A metasurface structural unit capable of simultaneously regulating reflected sound waves and transmitted sound waves

Abstract

The present invention discloses a metasurface structural unit capable of simultaneously regulating reflected sound waves and transmitted sound waves, which includes a first maze structure, a second maze structure, a third maze structure, an opening structure, a fourth maze structure, and a fifth maze structure stacked in sequence from top to bottom. When sound waves are incident from the bottom of the metasurface structural unit, partial reflection occurs at the interfaces of the fifth and fourth maze structures and the opening structure, and the remaining sound waves are transmitted through the opening structure and the third, second, and first maze structures. The energy ratio of the reflected sound waves and the transmitted sound waves can be adjusted by the opening width of the opening structure; the phase of the reflected sound waves can be adjusted by the widths of the third left and right partition plates in the fourth maze structure; the phase of the transmitted sound waves can be jointly adjusted by the widths of the third left and right partition plates in the fourth maze structure and the widths of the second left and right partition plates in the second maze structure, thereby achieving the simultaneous regulation of the reflected sound waves and the transmitted sound waves.

Description

Technical Field

[0001] The present invention relates to a metasurface structural unit capable of simultaneously regulating reflected sound waves and transmitted sound waves. Background Art

[0002] Sound field regulation is an important topic in the field of acoustic materials. The traditional methods for realizing sound field regulation mainly include two types: one is to use an array arrangement of numerous acoustic transducers to construct an acoustic array, and each acoustic transducer in the electrical end is manipulated to regulate the reflected sound wave or the transmitted sound wave, so as to realize the required reflected sound field or transmitted sound field; the second is to use an array arrangement of numerous metasurface structural units to construct an acoustic metasurface, and the geometric structure, geometric parameters, etc. of each metasurface structural unit are manipulated to regulate the reflected sound wave or the transmitted sound wave, so as to realize the required reflected sound field or transmitted sound field, such as acoustic redirection emission, multi-point focusing, etc. Typical metasurface structural units for constructing acoustic metasurfaces include maze structure type, Helmholtz resonance type, thin film structure type, piezoelectric material type, and five-mode type. However, these metasurface structural units can only perform single regulation on the reflected sound wave or the transmitted sound wave, that is, only a reflective metasurface can be constructed to regulate the reflected sound field or a transmissive metasurface can be constructed to regulate the transmitted sound field. Summary of the Invention

[0003] In order to solve the above technical problems, the present invention provides a metasurface structural unit with a simple structure that can simultaneously regulate reflected sound waves and transmitted sound waves.

[0004] The technical solution of the present invention to solve the above problems is: a metasurface structural unit capable of simultaneously regulating reflected sound waves and transmitted sound waves, including a first-layer maze structure, a second-layer maze structure, a third-layer maze structure, an opening structure, a fourth-layer maze structure, and a fifth-layer maze structure stacked in sequence from top to bottom.

[0005] For the above metasurface structural unit capable of simultaneously regulating reflected sound waves and transmitted sound waves, the first-layer maze structure, the third-layer maze structure, and the fifth-layer maze structure have the same structure, including two first left plate-shaped materials and two first right plate-shaped materials arranged in parallel. A first left partition plate is provided in the middle of the right side surface of the first left plate-shaped material, and two first right partition plates are provided at the upper and lower ends of the left side surface of the first right plate-shaped material. The first left partition plate and the first right partition plates are arranged in parallel and staggered to form a maze-shaped curling groove; the widths of the first left and right partition plates are equal, the distance between the first left plate-shaped material and the first right partition plate is equal to the distance between the first right plate-shaped material and the first left partition plate, and is equal to the distance between every two adjacent partition plates in the first left and right partition plates.

[0006] The above-mentioned metasurface structural unit capable of simultaneously regulating reflected sound waves and transmitted sound waves, wherein the second-layer maze structure includes two second left plate-shaped materials and two second right plate-shaped materials arranged in parallel. Four second left partition plates are evenly arranged on the right side surface of the second left plate-shaped material, and five second right partition plates are evenly arranged on the left side surface of the second right plate-shaped material. The second left partition plates and the second right partition plates are arranged in parallel and staggered to form a maze-shaped curly groove; the widths of the second left and right partition plates are equal, the distance between the second left plate-shaped material and the second right partition plates is equal to the distance between the second right plate-shaped material and the second left partition plates, and is equal to the distance between every two adjacent partition plates among the second left and right partition plates.

