AT526400B1 - Building board - Google Patents

Abstract

Building board (1), in particular wall or ceiling board, with sound absorption properties, which has a top side and a bottom side, wherein a plurality of sound entry recesses (2) are arranged on the top side facing the sound or visible side, and wherein each sound entry recess has a width, wherein each sound entry recess has a wall (5) which is essentially perpendicular to the top side and borders on an edge surrounding the sound entry recess, and wherein the majority of at least 85% of the sound entry recesses have a mouth bevel (6) which is in a predetermined angular range with one or more angles a at least in a partial section of the edge to the respective wall, wherein the angles a deviate from 90°, wherein the angle or angles a between mouth bevels of the majority of the sound entry recesses and the walls in the partial section of the edges is or are between approximately 70° and 85°, or wherein the angle a between the mouth bevel and the wall of a first partial section of the edge is between approximately 70° and 85° and along a second portion of the edge between approximately 95° and 140°.

Description

Description

BUILDING PLATE

[0001] The invention relates to a building board, in particular a wall or ceiling board, with sound absorption properties, which has a top side and a bottom side, wherein a plurality of sound entry recesses are arranged on the top side on the sound or visible side, and wherein each sound entry recess has a width, wherein each sound entry recess has a wall which is substantially perpendicular to the top side and which borders on an edge surrounding the sound entry recess, and wherein the majority of at least 85% of the sound entry recesses have a mouth bevel which is in a predetermined angular range with one or more angles a at least in a partial section of the edge to the respective wall, wherein the angles a deviate from 90°.

[0002] In the prior art, sound-absorbing panels for indoor or outdoor use are often provided with holes, depressions, wave structures or grooves in order to absorb or redirect sound waves in the audible range of about 20 Hz to 20 kHz. Panels of this type are used in meeting rooms, other common rooms in buildings, in halls or performance halls as wall or ceiling cladding to improve the room acoustics, usually to limit acoustic reverberation effects.

[0003] It is known in particular to provide the visible flat surface of a base plate with a large number of vertical holes in order to allow at least a portion of the sound to be lost therein or to superimpose reflected sound components with incoming sound components in a way that cancels them out. Although building panels of this type are simple and inexpensive to manufacture, the quantitative effect of sound absorption is not high and there is still a need to increase the sound absorption properties.

[0004] US2018090122 discloses a sound-insulating panel in which a large number of penetrating slots are arranged in a panel, whereby the walls of the slots are not always perpendicular to the panel plane. The absorber performance is thereby shifted upwards by about an octave in the frequency response, but without improving the overall absorber performance in any way.

[0005] WO0203375A1 teaches a sound-insulating body covered with a micro-perforated film. The sound-absorbing effect of this object is narrow-band and overall not particularly high.

[0006] EP2540926A1 shows a sound insulation panel in which micro-slots with steep walls are attached. The funnel-shaped walls have a very steep, completely circumferential angle and are based on a different vibration model than the one discussed here (see below). The disadvantage is that the high angles and the other geometric shapes of the micro-slots can be attached using complex manufacturing processes. The absorber performance is also narrow-band and not very high.

[0007] AT515748A1 comprises a sound-insulating construction panel in which there are a large number of large circular sound entry recesses. The absorption performance is increased by the invention in the low frequency range.

[0008] US2005104245 A1 shows a method for applying microperforation, which does not work particularly well compared to larger dimensioned sound entry recesses.

[0009] WO 2018085249 A1 shows several geometries for sound entry recesses that have walls that are given a rather random geometry with sharp edges on the top through a melting process. This has a reduced effect on sound absorption.

[0010] GB 2361718 A, US 2015267402 A1, DE 1868072 U, KR 200334976 Y1, DE 202019000997 U1, DE 19536562 A1 and DE 102004040112 A1 show recesses which only

consist of slanted walls and thus only work for a narrow frequency band. DE 102007040034 A1 and EP 1020846 A2 show step-shaped recesses without bevels, which are also not very effective. EP 3300073 A1 discloses sound entry recesses with curved walls, and US 2280631 A teaches recesses with vertical walls in the lower section, but concave curved areas in the upper section; both are difficult to produce.

