Soundproofing materials and objects

Abstract

The soundproofing material comprises a plurality of metaatoms, each having a membrane portion and a support portion extending in a cylindrical shape to support the membrane portion, and connecting portions that connect the support portions of the plurality of metaatoms, wherein the membrane portion is positioned at a location different from the connecting portions in the direction in which the support portions extend. The object comprises a plurality of metaatoms, each having a membrane portion and a support portion extending in a cylindrical shape to support the membrane portion, and connecting portions that connect the support portions of the plurality of metaatoms, wherein the membrane portion is positioned at a location different from the connecting portions in the direction in which the support portions extend.

Description

[Technical Field]

[0001] This disclosure relates to soundproofing materials and objects. [Background technology]

[0002] Japanese Patent Publication No. 6879369 describes an acoustic metamaterial soundproofing material. In this acoustic metamaterial soundproofing material, a lattice structure having a honeycomb structure is bonded to a latex rubber sheet, thereby dividing the latex rubber sheet into multiple compartments. [Overview of the project] [Problems that the invention aims to solve]

[0003] Ideally, soundproofing materials made of acoustic metamaterials should have a transmission loss frequency characteristic in which the transmission loss increases as the frequency decreases, with the resonant frequency of the membrane (compartment) as the boundary. However, when the Discloser fabricated a soundproofing material made of acoustic metamaterials as described in Japanese Patent Publication No. 6879369 and measured its transmission loss, while a trend toward the transmission loss frequency characteristic of acoustic metamaterials was observed, it was not sufficient.

[0004] The purpose of this disclosure is to provide soundproofing materials and objects that can improve the transmission loss frequency characteristics of acoustic metamaterials. [Means for solving the problem]

[0005] The Discloser has diligently researched the above-mentioned problem and obtained the following findings. In the soundproofing material of the acoustic metamaterial described in Japanese Patent No. 6879369, a lattice structure having a honeycomb structure is joined to a latex rubber sheet, so that multiple compartments are interconnected. For this reason, it is presumed that each compartment is affected by the vibrations of the other compartments, and the transmission loss frequency characteristics of the acoustic metamaterial were not sufficiently obtained. This disclosure is made based on the above findings.

[0006] [1] The soundproofing material according to the present disclosure comprises a plurality of metaatoms, each having a membrane portion and a support portion extending in a cylindrical shape to support the membrane portion, and a connecting portion connecting each of the support portions of the plurality of metaatoms, wherein the membrane portion is positioned at a location different from the connecting portion in the direction of extension of the support portion.

[0007] In this soundproofing material, each of the multiple metaatoms has a membrane portion and a support portion that extends in a cylindrical shape to support the membrane portion. Therefore, each membrane portion of the multiple metaatoms vibrates in response to sound waves, functioning as a soundproofing material of the acoustic metamaterial. The support portions of the multiple metaatoms are connected to each other by connectors, but the membrane portions are positioned at different locations from the connectors in the direction of extension of the support portions. In other words, each membrane portion of the multiple metaatoms is independent of the others. As a result, each membrane portion of the multiple metaatoms is less affected by the vibrations of other membrane portions and can easily vibrate independently. That is, each membrane portion of the multiple metaatoms can easily perform local membrane vibrations without being affected by the vibrations of other membrane portions. This makes it possible to improve the transmission loss frequency characteristics of the acoustic metamaterial.

[0008] [2] In the soundproofing material described in [1], if one end of the support portion is designated as the first end and the other end of the support portion is designated as the second end, the connecting portion may connect each of the support portions of the multiple metaatoms at the first end. In this soundproofing material, the connecting portion connects each of the support portions of the multiple metaatoms at the first end of the support portion. This makes it easier to manufacture the soundproofing material. In addition, the connecting portion can be brought into contact with the installation surface of the soundproofing material. This makes it possible to install the soundproofing material more stably compared to the case where multiple support portions are brought into contact with the installation surface individually. In addition, it becomes easier to curve the soundproofing material so that it is convex on the opposite side of the multiple support portions from the connecting portion. This makes it possible to increase the degree of freedom in installing the soundproofing material.

[0009] [3] In the soundproofing material described in [1] or [2], if one end of the support portion is designated as the first end and the other end of the support portion is designated as the second end, the membrane portion may be connected to the second end of the support portion. In this soundproofing material, the membrane portion is connected to the second end of the support portion. This makes it possible to improve the ease of manufacturing the soundproofing material.

[0010] [4] In the soundproofing material described in [1] or [2], if one end of the support is designated as the first end, the other end of the support is designated as the second end, and the space between the first and second ends of the support is designated as the intermediate section, the membrane portion may be connected to the intermediate section of the support. In this soundproofing material, the membrane portion is connected to the intermediate section of the support. Therefore, even when the first or second end of the support is in contact with the installation surface of the soundproofing material, the membrane portion can be separated from the installation surface. As a result, the inhibition of the membrane portion's vibration by the installation surface is suppressed, and the transmission loss frequency characteristics of the acoustic metamaterial can be improved.

[0011] [5] In the soundproofing material described in any of [1] to [4], the membrane portion does not need to have holes. In this soundproofing material, the membrane portion does not have holes. Therefore, it is easier to obtain the transmission loss frequency characteristics of the acoustic metamaterial, and the soundproofing performance of the membrane portion can be improved.

[0012] In the soundproofing material described in [6] and [5], the support and connecting parts do not need to have holes. In this soundproofing material, the support and connecting parts do not have holes. Therefore, it is easier to obtain the transmission loss frequency characteristics of the acoustic metamaterial and the overall soundproofing performance of the soundproofing material can be improved.

[0013] In the soundproofing material described in any of [1] to [6], if one end of the support portion is designated as the first end and the other end of the support portion as the second end, the support portion may taper from the first end side towards the second end side. In this soundproofing material, the support portion tapers from the first end side towards the second end side. Therefore, even if the support portions of multiple meta atoms are close to each other, it becomes easier to curve the soundproofing material so that it is convex toward the first end side relative to the second end. This increases the degree of freedom in installing the soundproofing material.

[0014] [8] In any of the soundproofing materials described in [1] to [7], the resonant frequency of the membrane may be between 500 Hz and 20,000 Hz. In this soundproofing material, the resonant frequency of the membrane is between 500 Hz and 20,000 Hz. Therefore, it can function appropriately as a soundproofing material. The resonant frequency of the membrane can be set by the surface density (mass per unit area) of the membrane, the surface stiffness of the membrane, the Poisson's ratio of the membrane, the Young's modulus of the membrane, the film thickness of the membrane, the area equivalent circle radius of the membrane, etc.

[0015] [9] In the soundproofing materials described in [1] to [8], the film thickness of the membrane portion may be 5 μm or more and 1000 μm or less. In this soundproofing material, the film thickness of the membrane portion is 5 μm or more and 1000 μm or less. Therefore, the membrane portion can be appropriately vibrated while ensuring ease of manufacture of the soundproofing material.

[0016]

[10] In the soundproofing materials described in [1] to [9], the area of ​​the membrane is 0.1 cm². 2 More than 10cm 2 The following is also acceptable: In this soundproofing material, the area of ​​the membrane is 0.1 cm². 2 More than 10cm 2 The following is the reason. Therefore, the membrane can be vibrated appropriately.

[0017]

[11] In the soundproofing material according to any one of [1] to

[10] , the length of the support portion in the extending direction thereof may be not less than 1 mm and not more than 80 mm. In this soundproofing material, the length of the support portion in the extending direction thereof is not less than 1 mm and not more than 80 mm. Accordingly, it is possible to achieve high rigidity of the plurality of support portions while reducing the thickness of the soundproofing material.

[0018]

[12] In the soundproofing material according to any one of [1] to

[11] , a ratio of the length of the support portion in the extending direction thereof to an area-equivalent circle radius of the membrane portion may be not less than 1 and not more than 30. In this soundproofing material, when the ratio of the length of the support portion in the extending direction thereof to the area-equivalent circle radius of the membrane portion is not less than 1, sound insulation performance is effectively exhibited by membrane vibration, and when the ratio is not more than 30, ease of manufacture can be ensured.

[0019]

[13] In the soundproofing material according to any one of [1] to

[12] , the thickness of the support portion may be not less than 50 μm and not more than 2000 μm. In this soundproofing material, the thickness of the support portion is not less than 50 μm and not more than 2000 μm. Accordingly, weight reduction of the soundproofing material can be achieved while ensuring the supporting force for the membrane portion.

[0020]

[14] In the soundproofing material according to any one of [1] to

[13] , the connection portion may be formed in a sheet shape. In this soundproofing material, the connection portion is formed in a sheet shape. Accordingly, the entire soundproofing material can be easily curved. This makes it possible to increase the degree of freedom in installing the soundproofing material.

