Low-frequency broadband acoustic metamaterial structure and rapid design method

Abstract

The present invention discloses a low-frequency broadband sound-absorbing metamaterial structure and a rapid design method. The metamaterial structure includes an enclosure panel, a partition board, a wave-tuning channel, and a self-stabilizing multi-degree-of-freedom sound absorber. The enclosure panel is a cylindrical structure with an open top. The partition board is arranged inside the enclosure panel to form at least one acoustic channel inside the enclosure panel. The acoustic channel, together with the enclosure panel and the partition board, constitutes the wave-tuning channel. The self-stabilizing multi-degree-of-freedom sound absorber includes a self-stabilizing sound-absorbing medium and multi-degree-of-freedom wave-guiding holes. The self-stabilizing sound-absorbing medium is filled in the acoustic channel, and the multi-degree-of-freedom wave-guiding holes are arranged on the self-stabilizing sound-absorbing medium. The present invention is applied to the fields of new materials, new structures, and their design technologies for noise control. It not only has the advantages of low cost, high reliability, low-frequency broadband sound-absorbing performance, multi-degree-of-freedom impedance modulation, self-stabilization, and load-bearing capacity, but also has the advantages of simple design process, rapid and efficient, and wide application range, and can effectively solve the problem of low-frequency broadband high-efficiency sound absorption in the prior art.

Description

Technical Field

[0001] The present invention relates to the technical field of new materials, new structures and their design for noise control, and particularly to a low-frequency broadband sound-absorbing metamaterial structure and a rapid design method thereof. Background Art

[0002] On the one hand, with the rapid development of science and technology, major transportation equipment (such as large aircraft, aircraft carriers, rocket ships, high-speed trains, etc.) is continuously developing towards high speed and light weight, and the resulting noise problems are becoming more prominent. A high-level noise environment not only affects the safety, reliability and comfort of the equipment, but also affects the physical and mental health of people. Seriously, it will cause damage to people's hearing and nerve functions. Therefore, the demand for noise reduction in the development of science and technology is extremely urgent. On the other hand, with the improvement of the quality requirements of human life, the requirements for noise reduction in the environment and products are higher. The noise pollution problems widely existing in industrial production, construction, transportation and social life have become a topic of great concern to society. Therefore, it is crucial to effectively control noise and improve the sound quality of the environment.

[0003] For noise control, it is mainly divided into reducing at the sound source, blocking in the propagation path and protecting at the receiver. Obviously, among the available noise reduction means, sound absorption is a widely used method. Sound-absorbing materials or structures achieve the absorption of sound by dissipating sound energy and are widely used in various enclosed or semi-enclosed spaces. It can be used for sound absorption and noise reduction in the cabins of major transportation equipment, such as high-speed trains, large aircraft, ships, rocket ships, etc.; it can also be used for sound field control in new functional places, such as conference rooms, studios, recording studios, anechoic chambers, large wind tunnels, etc. Traditional sound-absorbing materials or structures include porous fiber materials, porous foam materials and micro-perforated plate structures and have been widely applied. However, these traditional sound-absorbing materials and structures can only effectively absorb sound waves when the thickness exceeds 1 / 4 of the wavelength. Traditional porous fiber materials and porous foam materials can achieve excellent sound absorption performance in a relatively wide frequency band, but generally have problems of inability to bear mechanical loads and poor sound absorption performance in the medium and low frequency ranges. In addition, the micro-perforated plate structure also has poor absorption ability in the low frequency range and cannot achieve broadband absorption of sound waves. All along, due to the long wavelength, low-frequency noise has the characteristics of strong penetration ability and being difficult to be absorbed, making it an urgent problem to be solved in the field of noise control.

[0004] In recent years, the concept of acoustic metamaterials has provided ideas for solving low-frequency noise problems. Sound-absorbing metamaterial structures and their rapid design methods have become a major research focus in the field of sound absorption and noise reduction.

[0005] Among them, the patent titled "A Multi-Unit Coupled Microperforated Plate Low-Frequency Broadband Sound Absorption Structure and Its Design Method" (Publication Number: CN110517659A) describes a structure that achieves a continuous sound absorption bandwidth by providing multiple different microperforated sound absorption units, coupling the low-order and high-order sound absorption peaks of these units. However, the broadband sound absorption coefficient after coupling fluctuates significantly, exhibiting significant attenuation. Furthermore, the high cost of manufacturing the microperforated plates hinders practical application. Furthermore, the design method for this low-frequency broadband sound absorption structure is merely a basic forward design approach for this specific multi-unit coupled microperforated plate low-frequency broadband sound absorption structure. Research is lacking on rapid reverse optimization design methods for sound absorption structures under actual demand conditions, a critical issue that needs to be addressed in practical applications.

[0006] Among them, the patent is titled "Metamaterial Unit and Superstructure Module for Low-Frequency, Broadband, and Efficient Sound Absorption (Publication No.: CN217847433U)." This low-frequency, broadband, and efficient sound absorption superstructure module consists of a metamaterial cavity and an internally disposed impedance-efficient modulated sound absorber, capable of achieving good low-frequency, broadband sound absorption. However, its impedance modulation channel has few adjustable degrees of freedom and a limited modulation range, which often results in a small structural processing size and is difficult to process and prepare. In addition, its impedance modulation sound absorber is not stable and requires additional internal support structures to ensure the stability of the impedance modulation channel structure shape. This results in high manufacturing costs and is not conducive to practical applications.

[0007] Among them, the patent is named Helmholtz resonator and low-frequency broadband sound absorption and noise reduction structure based on it (publication number: CN111105774A). This low-frequency broadband sound absorption and noise reduction structure based on the Helmholtz resonator is composed of many narrow and slender cavities and double-layered small inner tubes. It can achieve low-frequency broadband sound absorption effect. However, in order to achieve low-frequency broadband sound absorption effect, it is often necessary to combine a large number of Helmholtz resonators composed of narrow and slender cavities and double-layered small inner tubes. The narrow and slender cavity and the internal small inner tubes often make processing and preparation difficult, the manufacturing cost is high, and the pollution resistance is poor, which is not conducive to practical application.

[0008] In summary, in actual engineering applications, existing sound-absorbing materials and structures often struggle to achieve low-frequency, broadband sound absorption due to limitations in space, processing techniques, and manufacturing costs. Currently, achieving efficient low-frequency, broadband sound absorption is a pressing challenge facing researchers in the field of noise control. Summary of the Invention

[0009] In view of the above deficiencies in the prior art, the present invention provides a low-frequency broadband sound-absorbing metamaterial structure and a rapid design method. The low-frequency broadband sound-absorbing metamaterial structure has the advantages of low cost, high reliability, low-frequency broadband sound-absorbing performance, multi-degree-of-freedom impedance modulation, self-stabilization, load-bearing capacity, etc. Moreover, its design has the advantages of simple process, rapid and efficient, wide application range, etc., and can effectively solve the problem of low-frequency broadband high-efficiency sound absorption in the prior art.

