Broadband composite acoustic metamaterial component and design method and modular splicing method thereof

Abstract

The invention discloses a broadband composite acoustic meta-structure assembly and a design method and a modular splicing method thereof. The broadband composite acoustic meta-structure assembly comprises a base module, a meta-structure module and a porous material module. Based on structural parameter design conditions and sound absorption characteristic constraint conditions of the super-structure module and based on an incident sound field and super-structure module surface acoustic impedance matching theory, optimizing structural parameters of the super-structure module by using an optimization algorithm; the structural parameter design conditions comprise constraint conditions of structural size parameters of each resonant cavity sound absorption unit in the super-structure module and limiting conditions of the breadth area of the super-structure module; the sound absorption characteristic constraint condition comprises a sound absorption frequency constraint condition and a sound absorption coefficient constraint condition. According to the invention, by matching the high sound absorption characteristics of the metamaterial module and the sound absorption material module in different frequency band ranges, the broadband noise reduction performance of the metamaterial component is quickly realized, and the material thickness is greatly reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of new acoustic material design, and specifically relates to a broadband composite acoustic meta-structure component and a design method and a modular splicing method thereof. Background Art

[0002] Traditional noise control materials, such as porous sound-absorbing materials and resonant sound-absorbing structures, often have problems such as low low-frequency sound absorption efficiency, narrow frequency band, and large thickness. They are difficult to meet the needs of modern high-end equipment manufacturing industries such as large aircraft, rail transit, and new energy for new acoustic functional materials and their key application technologies, especially in low-frequency broadband noise reduction and lightweight structural design.

[0003] Acoustic metamaterials are a new type of acoustic functional material that can achieve specific acoustic properties through carefully designed microstructure units, providing a new approach to breaking through the performance bottleneck of traditional acoustic materials. However, a single type of acoustic metamaterial can often only achieve good sound absorption performance within a specific frequency band and has difficulty covering a wider frequency range. In order to broaden the effective sound absorption band of acoustic metamaterials, researchers have proposed a variety of composite acoustic metamaterial structures, such as combining resonant units with multiple structural parameters, or embedding porous materials in metaresonant cavity units. However, existing composite acoustic metamaterial design methods still have certain shortcomings: 1) The structure is complex and heavy, making it difficult to achieve modular design and large-scale splicing; 2) It is difficult to achieve a high sound absorption coefficient within a wide frequency band; 3) There is a lack of a systematic design method. These limitations limit its large-scale engineering application, especially in application scenarios that require lightweight and broadband noise reduction. For example, patent CN202110183801.6 proposes a multi-unit metasurface array and broadband acoustic lining unit structure, which achieves broadband acoustic energy dissipation through non-local coupling. However, its structure is relatively complex and heavy, and it is difficult to further expand the width through combination. Another patent also proposes a modular spliced ​​ring structure, which uses connectors to splice multiple rings into an integral structure. However, this design is mainly targeted at specific structural forms, is highly specialized, and does not involve broadband acoustic performance.

[0004] As we all know, traditional porous acoustic materials have good absorption effects on mid- and high-frequency noise, but it is difficult to effectively control mid- and low-frequency noise. Pure acoustic metamaterials have good low-frequency noise reduction characteristics. In theory, matching the two to give full play to the complementary characteristics of frequency bands to achieve broadband noise reduction design is a feasible design idea. However, due to the large thickness of existing metamaterials, the sound-absorbing materials formed by their matching are also thick, making them difficult to use in some extreme space environments.

[0005] Therefore, developing a sound-absorbing material with a simple structure, high sound absorption performance in a wide frequency band, and a thin structure has important theoretical significance and practical application value. Summary of the Invention

[0006] The purpose of the present invention is to provide a broadband composite acoustic metastructure component and its design method and modular splicing method in order to solve at least one of the above problems, so as to solve the problems in the prior art that metastructure materials are thick, difficult to achieve high sound absorption coefficients within a wide frequency band, and large-scale modular splicing and assembly. This solution adopts the design concept of frequency band matching to control broadband noise, uses an optimization algorithm to quickly optimize the structural parameters of the metastructure module, and constructs a specific parallel impedance matching calculation model for the metastructure module and the porous material module to match the high sound absorption characteristics of the two in different frequency bands. The metastructure module and the traditional sound absorption material module are alternately designed in parallel to quickly achieve broadband noise reduction performance of the metastructure component; through the mortise and tenon matching design around the metastructure module, the modular splicing and assembly of large-scale acoustic metastructure materials can be quickly achieved, while greatly compressing the thickness of the acoustic metastructure material. It has broad application prospects in the field of acoustic metastructure material preparation and assembly.

[0007] The purpose of the present invention is achieved through the following technical solutions: A first aspect of the present invention discloses a design method for a broadband composite acoustic metastructure component, wherein the broadband composite acoustic metastructure component includes a base module, a metastructure module, and a porous material module; Based on the structural parameter design conditions of the metamodule and its sound absorption characteristic constraints, as well as the theory of matching the incident sound field with the surface acoustic impedance of the metamodule, an optimization algorithm is used to optimize the structural parameters of the metamodule. The structural parameter design conditions include the constraints on the structural size parameters of each resonant cavity sound absorption unit in the super-module and the limiting conditions on the width area of ​​the super-module; The sound absorption characteristic constraint conditions include sound absorption frequency constraint conditions and sound absorption coefficient constraint conditions; the sound absorption frequency constraint conditions are set to a number of frequency points and / or a number of frequency bands; the sound absorption coefficient constraint conditions are set to be not less than or greater than a set value (corresponding to the sound absorption coefficient set value of the sound absorption frequency constraint conditions, 0 < set value ≤ 1); The optimization design is as follows: based on satisfying the sound absorption characteristics of the supermodule, the optimal solution of the supermodule structural parameters is solved within the constraints through the differential evolution algorithm (DE).

