An underwater acoustic source based on trans-water-space metasurface encapsulation and its fabrication method

Abstract

This invention belongs to the field of acoustic signal transmission technology, specifically relating to a method for fabricating an underwater sound source based on a trans-water-space metasurface encapsulation. By optimizing the target frequency range and the external dimensions of the underwater sound source element, a waterproof cavity containing a trans-water-space metasurface is obtained. One or more air loudspeakers are encapsulated inside the waterproof cavity, assembling into an underwater sound source element. Depending on the requirements for transmitting underwater sound beams, several underwater sound source elements are arrayed. The underwater sound source fabricated by this invention possesses certain broadband characteristics and adjustable directivity, enabling more efficient trans-medium sound wave transmission. Furthermore, this invention also discloses an underwater sound source based on a trans-water-space metasurface encapsulation.

Description

Technical Field

[0001] This invention belongs to the field of acoustic signal transmission technology, specifically relating to an underwater sound source based on trans-water-space metasurface encapsulation and its preparation method. Background Technology

[0002] Sound waves, as a type of mechanical wave, are currently the primary carrier for long-distance underwater propagation and communication. With the continuous development of marine technology, the demand for underwater acoustic technology in various fields such as underwater acoustic communication, target detection, and environmental monitoring is increasing. However, because the speed of sound in water is higher than in air, underwater sound sources currently used for low-frequency sound wave emission are typically large in size, resulting in problems such as bulky size, heavy weight, high cost, and inflexible directivity adjustment. Therefore, how to manufacture underwater sound sources that are both lighter and have better sound emission performance is an urgent problem to be solved. Summary of the Invention

[0003] One of the objectives of this invention is to provide a method for preparing an underwater sound source based on trans-water-space metasurface encapsulation, which not only improves the transmission effect of the sound signal of the prepared underwater sound source, but also enables the underwater sound source to control the deflection direction of the emitted sound beam in the water.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A method for fabricating an underwater sound source based on trans-water-space metasurface encapsulation includes the following steps:

[0006] Step 1: Determine the target frequency range of the underwater sound source and the external dimensions of the underwater sound source element. Based on the target frequency range and the external dimensions, optimize the waterproof cavity containing a trans-water-air metasurface. This waterproof cavity allows sound waves to be efficiently transmitted from the air domain inside the cavity to the water outside the cavity.

[0007] Step 2: Encapsulate one or more air loudspeakers inside the waterproof cavity to assemble an underwater sound source unit;

[0008] Step 3: Based on the requirements for transmitting underwater sound beams, a certain number of underwater sound source element arrays are prepared, and the initial transmission phase distribution of the underwater sound source element arrays is set. The directivity of the underwater sound source transmission beam is adjusted and optimized to form the required underwater sound source.

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

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

[0011] Furthermore, step one also includes: optimizing the structure of the waterproof cavity using artificial intelligence optimization algorithms. The trans-water-air metasurface is a key design component and a major challenge, requiring integration with the solid frame of the entire waterproof cavity to ensure efficient transmission of sound waves from the internal air domain to the external water area.

[0012] Furthermore, step one also includes: using 3D printing technology to create a waterproof cavity containing a trans-water-space metasurface.

[0013] Furthermore, step two also includes: verifying the transmission performance of a single underwater sound source element, while considering the influence of viscous loss of solid materials. This ensures that the underwater sound source can emit significant energy into the water both with and without solid viscous loss, and possesses a certain degree of broadband and robustness.

[0014] Furthermore, step two also includes: the air loudspeaker is selected based on a preset power for transmitting the beam underwater. Specifically, an air loudspeaker or air horn that can only emit sound in an air environment can be selected.

