Laminated cross-medium sound transmission enhanced super lens and use method thereof

Abstract

The invention discloses a laminated cross-medium sound transmission enhancement super-lens and a use method, the laminated cross-medium sound transmission enhancement super-lens comprises an air-based super-structure unit, a water-based super-structure unit and a cross-shaped support frame, each super-structure unit is ring-shaped, and each unit is connected with an adjacent unit. The bottom-layer water-based superstructure unit, the middle-layer air-based superstructure unit and the top-layer air-based superstructure unit are overlapped in the thickness direction, so that the laminated annular acoustic superlens is assembled, the cross-shaped supporting frame is used for fixing each layer of superstructure unit, and through modulation of parameters of the air-based superstructure units and the water-based superstructure units, the air-based superstructure units and the top-layer air-based superstructure units are combined to form the laminated annular acoustic superlens. And cross-medium broadband sound penetration enhancement and sound bunching are realized. The impedance of the super-lens is matched with water and air, sound waves can penetrate through a water-air interface, so that cross-medium sound bunching is achieved, meanwhile, a laminated series structure and index impedance distribution are adopted, the working frequency band of the super-lens is effectively widened, and the super-lens has wide application prospects in the fields of underwater detection, cross-medium communication and the like.

Description

Technical Field

[0001] The present invention belongs to the field of acoustic devices, and in particular relates to a laminated cross-medium sound-transmitting enhanced superlens and a method of using the same. Background Art

[0002] As a new type of artificial structure, acoustic superstructure has properties that surpass the behavior of natural materials, such as negative mass density, negative bulk modulus and extreme Poisson's ratio, which brings new degrees of freedom and great possibilities for controlling sound waves. As an important category of acoustic superstructures, acoustic superlenses are a widely used device for manipulating sound waves, which has the ability to increase the intensity of sound energy in space. The ratio of acoustic impedance of the water-air interface is as high as 3600, and can only transmit 0.5% of the sound energy, which makes most acoustic superlenses only work in a uniform background medium and cannot meet the increasing needs of water-to-air communication applications. Although some acoustic superstructures can enhance the sound penetration ability at the water-air interface, their operating frequency band is narrow, and the complexity and strength of the structure cannot meet the needs of large-scale manufacturing and application.

[0003] In response to the above technical requirements, impedance matching can enable efficient energy transmission between two mismatched media, and has been widely used in electronics, acoustics, optics and other fields. The traditional quarter-wavelength matching layer theorem shows that when the thickness of the matching layer is 1 / 4λ and the acoustic impedance is the geometric mean of the acoustic impedances of the two media, perfect energy transmission across the medium can be achieved. The matching layer of the acoustic transducer has been commonly used in underwater sonar, ultrasonic transducers and medical ultrasonic sensors. However, if the two media that the sound crosses are air and water, the acoustic impedance required for the matching layer material is as high as 60 times the acoustic impedance of air, which is obviously not easy to obtain. Therefore, a simple and feasible design method is needed to be applied to the design of performance parameters of artificial structures. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the existing acoustic superlens and provide a laminated cross-medium sound-transmitting enhanced superlens and a method of use for achieving cross-medium sound penetration enhancement and sound focusing.

[0005] In order to achieve the above object, the present invention adopts the following technical solution: A laminated cross-medium sound-transmitting enhanced superlens, comprising an air-based superstructure unit composed of solid annular solid inclusions, a water-based superstructure unit composed of hollow annular solid inclusions, and a cross-shaped supporting frame; Both the air-based superstructure unit and the water-based superstructure unit are embedded structures, and each superstructure unit is annular, in which each unit is connected to the adjacent unit; the water-based superstructure unit on the bottom layer, the air-based superstructure unit on the middle layer and the air-based superstructure unit on the top layer are stacked in the thickness direction to assemble into a laminated annular acoustic superlens, and a cross-shaped support frame is used to fix each layer of superstructure units. By modulating the parameters of the air-based superstructure unit and the water-based superstructure unit, cross-medium broadband sound penetration enhancement and sound focusing are achieved.

[0006] A further improvement of the present invention is that the impedances of the air-based superstructure units of the middle layer and the water-based superstructure units of the bottom layer satisfy: ,in represents the impedance of water, represents the impedance of air, D is the total thickness of the metalens, and x is the position of each layer of the superstructure unit.

