Metamaterial sound insulation device

Abstract

To provide a metamaterial sound insulation device.SOLUTION: A first layer of a first material having a predetermined static Young's modulus and a density within a predetermined range, a second layer of a second material having a first surface attached to a surface of the first layer and a second surface facing away from the first surface, and made of a material having a predetermined static Young's modulus, a predetermined density and a predetermined weight per unit area attached to or integral with at least one of the first surface or the second surface of the second layer. A protrusion or a plurality of discrete protrusions in the form of a mesh, wherein the contact area of each of the discrete protrusions is not greater than a predetermined value and the total contact area of the protrusion or the plurality of discrete protrusions is within a predetermined range, wherein the second material has the same static Young's modulus as the protrusions and the same weight per unit area as the protrusions.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a sound insulating device, i.e. a device having the effect of attenuating sound transmission across the device, which is particularly adapted for sound insulation in the automotive field. [Background technology]

[0002] Sound insulation is needed to ensure and / or improve people's comfort in several stationary or mobile applications: for example, it may be desirable to isolate adjacent flats in a building, adjacent rooms in an office, or sections of a manufacturing plant, and it is usually necessary to isolate the driver's or passenger's cab of cars and trucks and vehicles from different noise sources such as engine bays, tire noise, or aerodynamic (air-borne) noise.

[0003] Since the requirements for sound insulation in the automotive field are more stringent and demanding than in other areas, the following description will be directed specifically to the former, but the invention has general applicability in any situation requiring insulation from noise.

[0004] Achieving good sound insulation in the automotive field is difficult due to the limited space and mass available for acoustic isolation components.

[0005] Isolation components for automotive applications are generally manufactured by combining layers of different materials, such as fiber aggregates (which may be natural-like cotton, polymeric fibers, or inorganic-like glass fibers), foams, dense polymer layers, and polymeric membranes (sometimes multiple layers of each), according to a wide variety of structures, one or more of which may contain fillers such as mineral powders to modify the properties of the substrate.

[0006] These components may include at least one of the layers having elastic properties, i.e., capable of recovering its original shape and size after compression or expansion, and at least a rigid, essentially incompressible layer. These components operate according to the spring-mass principle, in which the elastic layer (often also called the "decoupling layer," and typically a foam, when present) acts as the spring and the rigid layer acts as the mass (which is therefore referred to in the art as the "mass layer").

[0007] One problem with these components is that when their sound-insulating properties need to be improved, the only possible solution is to increase the thickness and weight of the mass layer in a uniform manner, resulting in an associated weight increase of the component. This approach is followed, for example, in U.S. Patent Application Publication No. 2004 / 0150128(A1), in which the stiff layer is created by first thermoforming a foil or flat plate of thermoplastic material and then adding an additional amount of the same thermoplastic material onto selected areas of the formed foil or plate (preferably in a cavity) to form areas of increased thickness in the stiff layer. This document does not teach the geometric characteristics of these additions of thermoplastic material, i.e., their thickness (absolute or relative to the initial foil or plate), their area compared to the area of ​​the stiff layer, or their distribution over the stiff layer. Furthermore, this document does not provide data on the acoustic properties of the finished sound-insulating component obtained using the described process.

[0008] The automotive industry is struggling to reduce the weight of vehicles as much as possible to minimize their power consumption and therefore their environmental impact. The trend towards weight reduction is even more felt in electric vehicles, where lower weight offers the opportunity to increase autonomy, thanks to lower mass being moved with the same battery pack, or because the weight gain can be exploited in fitting larger sized batteries.

[0009] In order to reduce the overall weight of noise-damping components, several documents propose creating voids in at least one of their layers in the form of through-holes, recesses, indentations, etc. Components following this approach are described, for example, in U.S. Pat. No. 5,013,597, U.S. Pat. No. 7,182,172 (B2), and WO 2018 / 091301 A1.

[0010] US Patent Application Publication No. 2012 / 0155688(A1) discloses a wide variety of acoustic absorbers and transducers in different configurations. One of these, described with reference to Figure 5 of the document, adds a discontinuous stiff layer directly onto a spring layer. The stiff layer can be patterned as a grid (Figure 5A of the document) or as a series of parallel abutting diamonds (Figure 5B).