[0011] The invention aims to create a building board as mentioned at the beginning, which achieves improved sound absorption properties with simple manufacturing steps. The sound-absorbing effect should be high over wide frequency ranges of the audible spectrum. The solution should be cost-effective and durable.

[0012] The building board according to the invention achieves this in that the angle or angles a between the mouth bevels of the majority of the sound entry recesses and the walls in the partial section of the edges is or are between approximately 70° and 85°, or wherein the angle a between the mouth bevel and the wall of a first partial section of the edge is between approximately 70° and 85° and along a second partial section of the edge is between approximately 95° and 140°.

[0013] A further embodiment of the invention consists in that the angle a between the bevel of the mouth of the building board and the wall in the section of the edge is between about 70° and 85° or between about 95° and 140°. These angle ranges are easy to produce and tests have shown that the sound absorption is high.

[0014] More specifically, the angle a between the bevel of the building board and the wall in the section of the edge may be between about 75° and 85° or between about 95° and 120°. These angle ranges are again easier to manufacture and tests have shown that the sound absorption is even higher.

[0015] It has also proven advantageous that more than 85% of the sound entry recesses have a bevelled opening and the remaining minority of the sound entry recesses have an edge to the top of the building board with an angle a of approximately 90°. This ensures that a clear majority of the openings achieve the desired effect and the absorption performance is improved compared to previously known panels.

[0016] Furthermore, it is provided that the remaining minority of the sound entry recesses have a beveled opening with an angle a of approximately 85° to approximately 95°. This ensures that the absorption performance is improved compared to previously known panels.

[0017] In one embodiment, the width of all sound entry recesses of a building board is about 0.1 mm to about 2.5 mm. This also increases the sound absorption properties.

[0018] A further embodiment of the invention consists in that the depth of all sound entry recesses of a building board is approximately 0.3 mm to approximately 6 mm, whereby the depth is simultaneously the thickness of the building board between the top and bottom. This measure increases both the sound absorption properties and facilitates the manufacturing process.

[0019] More specifically, the width of the mouth bevel may be approximately 0.8 to 1.8 times the width of the sound entry recesses. This also increases the sound absorption properties.

[0020] It has also proven advantageous that the width of the sound entry recesses is simultaneously their diameter, which can be easily produced by the drilling process step.

[0021] Furthermore, it is provided that the sound entry recesses are elongated, with the length being 2 to 100 times, preferably about 15 times, their width (B). This simplifies production and the sound-insulating effect is retained.

[0022] A further embodiment of the invention consists in improving the sound-insulating effect in that the sound entry recesses are provided in orderly rows on the upper side, wherein the distances between adjacent sound entry recesses within a row are approximately 0.5 to 2 times the length of the sound entry recesses or, in the case of circular sound entry recesses, approximately 1.5 to 10 times the diameter.

[0023] More specifically, the sound entry recesses may be provided in orderly rows on the upper side, the distances between adjacent rows being approximately 0.5 to 2 times the length of the sound entry recesses or, in the case of circular sound entry recesses, approximately 1.5 to 10 times the diameter.

[0024] Alternatively, the sound entry recesses are randomly distributed on the upper side.

[0025] It has also proven advantageous that the proportion of the sum of the areas of the sound entry recesses to the total area of the top side is approximately 2% to 10%, preferably approximately 5% to 8%. This advantageously achieves a balance between high sound absorption and reduced manufacturing costs.

[0026] Furthermore, it is provided that the building board comprises wood, lignified grasses, a light metal such as aluminum or plastic, which advantageously enables a high variability of model series for the building boards.

[0027] In one embodiment, the building board consists of wood fiberboard, chipboard, or plywood, which allows the appearance to be adapted to existing rooms.

[0028] A further embodiment of the invention consists in that it is connected to a carrier element on the rear side, whereby a cavity is formed between the underside of the building board and the carrier element, whereby the cavity preferably has a depth of approximately 3 to 20 times the depth D of the building board. As a result, sound waves are partially absorbed, particularly in the audible range.

[0029] It is further provided that the cavity is formed by the carrier plate designed as a honeycomb plate, perforated plate or coarse-pored foam. This makes the construction plate even more mechanically stable.