[0007] A further improvement of the present invention is that the refractive index of the air-based superstructure unit of the top layer satisfies a linear gradient distribution, so that the superlens can achieve cross-medium acoustic focusing.

[0008] A further improvement of the present invention is that the superlens is a stacked structure, and its impedance change is more continuous and has a wider operating frequency band.

[0009] A further improvement of the present invention is that the laminated cross-medium sound penetration enhanced superlens can achieve sound penetration enhancement at the water-air interface.

[0010] A further improvement of the present invention is that the laminated cross-medium sound penetration enhanced superlens can achieve sound focusing at the water-air interface.

[0011] A method for using a laminated cross-medium sound-transmitting enhanced superlens, comprising: 1) Determine the size of the air-based superstructure unit and the water-based superstructure unit according to the target operating frequency band; 2) Determine the size of the cross-shaped support frame according to the number of air-based superstructure units, stack the water-based superstructure units on the bottom layer, the air-based superstructure units on the middle layer, and the air-based superstructure units on the top layer in the thickness direction, connect them through a cross-shaped support frame, and place them at the water-air interface to achieve cross-medium sound transmission enhancement and sound focusing.

[0012] A further improvement of the present invention is that the impedances of the air-based superstructure units of the middle layer and the water-based superstructure units of the bottom layer satisfy: ,in represents the impedance of water, represents the impedance of air, D is the total thickness of the metalens, and x is the position of each layer of the superstructure unit.

[0013] A further improvement of the present invention is that the refractive index of the air-based superstructure unit of the top layer satisfies a linear gradient distribution, so that the superlens can achieve cross-medium acoustic focusing.

[0014] A further improvement of the present invention is that the superlens is a stacked structure, and its impedance change is more continuous and has a wider operating frequency band.

[0015] Compared with the prior art, the present invention has at least the following beneficial technical effects: 1. The present invention provides an exponential impedance distribution through the bottom water-based superstructure unit and the middle air-based unit, so that the acoustic superlens can achieve a broadband cross-medium sound penetration enhancement design; 2. The present invention provides a gradient refractive index distribution through the top air-based superstructure unit, so that the acoustic superlens can achieve a cross-medium sound focusing design; 3. The impedance of the acoustic superlens designed by the present invention matches that of water and air, thereby improving the sound penetration capability of the superlens at the water-air interface; 4. The present invention further broadens the working frequency band of the super lens without affecting the high transmittance of the super lens by introducing a stacked series design of super structure units; 5. The acoustic metalens designed by the present invention has a simple structure, does not require a complex design method, is easy to manufacture and apply on a large scale, and meets the requirements of compact structure and lightweight; 6. The simple structure of cross-medium sound penetration enhancement and sound beam focusing design realized by the present invention can realize cross-medium regulation of sound waves and has practical application value.

[0016] In summary, according to the above characteristics of a laminated cross-medium sound-transmitting enhanced superlens provided by the present invention, the acoustic superlens provided by the present invention can achieve cross-medium sound penetration enhancement and sound bunching, and effectively broaden the working frequency band of the superlens. The superstructure laminated series design has a wider working frequency band and has a significant sound penetration enhancement effect. The designed laminated cross-medium sound-transmitting enhanced superlens can achieve sound penetration enhancement and sound bunching at the water-air interface, has huge advantages in size and structure, and has practical engineering application value. In summary, compared with the existing superlens, the impedance of this acoustic superlens matches that of water and air, and can make sound waves pass through the water-air interface, thereby achieving cross-medium sound bunching. At the same time, the laminated series structure and exponential impedance distribution are adopted, so that its working frequency band is effectively broadened, and it has broad application prospects in the fields of underwater detection and cross-medium communication. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 (a) and (b) are schematic diagrams of air-based superstructure units and water-based superstructure units, respectively; Figure 2Plots of the effective density (blue line) and speed of sound (red line) that can be accommodated by an air-based superstructure; Figure 3 This is the structural diagram of the superlens sound penetration enhancement function module; Figure 4 It is a schematic diagram of the exponential impedance distribution curve; Figure 5 The calculated results of the energy transmission coefficient of the laminated cross-medium sound-transmitting enhanced superlens (red line) and the bare water-air interface (black line); Figure 6 This is a graph showing the results of the experimental test of the transmission amplitude enhancement of the laminated cross-medium sound transmission enhancement superlens; Figure 7 The simulated acoustic field cloud diagram of the laminated cross-medium sound-transmitting enhanced superlens and the bare water-air interface; Figure 8 This is the structural diagram of the superlens acoustic beam focusing function module; Fig. 9 is the refractive index nr diagram of the air-based superstructure unit; Fig.10 The simulated acoustic field cloud diagram of the laminated cross-medium sound-transmitting enhanced superlens at the water-air interface at the designed frequency; Fig.11 Comparison diagram of the experimental and simulated sound fields of the laminated cross-medium sound-transmitting enhanced superlens at the water-air interface at a frequency of 3450Hz; Fig.12 Comparison of simulated and experimental acoustic amplitudes on the axis of the laminated cross-medium acoustically enhanced superlens. DETAILED DESCRIPTION

