Omnidirectional scattering sound absorption covering layer, manufacturing method and application

Abstract

The invention discloses an underwater sound stealth covering layer structure which comprises a base plate, a unit A and a unit B, wherein the unit A and the unit B are fixedly attached to the base plate. The unit A and the unit B are metasurface structure units with different structures, the projection sizes of the unit A and the unit B on the substrate are the same, and the unit A and the unit B are arranged on the substrate in a matrix manner, so that an acoustic wave diffuse reflection effect is generated on the whole surface of the covering layer; the unit A is provided with a groove A in the direction back to the substrate, and the top of the groove A is covered with a thin film. The invention further discloses a manufacturing method of the underwater sound stealth covering layer structure, the unit B is made of metal materials, the unit A is manufactured through a 3D printing method, 0 / 1 coding is carried out on the metasurface through different small units, the functions of broadband underwater sound stealth and the like can be achieved, and the underwater sound stealth covering layer structure can be widely popularized in practical application.

Description

Technical Field

[0001] The present invention relates to the technical field of metasurface structures, and particularly to an omnidirectional scattering sound-absorbing covering layer, a manufacturing method and uses thereof. Background Art

[0002] Currently, a metasurface is a planar acoustic metamaterial with a subwavelength thickness. By arranging its microstructural units, the acoustic metasurface can freely customize the sound field and achieve various physical characteristics, such as anomalous reflection or refraction, sound absorption, super-sparse reflection, invisibility, etc. The acoustic metasurface has a device thickness of deep subwavelength and extraordinary acoustic wave manipulation performance, so it has great application prospects in the fields of medical imaging, acoustic communication, particle manipulation, etc.

[0003] There are still great limitations in using acoustic metamaterials to achieve acoustic negative refraction and subwavelength imaging. First, research on acoustic negative refraction mainly focuses on acoustic waves in air, and there are few reports on negative refraction of underwater sound. Second, some solutions, such as using porous soft silicon particles immersed in water, can form underwater acoustic negative refraction, but the damping's attenuation of resonance makes it difficult to truly be used for acoustic wave focusing and subwavelength imaging. Therefore, the realization and application of underwater acoustic negative refraction remain a difficult problem. Summary of the Invention

[0004] The present invention provides an omnidirectional scattering sound-absorbing covering layer, a manufacturing method and uses thereof to solve the technical problems existing in the known technology.

[0005] The technical solution adopted by the present invention to solve the technical problems existing in the known technology is:

[0006] An omnidirectional scattering sound-absorbing covering layer includes a substrate, unit A and unit B fixedly attached to the substrate; unit A and unit B are metasurface structural units with different structures, their projected sizes on the substrate are the same, and they are arranged in a matrix on the substrate to produce a sound wave diffuse reflection effect on the overall surface of the covering layer; a groove A is opened in the direction away from the substrate of unit A, and a thin film is covered on the top of the groove A.

[0007] Further, the phase difference of the sound wave reflection between unit A and unit B is 175 - 180 degrees; the surface of unit B facing away from the substrate is a plane or a protrusion.

[0008] Further, the cross-section of the groove A is square, and the longitudinal section of the groove A is rectangular or triangular or trapezoidal or arc-shaped.

[0009] Further, several square modules are formed by unit A and unit B alone or in combination; the substrate is divided into several squares, and each square module is fixed in one square.

[0010] Further, unit A and / or unit B are arranged in a matrix of M rows × M columns to form a square module, where M ≥ 10.

[0011] Further, let λ be the wavelength of sound waves. The projected contour shapes of unit A and unit B on the substrate are squares with side length equal to a, where a = λ / M.

[0012] Further, the phase difference of the sound wave reflection between unit A and unit B is 170 - 180 degrees; several square modules are formed by mixing unit A and unit B at intervals.

[0013] The present invention also provides a method for manufacturing the above omnidirectional scattering sound-absorbing covering layer. The manufacturing materials of unit A and unit B are hard plastics or metals; the manufacturing material of the thin film is an organic polymer material; unit A is manufactured using 3D printing method, and a thin film is covered on the top of groove A; let the phase encoding of unit A be 1, and the phase encoding of unit B be 0. Unit A and unit B are arranged and fixed on the substrate according to the set phase encoding sequence.

