Sound field distribution structure adjusted by applying frequency selective surface and design method

Abstract

The invention relates to a structure for adjusting sound field distribution by applying a frequency selective surface and a design method, and the structure comprises a substrate, the substrate is provided with a unit structure, the unit structure is circular, the size of the unit structure from the center to the edge of the substrate is gradually increased, and the shape of the unit structure gradually transits from the circular shape to the elliptical shape; according to the invention, accurate adjustment of sound waves is realized, the adaptability to multi-band sound waves is improved, and a more flexible and accurate sound field adjustment effect is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of sound field distribution, and in particular relates to a structure and a design method for adjusting sound field distribution by using a frequency selective surface. Background Art

[0002] Frequency Selective Surface (FSS) technology originated from the frequency selective control of electromagnetic waves and was first widely used in the fields of radar, communication antennas and radio wave shielding. By designing a unit structure with a specific geometric shape and arrangement, FSS can reflect, transmit or absorb electromagnetic waves, thereby achieving control over a specific frequency range. In recent years, with the development of acoustic technology, the concept of FSS has gradually been introduced into the field of sound field control. Acoustic FSS can perform similar selective control on sound waves. By adjusting the shape, size and arrangement of the unit structure, it can achieve reflection, transmission or absorption of sound waves of different frequencies. It is widely used in scenes such as architectural acoustics, acoustic barriers and noise control. The advantage of this technology lies in its high degree of customizability. By designing different geometric structures, it can meet different acoustic needs. However, the existing technology still has limitations in the precise control of sound field distribution, especially in complex acoustic environments, where it is difficult to simultaneously take into account the reflection, transmission and absorption effects of multi-band sound waves.

[0003] The existing FSS sound field control technology mainly faces several challenges. First, the control of single-frequency sound waves is relatively mature, but the existing design cannot achieve precise gradual adjustment of the sound field when controlling multi-band sound waves at the same time. Most FSS designs are based on unit structures with fixed shapes and sizes. This design works well within a specific frequency range, but its control ability is obviously insufficient when faced with a wide range of frequency changes. Secondly, the existing material selection and combination are also limited. Most designs use a single material, which makes it difficult to achieve the absorption and reflection characteristics of sound waves of different frequencies. Even if there are attempts to combine materials, the design of the transition zone is often rough, resulting in the inability to effectively control the reflection and transmission properties of sound waves. In addition, the accuracy of the manufacturing process is also a major bottleneck. The manufacture of complex geometric structures is difficult to meet the design requirements in traditional processes, which directly affects the acoustic performance of the FSS structure.

[0004] Our invention effectively solves the shortcomings of the prior art in multi-band sound wave regulation by introducing a gradient structure design and a multi-layer material combination solution. The method achieves fine regulation of the sound field by setting a unit structure of gradient shape and size on the substrate. Specifically, a small-sized circular unit structure is used in the central area of ​​the substrate to evenly reflect and transmit low-frequency sound waves, while from the center to the edge, the unit structure gradually transitions to an elliptical shape and increases in size, which can effectively regulate the directionality of high-frequency sound waves. In addition, in terms of the material selection of the substrate, the focusing, guiding and diffusion of sound waves are achieved through a gradient design from high density to low density. The introduction of a multi-layer structure further improves the accuracy of regulation, and by combining the absorption and reflection characteristics of different materials, accurate regulation of the sound field can be achieved over a wide frequency range. By superimposing multiple layers of FSS, more precise phase control and wider frequency response can be achieved. The multi-layer structure allows each layer to provide specific phase compensation, thereby achieving the required wavefront modulation. Therefore, the present invention belongs to the field of acoustic FSS, mainly solves the problem of multi-band sound wave regulation in a complex sound field environment, and provides new solutions for the fields of architectural acoustics and noise control. Summary of the invention

[0005] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0006] In view of the following technical problems in the prior art: the prior art still has limitations in the precise control of the sound field distribution, especially in complex acoustic environments, it is difficult to simultaneously take into account the reflection, transmission and absorption effects of multi-band sound waves.

