Sound absorber based on Archimedes spiral curled acoustic metamaterial and preparation method

Abstract

The invention discloses a sound absorber based on an Archimedes spiral curled acoustic metamaterial and a preparation method, the sound absorber comprises a sound absorption metamaterial cell element, a sound absorption channel is formed in the sound absorption metamaterial cell element, the sound absorption channel vertically penetrates through the sound absorption metamaterial cell element in the z-axis direction, the sound absorption channel is a spiral channel on the xy two-dimensional section, and the spiral channel is a spiral channel. One end of the spiral channel is opened in the side face of the sound absorption metamaterial cell element, the other end of the spiral channel is a blind end located in the center of the sound absorption metamaterial cell element, and the spiral channel is composed of two Archimedes spiral curves. According to the invention, a brand new sound absorption mechanism is adopted, the problems of strong dispersion and narrow bandwidth which are difficult to solve by a conventional resonance type structure are solved, and effective sound absorption (more than 0.5) of a broadband frequency band (2000Hz) can be realized in a range of 0-6000Hz.

Description

Technical Field

[0001] The present invention belongs to the technical field of sound absorption and noise reduction, and in particular relates to a sound absorber based on Archimedean spiral curled acoustic metamaterial and a preparation method thereof. Background Art

[0002] With the acceleration of urban development, urban industrial noise, traffic noise, and noise from elevators, transformers, central air conditioners and other sources that are closely related to life are increasing. At present, there is an urgent need to develop and apply compact low-frequency, broadband materials or structures to meet the growing demand for noise reduction. Traditional noise reduction methods, such as porous materials, perforated structures, acoustic blankets with mass interlayers, and gradient refractive index materials, have been widely used in the prevention of noise pollution. Although these methods can better handle noise in the medium and high frequency range, their use scenarios are very limited due to the need for a large thickness. The concept of metamaterials (metasurfaces) derived from electromagnetics has been extended to acoustic research, providing possibilities for modulating reflected and transmitted sound waves, acoustic invisibility, etc. The emergence of metamaterials has attracted widespread attention in the field of noise reduction because they can achieve almost perfect low-frequency absorption at subwavelength sizes. Among various metamaterial designs, spatial curled metamaterials have attracted widespread attention because they can achieve low-frequency absorption at deep subwavelength thicknesses. This excellent absorption performance is attributed to various mechanisms, including local resonance, negative equivalent material properties and zero equivalent material properties, critical coupling, FP resonance, and quarter-wave resonance. However, despite their near-perfect absorption through thickness, acoustic metamaterials generally suffer from strong dispersion and narrow bandwidth due to local resonances.

[0003] The invention patent application with application number "CN202410321317.9" ​​and name "New spiral sound-absorbing and sound-insulating metamaterial structure and its use method" discloses a spiral sound-absorbing and sound-insulating structure; the sound-absorbing and sound-insulating structure includes a bottom plate, a rectangular cross, and 4 spiral columns. The structure is based on a square lattice metamaterial with orthogonal rectangles as the basic prototype, with the center of the square lattice as the coordinate origin. Each of the four quadrants is provided with a spiral, and the adjacent spirals differ by 90 degrees. By changing the structural parameters of the spiral, different sound absorption and sound insulation requirements of the metamaterial can be met. The new spatial spiral sound-absorbing and sound-insulating metamaterial structure provided by the invention is novel and simple, small and light, and has good sound absorption and sound insulation performance within 100-2500Hz. Although this patent has a suppressive effect on medium and low frequency noise, the single sound absorption peak is narrow, and the effective sound absorption frequency band of a single sound absorption peak is less than 500Hz; its structure is connected front to back, which will cause sound energy leakage and affect the sound absorption effect; although the use of a double-layer structure can increase sound energy loss and broaden the bandwidth, it will also increase the thickness of the structure exponentially, and the scope of application is limited, making it difficult to put into practical use.

