An acoustic coding metasurface structure uniformly scattering under wideband arbitrary angle incidence

Abstract

The application provides a uniform scattering acoustic coding metasurface structure under wideband arbitrary angle incidence, comprising a plurality of base element structures arranged based on a directivity function, each base element structure comprising a Helmholtz cavity and a rectangular strip group; the Helmholtz cavities are arranged in horizontal parallel; the rectangular strip group is vertically added to the inside of the Helmholtz cavity to form the base element structure, and the rectangular strip group comprises upper rectangular strips, middle position rectangular strips, middle rectangular strips and end rectangular strips; in the plurality of base element structures, the number and affixed positions of the rectangular strips in the middle are different. The Helmholtz cavity is changed from the traditional vertical arrangement to horizontal parallel arrangement, the depth of the acoustic coding metasurface structure is shortened, the sound path difference is increased by adding the rectangular strip in the acoustic coding metasurface structure, the size is further reduced, the multi-angle incidence wideband scattering effect is finally achieved by arranging through the optimization algorithm, and the application has the advantages of wide frequency band, multiple angles and easy application.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of acoustically coded metasurface, and particularly relates to a uniform scattering acoustically coded metasurface structure under wide-frequency arbitrary-angle incidence. BACKGROUND

[0002] The regulation of wave propagation has been one of the key topics in the field of sound waves, and has potential applications in many fields. By designing functional units (or unit cells) with microstructures, refractive (transmissive) metasurfaces, reflective metasurfaces and absorptive metasurfaces are manufactured. Common structures of acoustic metasurfaces include comb-like metasurfaces composed of straight-well-like units, spiral structures with spiral channels, and plate-like resonant units. The reflection phase is changed by changing the path difference or realizing resonance, but these structure designs are complex and difficult to apply in reality.

[0003] As one of the structures of acoustic metasurfaces, digitally coded acoustic metasurface (ACM) is a kind of units with different phase differences (the phase difference interval is the same) that are "coded" by Boolean numbers or logic bits. Through the ordered combination and arrangement of several units on a two-dimensional or three-dimensional surface, the target demand metasurface structure is realized. The low-bit digitally coded acoustic metasurface requires fewer structure units, has the advantages of convenient processing, easy integration, and does not lose the general acoustic metasurface.

[0004] The low-bit digitally coded acoustic metasurface only needs a small number of unit cell formulas to constitute, and has the advantages of convenient design and processing, and wavefront regulation ability of general metasurface structure, so it can be widely applied to various scenes such as acoustic cabin design, sound energy collection, target sound stealth, etc.

[0005] The structure unit design of traditional acoustic metasurface is complex and difficult to apply in reality, the frequency band range is narrow, the angle of action is small, and the application is limited, therefore, the digitally coded metasurface is rising, which has different structures and arrangements for different functions, effectively overcoming the disadvantages of traditional acoustic metasurface. For example: a 2-element Helmholtz cavity structure coded metasurface is designed for vertical incidence to realize beam splitting and focusing of transmitted sound waves, and a 1-bit coded metasurface is proposed for perfect negative reflection, which is composed of a series of rectangular strips. Through the up-push or down-push operation, each strip can respond to logic bit "0" or "1", and by adjusting the coding sequence, perfect negative reflection in different directions is realized. However, there are few studies on scattering coded metasurfaces for multi-angle incidence and wide frequency band, so the digitally coded metasurface should be further studied. SUMMARY

[0006] The present application aims to solve the problem of the prior art that cannot be incident at multiple angles, and provides a uniform scattering acoustic coding metasurface structure under wideband arbitrary angle incidence, which shortens the depth of the acoustic coding metasurface structure by changing the traditional vertical discharge of the Helmholtz cavity to horizontal parallel discharge, increases the path difference by adding a rectangular strip inside the acoustic coding metasurface structure, further reduces the size, and achieves the effect of wideband multi-angle scattering by optimizing the algorithm for arrangement, has the advantages of wide frequency band, multiple angles of action and easy application.

[0007] To achieve the above-mentioned purpose, the technical solution provided by the present application is:

[0008] A uniform scattering acoustic coding metasurface structure under wideband arbitrary angle incidence, comprising: a plurality of unit structures, a hard acoustic wave reflection matrix for vertically placing the unit structures, and a plurality of unit structures being arranged based on a directivity function.

