EP3935624B1 - Sound absorber, structure and use of a sound absorber - Google Patents

Description

The invention relates to a sound absorber with an open-pored base plate according to claim 1.

Sound absorbers of this type are used, for example, to optimize room acoustics in buildings, vehicles or aircraft. Furthermore, the invention relates to a use of such a sound absorber according to claim 13.

Sound absorbers are known from practice which contain or consist of a porous material. The porous material can be provided in the form of a fleece, a foam or a fiber layer and can be introduced into a room, for example. Known examples are wall or ceiling elements which absorb sound at least in a definable frequency range and can thereby reduce the reverberation. This can improve the intelligibility of speech or the perception of musical performances.

Other well-known sound-absorbing constructions have a micro-perforated and shapeable layer on the surface, which is combined with a perforated panel. The perforated plate only has the necessary mechanical stability and is perforated so that the sound can penetrate through the perforation to an absorbing layer behind the plate to be absorbed. This makes the construction thicker and, with three layers, complex to manufacture. EP0046559 A2 discloses resonator sound absorption elements consisting of a hollow body with at least one resonator surface structure dividing the cavity space, as well as those consisting of a hollow body on whose peripheral edge a resonator surface structure covering the cavity mouth is fastened. 1

However, these known sound absorbers have the disadvantage that the possibilities for optical design are limited and as a result aesthetic compromises often have to be made for acoustic optimization. Proceeding from the state of the art, the invention is therefore based on the object of providing a sound absorber which also meets high design requirements.

The object is achieved according to the invention by a use according to claim 13 and a device according to claim 1. Advantageous developments of the invention can be found in the dependent claims.

According to the invention, a sound absorber with an open-pored base plate is proposed. The porosity is a dimensionless parameter that indicates the ratio of the cavity volume to the total volume of the base plate. The base plate should be regarded as open-pored if it has cavities which are connected to one another and to the environment. The open porosity thus allows hydraulic transport of fluids in the base plate.

According to the invention, the open-pored base plate should have a flow resistance of about 500 Ns/m ³ to about 6000 Ns/m ³ according to DIN EN 29053:1993-05. This flow resistance means that sound waves can penetrate the base plate and are converted into heat there through dissipation. The base plate thus has a sound-absorbing effect in at least part of the acoustic frequency range.

According to the invention it is now proposed that at least a partial area of the base plate with a micro-perforated Material layer is provided. In embodiments of the invention, the partial surface is a surface of the base plate that faces the outside during later use.

The outside is understood to be a surface that is visible when used as intended. In other embodiments of the invention, the base plate can be completely provided with the microperforated material layer. This primarily means that the entire surface of the base plate is covered by the micro-perforated layer of material. However, the microperforated material layer is not bonded to the entire surface. Rather, this is only connected in the form of strips, lines or points in order to enable surface vibrations of the micro-perforated material layer.

The microperforated material layer has a plurality of bores which, on the one hand, allow a sound wave to penetrate into the open-pored base plate lying behind the microperforated material layer. On the other hand, the holes in the micro-perforated material layer themselves act like a damped resonator, ie the micro-perforated material layer has higher sound absorption than the open-pored base plate without a micro-perforated material layer, depending on the diameter of the holes or holes and depending on the thickness at a specific frequency or frequency band . The inventive combination of the two layers, ie the open-pored base plate and the micro-perforated material layer, results in a new acoustic behavior, so that the absorption of the base plate is retained in principle, but the absorption is generally improved at low frequencies. Through the design of the micro-perforated material layer the acoustic behavior of the structure can also be specifically influenced. In addition, the holes in the micro-perforated material layer can be so small be chosen so that they can no longer be resolved by the eye of an observer from a normal viewing distance of, for example, more than approximately 1 m to more than approximately 3 m and appear optically smooth. As a result, wall coverings or facade elements or partitions or furniture surfaces can appear optically smooth and closed in a manner known per se, although they have a completely different acoustic behavior than a smooth surface.

In some embodiments of the invention, the base plate of the sound absorber can have a flow resistance of more than approximately 2000 Ns/m ³ according to DIN EN 29053:1993-05. As a result, the sound absorption can be improved. In some embodiments of the invention, the base plate can have a flow resistance of approximately 2000 Ns/m ³ according to DIN EN 29053:1993-05.

In some embodiments of the invention, the baseplate may have an open porosity of from about 30% to about 99%, or from about 40% to about 80%, or from about 45% to about 60%. This open porosity allows reliable sound absorption, so that the sound absorber according to the invention can have high degrees of absorption and only a small proportion of sound is reflected.

