An acoustic metasurface capable of tunable underwater acoustic wave reflection sound field

Abstract

This invention discloses an acoustic metasurface for tunable underwater acoustic wave reflection sound field, belonging to the field of acoustic metasurface technology. The acoustic metasurface includes a substrate and N media arranged sequentially on the substrate, each media bonded to the substrate. Assuming the length of the N media arranged from left to right is L and the thickness is d, the length of each media is such that the position coordinates of the nth media from left to right satisfy the formula requirements. The N media have the same density, and the density differs from that of water by no more than ±20%. Furthermore, the modulus of the nth media satisfies the design formula requirements. This invention can control the reflected sound field of perpendicularly incident plane sound waves, significantly reducing the sound pressure level near 90 degrees of the reflected sound field.

Description

Technical Field

[0001] This invention belongs to the field of acoustic metasurface technology, specifically relating to an acoustic metasurface that can control the sound field of underwater sound wave reflection. Background Technology

[0002] Acoustic metasurfaces are two-dimensional arrays of planar structures composed of ingeniously designed structural units. By introducing phase abrupt changes with gradient variations, the wavefront phase can be controlled, allowing for arbitrary manipulation of the reflection and refraction angles, thus bringing entirely new possibilities to sound wave manipulation. Numerous patents related to acoustic metasurfaces have been published, demonstrating how they can manipulate sound waves to achieve acoustic phenomena such as anomalous reflection, focusing, and vortices.

[0003] Most existing metasurface research uses air as the background, while research on acoustic metasurfaces using water as the background is relatively limited.

[0004] For an ordinary flat surface (such as a regular flat plate made of steel), when an incident sound wave is incident perpendicularly onto the plate, the reflected sound wave is reflected along the same path as the incident sound wave (around 90 degrees of the reflected sound field), resulting in a very strong sound pressure level around 90 degrees of the reflected sound field and a very weak sound pressure level in other directions. Summary of the Invention

[0005] In view of this, the present invention provides an acoustic metasurface that can regulate the reflected sound field of underwater sound waves, which can regulate the reflected sound field of vertically incident plane sound waves and significantly reduce the sound pressure level in the direction near 90 degrees of the reflected sound field.

[0006] An acoustic metasurface with tunable underwater acoustic wave reflection sound field, comprising a base plate and N (N is a positive integer) media arranged sequentially on the base plate, each media being bonded to the base plate;

[0007] Assuming N media are arranged from left to right with a length of L and a thickness of d, then the length of each media is d. The position coordinates of the nth medium from left to right are: The physical properties of N media meet the following requirements:

[0008] (1) The density of N media is the same, and the density of each medium differs from that of water by no more than ±20%.

[0009] (2) The modulus of the nth medium is Where K0 is the modulus of water, d is the thickness of each medium, L is the length of the N media arranged from left to right, and C1 and C2 are artificially designed parameters.

[0010] Furthermore, the base plate has a rectangular cross-sectional shape, and the N media have the same rectangular cross-sectional shape.

[0011] Furthermore, the base plate is made of steel, aluminum alloy, or titanium alloy.

[0012] Furthermore, the medium is replaced by a microstructure.

[0013] Furthermore, the overall dimensions of the microstructure are the same as the overall dimensions of the corresponding medium, the equivalent density of the microstructure is approximately equal to the density of the corresponding medium, the equivalent modulus of the microstructure is approximately equal to the modulus of the corresponding medium, and there are no abrupt shape changes between adjacent microstructures, ensuring smooth connection between adjacent microstructures.

[0014] Beneficial effects:

[0015] 1. The medium on the base plate of this invention plays a role in regulating the sound field. The modulus formula of the medium clearly gives the parameter distribution law of the metasurface. Therefore, the medium set according to its law can regulate the reflected sound field of vertically incident plane sound waves within a certain frequency range, and can significantly reduce the sound pressure level in the direction of the reflected sound field near 90 degrees. Laying it on the surface of underwater structures can avoid detection by active sonar.

[0016] 2. After the metasurface of the present invention receives the incident sound wave, the incident sound wave is generally a plane wave. The entire plane wave hits the metasurface. The incident sound wave makes the modulus large in the middle of the metasurface and the modulus smaller towards the two sides. This design makes the impedance large in the middle of the metasurface and the impedance smaller towards the two sides. After the sound wave is incident on the metasurface, some of the energy will flow along the metasurface to the middle and be concentrated before being radiated out, which reduces the radiated energy in the direction of the metasurface around 90 degrees.

[0017] 3. The cross-sectional shape of the base plate of the present invention is rectangular, and the cross-sectional shape of the N media is the same rectangular. The bonding method and the rectangular cross-section of the media and the base plate make the acoustic metasurface easy to mass-produce and help save production costs. Attached Figure Description

[0018] Figure 1 It is an acoustic metasurface that can tunable underwater sound wave reflection sound field;

[0019] Figure 2 A schematic diagram of a metasurface structure realized using microstructure;

[0020] Figure 3 This is a schematic diagram of the base plate structure;

[0021] Figure 4 The simulation results show the sound field of the 3000Hz sound wave reflection from the base plate.

