Adjustable acoustic metamaterial system for realizing ventilation and noise reduction, optimization method and equipment

Abstract

The invention provides a method for optimizing a ventilation and noise reduction adjustable acoustic metamaterial system. According to the method, a spiral tubular body matrix in a waveguide system is designed, the thickness of a tube wall is ignored, and an Archimedes spiral line is adopted as the cross section of a spiral tubular body. And constructing a model by using the spiral line equation, and optimizing structural parameters of the model through a genetic algorithm so as to minimize fitness values under different parameter combinations. In the optimization process, fitness values of corresponding structure parameters are calculated in combination with finite element software and MATLAB, numerical simulation is combined with a genetic algorithm, and finally the optimal geometric structure of the spiral tubular body is determined. In addition, a porous sound absorption material is introduced to improve the noise reduction effect, and a modular splicing structure is adopted to achieve the reconfigurable function. The performance of the acoustic metamaterial is remarkably improved through optimization design.

Description

Technical Field

[0001] The present invention relates to the field of airborne sound technology, and in particular to an adjustable acoustic metamaterial system, an optimization method and a device for achieving ventilation noise reduction. Background Art

[0002] At present, with the rapid development of industrial technology, the problem of noise pollution is becoming increasingly serious and has become one of the main sources of environmental pollution that affects the quality of human life. The traditional noise control method mainly uses noise reduction covers, but for large-scale mechanical equipment, sufficient heat dissipation conditions are essential. Therefore, achieving the compatibility of ventilation and efficient noise reduction has become a major technical challenge. In this context, traditional noise reduction materials based on the mass law have gradually lost their competitiveness, and acoustic metamaterials have emerged. This type of material breaks through the limitations of the mass law through the local resonance mechanism and achieves low-frequency noise reduction on a subwavelength scale. At present, there are three main types of mainstream ventilation noise reduction metamaterials: cylindrical silencers, plate-shaped sound barriers, and sparse array sound grilles. However, due to the inherent defects of the local resonance mechanism, the noise reduction bands of these structures are relatively narrow. Although the introduction of the Fano-like resonance effect has alleviated the problem of narrow bands to a certain extent, there are still many challenges. For example, in order to achieve a wider noise reduction band, it is usually necessary to increase the thickness of the structure, which makes the structure bulky. In addition, the design of most acoustic metamaterial structures is still based on empirical design, and there are few optimized designs, and there is significant room for optimization. This empirical design method is not only inefficient, but also often fails to achieve the best noise reduction and ventilation effects. Secondly, once the existing structure is designed, it is difficult for most existing structures to reconstruct and adjust the frequency according to actual needs after manufacturing. In actual applications, the noise frequency is variable, which greatly limits the adaptability and practicality of these structures. Even if some designs use optimization methods, they are usually only optimized under a fixed ventilation rate and cannot take into account the needs of multiple usage scenarios. Summary of the invention

[0003] The present invention provides an adjustable acoustic metamaterial system, an optimization method and a device for realizing ventilation noise reduction in order to solve the technical problems existing in the known technologies.

[0004] The technical solution adopted by the present invention to solve the technical problems existing in the known technology is:

[0005] An optimization method for an adjustable acoustic metamaterial system for achieving ventilation noise reduction comprises the following steps: setting a spiral tubular matrix; making the cross-sectional shape of each spiral tubular body in the spiral tubular matrix an Archimedean spiral; constructing a spiral tubular matrix model based on the Archimedean spiral equation, and optimizing the spiral equation parameters in the spiral tubular matrix by using a genetic algorithm; taking the minimum fitness value of the spiral tubular matrix when using different equation parameters as an optimization target; during the optimization process, for a set of equation parameters selected by the genetic algorithm, using finite element software and MATLAB to calculate the fitness value of the spiral tubular matrix corresponding to the set of equation parameters, and obtaining the optimal geometric equation parameters of the spiral tubular body by optimizing the equation parameters of the spiral tubular matrix.