[0007] To solve the above technical problems, the present invention provides the following technical solutions: a design method for adjusting the sound field distribution using a frequency selective surface, comprising: a substrate, on which a unit structure is arranged, the unit structure is circular, the size of the unit structure on the substrate gradually increases from the center to the edge, and the shape gradually transitions from circular to elliptical.

[0008] As a preferred technical solution for a design method of using a frequency selective surface to adjust the distribution of the acoustic field, the substrate is divided into a high-density area, a transition area and a low-density area from the middle to the edge.

[0009] As a preferred technical solution for a design method using a frequency-selective surface to adjust the sound field distribution, the substrate includes an inner layer, a middle layer and an outer layer, the inner layer is a high-absorption material, the middle layer is an elastic material, the outer layer is a high-reflection material, and the inner layer, the middle layer and the outer layer are fixed by an adhesive.

[0010] As a preferred technical solution for a design method of using a frequency selective surface to adjust the sound field distribution, a flexible adhesive is used between the inner layer and the middle layer, and a rigid adhesive is used between the middle layer and the outer layer.

[0011] As a preferred technical solution for a design method using a frequency selective surface to adjust the sound field distribution, the thickness of the inner layer is smaller than the thickness of the middle layer, and the thickness of the outer layer is smaller than the thickness of the inner layer.

[0012] Beneficial effects of the present invention: The present invention achieves gradual sound field regulation by designing the unit structure on the substrate to gradually increase from the center to the edge and transition from a circular shape to an elliptical shape. This design method can effectively control the propagation path and intensity of sound waves in different areas, making the distribution of the sound field more uniform and controllable. Specifically, the gradual change in the shape of the unit structure optimizes the reflection and transmission characteristics of sound waves at different frequencies, and enhances the responsiveness of the frequency selective surface to specific frequencies. Therefore, through this gradual design, not only the precise regulation of sound waves is achieved, but also the adaptability to multi-band sound waves is improved, achieving a more flexible and precise sound field regulation effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0014] Figure 1 Schematic diagram of the distribution structure of the unit structure on the substrate in the present invention;

[0015] Figure 2 This is a schematic diagram of the distribution of substrate materials in the present invention;

[0016] Figure 3 It is a schematic diagram of the layered structure of the substrate in the present invention.

[0017] Reference numerals: substrate 100 , unit structure 101 , high-density region 102 , transition region 103 , low-density region 104 , middle layer 106 , outer layer 107 , inner layer 105 . DETAILED DESCRIPTION

[0018] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings.

[0019] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0020] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0021] Secondly, the present invention is described in detail with reference to the schematic diagram. When describing the embodiments of the present invention in detail, for the sake of convenience, the cross-sectional diagrams showing the device structure will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.

[0022] Example 1

[0023] Reference Figure 1 to Figure 3 The present embodiment provides a design method for adjusting the sound field distribution by using a frequency selective surface, including a substrate 100, on which a unit structure 101 is arranged, the unit structure 101 is circular, and the size of the unit structure 101 gradually increases from the center to the edge of the substrate 100, and the shape gradually transitions from a circle to an ellipse.

[0024] This gradient design was chosen to achieve fine control of the sound field. By changing the geometric shape and size, different sound wave reflection, transmission or absorption characteristics can be achieved at different locations, thereby achieving precise control of the sound field distribution.

[0025] The basic unit structure of FSS is designed as a geometric figure with a gradual shape, such as a circle, an ellipse, a rectangle, a triangle, etc. In order to achieve a gradual effect of sound field adjustment, a geometric structure with a smooth shape transition is usually selected.

[0026] In the specific design, the unit structure in the central area is circular to achieve all-round uniform sound wave reflection and transmission characteristics; from the center to the edge, the unit structure gradually transitions to an elliptical shape, which can produce anisotropic sound wave response.

[0027] The size of the unit structure in the central area is relatively small, and the unit size gradually increases as it expands outward.

[0028] For example, suppose the unit structure in the center is a circle with a radius of $r_0=5$mm, and the gradient increases every 5mm outward. When reaching the edge, the radius of the unit structure increases to $r_n=10$mm. At the same time, the shape gradually changes from a circle to an ellipse with a ratio of major axis to minor axis of 2:1.

[0029] The unit structure is arranged radially from the center outward, and the center points of all units are located on the same axis.

