Underwater sound source based on cross-water-air metasurface packaging and preparation method thereof

Abstract

The invention belongs to the technical field of acoustic signal transmission, and particularly relates to a preparation method of an underwater sound source based on cross-water and cross-air metasurface packaging, and the method comprises the steps: obtaining a waterproof cavity with a cross-water and cross-air metasurface through the target frequency range of the underwater sound source and the boundary dimension optimization of an underwater sound source element; one or more air loudspeakers are packaged in a waterproof cavity to be assembled into an underwater sound source element, and a plurality of underwater sound source elements are arrayed according to the requirement of transmitting underwater sound beams. The underwater sound source prepared by the invention has a certain broadband characteristic and adjustable directivity, and can realize cross-medium sound wave transmission more efficiently. In addition, the invention also discloses an underwater sound source based on cross-water-air super-structure surface packaging.

Description

Technical Field

[0001] The present invention belongs to the technical field of acoustic signal transmission, and in particular relates to an underwater sound source based on trans-water-air metastructure surface packaging and a preparation method thereof. Background Art

[0002] As a mechanical wave, sound waves are the main carrier of underwater long-distance propagation and communication. With the continuous development of marine science and technology, the application demand of underwater acoustic technology in multiple fields such as underwater acoustic communication, target detection and environmental monitoring is also increasing. However, since the speed of sound in water is higher than that in air, the underwater sound sources currently used for low-frequency sound wave transmission usually have larger dimensions, which makes the underwater sound source equipment face problems such as large size, heavy weight, high cost, and inflexible directionality adjustment. Therefore, how to make an underwater sound source that is both lighter and has better sound performance is an urgent problem to be solved. Summary of the invention

[0003] One of the purposes of the present invention is to provide a method for preparing an underwater sound source based on trans-water-air metasurface packaging in response to the deficiencies in the prior art, which not only improves the transmission effect of the sound signal of the underwater sound source, but also enables the underwater sound source to control the deflection direction of the sound beam emitted in the water.

[0004] In order to achieve the above object, the present invention adopts the following technical solution:

[0005] A method for preparing an underwater sound source based on trans-water-air metasurface packaging comprises the following steps:

[0006] Step 1: determining the target frequency range of the underwater sound source, determining the outer dimensions of the underwater sound source primitive, and optimizing according to the target frequency range and the outer dimensions to obtain a waterproof cavity containing a trans-water-air metasurface, wherein the waterproof cavity can efficiently transmit sound waves from the air domain inside the cavity to the water domain outside the cavity;

[0007] Step 2: Encapsulate a single or multiple air speakers inside the waterproof cavity to assemble into an underwater sound source element;

[0008] Step 3: According to the requirement of emitting underwater sound beams, a certain number of underwater sound source element arrays are arranged, and the initial emission phase distribution of the underwater sound source element arrays is set, and the directivity of the underwater sound source emission beam is adjusted and optimized to form the required underwater sound source.

[0009] Furthermore, the step one also includes: setting the shape of the underwater sound source element to a rectangular parallelepiped, and defining waterproof baffles on two opposite sides of the waterproof cavity.

[0010] Furthermore, the step one also includes: when optimizing the structure of the waterproof cavity, taking the transmittance of sound waves in the air domain inside the cavity to the water area outside the cavity with a transmittance of not less than 95% as an optimization index.

[0011] Furthermore, the step 1 also includes: optimizing the structure of the waterproof cavity using an artificial intelligence optimization algorithm. Among them, the water-air metasurface is the main design component and difficulty. It is necessary to ensure that after it is integrated with the solid frame of the entire waterproof cavity, it can ensure that the sound waves in the air domain inside the cavity can be efficiently transmitted to the water area outside the cavity.

[0012] Furthermore, the step one also includes: using 3D printing technology to produce a waterproof cavity containing a trans-water-air meta-structure surface.

[0013] Furthermore, the step 2 also includes: checking the transmission performance of a single underwater sound source element, while considering the influence of the viscous loss of solid materials. This ensures that the underwater sound source can emit greater energy into the water when there is no solid viscous loss or when there is solid viscous loss, and has certain broadband and robustness.

[0014] Furthermore, the step 2 further includes: the air speaker is selected according to a preset power of emitting a beam underwater. Specifically, an air speaker or air horn that can only emit sound in an air environment can be selected.

