Acoustic transmission metasurface mechanism and method of manufacturing the same

Abstract

The present disclosure provides an acoustic transmission metasurface mechanism and a manufacturing method thereof. The acoustic transmission metasurface mechanism comprises a plurality of metasurface units arranged in parallel and spaced apart in a horizontal direction; the metasurface units are configured in a cubic structure, and an air cavity filled with air is arranged in the metasurface units, which is suitable for forming an air layer in a state that the metasurface mechanism floats on the water surface, so as to weaken the reflection of the incident wave and the transmission wave to the sound wave by phase conversion.

Description

TECHNICAL FIELD

[0001] At least one embodiment of the present disclosure relates to the technical field of sound wave absorption, and more particularly, to an acoustic transmission metasurface mechanism and a manufacturing method thereof. BACKGROUND

[0002] Sound waves are a common means of communication in water and air, which can be applied to the fields of ocean exploration and underwater communication. When sound waves pass through the water-air interface, due to the impedance difference of more than 3600 times between the two, impedance mismatch phenomenon occurs. In ordinary scenarios, only a small amount (e.g., about 0.1%) of sound wave energy can pass through the water-air interface, making the cross-medium transmission of sound waves between water and air a great challenge. How to achieve acoustic matching between the water-air interface becomes a problem to be solved.

[0003] According to the theory of acoustic impedance matching, when a uniform medium with an impedance size of the square root of the product of the air impedance and the water impedance and a length of 1 / 4 of its own length is placed at the water-air interface, high transmission of water-air sound waves can be achieved. Such materials are difficult to find in nature and are usually artificially manufactured. Currently, artificially manufactured metasurface structures with high transmission effects are generally formed by a plurality of continuous metasurface units. However, the range of incident angles that can achieve high transmission effects by continuous metasurface units is small, and the continuous arrangement of multiple metasurface units may also cause uncontrollable deformation (such as bending) of the metasurface mechanism, thereby affecting the transmission effect of the metasurface mechanism. SUMMARY

[0004] To solve at least one of the above and other problems in the prior art, the present disclosure provides an acoustic transmission metasurface mechanism and a manufacturing method thereof, which includes a plurality of metasurface units arranged discretely, and has better transmission effect than a metasurface mechanism formed by a plurality of continuous metasurface units.

[0005] Embodiments of the present disclosure provide an acoustic transmission metasurface mechanism, which includes a plurality of metasurface units arranged in parallel and spaced apart in a horizontal direction; the metasurface units are configured in a cubic structure, and an air cavity filled with air is arranged in the metasurface units, which is suitable for forming an air layer in a state where the metasurface mechanism floats on the water surface to weaken the reflection of incident waves and transmitted waves on sound waves by phase conversion.

[0006] According to embodiments of the present disclosure, the acoustic transmission metasurface mechanism further includes a substrate, and the plurality of metasurface units are uniformly spaced apart on the substrate in a direction perpendicular to the extension direction of the substrate.

[0007] According to an embodiment of the present disclosure, the plurality of limiting grooves are uniformly and spacedly arranged on the substrate, and the lower part of the metasurface unit is fitted into the limiting groove.

[0008] According to an embodiment of the present disclosure, the spacing between the midlines of the two adjacent metasurface units is configured to be the same as the height of the metasurface unit.

[0009] According to an embodiment of the present disclosure, the height of the metasurface unit is configured to be 0.65 times the working frequency of the metasurface mechanism, and the ratio of the height to the width of the metasurface unit is configured to be 2:1.

[0010] According to an embodiment of the present disclosure, the air cavity is configured to be symmetrically constrained in up-down and / or left-right.

[0011] According to an embodiment of the present disclosure, the metasurface unit is made of epoxy resin material.

[0012] An embodiment of the present disclosure further provides a manufacturing method of an acoustic transmission metasurface mechanism, comprising: setting a working frequency of the metasurface mechanism based on an acoustic wave to be transmitted through a water-air interface, and calculating a wavelength of the acoustic wave; setting a size of a cross section of the metasurface unit of the metasurface mechanism extending in a vertical direction and a spacing between midlines of two adjacent metasurface units according to the wavelength of the acoustic wave; for each metasurface unit, iteratively assigning respective material parameters to different pixel points by using topology optimization, to generate an initial parameter matrix containing material parameters of each pixel point, wherein the pixel points are obtained by discretizing the cross section of the metasurface unit extending in the vertical direction; for each initial parameter matrix, in a case where a transmission acoustic intensity of the metasurface unit corresponding to the initial parameter matrix satisfies a preset acoustic intensity threshold, determining the initial parameter matrix as a target parameter matrix; preparing a plurality of metasurface units based on the target parameter matrix; and arranging the plurality of metasurface units at intervals based on the spacing between the midlines of the two adjacent metasurface units, to form the metasurface mechanism.

