An acoustic superstructure for coordinated control of double-sided acoustic waves and its design method

Abstract

The present invention provides an acoustic superstructure for coordinated control of double-sided sound waves and a design method thereof, which solves the technical problem that existing acoustic metamaterials can only achieve single-sided wave control but cannot achieve double-sided wave control. An acoustic superstructure for coordinated control of double-sided sound waves includes a plurality of acoustic units arranged in an array; the acoustic unit is an Ω-shaped Helmholtz resonator, and the sound wave inlet side and the sound wave outlet side of the Ω-shaped Helmholtz resonator are separated on both sides of the Ω shape, wherein the sound wave inlet side is provided with a tortuous cavity open on three sides; by adjusting the length and width of the tortuous cavity, the impedance of the lower surface of the acoustic unit can be adjusted; by designing the parameters of the acoustic unit and arranging the acoustic unit periodically, it is possible to achieve a differentiated impedance arrangement on both sides of the acoustic superstructure, so that there is a phase gradient between the sound wave inlet side and the sound wave outlet side of the acoustic superstructure.

Description

Technical Field

[0001] The present invention belongs to the technical field of acoustic metamaterials, and specifically relates to an acoustic metastructure for coordinated regulation of double-sided sound waves and a design method thereof. Background Art

[0002] With the development of science and technology, noise issues have become increasingly prominent. Acoustic metamaterials, due to their excellent performance and flexible designability, have developed rapidly in recent years and have garnered widespread attention in noise control. Acoustic metastructures are composite materials composed of multiple acoustic units. They can achieve beam steering and propagation control of sound waves by manipulating the shape, arrangement, and material parameters of these units. A characteristic of these composite materials is that they can achieve equivalent continuous material properties for certain specific properties of sound waves within a given range. This property enables them to effectively control properties such as sound wave propagation, focusing, and transparency. Therefore, the study of acoustic metastructures is of great significance.

[0003] At present, acoustic metamaterials can be classified into reflective, transmissive, and sound-absorbing types. Among them, both reflective metasurfaces and transmissive metasurfaces can manipulate sound waves to achieve basic physical phenomena based on the generalized Snell's law, such as abnormal scattering (reflection and refraction), Bessel sound column generation, sound convergence, surface wave conversion, and sound vortexes. In other unique applications, reflective metasurfaces can achieve acoustic stealth, and transmissive metasurfaces can achieve asymmetric transmission. However, these wave-controlling acoustic metamaterials can only achieve unilateral wave control effects, and cannot meet the application scenarios of modulating the transmission of part of the sound wave while modulating the reflection of part of the sound wave.

[0004] In view of this, the research team of the present invention believes that it is necessary to explore an acoustic superstructure that can perform coordinated regulation of double-sided sound waves. Summary of the Invention

[0005] The purpose of the present invention is to address the shortcomings of existing acoustic metamaterials that can only achieve single-sided wave control but not double-sided wave control, and to provide an acoustic metastructure for coordinated double-sided sound wave control and a design method thereof. The acoustic metastructure is an acoustic metastructure that combines a maze-type acoustic structure and a Helmholtz resonator and has phase gradients on both sides (the sound wave inlet side and the sound wave outlet side), which can simultaneously realize the control of reflected waves and transmitted waves.

[0006] To achieve the above objectives, the technical solutions provided by the present invention are:

[0007] An acoustic superstructure for coordinated control of double-sided acoustic waves, which is special in that it includes multiple acoustic units arranged in an array;

[0008] The acoustic unit is an Ω-shaped Helmholtz resonator, and the sound wave inlet side and the sound wave outlet side of the Ω-shaped Helmholtz resonator are respectively located on two sides of the Ω shape, wherein the sound wave inlet side is provided with a tortuous cavity open on three sides; that is, the acoustic superstructure for double-sided sound wave coordinated regulation is composed of an array of multiple Ω-shaped Helmholtz resonators with tortuous cavities provided on the sound wave inlet sides;

[0009] By adjusting the length and width of the tortuous cavity, the impedance of the lower surface of the acoustic unit can be adjusted;

[0010] By designing the parameters of the acoustic units and arranging them periodically, it is possible to achieve a differentiated impedance arrangement on both sides of the acoustic superstructure, so that there is a phase gradient between the sound wave inlet side (also referred to as the lower surface in this article) and the sound wave outlet side (also referred to as the upper surface in this article) of the acoustic superstructure to achieve anomalous reflection and anomalous refraction at the target frequency; depending on actual needs, the length and width of the tortuous cavity in each acoustic unit may be different.