[0004] The invention patent application with application number "CN202010617443.0" and titled "A sound-absorbing metamaterial with a double-helix curled space and a preparation method thereof" discloses a curled space sound absorption structure; it includes a plurality of sound-absorbing metamaterial units, and the plurality of said sound-absorbing metamaterial units form an array, the sound-absorbing metamaterial unit includes a micro-perforated plate, a double-helix curled structure and a back plate arranged from top to bottom, the double-helix curled structure includes a partition, the partition is arranged in a double-helix form, and a double-helix curled space is formed, the double-helix curled space includes a spiral first sound channel and a second sound channel, the micro-perforated plate is provided with two micro-holes, and the two micro-holes are respectively connected to the first sound channel and the second sound channel, which effectively widens the sound absorption frequency range and achieves a more ideal sound absorption effect. Although this structure produces a higher sound absorption peak at low frequencies, its frequency band is too narrow to achieve a broadband sound absorption effect for different frequencies. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a sound absorber based on Archimedean spiral curled acoustic metamaterial and a preparation method thereof in view of the above-mentioned existing deficiencies.

[0006] In order to achieve the above technical objectives, the technical solution adopted by the present invention is:

[0007] A sound absorber based on an Archimedean spiral curled acoustic metamaterial comprises a sound absorbing metamaterial cell, in which a sound absorbing channel is provided, the sound absorbing channel penetrates the sound absorbing metamaterial cell up and down in the z-axis direction, and is a spiral channel in an xy two-dimensional cross section, one end of the spiral channel opens at a side surface of the sound absorbing metamaterial cell, and the other end is a blind end located at the center of the sound absorbing metamaterial cell, and the spiral channel is a channel composed of two Archimedean spiral curves.

[0008] To optimize the above technical solutions, the specific measures taken also include:

[0009] The above-mentioned sound-absorbing metamaterial cell is made of rigid material.

[0010] The definition of two Archimedean spiral curves is as follows:

[0011]

[0012] r2=a2+bθ,0≤θ≤-π+2kπ

[0013] Among them, r1 is the first Archimedean spiral curve, r2 is the second Archimedean spiral curve, a1, a2, a b are all constants, θ is the polar angle, and k is a positive integer.

[0014] The dimensions of the above-mentioned sound-absorbing metamaterial cell in the xyz-axis direction are 30 mm-50 mm.

[0015] The length of the spiral channel waveguide is expressed as follows, and the value is an odd integer multiple of one quarter of the working wavelength:

[0016]

[0017] h is the length of the spiral channel waveguide, and s is the cross-sectional size of the spiral channel.

[0018] The number of the above-mentioned sound absorbing metamaterial cells is multiple, and the sound absorbing metamaterial cells are arranged in an array.

[0019] The outer surface of the sound absorbing metamaterial cell is pasted with a porous sound absorbing medium.

[0020] A method for preparing a sound absorber based on Archimedean spiral curled acoustic metamaterial comprises the following steps:

[0021] Step 1: Design and determine the size of the sound absorbing metamaterial cell;

[0022] Step 2: Determine the parameters and value ranges of the two Archimedean spiral curves of the sound-absorbing metamaterial cell, construct the shape of the xy two-dimensional plane of the sound-absorbing metamaterial cell, and then stretch it in the z direction to complete the construction of the sound-absorbing metamaterial cell model;

[0023] Step 3: construct an air domain model for the sound-absorbing metamaterial cell model, add a background sound field to the air domain model to simulate the incident sound wave, add a perfect matching layer to simulate the process of an infinite sound field absorbing the reflected sound wave, and calculate the sound absorption coefficient of the sound-absorbing metamaterial cell model;

[0024] Step 4: Change the parameters and value ranges of the two Archimedean spiral curves of the sound-absorbing metamaterial cell, repeat steps 2-3, and obtain a database of the sound absorption coefficient with respect to the parameters of the Archimedean spiral curve;

[0025] Step 5: According to the actual sound absorption requirements, appropriate Archimedean spiral curve parameters are selected from the database, and the sound absorption metamaterial cell model corresponding to the Archimedean spiral curve parameters is printed and prepared by 3D printing technology.

[0026] In step three, the air domain model is constructed using UG 3D drawing software, and the air domain model is imported into COMSOL Multiphysics software. A background sound field is added to simulate the incident sound wave, and a perfectly matched layer is added to simulate the process of an infinite sound field absorbing reflected sound waves. The MATLAB precise solution is used for calculation to obtain the sound absorption coefficient of the sound-absorbing metamaterial cell model.