[0030] This arrangement helps ensure the symmetry of the structure and the uniform propagation of sound waves. The distance between adjacent units of each unit should be precisely controlled, for example 1mm, to avoid sound wave interference between adjacent units.

[0031] The smaller size and circular structure of the central area can evenly reflect and transmit sound waves, ensuring omnidirectional propagation of low-frequency sound waves.

[0032] The gradual size and shape that expands outward gradually changes the reflection and transmission paths of sound waves, especially the directionality of high-frequency sound waves can be controlled.

[0033] Through this gradient design, the sound field can be evenly adjusted and controlled in different frequency ranges.

[0034] The substrate 100 is divided into a high-density area 102 , a transition area 103 and a low-density area 104 from the middle to the edge. The material of the transition area 103 transitions from high density to low density from the inside to the outside.

[0035] The material gradient technology is used in different areas of the FSS to control the sound wave propagation speed and absorption rate in different areas. In specific implementation, a combination of high density to low density and from hard materials to soft materials is gradually used from the center area of ​​the FSS to the outside.

[0036] This material gradient design is chosen because material properties have a significant impact on the absorption and reflection of sound waves. By controlling the gradient of the material, the focusing, guiding or diffusion effects of the sound waves can be achieved, thereby achieving complex sound field gradient adjustment.

[0037] The FSS surface adopts a gradient design that mixes multiple materials. From the center to the edge, the physical properties of the materials gradually change, such as from high density to low density, and from hard to soft.

[0038] The central area (high-density area 102) uses high-density hard materials (such as aluminum or titanium alloy) to ensure strong reflection characteristics of sound waves; the edge area (low-density area 104) uses low-density soft materials (such as foam or polyurethane) to achieve stronger sound wave absorption.

[0039] A material transition zone 103 is provided between the high-density zone 102 and the low-density zone 104 , and the material gradually transitions in this zone, for example, by mixing high-density material and low-density material to achieve a gradual change.

[0040] For example, in the area with a radius of 10 mm to 30 mm, the material gradually transitions from 100% aluminum alloy to 100% polyurethane.

[0041] The center material and the edge material transition through a gradient area, and the material composition of the gradient area is mixed in proportion. For example, the density change of the material in the transition area is linear or nonlinear distribution to achieve smooth sound wave propagation characteristics.

[0042] Using composite technology, such as metal-polymer composites, ensures that the acoustic properties of the transition area meet the design requirements while improving the mechanical stability of the structure.

[0043] High-density materials are effective at reflecting sound waves, while low-density materials help absorb and attenuate sound waves.

[0044] The gradient material distribution allows the propagation speed and absorption rate of sound waves to be precisely adjusted in different frequency ranges, thereby achieving complex sound field control effects such as focusing or diffusion of sound waves.

[0045] Furthermore, the substrate 100 includes an inner layer 105, a middle layer 106 and an outer layer 107, the inner layer 105 is a highly absorbent material, the middle layer 106 is an elastic material, the outer layer 107 is a highly reflective material, and the inner layer 105, the middle layer 106 and the outer layer 107 are fixed by an adhesive.

[0046] The FSS structure is composed of multiple layers of gradient structures, each with unique acoustic properties. The inner layer 105 is designed to absorb sound waves of a specific frequency, while the outer layer 107 is used to reflect or guide sound waves of other frequencies.

[0047] The multi-layer gradient structure design was chosen because it can provide a wider range of sound field adjustment and enable more refined sound field control. Through the different designs of each layer, frequency-selective multifunctional sound field adjustment can be achieved.

[0048] The inner layer 105 uses highly absorbent materials (such as rubber or silicone rubber) to absorb low-frequency sound waves; the middle layer 106 uses elastic materials (such as polyurethane) to guide and control the propagation path of sound waves; the outer layer 107 uses highly reflective materials (such as aluminum or nickel alloy) to reflect high-frequency sound waves.

[0049] The layers are connected by adhesives or mechanical fixings to ensure that there are no gaps between the layers and to ensure the effective transmission of sound waves between the layers.

[0050] For example, a flexible adhesive is used between the inner layer 105 and the middle layer 106 , and a rigid adhesive is used between the middle layer 106 and the outer layer 107 , so as to achieve effective connection and acoustic property transition between different layers.