[0010] To achieve the above object, the present invention provides a low-frequency broadband sound-absorbing metamaterial structure, including an enclosure, a partition, a wave-tuning channel and a self-stabilizing multi-degree-of-freedom sound absorber;

[0011] The enclosure is a cylindrical structure with an open top, and the partition is arranged horizontally and / or vertically and / or vertically and / or obliquely in the enclosure to form at least one acoustic channel in the enclosure;

[0012] The acoustic channel has at least one opening at the top of the enclosure, and the acoustic channel and its corresponding part of the enclosure and / or part of the partition form a wave-tuning channel;

[0013] The self-stabilizing multi-degree-of-freedom sound absorber includes a self-stabilizing sound-absorbing medium and multi-degree-of-freedom wave-guiding holes. The self-stabilizing sound-absorbing medium is filled in the acoustic channel, and the multi-degree-of-freedom wave-guiding holes are arranged on the self-stabilizing sound-absorbing medium.

[0014] In one embodiment, the multi-degree-of-freedom wave-guiding holes are polyhedron structures with multiple size degrees of freedom, and the polyhedron structures include, but are not limited to, cuboids, pyramids, cones, frustums of cones, pyramids, and frustums of pyramids;

[0015] The multi-degree-of-freedom wave-guiding holes have at least one open end, and the open end of the multi-degree-of-freedom wave-guiding holes is located on the corresponding self-stabilizing sound-absorbing medium and is flush with the top of the enclosure.

[0016] In one embodiment, the cross-section of the self-stabilizing multi-degree-of-freedom sound absorber is a continuous plane composed of the self-stabilizing sound-absorbing medium alone everywhere; or

[0017] The cross-section of the self-stabilizing multi-degree-of-freedom sound absorber is a single annular continuous plane composed of the self-stabilizing sound-absorbing medium and the multi-degree-of-freedom wave-guiding holes embedded therein everywhere; or

[0018] A part of the cross-section of the self-stabilizing multi-degree-of-freedom sound absorber is a continuous plane composed of the self-stabilizing sound-absorbing medium alone, and another part of the cross-section of the self-stabilizing multi-degree-of-freedom sound absorber is a single annular continuous plane composed of the self-stabilizing sound-absorbing medium and the multi-degree-of-freedom wave-guiding holes embedded therein.

[0019] In one embodiment, the enclosing panel and the partition are made of a high acoustic reflection plate structure.

[0020] In one embodiment, the acoustic channel is a semi-through acoustic channel or a full-through acoustic channel;

[0021] When the acoustic channel is a semi-through acoustic channel, the acoustic channel is a straight channel, an L-shaped channel or a zigzag channel, and the acoustic channel has an opening at the top of the enclosing panel;

[0022] When the acoustic channel is a full-through acoustic channel, the acoustic channel is a U-shaped channel or a zigzag channel, and the acoustic channel has more than two openings at the top of the enclosing panel.

[0023] In one embodiment, the low-frequency broadband sound-absorbing metamaterial structure further includes a wave-transmitting surface structure, and the wave-transmitting surface structure covers the top of the enclosing panel.

[0024] To achieve the above object, the present invention also provides a rapid design method for the above low-frequency broadband sound-absorbing metamaterial structure, including the following steps:

[0025] Step 1, proposing an acoustic design objective for the low-frequency broadband sound-absorbing metamaterial structure;

[0026] Step 2, specifying a basic configuration of the low-frequency broadband sound-absorbing metamaterial structure;

[0027] Step 3, determining an acoustic performance optimization objective for the low-frequency broadband sound-absorbing metamaterial structure within a specific frequency range;

[0028] Step 4, extracting sensitive parameters that determine the acoustic performance of the low-frequency broadband sound-absorbing metamaterial structure;

[0029] Step 5, setting optimization boundaries for the sensitive parameters;

[0030] Step 6, selecting an optimization algorithm and setting an optimization iteration limit;

[0031] Step 7, implementing integrated optimization iteration to obtain the pre-designed parameter values of the low-frequency broadband sound-absorbing metamaterial structure;

[0032] Step 8, using the pre-designed parameter values to analyze and calculate the acoustic performance of the low-frequency broadband sound-absorbing metamaterial structure;

[0033] Step 9: Judging whether the acoustic performance of the low-frequency broadband sound-absorbing metamaterial structure meets the design objective:

[0034] If so, outputting the pre-designed parameter values to complete the rapid inverse design of the low-frequency broadband sound-absorbing metamaterial structure;

[0035] Otherwise, after adjusting the basic configuration of the low-frequency broadband sound-absorbing metamaterial structure, steps 3 to 9 are performed again.

[0036] In one embodiment, in step 3, the specific frequency range is a single frequency point; or

[0037] the specific frequency range is multiple discrete frequency points; or

[0038] the specific frequency range is a single continuous frequency band range; or

[0039] the specific frequency range is multiple continuous frequency band ranges; or

[0040] the specific frequency range is a combined frequency range composed of discrete frequency points and continuous frequency band ranges.

[0041] In one embodiment, in step 3, the acoustic performance is the absorption coefficient and / or the reflection coefficient and / or the surface impedance and / or the surface impedance ratio and / or the admittance;

[0042] the optimization goal is to optimize the maximum or minimum value of the acoustic performance; or

[0043] the optimization goal is to optimize the average value of the acoustic performance;

[0044] the optimization goal is to optimize the weighted average of the maximum or minimum value and the average value of the acoustic performance.

[0045] In one embodiment, in step 4, sensitive parameters that determine the acoustic performance of the low-frequency broadband sound-absorbing metamaterial structure are extracted by single-parameter scanning or multi-parameter scanning.

[0046] In one embodiment, in step 4, the sensitive parameters are the structural parameters of the wave tuning channel and / or the structural parameters of the multi-degree-of-freedom wave guiding cavity and / or the structural parameters of the wave transmitting protective surface structure and / or the material parameters of the self-stabilizing sound-absorbing medium.

[0047] In one embodiment, in step 5, the process of determining the optimization boundary of the sensitive parameters is as follows:

[0048] The optimization boundary of the sensitive parameters is directly set according to the maximum parameter boundary of the actual structural material; or

[0049] The optimization boundary of the sensitive parameters is obtained by quickly pre-optimizing the boundary screening according to the maximum parameter boundary of the actual structural material; or

[0050] The optimization boundary of the sensitive parameters is obtained by boundary screening according to the influence of the parameters of the actual structural material on the acoustic performance.

[0051] In one of the embodiments, in step 6, the optimization algorithm is a genetic algorithm, an ant colony algorithm, a simulated annealing algorithm, a tabu search algorithm or a particle swarm algorithm.

[0052] Compared with the prior art, the low-frequency broadband sound-absorbing metamaterial structure in the present invention has the following beneficial technical effects:

[0053] 1. The low-frequency broadband sound-absorbing metamaterial structure in the present invention has the advantages of low cost, high reliability, low-frequency broadband sound-absorbing performance, multi-degree-of-freedom impedance modulation, self-stabilization, load-bearing capacity, etc. On the one hand, by designing different structural sizes, wave tuning channels with different equivalent lengths can be formed. On the other hand, through the zigzag design, without increasing the thickness of the metamaterial structure, the effective length of the wave tuning channel can be significantly increased, which is beneficial to the absorption of lower-frequency sound waves.

[0054] 2. The present invention is provided with a self-stabilizing multi-degree-of-freedom sound absorber in the wave tuning channel, which has a multi-degree-of-freedom efficient cooperative modulation effect on the impedance.

