A structure and design method for applying frequency selective surfaces to regulate sound field distribution

Abstract

The application relates to a frequency-selective surface structure and a design method for adjusting sound field distribution, comprising a substrate, wherein unit structures are arranged on the substrate, the unit structures are circular, the unit structure size gradually increases from the center to the edge of the substrate, and the shape gradually transitions from a circular shape to an elliptical shape; the application not only realizes accurate adjustment of sound waves, but also improves the adaptability to multi-frequency band sound waves, and achieves a more flexible and accurate sound field adjustment effect.

Description

Technical Field

[0001] This invention belongs to the field of sound field distribution technology, specifically a structure and design method for adjusting sound field distribution using frequency-selective surface. Background Technology

[0002] Frequency Selective Surface (FSS) technology originated from the frequency-selective control of electromagnetic waves and was initially widely used in radar, communication antennas, and radio wave shielding. By designing unit structures with specific geometries and arrangements, FSSs 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 been gradually introduced into the field of sound field manipulation. Acoustic FSSs can perform similar selective manipulation of sound waves. By adjusting the shape, size, and arrangement of the unit structures, they can achieve reflection, transmission, or absorption of sound waves of different frequencies, and are widely used in architectural acoustics, acoustic barriers, and noise control. The advantage of this technology lies in its high customizability; by designing different geometries, different acoustic requirements can be met. However, existing technologies still have limitations in the precise control of sound field distribution, especially in complex acoustic environments, where it is difficult to simultaneously achieve reflection, transmission, and absorption effects for multiple frequency bands of sound waves.

[0003] Existing FSS (Fluid Sound Field Control) technologies face several challenges. First, while single-frequency sound wave control is relatively mature, current designs cannot achieve precise, gradual sound field adjustment when controlling multiple frequency bands simultaneously. Most FSS designs are based on unit structures with fixed shapes and sizes, which work well within specific frequency ranges but are significantly insufficient in controlling a wide range of frequencies. Second, existing material selection and combinations are also limited. Most designs use a single material, making it difficult to achieve the absorption and reflection characteristics of sound waves at different frequencies. Even with attempts at material combinations, the design of the transition zone is often crude, resulting in ineffective control over sound wave reflection and transmission performance. Furthermore, manufacturing precision is a major bottleneck; the fabrication of complex geometries is difficult to achieve the design requirements using traditional processes, directly impacting the acoustic performance of the FSS structure.

[0004] Our invention effectively addresses the shortcomings of existing technologies in multi-band sound wave modulation by introducing a gradient structure design and a multi-layer material combination. This method achieves precise sound field modulation by setting unit structures of varying shapes and sizes on a substrate. Specifically, the central region of the substrate uses small-sized circular unit structures to uniformly reflect and transmit low-frequency sound waves, while from the center to the edge, the unit structures gradually transition to elliptical shapes and increase in size, effectively controlling the directionality of high-frequency sound waves. Furthermore, the substrate material selection, through a gradient design from high density to low density, achieves sound wave focusing, guidance, and diffusion. The introduction of a multi-layer structure further enhances the modulation precision; by combining the absorption and reflection characteristics of different materials, precise sound field modulation can be achieved over a wide frequency range. By stacking multiple FSSs, more precise phase control and a wider frequency response can be achieved. The multi-layer structure allows each layer to provide specific phase compensation, thereby achieving the desired wavefront modulation. Therefore, this invention belongs to the field of acoustic FSSs, primarily solving the problem of multi-band sound wave modulation in complex sound field environments, and providing a new solution for architectural acoustics, noise control, and other fields. Summary of the Invention

[0005] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

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

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a design method for adjusting the sound field distribution using frequency selective surface, comprising a substrate, wherein a unit structure is disposed on the substrate, 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 that applies frequency-selective surface modulation of sound field distribution, the substrate is divided into a high-density region, a transition region, and a low-density region from the center to the edge.

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

[0010] As a preferred technical solution for a design method that applies frequency-selective surface modulation of 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 that applies frequency-selective surface modulation of sound field distribution, the inner layer thickness is less than the middle layer thickness, and the outer layer thickness is less than the inner layer thickness.