[0051] The thickness of the inner layer 105 is smaller than that of the middle layer 106 , and the thickness of the outer layer 107 is smaller than that of the inner layer 105 .

[0052] The thickness and material density of each layer can be gradually changed to achieve the adjustment of sound waves of different frequencies. For example, the inner layer is 2mm thick, the middle layer is 3mm thick, and the outer layer is 1mm thick.

[0053] Through the design and combination of such layers, selective absorption, transmission and reflection of sound waves in a wide frequency range can be achieved.

[0054] The inner layer 105 highly absorbent material is designed to absorb low frequency sound waves and reduce low frequency noise.

[0055] The elastic material of the middle layer 106 is designed to change the propagation path of the sound waves and regulate the reflection and transmission of the sound waves inside the FSS structure through the elastic properties.

[0056] The highly reflective material of the outer layer 107 is designed to reflect high-frequency sound waves to prevent them from leaking out, while forming a sound wave beam within a specific frequency range.

[0057] The multi-layer structure can adjust the transmission, reflection and phase of sound waves to achieve functions such as sound wave focusing, sound insulation, sound wave beam control, etc. The multi-layer combination design ensures fine adjustment and control of sound waves over a wide frequency range, making the FSS structure suitable for a variety of complex acoustic application scenarios.

[0058] In order to realize the above-mentioned gradient structure, a precisely controlled manufacturing process, such as 3D printing technology or micro-nano processing technology, is used to manufacture complex unit structures and material combinations.

[0059] These manufacturing processes were chosen because they offer high-precision control, ensuring that the geometry, dimensions, and material properties of the gradient structures are achieved exactly as designed.

[0060] Example description:

[0061] Assume that the FSS structure is designed for a large conference hall and requires uniform distribution of sound waves and noise control in the frequency range of 1kHz to 5kHz. The design parameters are as follows:

[0062] Unit structure size and shape: Central circular unit structure, radius gradually changes from 5mm to 10mm, and the shape changes from circular to elliptical with a major axis to minor axis ratio of 2:1.

[0063] Gradual material properties: aluminum alloy is used in the center area, polyurethane foam is used in the edge area, and the material density increases from 2.7g / cm 3 0.5g / cm to the edge 3 Gradient.

[0064] Multi-layer gradient structure combination: the inner layer is rubber (thickness 2mm), the middle layer is polyurethane (thickness 3mm), and the outer layer is aluminum (thickness 1mm).

[0065] Manufacturing process: Use 3D printing and micro-nano processing technology to manufacture and process each layer of the structure, and conduct quality control and acoustic performance testing to ensure that the structure meets the design requirements.

[0066] Example 2

[0067] Design methods include:

[0068] Determine the gradient design parameters:

[0069] First, determine the target frequency range and sound field adjustment requirements of FSS, and select the appropriate unit structure size and shape gradient method based on these requirements.

[0070] Assuming that the target frequency range is 1kHz to 5kHz, according to the sound field adjustment requirements, a design is selected in which the unit structure size is smaller in the center area, larger in the edge area, and gradually transitions from circular to elliptical.

[0071] Calculate the size change of the unit structure: Use the formula d(r) = d 0 + k·r calculates the change of unit structure size with radius r. Assume that the initial center size d0 = 5 mm and the gradient coefficient k = 0.1 mm / mm.

[0072] In the range of radius r from 0 to 50 mm, the dimension d(r) gradually changes from 5 mm to 10 mm.

[0073] Use CAD software (such as SolidWorks or AutoCAD) to build a 3D model of the FSS unit. According to the calculation results, draw the unit structure from the center to the edge in sequence.

[0074] During the structural modeling process, the spacing between units (e.g. 1 mm) also needs to be considered to ensure that the sound wave reflection and transmission characteristics of each unit are not interfered with by adjacent units.

[0075] Gradual shape design: The unit structure gradually changes from a circular shape in the center to an ellipse. In the CAD model, the ratio of the major and minor axes of the ellipse gradually changes from 1:1 to 1:2.

[0076] At different radius positions, the specific major and minor axis sizes are determined to meet the requirements of the gradient design.