[0055] 3. The self-stabilizing multi-degree-of-freedom sound absorber in the present invention has a closed and continuous cross-sectional structure, so it has self-stabilizing performance and does not require additional support structures.

[0056] 4. The multi-degree-of-freedom wave guiding holes in the present invention have multiple size degrees of freedom, and can realize the multi-degree-of-freedom efficient cooperative modulation of the impedance under the condition that the structural size is more in line with the engineering reality.

[0057] 5. The present invention can combine wave tuning channels with different equivalent lengths with self-stabilizing multi-degree-of-freedom sound absorbers with different impedances inside, so that its impedance matches the air, and different high-efficiency absorption peaks can be generated in the low-frequency range on the premise of realizing high-efficiency sound absorption in the medium and high frequencies.

[0058] 6. The present invention can effectively couple different high-efficiency absorption peaks of the metamaterial structure in the low-frequency range through the cooperative coupling effect between the wave tuning channel and the self-stabilizing multi-degree-of-freedom sound absorber, so that the metamaterial structure can achieve high-efficiency sound absorption of sound waves in the low-frequency broadband range.

[0059] Compared with the prior art, the rapid design method of the low-frequency broadband sound-absorbing metamaterial structure in the present invention has the following beneficial technical effects:

[0060] The rapid design method in the present invention has advantages such as a simple process, high efficiency, and a wide range of applications. It can propose acoustic design goals for metamaterial structures according to the requirements of actual engineering applications. By specifying the basic configuration of the low-frequency broadband absorbing metamaterial structure, determining the acoustic performance optimization goals within a specific frequency range, extracting the sensitive parameters that determine the acoustic performance of the low-frequency broadband absorbing metamaterial structure, and setting the parameter optimization boundaries, the optimization iteration efficiency can be significantly improved, and the design speed can be increased. Further, by selecting a suitable optimization algorithm, setting the optimization iteration limit, and continuously integrating optimization iterations, a metamaterial structure that meets the design goals can be obtained, realizing the rapid inverse design of the low-frequency broadband absorbing metamaterial structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0062] Figure 1 It is a three-dimensional perspective schematic diagram of the low-frequency broadband absorbing metamaterial structure in Embodiment 1 of the present invention;

[0063] Figure 2 It is a three-dimensional exploded structure schematic diagram of the low-frequency broadband absorbing metamaterial structure in Embodiment 1 of the present invention;

[0064] Figure 3 It is a three-dimensional perspective schematic diagram of the low-frequency broadband absorbing metamaterial structure in Embodiment 1 of the present invention when it has a triangular perforated plate as the wave-transmitting protective surface structure;

[0065] Figure 4 It is a three-dimensional perspective schematic diagram of the low-frequency broadband absorbing metamaterial structure in Embodiment 1 of the present invention when it has a circular perforated plate as the wave-transmitting protective surface structure;

[0066] Figure 5 It is a three-dimensional perspective schematic diagram of the low-frequency broadband absorbing metamaterial structure in Embodiment 1 of the present invention when it has a strip-shaped grid plate as the wave-transmitting protective surface structure;

[0067] Figure 6 It is a three-dimensional perspective schematic diagram of the low-frequency broadband absorbing metamaterial structure in Embodiment 1 of the present invention when it has a mesh-shaped grid plate as the wave-transmitting protective surface structure;

[0068] Figure 7 It is a three-dimensional perspective schematic diagram of the wave-tuning channel in Embodiment 1 of the present invention when it is a linear semi-penetrating channel;

[0069] Figure 83D perspective schematic diagram when the wave - tuning channel is an L - shaped semi - through - channel in Embodiment 1 of the present invention;

[0070] Figure 9 3D perspective schematic diagram when the wave - tuning channel is a zigzag - shaped semi - through - channel in Embodiment 1 of the present invention;

[0071] Figure 10 3D perspective schematic diagram when the wave - tuning channel is a U - shaped fully - through - channel in Embodiment 1 of the present invention;

[0072] Figure 11 3D perspective schematic diagram when the wave - tuning channel is a zigzag - shaped fully - through - channel in Embodiment 1 of the present invention;

[0073] Figure 12 3D perspective schematic diagram of the first implementation mode of the self - stabilizing multi - degree - of - freedom sound absorber in Embodiment 1 of the present invention;

[0074] Figure 13 3D perspective schematic diagram of the second implementation mode of the self - stabilizing multi - degree - of - freedom sound absorber in Embodiment 1 of the present invention;

[0075] Figure 14 3D perspective schematic diagram of the third implementation mode of the self - stabilizing multi - degree - of - freedom sound absorber in Embodiment 1 of the present invention;

[0076] Figure 15 Flow chart of the rapid design method for the low - frequency broadband sound - absorbing metamaterial structure in Embodiment 2 of the present invention;

[0077] Figure 16 3D structure schematic diagram of the low - frequency broadband sound - absorbing metamaterial structure in the example of Embodiment 2 of the present invention;

[0078] Figure 17 3D exploded perspective schematic diagram of the low - frequency broadband sound - absorbing metamaterial structure in the example of Embodiment 2 of the present invention;

[0079] Figure 18 Flow chart of the rapid design method for the low - frequency broadband sound - absorbing metamaterial structure in the example of Embodiment 2 of the present invention;

[0080] Figure 19 3D perspective schematic diagram of the structural dimensions of the wave - tuning channel in the example of Embodiment 2 of the present invention;

[0081] Figure 20 3D perspective schematic diagram of the structural dimensions of the self - stabilizing multi - degree - of - freedom sound absorber in the example of Embodiment 2 of the present invention;

[0082] Figure 21 3D structure schematic diagram of the structural dimensions of the wave - transmitting protective surface structure in the example of Embodiment 2 of the present invention;

[0083] Figure 22Schematic diagram of the sound absorption coefficient of the low-frequency broadband metamaterial structure rapidly designed in Example 2 of the present invention.

[0084] Reference numerals in the drawings: 1, self-stabilizing multi-degree-of-freedom sound absorber; 1a, multi-degree-of-freedom wave-guiding holes; 1b, self-stabilizing sound-absorbing medium; 2, wave-adjusting channel; 2a, enclosure plate; 2b, partition plate; 2c, acoustic channel; 3, wave-transmitting protective surface structure.

[0085] The realization, functional features and advantages of the object of the present invention will be further described with reference to the embodiments and the accompanying drawings. Detailed implementation manners

[0086] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts shall fall within the protection scope of the present invention.

[0087] It should be noted that all directional indications (such as up, down, left, right, front, back...) in the embodiments of the present invention are only used to explain the relative positional relationship and movement conditions between components in a specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indications will also change accordingly.

[0088] In addition, the descriptions such as "first" and "second" in the present invention are only for descriptive purposes, and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present invention, "a plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0089] In the present invention, unless otherwise clearly defined and limited, the terms "connection", "fixation", etc. shall be understood in a broad sense. For example, "fixation" may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection, an electrical connection, a physical connection or a wireless communication connection; it may be directly connected, or indirectly connected through an intermediate medium, and may be the internal connection of two components or the interaction relationship between two components, unless otherwise clearly limited. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0090] 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 ability of those of ordinary skill in the art to implement. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0091] Embodiment 1

[0092] As Figure 1 、 Figure 2 shown in the figure, a low-frequency broadband sound-absorbing metamaterial structure disclosed in this embodiment mainly includes a wave-tuning channel 2 and a self-stabilizing multi-degree-of-freedom sound absorber 1.

