EP3771779B1 - Room sound absorber for mounting on a wall and / or ceiling - Google Patents

Description

The present invention relates to a room sound absorber for mounting on a wall and/or ceiling.

Such absorbers are used to reduce reverberation in rooms. Room sound absorbers in the form of so-called acoustic images are known, which are designed to absorb only the sound waves that hit from the front. This means that the reverberation insulation is not optimal.

From the WO 2018/037345 A1 A room sound absorber is known that has a large number of absorber bodies that lie on the wall after installation. This makes it difficult to adequately absorb the sound waves.

From the DE 20 2007 016 382 U1 describes a room sound absorber with foam parts as the only material for sound absorption. This design has the disadvantage that it is only effective over a narrow frequency range. The DE 20 2007 016 382 U1 discloses a room sound absorber according to the preamble of claim 1.

An object of the present invention is to provide a room sound absorber with improved reverberation insulation.

A room sound absorber which solves this problem is specified in claim 1. The further claims specify preferred embodiments.

By providing spacers and a sound-absorbing layer with a large number of protruding absorber bodies directed towards the wall or ceiling, sound waves can pass behind the room sound absorber and be effectively absorbed by the layer.

Fig. 1

die Rückseite eines ersten Ausführungsbeispiels eines Raumschallabsorbers in einer perspektivischen Ansicht;

Fig. 2

die Rückseite des Beispiels gemäss Fig. 1;

Fig. 3

die Vorderseite des Beispiels gemäss Fig. 1;

Fig. 4

das Beispiel gemäss Fig. 1 montiert an einer Wand in einer Seitenansicht geschnitten in der Ebene IV-IV gemäss Fig. 2;

Fig. 5

eine perspektivische Ansicht eines Beispiels eines Raumschallabsorbers, welches nicht Teil der Erfindung ist;

Fig. 6

die Vorderseite des Beispiels gemäss Fig. 5;

Fig. 7

die Rückseite des Beispiels gemäss Fig. 5;

Fig. 8

das Beispiel gemäss Fig. 5 montiert an einer Decke in einer Seitenansicht geschnitten in der Ebene VIII-VIII gemäss Fig. 7;

Fig. 9

die Rückseite einer Variante des ersten Ausführungsbeispiels in einer perspektivischen Ansicht;

Fig. 10

die Rückseite des Beispiels gemäss Fig. 9 zusätzlich mit einer Aufhängevorrichtung;

Fig. 11

das Beispiel gemäss Fig. 9 montiert an einer Wand in einer Seitenansicht geschnitten in der Ebene XI-XI gemäss Fig. 10;

Fig. 12

das Beispiel gemäss Fig. 9 montiert an einer Wand in einer Seitenansicht geschnitten in der Ebene XII-XII gemäss Fig. 10;

Fig. 13

die Vorderseite einer Erweiterung des Beispiels gemäss Fig. 9 in einer perspektivischen Ansicht;

Fig. 14

die Rückseite des Beispiels gemäss Fig. 13;

Fig. 15

das Beispiel gemäss Fig. 13 montiert an einer Wand in einer Seitenansicht geschnitten in der Ebene XV-XV gemäss Fig. 14; und

Fig. 16

das Beispiel gemäss Fig. 13 montiert an einer Wand in einer Seitenansicht geschnitten in der Ebene XVI-XVI gemäss Fig. 14.

Further specific design features and their advantages are evident from the following description and figures of embodiments. They show

Fig.1

the rear side of a first embodiment of a room sound absorber in a perspective view;

Fig.2

the back of the example according to Fig.1 ;

Fig. 3

the front of the example according to Fig.1 ;

Fig.4

the example according to Fig.1 mounted on a wall in a side view cut in plane IV-IV according to Fig.2 ;

Fig.5

a perspective view of an example of a room sound absorber which is not part of the invention;

Fig.6

the front of the example according to Fig.5 ;

Fig.7

the back of the example according to Fig.5 ;

Fig.8

the example according to Fig.5 mounted on a ceiling in a side view cut in plane VIII-VIII according to Fig.7 ;

Fig.9

the back of a variant of the first embodiment in a perspective view;

Fig.10

the back of the example according to Fig.9 additionally with a hanging device;

Fig. 11

the example according to Fig.9 mounted on a wall in a side view cut in plane XI-XI according to Fig.10 ;

Fig. 12

the example according to Fig.9 mounted on a wall in a side view cut in plane XII-XII according to Fig.10 ;

Fig. 13

the front of an extension of the example according to Fig.9 in a perspective view;

Fig. 14

the back of the example according to Fig. 13 ;

Fig. 15

the example according to Fig. 13 mounted on a wall in a side view cut in plane XV-XV according to Fig. 14 ; and

Fig. 16

the example according to Fig. 13 mounted on a wall in a side view cut in plane XVI-XVI according to Fig. 14 .

