Low-frequency broadband sound absorption metamaterial structure based on metal foam and metamaterial sound barrier

Abstract

The invention discloses a low-frequency broadband sound absorption metamaterial structure based on metal foam and a metamaterial sound barrier, the metamaterial structure comprises a metal foam layer and a composite resonant sound cavity layer, and the metal foam layer and the composite resonant sound cavity layer are stacked; the composite resonance sound cavity layer comprises a mother cavity structure and a son cavity structure, the son cavity structure is embedded in the mother cavity structure, and the mother cavity structure and the son cavity structure are both provided with openings facing the metal foam layer, so that incident sound waves can enter the mother cavity structure and the son cavity structure after propagating through the metal foam layer; cavities of the primary cavity structure and the secondary cavity structure are one-way uniform-section cavities. The low-frequency and broadband high-efficiency sound absorption composite material is applied to the field of acoustic noise reduction, achieves low-frequency and broadband high-efficiency sound absorption performance, has high rigidity and strength and excellent environmental adaptability, can bear loads, is good in environmental tolerance and excellent in fireproof performance, is suitable for various complex and severe environments, ensures a long-term stable working state, is convenient to manufacture in batches at low cost, and has wide application prospects. And the economic feasibility is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of acoustic noise reduction, and in particular to a low-frequency, broadband sound-absorbing metamaterial structure and a metastructure sound barrier based on metal foam. Background Art

[0002] With the acceleration of urbanization and the deepening of industrialization, environmental noise pollution is becoming increasingly serious, especially the low-frequency noise generated in the fields of transportation, industry and construction. Due to its strong penetration and long propagation distance, it has a significant impact on the quality of human life and health. In order to effectively control these noises, it is particularly important to develop high-performance sound-absorbing materials and technologies.

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

[0004] In the existing sound absorption technology, although a variety of 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 idea for solving this problem. The sound absorbing metamaterial structure designed based on the metamaterial concept can achieve low-frequency and efficient sound absorption under thin layer conditions, showing great potential in low-frequency noise control. However, the existing sound absorbing metamaterial structure still faces challenges in taking into account low-frequency broadband efficient sound absorption performance, high load-bearing performance and adaptability to complex environments. In particular, the comprehensive requirements in terms of fire resistance, durability and economy have limited the application of existing sound absorbing metamaterial structures. When facing modern complex acoustic environments, the existing sound absorbing metamaterial structures generally have the following deficiencies: First, the sound absorption performance under strict thickness constraints is still limited, especially for broadband efficient sound absorption of low-frequency noise is difficult to achieve, and cannot meet the growing demand for low-frequency broadband noise reduction. Second, the structural bearing capacity is poor. Many high-performance sound-absorbing metamaterial structures lack sufficient mechanical strength to withstand external loads. When used as independent structures, they perform poorly under high wind pressure or other external forces. Third, the weather resistance and fire resistance are poor. The constituent materials of some sound-absorbing metamaterial structures are easily affected by environmental factors (such as humidity and temperature changes) and age and fail, and there may be safety hazards in the event of a fire. Fourth, the economic efficiency is poor. Some high-efficiency sound-absorbing metamaterial structures are expensive and not suitable for large-scale engineering applications. At the same time, the maintenance costs may also be relatively high. Therefore, it is of great significance to explore new solutions to overcome the limitations of existing technologies and achieve more efficient and reliable noise control.

[0005] At the same time, as a new type of lightweight and high-strength functional material, metal foam has the advantages of high load-bearing capacity, good weather resistance and fire resistance, and has broad application prospects in multiple engineering fields. When applied to the field of acoustics, it shows unique advantages: due to its unique three-dimensional network structure characteristics, it can not only provide sufficient surface area for the dissipation of sound wave energy, but also optimize the sound absorption performance at different frequencies by adjusting factors such as pore size and shape. However, it is difficult to simultaneously meet the requirements of low-frequency broadband sound absorption by relying solely on metal foam itself. How to effectively combine metal foam with sound-absorbing metamaterial structure technology to form a stable, reliable and economical overall solution is a technical problem that needs to be solved.