[0013] According to an embodiment of the present disclosure, for each of the above-mentioned metasurface units, the different pixel points are iteratively endowed with respective material parameters by using topology optimization, to generate an initial parameter matrix containing the material parameters of each of the above-mentioned pixel points, wherein the pixel points are obtained by discretizing the cross section of the metasurface unit extending in the vertical direction, including: performing grid processing on the cross section of the metasurface unit extending in the vertical direction, and uniformly dividing the cross section of the metasurface unit extending in the vertical direction into a plurality of pixel points according to the height direction and the width direction of the metasurface unit; and for each of the pixel points, a topology optimization model containing material parameters is established to generate an initial parameter matrix, wherein the material parameters include solid materials and gas materials; and the material parameters of each of the pixel points in the initial parameter matrix are iteratively replaced.

[0014] According to an embodiment of the present disclosure, for each of the above-mentioned initial parameter matrix, in the case that the transmission sound intensity of the metasurface unit corresponding to the initial parameter matrix satisfies a preset sound intensity threshold, the initial parameter matrix is determined as a target parameter matrix, including: configuring the incident sound intensity incident to the metasurface mechanism, and obtaining the transmission sound intensity transmitted by the metasurface mechanism after each iteration of the initial parameter matrix; and until the transmission sound intensity of the metasurface unit corresponding to the initial parameter matrix satisfies the preset sound intensity threshold, the initial parameter matrix is determined as the target parameter matrix.

[0015] According to the acoustic transmission metasurface mechanism and the manufacturing method thereof provided by the present disclosure, the air cavity of the metasurface unit is suitable for forming an air layer in the state that the metasurface mechanism floats on the water surface, so as to weaken the reflection of the incident wave and the transmission wave due to the phase transformation. Moreover, the discrete acoustic transmission metasurface mechanism formed by the plurality of metasurface units arranged in parallel and at intervals can realize high transmission in a larger incident angle range compared with the continuous acoustic transmission metasurface mechanism, and since the metasurface units are isolated from each other, the metasurface mechanism is less likely to be affected by the self-weight to cause stress concentration compared with the continuous acoustic transmission metasurface mechanism, thereby reducing the deformation of the metasurface unit. Furthermore, the plurality of metasurface units arranged in parallel and at intervals have better flexibility, and are suitable for transportation and assembly, so as to prevent the failure of the metasurface mechanism due to the damage of part of the metasurface units during the moving process. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is a front view of an acoustic transmission metasurface mechanism according to an illustrative embodiment of the present disclosure;

[0017] Figure 2 is Figure 1 is a schematic view of the size of the metasurface unit of the illustrative embodiment shown in

[0018] Figure 3 is a flow chart of a manufacturing method of an acoustic transmission metasurface mechanism according to an illustrative embodiment of the present disclosure;

[0019] Figure 4 is Figure 3 is a schematic diagram of a cross-sectional gridding process of a metasurface unit in a vertical direction in a flow chart of an illustrative embodiment;

[0020] Figure 5 is a vibration modal diagram of a metasurface unit based on an embodiment of the present disclosure;

[0021] Figure 6 is an effect diagram of transmission of a planar sound source of an acoustic transmission metasurface mechanism based on an embodiment of the present disclosure at a water-air interface; and

[0022] Figure 7 is a frequency response curve of an acoustic wave of an acoustic transmission metasurface mechanism based on an embodiment of the present disclosure and a continuous acoustic metasurface mechanism and a metasurface mechanism without configuration.

[0023] In the drawings, the meanings of the reference signs are as follows:

[0024] 1, metasurface unit;

[0025] 2, air cavity;

[0026] 3, substrate; and

[0027] 4, limiting groove. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and advantages of the present disclosure clearer, the present disclosure is further described in detail below with reference to the specific embodiments and the accompanying drawings.