[0015] Furthermore, the step three also includes: the initial transmission phase distribution adopts continuous or discrete phase points, and the initial transmission phase distribution is determined according to the mode of the transmission beam and the wave field control theory. The wave field control theory can be grating diffraction theory, generalized Snell's law or other wave field control theories. The phase distribution can be used to flexibly modulate the directivity of the transmission beam in water.

[0016] Furthermore, the optimization process of the underwater sound source is to check the underwater beam emission performance of the underwater sound source element array until a preset vibration mode can be generated inside the underwater sound source element. Within the set target frequency range, the sound signal is first emitted by the air speaker, and after being incident on the cross-water-air meta-structure surface at the front end of the waterproof cavity, the microstructure inside the underwater sound source element will produce a specific vibration mode, and finally radiate efficiently into the water to form an expected underwater beam with specific directivity.

[0017] The second object of the present invention is to provide an underwater sound source based on trans-water-air metasurface packaging, comprising a plurality of underwater sound source elements arranged in an array, wherein the underwater sound source element comprises a waterproof cavity, and the trans-water-air metasurface and air speakers are respectively arranged on opposite sides of the interior of the waterproof cavity; the interior of the underwater sound source element can generate a preset vibration mode in a water environment, and then radiate the sound signal into the water.

[0018] Furthermore, when the number of the array of the underwater sound source primitives is i, the underwater sound source emits a cylindrical beam with wide-angle characteristics, and when the number of the array of the underwater sound source primitives is j, the underwater sound source emits a plane beam with directivity, i and j are both constants and i <j。

[0019] Furthermore, i is 14, and j is 40. The trans-water-air metasurface and the air speakers are both arranged in an array, and the emission range of the sound beam is determined by the external dimensions of the underwater sound source element array.

[0020] The beneficial effects of the present invention are: 1) The innovation of the present invention is to utilize the acoustic energy transmission enhancement characteristics of the metasurface in the waterproof cavity at the water-air interface, and encapsulate the light and controllable air speaker inside a solid structure with waterproof function, so that the whole structure can be immersed in water as a sound source. The sound source can efficiently transmit sound wave signals, and the sound waves in the air domain inside the cavity can be efficiently transmitted to the water area outside the cavity; 2) The present invention can arbitrarily and flexibly adjust the directivity of the underwater transmitted sound beam by adjusting parameters such as the array number of underwater sound source elements across water and air and the emission phase of the air speaker in the element. It has the characteristics of lightness and flexibility, high controllability, and easy assembly, and has extremely high practical value and application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a preparation flow chart of the present invention.

[0022] Figure 2 Schematic diagram of the operating principle of the underwater sound source based on the trans-water-air metasurface package provided by the present invention.

[0023] Figure 3 A schematic diagram of the structure of an underwater sound source based on trans-water-air metasurface packaging provided by the present invention.

[0024] Figure 4 This is a cross-sectional view of a model of an underwater sound source in Embodiment 1 of the present invention.

[0025] Figure 5 This is a diagram showing the acoustic field transmission effect of a non-spanning water-space metastructure surface used for comparison in the first embodiment of the present invention.

[0026] Figure 6 The graph shows the variation of the normalized ratio of the acoustic field transmission, reflection and incident energy of the non-spanning water-space metasurface used for comparison in the first embodiment of the present invention with frequency.

[0027] Figure 7 This is a diagram showing the effect of sound field transmission of an underwater sound source encapsulated on a trans-water-space metasurface in accordance with an embodiment of the present invention, wherein the transmission does not take into account the influence of solid viscosity loss.

[0028] Figure 8This is a diagram showing the acoustic field transmission effect of an underwater sound source encapsulated on a trans-water-space metasurface in an implementation of the present invention, wherein the transmission has taken into account the influence of solid viscosity loss.

[0029] Fig. 9 The invention implements an underwater sound source in which the normalized ratio of transmission, reflection and incident energy in the sound field varies with frequency, without considering the influence of solid viscosity loss.

[0030] Fig.10 The invention implements an underwater sound source in which the normalized ratio of transmission, reflection and incident energy in the sound field varies with frequency, wherein the influence of solid viscosity loss has been considered.

[0031] Fig.11 The transmission performance of the underwater sound source based on the trans-water-air metasurface package in embodiment 1 of the present invention is enhanced as the frequency changes compared with the front-end emission energy without the metasurface.