[0007] The above-mentioned metasurface structural unit capable of simultaneously regulating reflected sound waves and transmitted sound waves, wherein the opening structure includes two third left plate-shaped materials and two third right plate-shaped materials arranged in parallel. An opening is formed between the third left plate-shaped material and the third right plate-shaped material.

[0008] The above-mentioned metasurface structural unit capable of simultaneously regulating reflected sound waves and transmitted sound waves, wherein the fourth-layer maze structure includes two fourth left plate-shaped materials and two fourth right plate-shaped materials arranged in parallel. Two third left partition plates are evenly arranged on the right side surface of the fourth left plate-shaped material, and three third right partition plates are evenly arranged on the left side surface of the fourth right plate-shaped material. The third left partition plates and the third right partition plates are arranged in parallel and staggered to form a maze-shaped curly groove; the widths of the third left and right partition plates are equal, the distance between the fourth left plate-shaped material and the third right partition plates is equal to the distance between the fourth right plate-shaped material and the third left partition plates, and is equal to the distance between every two adjacent partition plates among the third left and right partition plates.

[0009] The above-mentioned metasurface structural unit capable of simultaneously regulating reflected sound waves and transmitted sound waves, wherein the maze-shaped curly groove of the first-layer maze structure, the maze-shaped curly groove of the second-layer maze structure, the maze-shaped curly groove of the third-layer maze structure, the through groove of the opening structure, the maze-shaped curly groove of the fourth-layer maze structure, and the maze-shaped curly groove of the fifth-layer maze structure are connected in sequence to form the sound channel of the overall metasurface structural unit.

[0010] The above-mentioned metasurface structural unit capable of simultaneously regulating reflected sound waves and transmitted sound waves, wherein the widths of the second left and right partition plates, the width of the opening, and the widths of the third left and right partition plates are adjustable.

[0011] The above-mentioned metasurface structural unit capable of simultaneously regulating reflected sound waves and transmitted sound waves, wherein the length t of the opening structure p is λ / 4, where λ is the wavelength of the incident sound wave.

[0012] The above-mentioned metasurface structural unit capable of simultaneously regulating reflected sound waves and transmitted sound waves has a rectangular overall cross-section, and the width is 0.1λ - 0.3λ, where λ is the wavelength of the incident sound wave.

[0013] The above-mentioned metasurface structural unit capable of simultaneously regulating reflected sound waves and transmitted sound waves is arranged in a background medium, and the acoustic impedance of the metasurface structural unit exceeds 100 times that of the background medium.

[0014] The beneficial effect of the present invention is that: in the metasurface structural unit of the present invention, when a sound wave is incident from the bottom of the metasurface structural unit, it is partially reflected at the interfaces of the fifth, fourth layer maze structures and the opening structure, and the remaining sound waves are transmitted through the opening structure and the third, second, and first layer maze structures. The energy ratio of the reflected sound wave and the transmitted sound wave can be adjusted by the opening width w of the opening structure p ; the phase of the reflected sound wave can be adjusted by the width l of the third left and right partition plates in the fourth layer maze structure ir ; the phase of the transmitted sound wave can be adjusted by the width l of the third left and right partition plates in the fourth layer maze structure ir and the width l of the second left and right partition plates in the second layer maze structure it jointly, thereby realizing the simultaneous regulation of the reflected sound wave and the transmitted sound wave. Description of the Drawings

[0015] Figure 1 It is a three-dimensional view of the metasurface structural unit of the present invention.

[0016] Figure 2 It is a two-dimensional cross-sectional view of the metasurface structural unit of the present invention.

[0017] Figure 3 It is a transmission characteristic diagram of the metasurface structural unit of the present invention, including the variation relationships of reflectivity, transmittance, reflection phase, and transmission phase with adjustable parameters l ir , w p and l it .

