Adjustable acoustic metamaterial systems, optimization methods and equipment for achieving ventilation noise reduction

Abstract

This invention proposes a method for optimizing an adjustable acoustic metamaterial system for ventilation and noise reduction. The method involves designing a helical tubular matrix within a waveguide system, neglecting wall thickness, and using an Archimedean spiral as the cross-section of the helical tubule. A model is constructed using this spiral equation, and its structural parameters are optimized using a genetic algorithm to minimize the fitness values ​​under different parameter combinations. During optimization, the fitness values ​​of the corresponding structural parameters are calculated using finite element analysis software and MATLAB, combining numerical simulation with the genetic algorithm to ultimately determine the optimal geometric structure of the helical tubule. Furthermore, porous sound-absorbing materials are introduced to enhance noise reduction, and a modular splicing structure is employed to achieve reconfigurability. This invention significantly improves the performance of acoustic metamaterials through optimized design.

Description

Technical Field

[0001] This invention relates to the field of airborne acoustics, and in particular to an adjustable acoustic metamaterial system, optimization method, and device for achieving ventilation noise reduction. Background Technology

[0002] Currently, with the rapid development of industrial technology, noise pollution has become increasingly serious, becoming one of the major sources of environmental pollution affecting the quality of human life. Traditional noise control methods mainly use noise reduction enclosures, but for large mechanical equipment, sufficient heat dissipation is essential. Therefore, achieving compatibility between ventilation and efficient noise reduction has become a major technical challenge. Against this backdrop, traditional noise reduction materials based on the mass law have gradually lost their competitiveness, and acoustic metamaterials have emerged. These materials break through the limitations of the mass law through local resonance mechanisms, achieving low-frequency noise reduction at the subwavelength scale. Currently, the mainstream ventilation noise reduction metamaterials mainly fall into three categories: cylindrical silencers, plate-shaped sound barriers, and sparse array acoustic grilles. However, due to the inherent defects of the local resonance mechanism, the noise reduction bandwidth of these structures is relatively narrow. Although the introduction of Fano-like resonance effects has alleviated the problem of narrow bandwidth to some extent, many challenges remain. For example, to achieve a wider noise reduction bandwidth, it is usually necessary to increase the structural thickness, which makes the structure bulky. Moreover, the design of most acoustic metamaterial structures is still mainly based on empirical design, with few adopting optimized design, leaving significant room for optimization. This empirical design approach is not only inefficient but also often fails to achieve optimal noise reduction and ventilation. Secondly, once an existing structure is designed, it is difficult to reconstruct and adjust its frequency according to actual needs after manufacturing. Furthermore, noise frequencies vary greatly in real-world applications, severely limiting the adaptability and practicality of these structures. Even when optimization methods are employed, they typically only optimize under a fixed ventilation rate, failing to accommodate the needs of diverse usage scenarios. Summary of the Invention

[0003] This invention provides an adjustable acoustic metamaterial system, optimization method, and device for achieving ventilation noise reduction, in order to solve the technical problems existing in the prior art.

[0004] The technical solution adopted by this invention to solve the technical problems existing in the prior art is as follows:

[0005] An optimization method for an adjustable acoustic metamaterial system for ventilation noise reduction is proposed. The method involves setting up a helical tubular matrix; ensuring that the cross-sectional shape of each helical tubular body in the matrix is ​​an Archimedean spiral; constructing a helical tubular matrix model based on the Archimedean spiral equation; and optimizing the helical equation parameters in the helical tubular matrix using a genetic algorithm; taking the minimum fitness value of the helical tubular matrix with different equation parameters as the optimization objective; during the optimization process, for a set of equation parameters selected by the genetic algorithm, calculating the fitness value of the helical tubular matrix corresponding to that set of equation parameters using finite element software and MATLAB; and obtaining the optimal geometric equation parameters of the helical tubular body by optimizing the equation parameters of the helical tubular matrix.

[0006] Furthermore, since the number of rows or columns in the helical tubular matrix is ​​1, when optimizing the equation parameters of the helical tubular matrix model using a genetic algorithm, the following two-dimensional model of the single cross-section of a single helical tubular body is constructed using the Archimedean spiral polar coordinate equation:

[0007] ρ=α+βθ=α+β(θ1-θ0);

[0008] Let the frequency range of the acoustic optimization band be [f down f up ];f down To optimize the lowest frequency in the frequency band, f up To optimize the highest frequency in the frequency band; in [f down f up The frequency band corresponding to the frequency range of 600-1100Hz is the main optimized frequency band, and the frequency range of the main optimized frequency band is [f odown f oup ];f odown To optimize the lowest frequency in the primary frequency band, F oup The highest frequency in the primary optimization band; ψ is the sparsity of the helical tubular matrix arrangement; ψ up ψ is the upper limit of the sparsity of the helical tubular matrix arrangement; down This represents the lower limit of the sparsity of the helical tubular matrix arrangement.

[0009] Let a and b be intermediate variables, such that a = 2*(α + βθ1) and b = (a + 2t) / (1 - ψ).

[0010] Based on a two-dimensional model of the single cross-section of a single helical tubular body, a matrix model of the helical tubular body was generated using COMSOL simulation software.