[0032] Fig.12 This is a cross-sectional view of a model of an underwater sound source in Embodiment 2 of the present invention.

[0033] Fig.13 This is a diagram showing the sound field transmission effect of an underwater sound source encapsulated on a trans-water-air metasurface in Example 2 of the present invention, in which the influence of solid viscosity loss is not considered.

[0034] Fig.14 This is a diagram showing the sound field transmission effect of an underwater sound source encapsulated on a trans-water-air metasurface in Example 2 of the present invention, in which the influence of solid viscosity loss has been taken into account.

[0035] Fig.15 The figure is the variation of the normalized ratio of the transmission, reflection and incident energy of the underwater sound source sound field with frequency in the second embodiment of the present invention, in which the influence of solid viscosity loss is not considered.

[0036] Fig.16 The figure shows the variation of the normalized ratio of the transmission, reflection and incident energy of the underwater sound source sound field with frequency in the second embodiment of the present invention, in which the influence of solid viscosity loss has been considered.

[0037] Fig.17 The variation of the transmission performance of the front-end emission energy enhancement as a function of frequency of the underwater sound source encapsulated based on the trans-water-air metasurface in the second embodiment of the present invention compared to the case without the metasurface.

[0038] Fig.18 This is a rendering of an underwater sound source with a cylindrical beam emitting wide-angle characteristics in the third embodiment of the present invention, in which the influence of solid viscosity loss is not considered.

[0039] Fig.19 This is a rendering of an underwater sound source with a cylindrical beam emitting wide-angle characteristics in the third embodiment of the present invention, in which the influence of solid viscosity loss has been taken into account.

[0040] Fig. 20 This is a rendering of an underwater sound source emitting a highly directional plane beam in Embodiment 3 of the present invention, in which the influence of solid viscosity loss is not considered.

[0041] Fig.21 This is a rendering of an underwater sound source emitting a highly directional plane beam in the third embodiment of the present invention, in which the influence of solid viscosity loss has been taken into account.

[0042] Fig. 22 This is a rendering of the underwater sound source that emits a bi-directional deflected plane beam in Embodiment 4 of the present invention.

[0043] Fig.23 This is a rendering of the underwater sound source that emits a unidirectional deflected plane beam in Embodiment 4 of the present invention.

[0044] Among them: 1. air speaker; 2. incident sound waves in the air domain; 3. air; 4. waterproof cavity containing trans-water-air metasurface inside; 4-1. trans-water-air metasurface shell; 4-1-1. solid area of ​​trans-water-air metasurface unit; 4-1-2. air area of ​​trans-water-air metasurface unit; 4-1-3 air waveguide area inside the shell; 4-1-4. area inside the shell where air speakers are placed; 4-1-5. solid frame outside the shell; 4-2. waterproof baffle; 5. transmitted sound waves in the water area; 6. water. DETAILED DESCRIPTION

[0045] If certain words are used in the specification and claims to refer to specific components, those skilled in the art should understand that manufacturers may use different terms to refer to the same component. This specification and claims do not use differences in names as a way to distinguish components, but use differences in the functions of components as the criteria for distinction. As mentioned throughout the specification and claims, "including" is an open term and should be interpreted as "including but not limited to". "Approximately" means that within an acceptable error range, those skilled in the art can solve technical problems within a certain error range and basically achieve technical effects.

[0046] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by the terms "up", "down", "front", "back", "left", "right", "horizontal", etc. are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0047] In the invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the invention can be understood according to specific circumstances.

[0048] In recent years, the introduction of acoustic metasurfaces has brought new avenues for the development of acoustic technology. Metasurfaces are artificially designed sub-wavelength thickness structures. By carefully designing microstructure units and optimizing unit arrangements, the propagation direction of sound waves and their reflection or transmission characteristics can be flexibly controlled. In the field of cross-medium sound wave transmission, metasurfaces can achieve impedance matching between different media within a limited thickness, improve the energy transmission efficiency of sound waves across interfaces, and have the advantages of being light, thin, and flexible to control. These excellent properties make metasurfaces show broad application prospects in the field of cross-medium sound wave transmission, such as in complex environments such as water-air interfaces. Therefore, the use of cross-water-air acoustic metasurface technology is expected to overcome the limitations of existing underwater sound sources.