[0030] Further advantages and embodiments of the invention emerge from the description and the drawings. The invention is explained in more detail below with reference to embodiments shown in the drawings. They show: Fig. 1 and 2 each show schematic sections through a section of a building board with a sound entry recess, Fig. 3 and 4 each show a frequency diagram, Fig. 5 two sections from a section through a building board and Fig. 6 to 8 each show a schematic oblique view through a section of a building board.

[0031] Regarding the acoustics and the physical model of a sound entry recess 2 on a surface 3 according to e.g. Fig. 1 or 2, it is known that if the width B of the recess (or diameter in the case of circular openings) is very small in relation to the acoustic wavelength, so-called Helmholtz effects come into play. "Small" means in the example

200 Hz = 0.6 m wavelength A

and

according to Fig. 1 a width B of the opening in the area with vertical wall 5 B < 2.5 mm

a relationship

A:B > 240

This effect is called microperforation. In contrast to larger openings, where the sound energy is directed into a layer behind it for absorption, here the air itself (in, in front of and behind the opening in a possible

cavity) is stimulated to vibrate. Since air also has mass and thus inertia, a mass-spring system is created, which ultimately destroys sound energy, or more physically correctly converts it into thermal energy.

[0032] A disadvantage of this effect is that the absorption ranges that can be achieved are relatively narrow. By designing the opening cross-sections, said range can be shifted, but it still remains relatively narrow.

[0033] With larger widths B of the sound entry recesses 2 (or openings), a funnel geometry is occasionally used to direct more sound, just like with a funnel, into the layers behind. With small opening sizes, where there is a ratio of \:B > 240, this makes no sense, since the introduction of sound is not the aim there.

[0034] Extensive series of tests have shown that the opening effect at the small openings changes dramatically when the adjacent surfaces are not at 90° to the opening axis, as is usual with micro-perforated surfaces, but at a different angle, for example 75°-110°. This phenomenon results in a significant increase in the absorption area and thus in the absorption performance. The diagram in Fig. 3 illustrates this by forming the area integral under the frequency-dependent absorption curve, which, as can easily be seen, is many times greater than with conventional micro-perforations. The effect is also even greater due to the logarithmic x-axis.

[0035] While non-planar surface areas, such as a full-circumferential and arbitrarily inclined surface, between the individual openings are known and used to influence the diffuse reflection, only the immediately adjacent, specifically inclined areas, namely the width S of the mouth bevels 6, are relevant for the surprising effect of the invention for increased absorption.

[0036] The physical explanation is that sound vibrations in air in the form of longitudinal waves can, viewed locally, also be represented as pressure fluctuations. The above-mentioned vibration of the air in the opening area is caused by and results in a change in the local flow speed. However, since air is not an "ideal gas", this change does not occur abruptly, but rather areas of different isobars form in a dome shape above the sound entry recesses 2. The inventive mouth bevels 6 in turn result in the formation of overlapping isobar domes. In interaction with the primary ones present, interference and cancellation effects now occur, which are surprisingly responsible for the extraordinary effectiveness.

[0037] A distinction is clearly made between this and macroscopic bevels, funnels, etc. The described effect of the air being excited to vibrate can primarily develop in the small opening dimensions mentioned, in which an intentionally small proportion of the sound waves actually runs into the sound entry recesses 2, but the remaining proportion develops the effect just described. In larger openings (sound entry holes with larger widths B and the smaller ratio A:B < 240 and below), such bevels have the effect of a funnel, which directs as many sound waves as possible into an absorber placed behind it. Although the proportions are similar, the fundamentally different scale means that completely different physical mechanisms are at work.

[0038] In connection with the area of micro-perforation in question here, it is also sufficient if not all, but only a sufficiently large proportion of the sound entry recesses 2 are bevelled, and if the mouth bevels 6 also only affect part of the peripheral edge of a sound entry recess 2. This circumstance can be used to take into account any statistically occurring differences in the geometry of the sound entry recesses 2 depending on the building board material and the manufacturing process, but ultimately to allow for the efficiency to be achieved here.

(see embodiments of Fig. 6 to 8).

[0039] The diagram in Fig. 3 shows its exemplary product geometry in a test bench, called an "alpha cabin". An absorption coefficient a (without units or [1]) of an optimal structure (dotted line) is shown as an example to illustrate the absorption coefficient in comparison to the state of the art (solid and dashed lines). For the exemplary structure of a building board according to the invention, the parameters are selected as follows:

B = 0.5 mm; D= 3 mm; L= 5 mm (length of the slots),

a= 105° ... 45% share,

a = 80° ... 40 % share,

a= 90°... 15 % share,

Share of open area 6.6% of the total area of building panel 1.