[0018] Figure 4 It is a simulation diagram of the incident sound field and scattered sound field distributions when abnormal sound wave reflection and transmission are carried out using the present invention.

[0019] Figure 5 It is a simulation diagram of the incident sound field and scattered sound intensity distributions when acoustic multi-point focusing is carried out using the present invention. Detailed Embodiments

[0020] The present invention will be further described below in conjunction with the drawings and embodiments.

[0021] As Figure 1As shown in the figure, a meta - surface structural unit capable of simultaneously regulating reflected sound waves and transmitted sound waves includes a first maze structure 1, a second maze structure 2, a third maze structure 3, an opening structure 4, a fourth maze structure 5, and a fifth maze structure 6 stacked in sequence from top to bottom.

[0022] The first maze structure 1, the third maze structure 3, and the fifth maze structure 6 have the same structure. As Figure 2 shown, it includes two first left plate - like materials 11 and two first right plate - like materials 12 arranged in parallel. In the middle of the right side of the first left plate - like material 11, there is a first left partition plate 13. At the upper and lower ends of the left side of the first right plate - like material 12, there are two first right partition plates 14. The first left partition plate 13 and the first right partition plates 14 are arranged in parallel and staggered to form a maze - shaped coiled groove. The widths of the first left partition plate 13 and the first right partition plates 14 are equal. The distance between the first left plate - like material 11 and the first right partition plate 14 is equal to the distance between the first right plate - like material 12 and the first left partition plate 13, and is equal to the distance between every two adjacent partition plates among the first left partition plate 13 and the first right partition plates 14.

[0023] The second maze structure 2 includes two second left plate - like materials 21 and two second right plate - like materials 22 arranged in parallel. On the right side of the second left plate - like material 21, there are four second left partition plates 23 evenly arranged. On the left side of the second right plate - like material 22, there are five second right partition plates 24 evenly arranged. The second left partition plates 23 and the second right partition plates 24 are arranged in parallel and staggered to form a maze - shaped coiled groove. The widths of the second left partition plates 23 and the second right partition plates 24 are equal. The distance between the second left plate - like material 21 and the second right partition plate 24 is equal to the distance between the second right plate - like material 22 and the second left partition plate 23, and is equal to the distance between every two adjacent partition plates among the second left partition plates 23 and the second right partition plates 24. The opening structure 4 includes two third left plate - like materials 41 and two third right plate - like materials 42 arranged in parallel. An opening 43 is formed between the third left plate - like material 41 and the third right plate - like material 42. The length t p of the opening structure 4 is λ / 4, where λ is the wavelength of the incident sound wave.

[0024] The fourth-layer maze structure 5 includes two fourth left plate-shaped materials 51 and two fourth right plate-shaped materials 52 arranged in parallel. On the right side surface of the fourth left plate-shaped material 51, two third left partition plates 53 are evenly provided. On the left side surface of the fourth right plate-shaped material 52, three third right partition plates 54 are evenly provided. The third left partition plates 53 and the third right partition plates 54 are arranged in parallel and staggered to form a maze-shaped curling groove. The widths of the third left partition plates 53 and the third right partition plates 54 are equal. The distance between the fourth left plate-shaped material 51 and the third right partition plate 54 is equal to the distance between the fourth right plate-shaped material 52 and the third left partition plate 53, and is equal to the distance between every two adjacent partition plates among the third left partition plates 53 and the third right partition plates 54.

[0025] The maze-shaped curling groove of the first-layer maze structure 1, the maze-shaped curling groove of the second-layer maze structure 2, the maze-shaped curling groove of the third-layer maze structure 3, the through groove of the opening structure 4, the maze-shaped curling groove of the fourth-layer maze structure 5, and the maze-shaped curling groove of the fifth-layer maze structure 6 are connected in sequence to form the sound channel of the overall metasurface structure unit.

[0026] The widths l of the second left partition plate 23 and the second right partition plate 24 ir , the width w of the opening 43 p , the widths l of the third left partition plate 53 and the third right partition plate 54 it are all adjustable.

