Low-frequency broadband sound-absorbing metamaterial structure based on metal foam and super acoustic barrier

Abstract

The application discloses a kind of low-frequency broadband sound-absorbing metamaterial structures and super-constructed sound barriers based on metal foam, and the metamaterial structure includes metal foam layer and composite resonant cavity layer, and the metal foam layer and the composite resonant cavity layer are stacked;Composite resonant cavity layer includes mother cavity structure and sub-cavity structure, and the sub-cavity structure is embedded in the mother cavity structure, and the mother cavity structure and the sub-cavity structure are all provided with openings towards the metal foam layer, so that the incident sound wave can enter the mother cavity structure and the sub-cavity structure after propagating through the metal foam layer;The cavity of mother cavity structure and sub-cavity structure is unidirectional equal-section cavity.The application is applied to the field of acoustic noise reduction, realizes the high-efficiency sound-absorbing performance of low frequency and wide band, has high stiffness and strength and excellent environmental adaptability, can bear, has good environmental tolerance, has excellent fireproof performance, is suitable for various complex and severe environments, ensures long-term stable working state, is convenient for low-cost mass production, and improves economic feasibility.

Description

Technical Field

[0001] This invention relates to the field of acoustic noise reduction technology, specifically a low-frequency broadband sound-absorbing metamaterial structure based on metal foam and a metastructure sound barrier. Background Technology

[0002] With the acceleration of urbanization and the deepening of industrialization, environmental noise pollution has become increasingly serious, especially low-frequency noise generated in transportation, industry, and construction. Due to its strong penetrating power and long propagation distance, this noise has a significant impact on human quality of life and health. Therefore, developing high-performance sound-absorbing materials and technologies is crucial for effectively controlling this noise.

[0003] Traditional sound-absorbing materials mainly include porous materials such as foam plastics and glass wool. They achieve sound absorption by dissipating sound wave energy through their internal microporous structure, and have good absorption effects for mid-to-high frequency noise above 500Hz. However, these materials have lower absorption efficiency for low-frequency noise below 500Hz. In addition, there are some sound-absorbing structures designed based on the principle of resonance, such as Helmholtz resonators, labyrinth channel sound-absorbing structures, and thin-film resonant sound-absorbing structures. These structures can provide good sound absorption performance for specific frequency ranges by generating a resonance effect at specific frequencies, but their sound absorption bandwidth is narrow, making it difficult to simultaneously meet the needs of wide-band, especially low-frequency, high-efficiency sound absorption.

[0004] In existing sound absorption technologies, although various sound-absorbing materials and structures have been proposed and widely used in different practical scenarios, it is generally difficult to achieve efficient sound absorption performance in the low-frequency range under thin-layer conditions. In recent years, the emergence of metamaterials has provided a new approach to solving this problem. Sound-absorbing metamaterial structures designed based on metamaterial concepts can achieve efficient low-frequency sound absorption under thin-layer conditions, showing great potential in low-frequency noise control. However, existing sound-absorbing metamaterial structures still face challenges in balancing low-frequency broadband efficient sound absorption performance, high load-bearing capacity, and adaptability to complex environments. In particular, the comprehensive requirements for fire resistance, durability, and economy limit the application of existing sound-absorbing metamaterial structures. Existing sound-absorbing metamaterial structures generally have the following shortcomings when facing modern complex acoustic environments: First, the sound absorption performance under strict thickness constraints is still limited, especially for broadband efficient sound absorption of low-frequency noise, which is difficult to achieve and cannot meet the growing demand for low-frequency broadband noise reduction. Second, poor structural load-bearing capacity: Many high-performance sound-absorbing metamaterial structures lack sufficient mechanical strength to withstand external loads. When used as independent structures, they perform poorly under significant wind pressure or other external forces. Third, poor weather resistance and fire resistance: The constituent materials of some sound-absorbing metamaterial structures are susceptible to aging and failure due to environmental factors (such as humidity and temperature changes), and may pose safety hazards in the event of a fire. Fourth, poor economic efficiency: Some high-efficiency sound-absorbing metamaterial structures are too expensive for large-scale engineering applications, and maintenance costs may also be relatively high. Therefore, exploring new solutions to overcome the limitations of existing technologies and achieve more efficient and reliable noise control is of great significance.