[0093] The wave-tuning channel 2 is composed of a surrounding plate 2a, a partition plate 2b, and an acoustic channel 2c. Specifically, the surrounding plate 2a is a hollow cylindrical structure with an open top. The partition plate 2b is arranged horizontally and / or vertically and / or vertically and / or obliquely inside the surrounding plate 2a. The number of partition plates 2b is multiple, and the shapes of the partition plates 2b are not the same. When connecting, the partition plate 2b can be connected to the inner wall of the surrounding plate 2a or the partition plates 2b can be connected to each other. Thus, the internal space of the surrounding plate 2a can be divided into several acoustic channels 2c with different shapes, lengths, and cross-sectional areas by the partition plate 2b, and each acoustic channel 2c has at least one opening at the top of the surrounding plate 2a. And each acoustic channel 2c and the part of the surrounding plate 2a and / or part of the partition plate 2b enclosing the acoustic channel 2c form a wave-tuning channel 2. Among them, rigid connection methods such as gluing, nailing, welding, and / or integral molding can be used between the surrounding plate 2a and the partition plate 2b and between the partition plates 2b.

[0094] The surrounding plate 2a and multiple partition plates 2b with different structural dimensions are connected to form wave-tuning channels 2 with different equivalent lengths. The formed wave-tuning channels 2 with different structural dimensions, on the one hand, can form a gradient-varying effective wave-tuning length through different structural dimension designs; on the other hand, through the zigzag design, the equivalent length of the wave-tuning channel 2 can be significantly increased without increasing the thickness dimension (along the z-axis direction) of the metamaterial structure, which is beneficial to the absorption of lower-frequency sound waves.

[0095] The wave-tuning channel 2 needs to cooperate with the self-stabilizing multi-degree-of-freedom sound absorber 1 arranged inside it to achieve efficient absorption of sound waves. Specifically, the number of self-stabilizing multi-degree-of-freedom sound absorbers 1 corresponds one-to-one with the wave-tuning channels 2. The self-stabilizing multi-degree-of-freedom sound absorber 1 is composed of multi-degree-of-freedom wave-guiding holes 1a and self-stabilizing sound-absorbing media 1b. The self-stabilizing sound-absorbing media 1b are filled in the acoustic channels 2c of the corresponding wave-tuning channels 2, and the multi-degree-of-freedom wave-guiding holes 1a are arranged on the corresponding self-stabilizing sound-absorbing media 1b.

[0096] The self-stabilizing multi-degree-of-freedom sound absorber 1 has a closed and continuous cross-sectional structure, so it has self-stabilizing performance and does not require additional support structures. In addition, the multi-degree-of-freedom wave-guiding holes 1a in the self-stabilizing multi-degree-of-freedom sound absorber 1 have multiple degrees of freedom, and can achieve efficient cooperative modulation of impedance in multiple degrees of freedom under the condition that the structural dimensions are more in line with engineering practice. The wave-regulating channels 2 with different equivalent lengths are combined with the self-stabilizing multi-degree-of-freedom sound absorber 1 with different impedances inside, so that its impedance matches the air, and different high-efficiency absorption peaks can be generated in the low-frequency range on the premise of achieving high-efficiency sound absorption in the medium and high frequencies. Further, by utilizing the cooperative coupling effect between the wave-regulating channel 2 and the self-stabilizing multi-degree-of-freedom sound absorber 1 arranged inside it, through optimized design, the different high-efficiency absorption peaks of the metamaterial structure in the low-frequency range are effectively coupled, so that the metamaterial structure can achieve high-efficiency absorption of sound waves in the low-frequency broadband range.

[0097] Based on the wave-regulating channel 2 and the self-stabilizing multi-degree-of-freedom sound absorber 1, the low-frequency broadband sound-absorbing metamaterial structure in this embodiment can also be provided with a wave-transmitting protective surface structure 3, and the wave-transmitting protective surface structure 3 can cover the top of the enclosure 2a by means of hinging, nailing, etc. The wave-transmitting protective surface structure 3 can not only ensure that sound waves can enter the low-frequency broadband sound-absorbing metamaterial structure normally, but also play a role in fixing and protecting the built-in self-stabilizing multi-degree-of-freedom sound absorber 1. In addition, by changing the effective wave-transmitting area of the wave-transmitting protective surface structure 3, the acoustic performance of the low-frequency broadband sound-absorbing metamaterial structure in the low-frequency and high-frequency ranges can be adjusted to a certain extent, and the design freedom of the low-frequency broadband sound-absorbing metamaterial structure can be increased. In the specific implementation process, the selected wave-transmitting protective surface structure 3 is an opening structure, a slotted structure, a grid structure, and can even be a common wire mesh, fabric, etc. For example, the wave-transmitting protective surface structure 3 can be Figure 3 the opening plate with triangular holes shown, or Figure 4 the opening plate with circular holes shown, or Figure 5 the strip-shaped grid plate shown or Figure 6 the mesh-shaped grid plate shown.

[0098] In this embodiment, the acoustic channel 2c surrounded by the partition 2b and / or the enclosure 2a can be a semi-through acoustic channel 2c or a full-through acoustic channel 2c.

[0099] When the acoustic channel 2c is a semi-through acoustic channel 2c, the acoustic channel 2c is a straight channel as shown in Figure 7 , an L-shaped channel with a single bend as shown in Figure 8 or an L-shaped channel as shown in Figure 9The shown multi-bent zigzag channel, the acoustic channel 2c has an opening at the top of the baffle 2a and only has one opening. That is, the characteristics of the wave-tuning channel 2 under the semi-through acoustic channel 2c are: one end of the wave-tuning channel 2 is open, and the other end is physically closed by the baffle 2a or the partition 2b. Sound waves can only enter from the open end, and sound waves cannot transmit through the closed end. In this embodiment, through the bending design, the wave-tuning channel 2 forms an L-shaped semi-closed channel with one bend or a zigzag semi-closed channel with multiple bends, which can significantly increase the equivalent length of the wave-tuning channel 2 without increasing the thickness dimension (along the z-axis direction) of the low-frequency broadband sound-absorbing metamaterial structure, and realize the absorption of lower-frequency sound waves.

[0100] When the acoustic channel 2c is a fully-through acoustic channel 2c, the acoustic channel 2c is a U-shaped channel as shown in Figure 10 or a zigzag channel as shown in Figure 11 The acoustic channel 2c has more than two openings at the top of the baffle 2a. That is, the characteristics of the wave-tuning channel 2 under the fully-through acoustic channel 2c are: both ends or multiple ends of the wave-tuning channel 2 are open, and sound waves can enter the wave-tuning channel 2 simultaneously from two or more open ends. In the middle part of the wave-tuning channel 2, due to the interaction of two or more incident sound waves, an acoustic barrier that isolates the propagation of sound waves is formed, which is equivalent to two or more semi-through wave-tuning channels 2, making the preparation cost lower and the processing technology simpler. Similarly, in this embodiment, through the bending design, the wave-tuning channel 2 can significantly increase the equivalent length of the wave-tuning channel 2 without increasing the thickness dimension (along the z-axis direction) of the low-frequency broadband sound-absorbing metamaterial structure, and realize the absorption of lower-frequency sound waves.