[0027] The overall cross-section of the metasurface structure unit is rectangular, and the width is 0.1λ - 0.3λ, where λ is the wavelength of the incident sound wave. The metasurface structure unit is arranged in the background medium, and the acoustic impedance of the metasurface structure unit exceeds 100 times the acoustic impedance of the background medium.

[0028] Figure 2 This is the two-dimensional cross-sectional view of the metasurface structure unit of the present invention. In the embodiments of the present invention, the geometric parameters of the metasurface structure unit are all set as follows: the width a of the metasurface structure unit = 20 mm, the thickness d of all the left plate-shaped materials and all the partition plates w = 1 mm, the widths l of all the partition plates in the first, third, and fifth-layer maze structures b = 8 mm, the distances between the left plate-shaped materials and the right partition plates and between the right plate-shaped materials and the left partition plates in the first, third, and fifth-layer maze structures, and the distances w between every two adjacent partition plates in the first, third, and fifth-layer maze structures b = 4 mm, the length L of the first, third, and fifth-layer maze structures b = 2w b + 3d w, the distances between the left plate-like materials and the right partition plates and between the right plate-like materials and the left partition plates in the second and fourth layer maze structures, as well as the distance w between every two adjacent partition plates in the second and fourth layer maze structures i = 1 mm, and the length t of the opening structure p = 25 mm. The remaining geometric parameters: the widths l of the third left and right partition plates in the fourth layer maze structure ir , the opening width w of the opening structure p and the widths l of the second left and right partition plates in the second layer maze structure it are adjustable parameters.

[0029] Figure 3 is the transmission characteristic diagram of the metasurface structure unit of the present invention, including the relationships of reflectivity, transmittance, reflection phase and transmission phase with respect to the adjustable parameters l ir , w p and l it . When performing simulation calculations on the transmission characteristics of the metasurface structure unit of the present invention and on all embodiments of the acoustic metasurface constructed by the metasurface structure unit of the present invention, the boundary condition of the metasurface structure unit of the present invention is set as an acoustically hard boundary condition. The background medium is set as air, with its density and sound speed being 1.2 kg / m 3 and 343 m / s respectively, and the frequency of the incident sound wave is set as 3430 Hz. When performing simulation calculations on the reflectivity, the adjustable parameter l it is set to 10 mm; when performing simulation calculations on the transmittance, the adjustable parameter l ir is set to 10 mm; when performing simulation calculations on the reflection phase and transmission phase, the adjustable parameter w p is set to 11.08 mm. From Figure 3 , three conclusions can be drawn: (1) The reflectivity and transmittance are basically only affected by the adjustable parameter w p ; (2) The reflection phase is only affected by the adjustable parameter l ir ; (3) The transmission phase is affected by the adjustable parameters l ir and l it jointly. From this, the steps for simultaneously regulating the reflected sound wave and the transmitted sound wave using the metasurface structure unit of the present invention are as follows: (1) Determine the value of the adjustable parameter w p according to the energy ratio of the required reflected sound wave and transmitted sound wave; (2) Determine the value of the adjustable parameter l ir according to the phase of the required reflected sound wave; (3) Determine the value of the adjustable parameter l it according to the phase of the required transmitted sound wave. In all embodiments of the present invention, w p= 11.08 mm, and the reflectivity is about 50% at this time. Therefore, in the present invention, the steps of designing the acoustic metasurface are as follows: (1) Deduce the reflection phase distribution required to be provided by the acoustic metasurface according to the distributions of the incident sound field and the target reflection sound field, and thereby determine the adjustable parameter l of each super-surface structure unit in the acoustic metasurface ir value; (2) Deduce the transmission phase distribution required to be provided by the acoustic metasurface according to the distributions of the incident sound field and the target transmission sound field, and thereby determine the adjustable parameter l of each super-surface structure unit in the acoustic metasurface it value.