[0049] The following is combined with Figures 1 to 3 The present invention is described in detail, but is not intended to be limited to the present invention.

[0050] like Figures 1 to 3 As shown, an underwater sound source based on trans-water-air metasurface encapsulation is composed of a waterproof cavity 4 containing a trans-water-air metasurface inside and an air speaker array, wherein the front end of the waterproof cavity is designed with a metasurface with a microstructure of a specific shape, and the interior is air 3, which can efficiently emit sound waves in water 6 in conjunction with the air speaker 1. Figure 2 It is a schematic diagram of the structure of the underwater sound source element, whose shape can be selected as a cuboid, and a trans-water-air meta-structure surface shell 4-1 is formed by stretching the rectangular cross-section to a certain thickness, and waterproof baffles 4-2 are added on both sides to form a waterproof cavity.

[0051] A method for preparing an underwater sound source based on trans-water-air metasurface packaging, the method comprising the steps of:

[0052] (1) Determine the target operating frequency of the underwater sound source, which can be a single frequency point or a wide frequency range, for example, 1715 Hz, so that the shape of the underwater sound source unit is a rectangular parallelepiped, the length of which in the x-axis direction can be selected as 130 mm, the width in the z-axis direction can be selected as 44 mm, and the y-axis direction can be stretched to a specified thickness as required, which can be selected as 102 mm here. Each underwater sound source unit can be installed with three air speakers 1 of about 1 inch, and the length, width and thickness of each air speaker 1 are respectively about 34 mm, 34 mm and 17 mm. Within the given shape dimensions and target frequency range, an artificial intelligence optimization algorithm is used to design a waterproof cavity 4 containing a trans-water-air metasurface, to ensure that the sound waves can be efficiently transmitted from the air domain inside the cavity to the water area outside the cavity without considering the viscous loss of the waterproof cavity or considering the viscous loss of the waterproof cavity;

[0053] (2) Encapsulating a single or multiple air speakers 1 inside a waterproof cavity to assemble into an underwater sound source primitive, and calculating the normalized energy transmittance and sound field by finite element method to verify the transmission performance of a single underwater sound source primitive;

[0054] (3) According to the requirements of emitting underwater sound beams, the number of underwater sound source element arrays can be adjusted accordingly. For example, to achieve wide-angle underwater cylindrical beam emission, 14 underwater sound source element arrays can be used. To achieve highly directive planar beam emission, 40 underwater sound source element arrays can be used. The initial emission phase distribution of the underwater sound source element array can also be further set to achieve directivity adjustment of the underwater sound source emission beam.

[0055] For example, to realize dual-directional deflected plane beam transmission, 60 underwater elements can be arrayed, and 0 phase can be specified for transmission at elements 1-15 and 31-45, and π phase can be specified for transmission at elements 16-30 and 46-60. For example, to realize unidirectional deflected plane beam transmission, 60 underwater elements can be arrayed, 0 phase can be specified for transmission at elements 1-10 and 31-40, 2π / 3 phase can be specified for transmission at elements 11-20 and 41-50, and 4π / 3 phase can be specified for transmission at elements 21-30 and 51-60.

[0056] To calibrate the underwater beam emission performance of the underwater sound source element array, at the set target frequency of 1715kHz, the sound signal can first be emitted by the air speaker 1 as an incident sound wave 2 in the air domain. After being incident on the cross-water-air meta-structure surface at the front end of the waterproof cavity, the internal microstructure of the underwater sound source element will produce a specific vibration mode, and finally radiate efficiently into the water 6, forming the expected underwater beam with a specific directivity, so that the transmitted sound wave 5 in the water area can be efficiently transmitted.

[0057] In addition, the relevant parameters of the geometric configuration can be adjusted according to artificial experience to carry out the structural design of the cross-water-air metasurface, and other algorithms such as topology optimization and reverse design strategies can also be used to carry out the structural design of the cross-water-air metasurface.

[0058] The following is combined with Figures 4 to 23 The present invention is further described in detail with reference to the following specific embodiments, but is not intended to limit the present invention.