[0006] In summary, for various complex and harsh environments in actual engineering applications, further research and development of new metamaterial structures with high reliability and high load-bearing capacity that can achieve low-frequency, broadband, efficient sound absorption, simple structure and mass production has important research value and application prospects. Summary of the invention

[0007] In view of the deficiencies in the above-mentioned prior art, the present invention provides a low-frequency broadband sound-absorbing metamaterial structure and a metastructure sound barrier based on metal foam, which achieves low-frequency and broadband high-efficiency sound absorption performance, and has both high rigidity and strength and excellent environmental adaptability, can bear loads, has good environmental tolerance, and has excellent fire resistance, and is suitable for various complex and harsh environments, ensuring long-term stable working conditions. In addition, the relatively simple configuration facilitates low-cost batch manufacturing, improves economic feasibility, and is conducive to large-scale engineering applications.

[0008] To achieve the above object, 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; The composite resonant acoustic cavity layer comprises a mother cavity structure and a sub-cavity structure, wherein 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 wave can enter the mother cavity structure and the sub-cavity structure after propagating through the metal foam layer; The cavities of the mother cavity structure and the sub-cavity structure are both unidirectional cavities with equal cross-sections.

[0009] In one embodiment, the composite resonant acoustic cavity layer includes a first bottom plate, a second bottom plate, a rectangular surrounding plate and a side plate; The rectangular enclosure is connected to the first bottom plate and is enclosed and connected with the first bottom plate to form the mother cavity structure, and the metal foam layer is connected to the top of the rectangular enclosure; There are two side panels, the two side panels are connected inside the rectangular enclosure, and the second bottom panel is connected to the bottom of the two side panels, and cooperates with the side panels and the rectangular enclosure to enclose and connect to form the sub-cavity structure; The rectangular enclosure and the side panels are provided with connecting substructures, such as flange structures or ear structures, etc., for connecting the metal foam layer.

[0010] In one of the embodiments, one of the side panels and the rectangular enclosure panel can be integrally formed, that is, the cavity of the mother cavity structure can be an L-shaped cavity.

[0011] In one embodiment, the first bottom plate, the second bottom plate, the rectangular enclosure plate, and the side plates are all selected from the group consisting of homogeneous plates, stiffened plates, ribbed plates, and sandwich plates, or a combination of two or more thereof.

[0012] In one embodiment, at least one rectangular cavity, U-shaped cavity and / or L-shaped cavity may be connected in parallel or embedded in the composite resonant acoustic cavity layer; The parallel or embedded rectangular cavities, U-shaped cavities and / or L-shaped cavities are all unidirectional equal-section cavities and have openings facing the metal foam layer to increase the adjustment freedom of the sound absorption frequency band and improve the sound absorption capacity.

[0013] In one embodiment, the metal foam layer is a thin layer of lightweight porous material or structure, and preferably has a porosity greater than or equal to 60%.

[0014] To achieve the above object, the present invention also provides a low-frequency broadband sound absorbing metamaterial module, comprising two or more of the above low-frequency broadband sound absorbing metamaterial structures, each of which is connected in parallel in sequence.

[0015] In one embodiment, the structural forms and parameters of any two of the low-frequency broadband sound-absorbing metamaterial structures are the same or different.

[0016] To achieve the above object, the present invention also provides a low-frequency broadband sound absorbing metamaterial sound barrier, comprising a sound barrier shell structure, the above-mentioned low-frequency broadband sound absorbing metamaterial structure and / or the above-mentioned low-frequency broadband sound absorbing metamaterial module; The low-frequency broadband sound absorbing metamaterial structure and / or the low-frequency broadband sound absorbing metamaterial module are arranged on the sound barrier shell structure.

[0017] In one embodiment, the sound barrier shell structure includes a frame, a back plate, and a perforated or slotted protective plate; The back plate is arranged on the first side of the frame, the perforated or seamed protective plate is arranged on the second side of the frame, and a cavity is enclosed between the perforated or seamed protective plate and the back plate; The low-frequency broadband sound absorbing metamaterial structure and / or the low-frequency broadband sound absorbing metamaterial module are arranged 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.

[0018] In one embodiment, the first bottom 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 is formed integrally therewith, and at the same time, 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 is formed integrally therewith.