[0077] Design examples:

[0078] Central area (radius r = 0 to 10 mm): unit structure size d = 5 mm, circular shape.

[0079] Middle area (radius r = 10 to 30 mm): the unit structure size gradually increases to d = 8 mm, and the shape gradually transitions from circular to elliptical (major axis: minor axis = 1:1.5).

[0080] Edge area (radius r = 30 to 50 mm): unit structure size d = 10 mm, elliptical shape (major axis: minor axis = 1:2).

[0081] Select material type: Determine the acoustic wave regulation requirements of the FSS structure and select the appropriate material. For example, if the center area requires high reflectivity, choose a high-density material (such as aluminum alloy); if the edge area requires high absorptivity, choose a low-density material (such as foam or polyurethane).

[0082] Define material gradient parameters: Use the formula E(r) = E 0 (1-α·r) defines the gradual change of the elastic modulus of the material. Assume that the central initial elastic modulus E0 = 70 GPa (aluminum alloy) and the gradual change coefficient α = 0.01 GPa / mm.

[0083] During the manufacturing process, the material properties are gradually changed by changing the material mix ratio or using composite materials. For example, pure aluminum alloy is used in the center area, and polyurethane foam is gradually added to the outside until the edges are completely made of low-density materials.

[0084] Design examples:

[0085] Central area (radius r = 0 to 10 mm): the material is pure aluminum alloy, elastic modulus E = 70 GPa.

[0086] Middle area (radius r=10 to 30 mm): the material is a composite material of aluminum alloy and polyurethane foam, and the elastic modulus E gradually decreases from 70 GPa to 40 GPa.

[0087] Edge area (radius r = 30 to 50 mm): the material is pure polyurethane foam, elastic modulus E = 20 GPa.

[0088] Design and superposition of multi-layer gradient structure:

[0089] First determine the function and material of each layer. Inner layer (layer 1): designed to absorb sound waves of a specific frequency, choose a highly absorbent material (such as rubber).

[0090] Middle layer (layer 2): designed to guide sound waves of a specific frequency, and made of an elastic material (such as silicone rubber).

[0091] Outer layer (layer 3): designed to reflect sound waves of other frequencies, and a high reflectivity material (such as aluminum) is selected.

[0092] The gradient characteristics of each layer are designed: the thickness of the inner layer (layer 1) gradually increases from the center to the edge to enhance the absorption of low-frequency sound waves.

[0093] The middle layer (layer 2) maintains a uniform thickness to ensure stable propagation of sound waves within this layer.

[0094] The material of the outer layer (layer 3) becomes denser from the center to the edge to improve the reflectivity of high-frequency sound waves.

[0095] Use multi-layer simulation software (such as COMSOL Multiphysics) to simulate the acoustic field adjustment performance. Optimize the thickness, material and position of each layer through multiple iterations to ensure the best acoustic field adjustment effect within the target frequency range.

[0096] Design examples:

[0097] Inner layer (layer 1): The thickness increases from 2mm in the center to 5mm at the edge, and the material is rubber.

[0098] Middle layer (layer 2): 3 mm thick, made of silicone rubber.

[0099] Outer layer (layer 3): 1mm thick, made of aluminum, with density increasing gradually from the center to the edge.

[0100] According to the complexity and precision requirements of the FSS structure, a combination of 3D printing technology and micro-nano processing technology is selected.

[0101] First, the basic structure of FSS (such as cantilever beams and membrane structures) is manufactured using 3D printing technology to ensure the overall dimensional accuracy of the structure and the realization of complex geometric shapes.

[0102] Micro-nano processing technology is then used to perform fine processing and coating of the material surface (such as deposition of nanoscale material coatings) to ensure the material's gradual characteristics and surface smoothness.

[0103] During the manufacturing process, quality inspection is carried out after each step is completed (such as using laser interferometer to measure surface flatness and X-ray to check internal structure) to ensure that the structure and material properties meet the design requirements.

[0104] Design examples:

[0105] Print the FSS base structure using a high-precision 3D printer such as the EOS M 290 with a printing resolution of 0.01mm.

[0106] The surface nano-coating is deposited using micro-nano processing equipment (such as Raith eLINE Plus), and the coating thickness is controlled within 100nm.