[0011] A problem with known noise attenuation components is that while they generally have good blocking performance in the high frequency range, they do not have as good blocking properties within the range of about 200 Hz to 1000 Hz, which is crucial for noise sources related to automotive applications.

[0012] Currently, components that achieve a good compromise between weight reduction and good isolation across the entire spectrum of frequencies in the mass-spring-mass mechanism that are important for acoustic comfort are not yet available for resonant frequency bands. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] U.S. Patent Application Publication No. 2004 / 0150128(A1) [Patent Document 2] U.S. Patent No. 5,013,597 [Patent Document 3] U.S. Patent No. 7,182,172(B2) [Patent Document 4] WO2018 / 091301A1 [Patent Document 5] U.S. Patent Application Publication No. 2012 / 0155688(A1) Summary of the Invention [Problem to be solved by the invention]

[0014] It is an object of the present invention to provide a sound insulation device that overcomes the problems of the prior art and is particularly useful for use in the automotive field. [Means for solving the problem]

[0015] The purpose of this is to a first layer of a first material, not necessarily of uniform thickness, having a static Young's modulus of 1 kPa to 1 MPa; a first surface attached to a surface of the first layer and a second surface facing away from the first surface, the second surface having a static Young's modulus of 10 MPa to 2500 MPa and a coefficient of elasticity of 0.5 kg / m 2 and 20 kg / m 2 a second layer of a second material having a weight per unit area between a static Young's modulus of 10 MPa to 2500 MPa and a coefficient of elasticity of 0.5 kg / m 2 and 20 kg / m 2 and a weight per unit area between 0.01 and 0.15, wherein the contact area of ​​each of the individual protrusions is no more than 2% of the area of ​​the first surface or the second surface of the second layer, and the total contact area of ​​the one protrusion or the multiple protrusions is 10% to 60% of the area of ​​the first surface or the second surface of the second layer. This is achieved by the present invention, which relates to a metamaterial sound insulation device comprising:

[0016] The invention will now be described with reference to the drawings. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 shows a cross-sectional view (upper part of the figure) and a top view (lower part of the figure) of a first possible embodiment of a sound insulating device of the present invention, comprising a plurality of individual protrusions arranged in a two-dimensional periodic array on the second surface of the second layer. [Figure 2] 2A-2C show, in top and cross-sectional views, possible alternative shapes for individual protrusions that may be present in the device of FIG. 1. [Figure 3] FIG. 10 shows a side view (upper part of the figure) and a top view (lower part of the figure) of another possible sound insulating device of the present invention, comprising a plurality of individual protrusions randomly arranged on the second surface of the second layer. [Figure 4] 1 and 2 show cross-sectional and top views similar to those of FIG. 1 of another possible sound insulation device of the present invention, comprising a plurality of individual protrusions arranged in a two-dimensional periodic array on a first surface of a second layer, the protrusions having different shapes. [Figure 5] 1 and 2 show cross-sectional and top views similar to those of FIG. 1 of another possible sound insulation device of the present invention, comprising a plurality of individual protrusions arranged in a two-dimensional periodic array on the second surface of the second layer. [Figure 6] 1 and 2. A cross-sectional view and a top view similar to those of FIG. 1 showing another possible sound insulating device of the present invention, which comprises a plurality of individual protrusions arranged in a two-dimensional periodic array on the second surface of the second layer, and the first layer has recesses or through holes with the same arrangement as the protrusions. [Figure 7] 1 and 2. A cross-sectional view and a top view similar to those of FIG. 1 showing another possible sound insulating device of the present invention, which comprises a plurality of individual protrusions arranged in a two-dimensional periodic array on the second surface of the second layer, and the first layer has recesses or through holes with the same arrangement as the protrusions. [Figure 8] 1 and 2. A cross-sectional view and a top view similar to those of FIG. 1 showing another possible sound insulating device of the present invention, which comprises a plurality of individual protrusions arranged in a two-dimensional periodic array on the second surface of the second layer, and the first layer has recesses or through holes with the same arrangement as the protrusions. [Figure 9]2 shows a cross-sectional view similar to that of FIG. 1 and a top view of one possible sound insulating device of the invention, with one protrusion in the form of a regular mesh. [Figure 10] 2 shows a cross-sectional view similar to that of FIG. 1 and a top view of one possible sound insulating device of the invention, with one protrusion in the form of an irregular mesh. [Figure 11] 2A and 2B show cross-sectional and top views similar to those of FIG. 1 of a possible sound insulation device of the present invention, comprising a plurality of individual protrusions arranged in a two-dimensional periodic array on the second surface of the second layer, and wherein the first and second layers are non-flat and have non-constant thicknesses. [Figure 12] 1A and 1B show the geometries of particular devices of the present invention that were tested in the examples. [Figure 13] FIG. 1 is a graph comparing the sound isolation properties of a device of the present invention with those of a prior art device. DETAILED DESCRIPTION OF THE INVENTION

