards in the embodiment shown in Fig. 3(b) in the open state of the acoustic covering system open at the top. In Fig. 3(c) and (d) corresponding pivotal movements of the boards are obtained about a pivot axis 25 of the boards. Each of the boards 6 may have a respective pivot axis 25. The respective pivot axis 25 may be either arranged along a side of the board for hinging and tilting (cf. Figs. 3 (a) and (b)), or may be arranged lengthwise through the center of the respective board 6 to symmetrically rotate the board 6 (cf. Figs. 3 (c) and (d)).

[0076] Fig. 4 shows a schematic perspective view of a box-like shaped solid structure 2 having side portions 2i , 22, 2s, 24. Fig. 4 shows a schematic perspective view of the face of the acoustic covering system, where the face is the side of the acoustic covering system that, when installed on a boundary of a room faces the space containing the audience and performers for instance at a live concert. It is understood that even though the side portion 2i as seen in Fig. 2 could be regarded as the upper portion of the acoustic covering system, i.e., the portion of the acoustic covering system that when installed in a room faces the ceiling of the room, the side portions 2i , 22, 2s, 24 could have any orientation along given boundaries of a room, such that side portion 2i for instance in a specific room could face downwards towards the floor of the room.

[0077] The solid structure 2, when in use, is mounted to a boundary B of a room such that the boxlike solid structure 2 and the boundary B define an inner cavity (also called space herein), in which a sound absorbing means is provided. At the face 3 of the box-like structure 2 there are provided divider bars 4 such that a number of through openings 45 are formed in the box-like structure through which sound can pass into the inner cavity, when the acoustic covering io system is in the open state. In the closed state, the respective boards 61 , 62, ... 612 closes the corresponding through openings acoustically tight. The front faces of the respective boards are indicated by F, where the front face F is the face of the boards 6 that, when the acoustic covering system is installed on boundaries of a room, faces the interior of the room in which for instance an audience and an orchestra or band or soloist is situated.

[0078] The acoustic covering system can be divided in single cells which can be opened and closed by the corresponding single board (e.g. 61), such that sound energy in the open state of the acoustic covering system can reach the interior of the solid structure 2 in which a cavity is formed that is at least partly filled with the sound absorbing means (i.e. a sound absorbing material) that are effective at least the 125 Hz octave band.

[0079] The acoustic covering system comprises in Fig. 4 a total of twelve boards 6 provided in two rows R1 and R2, but it is understood that the acoustic covering system is not limited to this number of boards 6. The boards 6 are attached to the box-like solid structure 2 by hinge members 15 or pivot axes 25 in such a manner that the boards 6 can undergo a tilting movement relative to the face 3 of the solid structure 2. In the open state of the acoustic covering system, all boards 6 are tilted as shown, such that the boards 61, 63, 65, 67, 69, 611 are tilted by the dimension di than the remaining boards 62, 64, 6e, 6s, 610, 612 that are tilted as indicated by the dimension d2. For example, d2 is greater than di . For example, d2 is 1 ,25 times (or 1 ,5 times or 2 times) greater than di .

[0080] It is understood that this tilting pattern is only a non-limiting example, and reference is for instance made to Fig. 5(a) and (b) that show another example of a tilting pattern.

[0081] Fig. 5(a) shows a schematic perspective view of the acoustic covering system comprising boards 61, 63, 65, 6s, 610, 612 that are permanently fixed to the solid structure 2 (and hence cannot be opened) as well as boards 62, 64, 66, 67, 69, 611 that can be tilted between a closed state and an open state, where e.g., the tilt angle for some of the boards 6 may be larger than for other boards 6. Note that the closed state and the open state can be referred to as the position of the boards and the overall situation of the acoustic covering system.

[0082] Specifically Fig. 5(a) shows the acoustic covering system in the open state seen from a position in front of and slightly to the left of the acoustic covering system and Fig. 5(b) shows the same system seen from a position facing the front of the acoustic covering system.