[0101] In this embodiment, the shapes and sizes of the multi-degree-of-freedom wave-guiding holes 1a on the self-stabilizing multi-degree-of-freedom sound absorber 1 in different wave-tuning channels 2 can be the same or different. Specifically, the shape of the multi-degree-of-freedom wave-guiding holes 1a embedded in the self-stabilizing multi-degree-of-freedom sound absorber 1 is a polyhedron structure, such as a frustum, a circular frustum, an elliptical frustum, a cuboid, a pyramid, etc., or can be a cone, a pyramid, etc. For example Figure 12 The shown is the multi-degree-of-freedom wave-guiding hole 1a in the shape of an elliptical frustum. The multi-degree-of-freedom wave-guiding hole 1a has at least one open end, and the open end of the multi-degree-of-freedom wave-guiding hole 1a is located on the corresponding self-stabilizing sound-absorbing medium 1b and is flush with the top of the baffle 2a. These shapes of multi-degree-of-freedom wave-guiding holes 1a all have multiple degrees of freedom in size, and a wide range of adjustment of the shape and size of the multi-degree-of-freedom wave-guiding hole 1a can be realized by simultaneously adjusting multiple degrees of freedom in size.

[0102] In addition, one or more multi-degree-of-freedom wave-guiding holes 1a can be embedded in one self-stabilizing multi-degree-of-freedom sound absorber 1. By embedding multiple multi-degree-of-freedom wave-guiding holes 1a, a larger range of adjustment can be realized. For example Figure 13Shown is an implementation of a self-stabilizing multi-degree-of-freedom sound absorber 1 with two multi-degree-of-freedom wave-guiding cavities 1a embedded therein. One of the multi-degree-of-freedom wave-guiding cavities 1a has a triangular prism structure, and the other has a pentagonal prism structure. For another example Figure 14 Also shown is an implementation of a self-stabilizing multi-degree-of-freedom sound absorber 1 with two multi-degree-of-freedom wave-guiding cavities 1a embedded therein. One of the multi-degree-of-freedom wave-guiding cavities 1a has a hexagonal prism structure, and the other has a frustum of a cone structure.

[0103] In addition, the self-stabilizing multi-degree-of-freedom sound absorber 1 has a closed and continuous cross-sectional structure, so it has self-stabilizing performance and does not require an additional support structure. Specifically, the cross-section of the self-stabilizing multi-degree-of-freedom sound absorber 1 is everywhere a continuous plane composed of the self-stabilizing sound-absorbing medium 1b alone; or the cross-section of the self-stabilizing multi-degree-of-freedom sound absorber 1 is everywhere a single annular continuous plane composed of the self-stabilizing sound-absorbing medium 1b and the multi-degree-of-freedom wave-guiding cavities 1a embedded therein; or a part of the cross-section of the self-stabilizing multi-degree-of-freedom sound absorber 1 is a continuous plane composed of the self-stabilizing sound-absorbing medium 1b alone, and another part of the cross-section of the self-stabilizing multi-degree-of-freedom sound absorber 1 is a single annular continuous plane composed of the self-stabilizing sound-absorbing medium 1b and the multi-degree-of-freedom wave-guiding cavities 1a embedded therein. The self-stabilizing sound-absorbing medium 1b has an absorption effect on sound waves. Cooperating with the embedded multi-degree-of-freedom wave-guiding cavities 1a, it can achieve multi-degree-of-freedom and highly efficient collaborative modulation of the overall impedance of the self-stabilizing multi-degree-of-freedom sound absorber 1. In addition, the introduced multi-degree-of-freedom wave-guiding cavities 1a can make the sound waves in the low-frequency band better absorbed, and can make the surface impedance of the self-stabilizing multi-degree-of-freedom sound absorber 1 match the air in the low-frequency broadband range, realizing the low-frequency broadband absorption effect on sound waves.

[0104] In this embodiment, the enclosure 2a and the partition 2b are made of a high sound wave reflection plate structure, which can be a metal plate, a plastic plate, a hard fiber board, a plywood board, a gypsum board, a synthetic resin board, a composite material board, or a tempered glass board, etc.

[0105] Embodiment 2

[0106] Based on the low-frequency broadband sound-absorbing metamaterial structure in Embodiment 1, this embodiment discloses a corresponding design method for the rapid design of a low-frequency broadband sound-absorbing metamaterial structure. Refer to Figure 15 , and this design method specifically includes the following steps:

[0107] Step 1, propose the acoustic design goal of the low-frequency broadband sound-absorbing metamaterial structure: According to the actual engineering requirements, propose the specific indexes of the sound absorption performance that the metamaterial structure should achieve within the target frequency band range as its acoustic design goal;

[0108] Step 2, specifying the basic configuration of the low-frequency broadband sound-absorbing metamaterial structure: According to the acoustic design objectives proposed in Step 1 and combined with the requirements of the structural material properties of the metamaterial structure to be designed in actual engineering, specify the basic configuration of the low-frequency broadband sound-absorbing metamaterial structure;

[0109] Step 3, determining the optimization objectives for the acoustic performance of the low-frequency broadband sound-absorbing metamaterial structure within a specific frequency range: According to the acoustic design objectives proposed in Step 1 and combined with the basic configuration of the low-frequency broadband sound-absorbing metamaterial structure specified in Step 2, determine the acoustic performance of the low-frequency broadband sound-absorbing metamaterial structure within a specific frequency range as the optimization objective;

[0110] Step 4, extracting the sensitive parameters that determine the acoustic performance of the low-frequency broadband sound-absorbing metamaterial structure: By analyzing the influence of the specific structural material parameters of the low-frequency broadband sound-absorbing metamaterial structure specified in Step 2 on the acoustic performance optimization objectives determined in Step 3, extract the parameters that have a greater impact on the acoustic performance optimization objectives as sensitive parameters;

[0111] Step 5, setting the optimization boundaries of the sensitive parameters: According to the sensitive parameters extracted in Step 4 and combined with the actual situation, determine the maximum value range of each sensitive parameter. Further, analyze the sensitive parameters that may have an interactive effect and refine their value ranges to obtain the correct value ranges of all sensitive parameters, which can be directly used as the parameter optimization boundaries, or the value ranges can be further simplified according to the influence law of the sensitive parameters on the acoustic performance, and the simplified value ranges are used as the parameter optimization boundaries to improve the optimization efficiency;

[0112] Step 6, selecting an optimization algorithm and setting the optimization iteration limit: According to the optimization objectives of the low-frequency broadband sound-absorbing metamaterial structure set in Step 3 and the optimization boundaries of the sensitive parameters set in Step 5, select a suitable and efficient optimization algorithm, and according to the optimization experience and combined with the actual situation, set the corresponding optimization iteration limit;