[0107] Secondly, the acoustic performance of the overall structure of the design needs to be tested and calibrated. Specifically:

[0108] Install the manufactured FSS structure in the anechoic chamber to ensure that there are no other interfering sound sources in the acoustic test environment.

[0109] Acoustic test equipment such as sound intensity meters and multi-frequency sound sources are used to measure the reflectivity, absorptivity, directivity, and frequency selectivity of FSS structures.

[0110] In the frequency range of 1kHz to 5kHz, the frequency and direction of the sound source are gradually adjusted to record the sound wave reflection and absorption data at different locations.

[0111] The experimental data are then compared with the design simulation data to analyze the difference between the acoustic performance of the actual structure and the design target.

[0112] The design parameters of the FSS structure (such as unit size, material properties and stacking thickness) are adjusted according to the test results, and multiple iterations of optimization are carried out to ensure that the structure achieves the best performance.

[0113] Design examples:

[0114] At a frequency of 1 kHz, the reflectivity of the central area was measured to be 80% and the absorption of the edge area to be 60%.

[0115] According to the measurement results, the size and material combination of the unit structure in the central area are adjusted to improve the low-frequency reflection effect, while the material combination in the edge area is optimized to enhance the high-frequency absorption effect.

[0116] The size and shape gradient design determine the basic geometry of the FSS structure, which directly affects the propagation path and distribution of the sound waves.

[0117] The gradual application of material properties is based on the geometric position of the driver structure, ensuring that each driver has optimal acoustic performance within a specific frequency range.

[0118] The design and superposition of multi-layer gradient structures further refine the functional distribution of the structure and improve the adjustment accuracy of sound waves of different frequencies through layered design.

[0119] The optimization and implementation of the manufacturing process ensure that the designed gradient characteristics are accurately realized in the actual manufacturing process. Process optimization is directly related to the performance of the final product.

[0120] The acoustic performance testing and calibration of the overall structure provide feedback and improvement basis for design and manufacturing, ensuring the effectiveness and stability of the FSS structure in practical applications.

[0121] In the design method of the present invention, the rationality of character interpretation and the beneficial effects of key steps directly determine the structural performance and sound field adjustment effect. First, the key step of determining the gradient design parameters is to select the target frequency range of FSS and the sound field adjustment requirements, and to select the size and shape gradient of the unit structure in a targeted manner, thereby solving the problem of limited sound field adjustment range in traditional FSS design. For example, the selection of the target frequency range of 1kHz to 5kHz reasonably covers the important frequency bands in daily acoustic applications, and the unit structure design with a smaller center and larger edges, combined with a structure that gradually transitions from a circular shape to an elliptical shape, can effectively optimize the sound field distribution, and solve the problem of insufficient sensitivity to specific frequencies in traditional structures. This design not only enhances the reflection and absorption capabilities of sound waves of different frequencies, but also accurately controls the propagation path of sound waves, ultimately improving the accuracy and consistency of sound field adjustment.

[0122] The formula used to calculate the change in unit structure size further quantifies the change in unit structure with radius r, ensuring the controllability and scientificity of the design. For example, the initial size d0 = 5mm and the gradient coefficient k = 0.1mm / mm are set, and the unit size change under different radii is accurately determined through a mathematical model, ensuring the continuity and optimization performance of the gradient design. This calculation method can accurately adjust the design parameters according to the specific application scenario, solving the randomness and uncertainty of the gradient design in the traditional method, and ultimately ensuring the effectiveness of the sound field adjustment.

[0123] The circular to elliptical transition in the shape gradient design enhances the selectivity of FSS for different frequencies by adjusting the ratio of the major and minor axes from 1:1 to 1:2. For example, the circular unit structure in the center area reflects low-frequency sound waves better, while the elliptical structure in the edge area helps absorb high-frequency sound waves. This shape gradient design solves the problem that the traditional single-shape FSS structure is not accurate enough in responding to multi-band sound waves, and significantly improves the sound wave adjustment ability at different frequencies.