[0008] Preferably, the structural parameters of the supermodule are optimized by the following method: The structural parameters of the super-module include the inner cavity length of each resonant cavity sound absorption unit x , lumen width y, cavity height h and lumen wall thickness b , and the diameter of the embedded tube set in the resonance cavity sound absorption unit d and length l ; Depend on n The super-module is composed of parallel connection of resonance cavity sound absorption units, among which the i The resonant frequency of a resonant cavity sound absorbing unit is: ; but, h i Expressed as: ; Where 1≤ i ≤ n ; Discretize the set sound absorption frequency constraint into W frequency points, each angular frequency point is recorded as ω k , then i The resonant cavity sound absorption unit is at the angular frequency point ω k Acoustic impedance R i,k Acoustic impedance X i,k The expression is: ; ; Then, i The acoustic impedance expression of a resonant cavity sound absorption unit is: ; Then, according to the parallel impedance principle, the acoustic impedance of the supermodule is Z ak The expression is: ; Then, the acoustic impedance of the metamodule is R ak Acoustic impedance X ak Expressed as: ; ; Then, the sound absorption coefficient of the supermodule is α k The expression is: ; Where, η is the shear viscosity of air, j is the imaginary part,S is the area of ​​the incident sound field, is the air density; Based on the structural parameter design conditions and sound absorption characteristic constraints, the differential evolution algorithm is used to solve the minimum structural parameters of the super-module while meeting the acoustic indicators. Among them, the structural parameter design conditions and sound absorption coefficient constraints are expressed as: ; Where, α u is the sound absorption coefficient setting value, lb and ub The parameters to be solved are x i 、 y i 、 d i and l i The upper and lower bounds of .

[0009] Preferably, the surface acoustic impedance matching and the sound absorption coefficient of the broadband composite acoustic meta-assembly are calculated by the following method: A1. The broadband composite acoustic meta-component z Acoustic impedance of a metamodule Z az for: ; Where, Z i,k For the z The first supermodule i The resonant cavity sound absorption unit is at the angular frequency point ω k The acoustic impedance, n For the z The total number of resonant cavity sound-absorbing units in a supermodule; A2. The broadband composite acoustic meta-component m Acoustic impedance of a porous material module Z pm for: ; Where, is the air density, is the speed of sound in air, σ m For the m The flow resistivity of a porous material module, f is the frequency; A3. Acoustic impedance of the broadband composite acoustic meta-assembly Zt for: ; In the formula, the superscript Z is the total number of supermodules, M is the total number of porous material modules; A4. Sound absorption coefficient of the broadband composite acoustic meta-assembly α A for: ; Where Re and Im represent the real and imaginary parts of the normalized acoustic impedance, respectively.

[0010] The second aspect of the present invention discloses a broadband composite acoustic metastructure component, which is obtained by using any of the above-mentioned design methods; The broadband composite acoustic metastructure component includes a base module, a metastructure module and a porous material module; The mounting surface of the base module is divided into alternately arranged super-structure module plug-in areas and porous material module plug-in areas by a partition frame; The super-module is assembled in the super-module plug-in area. The super-module is composed of several resonance cavity sound absorption units connected in parallel, which are used for sound absorption in the medium and low frequency bands. The porous material module is assembled in the porous material module plug-in area and is used for sound absorption in the medium and high frequency bands; The meta-structure modules and the porous material modules are alternately assembled on the base module.

[0011] The alternation referred to in this scheme is: all adjacent to the super-structure module are porous material modules, and all adjacent to the porous material modules are super-structure modules.

[0012] According to different sound absorption requirements, the metastructure modules of the broadband composite acoustic metastructure assembly in this solution can adopt the same or different designs, and the porous material modules can also adopt the same or different designs.

[0013] Preferably, the outer wall of the meta-module is provided with a protrusion at the bottom, and the inner wall of the meta-module insertion area is provided with a groove that matches the structure of the protrusion. The meta-module is assembled in the meta-module insertion area through the plug-in fit of the protrusion and the groove. By plugging and fitting the protrusion of the meta-module with the groove of the base module, the meta-module can be securely assembled to the base module.

[0014] Preferably, there is an interference fit between the protrusion and the groove, which ensures a reliable connection after assembly and prevents movement or sliding during use.

[0015] Preferably, the outer contours of the protrusion and the groove are arc-shaped or wedge-shaped with an obtuse angle, so as to further ensure an interference fit between the protrusion and the groove.

[0016] Preferably, the length of the protrusion should not be too long, preferably 1 / 25 to 1 / 5 of the length of the super-module; the width should not be greater than the width of the bulkhead, preferably 0.5 to 1 mm; the height should be less than the height of the bulkhead, preferably 1 / 2 of the bulkhead height.