[0011] Furthermore, the plurality of acoustic units are arranged in a two-dimensional array. Of course, the array arrangement of the acoustic units can be adjusted accordingly according to different actual application requirements.

[0012] Furthermore, adjacent acoustic units are connected via a base plate made of the same material as the adjacent acoustic units.

[0013] Furthermore, the acoustic unit is prepared using 3D printing technology and is made of resin.

[0014] The design method of the above-mentioned acoustic superstructure for coordinated control of double-sided acoustic waves is special in that it includes the following steps:

[0015] 1) Constructing a mapping relationship between acoustic unit impedance and configuration, that is, calculating the input impedance amplitude of the zigzag cavity under different geometric parameters and the impedance phase of the zigzag cavity under different geometric parameters at multiple frequencies; calculating the input impedance amplitude of the Ω-type Helmholtz resonator throat diameter under different geometric parameters and the impedance phase of the upper and lower surfaces of the Ω-type Helmholtz resonator throat diameter under different geometric parameters;

[0016] Calculate the theoretical phase spatial distribution on both sides of the acoustic unit based on the wave control physical phenomena required for practical applications;

[0017] 2) According to the theoretical phase spatial distribution requirements obtained in step 1), the spatial impedance distribution form is obtained;

[0018] 3) Combining the mapping relationship between the acoustic superstructure unit impedance and configuration constructed in step 1) and the spatial impedance distribution form obtained in step 2), the spatial distribution and filling of the acoustic units are carried out, and the arrangement of the acoustic units of the acoustic superstructure is designed so that the phase gradient on both sides of the designed acoustic superstructure meets the actual phase requirements.

[0019] Further, in step 1), the geometric parameters of the zigzag cavity include the length and width of the zigzag cavity;

[0020] The geometric parameters of the Ω-type Helmholtz resonator include the length and width of the throat diameter and the cavity volume of the Helmholtz resonator;

[0021] The impedances of the acoustic unit's sound wave inlet and outlet sides can be designed by selecting the parameters of the zigzag cavity and the Ω-type Helmholtz resonator, such as the length and width of the throat diameter, the length and width of the zigzag cavity, and the volume of the Helmholtz resonator cavity. This can form a phase gradient on both sides of the metasurface to achieve anomalous reflection and anomalous refraction at the target frequency.

[0022] Furthermore, in step 2), the theoretical phase space distribution is a linear distribution, a parabolic distribution, etc.

[0023] In addition, the present invention also provides a method for manufacturing the above-mentioned acoustic superstructure, which is special in that the steps are as follows:

[0024] S1. Using software with 3D modeling and acoustic vibration analysis capabilities (e.g., UG, COMSOL, etc.), based on actual engineering application requirements and following the aforementioned design method, design and render a solid model of an acoustic metastructure with coordinated double-sided acoustic wave control.

[0025] S2. Import the acoustic superstructure solid model drawn in step S1 into a 3D printer, layer the model into several two-dimensional models, then spray resin and solidify layer by layer to print an acoustic superstructure with coordinated control of double-sided sound waves.

[0026] Principle of the invention:

[0027] The surface of plants can both absorb and reflect visible light, which aroused the interest of the research team of this invention and led to their analysis and research. They found that this was due to the curved surface formed by the Ω-shaped anticlinal wall structure of plant surface cells and the wax columnar protrusions on the three-dimensional surface of the plant. Therefore, the research team of this invention proposed an acoustic unit with dual-sided regulation of the target frequency based on the Ω-shaped anticlinal wall and three-dimensional surface wax structure of the plant surface. The unit includes an Ω-shaped Helmholtz resonator structure and a tortuous cavity structure designed in the area at the sound wave entrance.

[0028] The acoustic unit of the present invention realizes different acoustic impedances on both sides of the acoustic unit through the combination of "zigzag cavity + Ω-type Helmholtz resonator", and realizes differentiated impedance arrangement on both sides of the acoustic superstructure through the design and periodic arrangement of acoustic unit parameters, thereby obtaining an acoustic superstructure with phase gradients on both sides.