[0005] Meanwhile, metal foam, as a lightweight and high-strength novel functional material, boasts advantages such as high load-bearing capacity, good weather resistance, and fire resistance, making it widely applicable in various engineering fields. When applied to the acoustics field, it exhibits unique advantages: due to its unique three-dimensional network structure, it not only provides sufficient surface area for sound wave energy dissipation but also allows for optimization of sound absorption performance at different frequencies by adjusting factors such as pore size and shape. However, relying solely on metal foam itself is insufficient to simultaneously meet the requirements of low-frequency broadband sound absorption. How to effectively combine metal foam with sound-absorbing metamaterial structure technology to form a stable, reliable, and economical overall solution remains a technical challenge that needs to be addressed.

[0006] In summary, for various complex and harsh environments in practical engineering applications, further research and development of novel metamaterial structures that are low-frequency broadband, highly efficient in sound absorption, simple in structure, and mass-producible, with high reliability and high load-bearing capacity, has significant research value and application prospects. Summary of the Invention

[0007] To address the shortcomings of the existing technologies, this invention provides a low-frequency broadband sound-absorbing metamaterial structure and metastructure sound barrier based on metal foam. This structure achieves high-efficiency sound absorption performance at low frequencies and over a wide bandwidth, while also possessing high stiffness and strength, excellent environmental adaptability, load-bearing capacity, good environmental tolerance, and excellent fire resistance. It is suitable for various complex and harsh environments, ensuring long-term stable operation. Furthermore, its relatively simple configuration facilitates low-cost mass production, improving economic feasibility and facilitating large-scale engineering applications.

[0008] To achieve the above objectives, the present invention provides a low-frequency broadband sound-absorbing metamaterial structure, comprising a metal foam layer and a composite resonant acoustic cavity layer, wherein the metal foam layer and the composite resonant acoustic cavity layer are stacked.

[0009] The composite resonant acoustic cavity layer includes a mother cavity structure and a sub-cavity structure. The sub-cavity structure is embedded in the mother cavity structure, and both the mother cavity structure and the sub-cavity structure have openings facing the metal foam layer, so that the incident sound waves can enter the mother cavity structure and the sub-cavity structure after propagating through the metal foam layer.

[0010] Both the mother cavity structure and the daughter cavity structure are unidirectional, uniform cross-section cavities.

[0011] In one embodiment, the composite resonant acoustic cavity layer includes a first base plate, a second base plate, a rectangular surrounding plate, and a side plate;

[0012] The rectangular enclosure is connected to the first base plate and forms the mother cavity structure by enclosing and connecting with the first base plate; the metal foam layer is connected to the top of the rectangular enclosure.

[0013] The number of side plates is two, the two side plates are connected inside the rectangular enclosure, and the second bottom plate is connected to the bottom of the two side plates, and together with the side plates and the rectangular enclosure, they enclose and connect to form the sub-cavity structure;

[0014] The rectangular enclosure and the side panels are provided with connecting substructures, such as flange structures or hanging ear structures, for connecting the metal foam layer.

[0015] In one embodiment, one of the side plates and the rectangular surrounding plate can be integrally formed, that is, the cavity of the mother cavity structure can be an L-shaped cavity.

[0016] In one embodiment, the first base plate, the second base plate, the rectangular enclosure plate, and the side plate are all one or more combinations of homogeneous plates, stiffened plates, ribbed plates, and sandwich panels.

[0017] In one embodiment, at least one rectangular cavity, U-shaped cavity, and / or L-shaped cavity may be connected in parallel or embedded on the composite resonant acoustic cavity layer;

[0018] The parallel or embedded rectangular, U-shaped, and / or L-shaped cavities are all unidirectional, uniform cross-section cavities, and all have openings facing the metal foam layer to improve the degree of freedom in adjusting the sound absorption frequency band and enhance the sound absorption capacity.

[0019] In one embodiment, the metal foam layer is a thin, lightweight, porous material or structure, preferably with a porosity greater than or equal to 60%.