[0017] Preferably, the super-structure module is divided into a plurality of resonance cavity sound absorbing units by an inner partition, and each of the resonance cavity sound absorbing units includes an embedded tube arranged along the height direction and an opening opened on the sound absorbing surface, and the embedded tube is connected to the opening.

[0018] The length of the embedded tube in each resonant cavity sound absorption unit in the super-structure module can be designed to be of varying lengths, and the openings can also be designed to have different diameters. The structural optimization design is determined based on the specific sound absorption characteristic constraints. The embedded tube is a hollow tube.

[0019] Preferably, the surface of the super-module plug-in area is provided with partition slots that are plugged into and matched with the inner partitions, so as to further limit and position the super-module.

[0020] Preferably, the surface of the porous material module plug-in area is a flat surface, and the porous material module is assembled and limited by a partition frame.

[0021] A third aspect of the present invention discloses a modular assembly method for a broadband composite acoustic meta-assembly as described above, wherein the broadband composite acoustic meta-assembly as described above is assembled in a modular form; The outer wall surfaces of the base module at the super-structure module plug-in area and the porous material module plug-in area are respectively provided with tenons and tenons with matching structures; Adjacent broadband composite acoustic metastructure components are assembled and connected by plugging and fitting the tenons and mortises on the outside of their base modules to form a large-scale acoustic metastructure material; and in the large-scale acoustic metastructure material, the metastructure modules and the porous material modules are arranged alternately.

[0022] Through the plug-in cooperation between the tenon and the mortise, a reliable connection between adjacent broadband composite acoustic metastructure components can be achieved; and by setting the tenon / mortise on the outer wall of the metastructure module plug-in area and the mortise / mortise on the outer wall of the porous material module plug-in area, the broadband composite acoustic metastructure component after connection can still maintain the form of alternating arrangement of the metastructure module and the porous material module, so as to achieve the expansion and extension of the broadband composite acoustic metastructure component, and then construct a large-scale acoustic metastructure material through modular assembly.

[0023] Preferably, the tenon and the mortise are interference fit to ensure a reliable connection between the broadband composite acoustic metastructure components and prevent relative movement during use.

[0024] Preferably, the cross-section of the tenon is an inverted trapezoid. The trapezoid is preferably designed with the side closest to the base module as the top side (short side) and the side away from the base module as the bottom side (long side). Thus, when the broadband composite acoustic meta-assemblies are connected to each other, a longitudinal limit is formed between the tenon and the mortise, and the connection can only be released by movement in a single direction.

[0025] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention adopts the design concept of controlling broadband noise by frequency band matching, uses optimization algorithms to quickly optimize the structural parameters of the metastructure module, and through the construction of a specific parallel impedance matching calculation model for the metastructure module and the porous material module, matches the high sound absorption characteristics of the two in different frequency bands. The metastructure module and the traditional sound absorption material module are alternately designed in parallel, which can quickly realize the prediction of the broadband noise reduction performance of the metastructure component and greatly compress the thickness of the acoustic metastructure material.

[0026] (2) The acoustic metastructure component of the present invention has a simple and lightweight structure and adopts a flexible modular plug-in design method. It can implement customized frequency and band selection, multi-parameter design of metastructure modules and porous material modules for noise of specified frequencies. This method does not limit the design parameters of the metastructure module (systematic optimization design can be carried out according to target requirements). In addition, the tenons and grooves around the acoustic metastructure component can realize the horizontal plug-in combination of multi-parameter metastructure components to prepare large-scale acoustic metastructure material devices.

[0027] (3) The present invention modularizes the base, metastructure modules and porous materials of the acoustic metastructure component, which can be quickly modularized for processing and splicing and assembly, thereby improving production efficiency and adaptability. This design method is particularly suitable for application scenarios that have high requirements for lightness, broadband sound absorption performance and splicing stability, such as large aircraft, subway and ship siding, sound barriers and wall panels, and other extreme space application environments. It has important practical significance for promoting the application of acoustic metastructure materials in high-end equipment manufacturing. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of the three-dimensional structure of the alternating composite acoustic metastructure in Example 1; Figure 2 Schematic diagram of the three-dimensional structure of the base module in Example 1; Figure 3 Schematic diagram of the three-dimensional structure of the super-module in Example 1, where a is a top view and b is a bottom view; Figure 4 Schematic diagram of the structure of any resonant cavity sound absorbing unit in the super-structure module in Example 1; Figure 5The sound absorption coefficient test data of the aviation cotton porous material module, the superstructure module and the acoustic superstructure assembly in Example 4, and the theoretical calculation data of the sound absorption coefficient of the acoustic superstructure assembly; Figure 6 This is a schematic diagram of the horizontal assembly of the modularly spliced ​​large-scale acoustic metamaterial in Example 5; Figure 7 The sound absorption coefficient test data of the modular large-scale acoustic metamaterial in Example 5; Explanation of the accompanying figure numbers: 1. Base module, 11. Partition frame, 12. Groove, 13. Partition slot, 14. Tenon, 15. Mortise, 2. Superstructure module, 21. Resonance cavity sound absorption unit, 22. Protrusion, 23. Inner partition, 24. Embedded tube, 25. Opening, 3. Porous material module. DETAILED DESCRIPTION

[0029] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0030] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not require further definition or explanation in subsequent drawings.