[0029] According to the requirements of surface impedance hyperbolic and linear phase gradient, an acoustic superstructure is designed to enable it to have the ability to control two-sided sound waves, such as simultaneous anomalous reflection and anomalous refraction, generation of bilateral Bessel sound columns, bilateral sound convergence and bilateral surface wave conversion. Furthermore, a design method for an acoustic superstructure with coordinated control of double-sided sound waves is proposed to achieve the goal of coordinated control of transmitted and reflected sound waves.

[0030] The advantages of the present invention are:

[0031] 1. By arranging the acoustic units at the desired design frequency, the desired metamaterial phase distribution is obtained, which can achieve the simultaneous occurrence of anomalous reflection and anomalous refraction, the generation of bilateral Bessel sound columns, bilateral sound convergence, and bilateral surface wave conversion.

[0032] 2. The present invention has sufficient dual-side impedance adjustment capability, which enables it to be applied more flexibly in engineering to adapt to different demand scenarios.

[0033] 3. The design method of the present invention is supported by corresponding theories and simulation results, and can have strong scalability and broad design space in future designs.

[0034] 4. The present invention is prepared using 3D printing technology, the overall structure is composed of a single base material, and the processing technology is simple.

[0035] 5. The present invention has a compact structure and small size, which is convenient for installation and noise reduction in actual engineering applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Schematic diagram of the acoustic metamaterial structure and geometric parameters of each part for the coordinated regulation of double-sided sound waves of the present invention, where S is the throat width of the Helmholtz resonator, L is the throat length of the Helmholtz resonator, and V is the volume of the Helmholtz resonator cavity; D is the length of the tortuous cavity, H is the width of the tortuous cavity, and R1 and R2 are the outer and inner diameters of the curved channel of the Helmholtz resonator;

[0037] Figure 2 A top view of four structural units with different tortuous cavities of the acoustic superstructure for coordinated control of double-sided acoustic waves of the present invention;

[0038] Figure 3 is the input impedance amplitude of the zigzag cavity under different geometric parameters of the present invention;

[0039] Figure 4 is the phase of the lower surface (acoustic wave entrance side) unit under the zigzag cavity with different parameters of the present invention;

[0040] Figure 5 is the unit phase of the upper surface (sound wave outlet side) under the zigzag cavity with different parameters of the present invention;

[0041] Figure 6 is the input impedance amplitude of the Helmholtz resonator under different geometric parameters of the present invention;

[0042] Figure 7 is the phase of the lower surface unit under different throat diameters of the Helmholtz resonator of the present invention;

[0043] Figure 8 The upper surface unit phase of the Helmholtz resonator with different throat diameters of the present invention;

[0044] Figure 9 This is a schematic diagram of the acoustic half-lens principle;

[0045] Figure 10 is the phase distribution of the metamaterial at 4000 Hz;

[0046] Figure 11 The sound intensity field and sound pressure field of the acoustic half lens caused by the incident sound wave at 4000Hz and 0 degrees, (c) is the sound intensity field, and (d) is the sound pressure field;

[0047] Figure 12 Schematic diagram of the principle of generating double-sided Bessel sound columns at 3900Hz;

[0048] Figure 13 Double-sided acoustic convergence at 3900 Hz: (a) sound intensity field; (b) sound pressure field;

[0049] Figure 14 Surface wave conversion scattered sound pressure: (a) 51 degrees of incidence, 3500 Hz; (b) 52 degrees of incidence, 4300 Hz; (c) 49 degrees of incidence, 2800 Hz;

[0050] Figure 15 Figure 3. Scattered acoustic pressure of metamaterials with different zigzag cavities at normal incidence at 4300 Hz: (a) metasurface before the zigzag cavity; (b) metasurface after the zigzag cavity.

[0051] Figure 16 This is the structural design diagram of the acoustic unit of the present invention. DETAILED DESCRIPTION

[0052] The present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments:

[0053] like Figure 1 and Figure 2 As shown, an acoustic metastructure for coordinated double-sided acoustic wave control consists of a two-dimensional array of multiple superimposed Ω-shaped Helmholtz resonators with zigzag cavities. The zigzag cavities are located on the acoustic wave inlet side of the structural unit. The parameters of the zigzag cavities and Helmholtz resonators in each structural unit can be changed to achieve impedance control design. The specific implementation scheme is as follows:

[0054] 1. Acoustic unit design size basis

[0055] When the frequency of the excitation sound wave is extremely large compared to the wavelength, the zigzag cavity can be equivalent to a straight tube of equal length and width. The impedance of the closed straight tube can be written as:

[0056] Z s ≈-jρ0c0cotkl (1)

[0057] Where ρ0 is the air density, c0 is the speed of sound, l is the length of the straight tube, k is the wave number, and j is the imaginary unit. From formula (1), we can get:

[0058]

[0059] The periodic occurrence of zero impedance and infinite impedance turns the opening of the zigzag cavity into an alternating soft boundary and hard boundary, which causes the phase of the reflected sound wave to change by π or remain unchanged.