[0006] Furthermore, the number of rows or columns of the helical tubular matrix is ​​1. When the equation parameters of the helical tubular matrix model are optimized by using a genetic algorithm, the Archimedean spiral polar coordinate equation is used to construct the following two-dimensional model of the monomer cross section of a single helical tubular body:

[0007] ρ=α+βθ=α+β(θ1-θ0);

[0008] Assume: The frequency range of the acoustic optimization band is [f down , f up ]; f down To optimize the lowest frequency in the band, f up To optimize the highest frequency in the frequency band; in [f down , f up ] 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 frequency band, F oup is the highest frequency in the main optimized frequency band; ψ is the sparseness rate of the spiral tubular matrix; ψ up is the upper limit of the sparsity rate of the helical tubular matrix; ψ down is the lower limit of the sparsity rate of the helical tubular matrix arrangement;

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

[0010] Based on the two-dimensional model of the monomer cross section of a single helical tubular body, a helical tubular matrix model is generated by COMSOL simulation software;

[0011] The objective function of the helical tube matrix model is set as follows:

[0012]

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

[0014] When the frequency is [f odown , f oup ] range L 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] Where:

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

[0018] q1, q2, and q3 are all weighting factors, where q1 is 0.8, q2 is 0.1, and q3 is 0.1;

[0019] θ is the polar angle, which represents the total number of degrees that the Archimedean spiral rotates;

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

[0021] θ1 is the polar angle at which the Archimedean spiral ends;

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

[0023] α is the distance from the point on the Archimedean spiral to the center of the polar coordinate when θ0 is equal to 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 is the number of all discrete frequency points except the main optimized frequency band;

[0028] T i The frequency corresponding to the ith discrete frequency point belongs to [f down , f up ] and does not belong to [f odown , f oup ]The transmission coefficient under the condition of oiThe frequency corresponding to the ith discrete frequency point belongs to [f odown , f oup ]The transmission coefficient under the condition of

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

[0030] Furthermore, the COMSOL finite element calculation software was used to establish a 1-row*1-column spiral tubular matrix finite element model, and the spiral tubular matrix finite element model was divided into six sequentially connected regions, namely the first region to the sixth region, where the first and fifth regions are sound absorption boundaries, using perfect matching layers; the second region is the sound wave incident region, using a plane wave background pressure field, and the pressure amplitude is set to 1Pa; the third region is the spiral tubular body area, and the fourth region is the sound wave transmission area, and the transmission coefficient in this region is calculated.

[0031] Furthermore, COMSOL numerical simulation and MATLAB parallel computing were used to perform genetic algorithm optimization.

[0032] Furthermore, the cross-sectional shape of the helical tubular body is a double Archimedean spiral, which is a centrally symmetrical structure with the origin as the center, consisting of two helical tubular bodies with a single Archimedean spiral cross-section.

[0033] Furthermore, a plurality of nodes corresponding to different polar angles are arranged on the Archimedean spiral corresponding to the cross section of the spiral tubular body, and a single Archimedean spiral is divided into K segments. Correspondingly, the tube wall of the spiral tubular body having a cross section in the shape of g Archimedean spirals is vertically cut into g*K tube segments, and a base for fixing the tube segments is arranged; according to the requirements of the starting polar angle of the Archimedean spiral, the corresponding tube segments are detachably mounted on the base, so as to realize the adjustment of the starting polar angle of the Archimedean spiral of the spiral tubular body.

[0034] Furthermore, a slot in the shape of a double Archimedean spiral for inserting the pipe piece is provided on the base.

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

[0036] The present invention also provides a device for realizing an optimization method of an adjustable 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 implement the method steps of the optimization method of the adjustable acoustic metamaterial system for ventilation noise reduction as described above when executing the computer program.

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

[0038] The present invention provides an optimization method for an adjustable acoustic metamaterial system for achieving ventilation noise reduction, which combines finite element simulation and genetic algorithm. Under the constraints of a given optimization frequency, fitness function, size and structural transmission coefficient, a broadband ventilation noise reduction structure can be efficiently optimized. The sparsity rate is introduced into the fitness function, and the balance between the noise reduction effect and the ventilation effect is comprehensively considered. In order to absorb high-frequency sound waves and suppress the transmission peak generated by structural resonance, a porous medium is introduced into the structure, thereby improving the noise reduction effect of the structure. At the same time, the optimized structure is modularly designed to achieve module discretization of different frequencies. The structure can be subsequently frequency-modulated according to the change in frequency, greatly increasing the flexibility of the structure. In practical applications, it can be re-optimized according to the size requirements of production, and the above steps can be repeated to obtain the optimized solution at the corresponding frequency. This design method not only improves the performance of the ventilation noise reduction metamaterial, but also increases its applicability and flexibility in a variety of application scenarios.

[0039] The present invention optimizes the adjustable acoustic metamaterial system by combining optimization algorithm and simulation technology, which can greatly improve the performance of acoustic metamaterials and achieve more efficient noise control. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0041] Figure 2 It is a schematic diagram of the structure of a combination of multiple segments of a spiral tubular body.