[0029] The terms used herein are merely used to describe specific embodiments, and are not intended to limit the present disclosure. The terms "include", "contain" and the like used herein indicate the existence of the described features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0030] All terms used herein, including technical and scientific terms, have meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein should be interpreted to have meanings consistent with the context of the present specification, and should not be interpreted in an idealized or overly formal manner.

[0031] In the case of using expressions similar to "at least one of A, B, and C", it will be understood that the meaning is that "only A", "only B", "only C", "at least one of A and B", "at least one of A and C", "at least one of B and C", "at least one of A, B, and C", "at least one of A, B, and C, etc. are included.

[0032] Figure 1 is a front view of an acoustic transmission metasurface mechanism according to an exemplary embodiment of the present disclosure.

[0033] According to the acoustic transmission metasurface mechanism provided by the present disclosure, as shown in Figure 1 , a plurality of metasurface units 1 are arranged in parallel and spaced apart in the horizontal direction. The metasurface unit 1 is configured in a cubic structure, and an air cavity 2 filled with air is arranged inside the metasurface unit 1, which is suitable for forming an air layer in the state of the metasurface mechanism floating on the water surface, so as to weaken the reflection of the incident wave and the transmission wave to the acoustic wave.

[0034] In such an embodiment, the discrete acoustic transmission metasurface mechanism is formed by a plurality of metasurface units arranged in parallel and spaced apart. Compared with the continuous acoustic transmission metasurface mechanism, it can achieve high transmission in a larger incident angle range, and because the metasurface units are isolated from each other, compared with the continuous acoustic transmission metasurface mechanism, it is not easy to cause stress concentration due to self-weight, and the deformation of the metasurface unit is reduced. Further, the plurality of metasurface units arranged in parallel and spaced apart have better flexibility, which is suitable for transportation and assembly to prevent the failure of the metasurface mechanism due to the damage of part of the metasurface units during the moving process.

[0035] According to the embodiment of the present disclosure, as shown in Figure 1 , the acoustic transmission metasurface mechanism further comprises a substrate 3, and the plurality of metasurface units 1 are uniformly spaced apart on the substrate 3 in a direction perpendicular to the extension direction of the substrate 3.

[0036] According to the embodiment of the present disclosure, as shown in Figure 1 , a plurality of limiting grooves 4 are uniformly arranged on the substrate 3, and the lower part of the metasurface unit 1 is embedded in the limiting groove 4.

[0037] In an illustrative embodiment, the substrate 3 comprises, but is not limited to, a frame structure configured in a rectangular shape. In detail, the upper surface of the substrate 3 is provided with a limiting groove 4 for accommodating the metasurface unit. Further, the substrate comprises, but is not limited to, a foam material, which is suitable for floating the metasurface mechanism on the water surface. It should be understood that the embodiments of the present disclosure are not limited thereto.

[0038] For example, the metasurface mechanism can also be configured with other rigid structure frames, and the substrate and / or the plurality of metasurface units are arranged on the frame to improve the strength of the metasurface structure and maintain the spacing between adjacent metasurface units.

[0039] According to an embodiment of the present disclosure, as shown in Figure 1 , the air cavity 2 is configured to be symmetrically constrained in the up-down direction and / or the left-right direction.

[0040] In an illustrative embodiment, as shown in Figure 1 , the air cavity is configured to be symmetrically constrained in the left-right direction. It should be understood that the embodiments of the present disclosure are not limited thereto.

[0041] For example, the air cavity can be configured to be symmetrically constrained in the up-down direction or both the up-down direction and the left-right direction.

[0042] In such an embodiment, the transmission of the metasurface unit to the sound wave mainly depends on the distribution of the solid material, and therefore, the shape of the air cavity in the cross section of the metasurface unit in the vertical direction should be appropriate to meet the requirement of the transmission rate, and is not limited to the left-right symmetric constraint and the up-down symmetric constraint. Wherein, the air cavity is configured to be symmetrically constrained in the left-right direction and / or the up-down direction mainly to improve the simplicity of the processing process, and the specific constraint form can be changed according to different requirements (such as use scenarios, working frequency and transmission rate, etc.).

[0043] According to an embodiment of the present disclosure, the metasurface unit 1 comprises an epoxy resin material.

[0044] Figure 2 is Figure 1 a schematic diagram of the size of the metasurface unit in the illustrative embodiment shown in

[0045] According to an embodiment of the present disclosure, as shown in Figure 2 , the spacing between the center lines of the two adjacent metasurface units 1 is configured to be substantially the same as the height of the metasurface unit 1.