[0060] In order to analyze the impedance distribution law of the tortuous cavity, Figure 3 The input impedance amplitude of the zigzag cavity under different geometric parameters is calculated in the figure. The input impedance amplitude of the zigzag cavity at different target frequencies can be used to estimate the soft and hard boundary formation area of ​​the average impedance of the acoustic unit's lower surface, providing a basis for selecting the geometric dimensions of the zigzag cavity.

[0061] In order to reveal the relationship between the phase on both sides of the acoustic unit structure and the zigzag cavity, the impedance phase of the zigzag cavity with different geometric parameters at several frequencies is calculated in the embodiment, as shown in Figure 2 and Figure 3. Figure 5 As shown. The outer diameter of the acoustic unit R1 = 13.5mm, the inner diameter R2 = 16.5mm; the throat diameter length of the Helmholtz resonator L = 6mm, the width S = 2mm; the cavity length of the Helmholtz resonator C x =15mm, width C y =30mm; the length of the meandering cavity changes from D=10mm to D=60mm, and the width of the meandering cavity changes from H=0.5mm to H=3.5mm. The phase gradient line in Figure, Figure 5 This is clearly visible in the plot, for example, lines A1 and A2 at 3800Hz and 4300Hz. The choice of parameters can be easily accomplished by selecting points along these lines, which are used to construct the phase gradient at the bottom surface of the unit cell at the base of the periodic structure. The phase of the impedance at the upper surface of the periodic unit cell structure is largely independent of the parameters chosen for the meandering cavity.

[0062] In order to analyze the impedance distribution law of the Helmholtz resonator, Figure 6The input impedance amplitude of the Helmholtz resonator is calculated for different geometric parameters. The dominant geometric factors influencing the impedance amplitude of the Helmholtz resonator at different target frequencies can be estimated from the figure, providing a basis for selecting the geometric dimensions of the Helmholtz resonator.

[0063] In addition, the effect of the Helmholtz resonator on the impedance phase of the upper and lower surfaces of the acoustic unit is also calculated, such as Figure 7 、 Figure 8 As shown. The unit outer diameter R1 = 13.5mm, the inner diameter R2 = 16.5mm; the length of the zigzag cavity D = 20mm, the width H = 1.5mm; the length of the Helmholtz resonator cavity C x =15mm, width C y =30mm; the length of the Helmholtz resonator throat diameter changes from L = 2mm to L = 10mm, and the width of the throat diameter changes from S = 2mm to S = 6mm. In the figure, the phase gradient lines at 2800Hz to 4300Hz can be found, numbered as lines B1 to B 24 The results show that line B5-B6, line B 11 -B 12 Line B 17 -B 18 Line B 23 -B 24 The parameters selected in can construct the phase gradient on the upper surface of the periodic acoustic unit structure and have a limited impact on the phase of the units on the lower surface of the structure.

[0064] From the above analysis, we can see that the geometric dimensions of the zigzag cavity have a significant impact on the impedance of the cell's lower surface, but have almost no effect on the impedance of the cell's upper surface. The Helmholtz resonator affects both the upper and lower surface impedances of the cell, but has a greater impact on the upper surface impedance and a smaller impact on the lower surface impedance. Therefore, by selecting the parameters of the zigzag cavity and the Helmholtz resonator respectively, the impedance of the cell's upper and lower surfaces can be designed, thereby forming a phase gradient on both sides of the metamaterial to achieve anomalous reflection and refraction at the target frequency.

[0065] Based on the above analysis, four acoustic units with different geometric parameters are designed in the embodiment, and their geometric parameters are shown in Table 1.