[0011] The objective function for the helical tubular matrix model is set as follows:

[0012]

[0013] The constraints for the helical tubular matrix model are as follows:

[0014] When the frequency is located at [f odown f oup When L is within the range oi <0.2;

[0015] And: α = [1, 10], β = [1.27, 5], θ0 = [0, π], θ1 = [1.5π, 7π], ψ = [0.1, 0.3];

[0016] In the formula:

[0017] band r This is a penalty factor used to constrain the transmission coefficient at any point within the main optimization band to be no greater than 0.2. If the transmission coefficient at all points within the main optimization band is ≤0.2, then the band... r =1; if there is a point in the main optimization band with a transmission coefficient >0.2, then band r =10;

[0018] q1, q2, and q3 are all weighting factors, where q1 takes a value of 0.8, q2 takes a value of 0.1, and q3 takes a value of 0.1.

[0019] θ is the polar angle, representing the total degree rotation of the Archimedean spiral;

[0020] θ0 is the initial polar angle of the Archimedean spiral;

[0021] θ1 is the terminal polar angle of the Archimedean spiral;

[0022] ρ is the distance from a point on the Archimedean spiral to the center of the polar coordinate system;

[0023] α is the distance from a point on the Archimedean spiral to the center of the polar coordinates when θ0 equals 0;

[0024] β is the growth rate of the radius of the Archimedean spiral;

[0025] t represents the thickness of the wall of the helical tubular body 1;

[0026] i is the discrete frequency point number;

[0027] n r This refers to the number of all discrete frequency points other than the main optimization frequency band;

[0028] T i The frequency corresponding to the i-th discrete frequency point belongs to [f down f up And does not belong to [f] odown f oup Transmission coefficient under the condition of ]; T oiThe frequency corresponding to the i-th discrete frequency point belongs to [f odown f oup Transmission coefficient under the condition of ];

[0029] fitness is the fitness of the helical tubular matrix model.

[0030] Furthermore, using COMSOL finite element analysis software, a 1-row * 1-column helical tubular matrix finite element model was established. The helical tubular matrix finite element model was divided into six sequentially connected regions, namely the first region to the sixth region. The first and fifth regions are sound-absorbing boundaries, using a perfectly matched layer; the second region is the sound wave incident region, using a plane wave background pressure field with a pressure amplitude set to 1 Pa; the third region is the helical tubular region; and the fourth region is the sound wave transmission region. The transmission coefficient within this region was calculated.

[0031] Furthermore, the genetic algorithm was optimized using COMSOL numerical simulation and MATLAB parallel computing.

[0032] Furthermore, the cross-sectional shape of the helical tube is a double Archimedean spiral, which consists of two helical tubes with single Archimedean spiral cross-sections, forming a centrally symmetrical structure centered on the origin.

[0033] Furthermore, multiple nodes with different polar angles are set on the Archimedean spiral line corresponding to the cross-section of the spiral tube, dividing a single Archimedean spiral line into K segments. Correspondingly, the tube wall of the spiral tube with a cross-sectional shape of g Archimedean spirals is vertically cut into g*K tube segments, and a base for fixing the tube segments is set. According to the starting polar angle requirement of the Archimedean spiral line, the corresponding tube segments are detachably installed on the base to realize the adjustment of the starting polar angle of the Archimedean spiral line of the spiral tube.

[0034] Furthermore, the base is provided with slots in the shape of double Archimedean spirals for inserting pipe pieces.

[0035] The present invention also provides an adjustable acoustic metamaterial system for achieving ventilation noise reduction, which is prepared using the above-described optimized method for achieving an adjustable acoustic metamaterial system for ventilation noise reduction.

[0036] The present invention also provides an apparatus for optimizing a method for an adjustable acoustic metamaterial system for ventilation and noise reduction, comprising a memory and a processor, characterized in that the memory is used to store a computer program; the processor is used to execute the computer program and, when executing the computer program, to implement the method steps of the above-described method for optimizing a adjustable acoustic metamaterial system for ventilation and noise reduction.

[0037] The advantages and positive effects of this invention are:

[0038] This invention discloses an optimization method for an tunable acoustic metamaterial system for ventilation and noise reduction. Combining finite element simulation and genetic algorithms, it efficiently optimizes a broadband ventilation and noise reduction structure under constraints of a given optimization frequency, fitness function, size, and structural transmission coefficient. A sparsity factor is introduced into the fitness function to comprehensively consider the balance between noise reduction and ventilation effects. To absorb high-frequency sound waves and suppress transmission peaks generated by structural resonance, porous media are introduced inside the structure, thereby improving the noise reduction effect. Simultaneously, the optimized structure is modularly designed, enabling discrete modules for different frequencies. Subsequent frequency tuning based on changes in frequency greatly increases the structure's flexibility. In practical applications, re-optimization can be performed according to production size requirements, repeating the above steps to obtain the optimized solution at the corresponding frequency. This design method not only improves the performance of the ventilation and noise reduction metamaterial but also increases its applicability and flexibility in various application scenarios.

[0039] This invention optimizes tunable acoustic metamaterial systems by combining optimization algorithms and simulation techniques, which can significantly improve the performance of acoustic metamaterials and achieve more efficient noise control. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of an adjustable acoustic metamaterial system for achieving ventilation and noise reduction according to the present invention.

[0041] Figure 2 This is a schematic diagram of a multi-segment assembly of a spiral tubular structure.