[0042] Figure 3 Schematic diagram of the combination of multiple tube segments and sound-absorbing materials of a spiral tubular body.

[0043] Figure 4 It is a schematic cross-sectional view of a combination of multiple segments of a spiral tubular body.

[0044] Figure 5 Schematic diagram of the starting polar angles of each segment when a single Archimedean spiral corresponding to the cross-sectional shape of the spiral tubular body is divided into multiple segments.

[0045] Figure 6 Schematic diagram of the base structure for fixing the pipe segments.

[0046] Figure 7 Schematic diagram of the helical tubular matrix finite element model established for COMSOL finite element calculation software.

[0047] Figure 8 It is a transmission curve after optimization of the helical tubular matrix finite element model of the present invention.

[0048] Fig. 9It is a transmission curve of simulation comparison and experimental verification after optimization of a spiral tubular matrix finite element model of the present invention.

[0049] Fig.10 The transmission coefficient variation diagram of the spiral tubular matrix finite element model according to the present invention changes with the starting polar angle θ0.

[0050] Fig.11 It is a schematic diagram comparing the numerical simulation and experimental measurement results corresponding to the change of the starting polar angle when different pipe segments are inserted during the frequency modulation function of the present invention.

[0051] In the figure: 1. spiral tubular body; 1-1. tube segment with a starting polar angle of 0; 1-2. tube segment with a starting polar angle of 1.7; 1-3. tube segment with a starting polar angle of 4.5; 1-4. tube segment with a starting polar angle of 5.1; 2. upper cover of waveguide system; 3. speaker; 4. base; 5. slot; 6. porous material; 7. lower cover 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 tubular body; and t represents the thickness of the wall of the spiral tubular body.

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

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

[0055] θ 03 Represents the polar angle corresponding to the third node on a single Archimedean spiral. DETAILED DESCRIPTION

[0056] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

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

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

[0059] MATLAB: It is a commercial mathematical software produced by MathWorks, an American company, used in data analysis, wireless communications, deep learning, image processing and computer vision, signal processing, quantitative finance and risk management, robotics, control systems and other fields.

[0060] In the description of the present invention, the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention rather than requiring the present invention to be constructed and operated in a specific orientation, and therefore should not be construed as limiting the present invention. The terms "connected" and "connection" used in the present invention should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection; it can be a direct connection or an indirect connection through an intermediate component; it can also be an electrical connection or signal transmission; for those of ordinary skill in the art, the specific meanings of the above terms can be understood according to the specific circumstances.

[0061] See also Figures 1 to 11 , an optimization method for an adjustable acoustic metamaterial system for achieving ventilation noise reduction, setting a spiral tubular matrix; ignoring the tube wall thickness, making the cross-sectional shape of each spiral tubular body 1 in the spiral tubular matrix an Archimedean spiral; constructing a spiral tubular matrix model based on the Archimedean spiral equation, and using a genetic algorithm to optimize the equation parameters of the spiral tubular matrix; taking the minimum fitness value of the spiral tubular matrix when using different equation parameters as the optimization target; during the optimization process, for a set of equation parameters selected by the genetic algorithm, using finite element software to calculate the fitness value of the spiral tubular matrix corresponding to the set of equation parameters, and obtaining the optimal geometric equation parameters of the spiral tubular body 1 by optimizing the equation parameters of the spiral tubular matrix.

[0062] See also Figure 1 The waveguide system includes: a matrix of spiral tubular bodies 1, a waveguide system upper cover plate 2, a speaker 3, a porous material 6, and a waveguide system lower cover plate 7. The vertically arranged spiral 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 matrix of spiral tubular bodies 1 are surrounded by porous materials 6, and one side is open, and a speaker 3 is arranged on one side of the opening.

[0063] The spiral tubular body matrix arranged in a cavity for ventilation and noise reduction such as a waveguide system may be a spiral tubular body matrix of E rows and F columns.