[0040] The area integral under the absorber curves, expressed in aHz, is the fictitious absorber power for visualizing the performance of the individual variants, rounded to whole 100s. For the building board according to the invention in the diagram of Fig. 3, it is

1700 aHz.

[0041] The solid line corresponds to the performance of US2018090122 “prior Art”; the dashed line corresponds to the performance of US2018090122 “present”.

US2018090122 “prior Art” = 800 aHz, US2018090122 “present” = 900 aHz.

[0042] This already shows the advantage of the invention. In Fig. 4, which also shows absorption curves of three plates in comparison, the performance is compared with a conventional micro-perforated plate in which the edges of the sound entry recesses are 90° (solid line). The parameters are:

B = 0.5 mm; D= 3 mm; L= 5 mm, a = 90° approximately 100% share, share of open area 6.6%.

[0043] This would result in a power of approximately 850 aHz and additionally the disadvantage of narrow band (peak of absorption at about 1000H2Z).

[0044] The absorption curve of a building board according to the invention with the same parameters as in Fig. 3 is again shown in dotted lines in Fig. 4. An alternative building board according to the invention with a different distribution of the mouth bevels 6 is shown in dashed lines. The distribution is (with otherwise identical parameters to the dotted line):

a= 105° ... 25% share,

a= 100° ... 25% share,

a= 85°... 25% share,

a= 80°... 25 % share.

[0045] The performance is therefore very similar in frequency response and in the area integral.

[0046] The sound entry recesses 2 can be produced by milling, punching, water jets, laser cutting, compressed air granulate cutting or the like. This can be selected depending on the material of the building board 1 and/or its surface. The material or the substance of a building board 1 is essentially not relevant for the special effect of the sound entry recesses. In terms of vibration technology, materials with a bulk density in the range of 300 to 2700 kg/m? have proven to be effective. The materials in question are therefore plastics, wood materials, solid wood and light metals. Wood materials also include lignified grasses,

such as bamboo and the like. A first method step therefore consists in providing a raw material for a building board 1 with regard to the external dimensions and any coatings and in a second step producing the sound entry recesses 2 initially without mouth bevels 6. For this purpose, the shape, number and distribution of the sound entry recesses 2 are taken from a model and implemented by drilling, milling, embossing, water jets, laser cutting or punching. Alternatively, at least some sound entry recesses 2 already have sufficient mouth bevels 6 on parts of their edges in the sense of the invention, i.e. those with the above-mentioned angle ranges.

[0047] The mouth bevels 6 can be created by milling or similar machining or chip-removing processes, by compressed air granulate blasting, embossing or compacting, or in the case of solid wood by brushing. The brushing result can be achieved, for example, by a special sequence of one to four process steps using different brush materials. Starting with steel strands, followed by brass, Andalorn and nylon bristles.

[0048] The arrangement of the sound entry recesses 2 in the surface of a building board 1 works over a wide range. An arrangement in rows that are evenly spaced from one another and in which the recesses are the same distance from one another is, however, easier in serial production and is often preferred for optical reasons for installation. For the highest sound-insulating effect, the sound entry recesses 2 must be evenly distributed over the surface. The proportion of open area through the recesses is around 1-10%, preferably 3-8% and more preferably 6.6% of the total area for a high effect.

[0049] The rows can be aligned synchronously or offset from each other. Both alternatives work equally well in terms of sound absorption properties.

[0050] The opening geometry for a sound entry recess 2 can be designed in different ways. Tests have shown that the width B of a sound entry recess 2, always measured in the area with a vertical wall 5, is 0.1-2.5 mm, preferably 0.5-1.5 mm. The depth D of a sound entry recess 2 is then 0.3-6 mm, preferably 0.8-4.5 mm and particularly preferably 1.5-3.5 mm. The mouth bevel S is ideally 0.8 to 1.8 times the width B. The angle a between wall 5 and the mouth bevel, which should deviate from 90°, preferably from the range 85°-90°, in both directions, is, according to the test results, 70°-140° (excluding 90°) and preferably 75°-120° (excluding 85°95°).