[0059] Embodiment 1

[0060] In this embodiment 1, if Figure 4 As shown in the figure, the water-air metasurface at the front end of the waterproof cavity is reversely designed using a topology optimization program. The material parameter distribution of the 44×30 pixels (1320 in total) at the front end is optimized, and the materials of the solid area 4-1-1 and the air area 4-1-2 of the water-air metasurface unit are given respectively. The solid material parameters are set to a 3D printable resin material with a density of 1140kg / m 3 , the elastic modulus can be 3 GPa, the Poisson's ratio can be 0.41, and when considering the solid viscosity loss, the viscosity loss factor is 0.05. In addition, the density of air can be set to 1.21 kg / m 3 , the speed of sound in air can be set to 343m / s; the density of water can be set to 1000kg / m 3 , the speed of sound in water can be set to 1500m / s.

[0061] During the optimization process of the first embodiment, periodic boundary conditions are applied to the upper and lower sides of the hydroacoustic element, perfect matching layers are set at the front and rear ends to absorb sound waves, the air speaker 1 inside the waterproof cavity uses the background sound pressure field instead as the incident sound source, which is applied to the air waveguide area 4-1-3 inside the shell, the air speaker area 4-1-4 inside the shell is placed as a blank area and is used to place the air speaker 1, and the solid frame 4-1-5 outside the shell is used for waterproofing.

[0062] Figure 5 The acoustic field transmission effect diagram of the non-water-air metasurface is given for comparison. It can be seen that the sound waves can hardly be transmitted from the air domain inside the waterproof cavity to the external water area. Figure 6 The variation of the normalized energy ratios of transmission, reflection and incident energy of the corresponding sound field of the non-spanning water-air metasurface with frequency is given. It can be seen that in the frequency range of 1315Hz-2115Hz, the normalized energy ratio of the reflected wave at the incident end is close to 1. Combined with the enlarged area in the figure, the normalized energy of the front transmission wave is slightly higher than the normalized energy of the rear transmission wave, but the normalized energy ratios of the front and rear transmission waves are both close to 0.

[0063] Figure 7A diagram of the sound field transmission effect of the cross-water-air metasurface when the solid viscosity is not considered is given. It can be seen that, benefiting from the significant vibration mode of the cross-water-air metasurface, the sound waves are efficiently transmitted from the air domain inside the waterproof cavity to the water area at the external front end.

[0064] When solid viscosity needs to be considered, the corresponding results are as follows Figure 8 As shown, it can be seen that the cross-water-air metastructure surface still maintains the corresponding vibration mode, and the sound source has good emission performance.

[0065] in addition, Fig. 9 and Fig.10 The variation of the normalized ratio of the acoustic field transmission, reflection and incident energy with frequency is given without and with solid viscosity loss. The normalized energy of the incident end reflected wave at a frequency of 1315Hz in both figures is close to 1.

[0066] at last, Fig.11 The variation of the transmission performance of the front-end emission energy enhancement of the underwater sound source based on the trans-water-air metasurface package compared with the case without the metasurface with frequency is given. It can be seen that within the frequency range of 1455Hz-1900Hz, the energy enhancement ratio of the front-end transmission wave reaches 40dB (100 times), and the energy of the incident end reflection wave and the rear-end transmission is maintained at a low value, showing a good underwater sound wave emission effect within a certain wide frequency range. After considering the solid viscosity loss, the front-end transmission effect can also be maintained, which shows that the underwater sound source provided by the present invention is highly efficient.

[0067] Embodiment 2

[0068] In the second embodiment, Fig.12 As shown, in the second embodiment, other shapes of cross-water-space metasurfaces are designed, while other corresponding geometric configurations and material parameter settings are the same as those in the first embodiment.

[0069] Fig.13 A diagram of the sound field transmission effect of the cross-water-air metasurface when the solid viscosity is not considered is given. It can be seen that, benefiting from the significant vibration mode of the cross-water-air metasurface, the sound waves are efficiently transmitted from the air domain inside the waterproof cavity 4 to the water area at the external front end.

[0070] When solid viscosity needs to be considered, the corresponding results are as follows Fig.14 As shown, it can be seen that the cross-water-air metastructure surface still maintains the corresponding vibration mode, and the sound source has good emission performance.

[0071] in addition, Fig.15 and Fig.16 The variation of the normalized ratio of the acoustic field transmission, reflection and incident energy with frequency when solid viscosity loss is not considered and when solid viscosity loss is considered is given respectively. The normalized energy of the reflected wave at the incident end at a frequency of 1315Hz in both figures is close to 1.