[0012] The beneficial effects of this invention are as follows: By designing the unit structure on the substrate to gradually increase in size from the center to the edge and transition from a circle to an ellipse, this invention achieves a gradual adjustment of the sound field. This design effectively controls the propagation path and intensity of sound waves in different regions, resulting in a more uniform and controllable sound field distribution. Specifically, the gradual change in the shape of the unit structure optimizes the reflection and transmission characteristics of sound waves at different frequencies, enhancing the response capability of the frequency-selective surface to specific frequencies. Therefore, through this gradual design, not only is precise adjustment of sound waves achieved, but also the adaptability to multi-band sound waves is improved, resulting in a more flexible and precise sound field adjustment effect. Attached Figure Description

[0013] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0014] Figure 1 This is a schematic diagram of the distribution structure of the unit structure on the substrate in this invention;

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

[0016] Figure 3 This is a schematic diagram of the layered structure of the substrate in this 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 Implementation

[0018] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0019] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the 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 phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0021] Secondly, the present invention is described in detail with reference to the schematic diagrams. When detailing the embodiments of the present invention, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged, not according to the usual scale. Furthermore, the schematic diagrams are merely examples and should not limit the scope of protection of the present invention. In addition, actual fabrication should include three-dimensional spatial dimensions of length, width, and depth.

[0022] Example 1

[0023] Reference Figures 1-3 This embodiment provides a design method for adjusting the sound field distribution using frequency selective surface, including a substrate 100, on which a unit structure 101 is disposed. The unit structure 101 is circular, and the size of the unit structure 101 on the substrate 100 gradually increases from the center to the edge, and the shape gradually transitions from circular to elliptical.

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

[0025] The basic unit structure of an FSS (Focus Sound Filter) is designed with gradually changing geometric shapes, such as circles, ellipses, rectangles, and triangles. To achieve a gradual effect in sound field adjustment, geometric structures with smooth transitions are typically chosen.

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

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

[0028] For example, suppose the central unit structure is circular with a radius of $r_0 = 5$ mm, and it gradually increases in radius every 5 mm outwards. At the edge, the radius of the unit structure increases to $r_n = 10$ mm. Simultaneously, the shape gradually changes from a circle to an ellipse with a major axis to minor axis ratio of 2:1.

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

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

[0031] The smaller size and circular structure of the central area allow for uniform reflection and transmission of sound waves, ensuring the omnidirectional propagation of low-frequency sound waves.

[0032] The outward expansion of the gradually changing size and shape gradually alters the reflection and transmission paths of sound waves, especially controlling the directionality of high-frequency sound waves.

[0033] This gradient design allows for uniform adjustment and control of the sound field across different frequency ranges.

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

[0035] Material gradient technology is employed in different regions of the FSS to control the sound wave propagation speed and absorption rate in different areas. In practice, a combination of materials, ranging from high density to low density and from rigid to soft, is gradually used from the center of the FSS outwards.

[0036] This material gradient design was chosen because the 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 sound waves can be achieved, thereby achieving complex sound field gradient adjustment.

[0037] The FSS surface employs a gradient design that blends multiple materials, with the physical properties of the materials gradually changing from the center to the edge, such as from high density to low density, and from hard to soft.

[0038] The central region (high-density region 102) uses high-density rigid materials (such as aluminum or titanium alloy) to ensure strong sound wave reflection characteristics; the edge region (low-density region 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, in which the material gradually transitions, for example by mixing high-density and low-density materials to achieve the transition.

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

[0041] The central and peripheral materials transition through a gradient region, where the material composition is mixed proportionally. For example, the density variation of the material within the transition region can be linear or nonlinear to achieve smooth sound wave propagation characteristics.

[0042] Using composite material technologies (such as metal-polymer composites) ensures that the acoustic properties of the transition region meet design requirements, while also improving the mechanical stability of the structure.

[0043] High-density materials can effectively reflect sound waves, while low-density materials help absorb and weaken sound waves.

[0044] Gradual material distribution allows for precise adjustment of the propagation speed and absorption rate of sound waves across different frequency ranges, thereby achieving complex sound field control effects, such as focusing or spreading 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 high-absorption material, the middle layer 106 is an elastic material, and the outer layer 107 is a high-reflectivity material. The inner layer 105, the middle layer 106, and the outer layer 107 are fixed together 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 for sound wave absorption at specific frequencies, while the outer layer 107 is used for sound wave reflection or guidance at other frequencies.