[0083] With reference to Fig. 5(a) and (b) there is shown the acoustic covering system seen from a point in front of and slightly from the left of the acoustic covering system as visualized by the (x, y, z) coordinate system shown in both Fig. 5(a) and 5(b). The acoustic covering system shown in Fig. 5(a) and 5(b) comprises a total of twelve frame sections 35 (see also Fig. 6) and associated boards 61 , 62, ... 612. It is however understood that the acoustic covering system may comprise more or less than the twelve boards 6 and corresponding through openings in the face 3 of the solid structure 2 or frame according to the specific requirements in a given room. The acoustic covering system shown in Figs. 5(a) and (b) comprises two rows R1 and R2 of frame sections 35 and associated boards 6, but it is understood that other numbers of rows R could also be used according to the invention. The acoustic covering system may for instance cover an entire wall or only a portion of a wall of a room. Also, one or more of the walls of the room may be covered by one or more acoustic covering systems. It is also possible, and often desirable either in addition to or as an alternative to wall mountings to cover at least one or more portions of the ceiling of the room with the acoustic covering systems.

[0084] The acoustic covering system comprises boards 61, 63, 65, 6s, 610 and 612 that are fixedly connected to the solid structure 2 and thereby permanently closing the corresponding frame sections. Between each of the boards 61, 63, 65, 6s, 610, 612 movable (in Figs. 5(a) and 5(b) tiltable) boards 62, 64, 6e, 67, 69 and 611 are provided. As illustrated by the different tilt angles in Fig. 3(b), the movable boards 6 can be opened to a different extend thereby inter alia providing sound reflection in different directions in the room in which the acoustic covering system is installed. A more detailed description of the boards and the movements of these are given below with reference to Figs. 7 to 9.

[0085] Fig. 5(b) shows the same system as in Fig. 5(a) in the open state of the acoustic covering system, in which a substantial sound absorption in the 125 Hz octave band can be obtained, but seen directly towards the front face of the acoustic covering system that, when the acoustic covering system is installed in a room, faces the interior of the room, where seats for an audience and / or an orchestral podium of stage is present, when the room is used for instance for live concerts.

[0086] In the figures shown in this detailed description the acoustic covering system is planar, as shown extending in in the (x, z) plane. The invention is however not limited to planar systems. The acoustic covering system according to the invention could alternatively or in combination with planar systems be non-planar, for instance curved, for example in order to more closely correspond to the shape of the boundaries of a specific room. The basic features of a curved system would correspond to those of the planar system described herein but with the necessary changes of the shapes of the frame structure, frame sections and associated boards.

[0087] Fig. 6 shows a specific (but non-limiting) example of a solid structure 2 in the form of a rigid frame structure with openings through which sound can enter the space between the frame and the boundary, on which the frame is mounted, and in which space sound absorbing means are provided.

[0088] With reference to Fig. 6 there is shown a non-limiting example of a solid structure 2 (here a frame) consisting of a number of frame sections 35 each configured to be provided with a corresponding associated board 61, 62, ... 612.

[0089] Fig. 7 shows the mechanism of the board 6j being tilted over a hinge member 15 relative to the solid structure 2. Fig. 7 shows a schematic side view of a single cell of the acoustic covering system, where the associated board 6; is connected to the single section of the solid structure 2 (here frame section) by means of the hinge member 15, such that the associated board 6i can pivot between the open state (as shown in Fig. 7) and a closed state in which it closes the corresponding frame section in such a manner that sound is effectively prevented from passing through the frame section. The frame section has a first face 4 facing the associated board 6j and a second face 5 facing the boundary B upon which the acoustic covering system is installed. The frame section of the solid structure 2 is attached to the boundary B by appropriate attachment members 13 thereby creating an internal space S between the frame section of the solid structure 2 in which sound absorbing means 12 (a sound absorber) are provided. The associated board 6j is connected to the frame section of the solid structure 2 by a hinge member 15, such that the associated board 6j can undergo a tilt movement as indicated by the tilt angle a-, between an open state (as shown in Fig. 7) and a closed state in which the board closes the through opening in the frame section of the solid structure 2, such that sound is effectively prevented from passing through this opening into the space S.