Fig. 1-4 show a first embodiment of a room sound absorber. This comprises an outer frame 10, on which a sound-absorbing layer 20 is arranged by means of an inner frame 11.

The outer frame 10 has a side wall 10a and a front wall 10b arranged transversely thereto (cf. Fig. 3 ) and is composed of L-shaped profile parts, for example made of wood.

The inner frame 11 is made of strips, e.g. made of wood. A fabric ("fabric cover") 30 is attached to the inner frame 11, which is open-pored and printed so that it shows, e.g., a picture on the front (cf. Fig. 3 ). The fabric 30 is stretched on the inner frame 11 by being placed over the outer edge of the inner frame 11 and being fastened to the back thereof, for example by means of a plurality of clips.

The inner frame 11 is inserted into the outer frame 10 and secured by means of flexible elements 15 arranged between them. These are formed, for example, by means of silicone-based adhesive, which is applied, for example, between the corners of the inner frame 11 and the outer frame 10. Due to the flexibility of the elements 15, changes in the length of the outer frame 10 and/or inner frame 11 can be compensated. This means that the material 30 does not warp or wrinkle. Preferably, the two frames 10 and 11 are connected exclusively with the flexible elements 15.

The sound-absorbing layer 20 is attached to the inner frame 11, e.g. by means of clamps, and has a plurality of absorber bodies 21 which protrude, see also Fig.4 The side of the layer 20 facing away from the absorber bodies 21, ie the side facing the material 30, is flat.

The absorber bodies 21 are arranged on a grid and are tapered towards the top. The grid is selected such that the respective center of the absorber bodies 21 lies on the grid points of a square network.

The absorber bodies 21 are typically dimensioned such that there are at least ten, preferably at least twenty absorber bodies 21 and/or at most fifty, preferably at most forty absorber bodies 21 per dm ² . The height measured from the lowest point to the tip of an absorber body 21 is typically at least 0.5 cm, preferably at least 1 cm and/or at most 4 cm, preferably at most 3 cm.

The layer 20 is made of foam, e.g. polyurethane (PUR), for example in the form of a PUR convoluted foam. A respective absorber body 21 has pores that are arranged irregularly to one another and thus promote effective absorption of sound waves.

The layer 20 typically has a density (density of the layer based on the volume including the pore spaces) of at least 10 kg/m ³ , preferably at least 20 kg/m ³ and/or at most 100 kg/m ³ , preferably at most 50 kg/m ³ . For example, the density is in the range of 20-30 kg/m ³ .

Since layer 20 is located on the back of the room sound absorber, it does not necessarily have to be colorfast. Layer 20 is preferably made of a flame-retardant material.

To ensure that layer 20 fits well to fabric 30, in the example according to Fig.1 a longitudinal part 22, e.g. an elastic band, is provided, which runs alternately along the layer 20 and the inner frame 11 and is fastened at each end to the inner frame 11. The sections of the longitudinal part 22 which run along the inner frame 11 are fastened there to the inner frame 11, e.g. by means of clamps.

In the present example, the room sound absorber has another sound-absorbing material 40, which is arranged in a cross shape on the back of the room sound absorber. The material 40 is arranged in the form of blocks on a support 44, which is formed by a cross made of strips, e.g. made of wood. The ends of the support 44 are attached to the outer frame 10 by means of flexible elements 45. These are formed, for example, by means of silicone-based adhesive. The support 44 with the material 40 is movably connected to the outer frame 20 due to the flexible elements 45. This makes it possible to compensate for changes in the length of the outer frame 10 and/or the support 44.

The sound-absorbing material 40 is preferably made of foam, eg a composite foam such as PUR composite foam, and has a higher density than the layer 20 in order to effectively absorb sound waves with lower frequencies. Typically, the density is at least 150 kg/m ³ , preferably at least 200 kg/m ³ and/or at most 300 kg/m ³ , preferably at most 400 kg/m ³ . For example, the density is 250 kg/m ³ .