[0021]

[15] In the soundproofing material according to

[14] , the thickness of the connection portion may be not less than 300 μm and not more than 2000 μm. In this soundproofing material, the thickness of the connection portion is not less than 300 μm and not more than 2000 μm. Accordingly, weight reduction of the entire soundproofing material can be achieved while suppressing breakage of the connection portion.

[0022]

[16] In the soundproofing material described in [1] to

[15] , the connection part may connect the support parts of multiple metaatoms such that the support parts of adjacent metaatoms among the multiple metaatoms are in contact with each other. In this soundproofing material, the connection part connects the support parts of multiple metaatoms such that the support parts of adjacent metaatoms among the multiple metaatoms are in contact with each other. As a result, the total area of ​​the membrane per unit area can be increased. This makes it possible to improve the soundproofing performance of the soundproofing material.

[0023]

[17] In the soundproofing material described in [1] to

[16] , the connection part may connect the support parts of multiple metaatoms such that the support parts of adjacent metaatoms are spaced apart from each other. In this soundproofing material, the connection part connects the support parts of multiple metaatoms such that the support parts of adjacent metaatoms are spaced apart from each other. This makes it easier to bend the soundproofing material. This increases the degree of freedom in installing the soundproofing material.

[0024]

[18] The object according to the present disclosure comprises a plurality of metaatoms, each having a membrane portion and a support portion extending in a cylindrical shape to support the membrane portion, and a connecting portion connecting each of the support portions of the plurality of metaatoms, wherein the membrane portion is positioned differently from the connecting portion in the direction of extension of the support portion.

[0025] In this object, each of the multiple metaatoms has a membrane portion and a support portion that extends in a cylindrical shape to support the membrane portion. Therefore, each membrane portion of the multiple metaatoms vibrates in response to sound waves, functioning as an acoustic metamaterial. The support portions of the multiple metaatoms are connected to each other by connectors, but the membrane portions are positioned at different locations from the connectors in the direction of extension of the support portions. In other words, each membrane portion of the multiple metaatoms is independent of the others. As a result, each membrane portion of the multiple metaatoms is less affected by the vibrations of other membrane portions and can easily vibrate independently. That is, each membrane portion of the multiple metaatoms can easily perform local membrane vibrations without being affected by the vibrations of other membrane portions. This makes it possible to improve the transmission loss frequency characteristics of the acoustic metamaterial.

[0026] In the object described in

[19]

[18] , if one end of the support is designated as the first end and the other end of the support is designated as the second end, the connecting portion may connect each of the support portions of the multiple metaatoms at the first end. In this object, the connecting portion connects each of the support portions of the multiple metaatoms at the first end of the support. This makes it easier to manufacture the object. In addition, the connecting portion can be brought into contact with the mounting surface of the object. This makes it possible to install the object more stably than when the multiple support portions are brought into contact with the mounting surface individually. In addition, it becomes easier to curve the object so that it is convex toward the opposite side of the multiple support portions from the connecting portion. This makes it possible to increase the degree of freedom in installing the object.

[0027] In the object described in

[20]

[18] or

[19] , if one end of the support is designated as the first end and the other end of the support is designated as the second end, the membrane portion may be connected to the second end of the support. In this object, the membrane portion is connected to the second end of the support. This makes it possible to improve the ease of manufacturing the object.

[0028] In the object described in

[21]

[18] or

[19] , if one end of the support is designated as the first end, the other end of the support is designated as the second end, and the space between the first and second ends of the support is designated as the intermediate section, the membrane may be connected to the intermediate section of the support. In this object, the membrane is connected to the intermediate section of the support. Therefore, even when the first or second end of the support is in contact with the mounting surface of the object, the membrane can be separated from the mounting surface. This suppresses interference of the membrane's vibration by the mounting surface, thereby improving the transmission loss frequency characteristics of the acoustic metamaterial.

[0029] In the object described in any of

[22]

[18] to

[21] , the membrane portion does not need to have holes. In this object, the membrane portion does not have holes. Therefore, the transmission loss frequency characteristics of the acoustic metamaterial can be easily obtained, and the sound insulation performance of the membrane portion can be improved.

[0030] In the object described in

[23] and

[22] , the support and connecting parts do not need to have holes. In this object, neither the support nor the connecting parts have holes. Therefore, the transmission loss frequency characteristics of the acoustic metamaterial can be easily obtained, and the sound insulation performance of the entire object can be improved.

[0031] In the object described in any of

[24]

[18] to

[23] , if one end of the support is designated as the first end and the other end as the second end, the support may taper from the first end towards the second end. In this object, the support tapers from the first end towards the second end. Therefore, even if the support parts of multiple metaatoms are close to each other, it becomes easier to curve the object so that it is convex toward the first end relative to the second end. This increases the degree of freedom in setting up the object.

[0032] In the object described in any of

[25]

[18] to

[24] , the resonant frequency of the membrane portion may be between 500 Hz and 20000 Hz. In this object, the resonant frequency of the membrane portion is between 500 Hz and 20000 Hz. Therefore, it can be made to function properly as an object. The resonant frequency of the membrane portion can be set by the surface density (mass per unit area) of the membrane portion, the surface stiffness of the membrane portion, the Poisson's ratio of the membrane portion, the Young's modulus of the membrane portion, the film thickness of the membrane portion, the area equivalent circle radius of the membrane portion, etc.

[0033] In the object described in any of

[26]

[18] to

[25] , the film thickness of the membrane portion may be 5 μm or more and 1000 μm or less. In this object, the film thickness of the membrane portion is 5 μm or more and 1000 μm or less. Therefore, the membrane portion can be appropriately vibrated while ensuring ease of manufacturing of the object.

[0034] In the object described in any of

[27]

[18] ~

[26] , the area of ​​the membrane is 0.1 cm². 2 More than 10cm 2 The following is also acceptable: In this object, the area of ​​the membrane is 0.1 cm². 2 More than 10cm 2 The following is the reason. Therefore, the membrane can be vibrated appropriately.

[0035]

[28] In the object described in any of

[18] to

[27] , the length of the support portion in the extending direction may be 1 mm or more and 80 mm or less. In this object, the length of the support portion in the extending direction is 1 mm or more and 80 mm or less. Therefore, it is possible to make the object thinner while increasing the rigidity of multiple support portions.

[0036] In the object described in any of

[18] to

[28] , the ratio of the length of the support portion in the extending direction to the area equivalent circle radius of the membrane portion may be 1 or more and 30 or less. In this object, if the ratio of the length of the support portion in the extending direction to the area equivalent circle radius of the membrane portion is 1 or more, sound insulation is effectively achieved by membrane vibration, and if this ratio is 30 or less, ease of manufacture can be ensured.

[0037] In the object described in any of

[30]

[18] to

[29] , the wall thickness of the support portion may be 50 μm or more and 2000 μm or less. In this object, the wall thickness of the support portion is 50 μm or more and 2000 μm or less. Therefore, it is possible to reduce the weight of the object while ensuring the support capacity of the membrane portion.

[0038] In the object described in any of

[31]

[18] to

[30] , the connecting portion may be formed in a sheet-like manner. In this object, the connecting portion is formed in a sheet-like manner. This makes it easier to bend the entire object. This increases the degree of freedom in the installation of the object.

[0039]

[32] In the object described in

[31] , the wall thickness of the connecting portion may be 300 μm or more and 2000 μm or less. In this object, the wall thickness of the connecting portion is 300 μm or more and 2000 μm or less. Therefore, it is possible to reduce the overall weight of the object while suppressing fracture of the connecting portion.

[0040] In the object described in any of

[33]

[18] to

[32] , the connecting portion may connect the support portions of multiple metaatoms such that the support portions of adjacent metaatoms among the multiple metaatoms are in contact with each other. In this object, the connecting portion connects the support portions of multiple metaatoms such that the support portions of adjacent metaatoms among the multiple metaatoms are in contact with each other. As a result, the total area of ​​the film per unit area can be increased. This makes it possible to improve the sound insulation performance of the object.