[0027] In step five, the sound-absorbing metamaterial cell model corresponding to the Archimedean spiral curve parameters is exported into a three-dimensional STL format, and is prepared by photocuring 3D printing using photosensitive resin as a raw material.

[0028] The beneficial effects of the present invention are:

[0029] (1) The present invention adopts a new sound absorption mechanism, which solves the problems of strong dispersion and narrow bandwidth that have been difficult to solve in resonant structures. It can achieve effective sound absorption (above 0.5) in a wide frequency band (2000Hz) within the range of 0-6000Hz.

[0030] (2) Since the spiral parameters of the present invention are adjustable, the sound absorption performance of the structure can be quickly predicted through the established theoretical model, so it has good engineering adaptability and can be used for noise control in different environments.

[0031] (3) Since the sound absorption design method of the present invention is supported by corresponding theories and simulation results, it has strong scalability and broad design space in future designs.

[0032] (4) Since the present invention has a simple structure, the production cycle is short, the design effect is significant, and it has high practical engineering application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of an Archimedean spiral curled sound absorbing metamaterial array;

[0034] Figure 2 This is a schematic diagram of the Archimedean spiral curled sound-absorbing metamaterial cell model;

[0035] Figure 3 It is a schematic diagram of the xy two-dimensional plane structural parameters of the sound-absorbing metamaterial cell;

[0036] Figure 4 It is a schematic diagram of the theoretical model based on the transfer matrix method;

[0037] Figure 5 is the single cell sound absorption curve α (theoretical and simulation results).

[0038] The meanings of the symbols in the attached drawings are: 1. Sound-absorbing metamaterial cell; 2. Sound-absorbing channel. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application is described and illustrated below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application. Based on the embodiments provided in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present application.

[0040] Obviously, the drawings described below are only some examples or embodiments of the present application. For ordinary technicians in this field, the present application can also be applied to other similar scenarios based on these drawings without creative work. In addition, it can also be understood that although the efforts made in this development process may be complicated and lengthy, for ordinary technicians in this field related to the content disclosed in this application, some changes in design, manufacturing or production based on the technical content disclosed in this application are just conventional technical means, and should not be understood as insufficient content disclosed in this application.

[0041] Reference to "embodiments" in this application means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those of ordinary skill in the art that the embodiments described in this application may be combined with other embodiments without conflict.

[0042] Unless otherwise defined, the technical terms or scientific terms involved in this application should be understood by people with ordinary skills in the technical field to which this application belongs. The words "one", "a", "a", "the" and the like involved in this application do not indicate a quantitative limitation, and may represent the singular or plural. The terms "include", "comprise", "have" and any of their variations involved in this application are intended to cover non-exclusive inclusions; for example, a process, method, system, product or device that includes a series of steps or units (units) is not limited to the listed steps or units, but may also include steps or units that are not listed, or may also include other steps or units inherent to these processes, methods, products or devices. The words "connect", "connected", "coupled" and the like involved in this application are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The "multiple" / "several" involved in this application refers to two or more. "And / or" describes the association relationship of associated objects, indicating that there can be three relationships, for example, "A and / or B" can mean: A exists alone, A and B exist at the same time, and B exists alone. The character " / " generally indicates that the objects before and after are in an "or" relationship. The terms "first", "second", "third", etc. involved in this application are only used to distinguish similar objects and do not represent a specific ordering of the objects.

[0043] refer to Figure 1 , Figure 2 , Figure 3The present invention provides a sound-absorbing metamaterial based on Archimedean spiral curling. The sound-absorbing metamaterial is designed to address the problems of narrow frequency band and strong dispersion of traditional resonant sound-absorbing structures. It adopts a spiral curling structure without a resonant cavity, and the sound waves are directly incident on the curled waveguide. Compared with traditional methods, it has better impedance matching characteristics and broadband sound absorption characteristics, and is more likely to meet practical applications.