[0042] Figure 3 This is a schematic diagram of a multi-segment combination of a spiral tubular structure and sound-absorbing materials.

[0043] Figure 4 This is a schematic diagram of a cross-section of a multi-segment assembly of a helical tubular structure.

[0044] Figure 5 A schematic diagram of the initial polar angle of each segment when the single Archimedean spiral corresponding to the cross-sectional shape of the helical tubule is divided into multiple segments.

[0045] Figure 6 This is a schematic diagram of the base structure for fixing the tube segments.

[0046] Figure 7 A schematic diagram of a helical tubular matrix finite element model created for the COMSOL finite element calculation software.

[0047] Figure 8 This is the optimized transmission curve of a spiral tubular matrix finite element model according to the present invention.

[0048] Figure 9The transmission curves are obtained from simulation comparison and experimental verification of the optimized finite element model of a spiral tubular matrix according to the present invention.

[0049] Figure 10 This is a graph showing the transmission coefficient variation of a spiral tubular matrix finite element model according to the present invention, where the transmission coefficient changes with the initial polar angle θ0.

[0050] Figure 11 This is a schematic diagram comparing the numerical simulation and experimental measurement results corresponding to the change in the initial polar angle when inserting different tube segments during the frequency modulation function of this invention.

[0051] In the diagram: 1. Helical tubular body; 1-1. Tube segment with initial polar angle of 0; 1-2. Tube segment with initial polar angle of 1.7; 1-3. Tube segment with initial polar angle of 4.5; 1-4. Tube segment with initial polar angle of 5.1; 2. Upper cover plate of waveguide system; 3. Loudspeaker; 4. Base; 5. Slot; 6. Porous material; 7. Lower cover plate of waveguide system.

[0052] a represents the length of the base; b represents the width of the base; h represents the thickness of the base; l represents the height of the spiral tube; t represents the thickness of the spiral tube wall.

[0053] θ 01 This represents the polar angle corresponding to the first node on a single Archimedean spiral.

[0054] θ 02 This represents the polar angle corresponding to the second node on a single Archimedean spiral.

[0055] θ 03 This represents the polar angle corresponding to the third node on a single Archimedean spiral. Detailed Implementation

[0056] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0057] The following are the Chinese definitions of English words, abbreviations, and phrases:

[0058] COMSOL is an advanced software platform for multiphysics simulation and modeling.

[0059] MATLAB is a commercial mathematical software produced by MathWorks, Inc. in the United States. It is used in fields such as data analysis, wireless communication, deep learning, image processing and computer vision, signal processing, quantitative finance and risk management, robotics, and control systems.

[0060] In the description of this invention, the terms "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," and "bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and do not require the invention to be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on the invention. The terms "connected" and "linked" used in this invention should be interpreted broadly. For example, they can refer to a fixed connection or a detachable connection; a direct connection or an indirect connection through intermediate components; or an electrical connection or signal transmission. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0061] Please see Figures 1 to 11 An optimization method for an adjustable acoustic metamaterial system for ventilation and noise reduction is proposed. The method involves setting up a helical tubular matrix; ignoring the wall thickness, ensuring that the cross-sectional shape of each helical tubular body 1 in the helical tubular matrix is ​​an Archimedean spiral; constructing a helical tubular matrix model based on the Archimedean spiral equation; and optimizing the equation parameters of the helical tubular matrix using a genetic algorithm; taking the minimum fitness value of the helical tubular matrix with different equation parameters as the optimization objective; during the optimization process, for a set of equation parameters selected by the genetic algorithm, calculating the fitness value of the helical tubular matrix corresponding to that set of equation parameters using finite element software; and obtaining the optimal geometric equation parameters of the helical tubular body 1 by optimizing the equation parameters of the helical tubular matrix.

[0062] Please see Figure 1 The waveguide system includes: a matrix of helical tubular bodies 1, a waveguide system upper cover plate 2, a loudspeaker 3, a porous material 6, and a waveguide system lower cover plate 7. The vertically arranged helical tubular bodies 1 are located between the waveguide system upper cover plate 2 and the waveguide system lower cover plate 7. Three sides of the four perimeter of the matrix of helical tubular bodies 1 are enclosed by the porous material 6, with one side open. A loudspeaker 3 is installed on one side of the opening.

[0063] The helical tubular matrix installed in the cavity of a waveguide system or other device used for ventilation and noise reduction can be an E-row * F-column helical tubular matrix.

[0064] Preferably, the number of rows or columns in the helical tubular matrix can be 1, i.e., E = 1 or F = 1. When optimizing the structural parameters of the helical tubular matrix model with E = 1 or F = 1 using a genetic algorithm, the equation parameters of the helical tubular matrix model are optimized using a genetic algorithm. The following two-dimensional model of a single cross-section of a single helical tubular body is constructed using the Archimedean spiral polar coordinate equation:

[0065] ρ=α+βθ=α+β(θ1-θ0);

[0066] Let the frequency range of the acoustic optimization band be [fdown f up ];f down To optimize the lowest frequency in the frequency band, f up To optimize the highest frequency in the frequency band; in [f down f up The frequency band corresponding to the frequency range of 600-1100Hz is the main optimized frequency band, and the frequency range of the main optimized frequency band is [f odown f oup ];f odown To optimize the lowest frequency in the primary frequency band, F oup The highest frequency in the primary optimization band; ψ is the sparsity of the helical tubular matrix arrangement; ψ up ψ is the upper limit of the sparsity of the helical tubular matrix arrangement; down This represents the lower limit of the sparsity of the helical tubular matrix arrangement.