[0041] In the object described in any of

[34]

[18] to

[33] , the connecting part may connect the support parts of multiple metaatoms such that the support parts of adjacent metaatoms are spaced apart from each other. In this object, the connecting part connects the support parts of multiple metaatoms such that the support parts of adjacent metaatoms are spaced apart from each other. This makes it easier to bend the object. This increases the degree of freedom in setting up the object. [Effects of the Invention]

[0042] According to this disclosure, the transmission loss frequency characteristics of acoustic metamaterials can be improved. [Brief explanation of the drawing]

[0043] [Figure 1] Figure 1 is a perspective view showing an example of a soundproofing material according to an embodiment. [Figure 2] Figure 2 is a cross-sectional perspective view of the soundproofing material shown in Figure 1. [Figure 3] Figure 3 is a schematic cross-sectional view of the soundproofing material shown in Figure 1. [Figure 4] Figure 4 is a schematic cross-sectional view of a modified soundproofing material. [Figure 5] Figure 5 is a schematic cross-sectional view of a modified soundproofing material. [Figure 6] Figure 6 is a schematic cross-sectional view of a modified soundproofing material. [Figure 7] Figure 7 is a schematic cross-sectional view of a modified soundproofing material. [Figure 8] Figure 8 is a schematic cross-sectional view of a modified soundproofing material. [Figure 9] Figure 9 is a schematic cross-sectional view of a modified soundproofing material. [Figure 10] Figure 10 is a schematic cross-sectional view of a modified soundproofing material. [Figure 11] Figure 11 is a plan view showing the soundproofing material of Example 1. [Figure 12] Figure 12 is a cross-sectional view of section XII shown in Figure 11. [Figure 13] Figure 13 is a cross-sectional view along the line XIII-XIII shown in Figure 11. [Figure 14] Figure 14 is a plan view showing the soundproofing material of Comparative Example 1. [Figure 15] Figure 15 is a cross-sectional view along the XV-XV line shown in Figure 14. [Figure 16] Figure 16 is a plan view showing the soundproofing material of Comparative Example 2. [Figure 17] Figure 17 is a cross-sectional view of section XVII shown in Figure 16. [Figure 18]Figure 18 is a cross-sectional view along the line XVIII-XVIII shown in Figure 16. [Figure 19] Figure 19 is a graph showing measurement results to verify the method of installing soundproofing material on acoustic pipes. [Figure 20] Figure 20 is a graph showing the measurement results for Examples 1 and 2. [Figure 21] Figure 21 is a graph showing the measurement results for Comparative Examples 1 to 3. [Figure 22] Figure 22 is a photograph of the soundproofing material of Example 3. [Figure 23] Figure 23 is a plan view showing the soundproofing material of Example 3. [Figure 24] Figure 24 is a cross-sectional view of section XXIV shown in Figure 23. [Figure 25] Figure 25 is a partial cross-sectional view along the line XXV-XXV shown in Figure 23. [Figure 26] Figure 26 is a graph showing the measurement results for Examples 3 to 7. [Figure 27] Figure 27 is a graph showing the relationship between the resonant frequency of the film portion and the maximum transmission loss for Examples 3 to 7. [Modes for carrying out the invention]

[0044] Hereinafter, embodiments of the soundproofing material and object according to this disclosure will be described in detail with reference to the drawings. This embodiment applies the object according to this disclosure to a soundproofing material. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant descriptions are omitted.

[0045] Figure 1 is a perspective view showing an example of a soundproofing material according to the embodiment. Figure 2 is a cross-sectional perspective view of the soundproofing material shown in Figure 1. Figure 3 is a schematic cross-sectional view of the soundproofing material shown in Figure 1. The soundproofing material 1 shown in Figures 1 to 3 is a soundproofing material made of acoustic metamaterial. Examples of applications and installation forms for the soundproofing material 1 include the automotive sector, building and infrastructure applications, and the electronic equipment sector.

[0046] In the automotive sector, for example, by installing soundproofing material 1 in dash silencers, floor silencers, etc., significant weight reduction can be achieved compared to installing soundproofing material with a large area weight in accordance with the mass law. Also in the automotive sector, for example, by installing soundproofing material 1 in door panels, roofs, undercovers, around batteries, etc., the intrusion of external noise such as road noise or rain noise into the vehicle can be suppressed.

[0047] In building and infrastructure applications, for example, by installing soundproofing material 1 on the surface or intermediate layer of partitions such as walls, floors, or ceilings, the soundproofing of buildings and other structures can be improved.

[0048] In the field of electronic equipment, for example, by installing soundproofing material 1 around noise sources such as fans and motors, noise such as cogging noise generated from noise sources such as fans and motors can be reduced.

[0049] As shown in Figures 1 to 3, the soundproofing material 1 according to this embodiment comprises a plurality of metaatoms 2 and a connecting portion 5.

[0050] Each of the multiple metaatoms 2 has a film portion 3 and a support portion 4. The film portion 3 refers to the film portion 3 of each of the multiple metaatoms 2, and the support portion 4 refers to the support portion 4 of each of the multiple metaatoms 2.

[0051] The membrane portion 3 is the part that vibrates in response to sound waves and is the main component that performs its function as an acoustic metamaterial. For example, an elastic sheet-like member can be used as the membrane portion 3.

[0052] The constituent material of the elastic sheet-like member is not particularly limited; any material with elasticity may be used. The film portion 3 being elastic means that it is composed of a material whose Young's modulus is within the range of 0.001 to 70 [GPa]. The Young's modulus of resin is measured according to JIS K7161-1 (2014). The Young's modulus of metal is measured according to JIS Z2241 (2011). The Young's modulus of rubber is measured according to JIS Z6251 (2010).

[0053] For example, the constituent material of the membrane portion 3 can be rubber material, resin material, metal material, paper material, or a material with cushioning properties such as an air cushion.

[0054] Examples of rubber materials constituting the membrane portion 3 include vulcanized rubbers such as latex rubber, chloroprene rubber (CR), styrene-butadiene rubber (SBR), ethylene-propylene-diene rubber (EPDM), and acrylonitrile-butadiene rubber (NBR), as well as thermoplastic elastomers such as olefin-based (TPO), dynamically cross-linked (TPV), styrene-based (TPS), polyurethane-based (TPU), and polyester-based (TPEE).

[0055] Examples of resin materials constituting the membrane portion 3 include polyethylene (e.g., low-density polyethylene, high-density polyethylene, etc.), polyolefin resins such as polypropylene, polyvinyl chloride resin, acrylic resin, methacrylic resin, acrylonitrile-butadiene-styrene resin, vinyl acetate resin, ethylene-vinyl acetate resin, and styrene-butadiene resin.

[0056] Examples of thermosetting resins constituting the film portion 3 include silicone resin, urethane resin, melamine resin, thermosetting acrylic resin, urea resin, phenol resin, resorcinol resin, alkylresorcinol resin, epoxy resin, and thermosetting polyester. Furthermore, as the thermosetting resin constituting the film portion 3, resin precursors such as urethane resin prepolymers, urea resin prepolymers (initial condensates), phenol resin prepolymers (initial condensates), diallyl phthalate prepolymers, acrylic oligomers, polyvalent isocyanates, methacrylate monomers, and diallyl phthalate monomers may be used as prepolymers, oligomers, and monomers that produce these resins.

[0057] Examples of metal materials that make up the film portion 3 include copper and aluminum.

[0058] The support portion 4 extends in a cylindrical shape and supports the membrane portion 3. That is, the support portion 4 supports the membrane portion 3 as an acoustic metamaterial of the membrane portion 3, enabling local membrane vibration. The support portion 4 is positioned to surround the membrane portion 3 and is connected to the membrane portion 3.

[0059] Here, the direction in which the support portion 4 extends in a cylindrical shape is called the extension direction LD. In the extension direction LD, one end of the support portion 4 is designated as the first end 41, the other end of the support portion 4 is designated as the second end 42, and the area between the first end 41 and the second end 42 is designated as the intermediate portion 43. The intermediate portion 43 does not include the first end 41 or the second end 42.

[0060] The support portion 4 may support the membrane portion 3 at any position in the extending direction LD. For example, the support portion 4 may support the membrane portion 3 at the first end portion 41, at the second end portion 42, or at the intermediate portion 43. In this embodiment, the support portion 4 will be described as supporting the membrane portion 3 at the second end portion 42.

[0061] The cylindrical shape of the support portion 4 is not particularly limited and can be, for example, cylindrical, polygonal, etc. Examples of polygonal shapes include triangular, square, and hexagonal shapes. Furthermore, the cylindrical shape of the support portion 4 may be the same throughout the entire length of the extension direction LD of the support portion 4, or it may change along the extension direction LD. For example, the support portion 4 may be formed as a cylindrical shape with the same cross-sectional shape from the tip on the first end 41 side to the tip on the second end 42 side, or it may be formed as a tapered cylindrical shape that narrows from the first end 41 side to the second end 42 side, or it may be formed as a tapered cylindrical shape that narrows from the second end 42 side to the first end 41 side. In this embodiment, the support portion 4 will be described as being formed as a tapered hexagonal cylindrical shape that narrows from the first end 41 side to the second end 42 side.

[0062] The constituent material of the support portion 4 is not particularly limited, and for example, resin materials, rubber materials, metal materials, paper materials, etc., can be used. Examples of resin materials constituting the support portion 4 include thermoplastic resins and thermosetting resins. The constituent material of the support portion 4 may be the same as the constituent material of the film portion 3, or it may be different from the constituent material of the film portion 3.