[0018] The technical scheme in the implementation case of the present invention is described below in conjunction with the relevant calculation and measurement results of the implementation case of the present invention in the accompanying drawings. Obviously, the implementation case described is only a part of the implementation case of the present invention, not all the implementation cases. Based on the implementation case in the present invention, all other implementation cases obtained by those skilled in the art without making creative work belong to the scope of protection of the present invention.

[0019] Example 1 The present invention provides a laminated cross-medium sound-transmitting enhanced superlens, comprising an air-based superstructure unit 1, a water-based superstructure unit 2 and a cross-shaped support frame 3. The air-based superstructure unit 1 and the water-based superstructure unit 2 are an embedded structure, each superstructure unit is annular, and each unit is connected to an adjacent unit. The bottom layer water-based superstructure unit 2, the middle layer air-based superstructure unit 1 and the top layer air-based superstructure unit 1 are stacked in the thickness direction to assemble a laminated annular acoustic superlens. The cross-shaped support frame 3 is used to fix each layer of superstructure units. By modulating the parameters of the air-based superstructure unit 1 and the water-based superstructure unit 2, cross-medium broadband sound penetration enhancement and sound focusing are achieved.

[0020] In this embodiment, the impedances of the air-based superstructure unit 1 in the middle layer and the water-based superstructure unit 2 in the bottom layer satisfy: ,in represents the impedance of water, represents the impedance of air, D is the total thickness of the metalens, and x is the position of each layer of the superstructure unit.

[0021] In this embodiment, the refractive index of the air-based superstructure unit 1 at the top layer satisfies a linear gradient distribution, so that the superlens can achieve cross-medium acoustic focusing.

[0022] In this embodiment, the superlens is a stacked structure, and its impedance change is more continuous, and has a wider operating frequency band.

[0023] In this embodiment, the laminated cross-medium sound penetration enhanced superlens can achieve sound penetration enhancement at the water-air interface.

[0024] In this embodiment, the laminated cross-medium sound penetration enhanced superlens can achieve sound focusing at the water-air interface.

[0025] Example 2 The present invention provides a method for using a laminated cross-medium sound-transmitting enhanced superlens, comprising: 1) Determine the size of the air-based superstructure unit 1 and the water-based superstructure unit 2 according to the target operating frequency band; 2) The size of the cross-shaped support frame 3 is determined according to the number of air-based superstructure units 1, and the water-based superstructure units 2 of the bottom layer, the air-based superstructure units 1 of the middle layer, and the air-based superstructure units 1 of the top layer are stacked in the thickness direction and connected through the cross-shaped support frame 3. They are placed at the water-air interface to achieve cross-medium sound transmission enhancement and sound focusing.

[0026] Example 3 1. Design of matrix superstructure As an implementation example, the material of the air-based superstructure is a photosensitive resin material and the water-based superstructure is a rubber material. Figure 1 As shown, the air-based superstructure and water-based superstructure used in this embodiment are composed of multiple rings with the same diameter and gap. For the air-based superstructure unit, the blue part represents the solid inclusion (resin), a represents the lattice constant, and b represents the side length of the solid inclusion. The water-based superstructure unit has the same structural form as the air-based superstructure unit, but the embedded medium and the matrix medium are replaced by rubber and water respectively. Based on the effective medium theory, since the working wavelength in the superstructure is much larger than the size of the basic unit, the superstructure can be regarded as having an effective density and the effective bulk modulus The effective medium theory can intuitively reflect the propagation behavior and characteristics of waves in superstructures, and provides a theoretical basis for the wide application of superstructures in gradient refractive index lenses and invisible cloaks. For air-based superstructures, since the density of any solid material is much greater than the density of air, the extreme impedance mismatch prevents sound waves from passing through solid materials. Therefore, solid inclusions behave as rigid materials at this time, and their mass density can be regarded as infinite. Therefore, the type of material has almost no effect on the effective parameters of air-based superstructures. Considering factors such as processing and manufacturing costs and structural strength, a photosensitive resin polymer is selected, and its effective parameters can be specifically expressed as