[0047] The multi-layer gradient structure was chosen because it provides a wider range of sound field adjustment and enables more precise sound field control. By designing each layer differently, frequency-selective, multi-functional sound field adjustment can be achieved.

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

[0049] The layers are connected by adhesives or mechanical fastening to ensure no gaps between them and to guarantee 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 to achieve effective connection and acoustic property transition between different layers.

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

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

[0053] By designing and combining these layers, selective absorption, transmission, and reflection of sound waves across a wide frequency range can be achieved.

[0054] The inner layer of 105 high-absorption material is designed to absorb low-frequency sound waves and reduce low-frequency noise.

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

[0056] The outer 107 highly reflective material is designed to reflect high-frequency sound waves, preventing leakage of high-frequency sound waves, while forming a sound beam within a specific frequency range.

[0057] The multi-layered structure allows for adjustment of sound wave transmission, reflection, and phase to achieve functions such as sound wave focusing, sound insulation, and sound beam control. The multi-layered design ensures precise adjustment and control of sound waves across a wide frequency range, making the FSS structure suitable for a variety of complex acoustic applications.

[0058] To achieve the aforementioned gradient structure, precise manufacturing processes, such as 3D printing or micro / nano fabrication, are employed to create complex unit structures and material combinations.

[0059] These manufacturing processes were chosen because they provide high-precision control, ensuring that the geometry, dimensions, and material properties of the gradient structure are accurately achieved according to design requirements.

[0060] Example explanation:

[0061] Assuming the FSS structure is designed for a large conference hall, the requirement is to achieve uniform sound wave distribution and noise control within a frequency range of 1kHz to 5kHz. The design parameters are as follows:

[0062] Unit structure size and shape: The central circular unit structure has a radius that gradually changes from 5mm to 10mm, and the shape changes from a circle to an ellipse with a major axis to minor axis ratio of 2:1.

[0063] Gradual change in material properties: Aluminum alloy is used in the central area, while polyurethane foam is used in the peripheral areas. The material density changes from 2.7 g / cm³ in the center to... 3 0.5 g / cm at the edge 3 Gradual change.

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

[0065] Manufacturing process: Each layer of the structure is manufactured and processed using 3D printing and micro / nano fabrication technologies, and quality control and acoustic performance testing are carried out 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 the FSS, and then select the appropriate unit structure size and shape gradation method based on these requirements.

[0070] Assuming the target frequency range is 1kHz to 5kHz, based on the sound field adjustment requirements, the unit structure size is selected to be smaller in the central area and larger in the edge area, and gradually transitions from a circle to an ellipse.

[0071] Calculate the dimensional changes of the unit structure: Use the formula d(r)=d0+k·r to calculate the change in the unit structure size with radius r. Assume the initial size at the center d0=5mm, and the gradient coefficient k=0.1mm / mm.

[0072] Within the radius r ranging 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 create a 3D model of the FSS element. Based on the calculation results, draw the element structure sequentially from the center to the edge.

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

[0075] Gradual shape design: The unit structure gradually changes from a central circle to an ellipse. In the CAD model, the ratio of the major and minor axes of the ellipse is gradually changed from 1:1 to 1:2 by adjusting the ratio of the major and minor axes.

[0076] At different radius positions, determine the specific dimensions of the major and minor axes to meet the requirements of the gradient design.

[0077] Design Example:

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

[0079] The middle region (radius r = 10 to 30 mm): the unit structure size gradually increases to d = 8 mm, and the shape gradually transitions from a circle to an ellipse (major axis:minor axis = 1:1.5).

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

[0081] Material selection: Determine the acoustic modulation requirements of the FSS structure and select appropriate materials. For example, if the central area requires high reflectivity, choose a high-density material (such as aluminum alloy); if the edge area requires high absorption, choose a low-density material (such as foam or polyurethane).

[0082] Define the material gradient parameters: The gradient of the material's elastic modulus is defined using the formula E(r)=E0·(1-α·r). Assume the initial elastic modulus at the center is E0=70GPa (aluminum alloy), and the gradient coefficient α=0.01GPa / mm.