[0113] Step 7, using the optimization algorithm selected in Step 6 to perform integrated optimization iteration on the low-frequency broadband sound-absorbing metamaterial structure specified in Step 2 to obtain the pre-designed parameter values of the low-frequency broadband sound-absorbing metamaterial structure: Perform integrated optimization on all or part of the sensitive parameters among the specific structural material parameters of the low-frequency broadband sound-absorbing metamaterial structure, and through continuous optimization iteration, obtain the pre-designed parameter values of the optimized sensitive parameters;

[0114] Step 8, using the pre-designed parameter values to analyze and calculate the acoustic performance of the low-frequency broadband sound-absorbing metamaterial structure: Substitute the pre-designed parameter values obtained in Step 7 into the given low-frequency broadband sound-absorbing metamaterial structure to further analyze and calculate the acoustic performance of the low-frequency broadband sound-absorbing metamaterial structure;

[0115] Step 9, determine whether the acoustic performance of the low-frequency broadband sound-absorbing metamaterial structure meets the design objectives:

[0116] If so, output the values of the pre-designed parameters to complete the rapid inverse design of the low-frequency broadband sound-absorbing metamaterial structure;

[0117] Otherwise, after adjusting the basic configuration of the low-frequency broadband sound-absorbing metamaterial structure, perform Steps 3 to 9 again for re-optimization and iterative design.

[0118] It should be noted that in the specific implementation process, Step 2 is carried out after Step 1; Steps 3, 4, and 5 can be carried out in parallel after Step 2. Step 5 is carried out after Step 4, Step 6 is carried out after Steps 3 and 5, Step 7 is carried out after Step 6, Step 8 is carried out after Step 7, and Step 9 is carried out after Step 8.

[0119] In the specific implementation process of Step 3, different frequency ranges can be set for the specific frequency range according to actual needs. For example, the specific frequency range can be directly set as a single frequency point or a single continuous frequency band range, or it can be set as multiple discrete frequency points or multiple continuous frequency band ranges, or it can also be set as a combined frequency range composed of discrete frequency points and continuous frequency band ranges.

[0120] In the specific implementation process of Step 3, the determined acoustic performance can be selected as one, multiple, or all of the absorption coefficient, reflection coefficient, surface impedance, surface impedance ratio, and admittance. The optimization objective can be set to optimize the maximum or minimum value of the selected acoustic performance, or to optimize the average value of the selected acoustic performance, or it can also be set to optimize the weighted average of the maximum and minimum values of the selected acoustic performance.

[0121] In the specific implementation process of Step 4, sensitive parameters that determine the acoustic performance of the low-frequency broadband sound-absorbing metamaterial structure can be extracted through single-parameter scanning or multi-parameter scanning. The sensitive parameters can be one, multiple, or all of the structural parameters of the wave tuning channel 2, the structural parameters of the multi-degree-of-freedom wave guiding cavity, the structural parameters of the wave-transmitting protective surface structure 3, and the material parameters of the self-stabilizing sound-absorbing medium 1b.

[0122] In the specific implementation process of Step 5, the optimization boundary of the sensitive parameters can be directly set according to the maximum parameter boundary of the actual structural material, or the optimization boundary of the sensitive parameters can be obtained by quickly pre-optimizing the boundary screening according to the maximum parameter boundary of the actual structural material, or the optimization boundary of the sensitive parameters can be obtained by boundary screening according to the influence of the parameters of the actual structural material on the acoustic performance.

[0123] In the specific implementation process of step 6, the optimization algorithm selected can be a genetic algorithm, an ant colony algorithm, a simulated annealing algorithm, a tabu search algorithm, or a particle swarm algorithm.

[0124] The following combines specific examples to elaborate in detail on the rapid design method for the low-frequency broadband sound-absorbing metamaterial structure in this embodiment.

[0125] Refer to Figures 16 to 18 , Figure 16 which is the three-dimensional structure schematic diagram of the low-frequency broadband sound-absorbing metamaterial structure in this example. Figure 17 is the three-dimensional exploded perspective schematic diagram of the low-frequency broadband sound-absorbing metamaterial structure, which includes three wave-tuning channels and the corresponding three self-stabilizing multi-degree-of-freedom sound-absorbing bodies 1, as well as a wave-transmitting protective surface structure 3. Figure 18 is the flow chart of the rapid design method for the low-frequency broadband sound-absorbing metamaterial structure.

[0126] Set the actual engineering requirements as follows: On the premise that the structural thickness dimension (along the z-axis direction) does not exceed 100 mm, design a metamaterial structure with low-frequency broadband sound-absorbing performance, which can achieve efficient absorption of sound waves above 300 Hz, and this structure has a certain stiffness and can bear the load. For the above actual engineering requirements, carry out the rapid design of the corresponding low-frequency broadband sound-absorbing metamaterial structure, and the specific steps are as follows:

[0127] Step 1, propose the acoustic design goal of the low-frequency broadband sound-absorbing metamaterial structure: According to the actual engineering requirements, propose the specific indicators of the sound-absorbing performance that the low-frequency broadband sound-absorbing metamaterial structure should achieve within the target frequency band range as its acoustic design goal; the acoustic design goal of the metamaterial structure that can be proposed in this embodiment is: On the premise that the thickness dimension (along the z-axis direction) of the low-frequency broadband sound-absorbing metamaterial structure does not exceed 100 mm, the sound absorption coefficient is above 0.8 within the low-frequency broadband range of 300 Hz to 20,000 Hz;

[0128] Step 2, give the basic configuration of the low-frequency broadband sound-absorbing metamaterial structure: According to the acoustic design goal proposed in step 1, combined with the requirements of the actual project for the structural material properties of the metamaterial structure, give the basic configuration of the low-frequency broadband sound-absorbing metamaterial structure; the basic configuration of the low-frequency broadband sound-absorbing metamaterial structure given in this embodiment is as Figure 16 and Figure 17 shown. The low-frequency broadband sound-absorbing metamaterial structure includes a linear wave-tuning channel, two L-shaped wave-tuning channels, the corresponding three self-stabilizing multi-degree-of-freedom sound-absorbing bodies 1 each with a multi-degree-of-freedom wave-guiding hole 1a in the shape of an embedded quadrangular frustum, and a wave-transmitting protective surface structure 3 in the shape of a grid; preferably, the upper and lower end faces of the multi-degree-of-freedom wave-guiding hole 1a in the shape of a quadrangular frustum are both rectangles, and the centers of the rectangles are coaxial; the grid holes of the wave-transmitting protective surface structure 3 in the shape of a grid are selected as square holes;

[0129] Step 3, determine the optimization objective of the acoustic performance of the metamaterial structure within a specific frequency range: According to the acoustic design objective proposed in Step 1 and combined with the basic configuration of the low-frequency broadband sound-absorbing metamaterial structure given in Step 2, determine that the maximum value of the minimum sound absorption coefficient of the low-frequency broadband sound-absorbing metamaterial structure within the range of 300 Hz to 20,000 Hz is taken as the optimization objective;