[0009] Each unit structure comprises a Helmholtz cavity and a rectangular strip group, the Helmholtz cavity is horizontally and parallelly arranged, and the rectangular strip group is vertically added inside the Helmholtz cavity to form the unit structure, and the rectangular strip group is used to increase the path difference.

[0010] In the two-dimensional structure and the three-dimensional structure with the same cross section as the two-dimensional structure, the propagation characteristics of the sound wave propagation are the same, so the cross section and two-dimensional design of the unit structure in the acoustic coding metasurface structure are as follows:

[0011] Each unit structure is placed vertically to the long side of the hard acoustic wave reflection matrix, the rectangular strip group comprises an upper rectangular strip, a middle position rectangular strip, a middle rectangular strip and an end rectangular strip, the long side of the upper rectangular strip is placed parallel to the acoustic wave reflection matrix, the long side of the middle position rectangular strip is placed vertically to the center of the upper rectangular strip and the short side is placed parallel to the acoustic wave reflection matrix, and the two form a T-shaped structure, the middle rectangular strip is divided into two groups and is arranged vertically to the upper rectangular strip and parallel to the middle position rectangular strip, a plurality of middle rectangular strips are located on both sides of the middle position rectangular strip, and the end rectangular strip is located at both ends of the long side of the acoustic wave reflection matrix.

[0012] The rectangular strip group attached to the hard acoustic wave reflection matrix forms the effect of the Helmholtz cavity and the labyrinth structure acting together, and the middle position rectangular strip and the middle rectangular strip form a mountain-like structure.

[0013] Among the plurality of unit structures, the number and attachment position of the rectangular strips located at the middle position of the hard acoustic wave reflection matrix are different.

[0014] As a further limitation of the application, the number of the plurality of end rectangular strips and the distance between the end rectangular strips are adjusted to correspond to different frequency ranges, and the phase response of the unit structure is adjusted, so that the phase response difference of the plurality of unit structures is π / 2 at f=4000Hz-8000Hz.

[0015] As a further limitation of the application, the unit structure is four kinds, and the number of each unit structure is nine;

[0016] After the 36 unit structures are arranged based on the directivity function, they are arranged perpendicular to the hard sound wave reflection matrix.

[0017] As a further limitation of the application, the size of the unit structure is set to one-tenth to one-fifth of the required sound wave wavelength;

[0018] In the rectangular strip group, the width of the upper rectangular strip is 17mm, the thickness is 1mm; the height of the middle position rectangular strip is 5mm, the width is 1mm; the height of the middle rectangular strip is 4mm, the width is 1mm; the height of the end rectangular strip is 6mm, the width is 1mm;

[0019] The length of the hard sound wave reflection matrix is 23mm, the width is 6mm, and the thickness is 10mm, and the hard sound wave reflection matrix has the same cross-sectional size.

[0020] As a further limitation of the application, the unit structure has four kinds, and the phase is divided into a first unit structure, a second unit structure, a third unit structure, and a fourth unit structure from small to large;

[0021] In the wideband arbitrary angle incident uniform scattering acoustic coding metasurface structure, the unit structure arrangement mode is:

[0022] The first unit structure, the second unit structure, the second unit structure, the second unit structure, the first unit structure, the third unit structure, the first unit structure, the fourth unit structure, the fourth unit structure, the first unit structure, the fourth unit structure, the fourth unit structure, the third unit structure, the fourth unit structure, the second unit structure, the first unit structure, the second unit structure, the third unit structure, the third unit structure, the second unit structure, the first unit structure, the fourth unit structure, the third unit structure, the second unit structure, the fourth unit structure, the first unit structure, the third unit structure, the third unit structure, the third unit structure, the fourth unit structure, the first unit structure, the third unit structure, the third unit structure, the fourth unit structure, the first unit structure, the third unit structure.

[0023] As a further limitation of the application, the side of the unit structure is perpendicular to the bottom;

[0024] The basic structures are closely arranged in alignment respectively and are perpendicular to the bottom edge and parallel to the side edge of the hard acoustic wave reflection matrix.

[0025] As a further limitation of the application, the rectangular strip group and the hard acoustic wave reflection matrix are both made of aluminum material;

[0026] The density of the rectangular strip group and the hard acoustic wave reflection matrix is 2.7 g / m 3 , the Young's modulus is 70 GpPa, and the acoustic velocity is 6300 m / s.