[0066] Table 1 Geometric parameters of the four elements

[0067]

[0068] 2. Using the acoustic units designed above, different acoustic superstructures are obtained through spatial arrangement

[0069] Example 1

[0070] Based on the concept of optical semi-transparent reflectors, an acoustic half-lens with double-sided acoustic properties is constructed by utilizing the characteristics of the Ω-type metamaterial unit with double-sided adjustable impedance. The acoustic half-lens can separate the sound wave into two sound waves with a specified angle, and focus them on two points through reflection and transmission. The acoustic half-lens is a flat metamaterial structure in actual geometric shape, but its phase distribution is similar to a lens with double-sided concave and convex shapes, with a symmetrical phase distribution. When a plane wave is incident from below, part of it is reflected by the concave lens surface and converges at the lower focus; the other part of the sound wave passes through the lower surface, emerges from the convex lens surface on the other side and converges at the upper focus, as shown in FIG. Figure 9 shown.

[0071] In order to construct ideal refraction and transmission, the acoustic phase on both sides of the acoustic membrane reflector should be designed according to the generalized Snell's law, that is:

[0072]

[0073] Among them, θ i is the angle of incidence, θ t is the reflection angle or refraction angle, k0 is the wave number, and dφ / dx is the phase gradient change. This means that by selecting a suitable metamaterial unit and designing the double-sided phase gradient of the metamaterial unit, the design of an acoustic half-lens can be realized. Unlike the Bessel sound column and the acoustic focusing lens, the acoustic half-lens will allow part of the incident sound wave to pass through the metamaterial and be emitted from the other side, and reflect the other part back to the original direction. In order to realize the modulation of the reflected sound wave and the transmitted sound wave, the Ω-type metasurface unit designed in Table 1 is used to design a metamaterial phase gradient arrangement to achieve simultaneous adjustment of the phase distribution on both sides of the acoustic semi-transparent mirror. According to the principle of unilateral acoustic focusing, the bilateral phase gradient should be constructed as a parabolic function. Taking into account the incident angle θ i =0, Equation 3 can be rewritten as:

[0074]

[0075] Where φ(0) is the phase at the center of the surface, y0 is the vertical coordinate of the focus (0,y0), and k0 is the wave number of the incident wave. In this case, the structure has phase gradients on the top and bottom surfaces, respectively. The top and bottom focus positions are chosen to be y0 up =800mm and y0 down =800mm. The acoustic phase of the center point of the double-sided surface is selected as φ(0) up =6.07 and φ(0) down =2.08. The ideal phase distribution and the actual phase of the unit patchwork are as follows Figure 10As shown. The entire metamaterial unit is symmetrically distributed, with units arranged from number ① to number ④ and then back to number ①. The number of repetitions is: 2, 2, 3, 5, 3, 2, 2 (i.e., the arrangement order is: 11, 22, 333, 44444, 333, 22, 11). The above model is now numerically simulated and verified in COMSOL Multiphysics. The spatial dimension is selected as two dimensions, and the physical fields are selected as pressure acoustics, frequency domain (acpr) and thermoviscous acoustics, frequency domain (ta). The above symmetrical acoustic half-lens metamaterial geometric model is imported and rectangular regions are established above and below it. Perfectly matched layers are placed outside the rectangular regions to eliminate reflection. After the incident sound wave is acted upon by the metamaterial, it can propagate freely in the rectangular regions above and below. The zigzag cavity and the throat diameter of the Helmholtz resonator are set to thermoviscous acoustics, and the other regions are set to pressure acoustics. The geometric unit entity is selected as a hard boundary that can completely reflect the sound wave. Apply an upward background sound pressure of 1Pa to the lower rectangular area to excite the metamaterial, and calculate the sound pressure and intensity field of the acoustic half lens caused by the 4000Hz, 0-degree incident sound wave. Figure 11 As shown. The results show that the phase gradient distribution of the acoustic half-lens metasurface designed above meets the phase requirements of focusing on both sides at 4000 Hz. On the bottom side of the acoustic half-lens, the sound wave is reflected by the lower surface of the metamaterial and focused on one point. On the other side, the sound wave is emitted from the upper surface of the metamaterial and refracted to focus on another point. The two acoustic wave foci demonstrate the focusing ability of the acoustic film reflector. Acoustic focusing technology has become increasingly mature and can be used in many fields. For example, in the field of non-destructive testing, acoustic focusing can be used to detect internal defects in materials, and in the medical field, ultrasonic energy can be gathered for stone surgery.