[0083] During the manufacturing process, the material properties are gradually varied by changing the mixing ratio of materials or using composite materials. For example, pure aluminum alloy is used in the central area; polyurethane foam is gradually added outwards until the edges are entirely made of low-density materials.

[0084] Design Example:

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

[0086] The middle region (radius r = 10 to 30 mm) is made of a composite material of aluminum alloy and polyurethane foam, with the elastic modulus E gradually decreasing from 70 GPa to 40 GPa.

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

[0088] Design and stacking of multi-layered gradient structures:

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

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

[0091] Outer layer (layer 3): Designed to reflect sound waves of other frequencies, using a highly reflective material (such as aluminum).

[0092] The design incorporates a gradient characteristic for each layer: 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) gradually becomes denser from the center to the edge to improve the reflectivity of high-frequency sound waves.

[0095] The sound field adjustment performance was simulated using multilayer simulation software (such as COMSOL Multiphysics). Through multiple iterations, the thickness, material, and position of each layer were optimized to ensure optimal sound field adjustment within the target frequency range.

[0096] Design Example:

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

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

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

[0100] Based on the complexity and precision requirements of the FSS structure, a combination of 3D printing technology and micro / nano fabrication technology was selected.

[0101] First, use 3D printing technology to manufacture the basic structure of FSS (such as cantilever beams and membrane structures) to ensure the overall dimensional accuracy of the structure and the realization of complex geometries.

[0102] Then, micro- and nano-fabrication techniques are used to finely process and coat the material surface (such as the deposition of nanoscale material coatings) to ensure the material's gradient properties and surface smoothness.

[0103] During the manufacturing process, quality inspections are conducted after each step is completed (such as using a laser interferometer to measure surface flatness and X-rays to inspect the internal structure) to ensure that the structure and material properties meet the design requirements.

[0104] Design Example:

[0105] The FSS basic structure was printed using a high-precision 3D printer (such as the EOS M 290) with a printing resolution of 0.01 mm.

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

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

[0108] The manufactured FSS structure is installed in the anechoic chamber to ensure that there are no other sources of noise interference in the acoustic testing environment.

[0109] The reflectivity, absorptivity, directivity, and frequency selectivity of the FSS structure are measured using acoustic testing equipment such as sound intensity meters and multi-frequency sound sources.

[0110] Within a frequency range of 1kHz to 5kHz, the frequency and direction of the sound source were gradually adjusted, and sound wave reflection and absorption data at different locations were recorded.

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

[0112] Based on the test results, the design parameters of the FSS structure (such as unit size, material properties, and stack thickness) are adjusted, and through multiple iterations of optimization, the structure is ensured to achieve optimal performance.

[0113] Design Example:

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

[0115] Based on the measurement results, the size and material combination of the central region unit structure were adjusted to improve the low-frequency reflection effect, while the material combination of the edge region was optimized to enhance the high-frequency absorption effect.

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

[0117] The gradual application of material properties is based on the geometric position of the unit structure to ensure that the acoustic performance of each unit is optimal within a specific frequency range.

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

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

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

[0121] In the design method of this invention, the rationality of character interpretation and the beneficial effects of key steps directly determine the structural performance and sound field adjustment effect. Firstly, the crucial step of determining the gradient design parameters, by selecting the target frequency range of the FSS and the sound field adjustment requirements, allows for the targeted selection of the size and shape gradient of the unit structure, thereby solving the problem of limited sound field adjustment range in traditional FSS designs. For example, the selection of a target frequency range of 1kHz to 5kHz reasonably covers important frequency bands in everyday acoustic applications. Furthermore, the unit structure design with a smaller center and larger edges, combined with a structure that gradually transitions from a circle to an ellipse, effectively optimizes the sound field distribution and solves the problem of insufficient sensitivity to specific frequencies in traditional structures. This design not only enhances the reflection and absorption capabilities of sound waves at different frequencies but also precisely controls the propagation path of sound waves, ultimately improving the accuracy and consistency of sound field adjustment.