[0064] Preferably, the number of rows or columns of the helical tubular matrix can be 1, that is, E = 1 or F = 1. When the genetic algorithm is used to optimize the structural parameters of the helical tubular matrix model with E = 1 or F = 1, the genetic algorithm is used to optimize the equation parameters of the helical tubular matrix model, and the Archimedean spiral polar coordinate equation is used to construct the following single helical tubular monomer cross-section two-dimensional model:

[0065] ρ=α+βθ=α+β(θ1-θ0);

[0066] Assume: The frequency range of the acoustic optimization band is [fdown , f up ]; f down To optimize the lowest frequency in the band, f up To optimize the highest frequency in the frequency band; in [f down , f up ] 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 frequency band, F oup is the highest frequency in the main optimized frequency band; ψ is the sparseness rate of the spiral tubular matrix; ψ up is the upper limit of the sparsity rate of the helical tubular matrix; ψ down is the lower limit of the sparsity rate of the helical tubular matrix arrangement;

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

[0068] Based on the two-dimensional model of the monomer cross section of a single helical tubular body, a helical tubular matrix model is generated by COMSOL simulation software;

[0069] The objective function of the helical tube matrix model is set as follows:

[0070]

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

[0072] When the frequency is [f odown , f oup ] range T 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] Where:

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

[0076] q1, q2, and q3 are all weighting factors, where q1 is 0.8, q2 is 0.1, and q3 is 0.1;

[0077] θ is the polar angle, which represents the total number of degrees that the Archimedean spiral rotates;

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

[0079] θ1 is the polar angle at which the Archimedean spiral ends;

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

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

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

[0083] t represents the thickness of the wall of the spiral tube 1

[0084] i is the discrete frequency point number;

[0085] n r is the number of all discrete frequency points except the main optimized frequency band;

[0086] T i The frequency corresponding to the ith discrete frequency point belongs to [f down , f up ] and does not belong to [f odown , f oup ]The transmission coefficient under the condition of oi The frequency corresponding to the ith discrete frequency point belongs to [f odown , f oup ]The transmission coefficient under the condition of

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

[0088] The minimum fitness value of the helical tubular matrix model is taken as the goal of the model; the minimum fitness value of the helical tubular matrix model is obtained by optimizing the genetic algorithm.

[0089] The sparseness rate of the spiral tubular matrix indicates the distance between two adjacent spiral tubular bodies 1 in the waveguide system. When the spiral tubular matrix is ​​1 row and 1 column, the inner cavity width of the waveguide system is equal to the width b of the base 4, and the inner cavity width of the waveguide system is consistent with the width direction of the base 4. After the width of the waveguide system is determined, the longest radius of a single Archimedean spiral of the spiral tubular body 1 is set to r, then:

[0090] Sparsity ratio = (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 in which E and F are both equal to 1.

[0092] See also Figure 7 , which is equivalent to that the helical tubular matrix has only one helical tubular body 1, that is, a helical tubular body 1 is set in 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, wherein the first region and the fifth region are sound absorption boundaries, and a perfect matching layer is used; the second region is the sound wave incident region, and a plane wave background pressure field is used, and the pressure amplitude is set to 1Pa; the third region is the helical tubular region, and the fourth region is the sound wave transmission region, and the transmission coefficient in this region is calculated.

[0093] Based on the 1-row*1-column spiral tubular matrix finite element model, the topology can be extended in the front-back and left-right directions along the bottom surface of the waveguide system; that is, the E-row*F-column spiral tubular matrix finite element model can be constructed. Some matrix elements in the spiral tubular matrix are 1, and some matrix elements are 0. The position where the matrix element is 1 indicates that the spiral tubular body 1 is set, and the position where the matrix element is 0 indicates that the spiral tubular body 1 is not set.

[0094] The m equation parameters to be optimized may be selected from α, β, θ0, θ1, ψ; other equation parameters, such as the height 1 of the spiral tubular body 1 and the thickness i of the wall of the spiral tubular body 1 are set according to experience and use environment requirements.

[0095] Preferably, the cross-sectional shape of the helical tubular body 1 may be a double Archimedean spiral, which is a centrally symmetrical structure with the origin as the center, consisting of two helical tubular bodies 1 with a single Archimedean spiral cross-section.

[0096] Preferably, a plurality of nodes corresponding to different polar angles are arranged on the Archimedean spiral corresponding to the cross section of the spiral tubular body 1 to divide a single Archimedean spiral into K segments, and the tube wall of the spiral tubular body 1 having a cross section in the shape of g Archimedean spirals is vertically cut into g*K tube segments.

[0097] For example, a single Archimedean spiral is divided into four sections, and correspondingly, the tube wall of the spiral tubular body 1 having a cross-sectional shape of two Archimedean spirals is vertically cut into 2*4 tube segments, that is, 8 tube segments.

[0098] A base 4 for fixing the pipe segments can be provided; according to the requirements of the starting polar angle of the Archimedean spiral, the corresponding pipe segments can be sorted according to the starting polar angle size and installed on the base 4 in sequence so as to be detachable, so as to adjust the starting polar angle of the Archimedean spiral of the spiral tubular body 1.