[0019] Compared with the prior art, the present invention has the following beneficial technical effects: 1. The present invention, based on metal foam with excellent acoustic properties and good environmental adaptability, combines the design concept of metamaterial structure to construct a low-frequency, broadband sound-absorbing metamaterial structure based on metal foam. The sub-cavity structure and the mother cavity structure in the composite resonant acoustic cavity layer both include an opening facing 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. Since the cavity parameters of the mother cavity and the sub-cavity are significantly different, especially the equivalent depth is significantly different, the metal foam layer can be coupled with the mother cavity structure and the sub-cavity structure to form parallel resonant sound absorbers with different resonant frequencies, thereby achieving low-frequency, broadband and efficient sound absorption; in addition, the metal foam layer itself has good mid- and high-frequency sound absorption characteristics. Through reasonable parameter design, ultra-wideband efficient sound absorption performance that takes into account both low-frequency and mid- and high-frequency bands can be achieved; 2. The metal foam layer in the present invention has high strength and high rigidity characteristics. After being connected with the side wall structure of the composite resonant acoustic cavity layer, it 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 very good environmental tolerance and excellent fire resistance. It is suitable for various complex and harsh environments such as high pressure, high temperature, humidity, and wear. Its strong and durable characteristics ensure long-term stable working conditions. 3. The metal foam layer in the present invention is a thin layer of lightweight porous material structure. Compared with the traditional porous material sound-absorbing structure, the amount of porous material required in the present invention is greatly reduced, thereby significantly reducing the structural weight, greatly reducing the construction cost, and significantly improving the economy; at the same time, the sub-cavity structure and the mother cavity structure contained in the composite resonant sound cavity layer in the present invention are both unidirectional equal-section cavities with a relatively simple configuration, which makes the sub-cavity structure and the mother cavity structure easy to manufacture in batches at low cost, paving the way for large-scale engineering applications of low-frequency, broadband sound-absorbing super-structure sound barriers based on metal foam. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0021] Figure 1 This is an axonometric diagram of the low-frequency broadband sound-absorbing metamaterial structure in Example 1 of the present invention; Figure 2 A perspective view of the low-frequency broadband sound-absorbing metamaterial structure in Example 1 of the present invention; Figure 3 This is a cross-sectional view of the low-frequency broadband sound-absorbing metamaterial structure in Example 1 of the present invention; Figure 4 A perspective view of another implementation of the low-frequency broadband sound-absorbing metamaterial structure in Example 1 of the present invention; Figure 5 Schematic diagram of parallel expansion of the low-frequency broadband sound-absorbing metamaterial structure in Example 1 of the present invention, wherein: (a) and (b) are schematic diagrams of parallel expansion of U-shaped cavities, (c) is a schematic diagram of parallel expansion of rectangular cavities, and (d) is a schematic diagram of parallel expansion of L-shaped cavities; Figure 6 Schematic diagrams of the preparation of the composite resonant acoustic cavity layer in Example 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 plate, and (d) is a schematic diagram of a honeycomb sandwich plate; Figure 7 The low-frequency broadband sound absorbing metamaterial structure in Example 1 of the present invention is Figure 1 Sound absorption curve under the configuration; Figure 8 It is an axonometric diagram of the sound-absorbing metamaterial structure module in Example 2 of the present invention in one implementation manner; Fig. 9 is an axonometric diagram of the sound-absorbing metamaterial structure module in Example 2 of the present invention in another implementation manner; Fig.10 This is an axonometric diagram of a sound-absorbing superstructure sound barrier in Example 3 of the present invention in one implementation manner; Fig.11 It is a cross-sectional projection diagram of a low-frequency, broadband sound-absorbing metamaterial structure with a stiffened wall panel in Example 4 of the present invention; Fig.12 These are two assembly schematic diagrams of the metal foam layer and the composite resonant acoustic cavity layer of the low-frequency broadband sound-absorbing metamaterial structure in Example 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.

[0022] Figure numbers: metal foam layer 1, composite resonant acoustic cavity layer 2, mother cavity structure 201, sub-cavity structure 202, first bottom plate 203, second bottom plate 204, rectangular enclosure 205, side plate 206, sound barrier shell structure 3.

[0023] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] 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 position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0026] In addition, in the present invention, descriptions such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0027] In the present invention, unless otherwise clearly specified and limited, the terms "connection", "fixation", etc. should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, a physical connection, or a wireless communication connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0028] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0029] Example 1 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 to the composite resonant acoustic cavity layer 2.