[0018] The sound-insulating device of the present invention is a modification of prior art spring-mass systems. The inventors have observed that it is possible to improve the sound-insulating properties of older systems by adding localized individual protruding elements, or single protruding elements in the form of a mesh, to the mass layer. This can be done without increasing the total mass of the sound-attenuation system.

[0019] A material that has altered properties compared to its inherent properties due to shaping is referred to in materials science and engineering as a "metamaterial," and this definition is adopted herein to refer to the assembly formed by the second layer and protrusions described above.

[0020] In the following description, the first layer and the second layer are referred to as the "separation layer" and the "mass layer," respectively.

[0021] "Protrusion integral with" the surface of the mass layer means that said protrusion and the layer are formed as a single piece, obtained for example by moulding or injection moulding.

[0022] The metamaterial sound insulation device of the present invention is characterized in that the mass layer has, on at least one of its surfaces, a continuous protrusion in the form of a mesh or a plurality of individual protrusions.

[0023] In the case of a single protrusion in the form of a mesh, this may have a regular configuration, for example defining a square, rectangular, triangular or hexagonal pattern, or the configuration may be irregular, with the intersections (or nodes) of the mesh lines being randomly distributed on the mass layer surface.

[0024] Similarly, the plurality of individual protrusions may be disposed on the mass layer surface according to a regular, periodic pattern (thus defining an array) or randomly.

[0025] Each individual protrusion may have a contact area on the surface of the mass layer of up to 2% of said surface, and the total contact area on the surface of the mass layer of a single protrusion, or of multiple individual protrusions in the form of a mesh, is between 10% and 60% of said surface.

[0026] The separation layer has a static Young's modulus in the range of 1 kPa to 1 MPa and a stiffness of 1 kg / m 3 to 500 kg / m 3 up to, preferably 50 kg / m 3 and 100 kg / m 3 and a material having a density in the range between 0.01 and 0.05. This material can be, for example, a loose felt. Preferably, this material is a foam, especially a polyurethane (PU) foam, produced in a mold of suitable shape by the reaction of diisocyanate or polyisocyanate monomers with diol or polyol monomers in the presence of a catalyst or by activation with ultraviolet light.

[0027] The mass layer has a static Young's modulus between 50 MPa and 2500 MPa, preferably in the range of 50 MPa to 300 MPa, and a stiffness of 0.5 kg / m 2 and 20 kg / m 2 Between 1000 and 2000, preferably 2 kg / m 2 to 7 kg / m 2 The layer is made of a material having a weight per unit area of ​​up to 1000 psi. The material for the manufacture of this layer can be chosen from felt (of natural or synthetic fibers) or, preferably, from dense polymers. Preferred polymers for the manufacture of this layer are dense PU (i.e., not in the form of a foam), PVC, polyester (PET), polyolefins, in particular polyethylene (PE) and polypropylene (PP), and polyamide (PA, also generically called nylon).

[0028] The protrusions have a static Young's modulus ranging from 10 MPa to 2500 MPa and a stiffness of 500 kg / m 3 to 8000 kg / m 3 The material for the manufacture of the protrusions is advantageously selected from among the same materials useful for the manufacture of the mass layer.

[0029] The mass layer and the protrusions can be manufactured separately and then attached, for example by gluing. In a preferred embodiment of the invention, however, the mass layer and the protrusions are manufactured as a single part by injection molding and are therefore made of the same material.

[0030] Various possible embodiments of the metamaterial sound insulation device of the present invention are depicted in Figures 1-12. While the protrusions are presented in the figures as separate elements in contact with the mass layer, it should be understood that these figures also represent devices of corresponding structure in which the protrusions and mass layer are fabricated as a single piece. Furthermore, elements and features designated by the same numerals in the figures are the same in all embodiments.