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

[0016] Furthermore, the optimization process of the underwater sound source involves verifying the underwater beam emission performance of the underwater sound source element array until the underwater sound source element can generate a preset vibration mode. Within the set target frequency range, the sound signal is first emitted by an air loudspeaker, and after being incident on the trans-water-air metasurface at the front end of the waterproof cavity, the microstructure inside the underwater sound source element will generate a specific vibration mode, and finally radiate efficiently into the water, forming the expected specific directional underwater beam.

[0017] The second objective of this invention is to provide an underwater sound source based on a trans-water-space metasurface encapsulation, comprising a plurality of arrayed underwater sound source elements. Each underwater sound source element includes a waterproof cavity, and trans-water-space metasurfaces and air loudspeakers are respectively arranged on opposite sides inside the waterproof cavity. The underwater sound source element is capable of generating a preset vibration mode in the water environment and then radiating the sound signal into the water.

[0018] Furthermore, when the number of underwater sound source elements in the array is i, the underwater sound source emits a cylindrical beam with wide-angle characteristics; when the number of underwater sound source elements in the array is j, the underwater sound source emits a planar beam with directional characteristics, where i and j are both constants and i <j。

[0019] Furthermore, i is 14 and j is 40. Both the trans-water-air metasurface and the air loudspeaker are 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 this invention are as follows: 1) The innovation of this invention is to utilize the enhanced acoustic energy transmission characteristics of the metasurface in the waterproof cavity at the water-air interface, and to encapsulate a lightweight and controllable air loudspeaker in a waterproof solid structure. The entire structure can be submerged underwater as a sound source, which can efficiently emit sound wave signals. The sound waves in the air domain inside the cavity can be efficiently transmitted to the water outside the cavity; 2) This invention allows for arbitrary and flexible adjustment of the directivity of the underwater sound beam by adjusting the array number of the underwater sound source elements and the emission phase of the air loudspeaker in the elements. It is lightweight, flexible, highly controllable, and easy to assemble, and has extremely high practical and application value. Attached Figure Description

[0021] Figure 1 This is a flowchart illustrating the preparation process of the present invention.

[0022] Figure 2 This is a schematic diagram illustrating the operating principle of an underwater sound source based on trans-water-space metasurface encapsulation, as provided by the present invention.

[0023] Figure 3 This is a schematic diagram of the underwater sound source based on trans-water-space metasurface encapsulation provided by the present invention.

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

[0025] Figure 5 This is a diagram showing the sound field transmission effect of a non-water-space metasurface used for comparison in one embodiment of the present invention.

[0026] Figure 6 The normalized ratio of acoustic field transmission, reflection, and incident energy as a function of frequency is shown for a control on a trans-aqueous metasurface used in an embodiment of the present invention.

[0027] Figure 7 This is a sound field transmission effect diagram of an underwater sound source based on a trans-water-air metasurface encapsulation according to an embodiment of the present invention. The transmission does not consider the influence of solid viscous loss.

[0028] Figure 8This is a sound field transmission effect diagram of an underwater sound source based on a trans-water-air metasurface encapsulation according to an embodiment of the present invention. The transmission has taken into account the influence of solid viscous loss.

[0029] Figure 9 This invention describes the variation of the normalized ratio of transmitted, reflected, and incident energy of an underwater sound source with frequency, without considering the influence of solid viscous loss.

[0030] Figure 10 To implement this invention, the normalized ratio of the transmitted, reflected, and incident energy of an underwater sound source varies with frequency, taking into account the influence of solid viscous loss.

[0031] Figure 11 This invention relates to an underwater sound source based on a trans-water-air metasurface encapsulation, which, compared to the source without a metasurface, enhances front-end emission energy and transmission performance with frequency.

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

[0033] Figure 13 This is a sound field transmission effect diagram of an underwater sound source based on a trans-water-space metasurface encapsulation in Embodiment 2 of the present invention, where the influence of solid viscous loss is not considered.

[0034] Figure 14 This is a sound field transmission effect diagram of an underwater sound source based on a trans-water-air metasurface encapsulation in Embodiment 2 of the present invention, where the influence of solid viscous loss has been taken into account.