[0020] To achieve the above objectives, the present invention also provides a low-frequency broadband sound-absorbing metamaterial module, comprising two or more of the aforementioned low-frequency broadband sound-absorbing metamaterial structures, wherein each of the aforementioned low-frequency broadband sound-absorbing metamaterial structures is connected in parallel in sequence.

[0021] In one embodiment, any two of the described low-frequency broadband sound-absorbing metamaterial structures may have the same or different structural forms and parameters.

[0022] To achieve the above objectives, the present invention also provides a low-frequency broadband sound-absorbing metamaterial sound barrier, comprising a sound barrier shell structure, the aforementioned low-frequency broadband sound-absorbing metamaterial structure and / or the aforementioned low-frequency broadband sound-absorbing metamaterial module.

[0023] The low-frequency broadband sound-absorbing metamaterial structure and / or the low-frequency broadband sound-absorbing metamaterial module are disposed on the sound barrier shell structure.

[0024] In one embodiment, the sound barrier shell structure includes a frame, a back plate, and a perforated or slotted protective panel;

[0025] The back plate is disposed on the first side of the frame, and the perforated or sewn protective panel is disposed on the second side of the frame, and the perforated or sewn protective panel and the back plate form a cavity.

[0026] The low-frequency broadband sound-absorbing metamaterial structure and / or the low-frequency broadband sound-absorbing metamaterial module are disposed in the cavity, and the metal foam layer on the low-frequency broadband sound-absorbing metamaterial structure and / or the low-frequency broadband sound-absorbing metamaterial module faces the perforated or slotted protective panel.

[0027] In one embodiment, the first base plate of the low-frequency broadband sound-absorbing metamaterial structure and / or the low-frequency broadband sound-absorbing metamaterial module is replaced by the back plate of the sound barrier shell structure, or integrally formed therewith. Meanwhile, the rectangular enclosure of the low-frequency broadband sound-absorbing metamaterial structure and / or the low-frequency broadband sound-absorbing metamaterial module is replaced by the skeleton of the sound barrier shell structure, or integrally formed therewith.

[0028] Compared with the prior art, the present invention has the following beneficial technical effects:

[0029] 1. This invention, based on the excellent acoustic performance and environmental adaptability of metal foam, and combined with metamaterial structure design concepts, constructs a low-frequency broadband sound-absorbing metamaterial structure based on metal foam. Both the sub-cavity structure and the parent cavity structure in the composite resonant acoustic cavity layer include an opening facing the metal foam layer, allowing incident sound waves to enter the parent cavity structure and sub-cavity structure after propagating through the metal foam layer. Due to the significant differences in cavity parameters between the parent cavity and the sub-cavity, particularly the significant difference in equivalent depth, the metal foam layer can be coupled with the parent cavity structure and the sub-cavity structure to form parallel resonant sound absorbers with different resonant frequencies, thereby achieving low-frequency broadband high-efficiency sound absorption. Furthermore, the metal foam layer itself has good mid-to-high frequency sound absorption characteristics; through reasonable parameter design, ultra-wideband high-efficiency sound absorption performance that balances both low-frequency and mid-to-high frequency bands can be achieved.

[0030] 2. The metal foam layer in this invention has high strength and high rigidity. When connected with the sidewall structure of the composite resonant acoustic cavity layer, it together forms a combined structure with high load-bearing capacity. It can still be used as an independent structure when it needs to withstand large wind pressure or other external forces. In addition, since the metal foam layer is made of metal, it has excellent environmental tolerance and fire resistance. It is suitable for various complex and harsh environments such as high pressure, high temperature, humidity, and abrasion. Its sturdy and durable characteristics ensure long-term stable working condition.