[0031] FIG. 1 shows a device 10 of the present invention in a top view (lower part of the figure) and a cross-sectional view (upper part of the figure) along line A-A' of the top view. Device 10 is fabricated from a separation layer 11, a mass layer 12, and protrusions, collectively designated 14a, on a second surface 13 of mass layer 12. In this embodiment, the mass layer and spring layer are flat and have a constant thickness. Protrusions 14a are separate, individual elements that are arranged on surface 13 according to a regular, periodic pattern, in this case a rectangular grid. The base cells of the two-dimensional (2D) regular pattern, however, can also be square, rhombic, hexagonal, or triangular.

[0032] Figure 2 shows different possible shapes of protrusions 14b-14f that can be used in place of protrusion 14a in the device of Figure 1. In the figure, the top row shows top views of the protrusions, and the bottom row shows cross-sections of the corresponding elements along the dashed lines shown in the top views. In very brief, protrusion 14b is a solid cylinder, protrusion 14c is a hollow cylinder with a cavity extending through the entire thickness of the protrusion, protrusion 14d is a cylinder with a recess, protrusion 14e is a solid body of constant thickness but irregular shape, and protrusion 14f is a solid body of constant thickness but regular but complex shape.

[0033] 3 shows another possible device 30 of the present invention in top view (lower part of the figure) and side view (upper part of the figure). Device 30 has the same structure as device 10, except that protrusions 31 are randomly arranged on surface 13. Although protrusions 31 are depicted in the figure as having a circular cross section in the top view, they may obviously have any shape, for example one of the shapes shown in FIG. 2.

[0034] The protrusions on the mass layer of the devices of the invention need not all be equal. Figure 4 shows an example of this type of device of the invention in cross section and top view similar to that of Figure 1. This Example 40 device has the same general shape as device 10, but the protrusions, collectively designated 41, have different shapes and heights.

[0035] 5 shows another possible embodiment 50 of the device of the invention in a top view (lower part of the figure) and a cross-section along line A-A' of the top view (upper part of the figure). The device 50 is fabricated from a separation layer 51 having a recess in its surface that is in contact with the mass layer 12. A protrusion 52 is attached to or is integral with the first surface 53 of the mass layer and fits exactly into the recess in the separation layer. The dashed rectangle in the top view represents the projection of the protrusion 52 onto the second (upper) surface of the mass layer 12.

[0036] Figures 6, 7 and 8 show schematically other possible embodiments of the device of the invention, in which the separation layer has openings. In these three figures, the dashed rectangles in the top view represent the projection of the openings in the separation layer onto the mass layer.

[0037] Device 60 (FIG. 6) is similar in mass layer and protrusion configuration to device 10. Separation layer 61 instead has openings 62 through its entire thickness.

[0038] Device 70 (FIG. 7) is similar to device 10 except that separation layer 71 has a recess 72 in the surface that contacts the mass layer.

[0039] Device 80 (FIG. 8) is similar to device 70, except that in this case separation layer 81 has a cavity 82 in the surface opposite the surface in contact with the mass layer.

[0040] As in the other examples presented above, while in Figures 6-8 the protrusions on the mass layer (generally designated as element 14) are represented as solid cylinders and the openings in the separation layer (62, 72, or 82) have rectangular cross-sections, it will be apparent that both elements may have any shape, e.g., the protrusions may have any of the shapes represented in Figure 2, and the openings in the separation layer may have any shape in top view, e.g., square, hexagonal, circular, elliptical, etc. Furthermore, while devices 50, 60, 70, and 80 are represented in Figures 5-8 with a regular, periodic arrangement of protrusions in / on the mass layer and openings in the separation layer, in these examples too the arrangement of these elements in top view may be random, as in device 30. Finally, although in the top view drawings (lower parts of Figures 6, 7 and 8) the protrusions in the mass layer are represented as concentric with the openings in the separation layer, this is not an essential requirement of the invention, and in the top view of a possible device of the invention the centre of the shape representing the protrusion (rectangle, circle, ...) may not coincide with the centre of the shape representing the opening.