[0035] Figure 15 This refers to the change of the normalized ratio of transmitted, reflected, and incident energy of the underwater sound source with frequency in Embodiment 2 of the present invention, without considering the influence of solid viscous loss.

[0036] Figure 16 The normalized ratio of the transmitted, reflected, and incident energy of the underwater sound source in Embodiment 2 of the present invention varies with frequency, taking into account the influence of solid viscous loss.

[0037] Figure 17 The variation of the enhanced transmission performance of the underwater sound source based on the trans-water-air metasurface encapsulation in Embodiment 2 of the present invention with frequency compared to the form without the metasurface.

[0038] Figure 18 This is a rendering of the cylindrical beam underwater sound source with wide-angle emission characteristics in Embodiment 3 of the present invention, where the influence of solid viscous loss is not considered.

[0039] Figure 19 This is a rendering of the cylindrical beam underwater sound source with wide-angle emission characteristics in Embodiment 3 of the present invention, where the influence of solid viscous loss has been taken into account.

[0040] Figure 20 This is a diagram illustrating the effect of emitting a highly directional planar beam underwater sound source in Embodiment 3 of the present invention, where the influence of solid viscous loss is not considered.

[0041] Figure 21 This is a diagram illustrating the effect of emitting a highly directional planar beam underwater sound source in Embodiment 3 of the present invention, where the influence of solid viscous loss has been taken into account.

[0042] Figure 22 This is a diagram illustrating the effect of an underwater sound source emitting a bidirectional deflecting plane beam in Embodiment 4 of the present invention.

[0043] Figure 23 This is a diagram illustrating the effect of an underwater sound source emitting a unidirectional deflecting plane beam in Embodiment 4 of the present invention.

[0044] Among them: 1. Air loudspeaker; 2. Incident sound wave in the air domain; 3. Air; 4. Waterproof cavity containing a trans-water-air metasurface; 4-1. Trans-water-air metasurface shell; 4-1-1. Trans-water-air metasurface unit solid region; 4-1-2. Trans-water-air metasurface unit air region; 4-1-3. Air waveguide region inside the shell; 4-1-4. Air loudspeaker placement region inside the shell; 4-1-5. Solid frame outside the shell; 4-2. Waterproof baffle; 5. Transmitted sound wave in the water; 6. Water. Detailed Implementation

[0045] If certain terms are used in the specification and claims to refer to specific components, those skilled in the art will understand that manufacturers may use different names to refer to the same component. This specification and claims do not distinguish components based on differences in name, but rather on differences in function. The term "comprising" as used throughout the specification and claims is an open-ended term and should be interpreted as "comprising but not limited to." "Approximately" means that within an acceptable margin of error, those skilled in the art can solve the technical problem and substantially achieve the technical effect within a certain margin of error.

[0046] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "horizontal", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0047] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0048] In recent years, the concept of acoustic metasurfaces has brought new avenues for the development of acoustic technology. A metasurface is an artificially designed subwavelength thickness structure. Through precise design of microstructural units and optimization of unit arrangement, the propagation direction and reflection / transmission characteristics of sound waves can be flexibly controlled. In the field of cross-medium acoustic wave transmission, metasurfaces can achieve impedance matching between different media within a finite thickness, improving the energy transmission efficiency of sound waves at the interface. They possess advantages such as portability, thinness, and flexible control. These superior properties make metasurfaces a promising candidate for application in complex environments such as water-air interfaces in cross-medium acoustic wave transmission. Therefore, the application of cross-water-air acoustic metasurface technology holds promise for overcoming the limitations of existing underwater sound sources.

[0049] The following is in conjunction with the appendix Figures 1-3 The present invention will be described in detail, but this is not intended to limit the invention.