[0124] In the material selection and gradient parameter definition, a formula is used to define the gradient of the material elastic modulus so that the material properties match the geometric position of the unit structure. For example, the selection of aluminum alloy (E = 70GPa) in the center area can provide high reflectivity, while the selection of polyurethane foam (E = 20GPa) in the edge area enhances the absorption capacity. Through this material gradient design, the problem of single traditional materials and fixed performance is solved, thereby optimizing the reflection and absorption performance of sound waves in different frequency ranges and improving the adaptability of FSS structures in multi-band applications.

[0125] Finally, the design and superposition of the multi-layer gradient structure combines the absorption of the inner layer, the guidance of the middle layer and the reflection function of the outer layer, and further refines the functional distribution of the structure through layer-by-layer design. This design not only solves the problem of inaccurate regulation of sound waves of different frequencies in a single-layer structure, but also achieves precise control of sound waves of different frequency bands through the gradual change of material properties and the adjustment of thickness. For example, the gradually increasing thickness of the inner layer of rubber enhances the absorption of low-frequency sound waves, while the outer layer of aluminum material with a gradient density increases the reflectivity of high-frequency sound waves, further improving the sound field regulation effect.

[0126] The size of the unit structure set on the substrate gradually increases and transitions from a circle to an ellipse. By designing the unit structure on the substrate to gradually increase from the center to the edge and transition from a circle to an ellipse, the gradualness of the sound field adjustment is achieved. This design method can effectively control the propagation path and intensity of sound waves in different areas, making the distribution of the sound field more uniform and controllable. Specifically, the gradual change in the shape of the unit structure optimizes the reflection and transmission characteristics of sound waves at different frequencies, and enhances the responsiveness of the frequency selective surface to specific frequencies. Therefore, through this gradual design, not only the precise adjustment of sound waves is achieved, but also the adaptability to multi-band sound waves is improved, achieving a more flexible and precise sound field adjustment effect.

[0127] The density zoning design of the substrate is divided into high-density area, transition area and low-density area. The propagation characteristics of sound waves in different areas are adjusted to different degrees. The high-density area is mainly used to absorb high-frequency sound waves, the low-density area helps to reflect low-frequency sound waves, and the transition area plays a role in smooth transition between the two. This density zoning design realizes multi-level regulation of the sound field by changing the propagation path and absorption characteristics of the sound waves, which not only improves the flexibility of the sound field distribution, but also enhances the adaptability to complex sound field environments. Therefore, this design achieves the beneficial effect of optimizing the distribution of sound wave energy and reducing sound wave interference.

[0128] Multi-layer structure design: the inner layer is a highly absorbent material, the middle layer is an elastic material, and the outer layer is a highly reflective material. The multi-layer structure design significantly improves the structure's sound wave processing capabilities. The use of highly absorbent materials in the inner layer can effectively absorb sound waves in a specific frequency band, avoid unnecessary sound wave reflections, and thus reduce noise and echoes in the sound field. The elastic material in the middle layer provides better sound wave control capabilities by adjusting the propagation speed and direction of sound waves. The highly reflective material in the outer layer further enhances the reflection performance of sound waves in a specific frequency band, thereby achieving effective guidance and concentration of sound waves of a specific frequency. Through the combination and functional allocation of multi-layer materials, the structure achieves the effect of optimizing sound wave absorption, reflection, and propagation, further improving the controllability and adjustment effect of the sound field.

[0129] The use of flexible adhesives and rigid adhesives The use of flexible adhesives between the inner and middle layers provides better structural flexibility, which allows the materials to adapt to the dynamic changes of sound waves, reduces energy loss at the interface, and thus improves the overall sound wave absorption efficiency. The use of rigid adhesives between the middle and outer layers provides stronger structural stability, ensuring the accuracy and consistency of sound wave reflection. Therefore, through the selection of different adhesives, functional complementarity between materials and structural stability are achieved, and the accuracy of sound wave regulation and overall durability are enhanced.

[0130] Different thickness design of each layer The different thickness design of the inner layer, middle layer and outer layer enables the structure to treat sound waves of different frequencies differently. The thinner inner layer is more suitable for absorbing high-frequency sound waves, the thicker middle layer helps to adjust the propagation of medium and low-frequency sound waves, and the thickness of the outer layer optimizes the reflection characteristics. Through the different thickness design, accurate adjustment of sound waves of different frequency bands is achieved, thereby improving the flexibility and accuracy of the sound field distribution.