[0031] In the description of the present invention, it should be noted that the terms "longitudinal", "transverse", "horizontal", "bottom", "inside", "outside", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limiting the present invention.

[0032] The following matters not covered hereunder may all adopt existing technologies. In the absence of conflict, the following embodiments and features therein may be combined with each other.

[0033] Example 1 A broadband composite acoustic meta-component design method, such as Figures 1 to 4 As shown, the broadband composite acoustic metastructure component includes a base module 1, a metastructure module 2 and a porous material module 3; In this embodiment, the metamodule 2 is composed of a plurality of resonant cavity sound-absorbing units 21 connected in parallel. The structural parameter optimization design method is: based on the design conditions (including the structural parameter design conditions of the metamodule 2 and the sound absorption characteristic constraints), the results are calculated based on the theoretical matching between the incident sound field and the surface acoustic impedance of the metamodule 2.

[0034] The structural parameter design conditions of the super-module 2 include the inner cavity length of each resonant cavity sound absorbing unit 21 in the super-module 2 x , lumen width y , cavity height h and lumen wall thickness b , and the diameter of the embedded tube 24 d and length l , and structural design indicators such as the width area of ​​the super-structure module 2, and the sound absorption characteristic constraints include acoustic constraint design indicators such as sound absorption frequency and sound absorption coefficient.

[0035] The sound absorption frequency constraint condition can be set to several frequency points and / or several frequency bands, and the sound absorption coefficient constraint condition can be set to ensure that the sound absorption coefficient value corresponding to the sound absorption frequency is not less than or greater than a certain set value (set according to the target sound absorption coefficient requirement, taking 0 < set value ≤ 1), thereby realizing a target-oriented frequency and band selection design.

[0036] By using the differential evolution (DE) optimization design algorithm, the structural parameters of the metamodule 2 can be quickly solved, including the structural dimensions of the cavity and embedded tube 24 of each resonant cavity sound-absorbing unit 21 in the metamodule 2, so as to minimize the structural dimensions of the metamodule 2 (mainly the inner cavity height of the resonant cavity sound-absorbing unit 21) while meeting the acoustic indicators.

[0037] The theoretical models involved in DE optimization design algorithm, such as Figure 4 As shown, for n The super-structure module 2 is composed of a number of resonance cavity sound absorbing units 21 connected in parallel. i Resonance cavity sound absorption unit 21 (1≤ i ≤ n ), the relationship between the resonance frequency and the structural parameters is: ; Where, f i 、 d i 、 x i 、 y i 、 h i 、 b and l i Respectively i The resonant frequency of the resonant cavity sound absorbing unit 21, the diameter of the embedded tube 24 set in the resonant cavity sound absorbing unit 21, the inner cavity length, inner cavity width, inner cavity height of the resonant cavity sound absorbing unit 21, the wall thickness / inner cavity wall thickness of the embedded tube 24 and the length of the embedded tube 24.

[0038] but,h i The expression is expressed as: ; For n The super-structure module 2 is composed of a plurality of resonance cavity sound absorbing units 21 connected in parallel. h i Maximum h max As the optimization objective function, the expression is: ; In order to calculate the sound absorption coefficient of the supermodule 2 within the set frequency band, the set sound absorption frequency constraint condition is discretized into W frequency points, each angular frequency point is recorded as ω k , No. i The resonant cavity sound absorbing unit 21 is at the angular frequency point ω k Acoustic impedance R i,k Acoustic impedance X i,k The expression is: ; ; Then, i The acoustic impedance expression of a resonant cavity sound absorbing unit 21 is: ; According to the parallel impedance principle, the acoustic impedance of the super-module 2 Z ak The expression is: ; Acoustic impedance of the Metamodule 2 R ak Acoustic impedance X ak Expressed as: ; ; Then, the sound absorption coefficient of the supermodule 2 is α k The expression is: ; Where, η is the shear viscosity of air, j is the imaginary part, S is the area of ​​the incident sound field (also the sound absorption surface area of ​​the metamodule 2).

[0039] The optimization design problem of the super-module 2 can be expressed as follows: in the set frequency band [ f l , f r ], design a set of structural parameters ( x i 、 y i 、 d i 、 l i 、 h i ),in i ∈[1, n ], so that the average sound absorption coefficient of the super-module 2 α k (or minimum value) not less than or greater than the sound absorption coefficient setting value α u .

[0040] Based on the above, the design problem of the super-module 2 can be transformed into the following standard mathematical optimization problem with inequality constraints. Then, minimize the objective function h max Expressed as min h max .

[0041] The structural parameter design conditions and sound absorption coefficient constraints that need to be satisfied in the optimization problem are expressed as follows: ; Where, lb and ub The parameters to be solved are x i 、 y i 、 d i and l i The upper and lower bounds of .

[0042] In this embodiment, the DE algorithm is used to optimize the above optimization problem.

[0043] In this embodiment, the structural parameters of the acoustic metastructure component are precisely optimized and designed by acoustic impedance matching theory and DE algorithm to quickly achieve its low-bandwidth and high sound absorption performance.