[0051] The manufacturing process will preferably not produce the sound entry recesses 2 individually by pressing, embossing, brushing, machining or punching, but in large numbers at the same time, with the exact opening geometry only corresponding to the specified data in a statistical manner. In serial manufacturing processes, such as jet cutting, the sound entry recesses are alternatively not produced simultaneously, but individually, but in rapid succession one after the other. This statistical distribution can also occur here. However, this does not have a detrimental effect on the sound absorption function (and on the aesthetic design) of the building board 1. The proportion of sound entry recesses 2 whose angle a falls within the range of 85°-95° to be avoided should, however, be less than 15% of all sound entry recesses 2 in a building board 1.

[0052] According to Fig. 5, the mouth bevels 6 can be concave or convex. This can be caused by a manufacturing process, such as brushing wood materials. Even such shapes do not limit the sound-insulating effect of the sound entry recesses 2. In order to be able to determine and achieve the desired angular range of the angle a, one decides on the central tangent 7 of the curved mouth bevel 6 in order to obtain a straight line and to intersect with the line of the wall 5.

[0053] As illustrated in Fig. 7, the angle a of the mouth bevel 6 of a sound entry recess 2 can be changed from a section smaller than 90° to a section larger than 90°.

The particularly high sound-dim- ening effect is retained, even despite an intermediate, short section of the muzzle bevel 6 in which the angle a is close to or equal to 90°.

[0054] The sound entry recess 2 can have a round cross-section or be provided as an elongated slot as shown in Fig. 6 to 8. The maximum length of such a slot is limited to 20 mm, preferably to 15 mm, so that the building board 1 is not mechanically unstable, i.e. at risk of breakage. The shape of the slot ends is not primarily relevant for the acoustic effect and can therefore be left dependent on the manufacturing process, depending on whether it is easier to provide the slot ends with a bevel 6, or to leave a 90° edge, or to make the slot ends rectangular or with a radius in plan view.

[0055] For the distances between the sound entry recesses 2, the values for within a row, between the rows or the average distances in the case of an arbitrary, disordered distribution of all sound entry recesses 2 result from the open area (sum of the area of the sound entry recesses 2) and the desired proportion in % of the area of the building board 1.

[0056] If the sound entry recesses 2 are provided as slots, these can be straight or curved or have other geometries. From the point of view of simple production, straight sound entry recesses 2 are suitable, and for reasons of consistency or desired contrast with the room environment of the installed panels, curved or similar are also possible. With regard to the acoustic effect, no differences could be measured depending on these alternatives.

[0057] The mouth bevel 6 does not need to be linear/straight across its width S, but can be random as indicated in Fig. 8. As described above, such shapes can arise from brushing uneven wood materials, but do not impair the sound-insulating effect and can be tolerated. As a result, the angle a and the width S of the mouth bevel 6 vary at a sound entry recess 2. It is important that the angle a lies within the ranges described here as effective.

[0058] The building plate 1 is advantageously part of a higher-level structure in that it rests on a base construction. It must be ensured that there is a more or less self-contained air space behind the building plate 1 described above with the sound entry recesses 2. This means that either a box-shaped construction (not shown) is built in which the building plate 1 is firmly connected to a base plate and there is a predefined cavity between the two. Its depth (seen in the same spatial direction as the depth D of the building plate 1) is then matched to the depth D of the building plate 1. The cavity serves the small proportion of sound waves that enter the sound entry recesses 2. Even with the optional provision of a cavity behind the building plate 1, the formation of the mass-spring system and Helmholtz effect is also supported.

[0059] Or one chooses the mechanically more stable, because more torsionally rigid, alternative in which the building board 1 is held by a honeycomb structure or by (hardened) e.g. coarse-pored foam material. The building board 1 lies directly on the second, hollow-containing structure.

[0060] By varying the volume behind the building board 1, i.e. on the opposite underside 4, an acoustic fine-tuning of the frequency response can be achieved, but this would be the subject of another invention.