[0067] Let a and b be intermediate variables, such that a = 2*(α + βθ1) and b = (a + 2t) / (1 - ψ);

[0068] Based on a two-dimensional model of the single cross-section of a single helical tubular body, a matrix model of the helical tubular body was generated using COMSOL simulation software.

[0069] The objective function for the helical tubular matrix model is set as follows:

[0070]

[0071] The constraints for the helical tubular matrix model are as follows:

[0072] When the frequency is located at [f odown f oup When T is within the range oi <0.2;

[0073] And: α = [1, 10], β = [1.27, 5], θ0 = [0, π], θ1 = [1.5π, 7π], ψ = [0.1, 0.3];

[0074] In the formula:

[0075] band r This is a penalty factor used to constrain the transmission coefficient at any point within the main optimization band to be no greater than 0.2. If the transmission coefficient at all points within the main optimization band is ≤0.2, then the band... r =1; if there is a point in the main optimization band with a transmission coefficient >0.2, then band r =10;

[0076] q1, q2, and q3 are all weighting factors, where q1 takes a value of 0.8, q2 takes a value of 0.1, and q3 takes a value of 0.1.

[0077] θ is the polar angle, representing the total degree rotation of the Archimedean spiral;

[0078] θ0 is the initial polar angle of the Archimedean spiral;

[0079] θ1 is the terminal polar angle of the Archimedean spiral;

[0080] ρ is the distance from a point on the Archimedean spiral to the center of the polar coordinate system;

[0081] α is the distance from a point on the Archimedean spiral to the center of the polar coordinates when θ0 equals 0;

[0082] β is the growth rate of the radius of the Archimedean spiral;

[0083] t represents the thickness of the wall of the helical tubular body 1.

[0084] i is the discrete frequency point number;

[0085] n r This refers to the number of all discrete frequency points other than the main optimization frequency band;

[0086] T i The frequency corresponding to the i-th discrete frequency point belongs to [f down f up And does not belong to [f] odown f oup Transmission coefficient under the condition of ]; T oi The frequency corresponding to the i-th discrete frequency point belongs to [f odown f oup Transmission coefficient under the condition of ];

[0087] fitness is the fitness of the helical tubular matrix model.

[0088] The goal of the model is to minimize the fitness of the spiral tubular matrix model; the minimum fitness of the spiral tubular matrix model is obtained by optimization using a genetic algorithm.

[0089] The sparsity of the helical tube matrix arrangement represents the distance between two adjacent helical tubes 1 in the waveguide system. When the helical tube matrix is ​​1 row and 1 column, and the width of the waveguide system's cavity is equal to the width b of the base 4, and the width of the waveguide system's cavity is aligned with the width direction of the base 4, then, after determining the width of the waveguide system, let the longest radius of a single Archimedean spiral of the helical tube 1 be r, then:

[0090] Sparsity = (ba - 2*t) / b.

[0091] Preferably, COMSOL finite element calculation software can be used to establish a 1-row * 1-column helical tubular matrix finite element model, that is, to establish a helical tubular matrix finite element model where E and F are both equal to 1.

[0092] Please see Figure 7 This is equivalent to having only one helical tube 1 in the helical tubular matrix, i.e., setting one helical tube 1 within the waveguide system. The finite element model of the helical tubular matrix is ​​divided into six sequentially connected regions, namely the first region to the sixth region. The first and fifth regions are sound-absorbing boundaries, using a perfectly matched layer. The second region is the sound wave incident region, using a plane wave background pressure field with a pressure amplitude set to 1 Pa. The third region is the helical tubular region, and the fourth region is the sound wave transmission region. The transmission coefficient within this region is calculated.

[0093] Based on a 1x1 helical tubular matrix finite element model, the topology can be extended along the bottom surface of the waveguide system in the front-back and left-right directions; thus, an ExxF helical tubular matrix finite element model can be constructed. In the helical tubular matrix, some matrix elements are 1, and some are 0. A matrix element of 1 indicates that a helical tubular element 1 is present, while a matrix element of 0 indicates that a helical tubular element 1 is not present.

[0094] The parameters of the m equations to be optimized can be α, β, θ0, θ1, and ψ; other equation parameters, such as the height 1 of the helical tube 1 and the thickness i of the tube wall of the helical tube 1, are set according to experience and the requirements of the usage environment.

[0095] Preferably, the cross-sectional shape of the helical tube 1 can be a double Archimedean spiral, which is two helical tubes 1 with single Archimedean spiral cross-sections, and a centrally symmetrical structure centered on the origin.

[0096] Preferably, multiple nodes with different polar angles are set on the Archimedean spiral line corresponding to the cross-section of the spiral tube 1, dividing a single Archimedean spiral line into K segments, correspondingly cutting the tube wall of the spiral tube 1 with a cross-sectional shape of g Archimedean spiral lines vertically into g*K tube segments.

[0097] For example, if a single Archimedean spiral is divided into 4 segments, the wall of a spiral tube 1 with a cross-sectional shape of 2 Archimedean spirals is vertically cut into 2*4 segments, or 8 segments.