[0063] Examples of thermoplastic resins that constitute the support portion 4 include polyvinyl chloride resin, polyethylene (e.g., low-density polyethylene, high-density polyethylene, etc.), polyolefin resins such as polypropylene, acrylic resin, methacrylic resin, acrylonitrile-butadiene-styrene resin, vinyl acetate resin, ethylene-vinyl acetate resin, and styrene-butadiene resin.

[0064] Examples of thermosetting resins that constitute the support portion 4 include urethane resin, melamine resin, thermosetting acrylic resin, urea resin, phenol resin, resorcinol resin, alkyl resorcinol resin, epoxy resin, and thermosetting polyester. In addition, resin precursors such as urethane resin prepolymers, urea resin prepolymers (initial condensates), phenol resin prepolymers (initial condensates), diallyl phthalate prepolymers, acrylic oligomers, polyvalent isocyanates, methacrylate monomers, and diallyl phthalate monomers may be used as thermosetting resins that constitute the support portion 4.

[0065] Examples of rubber materials that constitute the support portion 4 include vulcanized rubbers such as latex rubber, chloroprene rubber (CR), styrene-butadiene rubber (SBR), ethylene-propylene-diene rubber (EPDM), and acrylonitrile-butadiene rubber (NBR), as well as thermoplastic elastomers such as olefin-based (TPO), dynamically cross-linked (TPV), styrene-based (TPS), polyurethane-based (TPU), and polyester-based (TPEE).

[0066] Examples of metal materials that make up the support part 4 include copper and aluminum.

[0067] The connecting part 5 connects the support parts 4 of each of the multiple metaatoms 2 to one another. The connecting part 5 integrates the multiple metaatoms 2 to form a structure as a soundproofing material 1. By connecting the support parts 4 of each of the multiple metaatoms 2 to one another, the connecting part 5 positions the multiple metaatoms 2 in predetermined locations within the soundproofing material 1.

[0068] The connecting portion 5 connects the support portions 4 of each of the multiple metaatoms 2 at a different position in the extending direction LD than the film portion 3. In other words, the film portion 3 is positioned at a different position in the extending direction LD than the connecting portion.

[0069] The connecting portion 5 may connect the support portions 4 of the multiple metaatoms 2 at any position in the extending direction LD, as long as it connects the support portions 4 of the multiple metaatoms 2 at a position different from that of the film portion 3 in the extending direction LD. For example, the connecting portion 5 may connect the support portions 4 of the multiple metaatoms 2 at the first end portion 41, at the second end portion 42, or at the intermediate portion 43. In this embodiment, the connecting portion 5 will be described as connecting the support portions 4 of the multiple metaatoms 2 at the first end portion 41.

[0070] The connection part 5 may connect the support parts 4 of multiple metaatoms 2 such that adjacent support parts 4 of multiple metaatoms 2 are in contact with each other, or it may connect the support parts 4 of multiple metaatoms 2 such that adjacent support parts 4 of multiple metaatoms 2 are spaced apart from each other. In this embodiment, the connection part 5 will be described as connecting the support parts 4 of multiple metaatoms 2 such that adjacent support parts 4 of multiple metaatoms 2 are spaced apart from each other.

[0071] The connecting portion 5 may connect the support portions 4 of the multiple metaatoms 2 in any manner. For example, the connecting portion 5 may directly connect adjacent metaatoms 2, or it may extend in a sheet-like manner to connect adjacent metaatoms 2. In this embodiment, the connecting portion 5 will be described as being formed in a sheet-like manner and connecting the support portions 4 of the multiple metaatoms 2.

[0072] The arrangement of the multiple metaatoms 2 formed by the connection portion 5 connecting the support portions 4 of each of the multiple metaatoms 2 to one another is not particularly limited, and examples include a lattice pattern, a staggered pattern, a honeycomb pattern, etc. In this embodiment, the connection portion 5 is described as connecting the multiple metaatoms 2 so that they are arranged in a honeycomb pattern.

[0073] The connecting portion 5 may extend outside the multiple metaatoms 2 so as to surround the entire multiple metaatoms 2, or it may not extend outside the multiple metaatoms 2. In this embodiment, the connecting portion 5 will be described as extending outside the multiple metaatoms 2 so as to surround the entire multiple metaatoms 2.

[0074] The materials used for the connecting portion 5 are not particularly limited, and for example, rubber materials, resin materials, metal materials, paper materials, etc., can be used. The materials used for the connecting portion 5 may be the same as or different from the materials used for the membrane portion 3 or the support portion 4.

[0075] Examples of rubber materials that constitute the connecting portion 5 include vulcanized rubbers such as latex rubber, chloroprene rubber (CR), styrene-butadiene rubber (SBR), ethylene-propylene-diene rubber (EPDM), and acrylonitrile-butadiene rubber (NBR), as well as thermoplastic elastomers such as olefin-based (TPO), dynamically cross-linked (TPV), styrene-based (TPS), polyurethane-based (TPU), and polyester-based (TPEE).

[0076] Examples of resin materials that constitute the connecting portion 5 include polyethylene (e.g., low-density polyethylene, high-density polyethylene, etc.), polyolefin resins such as polypropylene, polyvinyl chloride resin, acrylic resin, methacrylic resin, acrylonitrile-butadiene-styrene resin, vinyl acetate resin, ethylene-vinyl acetate resin, and styrene-butadiene resin.

[0077] Examples of thermosetting resins that constitute the connecting portion 5 include silicone resin, urethane resin, melamine resin, thermosetting acrylic resin, urea resin, phenol resin, resorcinol resin, alkylresorcinol resin, epoxy resin, and thermosetting polyester. Furthermore, as the thermosetting resin constituting the connecting portion 5, resin precursors such as urethane resin prepolymers, urea resin prepolymers (initial condensates), phenol resin prepolymers (initial condensates), diallyl phthalate prepolymers, acrylic oligomers, polyvalent isocyanates, methacrylate monomers, and diallyl phthalate monomers may be used as prepolymers, oligomers, and monomers that produce these resins.

[0078] Examples of metal materials that make up the connecting portion 5 include copper and aluminum.

[0079] In the soundproofing material 1 constructed in this manner, each membrane portion 3 of the multiple metaatoms 2 is independent of one another. That is, each membrane portion 3 of the multiple metaatoms 2 is not adjacent to the connecting portion 5, so adjacent membrane portions 3 are not directly connected. Furthermore, there are no holes in the membrane portions 3, the support portion 4, or the connecting portion 5. In other words, the soundproofing material 1 does not have holes through which sound waves can pass. Each of the multiple metaatoms 2 functions as an acoustic metamaterial soundproofing material. That is, the soundproofing material 1 has a transmission loss frequency characteristic in which the transmission loss of sound waves increases as the frequency of the sound wave decreases, with the resonance frequency of each membrane portion 3 of the multiple metaatoms 2 as the boundary.

[0080] The method for manufacturing the soundproofing material 1 is not particularly limited. For example, the soundproofing material 1 may be manufactured by vacuum molding using a thermoplastic resin sheet, by 3D printing or cutting, or by injection compression molding, in which the membrane portion 3 is compressed to thin the wall after injection molding. These manufacturing methods allow for the integral production of the soundproofing material 1. Alternatively, the soundproofing material 1 may be manufactured by creating an intermediate body that forms the support portion 4 and connecting portion 5 of a plurality of metaatoms 2 by injection molding or the like, and then attaching the membrane portion 3 to each of the support portions 4 of the plurality of metaatoms 2 of the intermediate body.

[0081] As described above, in the soundproofing material 1 according to this embodiment, each of the multiple metaatoms 2 has a membrane portion 3 and a support portion 4 that extends in a cylindrical shape and supports the membrane portion 3. Therefore, each membrane portion 3 of the multiple metaatoms 2 vibrates when it receives sound waves, functioning as a soundproofing material of the acoustic metamaterial. The support portions 4 of the multiple metaatoms 2 are connected to each other by a connecting portion 5, but the membrane portion 3 is positioned at a different location from the connecting portion 5 in the extending direction LD of the support portion 4. In other words, each membrane portion 3 of the multiple metaatoms 2 is independent of each other. Therefore, each membrane portion 3 of the multiple metaatoms 2 is less affected by the vibration of other membrane portions 3 and is more likely to vibrate independently. That is, each membrane portion 3 of the multiple metaatoms 2 is more likely to perform local membrane vibrations that vibrate without being affected by the vibration of other membrane portions 3. This makes it possible to improve the transmission loss frequency characteristics of the acoustic metamaterial.