[0099] It can be assumed that a represents the length of the base 4 ; b represents the width of the base 4 ; h represents the thickness of the base 4 ; 1 represents the height of the spiral tubular body 1 ; and t represents the thickness of the wall of the spiral tubular body 1 .

[0100] The value of h can be 2 to 15 mm; the value of 1 can be 50 to 200 mm; the value of t can be 2 to 5 mm.

[0101] The values ​​of a and b are related to the five optimization parameters α, β, θ0, θ1, and ψ. When α, β, θ0, θ1, and ψ are determined, the values ​​of a and b are determined accordingly. a is greater than the maximum value of the outer contour of the cross section of the spiral tubular body 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 spiral tubular body 1 in the width direction of the base 4.

[0102] The values ​​of a and b can be as follows: a = 2*(α + βθ1), so that b = (a + 2t) / (1-ψ). This is to ensure that the calculation area can completely include the Archimedean spiral during the finite element calculation process.

[0103] By selecting different minimum starting polar angles for installing the pipe segments, the starting polar angle of the Archimedean spiral of the spiral tubular body 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, and the system is prepared using the above-mentioned optimization method for the adjustable acoustic metamaterial system for achieving ventilation noise reduction.

[0106] The present invention also provides a device for realizing an optimization method of an adjustable 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 implement the method steps of the optimization method of the adjustable acoustic metamaterial system for ventilation noise reduction as described above when executing the computer program.

[0107] The following is a preferred embodiment of the present invention to further illustrate the working process and working principle of the present invention:

[0108] An optimization method for an adjustable acoustic metamaterial system for achieving ventilation noise reduction comprises the following steps: setting a spiral tubular matrix in a waveguide system; ignoring the tube wall thickness, making the cross-sectional shape of each spiral tubular body 1 in the spiral tubular matrix an Archimedean spiral; constructing a spiral tubular matrix model based on the Archimedean spiral equation, and optimizing the equation parameters of the spiral tubular matrix by using a genetic algorithm; taking the minimum fitness value of the spiral tubular matrix when using different equation parameters as an optimization target; during the optimization process, for a set of equation parameters selected by the genetic algorithm, using finite element software to calculate the fitness value of the spiral tubular matrix corresponding to the set of equation parameters, combining numerical simulation with the genetic algorithm, and optimizing the equation parameters of the spiral tubular matrix to obtain the optimal geometric equation parameters of the spiral tubular body 1.

[0109] The optimization method of the adjustable acoustic metamaterial system for achieving ventilation noise reduction provided by the present invention optimizes the parameters of the equation by combining simulation calculation and genetic algorithm. In the fitness function, the noise reduction effect and ventilation rate of the structure are comprehensively considered, aiming to achieve a reasonable balance between the noise reduction effect and the ventilation effect. In order to further improve the noise reduction effect, porous media are introduced into the structure to increase the dissipation of sound energy.

[0110] In order to improve the flexibility of the structure, the present invention introduces a reconfigurable modular design so that the structure can be adjusted and optimized according to actual needs.

[0111] In a preferred embodiment of the adjustable acoustic metamaterial system for achieving ventilation noise reduction of the present invention, a row of spiral tubular matrix or a column of spiral tubular matrix is ​​arranged in the waveguide system. The adjustable acoustic metamaterial system can be connected to the speaker 3.

[0112] The method of the present invention is based on the Archimedean spiral equation, and the number of columns of the spiral tubular matrix can be 1, that is, F = 1. When the structural parameters of the spiral tubular matrix model with E = 1 or F = 1 are optimized by using a genetic algorithm, the equation parameters of the spiral tubular matrix model are optimized by using a genetic algorithm, and the following single spiral tubular monomer cross-section two-dimensional model is constructed by using the Archimedean spiral polar coordinate equation:

[0113] ρ=α+βθ=α+β(θ1-θ0);

[0114] Assume: The frequency range of the acoustic optimization band is [f down , f up ]; f down To optimize the lowest frequency in the band, f up To optimize the highest frequency in the frequency band; in [f down , f up ] 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 frequency band, F oup is the highest frequency in the main optimized frequency band; ψ is the sparseness rate of the spiral tubular matrix; ψ up is the upper limit of the sparsity rate of the helical tubular matrix; ψ down is the lower limit of the sparsity rate of the helical tubular matrix arrangement;

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

[0116] Based on the two-dimensional model of the monomer cross section of a single helical tubular body, a helical tubular matrix model is generated by COMSOL simulation software;