[0098] A base 4 for fixing the tube segments can be set; according to the starting polar angle requirement of the Archimedean spiral, the corresponding tube segments can be arranged according to the size of the starting polar angle and installed on the base 4 in a detachable manner to realize the adjustment of the starting polar angle of the Archimedean spiral of the spiral tube 1.

[0099] Let a represent the length of base 4; b represent the width of base 4; h represent the thickness of base 4; l represent the height of spiral tube 1; and t represent the thickness of the wall of spiral tube 1.

[0100] h can be 2–15 mm; 1 can be 50–200 mm; t can be 2–5 mm.

[0101] The values ​​of a and b are related to five optimization parameters: α, β, θ0, θ1, and ψ. Once α, β, θ0, θ1, and ψ are determined, the values ​​of a and b are also determined. a is greater than the maximum value of the outer contour of the cross-section of the helical tube 1 in the length direction of the base 4, and b is greater than the maximum value of the outer contour of the cross-section of the helical tube 1 in the width direction of the base 4.

[0102] The values ​​of a and b can be taken as follows: a = 2*(α+βθ1), such that b = (a+2t) / (1-ψ). This is to ensure that the Archimedes spiral is completely included in the computational domain during the finite element calculation.

[0103] By selecting different minimum starting polar angles for the installation segments, the starting polar angle of the Archimedean spiral of the spiral tube 1 can be adjusted.

[0104] Preferably, the base 4 is provided with a slot 5 in the shape of a double Archimedean spiral for inserting the pipe piece.

[0105] The present invention also provides an adjustable acoustic metamaterial system for achieving ventilation noise reduction, which is prepared using the above-described optimized method for achieving an adjustable acoustic metamaterial system for ventilation noise reduction.

[0106] The present invention also provides an apparatus for optimizing a method for an adjustable acoustic metamaterial system for ventilation and noise reduction, comprising a memory and a processor, characterized in that the memory is used to store a computer program; the processor is used to execute the computer program and, when executing the computer program, to implement the method steps of the above-described method for optimizing a adjustable acoustic metamaterial system for ventilation and noise reduction.

[0107] The workflow and working principle of the present invention will be further described below with reference to a preferred embodiment:

[0108] An optimization method for an adjustable acoustic metamaterial system for ventilation noise reduction is proposed. A helical tubular matrix is ​​set within a waveguide system. Ignoring wall thickness, the cross-sectional shape of each helical tubular body 1 in the helical tubular matrix is ​​an Archimedean spiral. Based on the Archimedean spiral equation, a helical tubular matrix model is constructed, and a genetic algorithm is used to optimize the equation parameters of the helical tubular matrix. The minimum fitness value of the helical tubular matrix with different equation parameters is used as the optimization objective. During the optimization process, for a set of equation parameters selected by the genetic algorithm, the fitness value of the helical tubular matrix corresponding to that set of equation parameters is calculated using finite element software. By combining numerical simulation with the genetic algorithm, the optimal geometric equation parameters of the helical tubular body 1 are obtained by optimizing the equation parameters of the helical tubular matrix.

[0109] This invention provides an optimization method for an adjustable acoustic metamaterial system that achieves ventilation and noise reduction. This method combines simulation calculations with a genetic algorithm to optimize the equation parameters. The fitness function comprehensively considers both the noise reduction effect and the ventilation rate of the structure, aiming to achieve a reasonable balance between the two. To further enhance the noise reduction effect, porous media are introduced into the structure to increase sound energy dissipation.

[0110] To improve structural flexibility, this invention introduces a reconfigurable modular design, which allows the structure to be adjusted and optimized according to actual needs.

[0111] A preferred embodiment of the adjustable acoustic metamaterial system for achieving ventilation noise reduction according to the present invention includes a row of helical tubular matrix or a column of helical tubular matrix within the waveguide system. This adjustable acoustic metamaterial system can be connected to a loudspeaker 3.

[0112] The method of this invention is based on the Archimedean spiral equation, where the number of columns in the spiral tubular matrix can be 1, i.e., F = 1. When optimizing the structural parameters of the spiral tubular matrix model with E = 1 or F = 1 using a genetic algorithm, the equation parameters of the spiral tubular matrix model are optimized using the genetic algorithm. The following two-dimensional cross-sectional model of a single spiral tubular body is constructed using the Archimedean spiral polar coordinate equation:

[0113] ρ=α+βθ=α+β(θ1-θ0);

[0114] Let the frequency range of the acoustic optimization band be [f down f up ];f down To optimize the lowest frequency in the frequency band, f up To optimize the highest frequency in the frequency band; in [f down f up The frequency band corresponding to the frequency range of 600-1100Hz is the main optimized frequency band, and the frequency range of the main optimized frequency band is [fodown f oup ];f odown To optimize the lowest frequency in the primary frequency band, F oup The highest frequency in the primary optimization band; ψ is the sparsity of the helical tubular matrix arrangement; ψ up ψ is the upper limit of the sparsity of the helical tubular matrix arrangement; down This represents the lower limit of the sparsity of the helical tubular matrix arrangement.