[0030] Abnormal sound wave reflection and transmission:

[0031] As Figure 4 described, the sound wave is normally incident on the metasurface from the bottom, and abnormal sound wave reflection with a reflection angle θ r = -56.4° and abnormal sound wave transmission with a transmission angle θ t = -33.7° occur. According to the generalized Snell's law

[0032]

[0033] wherein, k0 = 2π / λ0 is the wave number of air, λ0 = 100 mm is the wavelength in air, θ r is the reflection angle, θ t is the transmission angle, θ i is the incident angle, or is the phase gradient of the acoustic metasurface, and D is the period length of the acoustic metasurface. The phase gradient of the acoustic metasurface required to achieve the target reflection sound field is That is, a linear change of -2π in the reflection phase needs to be achieved within one period of the acoustic metasurface with a length of 1.2λ0. Since the width a of the super-surface structure unit of the present invention is 0.2λ0, and the reflection phase is only related to the adjustable parameter l ir Therefore, by setting the values of the adjustable parameter l of 6 super-surface structure units of the present invention respectively ir This period can be constructed, and the reflection phase difference between adjacent super-surface structure units is -π / 3. The phase gradient of the acoustic metasurface required to achieve the target transmission sound field is That is, a linear change of -2π in the transmission phase needs to be achieved within one period of the acoustic metasurface with a length of 1.8λ0. And since the transmission phase of the super-surface structure unit of the present invention is related to both the adjustable parameter l ir and l it Therefore, on the premise that every 6 of the adjustable parameters l of the acoustic metasurface are in one period, 18 super-surface structure units need to be used to set the corresponding adjustable parameters l ir corresponding adjustable parameter l under ir the corresponding adjustable parameter lit Two periods with the desired transmission phase can be constructed, as shown in Table 1.

[0034] Table 1 Adjustable parameters l of each supercell structure unit of the present invention in the acoustic metasurface ir and l it Value (unit: mm)

[0035]

[0036] Acoustic multi-point focusing:

[0037] As Figure 5 described, the sound wave is normally incident on the metasurface from the bottom, and two-point acoustic focusing occurs in the reflected sound field and the transmitted sound field respectively. That is to say, for this acoustic metasurface, the target sound field includes the reflected sound field and the transmitted sound field. Among them, the target reflected sound field is: where p ra and are the amplitude and phase of the target reflected sound field respectively, k0 = 2π / λ0 is the wave number of air, λ0 is the wavelength in air, (x1, z1) = (-6λ0, -8λ0) and (x2, z2) = (8λ0, -6λ0) are the coordinates of the two focal points in the target reflected sound field. t1 = 20 mm is the total length of the fifth and fourth layer maze structures. The target transmitted sound field is: where p ta and are the amplitude and phase of the target transmitted sound field respectively, (x3, z3) = (-5λ0, 8λ0) and (x4, z4) = (6λ0, 6λ0) are the coordinates of the two focal points in the target transmitted sound field. t2 = 64 mm is the total length of the opening structure and the third, second, and first layer maze structures. In this embodiment, 100 Figure 1 supercell structures of the present invention shown are used to construct the full-space metasurface. Since the width a of the supercell structure unit of the present invention is 0.2λ0, the total length of this acoustic metasurface is 20λ0. First, the reflection phase distribution required by the acoustic metasurface is deduced according to the distribution of the incident sound field and the target reflected sound field, and thus the adjustable parameters l ir of each supercell structure unit of the present invention in the acoustic metasurface are determined; then, the transmission phase distribution required by the acoustic metasurface is deduced according to the distribution of the incident sound field and the target transmitted sound field, and thus the adjustable parameters l it of each supercell structure unit of the present invention in the acoustic metasurface are determined. As shown in Table 2.

[0038] Table 2 Adjustable parameters l of each supercell structure unit of the present invention in the acoustic metasurface ir and l itValue (unit: mm)

[0039]

[0040]

[0041] In the meta - surface structural unit of the present invention, when acoustic waves are incident from the bottom of the meta - surface structural unit, partial reflection occurs at the interfaces between the fifth and fourth - layer maze structures and the opening structure, and the remaining acoustic waves are transmitted through the opening structure and the third, second, and first - layer maze structures. The energy ratio of the reflected acoustic waves and the transmitted acoustic waves can be adjusted by the opening width w p of the opening structure; the phase of the reflected acoustic waves can be adjusted by the width l ir of the third left and right partition plates in the fourth - layer maze structure; the phase of the transmitted acoustic waves can be adjusted by the width l ir of the third left and right partition plates in the fourth - layer maze structure and the width l it of the second left and right partition plates in the second - layer maze structure jointly, thereby achieving the simultaneous regulation of the reflected acoustic waves and the transmitted acoustic waves.