[0072] at last, Fig.17 The variation of the transmission performance of the front-end emission energy enhancement of the underwater sound source based on the trans-water-air metasurface package compared with the case without the metasurface with frequency is given. It can be seen that within the frequency range of 1465Hz-1860Hz, the energy enhancement ratio of the front-end transmission wave reaches 40dB (100 times), and the energy of the incident end reflection wave and the rear-end transmission is maintained at a low value, showing a good underwater sound wave emission effect within a certain wide frequency range. After considering the solid viscosity loss, the good front-end transmission effect can also be maintained, which shows that the underwater sound source design and preparation method provided by the present invention has universal applicability.

[0073] Embodiment 3

[0074] In the third embodiment, according to the requirement of emitting underwater sound beams, the directivity of the underwater sound source can be adjusted by adjusting the corresponding number of underwater sound source element arrays.

[0075] Fig.18 The effect diagram of the cylindrical beam underwater sound source with wide-angle emission characteristics is given, in which the influence of solid viscosity loss is not considered, the structure of the underwater sound source element is selected from the result of Example 1, and the number of arrays of underwater sound source elements is 14. Fig.18 It can be seen that the sound waves emitted into the water from the front end have a good cylindrical wavefront and are wide-angle, while the emission from the rear end is well suppressed. Fig.19 The corresponding effect after considering the solid viscous loss is given, and the result shows that good emission performance is still maintained after considering the solid viscous loss.

[0076] Fig. 20 The effect diagram of emitting a highly directional plane beam underwater sound source is given, in which the influence of solid viscosity loss is not considered. The underwater sound source unit structure still uses the result in Example 1, but the number of underwater sound source unit arrays is 40. It can be seen that the sound waves emitted into the water from the front end have a good plane wavefront and good vertical directivity, while the emission from the rear end is well suppressed. In addition, Fig.21 The corresponding effect after considering the solid viscous loss is given, and the result shows that good emission performance is still maintained after considering the solid viscous loss.

[0077] Embodiment 4

[0078] In the fourth embodiment, according to the requirement of emitting underwater sound beams, the initial emission phase distribution of the underwater sound source element array can be further set to adjust the directivity of the underwater sound source.

[0079] Fig. 22The effect diagram of emitting a dual-directional deflected plane beam underwater sound source is given. The underwater sound source primitive structure uses the result in Example 1. The number of underwater sound source primitives in the array is 60. The 0 phase is specified for the 1-15 and 31-45 primitives, and the π phase is specified for the 16-30 and 46-60 primitives. It can be seen that regardless of whether the solid viscosity loss is considered, the sound waves emitted into the water from the front end are divided into two beams, which are distributed and emitted in two symmetrical directions, and the emission from the rear end is well suppressed, achieving the expected effect.

[0080] Fig.23 The effect diagram of emitting a single-directional deflected plane beam underwater sound source is given. The underwater sound source element structure uses the result in Example 1. The number of underwater sound source element arrays is 60. 1-10 and 31-40 elements are specified to emit a 0 phase, 11-20 and 41-50 elements are specified to emit a 2π / 3 phase, and 21-30 and 51-60 elements are specified to emit a 4π / 3 phase. It can be seen that regardless of whether the solid viscosity loss is considered, the sound waves emitted from the front end into the water are deflected to the lower left and emitted in a single direction, while the emission from the rear end is well suppressed, with good directivity, achieving the expected effect.

[0081] It can be seen that the underwater sound source of the present invention is composed of a waterproof cavity with a trans-water-air metasurface and an air speaker array, wherein the front end of the waterproof cavity is designed with a metasurface with a specific shape of microstructure, which can efficiently emit sound waves underwater in conjunction with the air speaker. The acoustic energy transmission enhancement characteristics of the metasurface at the trans-water-air interface are utilized, and the light and controllable air speaker is encapsulated inside a solid frame with a waterproof function, and finally used as a sound source for emitting underwater acoustic signals.

[0082] The underwater acoustic source designed by the present invention has certain broadband characteristics and adjustable directivity. By adjusting the number of metasurface arrays in the cavity, a cylindrical beam with wide-angle characteristics and a plane beam with high directivity can be generated. By adjusting the emission phase of the air speaker, the deflection direction of the underwater emission beam can be controlled, such as realizing the flexible emission of dual-directional or unidirectional underwater acoustic beams.