[0044] The calculation method of the sound absorption coefficient of the broadband composite metastructure component in which the optimized metastructure module 2 and the porous material module 3 are alternately connected in parallel includes: A1. The broadband composite acoustic meta-component z The acoustic impedance of a metamodule 2Z az for: ; Where, Z i,k For the z In supermodule 2 i The resonant cavity sound absorbing unit 21 is at the angular frequency point ω k The acoustic impedance, n For the z The total number of resonant cavity sound absorbing units 21 in each supermodule 2; A2. The broadband composite acoustic meta-component m Acoustic impedance of porous material module 3 Z pm for: ; Where, is the air density, is the speed of sound in air, σ m For the m The flow resistivity of the porous material module 3, f is the frequency; A3. Acoustic impedance of the broadband composite acoustic meta-assembly Z t for: ; In the formula, the superscript Z is the total number of supermodule 2, subscript M is the total number of porous material modules 3; A4. Sound absorption coefficient of the broadband composite acoustic meta-assembly α A for: ; Where Re and Im represent the real and imaginary parts of the normalized acoustic impedance, respectively.

[0045] Example 2 This embodiment provides an optimization mathematical model based on the inner cavity height of the super-module 2 disclosed in Example 1, which takes the optimization target as the optimization target, and optimizes the structural parameters of the super-module 2 to meet the design conditions.

[0046] In this embodiment, the design conditions of the super-module 2 are: the super-module 2 includes 3×3 rectangular cross-section embedded tubular resonant cavity sound absorbing units 21 (the number of units is n =9); the wall thickness of the embedded tube 24 and the wall thickness of the cavity b are all set to 1mm; structural parameters (x i 、 y i 、 d i 、 l i ) lb The value is set to [15, 15, 0.8, 1], the upper bound ub The value is set to [15, 15, 4, 11]; the inner cavity height h i are all set to be less than 12mm, and the height of the embedded tube 24 in each unit is less than the height of its cavity; set the sound absorption characteristic constraints of the super-module 2: set the sound absorption frequency band to [500, 1000], and the average sound absorption coefficient α k ≥0.65.

[0047] In this embodiment, the DE algorithm in the Geatpy library is called by Python language, and based on the above design conditions, the unit cavity height in the super module 2 is calculated. h i Perform optimization solution.

[0048] In this embodiment, the structural parameter optimization design result of the super-module 2 is as follows: the super-module 2 is composed of 9 resonance cavity sound absorption units 21 connected in parallel, and the structural parameters of the 9 units are shown in Table 1 (including the unit cavity length x i , unit cavity width y i , unit wall thickness b , embedded tube 24 diameter d i , embedded tube length l i Height of unit cavity h i ), the maximum height of the cavity of the super-structure module 2 is only 11.98 mm, and the average sound absorption coefficient is 0.65. This design result meets the causal law of minimizing the design thickness.

[0049] Table 1 Structural parameters of supermodule 2

[0050] Example 3 A broadband composite acoustic meta-component and its modular splicing design method, such as Figures 1 to 4 As shown, it includes a base module 1, a super structure module 2 and a porous material module 3; The mounting surface of the base module 1 is divided into alternately arranged super-structure module plug-in areas and porous material module plug-in areas by the partition frame 11; The super-module 2 is assembled in the super-module plug-in area. The super-module 2 is composed of a number of resonance cavity sound-absorbing units 21 connected in parallel, which are used for sound absorption in the medium and low frequency bands. The porous material module 3 is assembled in the porous material module plug-in area and is used for sound absorption in the medium and high frequency bands; The meta-modules 2 and the porous material modules 3 are alternately assembled on the base module 1 .

[0051] More specifically, in this embodiment: The base module 1 has a square cross-section, with a bulkhead 11 on its surface, separating the base module into alternating metamodule and porous material module insertion areas. That is, adjacent to a metamodule insertion area is a porous material insertion area, and vice versa. In this embodiment, the bulkhead 11 divides the base module 1 into alternating square metamodule and porous material insertion areas (2×2). The bulkhead 11 protrudes 2mm above the base module 1 surface and is 1mm wide.

[0052] The meta-module 2 is a cube with four protrusions 22 located in the center of the lower side of its outer walls. Furthermore, four grooves 12 are located in the center of the lower side of the inner wall of the bulkhead 11 in the meta-module insertion area. In this embodiment, the four grooves 12 on the lower side of the inner wall of the bulkhead 11 in the meta-module insertion area correspond one-to-one with the four protrusions 22 on each side of the meta-module 2. The grooves 12 and protrusions 22 cooperate with each other, forming an interference fit. The grooves 12 and protrusions 22 are designed to be moderately long (5 mm), with a horizontal width no greater than the width of the bulkhead 11 (0.5 mm) and a vertical height less than the height of the bulkhead 11 (1 mm). Their cross-sections are curved or wedge-shaped with an obtuse angle, ensuring smooth insertion and removal of the meta-module 2 from the base module 1 and an interference fit. When assembling the meta-module 2 , the meta-module 2 can be directly pressed into the bulkhead 11 of the meta-module plug-in area, and is constrained by the protrusions 22 and the grooves 12 .