[0090] The board 6j is further attached to a joint 9, which is connected to an electrical drive 11 by means of a rod 10. The electrical drive 11 can move the rod 10 in one direction, where the tilt of the board 6j relative to the solid structure 2 is achieved by the rod 10 being attached to the joint 9 and the board 6j being attached to the hinge member 15 at a side of the frame section of the solid structure 2.

[0091] As shown in Fig. 7, the board 6j may comprise a front plate (or panel) 7 made for instance of fiberboard attached to a cover plate 8 made for instance of steel or other stiff material (at a rear side facing the boundary B in closed state). This material can for instance be a magnetic material to be attracted by a magnetic force, where the solid structure 2 may also comprise corresponding magnetic material.

[0092] Fig. 8 shows the mechanism of the board 6j being tilted relative to the solid structure without the use of a hinge member 15. In Fig. 8, for the drive mechanism the rod 10 is retracted by the electrical drive 11 until the cover plate 8 contacts the first face 4 of the frame section of the solid structure 2, where the joint 9 attached to the cover plate 8 can pivot relative to the rod 10, while the tilt angle cn decreases and reaches a value of zero, when the board 6; is fully retracted and the acoustic covering system is in the closed state. The magnetic means can secure an acoustically tight closing. Another way to obtain this is by employing gaskets between the board 6; and the solid structure 2.

[0093] Fig. 9 shows the mechanism of the board 6; being displaced relative to and in parallel with the front of the frame section of the solid structure 2. In the open state of the acoustic covering system, a gap of width d is formed between the board 6j and the frame section of the solid structure 2 through which gap sound can enter in the inner space S containing the sound absorbing means 12. Fig. 9 can also be viewed as a top-down illustration thus panels are here angled sideways directing sound energy to either the front or end of the room rather than towards the ceiling or floor.

[0094] Fig. 10 shows a schematic perspective view of a single frame section 35 of the solid structure 2 (such as the frame shown in Fig. 4) and the associated board seen from above in which the tilt angle a is deliberately shown larger than what is typically used in practice in order to more clearly show corresponding contact region 22 on the frame section 35 and contact region 23 on the associated board 6. In Fig. 10, the frame section 35 is illustrated as a single individual section, but in most practical implementations of the invention, the acoustic covering system comprises a frame structure comprising a plurality of such sections formed as an integral part of the solid structure 2 (frame structure).

[0095] In the closed state of the acoustic covering system, it is important that the boards 6 effectively prevent sound (e.g. by means of damping material) from entering the inner cavity (space S) travelling through the through openings 45 formed by the solid structure 2. In order to obtain a substantially acoustically tight closing the contact region 22 on the frame section 35 may be provided with magnetic means, such as a magnetic ribbon, extending all the way around the through opening 45 and the corresponding contact region 23 on the board 6 must in this case be made of or provided with a material that will be attracted by the magnetic force from the magnetic means in contact region 22. As an alternative to such magnetic means, suitable mechanical means may be provided on the respective contact regions 22, 23, such that these means enter into engagement with each other, when the board 6 is closed and thereby provides the required acoustically tight closing of the through opening 45 in the frame section 35.

[0096] Figs. 11(a) and (b) show the boards being respectively pivoted about parallel displaced axes 25 such that, in the open state of the acoustic covering system, an upper portion of the board is tilted outwards relative to the solid structure and a lower portion of the board is tilted inwards into the solid structure.

[0097] In the open state (a) and in the closed state (b), in which the boards 6 can pivot about an axis 25 such that, in the open state of the acoustic covering system, an upper portion of the board is tilted outwards relative to the solid structure of the acoustic covering system and a lower portion of the board is tilted inwards into the solid structure of the acoustic covering system and towards the sound absorbing means 12 provided in the cavity formed between the boards 6 and the boundary B of the room. The boards 6 can pivot about the respective pivot axis 25 as indicated by a between the open state shown in Fig. 9(a) and the closed state shown in Fig. 9(b).