[0082] Furthermore, in this soundproofing material 1, the connecting portion 5 connects each of the support portions 4 of multiple meta atoms 2 at the first end portion 41 of the support portion 4. This makes it easier to manufacture the soundproofing material 1. In addition, the connecting portion 5 can be brought into contact with the installation surface (not shown) of the soundproofing material 1. This allows for more stable installation of the soundproofing material 1 compared to when the multiple support portions 4 are individually brought into contact with the installation surface. Moreover, it becomes easier to curve the soundproofing material 1 so that it is convex on the opposite side of the multiple support portions 4 from the connecting portion 5 (i.e., it becomes easier to curve it so that the membrane portion 3 side is convex). This increases the degree of freedom in installing the soundproofing material 1.

[0083] Furthermore, in this soundproofing material 1, the membrane portion 3 is connected to the second end portion 42 of the support portion 4. This makes it easier to manufacture the soundproofing material 1. Moreover, by combining this with a configuration in which the connecting portion 5 is connected to the first end portion 41, it is easier to maximize the distance between the membrane portion 3 and the connecting portion 5, and the independence of each membrane portion 3 of the multiple meta atoms 2 can be increased.

[0084] Furthermore, in this soundproofing material 1, there are no holes in the membrane portion 3. This makes it easier to obtain the transmission loss frequency characteristics of the acoustic metamaterial, and also improves the sound wave blocking performance of the membrane portion 3, i.e., the soundproofing performance.

[0085] Furthermore, in this soundproofing material 1, there are no holes in the support part 4 or the connecting part 5. Therefore, it is easier to obtain the transmission loss frequency characteristics of the acoustic metamaterial, and the overall soundproofing performance of the soundproofing material 1 can be improved.

[0086] Furthermore, in this soundproofing material 1, the support portion 4 tapers from the first end portion 41 towards the second end portion 42. Therefore, even if the support portions 4 of multiple meta atoms 2 are arranged in close proximity to each other, it becomes easier to curve the soundproofing material 1 so that the first end portion 41 side (i.e., the connection portion 5 side) is convex relative to the second end portion 42. This improves the conformability of the soundproofing material 1 when installing it on a concave curved surface, for example, and further increases the degree of freedom in installing the soundproofing material 1.

[0087] The resonant frequency of the membrane 3 is appropriately set according to the frequency band of the target sound. For example, the resonant frequency of the membrane 3 may be between 500Hz and 20000Hz, between 1000Hz and 10000Hz, or between 1000Hz and 5000Hz. In this soundproofing material 1, by having the resonant frequency of the membrane 3 within this range, effective soundproofing performance can be achieved in a specific frequency band.

[0088] Here, the resonant frequency of the film portion 3 can be determined by the following equation (1). Equation (1) is described in Japanese Patent Publication No. 6879369. In equation (1), f0 is the resonant frequency of the film portion 3, m is the surface density (mass per unit area) of the film portion 3, k is the surface stiffness of the film portion 3, ν is the Poisson's ratio of the film portion 3, E is the Young's modulus [Pa] of the film portion 3, h is the film thickness [m] of the film portion 3, and a is the area equivalent circle radius [m] of the film portion 3. The area equivalent circle radius of the film portion 3 is the radius of a circle with the same area as the film portion 3.

[0089]

number

[0090] As shown in equation (1), the resonant frequency of the film portion 3 can be adjusted by the surface density of the film portion 3, the surface stiffness of the film portion 3, the Poisson's ratio of the film portion 3, the Young's modulus of the film portion 3, the film thickness of the film portion 3, the area equivalent circle radius of the film portion 3, and so on.

[0091] The film thickness A of the membrane portion 3 (see Figure 3) may be, for example, 5 μm to 1000 μm, 10 μm to 500 μm, or 15 μm to 300 μm. In this soundproofing material 1, having the film thickness A of the membrane portion 3 within this range ensures ease of manufacturing of the membrane portion 3 while making it easier to appropriately vibrate the membrane portion 3 and obtain the desired resonance frequency. That is, if the film thickness A of the membrane portion 3 is 5 μm or more, 10 μm or more, or 15 μm or more, the membrane portion 3 can be given sufficient strength to be easily manufactured. On the other hand, if the film thickness A of the membrane portion 3 is 1000 μm or less, 500 μm or less, or 300 μm or less, the membrane portion 3 can be vibrated to function well as an acoustic metamaterial.

[0092] The area of the membrane portion 3 is, for example, 0.1 cm 2 or more and 10 cm 2 or less, 0.2 cm 2 or more and 3 cm 2 or less, or 0.3 cm 2 or more and 1 cm 2 or less. When the area of the membrane portion 3 falls within this range, the membrane portion 3 can be vibrated appropriately. That is, the area of the membrane portion 3 is 0.1 cm 2 or more, 0.2 cm 2 or more, or 0.3 cm 2 or more, whereby acoustic energy can be appropriately captured in the membrane portion 3. On the other hand, the area of the membrane portion 3 is 10 cm 2 or less, 3 cm 2 or less, or 1 cm 2 or less, whereby generation of unnecessary higher-order mode vibration in the membrane portion 3 can be suppressed, allowing the structure to function favorably as an acoustic metamaterial.

[0093] The equivalent circle radius of the area of the membrane portion 3 may be, for example, 0.2 cm or more and 2 cm or less, 0.25 cm or more and 1 cm or less, or 0.3 cm or more and 0.5 cm or less. When the equivalent circle radius of the area of the membrane portion 3 falls within this range, the membrane portion 3 can be vibrated appropriately. That is, when the equivalent circle radius of the area of the membrane portion 3 is 0.2 cm or more, 0.25 cm or more, or 0.3 cm or more, acoustic energy can be appropriately captured in the membrane portion 3. On the other hand, when the equivalent circle radius of the area of the membrane portion 3 is 2 cm or less, 1 cm or less, or 0.5 cm or less, generation of unnecessary higher-order mode vibration in the membrane portion 3 can be suppressed, allowing the structure to function favorably as an acoustic metamaterial.

[0094] The length B of the support portion 4 in the extending direction LD (see FIG. 3) may be, for example, 1 mm or more and 80 mm or less, 1 mm or more and 50 mm or less, or 3 mm or more and 30 mm or less. When the length B of the support portion 4 falls within this range, it is possible to reduce the overall thickness of the soundproofing material 1 to achieve thinning while ensuring the rigidity required for the support portion 4 to appropriately support the membrane portion 3.

[0095] The ratio of the length B (see Figure 3) of the support portion 4 in the extending direction LD to the area equivalent circle radius of the membrane portion 3 may be, for example, 1 to 30, 1 to 10, or 1 to 5. When the ratio of the length B of the support portion 4 in the extending direction LD to the area equivalent circle radius of the membrane portion 3 is 1 or more, sound insulation is effectively achieved by membrane vibration, and when this ratio is 30 or less, 10 or less, or 5 or less, ease of manufacturing can be ensured.

[0096] The thickness C of the support portion 4 (see Figure 3) may be, for example, 50 μm to 2000 μm, 100 μm to 1000 μm, or 200 μm to 500 μm. By having the thickness C of the support portion 4 within this range, it is possible to reduce the overall weight of the soundproofing material 1 while ensuring sufficient strength to support the membrane portion 3.

[0097] The thickness D of the connecting portion 5 (see Figure 3) may be, for example, 300 μm to 2000 μm, 400 μm to 1500 μm, or 500 μm to 1000 μm. By having the thickness D of the connecting portion 5 within this range, it is possible to reduce the overall weight of the soundproofing material 1 while ensuring sufficient strength to support the support portion 4.

[0098] Furthermore, in this embodiment, since the connecting portion 5 is formed in a sheet shape, the entire soundproofing material 1 can be easily bent. This makes it possible to easily install the soundproofing material 1 on objects of various shapes, such as walls or members with curved surfaces, thereby increasing the degree of installation flexibility.

[0099] If the connecting portion 5 is in sheet form, its thickness D (see Figure 3) may be, for example, 300 μm to 2000 μm, 400 μm to 1500 μm, or 500 μm to 1000 μm. By having the thickness D of the connecting portion 5 within this range, it is possible to reduce the overall weight of the soundproofing material 1 while suppressing the easy breakage of the connecting portion 5.

[0100] Furthermore, in this embodiment, the connecting portion 5 connects multiple support portions 4 of meta atoms 2 such that adjacent support portions 4 are spaced apart from each other. This makes it easier to bend the soundproofing material 1. This increases the degree of freedom in installing the soundproofing material 1.

[0101] While embodiments of this disclosure have been described above, this disclosure is not limited to the embodiments described above, and modifications may be made as appropriate without departing from the spirit of this disclosure.

[0102] For example, as shown in the modified soundproofing material 1A in Figure 4, the support portion may be formed in a cylindrical shape with the same cross-sectional shape from the tip of the first end to the tip of the second end.