[0115] Let a and b be intermediate variables, a = 2*(α+βθ1), such that b = (a+2t) / (1-ψ);

[0116] Based on a two-dimensional model of the single cross-section of a single helical tubular body, a matrix model of the helical tubular body was generated using COMSOL simulation software.

[0117] The objective function for the helical tubular matrix model is set as follows:

[0118]

[0119] The constraints for the helical tubular matrix model are as follows:

[0120] When the frequency is located at [f odown f oup When T is within the range oi <0.2;

[0121] And: α = [1, 10], β = [1.27, 5], θ0 = [0, π], θ1 = [1.5π, 7π], ψ = [0.1, 0.3];

[0122] In the formula:

[0123] band r This is a penalty factor used to constrain the transmission coefficient at any point within the main optimization band to be no greater than 0.2. If the transmission coefficient at all points within the main optimization band is ≤0.2, then the band... r =1; if there is a point in the main optimization band with a transmission coefficient >0.2, then band r =10;

[0124] q1, q2, and q3 are all weighting factors, where q1 takes a value of 0.8, q2 takes a value of 0.1, and q3 takes a value of 0.1.

[0125] θ is the polar angle, representing the total degree rotation of the Archimedean spiral;

[0126] θ0 is the initial polar angle of the Archimedean spiral;

[0127] θ1 is the terminal polar angle of the Archimedean spiral;

[0128] ρ is the distance from a point on the Archimedean spiral to the center of the polar coordinate system;

[0129] α is the distance from a point on the Archimedean spiral to the center of the polar coordinates when θ0 equals 0;

[0130] β is the growth rate of the radius of the Archimedean spiral;

[0131] t represents the thickness of the wall of the helical tubular body 1.

[0132] i is the discrete frequency point number;

[0133] n r This refers to the number of all discrete frequency points other than the main optimization frequency band;

[0134] T i The frequency corresponding to the i-th discrete frequency point belongs to [f down f up And does not belong to [f] odown f oup Transmission coefficient under the condition of ]; T oi The frequency corresponding to the i-th discrete frequency point belongs to [f odown f oup Transmission coefficient under the condition of ];

[0135] fitness is the fitness of the helical tubular matrix model.

[0136] The goal of the model is to minimize the fitness of the spiral tubular matrix model; the minimum fitness of the spiral tubular matrix model is obtained by optimization using a genetic algorithm.

[0137] After the design of a single helical structure is completed, it is rotated 180° around the origin to form a centrally symmetric structure. The optimized geometric equation parameters are input into COMSOL simulation software for simulation verification, resulting in the final ventilation and noise reduction metamaterial structure.

[0138] To ensure the structure achieves noise reduction, it was considered that excessively high sparsity would weaken the structure's resonance effect, leading to a loss of noise reduction, while excessively low sparsity would not provide sufficient ventilation area. Therefore, the sparsity was strictly limited, primarily optimizing the transmission coefficient T within the specified frequency range. i It was set to less than 0.2.

[0139] Please see Figure 10 In the color block on the right, the color gradient represents the transmission coefficient T. i From 0 to 1.

[0140] The optimization process aims to find the minimum value of the fitness function to ensure that the optimal equation parameters are obtained.

[0141] The optimized structure can be modularly discretized, with each specific module corresponding to a specific frequency, which allows the structure to be adjusted and optimized according to requirements.

[0142] The purpose of introducing porous media inside the structure is to suppress the narrow transmission peak caused by the structure's resonance and absorb high-frequency sound waves, thereby improving the noise reduction effect.

[0143] To achieve low-frequency noise reduction, the optimized frequency of this invention is set in the range of 300-1100Hz, with the main optimized frequency set in the range of 600-1100Hz. Through genetic algorithm and numerical simulation optimization, under the set fitness function, the following optimization results were obtained:

[0144] α=4.89, β=4.76, θ0=2.86, θ1=8.3, ψ=0.15;

[0145] The optimization results were verified by finite element analysis, and the transmission curve was plotted, such as... Figure 8 , Figure 9 As shown, it can be observed that the transmission coefficient of the structure is less than 0.2 in the 546-1575Hz range, exhibiting good noise reduction effect.

[0146] The optimization results are analyzed, and continuous θ0 is selected for transmission calculation, such as... Figure 10 As shown in the figure, the results indicate that the noise reduction frequency band of the structure shifts significantly as θ0 changes. Based on this phenomenon, an adjustable ventilation noise reduction structure can be realized.

[0147] The cross-sectional shape of the helical tube 1 is a double Archimedean spiral, which consists of two helical tubes 1 with single Archimedean spiral cross-sections, and is a centrally symmetrical structure centered on the origin.

[0148] On the Archimedean spiral line corresponding to the cross-section of the spiral tube 1, multiple nodes with different polar angles are set to divide a single Archimedean spiral line into K segments, which in turn vertically cut the tube wall of the spiral tube 1 with a cross-sectional shape of g Archimedean spiral lines into g*K tube segments.