LIST OF REFERENCE SYMBOLS

1 building board

2 Sound entry recess

3 Top

4 Bottom

5 Wall

6 Muzzle bevel

7 Central tangent

B Width of a sound entry recess D Depth of a sound entry recess Ss Width of a muzzle bevel

a angle

Claims (17)

Patent claims 1. Building board, in particular wall or ceiling board, with sound absorption properties, which has a top side and a bottom side, wherein a plurality of sound entry recesses are arranged on the top side facing the sound or visible side, and wherein each sound entry recess has a width, wherein each sound entry recess has a wall (5) which is substantially perpendicular to the top side and borders on an edge surrounding the sound entry recess, and wherein the majority of at least 85% of the sound entry recesses (2) have a mouth bevel (6) which is in a predetermined angular range with one or more angles a at least in a partial section of the edge to the respective wall (5), wherein the angles a deviate from 90°, characterized in that the angle or angles a between mouth bevels (6) of the majority of the sound entry recesses (2) and the walls (5) in the partial section of the edges is or are between approximately 70° and 85°, or wherein the angle a between Mouth bevel (6) and wall (5) of a first partial section of the edge is between approximately 70° and 85° and along a second partial section of the edge is between approximately 95° and 140°. 2. Building board according to claim 1, characterized in that the angle or angles a between the mouth bevels (6) of the majority of the sound entry recesses (2) and the walls (5) in the partial section of the edges is or are between approximately 75° and 85° or between approximately 95° and 120°. 3. Building board according to one of claims 1 or 2, characterized in that more than 85% of the sound entry recesses (2) have a mouth bevel (6) and the remaining minority of the sound entry recesses (2) have an edge to the upper side (3) of the building board (1) with an angle a of approximately 90°. 4. Building board according to claim 3, characterized in that the remaining minority of the sound entry recesses (2) have a mouth bevel (6) with an angle a of approximately 85° to approximately 95° over their entire circumference. 5. Building board according to one of claims 1 to 4, characterized in that the width (B) of all sound entry recesses (2) of a building board (1) is approximately 0.1 mm to approximately 2.5 mm. 6. Building board according to one of claims 1 to 5, characterized in that the depth (D) of all sound entry recesses (2) of a building board (1) is approximately 0.3 mm to approximately 6 mm, wherein the depth (D) is simultaneously the thickness of the building board (1) between the top side (3) and the bottom side (4). 7. Building board according to one of claims 1 to 6, characterized in that a width (S) of the mouth bevel (6) is approximately 0.8 to 1.8 times the width (B) of the sound entry recesses (2). 8. Building board according to one of claims 1 to 7, characterized in that the width (B) of the sound entry recesses (2) is simultaneously their diameter. 9. Building board according to one of claims 1 to 7, characterized in that the sound entry recesses (2) are elongated, the length being 2 to 100 times, preferably about 15 times, their width (B). 10. Building board according to one of claims 1 to 9, characterized in that the sound entry recesses (2) are arranged in rows on the upper side (3), the distances between adjacent sound entry recesses (2) within a row being approximately 0.5 to 2 times the length of the sound entry recesses (2) or, in the case of circular sound entry recesses (2), approximately 1.5 to 10 times the diameter. 11. Building board according to one of claims 1 to 10, characterized in that the sound entry recesses (2) are arranged in rows on the upper side (3), the distances between adjacent rows being approximately 0.5 to 2 times the length of the sound entry Recesses (2) or in the case of circular sound entry recesses (2) should be approximately 1.5 to 10 times the diameter. 12. Building board according to one of claims 1 to 9, characterized in that the sound entry recesses (2) are randomly distributed on the upper side (3). 13. Building board according to one of claims 1 to 12, characterized in that the proportion of the sum of the areas of the sound entry recesses (2) to the total area of the upper side (3) is about 2% to 10%, preferably about 5% to 8%. 14. Building board according to one of claims 1 to 13, characterized in that it comprises wood, lignified grasses, a light metal such as aluminum, or plastic. 15. Building board according to claim 14, characterized in that it consists of wood fiber boards, chipboards, or plywood. 16. Building board according to one of claims 1 to 15, characterized in that it is connected to a carrier element on the rear side, a cavity being formed between the underside (4) of the building board (1) and the carrier element, the cavity preferably having a depth of approximately 3 to 20 times the thickness D of the building board (1). 17. Building board according to claim 16, characterized in that the cavity is formed by the carrier plate designed as a honeycomb plate, perforated plate or coarse-pored foam, which rests directly on the underside (4) of the building board (1). 5 sheets of drawings