[0053] In this embodiment, the super-structure module 2 is composed of a number of resonance cavity sound absorbing units 21 connected in parallel, such as Figure 3 、 4Specifically, the inner cavity of the metamodule 2 is divided into nine resonant cavity sound-absorbing units 21 by internal partitions 23 in a 3×3 arrangement. Each resonant cavity sound-absorbing unit 21 has an embedded tube 24 (a hollow circular tube or a hollow square tube) extending vertically from the top surface (sound-absorbing surface) of the metamodule 2, extending from the center of the inner cavity sound-absorbing unit 21. An opening 25, matching the diameter of the embedded tube 24, is provided at one end of the top surface (sound-absorbing surface) of the metamodule 2. This opening 25 communicates with the embedded tube 24. The structural parameters of the embedded tube 24, such as length and diameter, of each resonant cavity sound-absorbing unit 21 can be designed to be the same or different. Similarly, the diameter of the opening 25 can also be designed to be the same or different, determined by optimizing the design based on the sound absorption constraints. The base surface within the metamodule insertion area is also provided with a partition slot 13 that matches the bottom of the metamodule 2. In this embodiment, the configuration of the partition slots 13 on the base surface in the meta-module plug-in area corresponds one-to-one with the configuration of the inner partition 23 inside the meta-module 2. The two are plugged into each other to achieve sealing of the bottom of the meta-module 2.

[0054] In this embodiment, the porous material module has a flat base surface within the insertion area. The porous material module 3 is assembled with the bulkhead 11 within the insertion area. The material parameters of the porous material module 3 are selected based on the sound absorption design requirements and calculation results. The porous material module 3 has high sound absorption performance in the mid- and high-frequency bands. Depending on the requirements of the use environment, the sound absorption material selected is foam, fiber, activated carbon, or other types.

[0055] The meta-structure modules 2 and the porous material modules 3 are alternately plugged into the surface of the base module 1 .

[0056] The areas of the super-structure module plug-in area and the porous material module plug-in area can be the same or different.

[0057] The tenons 14 and mortises 15 around the acoustic meta-structure components can be used to connect several meta-structure components horizontally and form a large-scale acoustic meta-structure material. Specifically, tenons 14 and mortises 15 are provided on all four sides of the base module 1. Figure 1 、 2 As shown, tenons 14 are provided in the middle of the outward-facing sides of the metamodule insertion area, while tenons 15 are provided in the middle of the outward-facing sides of the porous material module insertion area. The structural dimensions of the tenons 14 and tenons 15 on the periphery of the base module 1 match each other, allowing multiple groups of base modules 1 to be laterally plugged into each other, with the interlocking tenons 14 and tenons 15 forming an interference fit. The tenons 14 and tenons 15 have an inverted trapezoidal cross-section, with the top edge of the trapezoid coplanar with the bottom surface of the base module 1 being shorter than the bottom edge of the trapezoid away from the bottom surface. The cross-sectional height of the tenons 14 and tenons 15 is less than the thickness of the base module 1.

[0058] Example 4 This embodiment provides a calculation of the sound absorption coefficient of a composite acoustic metastructure assembly in which a metastructure module 2 and a porous material module 3 are alternately combined in parallel after the optimized design of Embodiments 1 and 2.

[0059] In this embodiment, the porous material module 3 is made of traditional aviation cotton material with a flow resistance of 12043 Pa·s·m -2 , the density is 18.7 kg·m -3 , the thickness is equal to the thickness of the super-module 2.

[0060] In this embodiment, the sound absorption coefficient test data of the aviation cotton porous material module 3, the sound absorption coefficient test data of the super structure module 2, the sound absorption coefficient test data of the acoustic super structure component and the theoretical calculation data thereof are as follows: Figure 5 shown.

[0061] The sound absorption coefficient test data is obtained from acoustic impedance tube testing.

[0062] In this embodiment, Figure 5 It can be seen that in the low and medium frequency bands, the sound absorption coefficient of the porous material module 3 of the traditional aviation cotton is low, and the sound absorption coefficient of the simple superstructure module 2 is much higher than that of the porous material module 3 of the aviation cotton; but in the high and medium frequency bands, the two are opposite, which is also the starting point of the frequency band matching design concept of the present invention. The theoretical calculation results of the sound absorption coefficient of the broadband composite acoustic metastructure component are obtained from Example 1. α A The calculation expression is obtained, which shows that it is basically consistent with the test data. The important things are: 1) In the frequency band of 500-1000Hz, the theoretical and test data of the sound absorption coefficient of the broadband composite acoustic meta-structure component are both high, with an average sound absorption coefficient of 0.63 (test value), while the average sound absorption coefficient of the porous material module 3 of the aviation cotton is only 0.28, indicating that the high sound absorption performance of the broadband composite acoustic meta-structure component in this frequency band is mainly contributed by the super-structure module 2; 2) In the frequency band above 1000Hz, the sound absorption coefficient of the super-structure module 2 is pulled up by the porous material module 3 of the aviation cotton, and the sound waves are Repeated air friction and heat exchange within the aviation cotton porous material module 3 efficiently convert acoustic energy into thermal energy, indicating that the broadband composite acoustic metaassembly's sound absorption capacity in this frequency band is primarily contributed by the aviation cotton porous material module 3. 3) In the 500-1700 Hz frequency band, the broadband composite acoustic metaassembly's sound absorption coefficient is higher than that of the aviation cotton porous material module 3 alone, with an average sound absorption coefficient of 0.69, while the average sound absorption coefficient of the aviation cotton porous material module 3 is only 0.48. Therefore, the broadband composite acoustic metaassembly designed through this parallel alternating combination improves the sound absorption performance of the metaassembly 2 in the mid-to-high frequency range and the porous material module 3 in the mid-to-low frequency range, greatly broadening the effective sound absorption frequency band.