[0044] Sound absorbing metamaterial cell 1, such as Figure 2 and Figure 3 As shown, θ1 and θ2 are the polar angles of the two Archimedean spiral curves, L and H are the thickness and height of the sound absorbing cell, respectively. The structure shown has symmetry along the z-axis, so we only consider the two-dimensional cross-section about xy, and the incident direction of the sound wave is along the negative direction of the x-axis. In an Archimedean spiral curled unit, a curled sound absorbing channel 2 is composed of two Archimedean spiral curves. The sound wave is directly incident from the x-direction. Its acoustic model can be equivalent to the combination of a waveguide with a gradually changing cross-section and a waveguide with a constant cross-section. When the sound wave is incident on the sound absorbing metamaterial cell, it can be considered as a plane wave. The cell sound absorption coefficient can be determined by the surface impedance of the structure. The surface impedance can be obtained by a theoretical model based on the transfer matrix method, such as Figure 4 . Figure 4 (a) is the air domain after segmentation, 1st-9th are the domain numbers, h1-h7 are the thickness of each domain, z1-z9 are the impedance of each domain boundary in the direction of acoustic wave incidence, Figure 4 (b) is the equivalent model for the irregular air domain. After the sound wave enters the spiral channel, it excites FP resonance at a specific frequency. Due to the existence of viscous loss between the waveguide and the air medium, the sound energy is dissipated as internal energy and disappears, and the structure achieves the effect of sound absorption.

[0045] The material of the sound-absorbing metamaterial cell 1 is a rigid material.

[0046] The two Archimedean curves are defined as follows:

[0047]

[0048] r2=a2+bθ,0≤θ≤-π+2kπ

[0049] The dimensions of the structure in the x, y, and z directions are d x d y d z , the value is 30mm-50mm.

[0050] The curled channel waveguide length is expressed as follows, where the value is an odd integer multiple of one quarter of the working wavelength:

[0051]

[0052] h is the length of the curled channel, and s is the cross-sectional size of the channel.

[0053] According to actual use needs, sound-absorbing cells with different geometric parameters are arrayed, or porous sound-absorbing media are attached to the surface of the structure to achieve sound absorption in a wider frequency range.

[0054] The following is a further detailed description of the embodiments and sound absorption mechanism of the invention:

[0055] First, determine the external dimensions of the structure, which will directly affect the frequency and bandwidth of sound absorption. The overall dimensions of this example are 30mm*30mm*30mm. The overall shape of the structure is a hexahedron, and the material is rigid. It is assumed that it meets the hard sound field boundary conditions, and the sound source frequency is lower than the cutoff frequency of the waveguide.

[0056] Secondly, determine the parameters and value ranges of the two Archimedean spiral curves so that the spiral curling channel can make full use of the structural space. a1 is 0, a2 is 1, b1 and b2 are 0.9, and k is 1. Then use discrete line segments to connect all the curves.

[0057] Finally, after constructing the shape of the two-dimensional plane, stretch it in the z direction to complete the construction of the final model.

[0058] The designed model is constructed using UG 3D drawing software. When used for actual manufacturing, the corresponding structure, partition and back panel are directly constructed, and the designed model can be obtained by performing Boolean operations and summing them. When used for numerical simulation to verify its sound absorption performance, only the air domain model needs to be constructed.

[0059] The air domain model constructed by UG was imported into COMSOL Multiphysics software, and a background sound field was added to simulate the incident sound wave. A perfectly matched layer was added to simulate the process of an infinite sound field absorbing reflected sound waves. The material of the constructed model was air, and the complex sound velocity was used to consider the influence of damping. A theoretical model was established, and the MATLAB exact solution was used for calculation to obtain the sound absorption coefficient of the structure.

[0060] Figure 5 The curve of the sound absorption coefficient under this parameter, the black solid line is the calculation result of the simulation, and the red dashed line is the calculation result of the theoretical model. The two are in good agreement. It can be seen that there are three sound absorption peaks in the range of 0-6000Hz, and the maximum sound absorption coefficient exceeds 0.9. Change the Archimedean spiral parameters and continue the simulation to obtain the database of the sound absorption coefficient curve about the spiral parameters. Select the size parameters required by actual needs, follow the above steps to establish the sound absorption metamaterial model and export it into a three-dimensional STL format, use photosensitive resin as the raw material, and use light-curing 3D printing technology to prepare and shape it.