[0031] 3. The metal foam layer in this invention is a thin-layer, lightweight, porous material structure. Compared with traditional porous material sound-absorbing structures, the amount of porous material required in this invention is significantly reduced, thereby significantly reducing the structural weight and manufacturing cost, and significantly improving economic efficiency. At the same time, the sub-cavity structure and the mother cavity structure included in the composite resonant acoustic cavity layer of this invention are both unidirectional equal-section cavities with relatively simple configurations, making it easy to mass-produce both the sub-cavity structure and the mother cavity structure at low cost. This paves the way for the large-scale engineering application of low-frequency broadband sound-absorbing metastructure sound barriers based on metal foam. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0033] Figure 1 This is an isometric view of the low-frequency broadband sound-absorbing metamaterial structure in Embodiment 1 of the present invention;

[0034] Figure 2 This is a perspective view of the low-frequency broadband sound-absorbing metamaterial structure in Embodiment 1 of the present invention;

[0035] Figure 3 This is a cross-sectional view of the low-frequency broadband sound-absorbing metamaterial structure in Embodiment 1 of the present invention;

[0036] Figure 4 This is a perspective view of another embodiment of the low-frequency broadband sound-absorbing metamaterial structure in Embodiment 1 of the present invention;

[0037] Figure 5 This is a schematic diagram of the parallel expansion of the low-frequency broadband sound-absorbing metamaterial structure in Embodiment 1 of the present invention, wherein: (a) and (b) are schematic diagrams of the parallel expansion of the U-shaped cavity, (c) is a schematic diagram of the parallel expansion of the rectangular cavity, and (d) is a schematic diagram of the parallel expansion of the L-shaped cavity.

[0038] Figure 6 The diagram below shows the preparation material of the composite resonant acoustic cavity layer in Embodiment 1 of the present invention, wherein: (a) is a schematic diagram of a homogeneous plate, (b) is a schematic diagram of a stiffened plate, (c) is a schematic diagram of a foam sandwich panel, and (d) is a schematic diagram of a honeycomb sandwich panel;

[0039] Figure 7 The low-frequency broadband sound-absorbing metamaterial structure in Embodiment 1 of the present invention... Figure 1 Sound absorption curves under the configuration;

[0040] Figure 8 This is an isometric view of the sound-absorbing metamaterial structure module in Embodiment 2 of the present invention under one implementation method;

[0041] Figure 9 This is an isometric view of the sound-absorbing metamaterial structure module in Embodiment 2 of the present invention under another implementation method;

[0042] Figure 10 This is an isometric view of the sound-absorbing metastructure sound barrier in Embodiment 3 of the present invention under one implementation method;

[0043] Figure 11 This is a cross-sectional projection view of a low-frequency broadband sound-absorbing metamaterial structure with reinforced wall panels in Embodiment 4 of the present invention;

[0044] Figure 12 The diagram shows two assembly schematics of the metal foam layer and the composite resonant acoustic cavity layer of the low-frequency broadband sound-absorbing metamaterial structure in Embodiment 1 of the present invention, wherein (a) is a schematic diagram of the flange structure and (b) is a schematic diagram of the ear-hanging structure.

[0045] Reference numerals: 1. Metal foam layer; 2. Composite resonant acoustic cavity layer; 201. Mother cavity structure; 202. Sub-cavity structure; 203. First base plate; 204. Second base plate; 205. Rectangular enclosure plate; 206. Side plate; 3. Sound barrier shell structure.

[0046] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0047] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0048] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0049] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0050] In this invention, unless otherwise explicitly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection, an electrical connection, a physical connection, or a wireless communication connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two elements or the interaction between two elements, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0051] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0052] Example 1

[0053] like Figure 1 The present embodiment discloses a low-frequency broadband sound-absorbing metamaterial structure based on metal foam, which mainly includes a metal foam layer 1 and a composite resonant acoustic cavity layer 2. The metal foam layer 1 and the composite resonant acoustic cavity layer 2 are stacked, that is, the metal foam layer 1 is connected in series on the composite resonant acoustic cavity layer 2.