The room sound absorber also has spacers 50 and a suspension device 60. The suspension device 60 is formed, for example, by a chain, a rope or a band and is attached at both ends to the inner frame 11. The suspension device 60 allows the room sound absorber to be hung on the wall, for example, using one or more nails. The suspension device 60 can also be designed differently. If the room sound absorber is used, for example, for mounting on a ceiling, For example, one or more tensioned, elastic ropes can be provided which are hooked into two or more hooks.

The spacers 50 are pin-shaped and can be provided with soft support elements, e.g. made of felt, at the end. The spacers 50 are attached to the inner frame 11 and protrude at a distance A over the outer frame 10, see. Fig.4 Typically, the distance A is at least 1 cm, preferably at least 2 cm, particularly preferably at least 3 cm. The greater the distance A between the wall and the room sound absorber, the greater the sound absorption.

In the present example, the spacers 50 are arranged in the corners of the inner frame 11. They can also be attached at other locations. The number of spacers 50 can be two, three, four or more.

The spacers 50 are dimensioned so that after the installation of the room sound absorber there is an air gap between the absorber bodies 21 of the layer 20 and the wall. How Fig.4 shows, there is also an air gap between the material 40 and the wall.

The functionality and advantages of the embodiment described so far can be summarized as follows:
The room sound absorber acts as an effective reverberation insulation and ensures that the sound in the room is not reflected as strongly or hardly at all.

The room sound absorber is designed in such a way that the sound waves in the high frequency range are absorbed at the front (material 30) and the middle frequencies are converted into heat in the layer 20 behind the material 30. The slightly lower and low frequencies, which mainly travel along the wall ("waving"), are absorbed on the back of the material 30. The air gap between the room sound absorber and the wall provided by the spacers 50 allows the sound waves to pass behind the room sound absorber and be converted into heat by the layer 20 and the material 40.

The room sound absorber can be used in rooms where the understanding of speech, the enjoyment of music and/or the room sound are impaired by reverberation. Particularly in acoustic measuring rooms and measuring booths The room sound absorber is suitable because it is precisely in these rooms that the measurement results can be improved many times over by absorbing the reverberation.

The room sound absorber can be individually designed. The size can be adapted to the room and the material can be printed with selected and suitable images. The printing is preferably carried out in such a way that the material is not provided with a closed print layer, but remains open-pored so that the majority of the sound can pass through.

The embodiments described so far are designed for mounting on a wall. Fig. 5-8 show an example, which is not part of the invention, for mounting on a ceiling. In this example, a sound-absorbing layer 70 with protruding absorber bodies 71 is attached to the front. The layer 70 is surrounded by an outer frame 10', which is composed of L-shaped profile parts, for example made of wood.

The side of the layer 70 facing away from the absorber bodies 71, ie the side facing the layer 20 (cf. Fig.8 ), is just trained.

The absorber bodies 71 are arranged on a grid and are tapered towards the top, e.g. pyramid-shaped. The grid is selected, for example, such that the respective center of the absorber bodies 71 lies on the grid points of a square network.

The absorber bodies 71 are typically dimensioned such that there are at least two, preferably at least three absorber bodies 71 and/or at most twenty, preferably at most ten absorber bodies 71 per dm ² . The height of a respective absorber body 71 measured from the lowest point to the tip is typically at least 2 cm, preferably at least 3 cm, particularly preferably at least 4 cm.

A suitable material for layer 70 is foam, for example made of melamine resin. The material of layer 70 typically has a density which is at least 5 kg/m ³ and/or at most 50 kg/m ³ . The material is preferably colorfast, since the absorber bodies 71 remain visible after assembly. Thus, solar radiation does not lead to a color change, e.g. yellowing, fading, etc. The material of the layer 70 is preferably flame-retardant and has, for example, a fire index of 5.3.

How Fig.7 shows, the outer frame 10' surrounds an inner frame 11', which is formed from strips, for example made of wood. Furthermore, the sound-absorbing layer 20 and the spacers 50 can be seen, as in the embodiment according to Fig.1 are provided. Preferably, the absorber bodies 71 of the layer 70 are larger than the absorber bodies 21 of the layer 20, so that the number of absorber bodies 71 per unit area is smaller than the number of absorber bodies 21.