[0014] Further, several square modules are formed by arranging unit A and unit B alone or in combination in a matrix of M rows and M columns; the substrate is divided into several squares. Let the surface of the square module in contact with the substrate be the bottom surface. The size of each square is the same as the bottom surface size of the square module. Card slots are provided on the substrate surface corresponding to the squares; the bottom of the square module is provided with protrusions that cooperate with the card slots. Let the phase encoding of the square module composed of unit A be 1, and the phase encoding of the square module composed of unit B be 0. The square modules composed of unit A and the square modules composed of unit B are arranged according to the set phase encoding sequence, and the square modules are inserted into the card slots and fixed.

[0015] The present invention also provides a use of the above omnidirectional scattering sound-absorbing covering layer, which is used for installing on underwater stealth devices.

[0016] The advantages and positive effects of the present invention are as follows: For the omnidirectional scattering sound-absorbing covering layer of the present invention, unit A and unit B, as two small units with different structures, are arranged in a matrix on the substrate. Through the adjustment of the arrangement order, the overall structure interferes with the sound wave reflection to form diffuse reflection; a groove A is opened on the back of unit A away from the substrate, and a thin film is covered on the top of groove A; in the thin film material, sound waves can cause the vibration of material fibers, which is then converted into heat energy and absorbed. Therefore, the thin film has a certain low-frequency sound absorption effect.

[0017] The phase of unit A can be encoded as 1, the phase of unit B can be encoded as 0, and unit A and unit B are arranged and fixedly connected to the substrate according to a set phase encoding sequence; or the phase of the square module composed of unit A can be encoded as 1, the phase of the square module composed of unit B can be encoded as 0, and the square module composed of unit A and the square module composed of unit B are arranged according to a set phase encoding sequence. By adjusting the arrangement of the phase encoding sequence and the incident angle of the sound wave, the sound wave diffuse reflection effect can be realized to achieve the sound stealth function.

[0018] The metal plate made by processes such as cutting and bending, the solid shell with grooves made by 3D printing method, and the polyethylene film made by calendering method have high production precision and low cost. By encoding the metasurface with 0 / 1 by different small units, the invention can realize functions such as broadband underwater sound stealth, and can be widely promoted in practical applications. Brief Description of the Drawings

[0019] Figure 1 It is a schematic diagram of unit B in an omnidirectional scattering sound-absorbing covering layer of the present invention.

[0020] Figure 2 It is a schematic diagram of unit A in an omnidirectional scattering sound-absorbing covering layer of the present invention.

[0021] Figure 3 It is a schematic structural diagram of unit A in an omnidirectional scattering sound-absorbing covering layer of the present invention.

[0022] Figure 4 It is a schematic cross-sectional view of the film covered by unit A in an omnidirectional scattering sound-absorbing covering layer of the present invention.

[0023] Figure 5 It is a schematic structural diagram of the square module composed of unit B in an omnidirectional scattering sound-absorbing covering layer of the present invention.

[0024] Figure 6 It is a schematic structural diagram of the square module composed of unit A in an omnidirectional scattering sound-absorbing covering layer of the present invention.

[0025] Figure 7 It is a schematic layout diagram of the square modules respectively composed of unit A and unit B in the omnidirectional scattering sound-absorbing covering layer of the preferred embodiment of the present invention.

[0026] Figure 8 It is the underwater sound stealth effect diagram when the incident sound wave frequency is 15 kHz and the incident angle is 0 degree by using the preferred embodiment of the present invention.

[0027] Figure 9 It is the underwater sound stealth effect diagram when the incident wave sound wave frequency is 25 kHz and the incident angle is 0 degree by using the preferred embodiment of the present invention.

[0028] Figure 10 The underwater acoustic stealth effect diagram when the incident sound wave frequency is 15 kHz and the incident angle is 30 degrees by adopting the preferred embodiment of the present invention.

[0029] Figure 11 The underwater acoustic stealth effect diagram when the incident sound wave frequency is 25 kHz and the incident angle is 30 degrees by adopting the preferred embodiment of the present invention.

[0030] In the figure: 1. Unit B; 2. Unit A; 3. Groove A; 4. Thin film; 5. Square module composed of unit B; 6. Square module composed of unit A; 7. Substrate.