[0117] The objective function of the helical tube matrix model is set as follows:

[0118]

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

[0120] When the frequency is [f odown , f oup ] range T 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] Where:

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

[0124] q1, q2, and q3 are all weighting factors, where q1 is 0.8, q2 is 0.1, and q3 is 0.1;

[0125] θ is the polar angle, which represents the total number of degrees that the Archimedean spiral rotates;

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

[0127] θ1 is the polar angle at which the Archimedean spiral ends;

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

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

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

[0131] t represents the thickness of the wall of the spiral tube 1

[0132] i is the discrete frequency point number;

[0133] n r is the number of all discrete frequency points except the main optimized frequency band;

[0134] T i The frequency corresponding to the ith discrete frequency point belongs to [f down , f up ] and does not belong to [f odown , f oup ]The transmission coefficient under the condition of oi The frequency corresponding to the ith discrete frequency point belongs to [f odown , f oup ]The transmission coefficient under the condition of

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

[0136] The minimum fitness value of the helical tubular matrix model is taken as the goal of the model; the minimum fitness value of the helical tubular matrix model is obtained by optimizing the genetic algorithm.

[0137] After the single spiral structure is designed, it is rotated 180° around the origin to form a centrally symmetrical structure. The optimized geometric equation parameters are input into the COMSOL simulation software for simulation verification to obtain the final ventilation and noise reduction metamaterial structure.

[0138] In order to ensure that the structure has a noise reduction effect, it is considered that a too large sparseness rate will weaken the resonance effect of the structure, thereby resulting in the loss of noise reduction effect, while a too small sparseness rate is insufficient to provide sufficient ventilation area. Therefore, a strict limit is imposed on the sparseness rate, mainly to optimize the transmission coefficient T within the frequency. i is set to less than 0.2.

[0139] See also Fig.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 the best equation parameters.

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

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

[0143] In order to achieve the low-frequency noise reduction effect, the optimization frequency of the present invention is set in the range of 300-1100Hz, and the main optimization frequency is set in the range of 600-1100Hz. Through genetic algorithm and numerical simulation optimization, under the set fitness function, the following optimization results are obtained:

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

[0145] The optimization results are verified by finite element calculation and the transmission curve is drawn, such as Figure 8 , Fig. 9 It can be observed that in the range of 546-1575Hz, the transmission coefficient of the structure is less than 0.2, showing a good noise reduction effect.

[0146] Analyze the optimization results and select continuous θ0 for transmission calculation, such as Fig.10 As shown in Figure 2, the results show that when θ0 changes, the noise reduction band of the structure will shift significantly. Based on this phenomenon, an adjustable ventilation noise reduction structure can be realized.

[0147] The cross-sectional shape of the helical tubular body 1 is a double Archimedean spiral, which is a centrally symmetrical structure with the origin as the center, consisting of two helical tubular bodies 1 with a single Archimedean spiral cross-sectional shape.

[0148] On the Archimedean spiral corresponding to the cross section of the spiral tubular body 1, multiple nodes corresponding to different polar angles are set to divide the single Archimedean spiral into K segments, and the tube wall of the spiral tubular body 1 with a cross section shape of g Archimedean spirals is vertically cut into g*K tube segments.

[0149] When g = 1 and K = 4, the cross section of the equivalent spiral tubular body 1 has only a single Archimedean spiral; see Figure 5 , set three polar angle nodes of a single Archimedean spiral at 1.7, 4.5 and 5.1 respectively; set: θ 01 Represents the polar angle corresponding to the first node on a single Archimedean spiral; θ 02 Represents the polar angle corresponding to the second node on a single Archimedean spiral; θ 03 represents 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. Then one Archimedean spiral is divided into four sections, and the tube wall of the spiral tubular body 1 with a cross-sectional shape of one Archimedean spiral is vertically cut into four tube segments. The four tube segments are: tube segment 1-1 with a starting polar angle of 0, tube segment 1-2 with a starting polar angle of 1.7, tube segment 1-3 with a starting polar angle of 4.5, and tube segment 1-4 with a starting polar angle of 5.1.

[0150] When g=2 and K=4, the cross section of the spiral tubular body 1 is equivalent to having two Archimedean spirals; three polar angle nodes are set at 1.7, 4.5 and 5.1 respectively on the two Archimedean spirals; then a single Archimedean spiral is divided into four sections, and the wall of the spiral tubular body 1 with a cross section in the shape of two Archimedean spirals is correspondingly vertically cut into eight tube segments.