[0054] Specifically, the composite resonant acoustic cavity layer 2 includes a mother cavity structure 201 and a sub-cavity structure 202. The sub-cavity structure 202 is partially or entirely embedded in the mother cavity structure 201. Both the mother cavity structure 201 and the sub-cavity structure 202 have openings facing the metal foam layer 1, so that the incident sound waves can enter the mother cavity structure 201 and the sub-cavity structure 202 after passing through the metal foam layer 1. Since the cavity parameters of the mother cavity structure 201 and the sub-cavity structure 202 are significantly different, especially the equivalent depth, the metal foam layer 1 can be coupled with the mother cavity structure 201 and the sub-cavity structure 202 to form two parallel resonant sound absorbers with different resonant frequencies, thereby achieving low-frequency broadband and efficient sound absorption. The connection between the two openings of the mother cavity structure 201 and the sub-cavity structure 202 increases the propagation distance of the sound waves in the cavity, increases the acoustic impedance, helps dissipate sound energy, and further improves the low-frequency sound absorption performance of the sound-absorbing metamaterial structure module. Meanwhile, the metal foam layer 1 itself has good mid-to-high frequency sound absorption characteristics, which can dissipate mid-to-high frequency sound waves significantly. Through reasonable parameter design, the sound-absorbing metamaterial structure can achieve ultra-wideband and high-efficiency sound absorption performance that takes into account both low-frequency and mid-to-high frequency bands.

[0055] In the specific implementation process, the composite resonant acoustic cavity layer 2 includes a first base plate 203, a second base plate 204, a rectangular surrounding plate 205, and side plates 206. The bottom end of the rectangular surrounding plate 205 is fixedly connected to the first base plate 203 by means of adhesive bonding, snap-fit ​​connection, screw connection, or integral molding, thereby enclosing and connecting to form the mother cavity structure 201. The sidewall of the metal foam layer 1 is fixedly connected to the inner wall of the top of the rectangular surrounding plate 205 by means of adhesive bonding, snap-fit ​​connection, screw connection, or integral molding. There are two side plates 206, which are symmetrically connected at intervals within the rectangular surrounding plate 205. The second base plate 204 is connected to the bottom of the two side plates 206, and the top of the two side plates 206 is connected to the bottom of the metal foam layer 1. That is, the second base plate 204, side plates 206, and part of the rectangular surrounding plate 205 enclose and connect to form a sub-cavity structure 202, and the cavities of the sub-cavity structure 202 and the mother cavity structure 201 are kept separate. For example Figure 3 As shown, the high-strength, high-rigidity metal foam layer 1, when connected to the rectangular surrounding plate 205 and side plate 206 on the composite resonant acoustic cavity layer 2, together form a composite structure with high load-bearing capacity, which can maintain its normal structural shape even under certain external forces. Furthermore, because the metal foam layer 1 is made of metal, it has excellent environmental resistance and fire resistance, ensuring the long-term stable operation of the sound-absorbing metamaterial structure in various complex and harsh environments.

[0056] It is worth noting that the shape of the side panel 206 is not limited to specific applications. Figure 3The flat plate shown can also be a curved plate, an arc plate, etc., that is, the cross-sectional shape of the inner cavity of the sub-cavity structure 202 is not limited to... Figure 3 The rectangle shown can also be a trapezoidal cross-section or other irregular structures. Furthermore, the sub-cavity structure 202 is not limited to... Figure 3 The cavity shown is located in the middle of the mother cavity structure 201, but it can also be located on one side of the mother cavity structure 201, meaning that the cross-sectional shape of the cavity inside the mother cavity structure 201 is not limited to... Figure 3 The U-shaped cavity shown can also be an L-shaped cavity. In this case, the side plate 206 closer to the mother cavity structure 201 and the rectangular surrounding plate 205 can be integrally formed, that is, the side plate 206 is replaced by the corresponding part of the rectangular surrounding plate 205, for example... Figure 4 As shown.

[0057] In this embodiment, both the mother cavity structure 201 and the daughter cavity structure 202 are unidirectional, uniform cross-section cavities. Depending on the limitations of the actual installation space or the needs of modular design, the length, width, and height of the daughter cavity structure 202 and the mother cavity structure 201 can be designed to any size. Furthermore, both the daughter cavity structure 202 and the mother cavity structure 201 can be manufactured using low-cost, reliable integrated molding processes such as extrusion molding and sheet metal bending, achieving low-cost, high-volume, and rapid high-efficiency manufacturing. In addition, the metal foam layer 1 is a thin-layer, lightweight, porous material structure, which is not only easy to process but also requires a small amount of porous material, significantly reducing structural weight and manufacturing costs, thus significantly improving economic efficiency.