[0041] 9 illustrates another possible device 90 of the present invention. Device 90 is shown in the figure in a top view (lower part of the figure) and in a cross-section along line A-A' of the top view (upper part of the figure). In this embodiment, separation layer 11 and mass layer 12 are similar to those of device 10, but in this case, instead of multiple protrusions 14a (or 14b-14f), there is a single protrusion 91 on the second surface of layer 12 in the form of a regular mesh. In the case shown in the figure, mesh 91 defines a rectangular lattice, but it could also be, for example, square, triangular, or hexagonal.

[0042] Figure 10 shows another possible device 100 of the invention. This device is similar to device 90, except that in this embodiment the protrusions 101 are in the form of an irregular lattice.

[0043] Finally, FIG. 11 schematically illustrates another possible embodiment of a device of the present invention. Device 110 is irregular in thickness and shape. Separation layer 111 and mass layer 112 are not uniform in thickness, and the cross section of the device is not flat. While the protrusions 114 are shown as all equal and arranged according to a regular pattern, they again may not all be equal and may be irregularly arranged, as in FIG. 3. Furthermore, while in this illustrative example, protrusions 114 are shown on the second surface 13 of the mass layer, they could also be on the first surface of the mass layer, as shown in FIG. 5. Also, protrusions on either surface of the mass layer could be combined with openings in the separation layer, as in devices 60, 70, and 80. [Example]

[0044] The present invention is further illustrated by the following examples.

[0045] "Example 1" A sound insulating device according to the invention was manufactured having the shape shown in Figure 12 and the dimensional and physical characteristics described below. The device had lateral dimensions of 1000 mm x 1200 mm, although only a representative portion of the device is shown in Figure 12.

[0046] The device 120 was fabricated from a separation layer 121 made of polyurethane foam with a thickness of 10 mm and a static Young's modulus of 80 kPa. The separation layer was square (in the top view of the device) and contained a series of recesses 122 arranged according to a periodic array of squares. The recesses had a lateral size of 15 mm × 15 mm and a depth of 8 mm, i.e., they did not penetrate the thickness of the separation layer, and the distance between the centers of two adjacent recesses was 30 mm.

[0047] The mass layer 12 has a thickness of 0.6 mm and a density of 2000 kg / m 3The mass layer was made of a mineral-filled thermoplastic polymer with a static Young's modulus of 300 MPa. On the surface 13 of the mass layer facing away from the separating layer, there were protrusions 14 made of the same material as the mass layer. The mass layer and the protrusions were manufactured together as a single part by injection molding. The protrusions 14 had the shape of prisms with a square base of 7 mm lateral size and a height of 10 mm, and were arranged according to a square array concentric with the trace of the recesses 122, as shown in the figure.

[0048] "Example 2" (Comparison) A prior art sound insulating device was fabricated having the same lateral dimensions as the device of Example 1.

[0049] This device had a separation layer of 10 mm uniform thickness (without recesses) made of the same polyurethane foam as in Example 1. The mass layer of this comparative device was made of the same polymer as in Example 1, but had a uniform thickness of 1 mm and no protrusions. The resulting device had a total weight per unit area nearly equivalent to that of the device of the present invention made as described in Example 1.

[0050] "Example 3" The sound insulation properties of the devices fabricated as described in Examples 1 and 2 were measured.

[0051] The tests were performed in accordance with ISO standard 15186-1. According to this standard, measurements are performed by placing the sample to be tested in a room divided into a reverberation room, where the sound source is located, and a reception room, where the sound detector is located. The two rooms are arranged vertically, with the reception room above the reverberation room. The two rooms are separated by a support frame with an opening essentially the same size as the sample to be tested. The edges of the sample are placed on the frame and sealed to the frame with mastic to avoid sound leakage between the two rooms.

[0052] The difference, measured in dB, between the sound pressure level of the excitation in the reverberation chamber and the level in the receiving chamber is the transmission loss R, calculated according to the formula: R=L excitation -L reception +10·log(S / A) During the ceremony, L is the measured level, S is the test window area (opening in the support frame), A is the equivalent sound absorption area in the receiving room.

[0053] Measurements were carried out at different frequency values, namely 200 Hz, 250 Hz, 315 Hz, 400 Hz, 500 Hz, 630 Hz, 800 Hz, 1000 Hz, 1250 Hz, 1600 Hz and 2000 Hz. The measured values ​​are reported in Figure 13 as transmission loss TL as a function of frequency. The values ​​measured for the sample of the invention are represented by a solid line, and the values ​​measured for the prior art sample are represented by a dotted line (although the spectrum of the above frequencies is sampled only at the given values, the results are represented by broken lines).