[0076] Example 2

[0077] Based on the Ω-shaped geometric unit designed in Table 1, a linearly repeated arrangement of four units was employed, leveraging the dual-surface acoustic wave synergistic control capabilities of the present invention to design an acoustic metamaterial capable of generating a bilateral Bessel acoustic column. While this metamaterial is geometrically flat, its phase distribution physically resembles a bilateral triangular pyramid prism, as shown in Figure 12.

[0078] The entire metamaterial is a symmetrical structure, composed of three repetitions of each unit type arranged in sequence. The transmitted sound wave is modulated by all four units, forming two plane waves above the metamaterial to form a Bessel acoustic column. The reflected sound wave is modulated by units ③ and ④ located in the center of the metamaterial, while units ① and ② located on both sides of the metamaterial do not participate in the modulation of the reflected sound wave. According to the generalized Snell's law, if Bessel acoustic columns are generated, the phase change along the x-direction on both sides of the metamaterial satisfies:

[0079] φ(x)=k0|x|sin(β)+φ(0) (5)

[0080] Where β is the angle of reflection or refraction, φ(0) up =5.88 and φ(0) down =1.83 is the phase change between the upper and lower surfaces at the center point. The metamaterial units are symmetrically distributed, arranged from unit ① to unit ④ and then back to unit ①, with the unit repetition numbers being 3, 3, 3, 3, 3, 3 (i.e., the arrangement order is 111, 222, 333, 444, 333, 222, 111). The above model is numerically simulated and verified in COMSOL Multiphysics. Two-dimensional spatial dimensions are selected, and pressure acoustics, frequency domain (acpr) and thermoviscous acoustics, frequency domain (ta) are selected for the physics fields. The aforementioned symmetrical double-sided Bessel acoustic column metasurface geometry model is imported, and rectangular regions are created above and below it. Perfectly matched layers are placed on either side of the rectangular regions to eliminate reflections. After the metamaterial acts, the incident sound wave can propagate freely in the upper and lower rectangular regions. The zigzag cavity and the Helmholtz resonator throat are set to thermoviscous acoustics, while the other regions are set to pressure acoustics. The geometric unit entities are selected as hard boundaries that can completely reflect sound waves. Apply an upward background sound pressure of 1Pa to the lower rectangular area to excite the metamaterial, and calculate the sound pressure and intensity field generated by the double-sided Bessel sound column caused by the incident sound wave at 3900Hz and 0 degrees. Figure 13 As shown. The results show that the phase gradient distribution of the designed metamaterial meets the phase requirements of the 3900Hz double-sided Bessel sound column generation. The simulation results show that two symmetrical plane waves are formed on both sides of the metamaterial at the same time and the Bessel sound column is generated. Due to the smaller number of reflected sound wave modulation units, the width of the two generated plane waves is narrower, and the lower side of the metamaterial shows stronger reflection performance. The scattered sound pressure field and scattered sound intensity field of the double-sided Bessel sound column at 3900Hz are shown as follows: Figure 3 It is worth mentioning that Figure 3 In (a), it can be seen that there is a more obvious energy asymmetry on the reflection side. This is due to a slight difference caused by the change in the exit direction of the curved channel, that is, the direction of the abnormally reflected sound wave on the left side of the symmetry center is opposite to the direction of the curved channel; on the right side of the symmetry center, the direction of the abnormally reflected sound wave is the same as the direction of the curved channel.

[0081] Example 3

[0082] In order to study the surface wave conversion phenomenon, a periodic term is introduced into the generalized Snell's law. The generalized Snell's law with a periodic term is written as:

[0083]

[0084] Where n represents the diffraction order due to the repetitive arrangement of the unit cells, m represents the diffraction order due to the repetition of the entire period, d is the width of each unit cell, and Γ is the length of one period of the metamaterial array. If the unit cell width is significantly smaller than the target wavelength and very high orders are ignored, any non-zero value of n will cause the diffracted waves caused by the repetitive arrangement of the unit cells to become evanescent waves. Therefore, Equation 6 can be rewritten as:

[0085]