[0050] like Figures 1-3 As shown, an underwater sound source based on a trans-water-air metasurface encapsulation consists of a waterproof cavity 4 containing a trans-water-air metasurface and an air speaker array. The front end of the waterproof cavity is designed with a metasurface of a specific shape and microstructure, and the interior is air 3. Together with the air speaker 1, it can efficiently emit sound waves in water 6. Figure 2 This is a structural schematic diagram of an underwater sound source element. Its shape can be a cuboid. A trans-water space metasurface shell 4-1 is formed by stretching the rectangular cross section to a certain thickness. Waterproof baffles 4-2 are added on both sides to form a waterproof cavity.

[0051] A method for fabricating an underwater sound source based on trans-water-space metasurface encapsulation, the method comprising the following steps:

[0052] (1) Determine the target operating frequency of the underwater sound source, which can be a single frequency point or a wide frequency range, such as 1715Hz. Make the shape of the underwater sound source unit cuboid. Its length in the x-axis direction can be selected as 130mm, its width in the z-axis direction can be selected as 44mm, and its y-axis direction can be stretched to a specified thickness as needed, which can be selected as 102mm. Each underwater sound source unit can be equipped with 3 air speakers 1 of about 1 inch each. The length, width, and thickness of each air speaker 1 are about 34mm, 34mm, and 17mm, respectively. Within the given external dimensions and target frequency range, use artificial intelligence optimization algorithm 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 outside the cavity, without considering the viscous loss of the waterproof cavity.

[0053] (2) One or more air loudspeakers 1 are encapsulated inside a waterproof cavity and assembled into an underwater sound source unit. The transmission performance of a single underwater sound source unit can be verified by calculating the normalized energy transmittance and sound field using finite element method.

[0054] (3) Based on the requirements for transmitting underwater sound beams, the number of underwater sound source element arrays can be adjusted accordingly. For example, to achieve the transmission of underwater cylindrical beams with wide-angle characteristics, 14 underwater sound element arrays can be used. To achieve the transmission of planar beams with high directivity, 40 underwater sound element arrays can be used. The initial transmission phase distribution of the underwater sound source element arrays can also be further set to achieve the directivity adjustment of the underwater sound source transmission beam.

[0055] To achieve bidirectional deflection plane beam transmission, 60 underwater elements can be arrayed, with elements 1-15 and 31-45 specifying the transmission of phase 0, and elements 16-30 and 46-60 specifying the transmission of phase π. To achieve unidirectional deflection plane beam transmission, 60 underwater elements can be arrayed, with elements 1-10 and 31-40 specifying the transmission of phase 0, elements 11-20 and 41-50 specifying the transmission of phase 2π / 3, and elements 21-30 and 51-60 specifying the transmission of phase 4π / 3.

[0056] To verify the underwater beam emission performance of the underwater sound source element array, at a set target frequency of 1715kHz, the sound signal is first emitted by the air loudspeaker 1 as an incident sound wave 2 in the air domain. After being incident on the trans-water-air metastructure surface at the front end of the waterproof cavity, the microstructure inside the underwater sound source element will generate a specific vibration mode, and finally radiate efficiently into the water 6, forming the expected specific directional underwater beam, so that the transmitted sound wave 5 in the water can be transmitted efficiently.

[0057] In addition, the relevant parameters of the geometric configuration can be adjusted based on human experience to design the structure of the trans-water-space metasurface. Other algorithms and reverse design strategies, such as topology optimization, can also be used to design the structure of the trans-water-space metasurface.

[0058] The following is in conjunction with the appendix Figures 4-23 The present invention will be further described in detail with reference to specific embodiments, but this is not intended to limit the present invention.