[0027] As a further limitation of the application, the acoustic coding metasurface structure uniformly scatters under wideband arbitrary angle incidence, and the frequency of f=4000 Hz-8000 Hz and the sound wave of multi-angle incidence are regulated to make the reflected wave uniformly scattered.

[0028] As a further limitation of the application, the directivity function includes the angle and frequency of the incident sound wave, the angle and frequency are known quantities, and the phase information of the coded arrangement is an unknown quantity; the angle is 0°, 30°, 45°, 60°, and 70°, and the frequency is 4 kHz-8 kHz.

[0029] The directivity function is taken as the objective function and is maximized, and the surface of the hard acoustic wave reflection matrix is divided into 36 blocks, and the data of each basic structure is 9 as a constraint function;

[0030] The multiple basic structures are temporarily placed on the surface of the hard acoustic wave reflection matrix according to the unknown arrangement, and the optimal coding arrangement of the multiple basic structures is obtained by using the directivity function.

[0031] As a further limitation of the application, the directivity function includes:

[0032]

[0033]

[0034] In the formula, θ represents the scattering wave elevation angle, represents the scattering wave azimuth angle, θ i represents the incident sound wave elevation angle, represents the incident sound wave azimuth angle, represents the directivity function of the scattering wave, represents the far-field scattering amplitude, represents the directivity function of the coding metasurface, represents the directivity function of the smooth surface without structure of the same size, σ R represents the diffusion performance of the coding metasurface compared with the ordinary smooth surface, σ R The larger the value is, the better the scattering effect is, and the elevation angle of the scattering wave is defined as The calculation formula of the scattering coefficient is:

[0035]

[0036] In the formula, D represents the scattering coefficient, L i represents the sound pressure level value of the far field in different directions, M represents the total number of selected angles, and i represents the selected direction.

[0037] The advantages of the present application are:

[0038] The present application shortens the depth of the acoustic coding metasurface structure by changing the Helmholtz cavity from the traditional vertical discharge to the horizontal parallel discharge, increases the sound path difference by adding a rectangular strip inside the acoustic coding metasurface structure, further reduces the size, and achieves the multi-angle incidence wide-band scattering effect through the optimization algorithm arrangement for the purpose of wide-band multi-angle scattering, and has the advantages of wide frequency band, multiple angles and easy application.

[0039] Additional aspects and advantages of the present application will be partially given in the following description, partially will become obvious from the following description, or will be understood through the practice of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0040] The above and / or additional aspects and advantages of the present application will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings, in which:

[0041] Figure 1 The present application provides four kinds of element structure diagrams of the acoustic coding metasurface structure uniformly scattered under wide-band arbitrary angle incidence;

[0042] Figure 2 The present application provides a schematic diagram of the hard sound wave reflection matrix, the upper rectangular strip, the middle rectangular strip and the end rectangular strip in the element structure;

[0043] Figure 3 The present application provides a schematic diagram of the size of the reference numeral; Figure 2

[0044] Figure 4 The present application provides a phase response schematic diagram of the four kinds of element structures at f=4000Hz-8000Hz;

[0045] Figure 5 The present application provides a finite element software simulation element structure phase response schematic diagram of the four kinds of element structures at f=5000Hz;

[0046] Figure 6 The present application provides a phase coding arrangement schematic diagram of the four kinds of element structures;

[0047] ​Figure 7 : The flat plate and the coded metasurface scattering effect comparison schematic diagram provided by the application at the incident sound wave frequency of 4.6 kHz and 8.4 kHz and the incident sound wave angle of 0°;

[0048] Figure 8 : The flat plate and the coded metasurface scattering effect comparison schematic diagram provided by the application at the incident sound wave frequency of 4.2 kHz and 5.7 kHz and the incident sound wave angle of 30°;

[0049] Figure 9 : The flat plate and the coded metasurface scattering effect comparison schematic diagram provided by the application at the incident sound wave frequency of 4.6 kHz and 6.3 kHz and the incident sound wave angle of 45°;

[0050] Figure 10 : The flat plate and the coded metasurface scattering effect comparison schematic diagram provided by the application at the incident sound wave frequency of 4.7 kHz and 6 kHz and the incident sound wave angle of 60°;

[0051] Figure 11 : The flat plate and the coded metasurface scattering coefficient comparison schematic diagram provided by the application at the frequency of 4000 Hz-10000 Hz and the incident sound wave angle of 0°;