In some embodiments of the invention, the base plate can have a thickness of from about 6 mm to about 100 mm, or from about 50 mm to about 200 mm, or from about 7 mm to about 80 mm, or from about 8 mm to about 40 mm, or from about 10 mm to about have 30 mm. In this way, the conflicting goals between low weight and low space requirements, mechanical stability and good sound absorption can be optimized.

In embodiments of the invention, the microperforated material layer is integrally connected to the base plate, in particular the microperforated material layer with the Base plate glued, soldered or welded. In some embodiments, which are not part of the invention, the microperforated material layer can be joined to the base plate over its entire surface. As a result, the mechanical stability of the sound absorber can be increased.

In embodiments of the invention, the microperforated material layer is only joined to the base plate in the form of strips or lines or only at certain points, for example by gluing, soldering or welding. As a result, the microperforated material layer can execute bending vibrations or surface vibrations, with the base plate being able to act as an additional spring element of a mass/spring system formed in this way, in addition to the inherent rigidity of the microperforated material layer. The natural frequencies of the vibrations of the microperforated material layer can be influenced by the number, size and/or position of the joints. Additional energy can be withdrawn from the sound field by the vibrations of the microperforated material layer, in particular also in frequency ranges in which the absorption of the base plate and/or the effect of the microperforation is only low. As a result, the vibration of the microperforated sheet of material as a whole can complement the effect of the absorber in some embodiments.

In some embodiments not forming part of the invention, the microperforated sheet of material may be spaced apart from the base plate. The distance can be between about 1 mm and about 10 mm or between about 3 mm and about 8 mm in some embodiments of the invention. In this embodiment, the natural vibration of the microperforated material layer can be less damped by the base plate, so that the effect of the absorber can be increased.

In some embodiments of the invention, the microperforated sheet of material can have a thickness of from about 0.1 mm to about 0.1 mm 2 mm, or from about 0.5 mm to about 1.8 mm, or from about 0.8 mm to about 1.5 mm, or from about 1 mm to about 4 mm, or from about 1 mm to about 2 mm. Such a microperforated material layer can on the one hand optimize the sound absorption and/or on the other hand give the sound absorber high stability with low weight.

In some embodiments of the invention, the microperforated material layer has a plurality of bores, the diameter of which is between about 0.1 mm and about 2 mm, or between about 0.3 mm and about 1.2 mm, or between about 0.4 mm and about 0.8 mm or between about 0.8 mm to about 2.0 mm. In some embodiments of the invention, all of the holes in the microperforated material layer can have a uniform diameter. In other embodiments of the invention, the bores in the microperforated material layer can have different diameters or a distribution function of the diameters. As a result, the absorption maximum can be optimized to a predeterminable frequency or a predeterminable frequency range, so that the sound absorber can, for example, selectively dampen room resonances.

In some embodiments of the invention, the area proportion of the bores of the microperforated material layer can be between 0.1% and about 10% or between about 1% and about 9% or between about 5% and about 8% of the total area. On the one hand, this enables the optical impression of a closed or largely closed surface and, on the other hand, sufficient sound absorption, so that the sound absorber according to the invention can be used to optimize the room acoustics or to optimize the acoustic properties of a facade.

In other embodiments of the invention, the area percentage of the bores of the microperforated material layer can be between about 0.005% and about 2% or between about 0.01% and about 1% of the total area. This enables the microperforation to be used as a broadband low-frequency absorber. In some embodiments of the invention, this can have a resonant frequency of less than 120 Hz or less than 80 Hz. In some embodiments of the invention, the resonant frequency of the microperforation can be chosen so that it is above the natural frequency of the surface vibration of the microperforated material layer and below the absorption maximum of the base plate.

In some embodiments of the invention, the distance between adjacent bores in the microperforated material layer can be chosen to be between about 15 mm and about 100 mm or between about 20 mm and about 60 mm.

In some embodiments of the invention, the microperforated sheet of material may include or consist of a melamine resin and/or a thermoset and/or a thermoplastic and/or a wood veneer and/or polyethylene and/or polyethylene terephthalate and/or ethyltetrafluoroethylene copolymer and/or a metal or alloy .A metal or alloy may contain or consist of aluminum or steel. Such layers of material enable, on the one hand, a decorative design of wall or ceiling surfaces or also furniture surfaces or facades and, on the other hand, are sufficiently mechanically stable to enable the sound absorber to have a long service life. In addition, layers of material with low internal friction, such as metals, can supplement the effect of the absorber in some embodiments by vibrating the microperforated layer of material as a whole.