[0103] Figure 4 is a schematic cross-sectional view of a modified soundproofing material. The modified soundproofing material 1A shown in Figure 4 is basically the same as the embodiment described above, but differs from the embodiment in that the shape of the support portion 4A is different. As shown in Figure 4, in the modified soundproofing material 1A, each support portion 4A of the multiple meta atoms 2A is formed in a cylindrical shape with the same cross-sectional shape from the tip on the first end 41 side to the tip on the second end 42 side. The membrane portion 3 is connected to the second end 42 of the support portion 4A, and the connecting portion 5 connects each support portion 4A of the multiple meta atoms 2A at the first end 41 of the support portion 4A.

[0104] Thus, even if the support portion 4A is formed in a cylindrical shape with the same cross-sectional shape from the tip on the first end portion 41 side to the tip on the second end portion 42 side, the same effects as in the above embodiment can be obtained.

[0105] Furthermore, as shown in the modified soundproofing material 1B in Figure 5 and the modified soundproofing material 1C in Figure 6, the connecting portion may be formed by connecting the support portions of multiple meta atoms such that adjacent support portions are in contact with each other.

[0106] Figure 5 is a schematic cross-sectional view of a modified soundproofing material. The modified soundproofing material 1B shown in Figure 5 is basically the same as the embodiment described above, but differs from the embodiment in that the connection of the support portion 4 by the connecting portion 5B is different. As shown in Figure 5, in the modified soundproofing material 1B, the connecting portion 5B connects the support portions 4 of multiple metaatoms 2 such that the support portions 4 of adjacent metaatoms 2 are in contact with each other. The membrane portion 3 is connected to the second end portion 42 of the support portion 4, and the connecting portion 5B connects the support portions 4 of multiple metaatoms 2 at the first end portion 41 of the support portion 4.

[0107] In this way, the connecting portion 5B connects the support portions 4 of multiple metaatoms 2 such that the support portions 4 of adjacent metaatoms 2 are in contact with each other, thereby increasing the total area of ​​the film portion 3 per unit area. This improves the sound insulation performance of the sound insulation material 1B.

[0108] Figure 6 is a schematic cross-sectional view of a modified soundproofing material. The modified soundproofing material 1C shown in Figure 6 is basically the same as the embodiment described above, but differs from the embodiment in that the shape of the support portion 4C is different and the way the support portion 4C is connected by the connecting portion 5C is different. As shown in Figure 6, in the modified soundproofing material 1C, each support portion 4C of the multiple metaatoms 2C is formed in a cylindrical shape with the same cross-sectional shape from the tip on the first end 41 side to the tip on the second end 42 side. The connecting portion 5C connects each support portion 4C of the multiple metaatoms 2C such that the support portions 4C of adjacent metaatoms 2C are in contact with each other. The membrane portion 3 is connected to the second end 42 of the support portion 4C, and the connecting portion 5C connects each support portion 4C of the multiple metaatoms 2C at the first end 41 of the support portion 4C.

[0109] In this way, the connecting portion 5C connects the support portions 4C of multiple metaatoms 2C such that the support portions 4C of adjacent metaatoms 2C are in contact with each other, thereby increasing the total area of ​​the film portion 3 per unit area. This improves the sound insulation performance of the sound insulation material 1C.

[0110] In soundproofing material 1C, the support portions 4C of adjacent metaatoms 2C are arranged to be in contact with each other. However, since each of the multiple metaatoms 2C film portions 3 is independent of each other, it becomes less susceptible to the vibration of adjacent film portions 3 and is more likely to vibrate independently.

[0111] Furthermore, as shown in the soundproofing material 1D in Figure 7 and the soundproofing material 1E in Figure 8, the membrane portion may be connected to the intermediate portion of the support portion. Also, the connection portion may connect the support portions of multiple meta atoms in the intermediate portion of the support portion.

[0112] Figure 7 is a schematic cross-sectional view of a modified soundproofing material. The modified soundproofing material 1D shown in Figure 7 is basically the same as the embodiment described above, but differs from the embodiment in that the shape of the support portion 4D is different and the arrangement position of the membrane portion 3D is different. As shown in Figure 7, in the modified soundproofing material 1D, each support portion 4D of the multiple metaatoms 2D is formed in a cylindrical shape with the same cross-sectional shape from the tip on the first end 41 side to the tip on the second end 42 side. In addition, each membrane portion 3D of the multiple metaatoms 2D is connected to the intermediate portion 43 between the first end 41 and the second end 42 of the support portion 4D. The connecting portion 5 connects each support portion 4D of the multiple metaatoms 2D at the first end 41 of the support portion 4D.

[0113] In this way, because the membrane portion 3D is connected to the intermediate portion 43 of the support portion 4D, the membrane portion 3D can be separated from the installation surface whether the first end portion 41 of the support portion 4D is in contact with the installation surface of the soundproofing material 1D, or whether the second end portion 42 of the support portion 4D is in contact with the installation surface of the soundproofing material 1D. As a result, the interference of vibration of the membrane portion 3D by the installation surface is suppressed, and the transmission loss frequency characteristics of the acoustic metamaterial can be improved more reliably.

[0114] Figure 8 is a schematic cross-sectional view of a modified soundproofing material. The modified soundproofing material 1E shown in Figure 8 is basically the same as the embodiment described above, but differs from the embodiment in that the shape of the support portion 4E is different and the arrangement position of the membrane portion 3E is different. As shown in Figure 8, in the modified soundproofing material 1E, each support portion 4E of the multiple metaatoms 2E extends from the first end 41 to the second end 42, is folded back at the second end 42 and extends to the intermediate portion 43, and supports the membrane portion 3E at its tip. Furthermore, each support portion 4E of the multiple metaatoms 2E is formed in a tapered shape that narrows from the first end 41 to the second end 42 until it is folded back at the second end 42, and after being folded back at the second end 42, it is formed in a tapered shape that narrows from the second end 42 to the intermediate portion 43. The connecting portion 5 connects each support portion 4E of the multiple metaatoms 2E at the first end 41 of the support portion 4E.

[0115] In this way, because the membrane portion 3E is connected to the intermediate portion 43 of the support portion 4E, the membrane portion 3E can be separated from the installation surface whether the first end portion 41 of the support portion 4E is in contact with the installation surface of the soundproofing material 1E, or whether the second end portion 42 of the support portion 4E is in contact with the installation surface of the soundproofing material 1E. As a result, the interference of vibration of the membrane portion 3E by the installation surface is suppressed, and the transmission loss frequency characteristics of the acoustic metamaterial can be improved more reliably.

[0116] Furthermore, since the support portion 4E extends from the first end portion 41 to the second end portion 42, is folded back at the second end portion 42 and extends to the intermediate portion 43, and supports the membrane portion 3E at its tip, the soundproofing material 1E can be manufactured by vacuum molding using a thermoplastic resin sheet.

[0117] Furthermore, since the support portion 4E is formed in a tapered shape that narrows from the first end portion 41 to the second end portion 42 until it is folded back at the second end portion 42, and after it is folded back at the second end portion 42, it is formed in a tapered shape that narrows from the second end portion 42 to the intermediate portion 43, the soundproofing material 1E can be manufactured even more easily by vacuum molding using a thermoplastic resin sheet.

[0118] Furthermore, as shown in soundproofing material 1F in Figure 9, the connection does not need to extend to the outside of the multiple meta atoms.

[0119] Figure 9 is a schematic cross-sectional view of a modified soundproofing material. The modified soundproofing material 1F shown in Figure 9 is basically the same as the embodiment described above, but differs from the embodiment in that the shape of the connecting portion 5F is different. As shown in Figure 9, in the modified soundproofing material 1F, the connecting portion 5F does not extend around the multiple meta atoms 2. Alternatively, the connecting portion 5F may be formed to extend outside the multiple meta atoms 2, and then the portion extending outside the multiple meta atoms 2 may be removed to make it not extend around the multiple meta atoms 2.

[0120] Thus, even if the connecting portion 5F does not extend around multiple meta atoms 2, the same effects as in the above embodiment can be obtained.

[0121] Furthermore, as shown in Figure 10, the portion of the soundproofing material 1G may be curved or bent so as to be tapered in shape in the part that supports the membrane portion of the support. Also, the portion of the support that connects to the connecting portion may be curved or bent so as to be tapered in shape.

[0122] Figure 10 is a schematic cross-sectional view of a modified soundproofing material. The modified soundproofing material 1G shown in Figure 10 is basically the same as the embodiment described above, but differs from the embodiment in that the shape of the support portion 4G is different. As shown in Figure 10, in the modified soundproofing material 1G, each support portion 4G of the multiple metaatoms 2G is formed in a tapered cylindrical shape that narrows from the first end 41 to the second end 42. The membrane portion 3 is connected to the second end 42 of the support portion 4G, and the connecting portion 5 connects each support portion 4G of the multiple metaatoms 2G at the first end 41 of the support portion 4G. In the support portion 4G, the second end 42 connected to the membrane portion 3 is curved or bent so that it narrows from the first end 41 to the second end 42. Also, in the support portion 4G, the first end 41 connected to the connecting portion 5 is curved or bent so that it narrows from the first end 41 to the second end 42.