[0022] Figure 5 The simulation results are for the sound field of 3000Hz acoustic wave reflection from the metasurface.

[0023] Figure 6Comparison of simulation results of sound pressure level of 3000Hz acoustic wave reflection field between base plate and metasurface;

[0024] Figure 7 The simulation results show the sound field reflection of the 5000Hz sound wave from the base plate.

[0025] Figure 8 The simulation results are for the sound field of 5000Hz acoustic wave reflection from the metasurface.

[0026] Figure 9 Comparison of simulation results of sound pressure level of 5000Hz acoustic wave reflection field between base plate and metasurface;

[0027] Figure 10 The simulation results are for the sound field of the 8000Hz sound wave reflection from the base plate.

[0028] Figure 11 The simulation results are for the sound field of 8000Hz acoustic wave reflection from the metasurface.

[0029] Figure 12 Comparison of simulation results of sound pressure level of 8000Hz acoustic wave reflection field between base plate and metasurface;

[0030] Figure 13 The simulation results are for the sound field of the 10000Hz sound wave reflection from the base plate.

[0031] Figure 14 The simulation results are for the sound field of 10000Hz acoustic wave reflection from the metasurface.

[0032] Figure 15 The simulation results of the sound pressure level of the sound field reflected by the 10000Hz sound wave on the base plate and the metasurface are compared.

[0033] 1-medium, 2-base plate. Detailed Implementation

[0034] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0035] This invention provides an acoustic metasurface that can tunable the underwater sound wave reflection sound field, such as... Figure 1 This is a geometric schematic diagram of the two-dimensional metasurface cross-section of the present invention. In this embodiment, the base plate has a rectangular cross-section with a length of 1m and a thickness of 10mm, and is made of steel. Twenty media are arranged closely from left to right on the base plate, each media having a rectangular cross-section with a length of 54mm and a thickness of 40mm.

[0036] If N = 20 media arranged from left to right have a length of L = 1.08 m and a thickness of d = 0.04 m, then the coordinates of the nth media from left to right are: The physical properties of the 20 media meet the following requirements:

[0037] (1) The density of all 20 media is 1200 kg / m³ 3 ;

[0038] (2) The modulus of the nth medium is Wherein, K0 = 2.19e9Pa is the modulus of water, and C1 = -0.37m and C2 = 0.48m are parameters that can be designed artificially. Whether the parameter values ​​are appropriate will be verified through subsequent simulations.

[0039] Based on the above scheme, calculate the modulus (K) of the 20 media relative to water from left to right. n The moduli of the medium (K0) are as follows: 0.2409, 0.02724, 0.3106, 0.3569, 0.4124, 0.4776, 0.5503, 0.6244, 0.6879, 0.7255, 0.7255, 0.6879, 0.6244, 0.5503, 0.4776, 0.4124, 0.3569, 0.3106, 0.2724, 0.2409. It can be observed that the modulus of the medium exhibits a symmetrical distribution.

[0040] The above only defines the external dimensions and density and modulus properties of each medium. To fabricate an actual metasurface, specific structures are needed to represent the geometric and physical properties of each medium. Using topological shape optimization design methods, 20 microstructures corresponding to each medium can be designed as a whole. Each microstructure has the same external dimensions, approximately equal density, and modulus as its corresponding medium. Furthermore, there are no abrupt shape changes between adjacent microstructures, ensuring smooth connections and facilitating manufacturing.

[0041] Figure 2 It is a gradient hexagonal honeycomb microstructure with 20 media corresponding to a certain shape optimization design method. The material of the honeycomb microstructure is titanium alloy. Figure 2 Overall dimensions and Figure 1 same. Figure 2 The equivalent density of each local microstructure is approximately equal to the density of the medium at the corresponding location, and the equivalent modulus of each local microstructure is approximately equal to the modulus of the medium at the corresponding location.

[0042] Figure 3 It's the base plate. Figures 1-3 The base plates in both are identical in shape and made of steel.

[0043] To verify Figure 2 Metasurfaces possess the ability to modulate reflected sound fields, which is verified through finite element acoustic simulation. Two models are used for comparison: Figure 3 base plate and Figure 2 Metasurfaces. The simulation comparison method is as follows: The simulation background environment is underwater. Under the same simulation conditions, the following comparisons are made: Figure 3 base plate and Figure 2 Plane sound waves of different frequencies are incident perpendicularly on the metasurface, and the reflected sound fields are calculated respectively; then the reflected sound fields of the base plate and the metasurface under different frequency sound waves are compared.

[0044] Figures 4-6 These are the acoustic simulation results for 3000Hz sound waves.