[0086] When the phase distribution range of the metamaterial unit exceeds π, most of the energy of the diffracted waves allowed by the periodic structure is distributed on the order m = ±1. This means that if the phase gradient and periodicity of the metasurface array Γ are properly designed, at certain incident angles θ i Under these conditions, a reflection angle or refraction angle with an imaginary part will be generated, thereby generating a phenomenon of conversion from propagating waves to surface waves. In order to reveal the surface wave conversion phenomenon in the double-sided metamaterial structure, a periodic arrangement is performed by repeating each unit 1 to 4 three times. Then, the sound field on both sides of the double-sided element surface is calculated at an incident angle of 49 degrees to 53 degrees. The results are shown in Figure 2. Figure 14 As shown, it can be seen that at 3500 Hz, when the incident angle is 51 degrees, the surface wave conversion occurs on the upper surface of the metamaterial; at 4300 Hz, when the incident angle is 52 degrees, it occurs on the lower surface of the metamaterial; at 2800 Hz, when the incident angle is 49 degrees, it occurs on both the upper and lower surfaces of the metamaterial.

[0087] This metamaterial converts propagating waves into surface waves. If foam sound-absorbing structures are added on both sides of the metamaterial, the sound absorption efficiency of the foam layer for reflected or projected sound waves can be greatly increased, providing a new idea for the design of new aviation sound insulation panels based on acoustic metamaterials.

[0088] To demonstrate the influence of the meandering cavity on the surface impedance of the metamaterial unit and confirm its wave control effect, the excitation frequency was increased to 4300 Hz. At this point, the metamaterial is less affected by the Helmholtz resonator and more dependent on the geometric parameters of the meandering cavity. To analyze the unit's phase control capability, the unit's surface impedance was calculated for different unit geometric parameters. The Helmholtz resonator throat width S was set to a range of 2 mm to 8 mm, with a 2 mm scan interval. The Helmholtz resonator throat length L was also set to a range of 2 mm to 8 mm, with a 2 mm scan interval. The meandering cavity length D was set to a range of 10 mm to 40 mm, with a 5 mm scan interval. The meandering cavity width H was set to a range of 0.5 mm to 2.5 mm, with a 0.5 mm scan interval. The curved channel outer diameter R1 was set to a range of 13.5 mm to 15 mm, with a 0.5 mm scan interval. The unit's surface impedance was calculated for different parameter combinations. Selecting geometric units from the metamaterial changes the geometric parameters of the zigzag cavity of the metamaterial unit, but without changing any other parameters outside the zigzag cavity, thus changing the anomalous reflection direction. Because the anomalous reflection direction jumps significantly, excessive differences in phase distribution between units can cause discontinuity in the reflected sound wave. Therefore, the geometric parameters of the zigzag cavity are readjusted at the junction between the units (the acoustic metamaterial is composed of many units, such as the 111222333444333222111 mentioned above. When two different units are close together, such as unit 1 and unit 2, the dimensions of the zigzag cavity of these two units need to be changed to the dimensions of the zigzag cavity at the junction of 1 and 2 in Table 2. The same applies when units 2 and 3 are close together, and when units 3 and 4 are close together. When two identical units are close together, such as units 1 and 1, or units 2 and 2, the dimensions of their zigzag cavities do not need to be changed; this is done to ensure a continuous transition in the reflected sound pressure). This results in a more continuous phase of the reflected sound pressure. The unit parameters are selected according to the impedance obtained above, and the abnormal reflected sound pressure before adjustment is compared with the abnormal reflected sound pressure after adjustment. Figure 5 The metasurface with the zigzag cavity was redesigned to change the reflected sound wave from -10 degrees to 15 degrees, as shown in Figure 5 This result demonstrates that acoustic metamaterials with bilaterally adjustable impedance can achieve sufficient bilateral impedance adjustment capabilities, enabling more flexible engineering applications to meet diverse requirements. The adjusted meandering cavity geometry is shown in Figure 2.

[0089] Table 2 Adjusted geometric dimensions of the tortuous cavity

[0090]

[0091] The specific preparation process of the above-mentioned acoustic superstructure with coordinated control of double-sided acoustic waves is as follows:

[0092] 1) Using software such as UG and COMSOL that has 3D modeling and acoustic vibration analysis capabilities, based on actual engineering application requirements, the various dimensional parameters of the present invention and the selected base material are determined, and a structural model suitable for 3D printing is generated.

[0093] 2) The designed acoustic metamaterial solid model is imported into a 3D printer, which then layers the model into several two-dimensional models, sprays resin and solidifies them layer by layer, and finally prints the complete structure.