[0083] In summary, the underwater sound source provided by the present invention is light and flexible in design, has good controllability, and is easy to assemble. It can replace a single cylindrical sound source and can also be assembled into a large-area sound array, which significantly reduces the cost of the underwater sound source and simplifies the design and production process. It has important application value in engineering fields such as underwater acoustic communication, underwater navigation and positioning, underwater robot control, marine mineral resource exploration, environmental monitoring, military detection, fault monitoring, and fishery resource management.

[0084] According to the disclosure and teaching of the above description, those skilled in the art to which the present invention belongs can also change and modify the above embodiment. Therefore, the present invention is not limited to the above specific embodiment, and any obvious improvement, replacement or modification made by those skilled in the art on the basis of the present invention belongs to the protection scope of the present invention. In addition, although some specific terms are used in this specification, these terms are only for the convenience of description and do not constitute any limitation to the present invention.

Claims

1. A method for preparing an underwater sound source based on trans-water-air metasurface packaging, characterized in that: The following steps are involved: Step 1: determining a target frequency range of an underwater sound source, determining the dimensions of an underwater sound source primitive, and optimizing a waterproof cavity containing a trans-water-air metasurface according to the target frequency range and the dimensions; Step 2: Encapsulate a single or multiple air speakers inside the waterproof cavity to assemble into an underwater sound source element; Step 3: According to the requirement of emitting underwater sound beams, a certain number of underwater sound source element arrays are arranged, and the initial emission phase distribution of the underwater sound source element arrays is set, and the directivity of the underwater sound source emission beam is adjusted and optimized to form the required underwater sound source.

2. The method for preparing an underwater sound source based on trans-water-air metasurface packaging according to claim 1, characterized in that: The step one also includes: setting the shape of the underwater sound source element to a rectangular parallelepiped, and defining waterproof baffles on two opposite sides of the waterproof cavity.

3. The method for preparing an underwater sound source based on trans-water-air metasurface packaging according to claim 1, characterized in that: The step one also includes: when optimizing the structure of the waterproof cavity, taking the transmittance of sound waves in the air domain inside the cavity to the water area outside the cavity being not less than 95% as an optimization index.

4. The method for preparing an underwater sound source based on trans-water-air metasurface packaging according to claim 1, characterized in that: The step one also includes: optimizing the structure of the waterproof cavity using an artificial intelligence optimization algorithm.

5. The method for preparing an underwater sound source based on trans-water-air metasurface packaging according to claim 1, characterized in that: The step one also includes: using 3D printing technology to make a waterproof cavity containing a trans-water-air meta-structure surface.

6. The method for preparing an underwater sound source based on trans-water-air metasurface packaging according to claim 1, characterized in that: The step 2 also includes: verifying the transmission performance of a single underwater sound source element while considering the influence of viscous loss of solid materials.

7. The method for preparing an underwater sound source based on trans-water-air metasurface packaging according to claim 1, characterized in that: The step 2 also includes: the air speaker is selected according to a preset power of emitting a beam underwater.

8. The method for preparing an underwater sound source based on trans-water-air metasurface packaging as claimed in claim 1, characterized in that: The step three also includes: the initial transmission phase distribution adopts continuous or discrete phase points, the initial transmission phase distribution is determined according to the mode of the transmission beam and the wave field control theory, and the optimization process of the underwater sound source is carried out by checking the underwater beam transmission performance of the underwater sound source element array until a preset vibration mode can be generated inside the underwater sound source element.

9. An underwater sound source based on trans-water-air metasurface packaging, characterized in that: include: A plurality of underwater sound source elements are arranged in an array, wherein the underwater sound source element comprises a waterproof cavity, and opposite sides of the interior of the waterproof cavity are respectively provided with a trans-water-air metasurface and an air speaker; the interior of the underwater sound source element can generate a preset vibration mode in a water environment, and then radiate the sound signal into the water.

10. The underwater sound source based on trans-water-air metasurface packaging according to claim 9, characterized in that: When the number of the array of the underwater sound source primitives is i, the underwater sound source emits a cylindrical beam. When the number of the array of the underwater sound source primitives is j, the underwater sound source emits a plane beam with directivity. i and j are both constants and i <j。

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