[0151] In order to fix these pipe segments, a fixed base 4 is introduced outside the pipe segment, and a base 4 for fixing the pipe segment is set; according to the requirements of the starting polar angle of the Archimedean spiral, the corresponding pipe segment is detachably installed on the base 4 to achieve the adjustment of the starting polar angle of the Archimedean spiral of the spiral tubular body 1.

[0152] Taking the case where the cross section of the spiral tubular body 1 has only a single Archimedean spiral as an example, the method for adjusting the starting polar angle of the Archimedean spiral of the spiral tubular body 1 is described;

[0153] The pipe wall is vertically cut into 4 pipe segments; the starting polar angles of the 4 pipe 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 pipe segments corresponding to different θ0 can be installed on the base 4 to realize the adjustment of the starting polar angle of the Archimedean spiral of the spiral tubular body 1.

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

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

[0156] The base 4 is provided with a slot 5 in the shape of a double Archimedean spiral for inserting the pipe segment. During the manufacturing process, the contour of the base 4 structure reserves a gap of 0.1 to 0.2 mm between the two side walls of the slot 5 and the pipe segment. The discrete pipe segments are placed in the base 4 one by one, and fixed by means such as adhesive, etc., so that the change of θ0 can be realized, thereby realizing the frequency modulation function, such as Fig.11 shown.

[0157] In order to conduct experimental verification, this experiment made a waveguide system. The cross section of the waveguide system is rectangular. The outside is made of acrylic plate (polymethyl methacrylate) with a thickness of 10mm to simulate the hard boundary of the sound field. The surrounding is made of sound-absorbing material (melamine). The overall size of the waveguide system is 1500mm long × 500mm wide × 100mm high. The experimental device is placed in the anechoic chamber. The overall experimental device is as follows Figure 1 shown.

[0158] In order to suppress the transmission peak caused by structural resonance and absorb high-frequency sound waves, the cavity between the walls of the spiral tubular body 1 is filled with a porous material 6, and the porous material 6 can be made of a porous material made of melamine. Figure 3 Finally, place it in the same Figure 1 The transmission test is carried out in the waveguide shown in the figure. The test results are shown in Fig. 9 The experimental results are basically consistent with the simulation results, and it can be observed that the high-frequency transmission has an obvious trend of being suppressed.

[0159] The transmission test of the helical tubular monomer in the waveguide system was carried out at three specific θ0. The results are shown in Fig.11 It can be observed that the experimental results are basically consistent with the simulation results, and with the change of θ0, the noise reduction frequency of the structure shifts significantly.

[0160] The embodiments described above are only used to illustrate the technical ideas and features of the present invention, and their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. The patent scope of the present invention cannot be limited only by this embodiment, that is, any equivalent changes or modifications made to the spirit disclosed by the present invention still fall within the patent scope of the present invention.

Claims

1. An optimization method for an adjustable acoustic metamaterial system for achieving ventilation noise reduction, characterized in that: A spiral tubular matrix is ​​set; the cross-sectional shape of each spiral tubular body in the spiral tubular matrix is ​​an Archimedean spiral; a spiral tubular matrix model is constructed based on the Archimedean spiral equation, and the equation parameters of the spiral tubular matrix are optimized by using a genetic algorithm; the minimum fitness value of the spiral tubular matrix when different equation parameters are used is taken as an optimization target; During the optimization process, for a set of equation parameters selected by the genetic algorithm, the finite element software is used to calculate the fitness value of the helical tubular body matrix corresponding to the set of equation parameters. The numerical simulation is combined with the genetic algorithm to obtain the optimal geometric equation parameters of the helical tubular body by optimizing the equation parameters of the helical tubular body matrix.

2. The optimization method of the adjustable acoustic metamaterial system for achieving ventilation noise reduction according to claim 1, characterized in that: The number of rows or columns of the helical tubular matrix is ​​1. When the genetic algorithm is used to optimize the equation parameters of the helical tubular matrix model, the Archimedean spiral polar coordinate equation is used to construct the following single helical tubular monomer cross-section two-dimensional model: ρ=α+βθ=α+β(θ1-θ0); Assume: The frequency range of the acoustic optimization band is [f down ,f up ]; f down To optimize the lowest frequency in the band, f up To optimize the highest frequency in the frequency band; in [f down ,f up ] 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 is the lowest frequency in the main optimization band, f oup is the highest frequency in the main optimized frequency band; ψ is the sparseness rate of the spiral tubular matrix; ψ up The upper limit of the sparsity rate of the helical tubular matrix arrangement; ψ down is the lower limit of the sparsity rate of the helical tubular matrix arrangement; Let a and b be intermediate variables, let a=2(α+βθ1), let b=(a+2t) / (1-ψ); Based on the two-dimensional model of the monomer cross section of a single helical tubular body, a helical tubular matrix model is generated by COMSOL simulation software; The objective function of the helical tube matrix model is set as follows: The constraints for setting the helical tube matrix model are as follows: When the frequency is [f odown ,f oup ] range T oi <0.2; And: α=[1,10], β=[1.27,5], θ0=[0,π], θ1=[1.5π,7π], ψ=[0.1,0.3]; Where: band r is a penalty factor, which is used to constrain the transmission coefficient of any point in the main optimization frequency band to be no greater than 0.