[0046] According to an embodiment of the present disclosure, as shown in Figure 2 , the height of the metasurface unit 1 is configured to be 0.65 times the working frequency of the metasurface mechanism, and the ratio of the height to the width of the metasurface unit 1 is configured to be 2:1.

[0047] Figure 3is a flowchart of a manufacturing method of an acoustic transmission metasurface mechanism according to an illustrative embodiment of the present disclosure.

[0048] The manufacturing method of the acoustic transmission metasurface mechanism provided according to the present disclosure, as shown in Figure 3 includes operations S510-S560.

[0049] Operation S510: setting a working frequency of the metasurface mechanism based on an acoustic wave to be transmitted through a water-air interface, and calculating a wavelength of the acoustic wave;

[0050] Operation S520: setting a size of a cross section of a metasurface unit of the metasurface mechanism extending along a vertical direction and a distance between midlines of two adjacent metasurface units according to the wavelength of the acoustic wave;

[0051] Operation S530: for each metasurface unit, iteratively assigning respective material parameters to different pixel points using topology optimization, to generate an initial parameter matrix containing the material parameters of the pixel points, wherein the pixel points are discretized from the cross section of the metasurface unit extending along the vertical direction;

[0052] Operation S540: for each initial parameter matrix, determining the initial parameter matrix as a target parameter matrix in a case where a transmission acoustic intensity of the metasurface unit corresponding to the initial parameter matrix satisfies a preset acoustic intensity threshold;

[0053] Operation S550: preparing a plurality of metasurface units based on the target parameter matrix;

[0054] Operation S560: arranging the plurality of metasurface units at intervals based on the distance between the midlines of the two adjacent metasurface units, to form the metasurface mechanism.

[0055] In an illustrative embodiment, operation S510 of setting a working frequency of the metasurface mechanism based on an acoustic wave to be transmitted through a water-air interface, and calculating a wavelength of the acoustic wave includes operations S511-S512.

[0056] Operation S511: setting a working frequency f of the metasurface mechanism according to the acoustic wave to be transmitted through the water-air interface;

[0057] Operation S512: calculating the wavelength λ of the acoustic wave according to a wavelength calculation formula (λ = c / f, where c represents a sound speed of the acoustic wave in air).

[0058] In an illustrative embodiment, operation S520 of setting a size of a cross section of a metasurface unit of the metasurface mechanism extending along a vertical direction and a distance between midlines of two adjacent metasurface units according to the wavelength of the acoustic wave includes operations S521-S522.

[0059] Operation S521: configuring the size of the cross section of the metasurface unit along the vertical direction according to the wavelength λ of the sound wave, wherein the size of the cross section of the metasurface unit along the vertical direction includes the height (h) and the width (w).

[0060] Operation S522: configuring the distance (d) between the midlines of the two adjacent metasurface units along the vertical direction according to the height (h) of the cross section of the metasurface unit along the vertical direction.

[0061] In an illustrative embodiment, the height of the metasurface unit is configured to be 0.65λ, and the height of the metasurface unit includes but is not limited to being configured to be twice the width (i.e., h = 2w), and further, the distance between the midlines of the two adjacent metasurface units along the vertical direction is configured to be substantially the same as the height of the metasurface unit (i.e., h = d). It should be understood that embodiments of the present disclosure are not limited thereto.

[0062] For example, the value of any one of the above h, w and d can be set by historical data or can be obtained by calculating the optimal solution with a preset target (e.g., the degree of attenuation of the sound intensity transmitted through the metasurface mechanism).

[0063] According to an embodiment of the present disclosure, operation S530 iteratively assigns respective material parameters to different pixel points using topology optimization for each metasurface unit to generate an initial parameter matrix containing the material parameters of the pixel points, wherein the pixel points are obtained by discretizing the cross section extending along the vertical direction of the metasurface unit, including operation S531 to operation S533.

[0064] Operation S531: grid processing the cross section extending along the vertical direction of the metasurface unit, and uniformly dividing the cross section extending along the vertical direction of the metasurface unit into a plurality of pixel points according to the height direction and the width direction of the metasurface unit;

[0065] Operation S532: assigning respective material parameters to each pixel point to establish a topology optimization model containing material parameters to generate an initial parameter matrix, wherein the material parameters include solid materials and gas materials;

[0066] Operation S533: iteratively replacing the material parameters of each pixel point in the initial parameter matrix to generate a plurality of initial parameter matrices.