[0058] In a preferred embodiment, at least one rectangular cavity, U-shaped cavity, and / or L-shaped cavity are also connected in parallel or embedded on the composite resonant acoustic cavity layer 2. These parallel or embedded rectangular cavities, U-shaped cavities, and / or L-shaped cavities are all unidirectional, uniform cross-section cavities, and each has an opening facing the metal foam layer 1. For example... Figure 5 (a) Figure 5 As shown in (b), a U-shaped cavity is connected in parallel in the composite resonant acoustic cavity layer 2, and its implementation is the same as that of the sub-cavity structure 202; for example Figure 5 As shown in (c), a rectangular cavity is connected in parallel to the composite resonant acoustic cavity layer 2, which is achieved by extending the rectangular surrounding plate 205 and the first base plate 203; for example... Figure 5As shown in (d), an L-shaped cavity is connected in parallel in the composite resonant acoustic cavity layer 2, which is achieved by connecting a partition plate with rectangular surrounding plates 205 on both sides between the first base plate 203 and the second base plate 204. By connecting or embedding rectangular cavities, U-shaped cavities and / or L-shaped cavities in parallel in the composite resonant acoustic cavity layer 2, multiple coupled resonant acoustic cavities are formed, with multiple parallel resonant sound absorbers with different resonant frequencies. This can improve the degree of freedom in adjusting the sound absorption frequency band of the low-frequency broadband sound-absorbing metamaterial structure module based on metal foam. Furthermore, by embedding one or more rectangular cavities in the composite resonant acoustic cavity layer 2 (same as the embodiment of sub-cavity structure 202), the ability to control the sound absorption performance of the low-frequency broadband sound-absorbing metamaterial structure module based on metal foam can be further improved.

[0059] In this embodiment, the metal foam layer 1 is a thin-layer, lightweight, porous material structure with a porosity greater than or equal to 60%, and can be made of one or more of aluminum foam, copper foam, nickel foam, and their foam alloys. The first base plate 203, the second base plate 204, the rectangular surrounding plate 205, and the side plate 206 are all combinations of one or more of homogeneous plates, stiffened plates, ribbed plates, and sandwich panels, for example... Figure 6 (a) The homogeneous plate shown Figure 6 (b) The stiffening plate shown Figure 6 (c) The foam sandwich panel shown in the image Figure 6 (d) shows the honeycomb sandwich panel, etc. In this embodiment, the rectangular surrounding panel 205 and the side panel 206 are both made of homogeneous plate, and the first bottom plate 203 and the second bottom plate 204 are both made of stiffened plate.

[0060] refer to Figure 7 for Figure 1 The sound absorption coefficient curve of the mid-to-low frequency broadband sound-absorbing metamaterial structure is shown. Specific parameters are: the thickness of the metal foam layer 1 is 5mm, and the length, width, and height of the composite resonant acoustic cavity layer 2 are 100mm, 100mm, and 100mm, respectively. Figure 7 It can be seen that the sound absorption coefficient of this low-frequency broadband sound-absorbing metamaterial structure is above 0.85 in the low-frequency broadband range of 400~2500Hz, and the average sound absorption coefficient is greater than 0.9.

[0061] Example 2

[0062] This embodiment discloses a low-frequency broadband sound-absorbing metamaterial module based on metal foam, comprising two or more low-frequency broadband sound-absorbing metamaterial structures as described in Embodiment 1, wherein the low-frequency broadband sound-absorbing metamaterial structures are connected in parallel sequentially, for example... Figure 8 , Figure 9 As shown, multiple low-frequency broadband sound-absorbing metamaterial structures can be connected in parallel to form one or more columns.

[0063] In this embodiment, the low-frequency broadband sound-absorbing metamaterial module consists of four different sound-absorbing metamaterial structure modules. The length and depth of the sub-cavity structure 202 of each low-frequency broadband sound-absorbing metamaterial structure are partially or completely different, forming a mother cavity structure 201 and a sub-cavity structure 202 with different shapes and sizes. Through coupling, the sound absorption frequency band can be further broadened, thereby obtaining better sound absorption performance.