[0059] Example 1

[0060] In this first embodiment, as Figure 4 As shown, a topology optimization program was used to reverse engineer the trans-water-air metasurface at the front end of the waterproof cavity. The material parameter distribution of the 1320 pixels (44×30 pixels) at the front end was optimized, specifying the materials for the solid region 4-1-1 and the air region 4-1-2 of the trans-water-air metasurface unit. The solid material parameters were set to a 3D-printable resin material with a density of 1140 kg / m³. 3 The elastic modulus can be 3 GPa, the Poisson's ratio can be 0.41, and a viscosity loss factor of 0.05 is used when considering solid viscous losses. Furthermore, the density of air can be set to 1.21 kg / m³. 3 The speed of sound in air can be set to 343 m / s; the density of water can be set to 1000 kg / m³. 3 The speed of sound in water can be set to 1500 m / s.

[0061] In the optimization process of this embodiment, periodic boundary conditions are applied to the upper and lower sides of the underwater acoustic element, and a perfectly matched layer is set at the front and rear ends to absorb sound waves. The air speaker 1 inside the waterproof cavity is replaced by the background sound pressure field as the incident sound source and applied to the air waveguide region 4-1-3 inside the shell. The air speaker region 4-1-4 inside the shell is used as a blank area for placing the air speaker 1. The solid frame 4-1-5 outside the shell is used for waterproofing.

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

[0063] Figure 7The acoustic field transmission effect of the trans-water-air metasurface is shown without considering the viscosity of the solid. It can be seen that, thanks to the significant vibration mode of the trans-water-air metasurface, the sound wave is transmitted efficiently from the air domain inside the waterproof cavity to the water area at the external front.

[0064] The corresponding result when considering the viscosity of solids is as follows: Figure 8 As shown, the trans-water-air metasurface still maintains the corresponding vibration mode, and the sound source has good emission performance.

[0065] in addition, Figure 9 and Figure 10 The normalized ratios of the transmitted, reflected, and incident energies of the sound field are presented as a function of frequency, with and without considering solid viscous losses. In both figures, the normalized energy of the reflected wave at the incident end at a frequency of 1315 Hz is close to 1.

[0066] at last, Figure 11 The variation of front-end transmission energy enhancement performance of the underwater acoustic source based on trans-water-air metasurface encapsulation with frequency compared to the form without the metasurface is presented. It can be seen that within the frequency range of 1455Hz-1900Hz, the front-end transmitted wave energy enhancement ratio reaches 40dB (100 times), while the energy of the incident reflected wave and the rear transmitted wave remains low, demonstrating good underwater acoustic wave transmission performance over a certain wide frequency range. Even after considering solid viscous losses, good front-end transmission performance is maintained, indicating the high efficiency of the underwater acoustic source provided by this invention.

[0067] Example 2

[0068] In this second embodiment, as Figure 12 As shown, in Example 2, other shapes of trans-water-space metasurfaces were designed, while the other corresponding geometric configurations and material parameter settings were the same as in Example 1.

[0069] Figure 13 The acoustic field transmission effect of the trans-water-air metasurface is given without considering the viscosity of the solid. It can be seen that, thanks to the significant vibration mode of the trans-water-air metasurface, the sound wave is efficiently transmitted from the air domain inside the waterproof cavity 4 to the water area at the external front.

[0070] The result when considering the viscosity of solids is as follows: Figure 14 As shown, the trans-water-air metasurface still maintains the corresponding vibration mode, and the sound source has good emission performance.

[0071] in addition, Figure 15 and Figure 16 The normalized ratios of the transmitted, reflected, and incident energies of the sound field are presented as a function of frequency, with and without considering solid viscous losses. In both figures, the normalized energy of the reflected wave at the incident end at a frequency of 1315 Hz is close to 1.

[0072] at last, Figure 17 The variation of front-end transmission energy enhancement performance of an underwater acoustic source based on a trans-water-air metasurface encapsulation with frequency compared to the absence of a metasurface is presented. It can be seen that within the frequency range of 1465Hz-1860Hz, the energy enhancement ratio of the front-end transmitted wave reaches 40dB (100 times), while the energy of the incident reflected wave and the rear transmitted wave remains low, demonstrating good underwater acoustic wave transmission performance over a certain wide frequency range. Even after considering solid viscous losses, good front-end transmission performance is maintained, indicating that the underwater acoustic source design and fabrication method provided by this invention has universality.