[0130] Step 4, extract the sensitive parameters that determine the acoustic performance of the low-frequency broadband sound-absorbing metamaterial structure: By analyzing the influence of the specific structural material parameters of the low-frequency broadband sound-absorbing metamaterial structure given in Step 2 on the acoustic performance optimization objective (the minimum sound absorption coefficient) determined in Step 3, extract the parameters that have a greater impact on the acoustic performance optimization objective as its sensitive parameters; Refer to Figures 19 to 21 , Figure 19 The structural parameters of the wave-tuning channel 2 in this example are identified. Among them, h1, h2, and h3 are the heights of each wave-tuning channel 2, and w1, w2, w3, and w4 together determine the length and width of each wave-tuning channel 2, and d1 is the thickness of the enclosing plate 2a and the partition plate 2b of each wave-tuning channel 2; Figure 20 The structural parameters of a self-stabilizing multi-degree-of-freedom sound absorber 1 in this example are identified (here, one of the self-stabilizing multi-degree-of-freedom sound absorbers 1 is taken as an example for identification). Among them, l1 is the height of the multi-degree-of-freedom wave-guiding hole 1a, and u1, u2, u3, and u4 are the lengths and widths of the upper and lower end faces of the multi-degree-of-freedom wave-guiding hole 1a respectively; Figure 21 The structural parameters of the wave-transmitting protective surface structure 3 are identified. Among them, d2 is the thickness of the wave-transmitting protective surface structure 3, m is the side length of the grid holes in the wave-transmitting protective surface structure 3, and d3 is the width of the grid; In this embodiment, through the method of single-parameter scanning, the extracted sensitive parameters include the structural parameters h1, h2, h3, w1, w2, w3, w4 of the wave-tuning channel 2, the structural parameters l1, u1, u2, u3, u4,... of the multi-degree-of-freedom wave-guiding hole 1a of the self-stabilizing multi-degree-of-freedom sound absorber 1 (it should be noted that "..." represents the omitted structural parameters of the multi-degree-of-freedom wave-guiding holes 1a of the two self-stabilizing multi-degree-of-freedom sound absorbers 1), the number n and the side length m of the grid holes in the wave-transmitting protective surface structure 3, and the acoustic material parameters of the self-stabilizing sound-absorbing medium 1b;

[0131] Step 5, set the parameter optimization boundary: According to the sensitive parameters extracted in Step 4 and combined with the actual situation, determine the maximum value range of each sensitive parameter; further, analyze the sensitive parameters that may have an interaction effect, and further refine their value ranges to obtain the correct value ranges of all sensitive parameters, which are used as the parameter optimization boundary; in this embodiment, the optimization boundary of the structural parameters of the wave tuning channel 2 should satisfy that the thickness dimension (along the z-axis direction) does not exceed 100 mm and the mutual position constraint limitations (such as 100 mm ≥ h1 > h2 > h3, w1 - 3*d1 > w3, w2 - 3*d1 > w4); for the structural parameters l1, u1, u2, u3, u4,... of the multi-degree-of-freedom wave guiding hole 1a, they should satisfy the structural dimension limitations of the corresponding wave tuning channel 2 (such as h1 ≥ l1, w2 - 2*d1 > u1, w3 > u2, w2 - 2*d1 > u3, w3 > u4); the number n and side length m of the grid holes in the wave-transmitting protective surface structure 3 should satisfy the perforation rate limitation of the wave-transmitting protective surface structure 3 (the perforation rate is (m*m*n) / (w1*w2)); the acoustic material parameters of the self-stabilizing sound-absorbing medium 1b should satisfy the technical limitations achievable in actual engineering requirements;

[0132] Step 6, select an optimization algorithm and set the optimization iteration limit: According to the low-frequency broadband sound-absorbing metamaterial structure optimization goal set in Step 3 and the sensitive parameter optimization boundary set in Step 5, select the genetic algorithm for optimization, and according to the optimization experience and combined with the actual situation, set the corresponding optimization iteration limit to 200 times;

[0133] Step 7, use the optimization algorithm selected in Step 6 to perform integrated optimization iteration on the low-frequency broadband sound-absorbing metamaterial structure given in Step 2 to obtain the pre-designed parameter values of the metamaterial structure: Perform integrated optimization on some of the sensitive parameters in the specific structural material parameters of the low-frequency broadband metamaterial structure, and through continuous optimization iteration, obtain the pre-designed parameter values of the optimized sensitive parameters;

[0134] Step 8, use the pre-designed parameter values to analyze and calculate the acoustic performance of the low-frequency broadband sound-absorbing metamaterial structure: Substitute the pre-designed parameter values obtained in Step 7 into the given low-frequency broadband sound-absorbing metamaterial structure, and further analyze and calculate the minimum sound absorption coefficient of the low-frequency broadband sound-absorbing metamaterial structure in the frequency range of 300 Hz to 20000 Hz;

[0135] Step 9: Determine whether the acoustic performance of the low-frequency broadband sound-absorbing metamaterial structure meets the design objectives. If so, output the values of the pre-designed parameters to complete the rapid inverse design of the low-frequency broadband sound-absorbing metamaterial structure. Otherwise, the basic configuration of the metamaterial structure can be adjusted by adjusting the number and structural forms of the wave-tuning channels 2 and multi-degree-of-freedom wave-guiding cavities 1a in the given low-frequency broadband sound-absorbing metamaterial structure, and then repeat Steps 3 to 9 after adjustment to re-optimize and iterate the design.

[0136] In this example, a low-frequency broadband sound-absorbing metamaterial structure that meets the actual engineering requirements is obtained through the rapid optimization design method. The basic structural form of the designed low-frequency broadband sound-absorbing metamaterial structure is as Figure 16 shown. The thickness dimension (along the z-axis direction) of the metamaterial structure is 100 mm, the length w1 and the broadband w2 are both 50 mm, the thickness d1 of the enclosure plate 2a and the partition plate 2b is 1.5 mm, and the thickness d2 of the wave-transmitting surface structure 3 is 1.5 mm. Overall, the designed low-frequency broadband sound-absorbing metamaterial structure has good load-bearing capacity and meets the load-bearing requirements of the actual design. This metamaterial structure can achieve efficient sound absorption of sound waves in the frequency range of 300 Hz to 20,000 Hz, and the sound absorption coefficient is above 0.8 in the frequency range of 300 Hz.

[0137] The results of the above example show that: by using the wave-tuning channels 2 with different equivalent lengths and the built-in self-stabilizing multi-degree-of-freedom sound absorber 1 in the present invention, and further cooperating with the wave-transmitting surface structure 3, the constructed low-frequency broadband sound-absorbing metamaterial structure can achieve impedance matching with air in the low-frequency broadband range, realize controlling large wavelengths with small sizes, and have good sound absorption effects in the low-frequency broadband range. Moreover, the low-frequency broadband metamaterial structure of the present invention has the advantages of simple process, light and thin structure, self-stabilization, load-bearing capacity, and multi-degree-of-freedom adjustment, and is suitable for large-scale processing applications. In addition, the rapid design method for the low-frequency broadband sound-absorbing metamaterial structure provided by the present invention can, according to the actual engineering requirements, use the optimization algorithm to quickly design a low-frequency broadband sound-absorbing metamaterial structure that meets the requirements through simple and efficient iterative optimization.

[0138] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structural transformation made under the inventive concept of the present invention by using the content of the specification and drawings of the present invention, or directly / indirectly applied in other related technical fields, is included in the patent protection scope of the present invention.