In some embodiments of the invention, the sound absorber can contain multiple base plates. These can have different properties, for example contain different materials and/or have different thicknesses and/or different ones have porosities. In some embodiments of the invention, the sound absorber can contain at least two base plates, with at least one base plate being arranged on each side of the microperforated material layer. In some embodiments, this may be spaced on one or both sides.

In some embodiments of the invention, the baseplate may be self-supporting. This makes assembly and transport of the base plate easier. For purposes of this specification, "self-supporting" means that the panel does not require any additional mechanical substructure or support or bracing for the desired application. The panel is therefore so rigid and stable that it can only be attached to individual attachment points and yet its shape does not change significantly over time, e.g. on the ceiling as ceiling cladding or on the wall as wall cladding. In the case of wall cladding in the movement area of students in schools or in sports halls, a cladding panel must also withstand mechanical forces such as impact by people. A non-self-supporting slab, on the other hand, always requires a substructure that absorbs the forces that occur in order to keep the slab in shape permanently in a certain position.

In some embodiments of the invention, the base plate can be a pressed polyester fleece and/or a wood material and/or pressed mineral wool and/or sintered glass foam and/or cement-bonded expanded clay and/or a duroplastic foam and/or a melamine resin and/or a natural fiber material and/or contain or consist of a metal foam. The base plates are therefore open-pored in order to have good acoustic properties. In addition, such base plates can also be mechanically stable so that they are not damaged during handling and assembly. In some embodiments According to the invention, the material of the base plate can be selected in such a way that it complies with the usual fire resistance classes and allows use in or on buildings without complex approval in individual cases.

In some embodiments of the invention, the sound absorber can contain at least one mechanical reinforcement element, which contains or consists of, for example, GRP and/or CFRP and/or polyethylene and/or polyester and/or wood or a wood-based material. In some embodiments of the invention, the reinforcement element can also contain or consist of a metal or an alloy. Such a reinforcement member can improve the mechanical strength of the sound absorber, thereby facilitating assembly and transportation. For this purpose, the reinforcement element can be applied as a grid or fabric layer to the outer surface of a sound absorber, in some cases above the microperforated material layer or also between the microperforated material layer and the base plate. In other embodiments of the invention, the reinforcement element can be embedded in the base plate.

In some embodiments of the invention, the sound absorber can be fixed in a basket on a building wall or a building ceiling. Such a basket can contain or consist of a perforated plate. Optionally, the basket can be closed at the side.

In some embodiments of the invention, the sound absorber can be introduced into at least one room of a building. This can be done as a wall or ceiling element, which can absorb sound at least in a definable frequency range and thereby reduce the reverberation. The intelligibility of speech or the perception of musical performances in the building can be improved by using the sound absorber. In some embodiments of the invention, the sound absorber can be attached to at least one partial surface of at least one outer facade of a building. As a result, sound of at least one predefinable frequency range can be absorbed and the reverberation can thereby be reduced. The use on a facade is particularly advantageous in inner courtyards or atriums or on streets with heavy traffic, in order to reduce acoustic disturbances in the adjacent interior rooms or to expand the possible uses of the inner courtyard or atrium, for example as a meeting place.

• Figur 1 einen Schallabsorber in einer ersten Ausführungsform, welche nicht Teil der Erfindung ist.
• Figur 2 zeigt einen Schallabsorber in einer zweiten Ausführungsform.
• Figur 3 zeigt in einem ersten Vergleichsbeispiel den Absorptionsgrad gegen die Frequenz.
• Figur 4 zeigt in einem zweiten Vergleichsbeispiel den Absorptionsgrad gegen die Frequenz.
• Figur 5 zeigt in einem dritten Vergleichsbeispiel den Absorptionsgrad gegen die Frequenz.
• Figur 6 zeigt in einem vierten Vergleichsbeispiel den Absorptionsgrad gegen die Frequenz.
• Figur 7 zeigt einen Schallabsorber gemäß der vorliegenden Erfindung in einer dritten Ausführungsform.
• Figur 8 zeigt einen Schallabsorber in einer vierten Ausführungsform.
• Figur 9 zeigt einen Schallabsorber in einer fünften Ausführungsform.
• Figur 10 zeigt einen Schallabsorber in einer sechsten Ausführungsform.
• Figur 11 zeigt in einem fünften Vergleichsbeispiel den Absorptionsgrad gegen die Frequenz.
• Figur 12 zeigt den Einfluss der Mikroperforation auf den Absorptionsgrad.