[0030] Specifically, the composite resonant acoustic cavity layer 2 includes a mother cavity structure 201 and a sub-cavity structure 202, wherein part or all of the sub-cavity structure 202 is embedded in the mother cavity structure 201, and 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 wave can enter the mother cavity structure 201 and the sub-cavity structure 202 after propagating 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 is significantly different, 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 realizing low-frequency, broadband and efficient sound absorption. The two openings of the mother cavity structure 201 and the sub-cavity structure 202 are connected, which increases the propagation distance of the sound wave in the cavity, increases the acoustic resistance, and contributes to the dissipation of acoustic energy, further improving the low-frequency sound absorption performance of the sound-absorbing metamaterial structure module. At the same time, the metal foam layer 1 itself has good mid- and high-frequency sound absorption characteristics and can greatly dissipate mid- and high-frequency sound waves. Through reasonable parameter design, the sound-absorbing metamaterial structure can achieve ultra-wideband efficient sound absorption performance that takes into account both low-frequency and mid- and high-frequency bands.

[0031] In the specific implementation process, the composite resonant acoustic cavity layer 2 includes a first bottom plate 203, a second bottom plate 204, a rectangular enclosure 205 and a side plate 206. The bottom end of the rectangular enclosure 205 is fixedly connected to the first bottom plate 203 by means of gluing, snap connection, screw connection, integral molding, etc., and then enclosed and connected to form a mother cavity structure 201. The side wall of the metal foam layer 1 is fixedly connected to the inner wall at the top of the rectangular enclosure 205 by means of gluing, snap connection, screw connection, integral molding, etc. There are two side plates 206, and the two side plates 206 are symmetrically connected in the rectangular enclosure 205 at intervals, and the second bottom 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 bottom plate 204, the side plate 206 and part of the rectangular enclosure 205 are enclosed and connected to form a sub-cavity structure 202, and the cavity of the sub-cavity structure 202 and the mother cavity structure 201 are kept disconnected. For example Figure 3 As shown. The metal foam layer 1 with high strength and high rigidity is connected with the rectangular enclosure 205 and the side plate 206 on the composite resonant acoustic cavity layer 2 to form a combined structure with high load-bearing capacity, which can still maintain a normal structural form under a certain external force. In addition, the metal foam layer 1 is made of metal and has very good environmental tolerance and fire resistance, so that the sound-absorbing metamaterial structure can ensure long-term stable working conditions in various complex and harsh environments.

[0032] It is worth noting that in the specific application process, the shape of the side plate 206 is not limited to Figure 3 The flat plate shown in the figure may 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 rectangular shape shown may also be a trapezoidal cross section or other special-shaped structures. Figure 3 The mother cavity structure 201 is shown as being located in the middle of the mother cavity structure 201, and may also be located on one side of the mother cavity structure 201, that is, the cross-sectional shape of the cavity in 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 side of the mother cavity structure 201 can be set as an integral molding with the rectangular enclosure 205, that is, the side plate 206 is replaced by the corresponding part of the rectangular enclosure 205, for example Figure 4 shown.

[0033] In this embodiment, the cavities of the mother cavity structure 201 and the sub-cavity structure 202 are all unidirectional equal-section cavities. According to the actual installation space limitation or the need of modular design, the length, width and height of the sub-cavity structure 202 and the mother cavity structure 201 can be designed to any size, and the sub-cavity structure 202 and the mother cavity structure 201 can both adopt low-cost and reliable integrated molding processes such as extrusion molding and sheet metal bending to achieve low-cost, large-scale, fast and efficient manufacturing. In addition, the metal foam layer 1 is a thin layer of lightweight porous material structure, which is not only easy to process, but also requires less porous material, which can significantly reduce the weight of the structure, greatly reduce the cost, and significantly improve the economy.

[0034] As a preferred embodiment, at least one rectangular cavity, U-shaped cavity and / or L-shaped cavity is also connected in parallel or embedded in the composite resonant acoustic cavity layer 2, and the parallel or embedded rectangular cavity, U-shaped cavity and / or L-shaped cavity are also unidirectional equal-section cavities and have openings facing the metal foam layer 1. Figure 5 (a) Figure 5 As shown in (b), a U-shaped cavity is connected in parallel to 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 realized by extending the rectangular enclosure 205 and the first bottom plate 203; for example Figure 5 As shown in (d), an L-shaped cavity is connected in parallel to the composite resonant acoustic cavity layer 2, which is realized by connecting a partition plate connected to the rectangular enclosure 205 on both sides between the first bottom plate 203 and the second bottom plate 204. By connecting or embedding rectangular cavities, U-shaped cavities and / or L-shaped cavities in parallel to the composite resonant acoustic cavity layer 2, a multi-coupled resonant acoustic cavity is formed, and a plurality of parallel resonant sound absorbers with different resonant frequencies can be provided, so as to improve the adjustment freedom of the sound absorption frequency band of the low-frequency broadband sound absorption metamaterial structure module based on metal foam, and further improve the ability to regulate the sound absorption performance of the low-frequency broadband sound absorption metamaterial structure module based on metal foam by embedding one or more rectangular cavities (the same as the implementation of the sub-cavity structure 202) in the composite resonant acoustic cavity layer 2.