[0098] In order to allow one longitudinal portion of the respective boards 6 to pivot into a connected and aligned solid structure, the sound absorbing means are placed at a distance Di from the rear surface of the boards 6. The sound absorbing means 12 does not have to occupy the entire remainder of the cavity between the boards 6 (in the closed state hereof) and the boundary B, but can be placed at a distance D2from the boundary B. In practice, the thickness t of the sound absorbing means can be thicker than 50 and / or thinner than 150 mm.

[0099] It is understood that even though the boards 6 in Fig. 11 could be regarded as the upper portion of the acoustic covering system, i.e., the portion of the acoustic covering system that when installed in a room faces the ceiling of the room, the side portions 2i , 22, 22, 24 could according to the invention have any orientation along given boundaries of a room, such that side portion 2i for instance in a specific room could face downwards towards the floor of the room.

[0100] In order to obtain an acoustically tight closing as well as a substantially un-broken surface of the acoustic covering system facing for instance an audience in the room in which the acoustic covering system is installed, corresponding overlapping portions 26, 27 are provided in corresponding end portions of respective adjacent boards. In these overlapping portions 26, 27 there can for instance be provided magnetic or mechanical means as described above. This means that also the axes 25 may be fixed at a ceiling and a bottom of the room such that the parallel axes 25 have a predetermined distance to each other and extend from bottom to ceiling of the room. The distance may be one board length. The boards 6 then open sideways.

[0101] Fig. 12 shows a plot of sound absorption coefficient as a function of frequency that illustrates the sound absorbing effect of persons either standing or sitting in a room. Exemplary sound absorption coefficients obtained by a system of the above kind with tilted boards in the closed and the open state of the acoustic covering system in the 125 Hz, 250 Hz, 500 Hz, 1000 Hz, 2000 Hz and 4000 Hz octave bands are shown below: f(HZ) Sound absorption coefficient

[0102] Closed State Open State

[0103] 125 0.10 0.75

[0104] 250 0.08 0.55

[0105] 500 0.05 0.40

[0106] 1000 0.05 0.40

[0107] 2000 0.05 0.40

[0108] 4000 0.05 0.40

[0109] In addition to the high sound absorption coefficient in the important 125 Hz octave band, the acoustic covering system according to the invention, where the board is angled, tilted or pivoted downwards, has a further important advantage which is described with reference to Fig. 12 that shows of the sound absorption coefficient as a function of frequency caused by persons either standing or sitting in a room. As it appears from Fig. 12 the effect of persons such as an audience at a musical performance is to introduce a very high sound absorption in the frequency range from approximately 500 Hz and upwards. Even though a controlled RT at 125 Hz is the most important factor, it is however desirable, if the RT in this mid and high frequency region could be reduced more than what is obtained solely by the open boards, and this can in fact be obtained by the particular embodiment of the invention consisting of downward tilted panels. The reduction is obtained by tilting or pivoting the boards such that the front surface of these, in the open state of the acoustic covering system, reflects sound impinging on the tilted front surfaces of the boards towards the areas in which the audience is seated during a performance.

[0110] Thereby, the invention provides both the required high sound absorption coefficient in the important 125 Hz octave band and a suitable sound absorption coefficient in the mid and high frequency bands. This effect is explained below with reference to Fig. 13(a) and (b).

[0111] Figs. 13(a) and (b) show a schematic cross-sectional view of a room in which a single board of the acoustic covering system is shown with the purpose to explain the method according to the invention. Fig. 13(a) shows a schematic cross-sectional view of a room with ceiling, front wall, floor and rear wall. Part of the floor is occupied by an audience and in front of the audience there is a sound source, which for instance could be a band playing music and thereby generating sound energy both at low, medium and high frequencies. A part of the sound generated by the sound source will be emitted directly towards the audience as indicated by Doin Figs. 13(a) and (b) and a part of the generated sound will be emitted in other directions such as Di and D5 respectively in the Figs. 13(a) and (b).