The invention is to be explained in more detail below with reference to figures without restricting the general inventive idea. The first, second, fourth, fifth and sixth embodiments of the sound absorber are not part of the invention. It shows:

• figure 1 a sound absorber in a first embodiment which is not part of the invention.
• figure 2 shows a sound absorber in a second embodiment.
• figure 3 shows the degree of absorption versus frequency in a first comparative example.
• figure 4 shows the degree of absorption versus frequency in a second comparative example.
• figure 5 FIG. 12 shows the degree of absorption versus frequency in a third comparative example.
• figure 6 Figure 12 shows absorptivity versus frequency in a fourth comparative example.
• figure 7 shows a sound absorber according to the present invention in a third embodiment.
• figure 8 shows a sound absorber in a fourth embodiment.
• figure 9 shows a sound absorber in a fifth embodiment.
• figure 10 shows a sound absorber in a sixth embodiment.
• figure 11 Figure 12 shows absorptivity versus frequency in a fifth comparative example.
• figure 12 shows the influence of microperforation on the degree of absorption.

Based on figure 1 a first exemplary embodiment of a sound absorber not according to the invention is explained in more detail. Shown is a building part 5, for example a wall or ceiling surface, which can be made of masonry or concrete, for example. The building part 5 delimits an interior space of a building. Due to the smooth surface of building part 5, disturbing sound reflections and long reverberation times can occur in this interior.

A sound absorber not according to the invention is used to improve the acoustic comfort. This contains a base plate 1, which for example has a thickness of about 6 mm to about 100 mm and which in some embodiments contains or consists of a pressed polyester fleece, a wood material, pressed mineral wool, sintered glass foam, cement-bonded expanded clay or a duroplastic foam. As a result, the base plate is at least partially open-pored and has a flow resistance of approximately 2000 Ns/m ³ .

The base plate 1 can be flat or curved. This allows the base plate to be shaped to complement the area of the building to which it is to be applied.

The base plate 1 can be applied directly to the surface of the building part 5, for example by gluing or by mechanical fasteners, such as screws and dowels. In other embodiments, the base plate 1 can be arranged at a distance from the building part 5, resulting in an optional intermediate space 4 which has a height of about 2 cm to about 20 cm or from about 2 cm to about 40 cm or from about 5 cm to about 10 cm.

In order to ensure the mechanical stability of the base plate 1, it can have optional reinforcement elements 15. The reinforcement element 15 can, for example, be embedded in the base plate 1 in the form of an elongate stiffener or a lattice. In addition, the reinforcement element 15 can be used as a holder in order to reliably fasten the sound absorber to the building part 5 . In other embodiments of the invention, the base plate itself can have sufficient mechanical stability, so that reinforcement elements 15 can also be omitted.

The intermediate space 4 can optionally be completely or partially filled with sound-absorbing material.

At least the partial area of the base plate 1 that is visible when used as intended is provided with a micro-perforated material layer 2 . The layer of material 2 contains a plurality of bores or holes 20, which can be arranged in a regular or irregular pattern and which can each have a diameter of about 0.1 mm to about 2 mm. The total area of the bores 20 can be about 0.1% to about 10% of the total intended use correspond to the visible surface of the sound absorber.

In the first embodiment, the microperforated material layer 2 is connected to the base plate 1 over its entire surface, for example by gluing. The micro-perforated material layer can consist of plastic, wood or metal and thus enable the desired surface design of the sound absorber.

The back of the base plate 1 facing the building part 5 or the intermediate space 4 is not provided with a microperforated material layer 2 .

In this embodiment, the microperforated material layer 2 is not capable of vibrating itself due to its connection to the base plate 1, i.e. the sound absorber is based on the following mechanisms of action: On the one hand, sound waves can penetrate through the microperforated material layer 2 into the base plate 1 and be dissipated there. This mechanism of action dominates at higher frequencies. On the other hand, the air enclosed in the bores 20 of the microperforated material layer 2 can be excited to vibrate by impinging sound waves and thereby dissipate energy from the sound field. This mechanism of action dominates at lower frequencies. In some embodiments, it can also be omitted or only slightly pronounced. Both mechanisms of action can therefore have different absorption spectra and thus complement each other.