[0067] In an illustrative embodiment, operation S531 grid processes the cross section extending along the vertical direction of the metasurface unit, and uniformly divides the cross section extending along the vertical direction of the metasurface unit into a plurality of pixel points according to the height direction and the width direction of the metasurface unit, including: setting the size of the pixel points, and dividing the cross section extending along the vertical direction of the metasurface unit into n x m pixel points according to the size of the pixel points and the height (h) and the width (w) of the metasurface unit. Wherein n and m are both integers greater than zero.

[0068] Figure 4 is Figure 3 a schematic diagram of the cross-sectional meshing process of the vertically extending super surface unit in the flowchart of the schematic embodiment.

[0069] In a schematic embodiment, as Figure 4 shown, operation S532 assigns respective material parameters to each pixel point to establish a topology optimization model including material parameters to generate an initial parameter matrix, wherein the material parameters include solid materials and gas materials, including:

[0070] The solid material is configured as "1" and the gas material is configured as "0". The topology optimization model is established and each pixel point is respectively assigned as "1" or "0" as an initial parameter matrix.

[0071] Figure 5 is the effect of acoustic wave transmission at the water-air interface and the vibration modal diagram of the super surface unit based on the acoustic transmission super surface mechanism of the embodiment of the present disclosure.

[0072] Referring to Figure 5 , the effect diagram and the vibration modal diagram of the acoustic wave transmission from the water side of the water-air interface are shown. As Figure 5 shown, in the process of acoustic wave transmission, the vibration of the solid material forming the super surface unit has a great influence on the transmission rate of the acoustic wave across the water-air interface. Therefore, in a schematic embodiment, the solid material includes but is not limited to being configured as a linear elastic body to meet the requirements of acoustic-solid coupling generated by the acoustic wave through the super surface mechanism.

[0073] According to the embodiment of the present disclosure, operation 540 determines the initial parameter matrix as a target parameter matrix in the case that the transmission acoustic intensity of the super surface unit corresponding to the initial parameter matrix meets a preset acoustic intensity threshold for each initial parameter matrix, including operation S541 and operation S542.

[0074] Operation S541: configuring the incident acoustic intensity incident to the super surface mechanism and obtaining the transmission acoustic intensity transmitted by the super surface mechanism of the initial parameter matrix after each iteration;

[0075] Operation S542: determining the initial parameter matrix as a target parameter matrix until the transmission acoustic intensity of the super surface unit corresponding to the initial parameter matrix meets the preset acoustic intensity threshold.

[0076] In an illustrative implementation, operation S541 configuring the incident sound intensity incident to the metasurface mechanism and obtaining the transmitted sound intensity transmitted by the metasurface mechanism after each iteration of the initial parameter matrix includes: taking the metasurface mechanism configured at the water-air interface as a use scenario, configuring a sound source to form a sound wave (including but not limited to any one of a plane wave, a Gaussian plane wave, and a cylindrical wave). Further, it also includes configuring the incident sound intensity and the incident direction of the sound source (including incident from the water side to the air side or incident from the air side to the water side). Still further, it also includes obtaining the transmitted sound intensity through the metasurface mechanism after each iteration.

[0077] In an illustrative embodiment, operation S542 determines the initial parameter matrix as the target parameter matrix until the transmitted sound intensity of the metasurface unit corresponding to the initial parameter matrix meets the preset sound intensity threshold. Since the configured incident sound intensity is controllable and known, the transmittance of the metasurface mechanism (i.e., the ratio of the transmitted sound intensity to the incident sound intensity) can be obtained by obtaining the corresponding transmitted sound intensity. When the transmitted sound intensity meets the preset sound intensity threshold (the target transmittance can be preset, such as 99%, 99.9%, or other values), the initial parameter matrix that meets the sound intensity threshold can be taken as the target parameter matrix (i.e., the optimal initial parameter matrix). For the process of obtaining the target parameter matrix from the initial parameter matrix in step S542, it includes but is not limited to using a genetic algorithm for optimization processing, and using parallel computing to obtain the target parameter matrix in the data optimization process.

[0078] In such an implementation, by combining topology optimization and genetic algorithm, the transmittance of each metasurface unit can be calculated under periodic boundary conditions, and the target parameter matrix with the highest transmittance is selected to prepare the metasurface unit to achieve impedance adjustment of the water-air interface, thereby obtaining the optimal metasurface mechanism. In the calculation process, parallel computing can effectively improve the model optimization processing efficiency.