2. If the transmission coefficient of all points in the main optimization frequency band is ≤ 0.2, then the band r =1; if there is a point with a transmission coefficient > 0.2 in the main optimized frequency band, then the band r =10; q1, q2, and q3 are all weighting factors, where q1 is 0.8, q2 is 0.1, and q3 is 0.1; θ is the polar angle, which represents the total number of degrees that the Archimedean spiral rotates; θ0 is the starting polar angle of the Archimedean spiral; θ1 is the polar angle at which the Archimedean spiral ends; ρ is the distance from the point on the Archimedean spiral to the center of the polar coordinates; α is the distance from the point on the Archimedean spiral to the center of the polar coordinate when θ0 is equal to 0; β is the growth rate of the Archimedean spiral radius; t represents the thickness of the wall of the spiral tube 1 i is the discrete frequency point number; n r is the number of all discrete frequency points except the main optimized frequency band; T i The frequency corresponding to the ith discrete frequency point belongs to [f down ,f up ] and does not belong to [f odown ,f oup ]The transmission coefficient under the condition of; T oi The frequency corresponding to the ith discrete frequency point belongs to [f odown ,f oup ]The transmission coefficient under the condition of; Fitness is the fitness of the helical tubular matrix model.

3. The optimization method of the adjustable acoustic metamaterial system for achieving ventilation noise reduction according to claim 2, characterized in that: Using COMSOL finite element calculation software, a 1-row*1-column spiral tubular matrix finite element model is established, and the spiral tubular matrix finite element model is divided into six sequentially connected regions, namely the first region to the sixth region, among which the first and fifth regions are sound absorption boundaries, and perfectly matched layers are used; the second region is the sound wave incident region, and a plane wave background pressure field is used, and the pressure amplitude is set to 1Pa; the third region is the spiral tubular body area, and the fourth region is the sound wave transmission area, and the transmission coefficient in this region is calculated.

4. The optimization method of the adjustable acoustic metamaterial system for achieving ventilation noise reduction according to claim 1, characterized in that: COMSOL numerical simulation and MATLAB parallel computing are used for genetic algorithm optimization.

5. The optimization method of the adjustable acoustic metamaterial system for achieving ventilation noise reduction according to claim 1, characterized in that: The cross-sectional shape of the spiral tubular body is a double Archimedean spiral line shape, which is a centrally symmetrical structure with the origin as the center, and is composed of two spiral tubular bodies whose cross-sectional shapes are single Archimedean spiral lines.

6. The optimization method of the adjustable acoustic metamaterial system for achieving ventilation noise reduction according to claim 1, characterized in that: On the Archimedean spiral corresponding to the cross section of the spiral tubular body, a plurality of nodes corresponding to different polar angles are arranged, and a single Archimedean spiral is divided into K segments. Correspondingly, the tube wall of the spiral tubular body having a cross section in the shape of g Archimedean spirals is vertically cut into g*K tube segments, and a base for fixing the tube segments is arranged; according to the requirements of the starting polar angle of the Archimedean spiral, the corresponding tube segments are detachably installed on the base, so as to realize the adjustment of the starting polar angle of the Archimedean spiral of the spiral tubular body.

7. The optimization method of the adjustable acoustic metamaterial system for achieving ventilation noise reduction according to claim 7, characterized in that: A slot in the shape of a double Archimedean spiral for inserting a pipe piece is arranged on the base.

8. An adjustable acoustic metamaterial system for achieving ventilation noise reduction, characterized in that: The system is prepared by using the optimization method of the adjustable acoustic metamaterial system for achieving ventilation noise reduction as described in any one of claims 1 to 8.

9. A device for realizing an optimization method of an adjustable 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, implement the method steps of the method for optimizing the adjustable acoustic metamaterial system for ventilation noise reduction as described in any one of claims 1 to 8.

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