In other embodiments, the sound absorber shown, ie the base plate 1 with optional reinforcement elements 15 and the microperforated material layer 2 applied over the entire surface, can also be used for other applications than the ceiling panel shown, for example as wall cladding or as the interior paneling of a vehicle or aircraft, as a mobile partition wall or in furniture construction or as a facade element of a building.

figure 2 shows a second embodiment of a sound absorber. Identical components are provided with the same reference symbols, so that the following description is limited to the essential differences.

figure 2 shows a section of the cross section through a base plate 1. This is provided not only partially, but over the entire surface with a micro-perforated material layer 2. The microperforated material layer 2 thus also covers the side edges and the side of the base plate 1 facing the building part 5.

Furthermore is off figure 2 It can be seen that the optional reinforcement elements 15 are not embedded in the base plate, but are introduced as a grid between the micro-perforated material layer 2 and the base plate 1. The reinforcement element 15 can thus also be connected to the base plate by gluing or welding.

In this embodiment, too, the microperforated material layer 2 is not itself capable of vibrating due to its connection to the base plate 1 or the reinforcing element 15, i.e. the sound absorber is based, like the first embodiment, on the following mechanisms of action: On the one hand, sound waves can pass through the microperforated material layer 2 into the base plate 1 penetrate and be dissipated there. On the other hand, in some embodiments, the air enclosed in the bores 20 of the microperforated material layer 2 can also be excited to vibrate by impinging sound waves and thereby dissipate energy from the sound field. Both Mechanisms of action can have different absorption spectra and thus complement each other.

The in the Figures 1 and 2 The first and second embodiments shown are collectively referred to as sound absorbers of the first type because of their identical mechanisms of action. Based on the below Figures 3 - 6 Comparative examples between different sound absorbers of the first type against known sound absorbers are explained.

Also the in figure 2 The sound absorber shown, ie the base plate 1 with optional reinforcement elements 15 and the micro-perforated material layer 2 applied over the entire surface can be used as a wall or ceiling panel of a building, as an interior paneling of a vehicle or aircraft, as a mobile partition wall or partition or in furniture construction or as a facade element.

figure 3 shows a first comparative example of a sound absorber. The degree of absorption is shown on the ordinate and the frequency of incoming sound on the abscissa. Here, curve A shows the degree of absorption of a sheet known per se made of a melamine resin foam with a thickness of 10 cm. Curve B shows the same base plate made of melamine resin foam with a thickness of 10 cm, which, however, was additionally provided with a micro-perforated material layer glued over the entire surface on the entry side of the sound.

How out figure 3 As can be seen, the sound absorption in the range from about 100 Hz to about 300 Hz is improved by the micro-perforated material layer, so that in addition to an aesthetic surface design there is also an improved effect of the sound absorber.

figure 4 shows a second comparative example. As in the ones described below Figures 5 and 6 is again the degree of absorption of a pressed mineral wool panel on the ordinate and the frequency on the abscissa. Curve A shows the degree of absorption of a mineral wool panel with a thickness of 2 cm, which was mounted in front of a building part 5 with a gap 4 of 10 cm. Curve B again shows the degree of absorption after the mineral wool board has been provided with a micro-perforated material layer over its entire surface. How out figure 4 As can be seen, the absorption behavior of the sound absorber does not deteriorate, with improved optical and aesthetic properties at the same time.

Based on figure 5 a third comparative example will be explained. In this case, curve A shows absorbance versus frequency for a pressed polyethersulfone (PES) web. The fleece has a thickness of 5 cm and is mounted at a distance or gap 4 of 5 cm from the building part 5 .

In this case, too, curve B shows the degree of absorption versus frequency for the nonwoven after it has been provided with a microperforated material layer that has been bonded over its entire surface. In this case, too, there is higher absorption in the range from about 150 to about 250 Hz, so that the sound absorber not only has improved optical properties, but also improved acoustic properties in the low-frequency range.

In the fourth comparative example according to figure 6 the identical pressed fleece layer is used as in the in figure 5 example shown. However, this is mounted at a greater distance of 10 cm from the surface of part 5 of the building. This changes the absorption behavior, especially for frequencies above about 800 Hz. Curve B again shows the fleece provided with a microperforated layer of material.

figure 7 shows a sound absorber according to the present invention in a third embodiment. Identical components are provided with the same reference symbols, so that the following description is limited to the essential differences.

The third embodiment also has a base plate 1 which contains or consists of, for example, an open-pore foam, a fiber layer, a knitted fabric, a knitted fabric or another sound-absorbing material known per se. The base plate 1 is designed with open pores so that sound waves can penetrate and their energy is dissipated in the base plate.