[0131] The design method of selecting the unit structure size and shape gradient mode achieves a high degree of customization of the sound field distribution by selecting the appropriate unit structure size and shape gradient mode according to the FSS target frequency range and sound field adjustment requirements. This method can adjust the geometric parameters of the unit structure according to different acoustic application scenarios to meet different frequency ranges and sound field distribution requirements. This provides a highly flexible and targeted optimization path for the design, which significantly improves the performance of FSS in different application scenarios.

[0132] Using formula to calculate the change of unit structure size with radius By using formula to accurately calculate the change of unit structure size with radius, the quantification and controllability of unit structure gradient design are realized. This method directly reflects the relationship between geometric parameters and sound field adjustment performance through mathematical models, thereby ensuring the scientificity and effectiveness of the design. This design method makes the distribution adjustment of the sound field more accurate, and can be adjusted through calculation to meet different application requirements, achieving a double improvement in design efficiency and accuracy.

[0133] Using a formula to define the gradual change of the elastic modulus of the material Using a formula to define the gradual change of the elastic modulus of the material can dynamically adjust the mechanical properties of the material according to the sound field adjustment requirements of different areas. This design method ensures that the material has different response characteristics to sound waves in different areas, and achieves more accurate control of the sound wave propagation path. Through this gradual change design of the elastic modulus, the deep coupling of material properties and sound field adjustment effects is finally achieved, making the sound field distribution more in line with the expected goals and improving the overall performance of the material and the sound wave control effect.

[0134] It will be appreciated that in the development of any actual implementation, as in any engineering or design project, numerous implementation-specific decisions may be made. Such a development effort may be complex and time-consuming, but will be a routine task of design, fabrication, and production for those of ordinary skill having the benefit of this disclosure without undue experimentation.

[0135] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A structure for adjusting the sound field distribution using a frequency selective surface, characterized in that: The invention comprises a substrate (100), wherein a unit structure (101) is arranged on the substrate (100), wherein the unit structure (101) is circular, and the size of the unit structure (101) gradually increases from the center to the edge of the substrate (100), and the shape gradually transitions from a circular shape to an elliptical shape.

2. The structure for adjusting the sound field distribution by using a frequency selective surface according to claim 1, characterized in that: The substrate (100) is divided into a high-density area (102), a transition area (103) and a low-density area (104) from the middle to the edge.

3. The structure for adjusting the sound field distribution by using a frequency selective surface according to claim 2, characterized in that: The substrate (100) comprises an inner layer (105), a middle layer (106) and an outer layer (107); the inner layer (105) is a highly absorbent material, the middle layer (106) is an elastic material, and the outer layer (107) is a highly reflective material; the inner layer (105), the middle layer (106) and the outer layer (107) are fixed by an adhesive.

4. The structure for adjusting the sound field distribution by using a frequency selective surface according to claim 3, characterized in that: A flexible adhesive is used between the inner layer (105) and the middle layer (106), and a rigid adhesive is used between the middle layer (106) and the outer layer (107).

5. The structure for adjusting the sound field distribution by using a frequency selective surface according to claim 4, characterized in that: The thickness of the inner layer (105) is smaller than the thickness of the middle layer (106), and the thickness of the outer layer (107) is smaller than the thickness of the inner layer (105).

6. A design method for adjusting the sound field distribution using a frequency selective surface, characterized in that: According to the target frequency range and sound field adjustment requirements of FSS, select the appropriate unit structure size and shape gradient method; Select appropriate materials based on the acoustic wave regulation requirements of the FSS structure; Determine the function, material and gradient characteristics of each layer to form a multi-layer structure.

7. The design method for adjusting the sound field distribution by using a frequency selective surface according to claim 6 is characterized in that: Choose the shape gradient method including: The formula d(r)=d0+k·r is used to calculate the change of unit structure size with radius r.

8. The design method for adjusting the sound field distribution by using a frequency selective surface according to claim 7 is characterized in that: Choosing the right materials includes: The gradual change of the elastic modulus of the material is defined using the formula E(r)=E0·(1-α·r).

Images