[0094] In summary, the present invention has stronger control capabilities than existing single-sided sound wave control acoustic metamaterials and structures. In addition, the structure of the present invention is prepared using 3D printing technology, with a simple production process, low equipment and material investment costs, and strong engineering feasibility. It can be used in practical application scenarios such as aviation wall panel interlayers and building material interlayers, and has good application prospects.

[0095] The above is merely one specific embodiment of the present invention. Obviously, the present invention is not limited to the above embodiment. The dimensions, parameters, and number of structural units can vary greatly. All variations that can be directly derived or imagined by a person skilled in the art from the disclosure of the present invention should be considered to be within the scope of protection of the present invention.

Claims

1. An acoustic superstructure for coordinated control of double-sided acoustic waves, characterized by: comprising a plurality of acoustic units arranged in an array; The acoustic unit is an Ω-shaped Helmholtz resonator, wherein the sound wave inlet side and the sound wave outlet side of the Ω-shaped Helmholtz resonator are respectively located on both sides of the Ω shape, and the sound wave inlet side is provided with a tortuous cavity open on three sides; By adjusting the length and width of the tortuous cavity, the impedance of the lower surface of the acoustic unit can be adjusted; By designing the parameters of the acoustic units and arranging them periodically, it is possible to achieve a differentiated impedance arrangement on both sides of the acoustic superstructure, so that there is a phase gradient between the sound wave inlet and outlet sides of the acoustic superstructure.

2. The acoustic superstructure for coordinated control of double-sided acoustic waves according to claim 1, characterized in that: Multiple acoustic units are arranged in a two-dimensional array.

3. The acoustic superstructure for coordinated control of double-sided acoustic waves according to claim 1 or 2, characterized in that: Adjacent acoustic units are connected by base plates made of the same material.

4. The acoustic superstructure for coordinated control of double-sided acoustic waves according to claim 3, characterized in that: The acoustic unit is prepared by 3D printing technology and is made of resin.

5. The method for designing an acoustic superstructure for cooperative control of double-sided acoustic waves according to any one of claims 1 to 4, characterized in that: The following steps are involved: 1) Constructing a mapping relationship between acoustic unit impedance and configuration: Calculating the input impedance amplitude of the zigzag cavity with different geometric parameters and the impedance phase of the zigzag cavity with different geometric parameters at multiple frequencies; Calculating the input impedance amplitude of the Ω-type Helmholtz resonator throat diameter with different geometric parameters and the impedance phase of the upper and lower surfaces of the Ω-type Helmholtz resonator throat diameter with different geometric parameters; Calculate the theoretical phase spatial distribution on both sides of the acoustic unit based on the wave control physical phenomena required for practical applications; 2) According to the theoretical phase spatial distribution requirements obtained in step 1), the spatial impedance distribution form is obtained; 3) Based on the mapping relationship between acoustic unit impedance and configuration constructed in step 1), and according to the spatial impedance distribution obtained in step 2), the spatial distribution and filling of acoustic units are carried out, and the arrangement of acoustic units in the acoustic superstructure is designed so that the phase gradient on both sides of the designed acoustic superstructure meets the actual phase requirements.

6. The method for designing an acoustic superstructure for coordinated control of double-sided acoustic waves according to claim 5, characterized in that: In step 1), the geometric parameters of the zigzag cavity include the length and width of the zigzag cavity; The geometric parameters of the Ω-type Helmholtz resonator include the length and width of the throat diameter and the cavity volume of the Helmholtz resonator.

7. The method for designing an acoustic superstructure for coordinated control of double-sided acoustic waves according to claim 6, characterized in that: In step 2), the theoretical phase space distribution is a linear distribution or a parabolic distribution.

8. The method for fabricating the acoustic superstructure with double-sided acoustic wave cooperative control according to claim 1, characterized in that: S1. Using software with 3D modeling and acoustic vibration analysis capabilities, based on actual engineering application needs, and in accordance with the design method of claim 5, design and draw a physical model of an acoustic superstructure with coordinated double-sided acoustic wave control; S2. Import the acoustic superstructure solid model drawn in step S1 into a 3D printer, layer the model into several two-dimensional models, then spray resin and solidify layer by layer to print an acoustic superstructure with coordinated control of double-sided sound waves.

9. The method for fabricating an acoustic superstructure with coordinated control of double-sided acoustic waves according to claim 8, characterized in that: In S1, the software used is UG or COMSOL.

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