[0122] The calculation of unit structure size changes uses formulas to further quantify the variation of unit structure with radius r, ensuring the controllability and scientific nature of the design. For example, setting the initial size d0 = 5mm and the gradation coefficient k = 0.1mm / mm, the mathematical model accurately determines the unit size changes under different radii, ensuring the continuity and optimization performance of the gradation design. This calculation method can precisely adjust design parameters according to specific application scenarios, solving the problems of arbitrariness and uncertainty in gradation design in traditional methods, and ultimately ensuring the effectiveness of sound field adjustment.

[0123] The gradual shape transition from circular to elliptical in the design, achieved by adjusting the ratio of the major and minor axes from 1:1 to 1:2, enhances the selectivity of the FSS for different frequencies. For example, the circular unit structure in the central region reflects low-frequency sound waves better, while the elliptical structure in the edge region helps absorb high-frequency sound waves. This gradual shape design solves the problem of insufficient precision in multi-frequency sound wave response of traditional single-shape FSS structures, significantly improving the sound wave tuning capability at different frequencies.

[0124] In material selection and the definition of gradient parameters, a formula is used to define the gradient of the material's elastic modulus, ensuring that the material properties match the geometric position of the unit structure. For example, choosing aluminum alloy (E=70GPa) for the central region provides high reflectivity, while using polyurethane foam (E=20GPa) for the edge region enhances absorption capacity. This gradient material design solves the problem of traditional materials being singular and having fixed properties, thereby optimizing the reflection and absorption performance of sound waves across different frequency ranges and improving the adaptability of the FSS structure in multi-frequency applications.

[0125] Finally, the design and stacking of a multi-layered gradient structure, combining the absorption of the inner layer, the guidance of the middle layer, and the reflection of the outer layer, further refined the functional distribution of the structure through layer-by-layer design. This design not only solved the problem of inaccurate modulation of different frequency sound waves in single-layer structures, but also achieved precise control of sound waves in different frequency bands through the gradual change of material properties and the adjustment of thickness. For example, the gradually increasing thickness of the inner rubber layer enhances the absorption of low-frequency sound waves, while the gradually increasing density of the outer aluminum material improves the reflectivity of high-frequency sound waves, further enhancing the sound field modulation effect.

[0126] By designing the unit structures on the substrate to gradually increase in size and transition from circular to elliptical shapes from the center to the edge, a gradual approach to sound field adjustment is achieved. This design effectively controls the propagation path and intensity of sound waves in different regions, resulting in a more uniform and controllable sound field distribution. Specifically, the gradual shape change of the unit structures optimizes the reflection and transmission characteristics of sound waves at different frequencies, enhancing the response capability of the frequency-selective surface to specific frequencies. Therefore, this gradual design not only achieves precise sound wave adjustment but also improves adaptability to multi-frequency sound waves, resulting in a more flexible and precise sound field adjustment effect.

[0127] The substrate is divided into high-density, transition, and low-density zones. This density-zoning design allows for varying degrees of modulation of sound wave propagation characteristics in different areas. The high-density zone primarily absorbs high-frequency sound waves, while the low-density zone helps reflect low-frequency sound waves, and the transition zone acts as a smooth transition between the two. This density-zoning design, by altering the sound wave propagation path and absorption characteristics, achieves multi-level control of the sound field, improving the flexibility of sound field distribution and enhancing adaptability to complex sound field environments. Therefore, this design achieves the beneficial effects of optimizing sound wave energy distribution and reducing sound wave interference.

[0128] Multi-layered structural design: The inner layer is made of highly absorbent material, the middle layer of elastic material, and the outer layer of highly reflective material. This multi-layered design significantly enhances the structure's sound wave processing capabilities. The high-absorption material in the inner layer effectively absorbs sound waves in specific frequency bands, avoiding unnecessary sound wave reflections and thus reducing noise and echoes in the sound field. The elastic material in the middle layer provides better sound wave control by adjusting the propagation speed and direction of sound waves. The high-reflective material in the outer layer further enhances the reflection performance of sound waves in specific frequency bands, thereby achieving effective guidance and concentration of sound waves at specific frequencies. Through the combination and functional allocation of multiple layers of materials, the structure optimizes the absorption, reflection, and propagation of sound waves, further improving the controllability and adjustability of the sound field.