[0063] In this embodiment, the thickness of the base at the plug-in area of ​​the metamodule and the porous material module is 1 mm, and the thickness of the broadband composite acoustic metaassembly is 13.98 mm. The calculated equivalent surface density is only 2.87 kg·m -2 , which is about 1 / 3 lighter than a simple Super Module 2.

[0064] In this embodiment, research on the sound absorption coefficient of a broadband composite acoustic meta-assembly demonstrates that, by combining the impedance and sound absorption characteristics of Meta-Module 2 and Porous Material Module 3, combined with the flexible and optimizable design of Meta-Module 2, this design approach can be widely applied to achieve superior low-bandwidth noise reduction performance. Compared to a single Meta-Module 2, Porous Material Module 3 is a lightweight material. By combining the two in parallel, high broadband sound absorption performance can be achieved without significantly increasing the weight of Meta-Module 2. This is particularly important for applications where weight, thickness, and low-bandwidth noise reduction are a key consideration.

[0065] Example 5 See also Figures 6 and 7 This embodiment provides a modular splicing design method for a large-scale broadband composite acoustic metamaterial and its sound absorption coefficient test data. The broadband composite acoustic metamaterial component of Example 4 is used. By horizontally plugging the tenon 14 and the tenon groove 15 on the base module 1 of multiple sets of broadband composite acoustic metamaterial components, and vertically plugging the metamaterial module 2 and the porous material module 3 on the base module 1, a large-scale acoustic metamaterial device is spliced ​​and assembled. The schematic diagram is shown as follows: Figure 6 shown.

[0066] The design parameters of the multiple groups of meta-modules 2 and porous material modules 3 can be the same or different, and can be selected and designed according to design requirements.

[0067] In this embodiment, the sound absorption coefficient test data of the large-scale acoustic metamaterial specimen is as follows: Figure 7 shown.

[0068] The area of ​​the large-scale acoustic metamaterial specimen is 1m×1m.

[0069] The sound absorption coefficient test data is obtained from an acoustic reverberation chamber test.

[0070] In this embodiment, Figure 7 It can be seen that the test results of the sound absorption coefficient of the large-format acoustic metamaterial specimens show that: 1) in the frequency band of 500-1000Hz, the average sound absorption coefficient of the large-format acoustic metamaterial is increased to 0.75, and a sound absorption peak appears, indicating that its sound absorption performance can still reflect the high sound absorption characteristics of the above-mentioned metastructure module 2 and metastructure components in this frequency band; 2) in the wide frequency band of 500-10000Hz, the average sound absorption coefficient is 0.92, showing excellent broadband and high sound absorption and noise reduction capabilities.

[0071] The causal law of large-scale acoustic metamaterials reveals the limiting relationship between the minimum thickness of a sound-absorbing material and its sound absorption coefficient. Therefore, based on the causal law of metamaterials, when the average sound absorption coefficient is 0.92 between 500 and 10,000 Hz, the minimum thickness of a simple resonant cavity acoustic metamaterial should be 59.56 mm. However, the thickness of the acoustic metaassembly of the present invention is only 13.98 mm, a 76.5% reduction from the causal law. This demonstrates that the alternating parallel composite metaassembly employed in this solution can effectively reduce the required thickness of the sound-absorbing material and achieve excellent sound absorption performance within the 500-10,000 Hz broadband.

[0072] The sound absorption coefficient test results of the large-scale acoustic metamaterial specimens verified the broadband noise reduction capability of the design scheme of the present invention. The present invention will provide a set of practical application design solutions for the widespread application of thin and light broadband acoustic metamaterials.

[0073] In summary, the present invention has a simple and lightweight structure, can be quickly modularized and assembled, can well achieve broadband noise reduction performance and highly modular assembly process requirements, and has broad application prospects in the field of acoustic metamaterial preparation and assembly.

[0074] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A design method for a broadband composite acoustic meta-assembly, characterized in that: A broadband composite acoustic metastructure component includes a base module (1), a metastructure module (2), and a porous material module (3); based on the structural parameter design conditions of the metastructure module (2) and its sound absorption characteristic constraint conditions, and based on the incident sound field and the surface acoustic impedance matching theory of the metastructure module (2), an optimization algorithm is used to optimize the structural parameters of the metastructure module (2); The structural parameter design conditions include the constraints on the structural size parameters of each resonant cavity sound absorption unit (21) in the super-structure module (2) and the limiting conditions on the width area of ​​the super-structure module (2); The sound absorption characteristic constraint conditions include sound absorption frequency constraint conditions and sound absorption coefficient constraint conditions; the sound absorption frequency constraint conditions are set to a number of frequency points and / or a number of frequency bands; the sound absorption coefficient constraint conditions are set to be not less than or greater than a set value; The optimization design is as follows: taking the sound absorption characteristics of the super-structure module (2) as the optimization basis, the optimal solution of the structural parameters of the super-structure module (2) is solved within the constraints through the differential evolution algorithm.