[0031] The projections of unit A and unit B on the substrate are squares, a is the side length of the square; the bottom surface of groove A is a square, b is the side length of the square; c is the thickness of the thin film, d is the depth of groove A, e is the thickness of the groove A wall, and f is the distance between the bottom surface of groove A and the bottom surface of unit A. Specific embodiments

[0032] The present invention will be described in detail below with reference to the drawings and in conjunction with embodiments. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0033] In the description of the present invention, the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention rather than requiring the present invention to be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of the present invention. The terms "connected" and "coupled" used in the present invention should be understood in a broad sense. For example, it can be a fixed connection or a detachable connection; it can be directly connected or indirectly connected through an intermediate component; it can also be an electrical connection or a signal transmission; for those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0034] Please refer to Figures 1 to 11 , an omnidirectional scattering sound absorption coating, including a substrate 7, a unit A 2 and a unit B 1 fixedly attached to the substrate 7; the unit A 2 and the unit B 1 are two different metasurface structure units, and their projection sizes on the substrate 7 are the same. They are arranged in a matrix on the substrate 7 to cause a sound wave diffuse reflection effect on the overall surface of the coating; a groove A 3 is opened in the direction of the unit A 2 away from the substrate 7, and a thin film 4 is covered on the top of the groove A 3.

[0035] In the material of the thin film 4, sound waves can cause the vibration of the material fibers, which are then converted into heat energy and absorbed. Therefore, the thin film 4 has a certain low-frequency sound absorption effect.

[0036] The sound absorption mechanism of the thin film 4 structure is mainly the internal damping loss when the thin film 4 vibrates as a whole, so it can be approximately regarded as a simple mass-spring system. When sound waves encounter the thin film 4 type acoustic metamaterial, part of the sound waves will be reflected back, and the other part of the sound waves will be absorbed or continue to penetrate the material, but their intensity will be attenuated to a certain extent.

[0037] The low-frequency sound absorption performance of the thin film 4 is mainly related to the thickness, density and material selection of the film. A thicker thin film 4 can better absorb low-frequency sound waves, while a lighter film has better high-frequency sound absorption performance. At the same time, different materials will also affect the low-frequency sound absorption performance of the thin film 4.

[0038] When a plane wave is incident on the omnidirectional scattering sound absorption covering layer of the present invention vertically or at a certain deflection angle, the covering layer structure will reflect the sound waves and diverge them in different directions, and the reflection angle is axisymmetric with the incident angle about the normal line. A groove A3 is opened in the unit A2 in the direction away from the substrate 7, and the thin film 4 is covered on the top of the groove A3. When a plane wave is incident on the surface of the thin film 4 in the groove A3, when the sound waves encounter the thin film 4 type acoustic metamaterial, part of the sound waves will be reflected back, and the other part of the sound waves will be absorbed or continue to penetrate the thin film 4, but their intensity will be attenuated to a certain extent. The sound waves transmitted to the inner wall and the bottom of the groove A3 are reflected to the thin film 4 and continue to be absorbed or continue to penetrate the thin film 4. The sound waves penetrating the thin film 4 are further attenuated, and the angle of the sound waves exiting the thin film 4 is inconsistent with the angles of the other sound waves reflected from the covering layer, thus causing diffuse reflection.

[0039] The covering layer structure adjusts the reflection direction of the sound waves by adjusting the matrix arrangement order of the unit A2 and the unit B1 on the substrate 7. After the two are arranged, the overall surface structure of the covering layer interferes with the sound wave reflection to cancel each other out, causing a broadband sound wave diffuse reflection effect, so as to achieve the function of underwater acoustic stealth.

[0040] By arranging the unit A2 and the unit B1 with two different structures in different arrangement forms, different forms of acoustic metasurface structures can be made to achieve adjustable broadband reflection type wavefront control. The coding arrangement rule determines the form of the acoustic metasurface structure.

[0041] Preferably, the phase difference between the unit A2 and the unit B1 in the reflection of the sound waves can be 175-180 degrees; the surface of the unit B1 in the direction away from the substrate 7 can be a plane. The surface of the unit B1 in the direction away from the substrate 7 can be a rough surface with multiple protrusions.