[0123] Thus, even if the first end 41 and the second end 42 of the support portion 4G are curved or bent so that they become thinner from the first end 41 side to the second end 42 side, the same effects as in the above embodiment can be obtained.

[0124] Furthermore, although the above embodiment was described as applying the object relating to this disclosure to a soundproofing material, the object relating to this disclosure may also be applied to materials other than soundproofing materials. [Examples]

[0125] Next, embodiments of the present disclosure will be described. However, the present disclosure is not limited to the embodiments described below.

[0126] (Example 1) As the soundproofing material for Example 1, the soundproofing material shown in Figures 11 to 13 was fabricated. Figure 11 is a plan view showing the soundproofing material of Example 1. Figure 12 is a cross-sectional view of section XII shown in Figure 11. Figure 13 is a cross-sectional view along the line XIII-XIII shown in Figure 11. Note that Figure 12 shows a cross-section along the line XII-XII shown in Figure 13.

[0127] As shown in Figures 11 to 13, first, an intermediate body was fabricated from acrylic resin, consisting of 85 support parts connected by connectors. The connectors were disc-shaped with a diameter E of 107.5 mm and a thickness F of 0.5 mm. The support parts were hexagonal tubes with rounded corners, having a longer diagonal length G of 8.0 mm and a shorter diagonal length H of 6.93 mm. The support parts also had a wall thickness I of 0.5 mm and a length J in the direction of extension of the support part of 10.0 mm. The 85 support parts were then arranged in a honeycomb pattern such that the spacing K between adjacent support parts was 2.0 mm and the pitch L (distance between centers) between adjacent support parts was 9.93 mm.

[0128] Next, a PET (polyethylene terephthalate) film with a thickness M of 0.025 mm was attached to the end of each of the 85 support sections opposite to the connection point. The area of ​​each film section was 0.42 cm². 2 The area equivalent circle radius of each membrane section was 0.36 cm. This yielded the soundproofing material of Example 1.

[0129] (Example 2) The soundproofing material in Example 2 was the same as in Example 1, except that the length J in the extending direction of the support portion was set to 5.0 mm.

[0130] (Comparative Example 1) As the soundproofing material for Comparative Example 1, the soundproofing material shown in Figures 14 and 15 was prepared. Figure 14 is a plan view showing the soundproofing material for Comparative Example 1. Figure 15 is a cross-sectional view taken along the line XV-XV shown in Figure 14.

[0131] As shown in Figures 14 and 15, the soundproofing material for Comparative Example 1 was a disc-shaped soundproofing material made of acrylic resin with a diameter N of 107.5 mm and a thickness O of 0.5 mm.

[0132] (Comparative Example 2) As the soundproofing material for Comparative Example 2, the soundproofing material shown in Figures 16 to 18 was prepared. Figure 16 is a plan view showing the soundproofing material for Comparative Example 2. Figure 17 is a cross-sectional view of section XVII shown in Figure 16. Figure 18 is a cross-sectional view along the line XVIII-XVIII shown in Figure 16.

[0133] As shown in Figures 16 to 18, first, an intermediate body was fabricated by fitting a honeycomb member, which consists of multiple regular hexagonal spaces with rounded corners arranged in a honeycomb pattern, inside a cylindrical member (annular member) with an outer diameter P of 107.5 mm, an inner diameter Q of 88.0 mm, and a length R (thickness) in the extending direction of 10.0 mm, using acrylic resin. The length S of the longer diagonal of the regular hexagonal space was set to 8.0 mm, and the length T of the shorter diagonal was set to 6.93 mm. The multiple regular hexagonal spaces were then densely arranged so that the spacing U between adjacent regular hexagonal spaces was 0.5 mm, and the pitch V (distance between centers) between adjacent regular hexagons was 7.43 mm.

[0134] Next, a PET film with a thickness of 0.025 mm was attached to one end face of the intermediate, dividing the PET film into multiple sections using the intermediate. The area of ​​each section of the PET film divided by the intermediate was 0.42 cm². 2 The equivalent circle radius of each section was 0.36 cm. This yielded the soundproofing material for Comparative Example 2.

[0135] (Comparative Example 3) The soundproofing material in Comparative Example 3 was the same as in Comparative Example 2, except that the length R in the extension direction of the intermediate body was set to 5.0 mm.

[0136] (Transmission loss measurement) Next, the transmission loss of the soundproofing materials of Examples 1 and 2 and Comparative Examples 1 to 3 was measured. For the measurement of transmission loss, a Rion Co., Ltd. Model 9301 vertical incidence sound absorption coefficient / transmission loss measurement system was used, which utilizes an acoustic tube (100 mm inner diameter) of low frequency duct. Sound was then incident perpendicularly onto the soundproofing material installed in the acoustic tube, and the transmission loss (transmission loss frequency characteristics) of the soundproofing material was measured.

[0137] It is known that when measuring the transmission loss of soundproofing materials using acoustic tubes, the vibration of the acoustic tubes makes it difficult to measure the transmission loss of the soundproofing material with high accuracy. Therefore, prior to measuring the transmission loss of the soundproofing material, we investigated the method of installing the soundproofing material relative to the acoustic tubes.

[0138] In verifying the installation methods, a 1mm thick acrylic plate was used as a soundproofing material sample, and the sample was installed in the acoustic tube using the following installation methods 1 to 3. In installation method 1, the sample was installed in the acoustic tube by fastening it by clamping it with the acoustic tube. Installation method 1 is called fastening fixation. In installation method 2, grease was applied to the acoustic tube, and the sample was installed in the acoustic tube by making it adhere to the grease. Installation method 2 is called loose fixing (grease support). In installation method 3, the outer diameter of the sample was made slightly smaller than the inner diameter of the acoustic tube so that a small clearance was formed between the acoustic tube and the sample, and the sample was installed in the acoustic tube by making line contact with the acoustic tube due to the weight of the sample itself. Installation method 3 is called loose fixing (clearance). Then, the transmission loss of the sample was measured for each of installation methods 1 to 3. The measurement results are shown in Figure 19. Figure 19 is a graph showing the measurement results for verifying the installation method of soundproofing material to the acoustic tube.

[0139] Since the sample is a 1mm thick acrylic plate, it exhibits transmission loss frequency characteristics in accordance with the mass law. The mass law states that the greater the mass of the soundproofing material and the higher the frequency of the sound wave, the greater the transmission loss. However, as shown in Figure 19, transmission loss frequency characteristics that do not conform to the mass law were observed in fastening method 1 and loose fixing (grease support) method 2. This is presumed to be due to plate resonance of the sample caused by the sample being fixed to the acoustic tube. In contrast, in loose fixing (clearance) method 3, transmission loss frequency characteristics in accordance with the mass law were observed. This is presumed to be because plate resonance of the sample was suppressed due to the significantly relaxed fixing of the sample.

[0140] Therefore, using the loose fixing (clearance) method of installation method 3, the soundproofing materials of Examples 1 and 2 and Comparative Examples 1 to 3 were installed in acoustic tubes and the transmission loss was measured. The measurement results of Examples 1 and 2 are shown in Figure 20, and the measurement results of Comparative Examples 1 to 3 are shown in Figure 21. Figure 20 is a graph showing the measurement results of Examples 1 and 2. Figure 21 is a graph showing the measurement results of Comparative Examples 1 to 3.

[0141] As shown in Figure 21, the soundproofing material of Comparative Example 1, which conforms to the mass law, exhibits a transmission loss frequency characteristic that conforms to the mass law, where the transmission loss increases as the frequency of the sound wave increases. On the other hand, the soundproofing materials of Comparative Examples 2 and 3, which are acoustic metamaterials, ideally exhibit a transmission loss frequency characteristic where the transmission loss increases as the frequency decreases, with the resonance frequency of the partition as the boundary. However, the measurement results for Comparative Examples 2 and 3 do not fully demonstrate this transmission loss frequency characteristic of the acoustic metamaterial. In contrast, the soundproofing materials of Examples 1 and 2, which are acoustic metamaterials, exhibit the transmission loss frequency characteristic of the acoustic metamaterial more strongly than the soundproofing materials of Comparative Examples 2 and 3.

[0142] These results suggest that in the soundproofing materials of Examples 1 and 2, the membrane portion is positioned at a different location from the connection portion in the extending direction of the support portion. As a result, each membrane portion of multiple metaatoms is independent of the others, making it less susceptible to the vibration of other membrane portions, and thus the transmission loss frequency characteristics of the acoustic metamaterial are more strongly expressed.