[0027]

[0028] in , K and f are mass density, bulk modulus and volume fraction, and subscripts R and a represent resin and air, respectively. When the volume fraction is too large, there is a slight deviation between formula (22) and the accurate theoretical model calculation. For impedance calculation, this deviation can be ignored. Figure 2 As shown, by changing the size of the air-based superstructure, its density and sound speed can be varied within a large range. 2. Design and experimental verification of the superlens acoustic penetration enhancement function module As an implementation case, the superlens sound penetration enhancement function module consists of a water-based superstructure and an air-based superstructure, such as Figure 3 As shown, the two are stacked in series in the thickness direction. Functional gradient materials are widely used in sound absorption, sound focusing and sound stealth due to their superior acoustic properties. When the material is designed to have a gradient impedance change in thickness, most of the sound waves will not be reflected back at the impedance matching interface, but will be transmitted, thereby achieving enhanced broadband sound penetration. In order to match the impedance of the superlens with air and water, an exponential distribution curve is selected to couple the impedance of air and water. Its specific form is shown below,

[0029] in is the impedance of air, is the impedance of the water and D is the thickness of the structure.

[0030] By combining air-based superstructures with water-based superstructures, the present invention designs a superlens acoustic penetration enhancement function module, which overcomes the shortcomings of single-layer superlens with narrow operating frequency band and harsh impedance matching conditions. This structure can meet the requirements of broadband transmission and is very simple in form, with potential engineering application value. At the same time, by using the thickness equivalent layering method, the following can be obtained: Figure 4 The red circles show the impedance distribution. The sound speeds in the two-layer superstructure are 256.9m / s and 187.5m / s respectively. Correspondingly, the operating frequency is around 11700 and the total thickness of the structure is 9mm. Figure 5 As shown, the red line and black line represent the energy transmission coefficients of the metalens and the bare water-air interface, respectively. It can be seen that the energy transmission coefficient of the bare water-air interface is close to 0, and most of the sound is reflected by the water-air interface and is difficult to penetrate into the air. However, in the frequency range of 11000-12500Hz of the metalens, the average energy transmission is stable at above 0.85, and most of the sound can penetrate the water-air interface. The central transmission frequencies of the metalens are calculated theoretically. =11700Hz, which matches the frequency band shown in the simulation calculation results. Figure 6 As shown, the experimental results show that in the range of 9400-12500Hz, the average transmission amplitude enhancement exceeds 20dB, and the working bandwidth exceeds 700Hz. The working frequency band calculated by the simulation numerical model is 10000-12500, which is basically consistent with the experimental results. By comparing the experimental results and the simulation results, it can be found that there are differences between the experimental results and the simulation results of the two types of laminated sound penetration super lenses, but for the range of the working frequency band, the simulation and experimental results have the necessary consistency. The possible reasons for the difference between the simulation results and the experimental results come from multiple aspects. On the one hand, there are certain errors in the processing of the sample, and the structural dimensions and material parameters cannot be guaranteed to be completely consistent with the parameters set by the simulation model. On the other hand, the reflection of the water tank wall will inevitably have a certain impact on the experimental results. It is worth noting that the transmission amplitude enhancement results measured experimentally will have a certain jump between some frequency points due to the reflection of the water tank wall. As Figure 7 As shown, the transmitted sound field of the set superlens and the exposed water-air interface is given. It can be found that with the increase of the superlens, the transmitted sound pressure is significantly enhanced, which further proves that the superlens can achieve broadband penetration enhancement of water-air interface sound.