[0042] A rough surface refers to a surface that is uneven, has obvious bumps and textures. Such surfaces are very common in daily life, such as the surfaces of natural materials such as unpolished wood and stone, or the surfaces of metals treated by specific processes.

[0043] A rough surface will cause the incident sound waves to be reflected at various angles, thus dispersing the reflected energy in different directions, resulting in a diffuse reflection effect.

[0044] Unit A2 and unit B1, when arranged, can make the overall structure have a sound wave reflection phase difference close to 180 degrees in a wide frequency range.

[0045] Preferably, the cross-section of the groove A3 can be square, and the longitudinal section of the groove A3 can be rectangular or trapezoidal or arc-shaped.

[0046] Preferably, the cross-section of the groove A3 can be circular, and the longitudinal section of the groove A3 can be square or arc-shaped.

[0047] The projections of unit A2 and unit B1 on the substrate 7 are square, and a is the side length of this square; a can be 10 - 12 mm. The bottom surface of the groove A3 is square, and b is the side length of this square, b can be 7 - 10 mm. c is the thickness of the thin film 4, c can be 0.25 - 0.35 mm. The height of unit A2 and unit B1 is a + c.

[0048] Please refer to Figure 4 , d is the depth of the groove A3, d can be 8 - 10 mm; e is the wall thickness of the groove A3, e = 1 mm. f is the distance between the bottom surface of the groove A3 and the bottom surface of unit A2, f = 1 mm.

[0049] Unit B1 and unit A2, as a metasurface structure unit, when adopting the following dimensions: the side length of the square bottom surface of unit B1 and unit A2 is 10 mm, the height of unit B1 is 10.35 mm, the height of unit A2 is 10 mm, the side length of the square bottom surface of the groove A3 is 8 mm, the side wall thickness is 9 mm, the bottom of the groove A3 is 1 mm away from the bottom of unit A2, the surface of the thin film 4 on the top of the groove A3 is square, and its surface side length is 10 mm, and the thickness is 0.35 mm. The unit B1 without a groove and the unit A2 with a groove have a phase difference close to 180 degrees when reflecting sound waves. And it remains stable in the wide frequency range of 10 kHz - 12 kHz and 13 kHz - 25 kHz.

[0050] Preferably, several square modules can be composed of unit A2 and unit B1 alone or in combination; the substrate 7 can be divided into several squares, and each square module is fixed in one square.

[0051] The square module composed of unit A2 alone is called the super unit A6; the square module composed of unit B1 alone is called the super unit B5.

[0052] Preferably, unit A2 and / or unit B1 can form a square module in a matrix arrangement of M rows × M columns, where M ≥ 10. The super unit A6 and the super unit B5 are fixed to the metal base plate according to a specific coding sequence to form a metasurface structure.

[0053] Preferably, the square module can be composed of unit A2 and unit B1 alone, and the square modules formed by unit A2 and the square modules formed by unit B1 can be arranged alternately.

[0054] Unit A2 and unit B1 are correspondingly combined into the super unit A6 and the super unit B5 in the same matrix arrangement. A number of unit A2s are combined into the super unit A6; a number of unit B1s are combined into the super unit B5. The two types of super units are then arranged according to a specific coding sequence.

[0055] In the super unit A6 and the super unit B5, both unit B1 and unit A2 are arranged in a matrix of M rows and M columns. M ≥ 10, for example, M can preferably be 10 - 15.

[0056] Preferably, let λ be the sound wave wavelength, and the projected contour shape of unit A2 and unit B1 on the substrate 7 can be a square with a side length equal to a, where a = λ / M.

[0057] In order to achieve the best underwater acoustic stealth effect and be efficient for different broadband ranges. The side length a of the square bottom surface of unit B1 and unit A2 can satisfy M × a = λ (λ is the wavelength of the sound wave in water). The metasurface structure after encoding arrangement can achieve various broadband acoustic wave regulation capabilities. For example, the sizes of unit B1 and unit A2 mentioned above are suitable for the broadband ranges of 10 kHz - 12 kHz and 13 kHz - 25 kHz.

[0058] Preferably, the phase difference between the sound wave reflections of unit A2 and unit B1 is 170 - 180 degrees; several square modules can be formed by mixing unit A2 and unit B1 at intervals.