[0143] (Example 3) As the soundproofing material for Example 3, the soundproofing material shown in Figures 22 to 25 was fabricated. Figure 22 is a photograph of the soundproofing material of Example 3. Figure 23 is a plan view showing the soundproofing material of Example 3. Figure 24 is a cross-sectional view of section XXIV shown in Figure 23. Figure 25 is a partial cross-sectional view along the line XXV-XXV shown in Figure 23.

[0144] As shown in Figures 22 to 25, a low-density polyethylene (LDPE) sheet with a thickness of 0.80 mm was prepared as the base sheet. The prepared LDPE sheet was heated to 200°C and set in a resin mold at room temperature. The resin mold was then vacuumed, and compressed air was applied to the LDPE sheet from above, thereby vacuum forming a soundproofing material in which 31 metaatoms arranged in a honeycomb pattern were connected by connecting parts. In the vacuum forming process, the support part was made into a rounded cylindrical truncated hexagonal pyramid with an extension length a of 10.0 mm and a taper angle b of 3 degrees. The separation distance c on the connecting part side of adjacent metaatoms was set to 0.6 mm, the separation distance d on the film side of adjacent metaatoms was set to 1.9 mm, and the length e of one side of the film part was set to 6.06 mm. Subsequently, the connecting parts were trimmed by punching with a Thomson die so that the diameter f of the connecting part was 107.5 mm, thereby obtaining the soundproofing material of Example 3.

[0145] The thickness of the connection portion was approximately the same as the thickness of the original sheet (LDPE sheet before vacuum forming). The thickness of the support portion gradually decreased from the connection portion side toward the membrane portion side, and was thinnest at the connection point with the membrane portion. The thickness g of the membrane portion was 0.13 mm.

[0146] (Example 4) In Example 4, a 1.00 mm thick LDPE sheet was prepared as the base sheet. The soundproofing material for Example 4 was obtained under the same conditions as in Example 3. The thickness of the connection portion was approximately the same as the thickness of the original sheet. The support portion gradually decreased in thickness from the connection side toward the membrane side, becoming thinnest at the connection point with the membrane. The thickness g of the membrane was 0.17 mm.

[0147] (Example 5) In Example 5, a 0.50 mm thick polypropylene (PP) sheet was prepared as the base sheet. The soundproofing material for Example 5 was obtained under the same conditions as in Example 3.

[0148] The thickness of the connection portion was approximately the same as the thickness of the original sheet. The thickness of the support portion gradually decreased from the connection portion side toward the membrane portion side, and was thinnest at the connection point with the membrane portion. The thickness g of the membrane portion was 0.08 mm.

[0149] (Example 6) In Example 6, a PP sheet with a thickness of 0.80 mm was prepared as the base sheet. The soundproofing material for Example 6 was obtained under the same conditions as in Example 3.

[0150] The thickness of the connection portion was approximately the same as the thickness of the original sheet. The thickness of the support portion gradually decreased from the connection portion side toward the membrane portion side, and was thinnest at the connection point with the membrane portion. The thickness g of the membrane portion was 0.11 mm.

[0151] (Example 7) In Example 7, a polyethylene terephthalate (PET) sheet with a thickness of 0.70 mm was prepared as the base sheet. The soundproofing material of Example 7 was obtained under the same conditions as in Example 3.

[0152] The thickness of the connection portion was approximately the same as the thickness of the original sheet. The thickness of the support portion gradually decreased from the connection portion side toward the membrane portion side, and was thinnest at the connection point with the membrane portion. The thickness g of the membrane portion was 0.12 mm.

[0153] (Transmission loss measurement) Next, the transmission loss of the soundproofing materials of Examples 3 to 7 was measured. The transmission loss was measured in the same manner as in Example 1. The measurement results for Examples 3 to 7 are shown in Figure 26. Figure 26 is a graph showing the measurement results for Examples 3 to 7.

[0154] As shown in Figure 26, the soundproofing materials of Examples 3 to 7, which are acoustic metamaterials, exhibit a stronger transmission loss frequency characteristic of the acoustic metamaterial compared to the soundproofing materials of Comparative Examples 2 and 3.

[0155] These results suggest that, in the soundproofing materials of Examples 3 to 7, similar to Examples 1 and 2, the membrane portion is positioned at a different location from the connection portion in the extending direction of the support portion. As a result, each membrane portion of multiple metaatoms is independent of the others, making it less susceptible to the vibration of other membrane portions, and thus the transmission loss frequency characteristics of the acoustic metamaterial are more strongly expressed.

[0156] Next, the resonant frequencies of the membrane portion of the soundproofing materials in Examples 3 to 7 were calculated using the above formula (1), and the peak frequency and maximum value of the transmission loss of the soundproofing materials in Examples 3 to 7 were estimated visually from the graph in Figure 26. The results are shown in Table 1 and Figure 27. Figure 27 is a graph showing the relationship between the resonant frequency of the membrane portion and the maximum value of the transmission loss in Examples 3 to 7.

[0157] [Table 1]

[0158] As shown in Table 1 and Figure 27, the transmission loss (sound insulation) increased as the resonant frequency of the membrane increased. From these results, it can be inferred that greater transmission loss (sound insulation) can be obtained by fabricating soundproofing materials so that the resonant frequency of the membrane increases. [Explanation of symbols]

[0159] 1...Soundproofing material, 1A...Soundproofing material, 1B...Soundproofing material, 1C...Soundproofing material, 1D...Soundproofing material, 1E...Soundproofing material, 1F...Soundproofing material, 1G...Soundproofing material, 2...Metaatom, 2A...Metaatom, 2C...Metaatom, 2D...Metaatom, 2E...Metaatom, 2G...Metaatom, 3...Membrane part, 3D...Membrane part, 3E...Membrane part, 4...Support part, 4A...Support part, 4C...Support part, 4D...Support part, 4E...Support part, 4G...Support part, 5...Connection part, 5B...Connection part, 5C...Connection part, 5F...Connection part, 41...First end, 42...Second end, 43...Intermediate part, LD...Extension direction.

Claims

1. A plurality of metaatoms having a membrane portion and a support portion that extends in a tubular shape and supports the membrane portion, The system comprises a connecting portion that connects the support portions of each of the plurality of metaatoms, The film portion has a transmission loss frequency characteristic that has a bandwidth where the transmission loss of the sound wave increases as the frequency of the sound wave decreases, with the resonance frequency of the film portion as the boundary. The membrane portion is positioned at a different location from the connecting portion in the extending direction of the support portion. When one end of the support portion is designated as the first end and the other end of the support portion is designated as the second end, The connecting portion connects the respective support portions of the plurality of meta atoms at the first end. Soundproofing material.

2. The membrane portion is connected to the second end of the support portion, The soundproofing material according to claim 1.

3. When the section between the first end and the second end of the support portion is an intermediate section, The membrane portion is connected to the intermediate portion of the support portion. The soundproofing material according to claim 1.

4. The aforementioned membrane portion does not have holes. The soundproofing material according to claim 1 or 2.

5. The support portion and the connecting portion do not have holes. The soundproofing material according to claim 4.

6. The support portion tapers from the first end side toward the second end side, The soundproofing material according to claim 1 or 2.

7. The resonant frequency of the aforementioned film portion is between 500 Hz and 20,000 Hz. The soundproofing material according to claim 1 or 2.

8. The thickness of the aforementioned film portion is 5 μm or more and 1000 μm or less. The soundproofing material according to claim 1 or 2.

9. The area of ​​the aforementioned membrane is 0.1 cm². ２ 10cm or more ２ The following is: The soundproofing material according to claim 1 or 2.

10. The length of the support portion in the extending direction is 1 mm or more and 80 mm or less. The soundproofing material according to claim 1 or 2.

11. The ratio of the length of the support portion in the extending direction to the area equivalent radius of the membrane portion is 1 or more and 30 or less. The soundproofing material according to claim 1 or 2.

12. The thickness of the support portion is 50 μm or more and 2000 μm or less. The soundproofing material according to claim 1 or 2.

13. The aforementioned connecting portion is formed in a sheet shape. The soundproofing material according to claim 1 or 2.

14. The thickness of the connection portion is 300 μm or more and 2000 μm or less. The soundproofing material according to claim 13.

15. The connecting portion connects the support portions of each of the plurality of metaatoms such that the support portions of adjacent metaatoms among the plurality of metaatoms are in contact with each other. The soundproofing material according to claim 1 or 2.

16. The connecting portion connects the support portions of each of the plurality of metaatoms such that the support portions of adjacent metaatoms are spaced apart from each other. The soundproofing material according to claim 1 or 2.

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