In the present example, the layer 20 is attached to the back of the layer 70, e.g. by gluing. The layer 20 is therefore held to the outer frame 10' via the layer 70.

A suspension device 60' is provided for fastening to the ceiling, which here is formed by two elastic ropes or straps, which are fastened at the end to the inner frame 11'. For assembly, hooks are attached to the ceiling, onto which the ropes or straps of the suspension device 60' are hooked. The suspension device allows the mounted room sound absorber to be rotated and thus aligned, especially if the hooks were not attached exactly in line.

The spacers 50 are attached to the inner frame 11' and protrude as in the example according to Fig.4 with a distance A beyond the outer frame 10', cf. Fig.8 .

For room sound absorbers according to Fig.5 By providing the layer 70 on the front side, the sound can be absorbed even more effectively and converted into heat.

In an alternative variant, the layer 70 can be replaced by the material 30 according to the example in Fig. 3 be replaced and e.g. be mounted on the inner frame 11'.

Fig. 9-12 shows a variant of the first embodiment according to Fig.1 .

For the sake of simplicity, only a single frame 10" is shown here, in which the sound-absorbing layer 20 is arranged and on which the material 30 is stretched. Instead of the single frame 10", it is conceivable to provide an outer frame 10 and an inner frame 11, as in the first embodiment, which are connected to one another by means of flexible elements 15 arranged between them.

In contrast to the first embodiment, the additional sound-absorbing material 40a, 40b is arranged differently.

A support frame 47 is provided within which one or more support struts 47a are arranged, which connect opposite sides of the support frame 47 to one another. The support frame 47 and the support struts 47a serve as supports for the additional sound-absorbing material 40a, 40b. The sound-absorbing layer 20 is also held by the support struts 47a and thus take over the function of the longitudinal part 22 from the first embodiment.

The support frame 47 is connected to the individual frame 10" - or an outer frame 10 if present - via intermediate elements 48. The intermediate elements 48 can consist of a flexible material, e.g. a silicone-based adhesive.

The additional sound-absorbing material 40a, 40b is attached in the form of lamellas to the support frame 47 and the support struts 47a, in that it is designed in the form of blocks 40a, 40b, which each extend from one side of the support frame 47 over the support struts 47a to the opposite side of the support frame 47. The individual blocks 40a, 40b are each arranged at a distance from one another, so that a free space is provided, which allows access to the layer 20.

In particular Fig. 12 shows, the blocks 40b, 40b have a cross-section in the form of an oblique parallelogram, except for the block 40b in the middle, which has a trapezoidal cross-section. The respective block 40a, 40b can also have a different shape, eg that of a rectangular cuboid. Blocks 40a, 40b with bevelled sides have the advantage over rectangular cuboids that a larger surface is available with the same amount of material.

In the present example, blocks 40a, 40b with different densities are provided. For example, a block 40a has a greater density than block 40b. The blocks 40a, 40b are arranged alternately, for example.

After mounting on the wall using, for example, the hanging device 60, the spacers 50 create an air gap between the wall and the other sound-absorbing material 40a, 40b and thus also between the wall and the layer 20, cf. in Fig. 12 the distance A by which the spacers 50 protrude beyond the support frame 47, and the distance B between the wall and the further sound-absorbing material 40a, 40b. Typically, the distance B is at least 1 cm, preferably at least 2 cm, particularly preferably at least 3 cm. The distance A is typically at least 1 cm, preferably at least 2 cm, particularly preferably at least 3 cm, greater than the distance B.

Fig. 13-16 show an extension of the embodiment according to Fig. 9-12 , in which a base plate 80 is additionally provided, which is made of sound-absorbing material. This can, for example, have a density that is even higher than that of the material 40a, 40b. The base plate 80 therefore supports the absorption, especially in the low frequency range.

How special Fig. 15 and 16 show, the base plate 80 can have inwardly bevelled edges to support sound deflection, see also in Fig. 14 the dashed rectangle within the base plate 80, which indicates the inner end of the edges.

60" strips are attached to the rear of the base plate 80 and protrude laterally beyond the base plate 80. A screw can be passed through the respective protruding part of a 60" strip, for example, to mount the room sound absorber on the wall or ceiling.