[0059] Preferably, the production material of unit A2 can be a rigid plastic material; the production material of unit B1 can be a metal material; the production material of the thin film 4 can be polyethylene or polyimide. The thin film 4 can be made by the calendering method.

[0060] Unit A2, unit B1, super unit A6, and super unit B5 can all be made by 3D printing.

[0061] The 3D printing materials are metal powder, alloy powder, metal matrix composite material, or hard plastic powder.

[0062] The metal powder materials include metal powders such as silver, copper, aluminum, and titanium. These powders can be prepared by methods such as fused deposition, electron beam melting, and electron beam melting injection. During the 3D printing process, these metal powders can be melted and deposited into shape on the corresponding molds through the scanning of a laser beam, thereby preparing metal parts with certain shapes and sizes.

[0063] Metal matrix composites are composite materials composed of metal powders and fiber materials, and are usually prepared by methods such as powder sintering and fused deposition. These materials have characteristics such as high strength, high toughness, and high wear resistance, and various parts with different shapes and sizes can be prepared through different forming methods.

[0064] There are many types of 3D printing alloy powder materials, including stainless steel, aluminum alloy, cobalt-chromium alloy, copper alloy, titanium alloy, and nickel alloy, etc. These powder materials need to meet certain requirements, such as fine particle size, narrow particle size distribution, high sphericity, good fluidity, and high apparent density, etc., to ensure excellent performance of the printed products. The characteristics of different alloy powders determine their respective suitable application fields. For example, stainless steel powder has high cost performance and good corrosion resistance, and is suitable for the production of complex industrial parts; aluminum alloy powder has the characteristics of light weight and high strength, and is suitable for applications with thin walls and complex geometries; titanium alloy powder is widely used in the aerospace field, which can help optimize product design and achieve lightweight production.

[0065] One of the most commonly used materials in 3D printing is plastic materials. Plastic materials are usually used in the form of powders or liquids, and then melted and solidified to produce the required shapes. Common plastic materials include polyamide (PA), polylactic acid (PLA), polycarbonate (PC), polyvinyl alcohol (PVA), etc. These materials have the advantages of being light, inexpensive, and easy to process, and are widely used in 3D printing. Plastic materials are widely used in the manufacture of models, prototypes, parts, etc.

[0066] Unit B1 can be made of hard metal materials, unit A2 can be made of hard organic materials or hard metals, and the film 4 can be made of organic polymer materials. Hard metal materials include hard alloys such as alloy steel and aluminum alloy, hard organic materials can include epoxy resin, etc., and organic polymer materials can include polyethylene, polyimide, etc.

[0067] The present invention also provides a method for manufacturing the above omnidirectional scattering sound-absorbing covering layer. The manufacturing materials of unit A2 and unit B1 are hard plastics or metals; the manufacturing material of the thin film 4 is an organic polymer material; the 3D printing method is used to manufacture unit A2 and super unit A6, and the thin film 4 is covered on the top of the groove A3; the phase encoding of unit A2 is set to 1, the phase encoding of unit B1 is set to 0, and unit A2 and unit B1 are arranged and fixedly connected to the substrate 7 according to the set phase encoding sequence. Unit A2 and unit B1 can be fixedly connected to the substrate 7 with an adhesive. Unit B1 and super unit B5 can be made by processes such as cutting and casting, the thin film 4 is made by a calendering method, and the thin film 4 is fixedly pasted on the upper edge of the groove A3 with a waterproof adhesive.

[0068] Preferably, several square modules can be formed by arranging unit A2 and unit B1 alone or in combination in a matrix arrangement of M rows and M columns; the substrate 7 can be divided into several squares, the surface of the square module in contact with the substrate 7 is set as the bottom surface, the size of each square is the same as the bottom surface size of the square module, and card slots are arranged on the surface of the substrate 7 corresponding to the squares; a protrusion matching the card slot is arranged at the bottom of the square module. The phase encoding of the square module composed of unit A2 can be set to 1, the phase encoding of the square module composed of unit B1 can be set to 0, and the square module composed of unit A2 and the square module composed of unit B1 can be arranged according to the set phase encoding sequence, and the square module is embedded in the card slot and fixed.