[0112] In Fig. 13(a) the boards (only one of which is shown for simplicity) are angled / tilted upwards (they could alternatively be angled sideways), and the sound that hits the walls will be reflected around between walls and ceiling (at the speed of sound) as indicated by D1 , D2, D3 and D4, and this propagation of sound will take some time, thereby creating a long RT.

[0113] In Fig. 13(b) the boards (only one of which is shown for simplicity) are tilted downwards whereby the sound energy is reflected from the front face F of the boards downwards towards the audience who absorbs approx. 5 times more HF than LF (cf. Fig. 12). The RT especially at HF is thereby decreased compared to a situation where the boards were angled upwards or sideways as shown in Fig. 13(a).

[0114] With the boards tilted downwards towards the sound absorptive audience, the sound energy is immediately reflected to the audience who then absorb especially the HF. Hence RT in the room especially at HF is reduced more than what the absorption coefficients I the above table suggests especially at HF, since those absorption coefficients were measured in a reverberation chamber without any HF absorptive audience on any surface. This corresponds to achieving a higher absorption coefficient of the acoustic covering system at HF.

[0115] Thus, with the boards tilted downwards, already after the first reflection from the walls, sound is absorbed (mostly HF) by the audience, and thus especially the first part of the sound decay will be affected. The time it takes for the sound to decay from 0 dB to -10 dB is often referred to as the Early Decay Time (EDT) also referred to as the “running reverberation". It is mainly the EDT that will be lowered by the downward reflecting panels which is important, since the first 10 dB decay of the reverberation is the decay, you hear the most clearly in the room, whereas later parts of the sound have a sound pressure level below the level of the sound pressure level of the sound / music experienced by the audience and performers.

[0116] Further, Fig. 14 (a) shows a schematic perspective view of single frame section 35 of the acoustic covering system. The frame section 35 as shown in Fig. 14(a) can be considered a unit cell or single cabinet with a single space S (confined when installed at the boundary B). These single frame sections 35 can be arranged next to each other in a row (as shown in Fig. 14(b)), where several surfaces and / or the boards 61 , 62 and 63 are aligned with each other. The single spaces Si , S2 and S3 can be separated from each other, e.g., which may be different from a whole space S as defined by the whole solid structure 2 (e.g. in Fig. 4).

[0117] Finally, Fig. 15 shows a photo of an acoustic covering system on the floor, Fig. 16 shows a photo of an acoustic covering system without boards on the wall; Fig. 17 shows a photo of a board with a steel plate and mounted actuators; and Fig. 18 shows certified measurement results.

[0118] At this point it should be noted that all of the above-described parts are considered to be essential to the invention on their own and in any combination, especially the details shown in the drawings. Modifications of this are familiar to the skilled person.

Claims

CLAIMS1. An acoustic covering system for covering at least parts of a boundary (B) of a room, the acoustic covering system being configured to provide variable sound absorption, where the acoustic covering system comprises: a solid structure (2) configured to be attached to the boundary (B), such that the solid structure (2) and the boundary (B) form a space (S); and one or more boards (6) attached to the solid structure (2) and configured to selectively move relative to the solid structure (2), such that, in an open state of the acoustic covering system, one or more respective openings (45) are created between the one or more boards (6) and the solid structure (2) on at least part of a circumference of the respective one or more boards (6) to enable sound energy to pass through and reach sound absorbing means (12) within the space (S) between the one or more boards (6) and the boundary (B), wherein the sound energy is absorbed in the open state of the acoustic covering system to lower the reverberation time, RT, in the room when the acoustic covering system is installed.