[0073] Example 3

[0074] In this third embodiment, the directivity of the underwater sound source can be adjusted by changing the number of underwater sound source element arrays according to the requirements for transmitting underwater sound beams.

[0075] Figure 18 A schematic diagram of a cylindrical beam underwater acoustic source with wide-angle emission characteristics is presented. The effect of solid viscous loss is not considered. The underwater acoustic source element structure is selected from the result of Example 1, and the array size of the underwater acoustic source elements is 14. Figure 18 As can be seen, the sound waves emitted into the water from the front end have a good cylindrical wavefront and a wide angle, while effectively suppressing the emission from the rear end. Furthermore, Figure 19 The results show the effect after considering solid viscous loss, demonstrating that good emission performance is still maintained even after considering solid viscous loss.

[0076] Figure 20 A diagram illustrating the effect of emitting a highly directional planar wavefront underwater acoustic source is presented. The influence of solid viscous loss is not considered, and the basic structure of the underwater acoustic source remains the same as in Example 1, but the array size of the underwater acoustic source elements is 40. It can be seen that the acoustic wave emitted into the water from the front end has a good planar wavefront and good vertical directivity, while effectively suppressing the emission from the rear end. Furthermore, Figure 21 The results show the effect after considering solid viscous loss, demonstrating that good emission performance is still maintained even after considering solid viscous loss.

[0077] Example 4

[0078] In this fourth embodiment, the directivity of the underwater sound source can be adjusted by further setting the initial transmission phase distribution of the underwater sound source element array according to the requirements for transmitting the underwater sound beam.

[0079] Figure 22A diagram illustrating the effect of transmitting a bidirectional deflecting plane beam underwater acoustic source is presented. The underwater acoustic source element structure uses the results from Example 1, with an array of 60 elements. Elements 1-15 and 31-45 are designated to transmit the 0 phase, while elements 16-30 and 46-60 are designated to transmit the π phase. It can be seen that, regardless of whether solid viscous loss is considered, the sound waves emitted into the water from the front end are split into two beams, distributed along two symmetrical directions, while effectively suppressing the emission from the rear end, achieving the desired effect.

[0080] Figure 23 The effect of transmitting a unidirectional deflecting planar wave underwater acoustic source is shown in the diagram. The underwater acoustic source element structure is based on the results from Example 1, with an array of 60 elements. Elements 1-10 and 31-40 are designated to transmit phase 0, elements 11-20 and 41-50 to transmit phase 2π / 3, and elements 21-30 and 51-60 to transmit phase 4π / 3. It can be seen that, regardless of whether solid viscous loss is considered, the sound wave emitted into the water at the front end deflects downwards and to the left, transmitting in a single direction, while effectively suppressing the emission at the rear end, exhibiting good directivity and achieving the desired effect.

[0081] As can be seen, the underwater sound source of the present invention consists of a waterproof cavity with a trans-water-space metasurface and an array of air speakers. The front end of the waterproof cavity is designed with a metasurface of a specific shape and microstructure, which, together with the air speakers, can efficiently emit sound waves underwater. Utilizing the sound energy transmission enhancement characteristics of the metasurface at the trans-water-space interface, and encapsulating the lightweight and controllable air speakers inside a waterproof solid frame, it ultimately serves as a sound source for emitting underwater acoustic signals.

[0082] The underwater acoustic source designed in this invention possesses certain broadband characteristics and adjustable directivity. By adjusting the number of metasurface arrays in the cavity, cylindrical beams with wide-angle characteristics and planar beams with high directivity can be generated. By adjusting the emission phase of the air loudspeaker, the deflection direction of the emitted sound beam in the water can be controlled, such as achieving flexible emission of bidirectional or unidirectional underwater acoustic beams.