[0045] Figure 4 It is the sound field reflected by the sound wave from the bottom plate. As you can see, the reflected sound wave is reflected along the original path along the incident direction. This results in a very strong sound pressure level in the 90-degree direction of the reflected sound field, while the sound pressure level in other directions is very weak.

[0046] Figure 5 It is a metasurface acoustic wave reflection sound field, and you can see that the reflected sound waves are reflected in all directions.

[0047] Figure 6 This is a comparison of the sound pressure levels of the reflected sound fields on the base plate and the metasurface. The dashed line represents the sound pressure level of the reflected sound field on the base plate, and the solid line represents the sound pressure level of the reflected sound field on the metasurface. It can be seen that after the metasurface is installed on the base plate, the sound pressure level in the reflected sound field near 90 degrees is significantly reduced, with a decrease of 5.3 dB in the 90-degree direction.

[0048] Figures 7-9 These are the acoustic simulation results for 5000Hz sound waves.

[0049] Figure 7 It is the sound field reflected by the sound wave from the bottom plate, and the reflected sound wave is basically reflected along the original path along the incident direction. Figure 8 It is a metasurface acoustic wave reflection sound field, in which the reflected sound waves are reflected in all directions. Figure 9 This is a comparison of the sound pressure levels of the reflected sound fields on the base plate and the metasurface. The dashed line represents the sound pressure level of the reflected sound field on the base plate, and the solid line represents the sound pressure level of the reflected sound field on the metasurface. After the metasurface is installed on the base plate, the sound pressure level in the reflected sound field near 90 degrees is significantly reduced, with a decrease of 15.7 dB in the 90-degree direction.

[0050] Figures 10-12 These are the acoustic simulation results for 8000Hz sound waves.

[0051] Figure 10 It is the sound field reflected by the sound wave from the bottom plate, and the reflected sound wave is basically reflected along the original path along the incident direction. Figure 11 It is a metasurface acoustic wave reflection sound field, in which the reflected sound waves are reflected in all directions. Figure 12 This is a comparison of the sound pressure levels of the reflected sound fields on the base plate and the metasurface. The dashed line represents the sound pressure level of the reflected sound field on the base plate, and the solid line represents the sound pressure level of the reflected sound field on the metasurface. After the metasurface is installed on the base plate, the sound pressure level in the reflected sound field near 90 degrees is significantly reduced, with a decrease of 8.6 dB in the 90-degree direction.

[0052] Figures 13-15These are the results of an acoustic simulation at 10000Hz.

[0053] Figure 13 It is the sound field reflected by the sound wave from the bottom plate, and the reflected sound wave is basically reflected along the original path along the incident direction. Figure 14 It is a metasurface acoustic wave reflection sound field, in which the reflected sound waves are reflected in all directions. Figure 15 This is a comparison of the sound pressure levels of the reflected sound fields on the base plate and the metasurface. The dashed line represents the sound pressure level of the reflected sound field on the base plate, and the solid line represents the sound pressure level of the reflected sound field on the metasurface. After the metasurface is installed on the base plate, the sound pressure level in the reflected sound field near 90 degrees is significantly reduced, with a decrease of 10.7 dB in the 90-degree direction.

[0054] The above simulations show that the acoustic metasurface provided by this invention can significantly reduce the sound pressure level of reflected sound waves at different frequencies near 90 degrees.

[0055] In summary, the above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An acoustic metasurface with tunable underwater acoustic wave reflection sound field, characterized in that, The acoustic metasurface includes a base plate and components arranged sequentially on the base plate. N Each medium is bonded to the base plate; Assumption N The length of the media arranged from left to right is Thickness is d Then the length of each medium is From left to right n The position coordinates of the medium are , ; N The physical properties of the medium meet the following requirements: (1) N All media have the same density, and the density difference between them and water does not exceed ±20%; (2) No. n The modulus of the medium is ,in, The modulus of water, d For the thickness of each medium, L for N The length of each medium arranged from left to right and These are parameters designed by humans.

2. The acoustic metasurface with tunable underwater acoustic wave reflection sound field as described in claim 1, characterized in that, The base plate has a rectangular cross-sectional shape. N The cross-sectional shape of each medium is the same rectangle.

3. The acoustic metasurface with tunable underwater acoustic wave reflection sound field as described in claim 2, characterized in that, The base plate is made of steel, aluminum alloy, or titanium alloy.

4. The acoustic metasurface with tunable underwater acoustic wave reflection sound field as described in claim 3, characterized in that, The medium is replaced by a microstructure.

5. The acoustic metasurface with tunable underwater acoustic wave reflection sound field as described in claim 4, characterized in that, The overall dimensions of the microstructure are the same as those of the corresponding medium, the equivalent density of the microstructure is approximately equal to the density of the corresponding medium, the equivalent modulus of the microstructure is approximately equal to the modulus of the corresponding medium, and there are no abrupt shape changes between adjacent microstructures, ensuring smooth connection between adjacent microstructures.

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