The base plate 1 is attached to a building part 5, for example a ceiling or an inner wall or an outer wall. The side of the base plate 1 opposite the part of the building is provided with a micro-perforated material layer 2 . In contrast to the first and second embodiments described above, the microperforated material layer 2 according to the third, fourth, fifth and sixth embodiment is not connected to the base plate 1 over its entire surface. Rather, the microperforated material layer is connected to the base plate in the form of strips, lines or points. In some embodiments, which are not part of the invention, J the connection can only take place via the edges, so that the surface of the micro-perforated material layer 2 has no connection to the base plate 1.

In still other embodiments, which are not part of the invention, there can be no mechanical or material connection between the microperforated material layer 2 and the base plate 1 . This feature enables surface vibrations of the microperforated material layer 2. In addition to the two above in connection with the Mechanisms of action described in the first and second embodiment, the third, fourth, fifth and sixth embodiments can also dissipate sound energy in that the microperforated material layer as a whole is excited to surface vibrations and thus dissipates energy from the sound field. For this purpose, the microperforated material layer in the third embodiment can have a thickness of approximately 1 mm to approximately 4 mm or of approximately 1 mm to approximately 2 mm. The microperforated material layer preferably has low internal damping and is made, for example, from a metal, an alloy or a duroplast. In some embodiments of the invention, the micro-perforated material layer 2 can be a sandwich construction made of several material layers in order to adapt the vibration behavior to desired target values.

The microperforated material layer 2 has holes 20 which have a diameter of about 0.8 mm to about 2 mm and a distance between adjacent holes of about 15 mm to about 100 mm. As a result, the microperforation can be tuned as a broadband low-frequency absorber with a resonant frequency of less than approximately 150 Hz or less than approximately 80 Hz. The broadband effective low-frequency absorber is therefore mainly effective in the low-frequency range. This is followed by the resonance of the surface vibration of the microperforated material layer 2 . Finally, in the high-frequency range, the absorption of the base plate 1 is decisive for the absorption behavior. Since the figure 7 Third embodiment shown thus combines three mechanisms of action in a single sound absorber, this is in contrast to the basis of Figures 1 and 2 described embodiments hereinafter referred to as sound absorbers of a second type.

The base plate 1 and/or the microperforated material layer 2 can be attached to the building part 5 in a basket 6 . The basket 6 can, for example, from a wire mesh or be made of perforated sheet metal and be open or closed at the edges. The basket 6 can optionally contain a trickle guard, which can be designed as a flow layer. Since the basket 6 provides the sound absorber with mechanical stability, there is greater freedom in the selection of the base plate 1 in an embodiment with such a basket 6. This does not necessarily have to be designed to be self-supporting. However, it should be noted that the basket 6 is optional and may be omitted in other embodiments of the invention.

In other embodiments of the invention, the sound absorber shown, i.e. the base plate 1 with optional reinforcement elements 15 and the micro-perforated material layer 2 connected to the base plate in the form of strips, lines or points, can also be used for applications other than the ceiling panel shown in or on a building, for example as a Interior paneling of a vehicle or aircraft, as a mobile partition or partition or in furniture construction.

Based on figure 8 a fourth embodiment is explained in more detail. Identical components are provided with the same reference symbols, so that the following description is based on the essential differences from the above with reference to FIG figure 7 described third embodiment limited.

How out figure 8 As can be seen, the microperforated material layer 2 does not lie on the base plate 1. Rather, there is a distance 7 between the base plate 1 and the microperforated material layer 2. In some embodiments, this distance can be between approximately 1 mm and approximately 10 mm or between approximately 3 mm and approximately 8 mm. This feature has the effect that the natural vibration of the micro-perforated sheet of material is less influenced by the base plate, so that the effect of the absorber can be increased. However, the air volume enclosed between the microperforated material layer 2 and the building part 5 in the base plate 1 still acts as a restoring force on the vibration of the microperforated material layer 2, so that the selection of the distance 7 also affects the natural frequency of the material layer 2 and thus the absorption behavior of the sound absorber can be optimized or adjusted.