[0079] In an illustrative embodiment, operation 550 preparing a plurality of metasurface units based on the target parameter matrix includes but is not limited to using a 3D printing method to prepare a plurality of metasurface units and / or a substrate. Further, operation S560 arranges a plurality of metasurface units based on the spacing interval of the center lines of adjacent two metasurface units to form a metasurface mechanism, which includes arranging the prepared plurality of metasurface units in the limiting grooves formed by the substrate to arrange the plurality of metasurface units in parallel and spaced apart to form the metasurface mechanism.

[0080] In an illustrative embodiment, the operating frequency of the metasurface mechanism is configured as f = 10 kHz, the sound speed of the sound wave in air is c = 346 m / s, and based on the wavelength calculation formula, λ = 3.46 cm. Further, the height h in the metasurface unit is configured as 2.28 cm, and the width w is configured as 1.14 cm. Further, the spacing d between the center lines of two adjacent metasurface units is configured as 2.28 cm.

[0081] In an illustrative embodiment, based on the cross section of the metasurface unit of 2.28 cm x 1.14 cm, the size of each pixel is configured as a 0.95 mm x 0.95 mm square, so that the cross section of the metasurface unit extending in the vertical direction is configured as a rectangular matrix of n = 24, m = 12 (including 288 pixels). Further, in the cross section of the metasurface unit in the vertical direction, the solid material and the gas material are configured in the form as shown in Figure 1 Further, the elastic modulus of the epoxy resin used is configured as E = 2.65 GPa; the density is configured as p = 1180 kg·m -3 ; and the Poisson's ratio is configured as v = 0.41.

[0082] In an illustrative embodiment, the metasurface mechanism includes a plurality of parallel and spaced metasurface units, and the lower part of each metasurface unit is fixed on a substrate as shown in Figure 1 The substrate is made of foam material, and the thickness is appropriate to fix the metasurface unit. The number of metasurface units includes but is not limited to 10, 20, 30 or any other number.

[0083] Based on the above metasurface mechanism, the transmittance of the sound wave of the plane wave beam generated by the plane sound source is obtained by experiment.

[0084] Figure 6 is an effect diagram of the transmission of the plane sound source of the acoustic transmission metasurface mechanism based on the embodiment of the present disclosure at the water-air interface.

[0085] Referring to Figure 6 , in the process of transmission of the sound wave from the water side to the air side of the water-air interface, the air side forms a clear transmission wave, and the intensity of the transmission sound intensity corresponding to the transmission wave is substantially the same as the incident sound intensity of the device, so it can be known that the above metasurface mechanism has good transmission effect for the sound wave with a frequency of 10 kHz, and the transmittance is close to 100%.

[0086] Figure 7is the frequency response curve of the acoustic wave of the acoustic transmission metasurface mechanism and the continuous acoustic metasurface mechanism based on the embodiments of the present disclosure and the acoustic wave of the acoustic wave without the metasurface mechanism.

[0087] Figure 7 The horizontal axis in the figure is the working frequency of the metasurface unit (unit: kHz), and the vertical axis is the sound pressure (sound pressure is positively correlated with sound intensity, so sound intensity can be represented by sound pressure, unit: mPa).

[0088] Further, Figure 7 The solid line in the figure represents the sound pressure-frequency curve of the water-air interface without the metasurface mechanism; the dotted horizontal line (i.e., -.) represents the sound pressure-frequency curve of the above-mentioned metasurface mechanism (discrete type); and the horizontal dashed line (i.e., --) represents the sound pressure-frequency curve of the metasurface mechanism with continuous metasurface units (continuous type).

[0089] In such an embodiment, with reference to Figure 7 As shown in the figure, the sound pressure-frequency curve of the above-mentioned metasurface mechanism has a peak value of 25 mPa at a working frequency of 10 kHz to 12 kHz. The discrete metasurface mechanism improves the peak value of the sound pressure to 30 mPa compared with the continuous metasurface mechanism. Therefore, the metasurface mechanism provided by the present disclosure has better transmission than the continuous metasurface mechanism.

[0090] It should be further noted that the directional terms mentioned in the embodiments, such as "up", "down", "front", "back", "left", "right", etc., are only the directions of the drawings and are not intended to limit the protection scope of the present disclosure. Throughout the drawings, the same elements are represented by the same or similar reference numerals. When the conventional structures or configurations may cause confusion to the understanding of the present disclosure, they will be omitted.