[0031] In order to facilitate testing and verification, the acoustic-solid coupling module is used in the commercial multi-physics field coupling finite element analysis software COMSOL. The acoustic superlens adopts a rigid wall design, and the rigid wall material of the air-based superstructure is selected as a photosensitive resin polymer, whose mass density, Young's modulus and Poisson's ratio are respectively = , = Pa and =0.375, the sound propagation medium is selected as air, and its sound speed and density are =343 and =1.29 ; The rigid wall material of the water-based superstructure is rubber, whose mass density, Young's modulus and Poisson's ratio are = , = Pa and =0.49, the sound propagation medium is selected as air, and its sound speed and density are =1500 and =1000

[0032] 3. Design and experimental verification of the superlens acoustic beam focusing function module Here, we first construct a superlens acoustic beamforming function module with the base superstructure as the basic unit. Different from the sound penetration enhancement module, the refractive index of the basic unit that constitutes the acoustic beamforming function module should be distributed in a linear gradient, which means that the size of each unit should be different. Figure 8 As shown in the figure, the two-dimensional cross sections corresponding to different refractive indices are arranged at different radial positions. After rotating the axis of symmetry, an acoustic beam-forming superlens can be obtained, and its refractive index decreases step by step from the center along the radial direction. The total width of the unit a = 18mm, by changing the side length b of the solid inclusion, the refractive index of the superlens can be controlled in a wide range. Fig. 9 As shown, the refractive index that can be adjusted by the structure is up to 3.8. By changing the value of the side length b, the refractive index of the structure can be adjusted within a larger span to meet the requirements of the gradient refractive index of the superlens. According to the adjustable range of the refractive index, the present invention designs a 6-unit acoustic focusing superlens. The maximum refractive index of the superlens is n_1=3.8, and the minimum is n_6=1.8, which is distributed in a linear gradient. The sizes corresponding to each unit are: b_1=13.5mm, b_2=13mm, b_3=12mm, b_4=11mm, b_5=9.5mm, b_6=7.5mm. Fig.10The simulated sound field in the figure clearly shows that the superlens has a good acoustic focusing effect within the design frequency, and can produce a certain range of focused light beams along the axis at frequencies of 3150Hz, 3250Hz, 3350Hz and 3450Hz. In order to verify the acoustic focusing performance of the acoustic superlens, a three-dimensional acoustic experimental test was carried out on the designed superlens. Fig.11 The measured sound field shown clearly shows the acoustic focusing performance of the acoustic superlens. The length of the sound beam generated by the superlens at a frequency of 3450Hz is close to 0.8m. The simulated and measured sound amplitude distributions on the lens axis are extracted and normalized. The results are shown in Fig.12 As shown in the figure, the acoustic amplitude distribution of the experiment (black dots) and the simulation (red line) at a frequency of 3450 Hz is highly consistent. The experiment proves that the designed acoustic superlens meets the design requirements and has good acoustic focusing performance.

[0033] According to the above data, it can be seen that the technical effects that the present invention can achieve are as follows: 1. The present invention provides an exponential impedance distribution through the bottom water-based superstructure unit and the middle air-based unit, so that the acoustic superlens can achieve a broadband cross-medium sound penetration enhancement design; 2. The present invention provides a gradient refractive index distribution through the top air-based superstructure unit, so that the acoustic superlens can achieve a cross-medium sound focusing design; 3. The impedance of the acoustic superlens designed by the present invention matches that of water and air, thereby improving the sound penetration capability of the superlens at the water-air interface; 4. The present invention further broadens the working frequency band of the super lens without affecting the high transmittance of the super lens by introducing a stacked series design of super structure units; 5. The acoustic metalens designed by the present invention has a simple structure, does not require a complex design method, is easy to manufacture and apply on a large scale, and meets the requirements of compact structure and lightweight; 6. The simple structure of cross-medium sound penetration enhancement and sound beam focusing design realized by the present invention can realize cross-medium regulation of sound waves and has practical application value.