Based on figure 9 a fifth embodiment which is not part of the invention will be described. The fifth embodiment differs from the third embodiment in that the basket 6 is enlarged so that a porous foam, a knitted fabric, a knitted fabric or a fiber layer can be arranged on both sides of the microperforated material layer 2 . Starting from the surface of the building part 5, the base plate 1 is thus initially arranged directly on the surface of the building part 5. The microperforated material layer is applied to the side of the base plate 1 opposite the building part 5, as described above. A first additional board 11 comes to rest on the side of the microperforated material layer 2 opposite the base board 1 . An optional second additional plate 12 is applied to the first additional plate 11 . Impinging sound energy is thus initially absorbed by the first and second supplementary panels 11 and 12 . Low frequencies, which can pass through the additional panels 11 and 12, excite the microperforated material layer 2 to surface vibrations, which absorb further sound energy in the medium frequency range. Low frequencies below about 80 Hz can be absorbed by the air volume enclosed in the bores 20 of the micro-perforated material layer 2. If high-frequency vibrations still reach the base plate 1, they are absorbed there. Essentially, however, the base plate 1 serves to dampen the vibrations of the microperforated material layer 2 and to dissipate energy.

Since the microperforated material layer 2 is in contact both with the first additional plate 11 and with the base plate 1, an additional mechanical or cohesive attachment by gluing, soldering or welding can be omitted. The four in figure 9 Material layers shown can be held in the basket 6 solely by its own weight and attached to the building part 5 with it.

Based on figure 10 a sixth embodiment, which is not part of the invention, is explained in more detail. figure 10 shows a cross section through a sound absorber. The sixth embodiment is a combination of the fifth embodiment described above with the fourth embodiment.

How out figure 10 As can be seen, the sixth embodiment also includes at least a first additional plate 11 and an optional second additional plate 12, which can be made of a different material and/or have a different thickness, so that the additional plates 11 and 12 have an absorption maximum at different frequencies. Also in the fifth embodiment described above, the material properties of the first and second auxiliary plates 11 and 12 can be appropriately selected.

The main difference between the sixth embodiment and the fifth embodiment is that there is a distance 7 between the base plate 1 and the microperforated material layer 2 and/or between the microperforated material layer 2 and the first additional plate 11 . The distance 7 can be between about 1 mm and about 10 mm, for example. For this purpose, the microperforated material layer 2 is connected to the basket 6 by holding elements 25 . As a result, the microperforated material layer 2 can oscillate freely and thus with a larger amplitude and/or less damping and thus dissipate a higher proportion of the incoming sound energy.

Based on figure 11 the effect of the sound absorber is explained in a fifth comparative example. The degree of absorption is again plotted on the ordinate and the frequency on the abscissa. Curve A shows an absorber according to the prior art, which has a structure similar to that in figure 9 shown sound absorbers. The sound absorber according to figure 9 has a base plate 1, in front of which an oscillatable material layer 2 is arranged. In addition, a further base plate 11 and/or base plate 12 is arranged in front of the material layer 2 . However, the material layer 2 does not have any microperforations or bores 20 . How

figure 11 shows, this sound absorber has a first resonant frequency at about 125 Hz. At about 150 Hz, an undesired minimum of the absorption behavior is formed. The absorption of the base plate 11 and/or 12 only takes effect at significantly higher frequencies from about 200 Hz. By applying the microperforation according to the invention in the material layer 2, the absorption behavior changes as shown in curve B with an otherwise unchanged structure. How out figure 11 As can be seen, the resonance shifts to lower frequencies, in the present example to around 80 Hz. The resonance becomes broader and less pronounced. The minimum of the absorption behavior visible in curve A is largely smoothed out by the microperforation according to the invention.

Based on figure 12 the effect of the microperforation in a sound absorber of the second type is explained again in a sixth comparative example. Curve C again shows the absorption behavior a sound absorber, which is approximately according to the structure figure 7 with a basket closed at the side, but has no bores 20 or no microperforations in the material layer 2 . The material layer 2 consists of a sheet steel with a thickness of 1.25 mm. The base plate 1 contains a melamine resin foam and has a thickness of 100 mm. How out figure 12 As can be seen, such a known sound absorber exhibits a strong increase in the absorption behavior at a resonance frequency of approximately 100 Hz. The absorption behavior drops sharply on both sides of the resonance frequency.

Curves D and E show the absorption behavior of a nominally identical sound absorber, which, however, has been provided with the microperforation according to the invention. The sound absorbers according to curves D and E thus have all three mechanisms of action which characterize the second type of sound absorber. Depending on the number or the spacing of the holes, the resonant frequency of the microperforated material layer 2 can be shifted to higher or lower frequencies. As curve D shows in particular, the resonant frequency can also be broadened, so that the absorption behavior is sustainably improved up to comparatively high frequencies of 500 Hz.