[0054] From the two curves in Figure 13, it is clear that the device of the present invention has sound isolation properties that are comparable to those of the prior art device in part of the frequency spectrum, and has improved properties within the frequency range between 630 Hz and 1000 Hz.

Claims

1. Static Young's modulus from 1 kPa to 1 MPa and 1 kg / m ３ to 500 kg / m ３ a first layer (11, 51, 61, 71, 81, 111, 121) of a first material having a density in the range of a second layer (12, 112) of a second material having a first surface attached to the surface of the first layer and a second surface (13) facing away from the first surface; a static Young's modulus of 10 MPa to 2500 MPa and a strength of 500 kg / m ３ to 8000 kg / m ３ Density up to 0.5 kg / m ２ to 20 kg / m ２ a protrusion or a plurality of individual protrusions (14, 14a, 14b, 14c, 14d, 14e, 14f, 31, 41, 52, 91, 101, 114) in the form of a mesh made from a material having a weight per unit area of ​​up to 1000 kJ / cm, wherein the contact area of ​​each of the individual protrusions is not greater than 2% of the area of ​​the first surface or the second surface of the second layer, and the total contact area of ​​the protrusion or the plurality of individual protrusions is 10% to 60% of the area of ​​the first surface or the second surface of the second layer; Equipped with A metamaterial sound insulation device (10, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120), wherein the second material has the same static Young's modulus and the same weight per unit area as the protrusions.

2. The metamaterial sound insulation device of claim 1 , wherein the first material is polyurethane foam.

3. 3. The metamaterial sound insulation device of claim 1, wherein the second material is a felt of natural or synthetic fibers, or a polymer selected from polyurethane, polyvinyl chloride, polyester, polyolefin, and polyamide.

4. 4. The metamaterial sound insulation device of claim 1, wherein the protrusions are attached to the second layer by adhesive.

5. 4. The metamaterial sound insulation device of claim 1, wherein the protrusions are integral with the second layer.

6. 6. The metamaterial sound insulation device of claim 1, wherein a plurality of individual protrusions are disposed on either the first surface or the second surface of the second layer according to a regular, periodic pattern.

7. 6. The metamaterial sound insulation device (30) of claim 1, wherein a plurality of individual protrusions (31) are disposed in a random arrangement on either the first surface or the second surface of the second layer.

8. 6. The metamaterial sound insulation device (90) of claim 1, comprising single protrusions (91) in the form of a regularly configured mesh defining a square, rectangular, triangular, or hexagonal pattern.

9. 6. The metamaterial sound insulation device (100) of any one of claims 1 to 5, comprising a single protrusion (101) in the form of a mesh with an irregular shape.

10. 10. The metamaterial sound insulation device of claim 1, wherein the first layer has an opening through its entire thickness, or a recess in the surface that is in contact with the first surface of the second layer, or a cavity in the surface opposite the surface that is in contact with the second layer.

11. 11. The metamaterial sound insulation device (50, 60, 70, 80, 120) of claim 10, wherein the openings (62), the recesses (72), or the cavities (82, 122) are arranged in the first layer (51, 61, 71, 81, 121) according to a regular, periodic pattern.

12. 12. The metamaterial sound insulation device (50) of claim 11, wherein the first layer (51) has a recess at the surface in contact with the second layer (12) that is completely occupied by a protrusion (52) present on the first surface of the second layer (12).

13. The metamaterial sound insulation device of claim 10 , wherein the openings, recesses, or cavities are arranged in a random arrangement in the first layer.

14. 14. The metamaterial sound insulation device (50, 60, 70, 80) according to any one of claims 10 to 13, wherein, in a top view of the device, the protrusions (14, 52) on the second layer (12) are located at positions that essentially correspond to positions of the openings (62), the recesses (72) or the cavities (82, 122) in the first layer (51, 61, 71, 81, 121).

15. 15. The metamaterial sound insulation device (10, 30, 40, 90, 100) of any one of claims 1 to 14, wherein the first layer (11) has a uniform thickness.

16. 15. The metamaterial sound insulation device (50, 60, 70, 80, 110, 120) of any one of claims 1 to 14, wherein the first layer (51, 61, 71, 81, 111, 121) has a non-uniform thickness.

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