[0091] The embodiments of the present disclosure are described above. However, these embodiments are only for illustrative purposes, and are not intended to limit the scope of the present disclosure. Although each embodiment is described above, this does not mean that the measures in each embodiment cannot be used advantageously in combination. The scope of the present disclosure is defined by the appended claims and their equivalents. Without departing from the scope of the present disclosure, those skilled in the art can make various substitutions and modifications, which should all fall within the scope of the present disclosure.

Claims

1. An acoustically transmissive metasurface mechanism, characterized in that, The super surface unit (1) is configured in a cuboid structure, and an air cavity (2) filled with air is arranged inside the super surface unit (1), which is suitable for forming an air layer to weaken the reflection of incident waves and transmitted waves to sound waves in the state that the super surface mechanism floats on the water surface. A substrate (3) is provided, and a plurality of super surface units (1) are uniformly and spacedly arranged on the substrate (3) along the extension direction of the substrate (3). The spacing between the vertical midlines of two adjacent super surface units (1) is configured to be the same as the height of the super surface unit (1). A plurality of limiting grooves (4) are uniformly and spacedly arranged on the substrate (3), and the lower part of the super surface unit (1) is fitted into the limiting groove (4).

2. The metasurface mechanism of claim 1, wherein, The height of the super surface unit (1) is configured to be 0.65 times the working frequency of the super surface mechanism, and the ratio of the height to the width of the super surface unit (1) is configured to be 2:

1.

3. The metasurface mechanism of claim 1 or 2, wherein, The air cavity (2) is configured to be symmetrically constrained up and down and / or left and right.

4. The metasurface mechanism of claim 1 or 2, wherein, The super surface unit (1) is made of epoxy resin material.

5. The metasurface mechanism of claim 1 or 2, wherein, Comprising:

6. The method of fabricating an acoustically transmissive metasurface mechanism of any one of claims 1 to 5, wherein, Setting the working frequency of the super surface mechanism based on the sound wave that needs to be transmitted through the water-air interface, and calculating the wavelength of the sound wave; According to the wavelength of the sound wave, the size of the cross section of the super surface unit of the super surface mechanism extending in the vertical direction and the spacing of the vertical midlines of two adjacent super surface units are set; For each super surface unit, iteratively assign different pixel points with their own material parameters using topology optimization to generate an initial parameter matrix containing the material parameters of each pixel point, wherein the pixel points are obtained by discretizing the cross section extending in the vertical direction of the super surface unit; For each initial parameter matrix, if the transmitted sound intensity of the super surface unit corresponding to the initial parameter matrix satisfies the preset sound intensity threshold, the initial parameter matrix is determined as a target parameter matrix; Based on the target parameter matrix, a plurality of super surface units are prepared; and Based on the spacing of the vertical midlines of two adjacent super surface units, a plurality of super surface units are arranged to form a super surface mechanism. The method for assigning different pixel points with their own material parameters using topology optimization to generate an initial parameter matrix containing the material parameters of each pixel point for each super surface unit, wherein the pixel points are obtained by discretizing the cross section extending in the vertical direction of the super surface unit, comprises:

7. The method of manufacturing according to claim 6, wherein, Grid processing is performed on the cross section extending in the vertical direction of the super surface unit, and the cross section extending in the vertical direction of the super surface unit is uniformly divided into a plurality of pixel points according to the height direction and the width direction of the super surface unit; For each pixel point, a topology optimization model including material parameters is established to generate an initial parameter matrix, wherein the material parameters include solid materials and gas materials; and Iteratively replace the material parameters of each pixel point in the initial parameter matrix. ​ 8. The method of manufacturing according to claim 7, wherein, The determining, for each of the initial parameter matrices, the initial parameter matrix as the target parameter matrix in a case where a transmission sound intensity of a metasurface unit corresponding to the initial parameter matrix satisfies a preset sound intensity threshold value, comprises: configuring an incident sound intensity incident to the metasurface mechanism, and obtaining a transmission sound intensity of the initial parameter matrix transmitted by the metasurface mechanism after each iteration; and until the initial parameter matrix is determined as the target parameter matrix in a case where a transmission sound intensity of a metasurface unit corresponding to the initial parameter matrix satisfies a preset sound intensity threshold value.

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