2. The method for designing a broadband composite acoustic metacomponent according to claim 1, characterized in that: The structural parameters of the super-module (2) are optimized by the following method: The structural parameters of the super-structure module (2) include the inner cavity length of each resonant cavity sound absorption unit (21) x , lumen width y , cavity height h and lumen wall thickness b , and the diameter of the embedded tube (24) provided in the resonance cavity sound absorbing unit (21) d and length l ; Depend on n A superstructure module (2) is composed of a plurality of resonance cavity sound absorption units (21) connected in parallel, wherein the first i The resonant frequency of the resonant cavity sound absorbing unit (21) is: ； but, h i Expressed as: ； Where 1≤ i ≤ n ; Discretize the set sound absorption frequency constraint into W frequency points, each angular frequency point is recorded as ω k , then i The resonant cavity sound absorbing unit (21) is at the angular frequency point ω k Acoustic impedance R i,k Acoustic impedance X i,k The expression is: ； ； Then, i The acoustic impedance expression of a resonant cavity sound absorption unit (21) is: ； Then, according to the parallel impedance principle, the acoustic impedance of the superstructure module (2) is Z ak The expression is: ； Then, the acoustic impedance of the supermodule (2) R ak Acoustic impedance X ak Expressed as: ； ； Then, the sound absorption coefficient of the superstructure module (2) is α k The expression is: ； Where, η is the shear viscosity of air, j is the imaginary part, S is the area of ​​the incident sound field, ρ 0 is the air density; Based on the structural parameter design conditions and sound absorption characteristic constraints, the differential evolution algorithm is used to solve the minimum structural parameters of the super-structure module (2) while meeting the acoustic indicators; Among them, the structural parameter design conditions and sound absorption coefficient constraints are expressed as: ； Where, α u is the sound absorption coefficient setting value, lb and ub The parameters to be solved are x i 、 y i 、 d i and l i The upper and lower bounds of .

3. The method for designing a broadband composite acoustic metacomponent according to claim 1, wherein: The surface acoustic impedance matching and sound absorption coefficient of the broadband composite acoustic meta-assembly are calculated using the following method: A1. The broadband composite acoustic meta-component z The acoustic impedance of a supermodule (2) Z az for: ； Where, Z i,k For the z The first of the supermodules (2) i The resonant cavity sound absorbing unit (21) is at the angular frequency point ω k The acoustic impedance, n For the z The total number of resonant cavity sound absorbing units (21) in the super-module (2); A2. The broadband composite acoustic meta-component m Acoustic impedance of a porous material module (3) Z pm for: ； Where, ρ 0 is the air density, c 0 is the speed of sound in air, σ m For the m The flow resistivity of the porous material module (3), f is the frequency; A3. Acoustic impedance of the broadband composite acoustic meta-assembly Z t for: ； Where, Z is the total number of supermodules (2), M is the total number of porous material modules (3); A4. Sound absorption coefficient of the broadband composite acoustic meta-assembly α A for: ； Where Re and Im represent the real and imaginary parts of the normalized acoustic impedance, respectively.

4. A broadband composite acoustic meta-assembly, characterized in that: Obtained by adopting the design method according to any one of claims 1 to 3; The mounting surface of the base module (1) is divided into alternately arranged super-structure module plug-in areas and porous material module plug-in areas by a partition frame (11); The super-structure module (2) is assembled in the super-structure module plug-in area. The super-structure module (2) is composed of a plurality of resonance cavity sound absorption units (21) connected in parallel and is used for sound absorption in the medium and low frequency bands. The porous material module (3) is assembled in the porous material module plug-in area and is used for sound absorption in the medium and high frequency bands; The super-structure modules (2) and the porous material modules (3) are alternately assembled on the base module (1).

5. The broadband composite acoustic metacomponent according to claim 4, characterized in that: The bottom of the outer wall of the super-module (2) is provided with a protrusion (22), and the inner wall of the super-module plug-in area is provided with a groove (12) that matches the structure of the protrusion (22). The super-module (2) is assembled in the super-module plug-in area by plugging and fitting the protrusion (22) and the groove (12).

6. The broadband composite acoustic metacomponent according to claim 5, characterized in that: The protrusion (22) and the groove (12) are in an interference fit; and / or the outer contours of the protrusion (22) and the groove (12) are in an arc shape or a wedge shape with an obtuse angle.

7. The broadband composite acoustic metacomponent according to claim 4, characterized in that: The super-structure module (2) is divided into a plurality of resonant cavity sound absorbing units (21) by an inner partition (23), and each of the resonant cavity sound absorbing units (21) includes an embedded tube (24) arranged along the height direction and an opening (25) opened on the sound absorbing surface, and the embedded tube (24) is connected to the opening (25).

8. The broadband composite acoustic metacomponent according to claim 7, characterized in that: The surface of the super-module plug-in area is provided with a partition slot (13) that is plugged into and matched with the inner partition (23).

9. A modular splicing method for a broadband composite acoustic meta-assembly, characterized in that: The broadband composite acoustic meta-assembly according to any one of claims 4 to 8 is assembled in a modular form; The base module (1) is provided with a tenon (14) and a tenon groove (15) with matching structures on the outer wall surfaces of the super-structure module plug-in area and the porous material module plug-in area respectively; Adjacent broadband composite acoustic metastructure components are assembled and connected by plugging and fitting the tenon (14) and the mortise (15) to form a large-scale acoustic metastructure material; and in the large-scale acoustic metastructure material, the metastructure modules (2) and the porous material modules (3) are alternately arranged.

10. The modular assembly method of a broadband composite acoustic meta-assembly according to claim 9, characterized in that: The tenon (14) and the tenon groove (15) are in interference fit.

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