[0083] In summary, the underwater sound source design provided by this invention is lightweight, flexible, highly controllable, and easy to assemble. It can replace a single cylindrical sound source or be assembled into a large-area sound array, significantly reducing the cost of underwater sound sources and simplifying the design and manufacturing process. It has significant application value in engineering fields such as underwater acoustic communication, underwater navigation and positioning, underwater robot control, marine mineral resource exploration, environmental monitoring, military reconnaissance, fault monitoring, and fisheries resource management.

[0084] Based on the disclosure and teachings of the foregoing specification, those skilled in the art can make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments described above, and any obvious improvements, substitutions, or modifications made by those skilled in the art based on the present invention are within the scope of protection of the present invention. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on the present invention.

Claims

1. A method for fabricating an underwater sound source based on trans-water-space metasurface encapsulation, characterized in that, Includes the following steps: Step 1: Determine the target frequency range of the underwater sound source and the external dimensions of the underwater sound source element. Based on the target frequency range and the external dimensions, optimize the waterproof cavity containing a trans-water space metasurface. The optimization process uses a topology optimization program to reverse design the trans-water space metasurface at the front end of the waterproof cavity. The optimization index is that the transmittance of the sound waves in the air domain inside the cavity is not less than 95% when they are emitted to the water outside the cavity. The material parameter distribution of multiple pixels on the trans-water space metasurface at the front end is optimized. At the same time, periodic boundary conditions are applied to the upper and lower sides of the underwater sound source element. Step 2: Encapsulate one or more air loudspeakers inside the waterproof cavity to assemble an underwater sound source unit; Step 3: Based on the requirements for transmitting underwater sound beams, a certain number of underwater sound source element arrays are prepared, and the initial transmission phase distribution of the underwater sound source element arrays is set. The directivity of the underwater sound source transmission 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-space metasurface encapsulation as described in claim 1, characterized in that, Step one further includes: setting the shape of the underwater sound source element as a cuboid, and defining waterproof baffles on the opposite sides of the waterproof cavity.

3. The method for fabricating an underwater sound source based on trans-water-space metasurface encapsulation as described in claim 1, characterized in that, Step one also includes: using 3D printing technology to create a waterproof cavity containing a trans-water-space metasurface.

4. The method for preparing an underwater sound source based on trans-water-space metasurface encapsulation as described in claim 1, characterized in that, Step two also includes: verifying the transmission performance of a single underwater sound source element, while taking into account the influence of viscous loss of solid materials.

5. The method for fabricating an underwater sound source based on trans-water-space metasurface encapsulation as described in claim 1, characterized in that, Step two further includes: the air loudspeaker is selected based on a preset power for transmitting the beam underwater.

6. The method for preparing an underwater sound source based on trans-water-space metasurface encapsulation as described in claim 1, characterized in that, Step three further includes: the initial transmission phase distribution adopts continuous or discrete phase points, the initial transmission phase distribution is determined according to the transmission beam mode and wave field control theory, and the underwater sound source optimization process is carried out by checking the underwater beam transmission performance of the underwater sound source element array until the underwater sound source element can generate a preset vibration mode.

7. An underwater sound source based on a trans-water-space metasurface encapsulation, prepared by the method for preparing an underwater sound source as described in any one of claims 1 to 6, characterized in that, include: Several arrays of underwater sound source elements are arranged. Each underwater sound source element includes a waterproof cavity. The waterproof cavity has a trans-water-air metasurface and an air loudspeaker arranged on opposite sides. The underwater sound source element can generate a preset vibration mode in the water environment and then radiate the sound signal into the water.

8. The underwater sound source based on trans-water-space metasurface encapsulation as described in claim 7, characterized in that: When the number of underwater sound source elements in the array is i, the underwater sound source emits a cylindrical beam; when the number of underwater sound source elements in the array is j, the underwater sound source emits a directional planar beam. Both i and j are constants, and i... <j。

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