[0149] When g = 1 and K = 4, the cross-section of the equivalent helical tubular body 1 contains only a single Archimedean spiral; please refer to [link / reference needed]. Figure 5 Let there be three polar nodes on a single Archimedean spiral, with angles of 1.7, 4.5, and 5.1. Let θ 01 θ represents the polar angle corresponding to the first node on a single Archimedean spiral. 02 θ represents the polar angle corresponding to the second node on a single Archimedean spiral. 03 Let θ represent the polar angle corresponding to the third node on a single Archimedean spiral; then θ 01 =1.7; θ02 =4.5; θ 03 =5.1. Therefore, dividing one Archimedean spiral into four segments corresponds to perpendicularly cutting the wall of the spiral tube 1, whose cross-sectional shape is an Archimedean spiral, into four segments. The four segments are: segment 1-1 with an initial polar angle of 0, segment 1-2 with an initial polar angle of 1.7, segment 1-3 with an initial polar angle of 4.5, and segment 1-4 with an initial polar angle of 5.1.

[0150] When g = 2 and K = 4, the cross-section of the equivalent spiral tube 1 has 2 Archimedean spirals; with 3 polar nodes set at 1.7, 4.5 and 5.1 for the 2 Archimedean spirals, a single Archimedean spiral is divided into 4 segments, which corresponds to the vertical cutting of the tube wall of the spiral tube 1 with a cross-sectional shape of 2 Archimedean spirals into 8 tube segments.

[0151] To fix these segments, a fixed base 4 is introduced outside the segments to fix the segments; according to the Archimedean spiral starting polar angle requirement, the corresponding segments are detachably installed on the base 4 to adjust the starting polar angle of the Archimedean spiral of the spiral tube 1.

[0152] Taking the case where the cross-section of the spiral tube 1 has only a single Archimedean spiral as an example, this paper explains the method for adjusting the starting polar angle of the Archimedean spiral of the spiral tube 1.

[0153] The tube wall is vertically divided into 4 segments; the initial polar angles of the 4 segments are 0, 1.7, 4.5 and 5.1 respectively; the present invention selects four specific θ0, 0, 1.7, 4.5 and 5.1; the segments corresponding to different θ0 can be installed on the base 4 to realize the adjustment of the initial polar angle of the Archimedean spiral of the spiral tube 1.

[0154] a represents the length of base 4; b represents the width of base 4; h represents the thickness of base 4; l represents the height of spiral tube 1; t represents the thickness of the wall of spiral tube 1.

[0155] Dimensions of each part as follows Figure 2 and Figure 6 As shown. The thickness h of the base 4 can be 2mm; the height l of the spiral tube 1 can be 80mm; the wall thickness t of the spiral tube 1 can be 2mm. The length a and width b of the base 4 are determined according to the optimization parameters.

[0156] The base 4 has slots 5 in the shape of a double Archimedean spiral for inserting tube segments. During manufacturing, the outline of the base 4 is pre-designed to allow a gap of 0.1–0.2 mm between the side walls of the slots 5 and the tube segments. By sequentially placing the discrete tube segments into the base 4 and using fixing methods such as adhesive bonding, variations in θ0 can be achieved, thus realizing frequency modulation. Figure 11 As shown.

[0157] To conduct experimental verification, a custom-made waveguide system was constructed. The waveguide system has a rectangular cross-section and is externally constructed using a 10mm thick acrylic sheet (polymethyl methacrylate) to simulate a hard boundary sound field. Sound-absorbing material (melamine) is used around the perimeter. The overall dimensions of the waveguide system are 1500mm (L) × 500mm (W) × 100mm (H). The experimental setup was placed in an anechoic chamber. The overall experimental setup is shown below. Figure 1 As shown.

[0158] To suppress transmission peaks caused by structural resonance and absorb high-frequency sound waves, the cavity between the walls of the helical tube 1 is filled with a porous material 6, which can be made of melamine. A schematic diagram of the internal filling of the structure is shown below. Figure 3 As shown. Finally, place it in the same way as... Figure 1 Transmission tests were conducted in the waveguide shown, and the test results are as follows: Figure 9 As shown in the figure, the experimental results are in good agreement with the simulation results, and a significant trend of high-frequency transmission suppression can be observed.

[0159] The propagation of a single helical tubular unit in a waveguide system was tested at three specific θ0 values, and the results are as follows: Figure 11 As shown, the experimental results are basically consistent with the simulation results, and the noise reduction frequency of the structure shifts significantly with the change of θ0.

[0160] The embodiments described above are only used to illustrate the technical ideas and features of the present invention. Their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. The patent scope of the present invention should not be limited by these embodiments. That is, any equivalent changes or modifications made in accordance with the spirit disclosed in the present invention still fall within the patent scope of the present invention.