[0069] For example, the substrate 7 can be divided into 10 rows × 5 columns of squares, and a square module composed of unit A2 and unit B1 arranged at intervals and mixed in a matrix arrangement of M rows and M columns is fixed in 5 rows × 5 columns of squares; the square modules composed of unit A2 and the square modules composed of unit B1 in the other 5 rows × 5 columns are arranged according to the following encoding sequence: "01010", "10101", "01010", "10101", "01010".

[0070] The card slot can be a dovetail groove, a dovetail matching the dovetail groove is arranged at the bottom of the square module, the square module is embedded in the dovetail groove, and retaining bars for preventing the square module from sliding out of the dovetail groove are arranged at both ends of the dovetail groove, and the retaining bars are fixed to the substrate 7 with screws.

[0071] The present invention also provides a use of the above omnidirectional scattering sound-absorbing covering layer, which is used for installing on an underwater stealth device. The phase encoding of unit A2 with the groove A3 is set to 1, and the phase encoding of unit B1 without the groove A3 is set to 0; the underwater acoustic stealth function can be realized by adjusting the arrangement of the phase encoding sequence.

[0072] The following further illustrates the structure and working principle of the present invention with several preferred embodiments of the present invention:

[0073] An omnidirectional scattering sound-absorbing covering layer, comprising a substrate 7, a unit A2 and a unit B1 fixedly attached to the substrate 7; the unit A2 and the unit B1 are both metasurface structure units with different structures, and their projected sizes on the substrate 7 are the same. They are arranged in a matrix on the substrate 7, and their combined arrangement makes the overall surface of the covering layer form an acoustic wave diffuse reflection effect; a groove A3 is opened in the direction of the unit A2 away from the substrate 7, and a thin film 4 is covered on the top of the groove A3.

[0074] Please refer to Figures 1 to 3 , the projections of the unit A2 and the unit B1 on the substrate 7 are squares, and a is the side length of the square; a = 10 mm. The bottom surface of the groove A3 is a square, and b is the side length of the square, b = 8 mm. c is the thickness of the thin film 4, c = 0.35 mm. The height of the unit A2 and the unit B1 is a + c.

[0075] Please refer to Figure 4 , d is the depth of the groove A3, e is the wall thickness of the groove A3, e = 1 mm. f is the distance between the bottom surface of the groove A3 and the bottom surface of the unit A2, f = 1 mm.

[0076] d and a maintain a numerical relationship of a = d + f.

[0077] Please refer to Figure 5 , the unit B1 is arranged in a matrix of M rows × M columns to form a square module, M = 10.

[0078] Please refer to Figure 6 , the unit A2 is arranged in a matrix of M rows × M columns to form a square module, M = 10.

[0079] Please refer to Figure 7 , several square modules are formed by the unit A2 and the unit B1 alone or in combination; the substrate 7 is divided into several squares, and each square module is fixed in a square.

[0080] An omnidirectional scattering sound-absorbing covering layer formed by arranging the square modules composed of the unit B1 and the square modules composed of the unit A2 in a coding sequence.

[0081] The present invention can achieve broadband coding acoustic regulation, such as broadband acoustic wave diffuse reflection effect, and its working principle is as follows:

[0082] When a plane wave is incident on the omnidirectional scattering sound-absorbing covering layer of the present invention vertically or at a certain deflection angle, the covering layer structure can diverge the reflected acoustic wave in different directions, and the reflection angle is axisymmetric with the incident angle about the normal line. The covering layer structure realizes the function of underwater acoustic stealth by regulating the behavior of the reflected acoustic wave to make it have a broadband acoustic wave diffuse reflection effect.

[0083] If the cells A2 are arranged in a 10×10 matrix to form super cells A6, and if the cells B1 are arranged in a 10×10 matrix to form super cells B5, the super cells A6 are recorded as code 1, and the super cells B5 are recorded as code 0, such as Figure 7 As shown, the arrangement order of super unit A6 and super unit B5 in the first row corresponds to the periodic coding sequence: "00010010". When a series of plane waves of different frequencies are incident on the cover structure at an incident angle of zero (i.e., vertical scanning) or other angles, the reflected waves will be dispersed in different directions, thereby reducing the intensity of the reflected sound waves.

[0084] The structure of the embodiment of the present invention can be obtained by a relatively simple mechanical processing method such as 3D printing, and the processing is simple.