[0064] In the specific implementation process, the thickness of the metal foam layer 1, the number of sub-cavity structures 202, the relative position of the sub-cavity structure 202 in the parent cavity structure 201, and the structural parameters of the sub-cavity structure 202 can all be set to be partially or completely different for each low-frequency broadband sound-absorbing metamaterial structure.

[0065] Example 3

[0066] This embodiment discloses a low-frequency broadband sound-absorbing metastructure sound barrier based on metal foam, such as Figure 10 As shown, it includes a sound barrier shell structure 3, and a low-frequency broadband sound-absorbing metamaterial structure in Embodiment 1 and / or a low-frequency broadband sound-absorbing metamaterial structure module in Embodiment 2, wherein the low-frequency broadband sound-absorbing metamaterial structure and / or the low-frequency broadband sound-absorbing metamaterial module are disposed on the sound barrier shell structure 3.

[0067] Specifically, the sound barrier shell structure 3 includes a frame, a back plate, and a perforated or slotted protective panel. The back plate is located on a first side of the frame, and the perforated or slotted protective panel is located on a second side of the frame, forming a cavity between the perforated or slotted protective panel and the back plate. A low-frequency broadband sound-absorbing metamaterial structure and / or a low-frequency broadband sound-absorbing metamaterial module is located within the cavity, with the metal foam layer 1 on the low-frequency broadband sound-absorbing metamaterial structure and / or the low-frequency broadband sound-absorbing metamaterial module facing the perforated or slotted protective panel.

[0068] In the specific implementation process, the first base plate 203 on the low-frequency broadband sound-absorbing metamaterial structure and / or the low-frequency broadband sound-absorbing metamaterial module can be replaced by the back plate of the sound barrier shell structure 3, or the first base plate 203 and the back plate can be integrally formed to simplify the structure of the low-frequency broadband sound-absorbing metamaterial sound barrier and reduce costs.

[0069] Meanwhile, the rectangular enclosure 205 of the low-frequency broadband sound-absorbing metamaterial structure and / or the low-frequency broadband sound-absorbing metamaterial module can be replaced by the skeleton of the sound barrier shell structure, or integrally formed with it.

[0070] Example 4

[0071] This embodiment discloses another form of low-frequency broadband sound-absorbing metamaterial structure based on metal foam, such as Figure 11As shown, based on the low-frequency broadband sound-absorbing metamaterial structure in Example 1, the addition of multiple sub-cavities in parallel improves the degree of freedom of structural parameter adjustment, which is beneficial to adjusting the sound absorption performance of the structure; at the same time, the addition of stiffeners to the base plate further enhances the stiffness and strength of the structure, which is beneficial to improving the sound insulation performance of the structure.

[0072] In practical implementation, the metal foam layer and composite resonant acoustic cavity layer of the sound-absorbing metamaterial structure can be connected in various ways, such as... Figure 12 The diagram illustrates two connection methods for the metal foam layer and the composite resonant acoustic cavity layer in the low-frequency broadband sound-absorbing metamaterial structure of Embodiment 1 of the present invention. By opening holes in the metal foam layer and setting connecting substructures, such as flange structures or hanging ear structures, on the rectangular surrounding plate and side plate, the metal foam layer and the composite resonant acoustic cavity layer can be combined into a whole sound-absorbing metamaterial structure using rivets or screws.