[0129] The use of flexible and rigid adhesives: Using a flexible adhesive between the inner and middle layers provides greater structural flexibility, allowing the materials to adapt to dynamic changes in sound waves, reducing energy loss at the interface, and thus improving overall sound wave absorption efficiency. Using a rigid adhesive between the middle and outer layers provides stronger structural stability, ensuring the accuracy and consistency of sound wave reflection. Therefore, by selecting different adhesives, functional complementarity and structural stability are achieved between materials, enhancing the precision of sound wave modulation and overall durability.

[0130] The varying thicknesses of the inner, middle, and outer layers allow the structure to cater to different sound wave frequencies. The thinner inner layer is better suited for absorbing high-frequency sound waves, while the thicker middle layer helps regulate the propagation of mid- and low-frequency sound waves, and the outer layer optimizes reflection characteristics. This differential thickness design enables precise adjustment of sound waves across different frequency bands, thereby improving the flexibility and accuracy of the sound field distribution.

[0131] The design method of selecting appropriate unit structure size and shape gradation patterns achieves a high degree of customization of the sound field distribution by choosing suitable unit structure size and shape gradation patterns based on the target frequency range and sound field adjustment requirements of the FSS. This method allows for adjustment of the geometric parameters of the unit structure according to different acoustic application scenarios, thereby meeting the requirements of different frequency ranges and sound field distributions. This provides a highly flexible and targeted optimization path for the design, significantly improving the performance of the FSS in various application scenarios.

[0132] By using formulas to accurately calculate the variation of unit structure dimensions with radius, the gradual design of unit structures is quantified and controllable. This method directly reflects the relationship between geometric parameters and sound field adjustment performance through a mathematical model, thus ensuring the scientific validity and effectiveness of the design. This design approach allows for more precise sound field distribution adjustment and can be calculated and adjusted to meet different application requirements, achieving a dual improvement in design efficiency and accuracy.

[0133] Defining a gradual change in the elastic modulus of a material using a formula allows for dynamic adjustment of the material's mechanical properties based on the sound field conditioning requirements of different regions. This design method ensures that the material's response to sound waves varies across different regions, achieving more precise control over the sound wave propagation path. Through this gradual change in elastic modulus design, a deep coupling between material properties and sound field conditioning effects is ultimately achieved, making the sound field distribution more aligned with the expected goals and improving the overall material performance and sound wave control effect.

[0134] It should be understood that numerous specific implementation decisions can be made during the development of any practical implementation, such as in any engineering or design project. Such development efforts may be complex and time-consuming, but for those skilled in the art who benefit from this disclosure, the development effort will be a routine work of design, manufacturing, and production without requiring much experimentation.

[0135] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A device for adjusting the sound field distribution using frequency-selective surface modulation, characterized in that: Includes a substrate (100), on which a unit structure (101) is disposed, the unit structure (101) being circular, the size of the unit structure (101) on the substrate (100) gradually increasing from the center to the edge, and the shape gradually transitioning from circular to elliptical; The substrate (100) is divided into a high-density region (102), a transition region (103) and a low-density region (104) from the center to the edge. The substrate (100) includes an inner layer (105), a middle layer (106) and an outer layer (107). The inner layer (105) is a high-absorption material, the middle layer (106) is an elastic material, and the outer layer (107) is a high-reflection material. The inner layer (105), the middle layer (106) and the outer layer (107) are fixed together by an adhesive. The thickness of the inner layer (105) is less than the thickness of the middle layer (106), and the thickness of the outer layer (107) is less than the thickness of the inner layer (105); 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). Based on the target frequency range and sound field adjustment requirements of the FSS, select the unit structure size and shape gradation method; Select materials based on the acoustic wave modulation requirements of the FSS structure; The function, material, and gradient characteristics of each layer are determined to form a multi-layer structure.

2. The frequency-selective surface-adjustable sound field distribution device according to claim 1, characterized in that: The shape gradient options include: Use formula The variation of the unit structure dimensions with radius r is calculated, where Let K be the initial size at the center, K be the shape gradient coefficient, and r be the radius.

3. The application frequency selective surface-adjustable sound field distribution device according to claim 2, characterized in that: The available materials include: Use formula Define the gradual change in the elastic modulus of a material, where E0 is the elastic modulus of the material. denoted by , where r is the material gradient coefficient and r is the radius.

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