Claims

1. A meta - surface structural unit capable of simultaneously regulating reflected sound waves and transmitted sound waves, characterized in that: It includes a first maze structure, a second maze structure, a third maze structure, an opening structure, a fourth maze structure, and a fifth maze structure stacked in sequence from top to bottom; The first maze structure, the third maze structure, and the fifth maze structure have the same structure, including two first left plate-like materials and two first right plate-like materials arranged in parallel. In the middle of the right side of the first left plate-like material, there is a first left partition plate. At the upper and lower ends of the left side of the first right plate-like material, there are two first right partition plates. The first left partition plate and the first right partition plates are arranged in parallel and staggered to form a maze-shaped curling groove; the widths of the first left and right partition plates are equal, the distance between the first left plate-like material and the first right partition plate is equal to the distance between the first right plate-like material and the first left partition plate, and is equal to the distance between every two adjacent partition plates among the first left and right partition plates; The second maze structure includes two second left plate-like materials and two second right plate-like materials arranged in parallel. On the right side of the second left plate-like material, four second left partition plates are evenly arranged. On the left side of the second right plate-like material, five second right partition plates are evenly arranged. The second left partition plates and the second right partition plates are arranged in parallel and staggered to form a maze-shaped curling groove; the widths of the second left and right partition plates are equal, the distance between the second left plate-like material and the second right partition plate is equal to the distance between the second right plate-like material and the second left partition plate, and is equal to the distance between every two adjacent partition plates among the second left and right partition plates; The opening structure includes two third left plate-like materials and two third right plate-like materials arranged in parallel. An opening is formed between the third left plate-like material and the third right plate-like material; The fourth maze structure includes two fourth left plate-like materials and two fourth right plate-like materials arranged in parallel. On the right side of the fourth left plate-like material, two third left partition plates are evenly arranged. On the left side of the fourth right plate-like material, three third right partition plates are evenly arranged. The third left partition plates and the third right partition plates are arranged in parallel and staggered to form a maze-shaped curling groove; the widths of the third left and right partition plates are equal, the distance between the fourth left plate-like material and the third right partition plate is equal to the distance between the fourth right plate-like material and the third left partition plate, and is equal to the distance between every two adjacent partition plates among the third left and right partition plates.

2. The meta - surface structural unit capable of simultaneously regulating reflected sound waves and transmitted sound waves according to claim 1, wherein: The maze-shaped curling groove of the first maze structure, the maze-shaped curling groove of the second maze structure, the maze-shaped curling groove of the third maze structure, the through groove of the opening structure, the maze-shaped curling groove of the fourth maze structure, and the maze-shaped curling groove of the fifth maze structure are connected in sequence to form the sound channel of the overall metasurface structure unit.

3. The meta - surface structural unit capable of simultaneously regulating reflected sound waves and transmitted sound waves according to claim 1, wherein: The widths of the second left and right partition plates, the width of the opening, and the widths of the third left and right partition plates are adjustable.

4. The meta - surface structural unit capable of simultaneously regulating reflected sound waves and transmitted sound waves according to claim 1, wherein: The length t of the opening structure p is λ / 4, where λ is the wavelength of the incident sound wave.

5. The meta - surface structural unit capable of simultaneously regulating reflected sound waves and transmitted sound waves according to claim 1, wherein: The overall cross-section of the metasurface structure unit is rectangular, and the width is 0.1λ - 0.3λ, where λ is the wavelength of the incident sound wave.

6. The meta - surface structural unit capable of simultaneously regulating reflected sound waves and transmitted sound waves according to claim 1, wherein: The metasurface structure unit is arranged in a background medium, and the acoustic impedance of the metasurface structure unit exceeds 100 times the acoustic impedance of the background medium.

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