Claims

1. An optimization method for an tunable acoustic metamaterial system for achieving ventilation noise reduction, characterized in that, Set up a helical tubular matrix; make the cross-sectional shape of each helical tubular body in the helical tubular matrix an Archimedean spiral; construct a helical tubular matrix model based on the Archimedean spiral equation, and optimize the equation parameters of the helical tubular matrix using a genetic algorithm; take the minimum fitness value of the helical tubular matrix with different equation parameters as the optimization objective; During the optimization process, for a set of equation parameters selected by the genetic algorithm, the fitness value of the helical tube matrix corresponding to the set of equation parameters is calculated using finite element software. By combining numerical simulation with the genetic algorithm, the optimal geometric equation parameters of the helical tube matrix are obtained by optimizing the equation parameters of the helical tube matrix. When optimizing the equation parameters of the helical tubular matrix model using a genetic algorithm with one row or one column, the following two-dimensional model of a single cross-section of a single helical tubular body is constructed using the Archimedean spiral polar coordinate equation: ρ=α+βθ=α+β(θ1-θ0); Let the frequency range of the acoustic optimization band be [f down ,f up ];f down To optimize the lowest frequency in the frequency band, f up To optimize the highest frequency in the frequency band; in [f down ,f up The frequency band corresponding to the frequency range of 600-1100Hz is the main optimized frequency band, and the frequency range of the main optimized frequency band is [f odown ,f oup ];f odown To optimize the lowest frequency in the primary frequency band, f oup The highest frequency in the primary optimization band; ψ is the sparsity of the helical tubular matrix arrangement; ψ up This represents the upper limit of the sparsity ratio of the helical tubular matrix arrangement. ψ down This represents the lower limit of the sparsity of the helical tubular matrix arrangement. Let a and b be intermediate variables, such that a = 2(α + βθ1) and b = (a + 2t) / (1 - ψ); Based on a two-dimensional model of the single cross-section of a single helical tubular body, a matrix model of the helical tubular body was generated using COMSOL simulation software. The objective function for the helical tubular matrix model is set as follows: The constraints for the helical tubular matrix model are as follows: When the frequency is located at [f odown ,f oup When T is within the range oi <0.2; And: α=[1,10], β=[1.27,5], θ0=[0,π], θ1=[1.5π,7π], ψ=[0.1,0.3]; In the formula: band r This is a penalty factor used to constrain the transmission coefficient at any point within the main optimization band to be no greater than 0.

2. If the transmission coefficient at all points within the main optimization band is ≤0.2, then the band... r =1; if there is a point in the main optimization band with a transmission coefficient >0.2, then band r =10; q1, q2, and q3 are all weighting factors, where q1 takes a value of 0.8, q2 takes a value of 0.1, and q3 takes a value of 0.

1. θ is the polar angle, representing the total degree rotation of the Archimedean spiral; θ0 is the initial polar angle of the Archimedean spiral; θ1 is the terminal polar angle of the Archimedean spiral; ρ is the distance from a point on the Archimedean spiral to the center of the polar coordinate system; α is the distance from a point on the Archimedean spiral to the center of the polar coordinates when θ0 equals 0; β is the growth rate of the radius of the Archimedean spiral; t represents the thickness of the spiral tubular body wall. i is the discrete frequency point number; n r This refers to the number of all discrete frequency points other than the main optimization frequency band; T i The frequency corresponding to the i-th discrete frequency point belongs to [f down ,f up And does not belong to [f] odown ,f oup Transmission coefficient under the condition of ]; T oi The frequency corresponding to the i-th discrete frequency point belongs to [f odown ,f oup The transmission coefficient under the condition; fitness is the fitness of the helical tubular matrix model.

2. The optimization method for an adjustable acoustic metamaterial system for achieving ventilation noise reduction according to claim 1, characterized in that, Using COMSOL finite element analysis software, a 1-row x 1-column helical tubular matrix finite element model was established. The helical tubular matrix finite element model was divided into six sequentially connected regions, namely the first region to the sixth region. The first and fifth regions are sound-absorbing boundaries, using a perfectly matched layer. The second region is the sound wave incident region, using a plane wave background pressure field with a pressure amplitude set to 1 Pa. The third region is the helical tubular region, and the fourth region is the sound wave transmission region. The transmission coefficient in this region was calculated.

3. The optimization method for an adjustable acoustic metamaterial system for achieving ventilation noise reduction according to claim 1, characterized in that, Genetic algorithm optimization was performed using COMSOL numerical simulation and MATLAB parallel computing.

4. The optimization method for an adjustable acoustic metamaterial system for achieving ventilation noise reduction according to claim 1, characterized in that, The cross-sectional shape of the helical tube is a double Archimedean spiral, which consists of two helical tubes with single Archimedean spiral cross-sections, and is a centrally symmetrical structure centered on the origin.

5. The optimization method for an adjustable acoustic metamaterial system for achieving ventilation noise reduction according to claim 1, characterized in that, On the Archimedean spiral line corresponding to the cross-section of the spiral tubular body, multiple nodes with different polar angles are set, dividing a single Archimedean spiral line into K segments. Correspondingly, the wall of the spiral tubular body with a cross-sectional shape of g Archimedean spiral lines is vertically cut into g*K segments, and a base for fixing the segments is set. According to the starting polar angle requirement of the Archimedean spiral line, the corresponding segments are detachably installed on the base to realize the adjustment of the starting polar angle of the Archimedean spiral line of the spiral tubular body.

6. The optimization method for an adjustable acoustic metamaterial system for achieving ventilation noise reduction according to claim 5, characterized in that, The base has slots shaped like double Archimedean spirals for inserting pipe pieces.

7. An adjustable acoustic metamaterial system for achieving ventilation noise reduction, characterized in that, The system is prepared using the optimization method of the adjustable acoustic metamaterial system for achieving ventilation and noise reduction as described in any one of claims 1 to 6.

8. An apparatus for optimizing a tunable acoustic metamaterial system for ventilation noise reduction, comprising a memory and a processor, characterized in that, The memory is used to store a computer program; the processor is used to execute the computer program and, when executing the computer program, to implement the method steps of the optimization method for achieving a tunable acoustic metamaterial system for ventilation noise reduction as described in any one of claims 1 to 6.

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