The absorption behavior shown in curve D was obtained with a material layer 2 which is made of sheet steel, has a thickness of 1.25 mm and a wall spacing of 100 mm. Holes with a diameter of 1 mm were introduced into the material layer 2, which are each spaced 22 mm apart. The percentage of perforated area is therefore 0.16%.

The absorption behavior shown in curve E was obtained with a material layer 2 made of sheet steel, a thickness of 1.25 mm and a distance from the wall of 100 mm having. Holes with a diameter of 1 mm were introduced into the material layer 2, which are each spaced 35 mm apart. The percentage of perforated area is therefore 0.064%.

Of course, the invention is not limited to the illustrated embodiments. The foregoing description is therefore not to be considered as limiting but as illustrative. This does not exclude the presence of other features. Insofar as the claims and the above description define "first" and "second" embodiments, this designation serves to distinguish between two similar embodiments without establishing a ranking.

Claims (13)

1. Sound absorber with at least one open-pored base plate (1), which has no bores and has a flow resistance of about 500 Ns/m³ to about 6000 Ns/m³ according to DIN EN 29053:1993-05, at least a partial surface of the base plate (1) that is visible when used as intended being provided with a microperforated material layer (2), and the microperforated material layer (2) having a plurality of bores (20), the diameter of which is in each case between about 0.1 mm and about 2 mm, characterized in that the microperforated material layer (2) is integrally bonded to the base plate (1) only in a strip-like or linear or punctiform manner.
2. Sound absorber according to claim 1, characterized in that the base plate (1) has a flow resistance of more than about 2000 Ns/m³ according to DIN EN 29053:1993-05 or
   in that the base plate (1) has a flow resistance of about 2000 Ns/m³ according to DIN EN 29053:1993-05.
3. Sound absorber according to claim 1 or 2, characterized in that the base plate (1) has an open porosity of from about 30% to about 99% or from about 40% to about 80% or from about 45% to about 60%.
4. Sound absorber according to any one of claims 1 to 3, characterized in that the base plate (1) has a thickness of from about 6 mm to about 100 mm, or from about 50 mm to about 200 mm, or from about 7 mm to about 80 mm, or from about 8 mm to about 40 mm, or from about 10 mm to about 30 mm.
5. Sound absorber according to any one of claims 1 to 4, characterized in that the microperforated material layer (2) is adhered and/or welded and/or soldered to the base plate (1).
6. Sound absorber according to any one of claims 1 to 5, characterized in that the microperforated material layer (2) has a thickness of from about 0.5 mm to about 1.8 mm or from about 0.8 mm to about 1.5 mm or from about 1 mm to about 4 mm or from about 1 mm to about 2 mm.
7. Sound absorber according to any one of claims 1 to 6, characterized in that the microperforated material layer (2) has a plurality of bores (20), the diameter of which is in each case between about 0.3 mm and about 1.2 mm, or between about 0.4 mm and about 0.8 mm, or between about 0.8 mm and about 2.0 mm.
8. Sound absorber according to any one of claims 1 to 7, characterized in that the area ratio of the bores (20) of the microperforated material layer (2) is between about 5% and about 10%, or between about 6% and about 8%, or

   between about 0.1% and about 10%, or

   between about 1% and about 9% or

   between about 5% and about 8% or

   between about 0.005% and about 2% or

   between about 0.01% and about 1%

   of the total area.
9. Sound absorber according to any one of claims 1 to 8, characterized in that the distance between adjacent bores of the microperforated material layer is chosen between about 15 mm and about 100 mm or between about 20 mm and about 60 mm.
10. Sound absorber according to any one of claims 1 to 9, characterized in that the microperforated material layer (2) contains or consists of a melamine resin and/or a thermoset and/or a thermoplastic and/or a wood veneer and/or polyethylene and/or polyethylene terephthalate and/or ethylene tetrafluoroethylene copolymer and/or a metal or an alloy and/or steel and/or aluminum.
11. Sound absorber according to any one of claims 1 to 10, characterized in that the base plate (1) contains or consists of a pressed polyester fleece and/or a wood-based material and/or pressed mineral wool and/or sintered glass foam and/or cement-bound expanded clay and/or a thermosetting foam and/or a melamine resin and/or a natural fiber material and/or a metal foam.
12. Sound absorber according to any one of claims 1 to 11, further containing at least one mechanical reinforcement element (15) containing or consisting of, for example, GFRP and/or CFRP and/or polyethylene and/or polyester and/or wood or a wood-based material.
13. Use of a sound absorber according to any one of claims 1 to 12 in or on a building.

Images