2. The acoustic covering system according to claim 1 , wherein the solid structure (2) comprises a plurality of sections (35) enabling sound energy to pass through from a first side (4) of the solid structure (2) to an opposite second side (5) of the solid structure (2); for each of the plurality of sections (35) an associated board (6) is configured to move relative to the corresponding section (35) in a direction away from the internal space (S), in such a manner that in a closed state of the acoustic covering system, the associated board (6) closes the corresponding section (35) such that sound energy is prevented from passing through the section (35) and in an open state of the acoustic covering system, the associated board (6) opens for the sound energy to pass through the respective one of the openings (45) formed between the associated board (6) and the corresponding section (35) such that the sound energy passes through the section (35) from the first side (4) of the solid structure (2) to the internal space (S); and wherein the opening (45) formed between the respective associated board (6) and the corresponding section (35) is obtained by tilting or pivoting the respective associated board (6) at an angle (a) relative to the corresponding section (35), where the angle (a) is > 0 degrees, where the respective angle (a) for different associated boards (6) varies.

3. The acoustic covering system according to claim 1 or 2, wherein each of the sections (35) comprises a first contact region (22) and the associated board (6) comprises a second contact region (23) that in the closed state of the acoustic covering system overlaps the first contact region (22) on the corresponding frame section (35) such that an acoustically tight closing is obtained between the associated board (6) and the corresponding section (35) in the closed state of the acoustic covering system.

4. The acoustic covering system according to claim 3, wherein the surface of the board (6) that faces the solid structure (2) is provided with a cover plate (8) made of steel adapted to be attracted by a magnetic force, and wherein the first contact region (22) on the corresponding frame section (35) is provided with magnetic means configured to attract the cover plate (8) and to maintain an acoustically tight contact between the board (6) and the corresponding section (35) in the closed state of the acoustic covering system.

5. The acoustic covering system according to claim 3 or 4, wherein the first contact region (22) is provided with magnetic means, such as a magnetic ribbon, and the second contact region (23) is provided with means that is / are attracted by the magnetic force from the magnetic means provided in the first contact region (22) or vice versa.

6. The acoustic covering system according to any of the preceding claims, wherein the solid structure (2) and the boards (6) are substantially planar when the acoustic covering system is in the closed state.

7. The acoustic covering system according to any of the preceding claims, wherein the boards (6) are single unperforated panels.

8. The acoustic covering system according to any of the preceding claims, wherein one edge portion of each respective board (6), in a condition when the board (6) is tilted, remains in contact with the corresponding portion of the respective section of the solid structure (2).

9. The acoustic covering system according to any of the preceding claims, wherein individual boards (6) in the open state of the acoustic covering system are tilted or pivoted by an individual tilting angle (a), whereby the sizes of the individual openings (45) between the respective boards (6) and the corresponding sections (35) of the solid structure (2) vary from each other in the open state of the acoustic covering system.

10. The acoustic covering system according to any of the preceding claims, wherein the acoustic covering system is provided with one or more tilting mechanisms that are configured to allow all boards (6) of the acoustic covering system to be tilted using one single drive means (11), such as an electric motor, pneumatic motor or the like.

11. The acoustic covering system according to any of the preceding claims, wherein the acoustic covering system is provided with one or more tilting mechanisms that are configured to allow one or more subsets of boards (6) of the acoustic covering system to be tilted using one drive means (11) for each subset of boards (6), such as an electric motor, pneumatic motor or the like.

12. The acoustic covering system according to any of the preceding claims, wherein the tilt angle (a) of the individual boards (6) is determined based on the direction in which sound reflection is to be directed, when the acoustic covering system is installed in the room.

13. The acoustic covering system according to any of the preceding claims, wherein the width of the one or more boards (6) is either between 70 and 140 cm or 170 and 240 cm, and wherein a depth of the solid structure (2) is between 0,1 m and 0,25 m.

14. The acoustic covering system according to any of the preceding claims, wherein the boards are angled with respect to the solid structure (2) between the closed state and the open state of the acoustic covering system between an angle of 0 and 60 degrees, in particular less than 20 degrees.

15. The acoustic covering system according to any of the preceding claims, wherein directly neighboring boards (6) are angled differently to each other and / or are spaced apart by at least 4 cm.

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