[0034] In summary, according to the above characteristics of a laminated cross-medium sound-transmitting enhanced superlens provided by the present invention, the acoustic superlens provided by the present invention can achieve cross-medium sound penetration enhancement and sound bunching, and effectively broaden the working frequency band of the superlens. The superstructure laminated series design has a wider working frequency band and has a significant sound penetration enhancement effect. The designed laminated cross-medium sound-transmitting enhanced superlens can achieve sound penetration enhancement and sound bunching at the water-air interface, has huge advantages in size and structure, and has practical engineering application value. In summary, compared with the existing superlens, the impedance of this acoustic superlens matches that of water and air, and can make sound waves pass through the water-air interface, thereby achieving cross-medium sound bunching. At the same time, the laminated series structure and exponential impedance distribution are adopted, so that its working frequency band is effectively broadened, and it has broad application prospects in the fields of underwater detection and cross-medium communication.

[0035] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the attached claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention. Any figure mark in the claims should not be regarded as limiting the claims involved.

[0036] In addition, it should be understood that although this specification is described in accordance with the implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation modes that can be understood by those skilled in the art. The above content is only to illustrate the technical idea of ​​the present invention, and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution according to the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A laminated cross-medium sound-transmitting enhanced superlens, characterized in that: It comprises an air-based superstructure unit (1) composed of solid annular solid inclusions, a water-based superstructure unit (2) composed of hollow annular solid inclusions, and a cross-shaped supporting frame (3); The air-based superstructure unit (1) and the water-based superstructure unit (2) are both embedded structures, and each superstructure unit is annular, wherein each unit is connected to an adjacent unit; the water-based superstructure unit (2) at the bottom layer, the air-based superstructure unit (1) at the middle layer, and the air-based superstructure unit (1) at the top layer are stacked in the thickness direction to assemble into a laminated annular acoustic superlens; a cross-shaped support frame (3) is used to fix each layer of superstructure units, and by modulating the parameters of the air-based superstructure unit (1) and the water-based superstructure unit (2), broadband sound penetration enhancement and sound focusing across media are achieved.

2. The laminated cross-medium sound transmission enhanced superlens according to claim 1, characterized in that: The impedances of the air-based superstructure unit (1) in the middle layer and the water-based superstructure unit (2) in the bottom layer satisfy: ,in represents the impedance of water, represents the impedance of air, D is the total thickness of the metalens, and x is the position of each layer of the superstructure unit.

3. The laminated cross-medium sound transmission enhanced superlens according to claim 1, characterized in that: The refractive index of the top air-based superstructure unit (1) satisfies a linear gradient distribution, so that the superlens can achieve cross-medium acoustic focusing.

4. The laminated cross-medium sound transmission enhanced superlens according to claim 1, characterized in that: The superlens is a stacked structure with a more continuous impedance change and a wider operating frequency band.

5. The laminated cross-medium sound transmission enhanced superlens according to claim 1, characterized in that: The laminated cross-medium sound penetration enhanced superlens can achieve sound penetration enhancement at the water-air interface.

6. The laminated cross-medium sound transmission enhanced superlens according to claim 1, characterized in that: The laminated cross-medium sound penetration enhanced superlens can achieve sound focusing at the water-air interface.

7. The method for using the laminated cross-medium sound transmission enhanced superlens according to claim 1, characterized in that: include: 1) Determining the sizes of the air-based superstructure unit (1) and the water-based superstructure unit (2) according to the target operating frequency band; 2) The size of the cross-shaped support frame (3) is determined according to the number of air-based superstructure units (1), and the water-based superstructure units (2) of the bottom layer, the air-based superstructure units (1) of the middle layer, and the air-based superstructure units (1) of the top layer are stacked in the thickness direction and connected through the cross-shaped support frame (3). The cross-shaped support frame (3) is placed at the water-air interface to achieve cross-medium sound transmission enhancement and sound focusing.

8. The method for using the laminated cross-medium sound transmission enhanced superlens according to claim 7, characterized in that: The impedances of the air-based superstructure unit (1) in the middle layer and the water-based superstructure unit (2) in the bottom layer satisfy: ,in represents the impedance of water, represents the impedance of air, D is the total thickness of the metalens, and x is the position of each layer of the superstructure unit.

9. The method for using the laminated cross-medium sound transmission enhanced superlens according to claim 7, characterized in that: The refractive index of the top air-based superstructure unit (1) satisfies a linear gradient distribution, so that the superlens can achieve cross-medium acoustic focusing.

10. The method for using the laminated cross-medium sound transmission enhanced superlens according to claim 7, characterized in that: The superlens is a stacked structure with a more continuous impedance change and a wider operating frequency band.

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