[0035] In this embodiment, the metal foam layer 1 is a thin layer of lightweight porous material structure, and its porosity is greater than or equal to 60%, and can be made of one or a combination of two or more of foam aluminum, foam copper, foam nickel and foam alloys thereof. The first bottom plate 203, the second bottom plate 204, the rectangular enclosure 205, and the side plate 206 are all one or a combination of two or more of homogeneous plates, reinforced plates, ribbed plates, and sandwich panels, for example. Figure 6 (a) shows a homogenizing plate, Figure 6 (b) The stiffened plate shown, Figure 6 (c) The foam sandwich panel shown, Figure 6 (d) The honeycomb sandwich panel shown in FIG. 200 is a honeycomb sandwich panel. In this embodiment, the rectangular enclosure panel 205 and the side panel 206 are both made of homogeneous panels, and the first bottom panel 203 and the second bottom panel 204 are both made of reinforced panels.

[0036] refer to Figure 7 for Figure 1 Sound absorption coefficient curve of the medium and low frequency broadband sound absorption metamaterial structure, the specific parameters are: the thickness of the metal foam layer 1 is 5mm, 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 the 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.

[0037] Example 2 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 of embodiment 1, each low-frequency broadband sound absorbing metamaterial structure is connected in parallel in sequence, for example Figure 8 , Fig. 9 As shown, multiple low-frequency broadband sound absorbing metamaterial structures can be connected in parallel into one or more rows.

[0038] The low-frequency broadband sound absorbing metamaterial module in this embodiment consists of four different sound absorbing metamaterial structure modules. The lengths and depths of the sub-cavity structures 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 of different shapes and sizes. The sound absorption frequency band can be further widened through coupling, thereby obtaining better sound absorption performance.

[0039] In the specific implementation process, the thickness of the metal foam layer 1 of each low-frequency broadband sound absorbing metamaterial structure, the number of sub-cavity structures 202, the relative position of the sub-cavity structure 202 in the mother cavity structure 201, and the structural parameters of the sub-cavity structure 202 can be set to be partially or completely different.

[0040] Example 3 This embodiment discloses a low-frequency broadband sound-absorbing superstructure sound barrier based on metal foam, such as Fig.10 As shown, it includes a sound barrier shell structure 3, and the low-frequency broadband sound absorbing metamaterial structure in Example 1 and / or the low-frequency broadband sound absorbing metamaterial structure module in Example 2, and the low-frequency broadband sound absorbing metamaterial structure and / or the low-frequency broadband sound absorbing metamaterial module are arranged on the sound barrier shell structure 3.

[0041] Specifically, the sound barrier shell structure 3 includes a frame, a back plate, and a perforated or slotted protective plate. The back plate is arranged on a first side of the frame, and the perforated or slotted protective plate is arranged on a second side of the frame, and a cavity is formed between the perforated or slotted protective plate and the back plate. The low-frequency broadband sound absorbing metamaterial structure and / or the low-frequency broadband sound absorbing metamaterial module are arranged in the cavity, and the metal foam layer 1 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 plate.

[0042] In the specific implementation process, the first bottom 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 bottom plate 203 and the back plate are integrally formed to simplify the structure of the low-frequency broadband sound absorbing metastructure sound barrier and reduce costs.

[0043] At the same time, 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 be integrally formed therewith.

[0044] Example 4 This embodiment discloses another form of low-frequency broadband sound-absorbing metamaterial structure based on metal foam, such as Fig.11 As shown, on the basis of the low-frequency broadband sound-absorbing metamaterial structure in Example 1, multiple sub-cavities are added in parallel, which improves the adjustable freedom of structural parameters, which is beneficial to adjusting the sound absorption performance of the structure; at the same time, the bottom plate is reinforced to further improve the rigidity and strength of the structure, which is beneficial to improving the sound insulation performance of the structure.