The strips 60" are connected to the support frame 47 via spacers 50'. The spacers 50' are each designed to be split, whereby the end parts of a spacer 50' can be connected to one another, for example by means of a screw connection.

During assembly, the 60" strips are screwed to the wall or ceiling, which also mounts the base plate 80. The parts of the 50' spacer are then screwed together, which connects the rest of the room sound absorber to the 60" strips.

In the variant shown here, the spacers 50' and strips 60" also serve as a suspension device, so that the suspension device 60, which is provided in the other embodiments, can be omitted.

After installation, the spacers 50' create an air gap between the base plate 80 and the other sound-absorbing material 40a, 40b and thus also between the wall or ceiling and the layer 20, cf. in Fig. 16 the distance A' of the spacers 50' between the base plate 80 and the support frame 47 and the distance B' between the base plate 80 and the further sound-absorbing material 40a, 40b.

The room sound absorbers described here are particularly effective for reducing reverberation in a room and ensure that the sound is not reflected as strongly or hardly at all. The room sound absorbers are designed in such a way that the sound in the hearing range in particular is absorbed, including in the range from 50 Hz to 8,000 Hz and/or in the range from 150 Hz to 8,000 Hz.

Depending on the measurement of the room acoustics, the room sound absorbers can be designed specifically to effectively dampen the reverberation. Depending on the frequency range to be influenced, sound-absorbing materials are used, e.g. only layer 20 or a combination with one or more of the materials 40, 40a, 40b, 70, 80.

After assembly, the absorber bodies 21 are arranged at a distance from the wall or ceiling by the spacers 50; 50', forming an air gap. This creates an air layer between the absorber bodies 21 and the wall or ceiling. The thickness of the air layer is typically at least 1 cm, preferably at least 2 cm, particularly preferably at least 3 cm. The air layer does not necessarily border the sound-absorbing layer 20 over its entire surface, but can be interrupted by components, e.g. by the carrier 44 and the sound-absorbing material 40 in the example according to Fig.1 or by the carrier 47, 47a and the sound-absorbing material 40a, 40b in the example according to Fig.9 or 13. Furthermore, the air layer can be arranged at a distance from the wall or ceiling; for example, in the example according to Fig. 16 the air layer on the wall or ceiling side is limited by the base plate 80.

The air layer which is at least partially adjacent to the absorber body 21 provides access for the sound waves so that they can reach behind the room sound absorber and be converted into heat by the layer 20.

Numerous modifications will become apparent to those skilled in the art from the above description without departing from the scope of protection defined in the patent claims.

In the examples shown here, the room sound absorbers have a rectangular shape. This can also be different, e.g. polygonal, round, for example circular or elliptical, or a combination of straight and round shapes.

After installation, the room sound absorber may protrude relatively far into the room, making it possible to see behind the room sound absorber from the side. To prevent this, the side of the room sound absorber can be covered all the way around, e.g. using a stretchable material.

Claims (12)

1. Room sound absorber for mounting at a wall and/or ceiling, with a frame (10; 10") in which a sound-absorbing layer (20) is arranged, which has a plurality of protruding absorber bodies (21) which, after mounting, are directed towards the wall or ceiling, and with spacers (50; 50') which serve, after mounting, the frame (10; 10") and the absorber bodies (21) being arranged at a distance from the wall or ceiling forming an air gap, characterized in that the room sound absorber includes at least one further sound-absorbing material (40; 40a, 40b, 80), which has a greater bulk density than the sound-absorbing layer (20) and which is held on the frame (10; 10") in such a way that it is arranged between the sound-absorbing layer (20) and the wall or ceiling after mounting.
2. Room sound absorber according to claim 1, wherein the spacers (50; 50') have at least one of the following features A1-A5:

   A1) the spacers are designed in a pin-shaped manner;

   A2) the spacers protrude at least 1 cm, preferably at least 2 cm, particularly preferably at least 3 cm beyond the frame (10; 10");

   A3) at least three spacers are provided;

   A4) the end of a respective spacer has a distance from the frame (10; 10") which is at least 1 cm, preferably at least 2 cm, particularly preferably at least 3 cm;

   A5) the respective spacer is designed in a divided manner so that two connection ends are formed, which can be connected to each other by a detachable connection, in particular a screw connection.
3. Room sound absorber according to any one of the preceding claims, wherein the sound-absorbing layer (20) has at least one of the following features B1-B9:

   B1) the layer is made of a foam material;

   B2) the bulk density of the layer is at least 10 kg/m³, preferably at least 20 kg/m³;

   B3) the absorber bodies (21) are arranged on a grid;

   B4) the absorber bodies are designed to taper towards the top;

   B5) the height of the absorber bodies is at least 0.5 cm, preferably at least 1 cm,

   B6) the height of the absorber bodies is at most 4 cm, preferably at most 3 cm;

   B7) at least 10, preferably at least 20 absorber bodies are provided per square decimeter;

   B8) at least one longitudinal part (22, 47a), which is preferably elastic, is placed over the layer to fix it;

   B9) the side of the layer (20) facing away from the absorber bodies (21) is designed in a flat manner.
4. Room sound absorber according to any one of the preceding claims, wherein the frame is an outer frame (10) which surrounds an inner frame (11).
5. Room sound absorber according to claim 4, which includes yielding elements (15) via which the inner frame (11) is held at the outer frame (10), preferably the inner frame is held at the outer frame exclusively via yielding elements and/or preferably the yielding elements are formed by a silicone glue.
6. Room sound absorber according to any one of the preceding claims, wherein a surface of fabric (30) is provided, which is held directly or indirectly at the frame (10), preferably the fabric is printed and/or the fabric is stretched at the or an inner frame (11), particularly preferably the printed fabric is open-pored.
7. Room sound absorber according to any one of the preceding claims, wherein the at least one further sound-absorbing material (40; 40a, 40b, 80) has at least one of the following features C1-C5:

   C1) the bulk density of the material is at least 150 kg/m³, preferably at least 200 kg/m³;

   C2) the material is designed in the form of one or more blocks, wherein a block is preferably cuboid or has a cross-section of an oblique-angled parallelogram;

   C3) the material is arranged on a carrier (44; 47, 47a), which is attached to the frame (10; 10") via yielding elements (45; 48);

   C4) the material is arranged on a cross-shaped carrier (44) and/or on a carrier which comprises a carrier frame (47);

   C5) the material is designed in the form of several blocks, which are arranged at a distance from each other so that there is a free interspace between them, preferably the blocks are arranged parallel to each other.
8. Room sound absorber according to any one of the preceding claims, which includes a suspension device (60; 60") for mounting at the wall and/or ceiling, preferably the suspension device has one or more of the following elements: chain, rope, strap, strip.
9. Room sound absorber according to any one of the preceding claims, which includes a further sound-absorbing layer which is arranged at the front side of the room sound absorber, and which has protruding absorber bodies.
10. Room sound absorber according to claim 9, wherein the further sound-absorbing layer has at least one of the following features D1-D7:

    D1) the layer is made of a foam material;

    D2) the bulk density of the layer is at least 5 kg/m³;

    D3) the absorber bodies are arranged on a grid;

    D4) the absorber bodies are designed to taper towards the top;

    D5) the absorber bodies have a greater height than the absorber bodies (21) of the first sound-absorbing layer (20);

    D6) fewer absorber bodies per square decimeter are provided than for the first sound-absorbing layer;

    D7) the layer is colorfast.
11. Room sound absorber according to any one of the preceding claims, which includes a first further sound-absorbing material (40a, 40b) which is the at least one further sound-absorbing material and which is arranged on a carrier (47, 47a) which is held at the frame (10"), and a second further sound-absorbing material (80) which can be mounted at the wall or ceiling, so that an air gap is provided between the two materials.
12. Room sound absorber according to claim 11 which has at least one of the following features E1-E7:

    E1) the first further sound-absorbing material is designed in several blocks (40a, 40b), wherein preferably at least one block has a greater bulk density than at least one other block;

    E2) the first further sound-absorbing material has a lower bulk density than the second further sound-absorbing material (80);

    E3) the first further sound-absorbing material (40a, 40b) has a bulk density of at least 150 kg/m³ and/or less than 300 kg/m³;

    E4) the second further sound-absorbing material (80) has a bulk density of at least 300 kg/m³ and/or at most 500 kg/m³;

    E5) the second further sound-absorbing material is designed as a panel, which preferably has beveled edges;

    E6) the second further sound-absorbing material is held at the spacers (50');

    E7) the second further sound-absorbing material is arranged at strips (60") which can be attached to the wall or ceiling.

Images