[0085] Figure 7 It is a schematic diagram of the arrangement of square modules in an omnidirectional scattering sound-absorbing covering layer of the present invention.

[0086] Figures 8 to 11 This is a diagram of the underwater acoustic stealth effect provided by an embodiment of the present invention. Figure 8 The frequency of the incident sound wave is 15kHz, and the angle of incidence is zero degrees; Figure 9 The frequency of the incident sound wave is 25kHz, and the angle of incidence is zero degrees; Figure 10 The frequency of the incident sound wave is 15kHz, and the incident angle is 30 degrees; Figure 11 The incident sound wave frequency is 25kHz and the incident angle is 35 degrees. Different incident frequencies and different incident angles will produce different underwater acoustic stealth effects.

[0087] The embodiments described above are only used to illustrate the technical ideas and features of the present invention, and their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. The patent scope of the present invention cannot be limited only by this embodiment, that is, any equivalent changes or modifications made to the spirit disclosed by the present invention still fall within the patent scope of the present invention.

Claims

1. An omnidirectional scattering sound absorbing covering layer, characterized in that: It includes a substrate, a unit A and a unit B fixed on the substrate; the unit A and the unit B are super surface structural units with different structures, the projection sizes of the two on the substrate are the same, and the two are arranged in a matrix on the substrate, so that the overall surface of the covering layer produces a diffuse reflection effect of sound waves; the unit A has a groove A facing away from the substrate, and a thin film is covered on the top of the groove A.

2. The omnidirectional scattering sound absorbing covering layer according to claim 1, characterized in that: The phase difference between unit A and unit B in terms of sound wave reflection is 175-180 degrees; the surface of unit B facing away from the substrate is a plane or a protrusion.

3. The omnidirectional scattering sound absorbing covering layer according to claim 1, characterized in that: The cross section of the groove A is square, and the longitudinal section of the groove A is rectangular, triangular, trapezoidal or arc-shaped.

4. The omnidirectional scattering sound absorbing covering layer according to claim 1, characterized in that: A plurality of square modules are formed by unit A and unit B alone or in combination; the substrate is divided into a plurality of square grids, and each square module is fixed in a square grid.

5. The omnidirectional scattering sound absorbing covering layer according to claim 4, characterized in that: The units A and / or the units B are arranged in a matrix of M rows×M columns to form a square module, where M≥10.

6. The omnidirectional scattering sound absorbing covering layer according to claim 5, characterized in that: Assuming λ is the wavelength of the sound wave, the projection outline of unit A and unit B on the substrate is a square with a side length equal to a, where a=λ / M.

7. The omnidirectional scattering sound absorbing covering layer according to claim 4, characterized in that: The phase difference between unit A and unit B in terms of sound wave reflection is 170 to 180 degrees; a number of square modules are formed by mixing units A and B at intervals.

8. A method for manufacturing the omnidirectional scattering sound absorbing covering layer according to claim 1, characterized in that: The materials used to make unit A and unit B are hard plastic or metal; the materials used to make the film are organic polymer materials; unit A is made using a 3D printing method, and the film is covered on the top of groove A; the phase coding of unit A is set to 1, and the phase coding of unit B is set to 0, and units A and B are arranged according to the set phase coding sequence and fixed to the substrate.

9. The method for manufacturing an omnidirectional scattering sound absorbing covering layer according to claim 8, characterized in that: A plurality of square modules are formed by arranging the units A and B individually or in combination in a matrix of M rows and M columns; the substrate is divided into a plurality of square grids, the surface of the square module attached to the substrate is assumed to be the bottom surface, the size of each square grid is the same as the bottom surface size of the square module, and a card slot is arranged on the substrate surface corresponding to the square grid; a protrusion matching the card slot is provided at the bottom of the square module, the phase code of the square module composed of the unit A is assumed to be 1, and the phase code of the square module composed of the unit B is assumed to be 0, the square module composed of the unit A and the square module composed of the unit B are arranged according to the set phase code sequence, and the square modules are embedded in the card slots and fixed.

10. Use of the omnidirectional scattering sound absorbing covering layer according to any one of claims 1 to 7, characterized in that: Used to be installed on underwater stealth devices.

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