[0045] In the specific implementation process, the metal foam layer and the composite resonant acoustic cavity layer of the sound absorbing metamaterial structure have various connection forms, such as Fig.12 The figure shows two connection forms of the metal foam layer and the composite resonant acoustic cavity layer of the low-frequency broadband sound absorbing metamaterial structure in Example 1 of the present invention. By opening holes in the metal foam layer and setting connecting substructures such as flange structures or ear structures on the rectangular enclosure and side panels, rivets or screws can be used to combine the metal foam layer and the composite resonant acoustic cavity layer into a whole sound absorbing metamaterial structure.

[0046] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A low-frequency broadband sound-absorbing metamaterial structure, characterized in that: It comprises 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; The composite resonant acoustic cavity layer comprises a mother cavity structure and a sub-cavity structure, wherein 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 wave can enter the mother cavity structure and the sub-cavity structure after propagating through the metal foam layer; The cavities of the mother cavity structure and the sub-cavity structure are both unidirectional cavities with equal cross-sections.

2. The low-frequency broadband sound-absorbing metamaterial structure according to claim 1, characterized in that: The composite resonant acoustic cavity layer comprises a first bottom plate, a second bottom plate, a rectangular enclosure plate and a side plate; The rectangular enclosure is connected to the first bottom plate and is enclosed and connected with the first bottom plate to form the mother cavity structure, and the metal foam layer is connected to the top of the rectangular enclosure; There are two side panels, the two side panels are connected inside the rectangular enclosure, and the second bottom panel is connected to the bottom of the two side panels, and cooperates with the side panels and the rectangular enclosure to enclose and connect to form the sub-cavity structure; The rectangular enclosure plate and the side plate may also be provided with a connecting substructure for connecting the metal foam layer.

3. The low-frequency broadband sound-absorbing metamaterial structure according to claim 1, characterized in that: One of the side panels and the rectangular enclosure panel can be integrally formed, that is, the cavity of the mother cavity structure can be an L-shaped cavity.

4. The low-frequency broadband sound-absorbing metamaterial structure according to claim 1, characterized in that: The first bottom plate, the second bottom plate, the rectangular enclosure plate, and the side plates are all selected from the group consisting of homogeneous plates, stiffened plates, ribbed plates, and sandwich plates, or a combination of two or more thereof.

5. The low-frequency broadband sound absorbing metamaterial structure according to any one of claims 1 to 4, characterized in that: At least one rectangular cavity, U-shaped cavity and / or L-shaped cavity may be connected in parallel or embedded in the composite resonant acoustic cavity layer; The parallel or embedded rectangular cavities, U-shaped cavities and / or L-shaped cavities are all unidirectional equal-section cavities and have openings facing the metal foam layer to increase the adjustment freedom of the sound absorption frequency band and improve the sound absorption capacity.

6. The low-frequency broadband sound absorbing metamaterial structure according to any one of claims 1 to 4, characterized in that: The metal foam layer is a thin layer of lightweight porous material or structure.

7. A low-frequency broadband sound-absorbing metamaterial module, characterized in that: The invention comprises two or more low-frequency broadband sound absorbing metamaterial structures according to any one of claims 1 to 6, wherein each of the low-frequency broadband sound absorbing metamaterial structures is sequentially connected in parallel.

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

9. A low-frequency broadband sound-absorbing superstructure sound barrier, characterized in that: It comprises a sound barrier shell structure, a low-frequency broadband sound absorbing metamaterial structure as described in any one of claims 1 to 6, and / or a low-frequency broadband sound absorbing metamaterial module as described in claim 7 or 8; The low-frequency broadband sound absorbing metamaterial structure and / or the low-frequency broadband sound absorbing metamaterial module are arranged on the sound barrier shell structure.

10. The low-frequency broadband sound-absorbing super-structure sound barrier according to claim 9 is characterized in that: The sound barrier shell structure includes a frame, a back plate, and a perforated or slotted protective plate; The back plate is arranged on the first side of the frame, the perforated or seamed protective plate is arranged on the second side of the frame, and a cavity is enclosed between the perforated or seamed protective plate and the back plate; The low-frequency broadband sound absorbing metamaterial structure and / or the low-frequency broadband sound absorbing metamaterial module are arranged 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; The first bottom plate of 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, or be formed integrally therewith. Meanwhile, the rectangular enclosure 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 be formed integrally therewith.

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