Claims

1. A rapid design method for a low-frequency broadband sound-absorbing metamaterial structure, characterized in that The low-frequency broadband sound-absorbing metamaterial structure includes an enclosure, a partition, a wave-tuning channel, and a self-stabilizing multi-degree-of-freedom sound absorber; the enclosure is a cylindrical structure with an open top, and the partition is arranged horizontally and / or longitudinally and / or vertically and / or obliquely inside the enclosure to form at least one acoustic channel inside the enclosure; The acoustic channel has at least one opening at the top of the enclosure, and the acoustic channel, its corresponding part of the enclosure, and / or part of the partition form a wave-tuning channel; the self-stabilizing multi-degree-of-freedom sound absorber includes a self-stabilizing sound-absorbing medium and multi-degree-of-freedom wave-guiding holes, the self-stabilizing sound-absorbing medium is filled in the acoustic channel, and the multi-degree-of-freedom wave-guiding holes are arranged on the self-stabilizing sound-absorbing medium; The method includes the following steps: Step 1, propose the acoustic design objective of the low-frequency broadband sound-absorbing metamaterial structure; Step 2, specify the basic configuration of the low-frequency broadband sound-absorbing metamaterial structure; Step 3, determine the acoustic performance optimization objective of the low-frequency broadband sound-absorbing metamaterial structure within a specific frequency range; Step 4, extract the sensitive parameters that determine the acoustic performance of the low-frequency broadband sound-absorbing metamaterial structure; Step 5, set the optimization boundaries of the sensitive parameters; Step 6, select an optimization algorithm and set the optimization iteration limit; Step 7, perform integrated optimization iteration to obtain the pre-designed parameter values of the low-frequency broadband sound-absorbing metamaterial structure; Step 8, use the pre-designed parameter values to analyze and calculate the acoustic performance of the low-frequency broadband sound-absorbing metamaterial structure; Step 9: Judge whether the acoustic performance of the low-frequency broadband sound-absorbing metamaterial structure meets the design objective: If so, output the pre-designed parameter values and complete the rapid inverse design of the low-frequency broadband sound-absorbing metamaterial structure; Otherwise, after adjusting the basic configuration of the low-frequency broadband sound-absorbing metamaterial structure, perform steps 3 to 9 again.

2. The rapid design method of the low-frequency broadband sound-absorbing metamaterial structure according to claim 1, characterized in that In step 3, the specific frequency range is a single frequency point; or The specific frequency range is multiple discrete frequency points; or The specific frequency range is a single continuous frequency band range; or The specific frequency range is multiple continuous frequency band ranges; or The specific frequency range is a combined frequency range composed of discrete frequency points and continuous frequency band ranges.

3. The rapid design method of the low-frequency broadband sound-absorbing metamaterial structure according to claim 1, characterized in that, In step 3, the acoustic performance is the absorption coefficient and / or reflection coefficient and / or surface impedance and / or surface impedance ratio and / or admittance; The optimization objective is to optimize the maximum or minimum value of the acoustic performance; or The optimization objective is to optimize the average value of the acoustic performance; The optimization objective is to optimize the weighted average of the maximum or minimum value and the average value of the acoustic performance.

4. The rapid design method of the low-frequency broadband sound-absorbing metamaterial structure according to claim 1, characterized in that, In step 4, the sensitive parameters that determine the acoustic performance of the low-frequency broadband sound-absorbing metamaterial structure are extracted through single-parameter scanning or multi-parameter scanning.

5. The rapid design method of the low-frequency broadband sound-absorbing metamaterial structure according to claim 1, characterized in that In step 4, the sensitive parameters are the structural parameters of the wave-tuning channel and / or the structural parameters of the multi-degree-of-freedom wave-guiding holes and / or the structural parameters of the wave-transmitting protective surface structure and / or the material parameters of the self-stabilizing sound-absorbing medium.

6. The rapid design method of the low-frequency broadband sound-absorbing metamaterial structure according to claim 1, characterized in that In step 5, the process of determining the optimization boundaries of the sensitive parameters is as follows: The optimization boundaries of the sensitive parameters are directly set according to the maximum parameter boundaries of the actual structural materials; or Performing rapid pre-optimization boundary screening based on the maximum parameter boundary of the actual structural material to obtain the optimization boundary of the sensitive parameter; or Performing boundary screening based on the influence of the parameters of the actual structural material on the acoustic performance to obtain the optimization boundary of the sensitive parameter.

7. The rapid design method of the low-frequency broadband sound-absorbing metamaterial structure according to claim 1, characterized in that In step 6, the optimization algorithm is a genetic algorithm, an ant colony algorithm, a simulated annealing algorithm, a tabu search algorithm or a particle swarm algorithm.

8. The rapid design method of the low-frequency broadband sound-absorbing metamaterial structure according to any one of claims 1 to 7, characterized in that, The multi-degree-of-freedom wave-guiding cavity is a polyhedron structure with multiple dimensional degrees of freedom, and the polyhedron structure includes but is not limited to a cuboid, a pyramid, a cone, a frustum of a cone, a pyramid, a frustum of a pyramid; The multi-degree-of-freedom wave-guiding cavity has at least one open end, and the open end of the multi-degree-of-freedom wave-guiding cavity is located on the corresponding self-stabilizing sound-absorbing medium and is flush with the top end of the baffle.

9. The rapid design method of the low-frequency broadband sound-absorbing metamaterial structure according to any one of claims 1 to 7, characterized in that The cross-section of the self-stabilizing multi-degree-of-freedom sound absorber is everywhere a continuous plane composed of the self-stabilizing sound-absorbing medium alone; or The cross-section of the self-stabilizing multi-degree-of-freedom sound absorber is everywhere a single annular continuous plane composed of the self-stabilizing sound-absorbing medium and the multi-degree-of-freedom wave-guiding cavity embedded therein; or A part of the cross-section of the self-stabilizing multi-degree-of-freedom sound absorber is a continuous plane composed of the self-stabilizing sound-absorbing medium alone, and another part of the cross-section of the self-stabilizing multi-degree-of-freedom sound absorber is a single annular continuous plane composed of the self-stabilizing sound-absorbing medium and the multi-degree-of-freedom wave-guiding cavity embedded therein.

10. The rapid design method of the low-frequency broadband sound-absorbing metamaterial structure according to any one of claims 1 to 7, characterized in that The baffle and the partition are made of a high acoustic reflection plate structure.

11. The rapid design method of the low-frequency broadband sound-absorbing metamaterial structure according to any one of claims 1 to 7, characterized in that, The acoustic channel is a semi-through acoustic channel or a full-through acoustic channel; When the acoustic channel is a semi-through acoustic channel, the acoustic channel is a straight channel, an L-shaped channel or a zigzag channel, and the acoustic channel has an opening at the top end of the baffle; When the acoustic channel is a full-through acoustic channel, the acoustic channel is a U-shaped channel or a zigzag channel, and the acoustic channel has more than two openings at the top end of the baffle.

12. The rapid design method of the low-frequency broadband sound-absorbing metamaterial structure according to any one of claims 1 to 7, characterized in that It further includes a wave-transmitting surface protection structure, and the wave-transmitting surface protection structure covers the top end of the baffle.

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