[0073] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A low-frequency broadband sound-absorbing metamaterial structure, characterized in that, It includes a metal foam layer and a composite resonant acoustic cavity layer, wherein the metal foam layer and the composite resonant acoustic cavity layer are stacked together, and the porosity of the metal foam layer is greater than or equal to 60%; The composite resonant acoustic cavity layer includes a mother cavity structure and a sub-cavity structure. The sub-cavity structure is embedded in the mother cavity structure, and both the mother cavity structure and the sub-cavity structure have openings facing the metal foam layer, so that the incident sound waves can enter the mother cavity structure and the sub-cavity structure after propagating through the metal foam layer. Both the mother cavity structure and the daughter cavity structure are unidirectional, uniform cross-section cavities. The composite resonant acoustic cavity layer includes a first base plate, a second base plate, a rectangular surrounding plate, and side plates; The rectangular enclosure is connected to the first base plate and forms the mother cavity structure by enclosing and connecting with the first base plate; the metal foam layer is connected to the top of the rectangular enclosure. The number of side plates is two, the two side plates are connected inside the rectangular enclosure, and the second bottom plate is connected to the bottom of the two side plates, and together with the side plates and the rectangular enclosure, they enclose and connect to form the sub-cavity structure; The rectangular enclosure and the side panels are further provided with connecting substructures for connecting the metal foam layer; The metal foam layer is used to dissipate mid-to-high frequency sound waves, and is coupled with the mother cavity structure and the daughter cavity structure to form parallel resonant sound absorbers with different resonant frequencies.

2. The low-frequency broadband sound-absorbing metamaterial structure according to claim 1, characterized in that, One of the side plates and the rectangular surrounding plate can be integrally formed, that is, the cavity of the mother cavity structure can be an L-shaped cavity.

3. The low-frequency broadband sound-absorbing metamaterial structure according to claim 1, characterized in that, The first base plate, the second base plate, the rectangular surrounding plate, and the side plate are all one or a combination of two or more of the following: homogeneous plate, stiffened plate, ribbed plate, and sandwich panel.

4. The low-frequency broadband sound-absorbing metamaterial structure according to any one of claims 1 to 3, characterized in that, The composite resonant acoustic cavity layer also has at least one rectangular cavity, U-shaped cavity and / or L-shaped cavity connected in parallel or embedded therein; The parallel or embedded rectangular, U-shaped, and / or L-shaped cavities are all unidirectional, uniform cross-section cavities, and all have openings facing the metal foam layer to improve the degree of freedom in adjusting the sound absorption frequency band and enhance the sound absorption capacity.

5. The low-frequency broadband sound-absorbing metamaterial structure according to any one of claims 1 to 3, characterized in that, The metal foam layer is a thin, lightweight, porous material or structure.

6. A low-frequency broadband sound-absorbing metamaterial module, characterized in that, It includes two or more low-frequency broadband sound-absorbing metamaterial structures as described in any one of claims 1 to 5, wherein each of the low-frequency broadband sound-absorbing metamaterial structures is connected in parallel in sequence.

7. The low-frequency broadband sound-absorbing metamaterial module according to claim 6, characterized in that, The structural forms and parameters of any two of the described low-frequency broadband sound-absorbing metamaterial structures may be the same or different.

8. A low-frequency broadband sound-absorbing metastructure sound barrier, characterized in that, Including a sound barrier shell structure, a low-frequency broadband sound-absorbing metamaterial structure as described in any one of claims 1 to 5, or a low-frequency broadband sound-absorbing metamaterial module as described in claim 6 or 7; The low-frequency broadband sound-absorbing metamaterial structure or the low-frequency broadband sound-absorbing metamaterial module is disposed on the sound barrier shell structure.

9. The low-frequency broadband sound-absorbing metamorphic sound barrier according to claim 8, characterized in that, The sound barrier shell structure includes a frame, a back plate, and a perforated or slotted protective panel. The back plate is disposed on the first side of the frame, and the perforated or sewn protective panel is disposed on the second side of the frame, and the perforated or sewn protective panel and the back plate form a cavity. The low-frequency broadband sound-absorbing metamaterial structure or the low-frequency broadband sound-absorbing metamaterial module is disposed in the cavity, and the metal foam layer on the low-frequency broadband sound-absorbing metamaterial structure or the low-frequency broadband sound-absorbing metamaterial module faces the perforated or slotted protective panel. The first base plate of the low-frequency broadband sound-absorbing metamaterial structure or the low-frequency broadband sound-absorbing metamaterial module can be replaced by the back plate of the sound barrier shell structure, or integrally formed therewith. Meanwhile, the rectangular enclosure of the low-frequency broadband sound-absorbing metamaterial structure or the low-frequency broadband sound-absorbing metamaterial module can be replaced by the skeleton of the sound barrier shell structure, or integrally formed therewith.

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