[0061] The above are only preferred embodiments of the present invention. The protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims

1. A sound absorber based on Archimedean spiral curled acoustic metamaterial, characterized by: The invention comprises a sound absorbing metamaterial cell (1), wherein a sound absorbing channel (2) is provided in the sound absorbing metamaterial cell (1), wherein the sound absorbing channel (2) penetrates the sound absorbing metamaterial cell (1) vertically in the z-axis direction, and is a spiral channel in the xy two-dimensional cross section, wherein one end of the spiral channel opens at the side of the sound absorbing metamaterial cell (1), and the other end is a blind end located at the center of the sound absorbing metamaterial cell (1), and the spiral channel is a channel composed of two Archimedean spiral curves.

2. The sound absorber based on the Archimedean spiral curled acoustic metamaterial according to claim 1, characterized in that: The sound absorbing metamaterial cell (1) is made of rigid material.

3. The sound absorber based on the Archimedean spiral curled acoustic metamaterial according to claim 1, characterized in that: The definition of two Archimedean spiral curves is as follows: r2=a2+bθ,0≤θ≤-π+2kπ Among them, r1 is the first Archimedean spiral curve, r2 is the second Archimedean spiral curve, a1, a2, a b are all constants, θ is the polar angle, and k is a positive integer.

4. The sound absorber based on the Archimedean spiral curled acoustic metamaterial according to claim 1, characterized in that: The dimensions of the sound-absorbing metamaterial cell (1) in the xyz-axis direction are 30 mm to 50 mm.

5. The sound absorber based on Archimedean spiral curled acoustic metamaterial according to claim 3, characterized in that: The length of the spiral channel waveguide is expressed as the following formula, which is an odd integer multiple of one quarter of the working wavelength: h is the length of the spiral channel waveguide, and s is the cross-sectional size of the spiral channel.

6. The sound absorber based on the Archimedean spiral curled acoustic metamaterial according to claim 5, characterized in that: The number of the sound absorbing metamaterial cells (1) is multiple, and the sound absorbing metamaterial cells (1) are arranged in an array.

7. The sound absorber based on Archimedean spiral curled acoustic metamaterial according to claim 5, characterized in that: The outer surface of the sound absorbing metamaterial cell (1) is pasted with a porous sound absorbing medium.

8. The method for preparing a sound absorber based on Archimedean spiral curled acoustic metamaterial according to claim 5, characterized in that: The following steps are involved: Step 1: Design and determine the size of the sound absorbing metamaterial cell (1); Step 2: Determine the parameters and value ranges of the two Archimedean spiral curves of the sound absorbing metamaterial cell (1), construct the shape of the xy two-dimensional plane of the sound absorbing metamaterial cell (1), and then stretch it in the z direction to complete the construction of the sound absorbing metamaterial cell model; Step 3: construct an air domain model for the sound-absorbing metamaterial cell model, add a background sound field to the air domain model to simulate the incident sound wave, add a perfect matching layer to simulate the process of an infinite sound field absorbing the reflected sound wave, and calculate the sound absorption coefficient of the sound-absorbing metamaterial cell model; Step 4: changing the parameters and value ranges of the two Archimedean spiral curves of the sound-absorbing metamaterial cell (1), repeating steps 2-3, and obtaining a database of the sound absorption coefficient with respect to the parameters of the Archimedean spiral curve; Step 5: According to the actual sound absorption requirements, appropriate Archimedean spiral curve parameters are selected from the database, and the sound absorption metamaterial cell model corresponding to the Archimedean spiral curve parameters is printed and prepared by 3D printing technology.

9. The method for preparing a sound absorber based on Archimedean spiral curled acoustic metamaterial according to claim 8, characterized in that: In step three, the air domain model is constructed using UG 3D drawing software, and the air domain model is imported into COMSOL Multiphysics software. A background sound field is added to simulate the incident sound wave, and a perfectly matched layer is added to simulate the process of an infinite sound field absorbing reflected sound waves. The MATLAB precise solution is used for calculation to obtain the sound absorption coefficient of the sound-absorbing metamaterial cell model.

10. The method for preparing a sound absorber based on Archimedean spiral curled acoustic metamaterial according to claim 8, characterized in that: In step five, the sound-absorbing metamaterial cell model corresponding to the Archimedean spiral curve parameters is exported into a three-dimensional STL format, and is prepared by photocuring 3D printing using photosensitive resin as a raw material.

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