[0052] Figure 12 : The flat plate and the coded metasurface scattering coefficient comparison schematic diagram provided by the application at the frequency of 4000 Hz-10000 Hz and the incident sound wave angle of 30°;

[0053] Figure 13 : The flat plate and the coded metasurface scattering coefficient comparison schematic diagram provided by the application at the frequency of 4000 Hz-10000 Hz and the incident sound wave angle of 45°;

[0054] Figure 14 : The flat plate and the coded metasurface scattering coefficient comparison schematic diagram provided by the application at the frequency of 4000 Hz-10000 Hz and the incident sound wave angle of 60°;

[0055] In the figure: 10-primitive structure; 20-rectangular strip group; 21-upper rectangular strip; 22-middle rectangular strip; 23-end rectangular strip; 30-hard sound wave reflection matrix. DETAILED DESCRIPTION

[0056] The embodiments of the application are described in detail below, which are exemplary and are intended to explain the application, and cannot be understood as a limitation of the application.

[0057] Please refer to Figure 1The embodiment of the present application provides a uniform scattering acoustic coding metasurface structure under wideband arbitrary angle incidence, which comprises four kinds of unit structures, a hard sound wave reflection matrix for vertically placing the unit structures, and the four kinds of unit structures are arranged based on directivity function coding; each unit structure comprises a Helmholtz cavity and a rectangular strip group, and the Helmholtz cavity is arranged in a horizontal row and parallel to the rectangular strip group.

[0058] The Helmholtz cavity of the embodiment of the present application is changed from the traditional vertical row discharge to the horizontal row parallel discharge, so that the longitudinal depth of the structure is shortened; the sound path difference is increased by adding the rectangular strip group in the Helmholtz cavity, and the structure size is further reduced.

[0059] In the two-dimensional structure and the three-dimensional structure with the same cross section as the two-dimensional structure, the propagation characteristics of the sound wave propagation are the same, so the cross section and the two-dimensional design of the unit structure in the acoustic coding metasurface structure are as follows:

[0060] The size of the upper rectangular strip of the embodiment of the present application is that the length is 17 mm and the width is 1 mm, the long side of which is parallel to the sound wave reflection matrix; the size of the middle rectangular strip is that the length is 5 mm and the width is 1 mm, and the middle rectangular strip is placed vertically to the center of the upper rectangular strip, and the short side of which is parallel to the sound wave reflection matrix; the size of the end rectangular strip is that the length is 4 mm and the width is 1 mm, and the short side of which is parallel to the sound wave reflection matrix, and the size of the sound wave reflection matrix is that the length is 23*6 mm and the thickness is 10 mm.

[0061] The rectangular strip group of the embodiment of the present application comprises an upper rectangular strip, a middle position rectangular strip, a middle rectangular strip and an end rectangular strip; further, the number of the end rectangular strips and the distance between the end rectangular strips are adjusted corresponding to different frequency ranges, so as to adjust the phase response of the unit structure, and the phase response difference of the multiple unit structures is π / 2 under f=4000Hz-8000Hz.

[0062] The rectangular strip group of the embodiment of the present application is attached to the hard sound wave reflection matrix, and the upper part and the middle part of the hard sound wave reflection matrix correspond to the attachment of the upper rectangular strip, the middle position rectangular strip and the middle rectangular strip; the upper rectangular strip and the middle position rectangular strip are perpendicular and form a T-shaped structure (the long side of the middle position rectangular strip is placed vertically to the center of the upper rectangular strip, the short side is parallel to the sound wave reflection matrix, and the two form a T-shaped structure), and the middle rectangular strip is divided into two groups and is arranged vertically to the upper rectangular strip and parallel to the middle position rectangular strip; multiple middle rectangular strips are located on both sides of the middle position rectangular strip, and the end rectangular strip is located at both ends of the long side of the sound wave reflection matrix.

[0063] Further, the embodiment of the present application is pasted between the rectangular strip groups of the hard sound wave reflection base body to form the effect of the Helmholtz cavity and the labyrinth structure, the rectangular strips in the middle position and the middle rectangular strips are fixed to form a mountain-like structure; among the various primitive structures, the number and pasting position of the rectangular strips in the middle position of the hard sound wave reflection base body are different.

[0064] Please continue to refer to Figure 1 The primitive structure of the embodiment of the present application is four kinds, and the number of each kind of primitive structure is nine; after the 36 primitive structures are encoded and arranged based on the directivity function, they are arranged perpendicular to the hard sound wave reflection base body, and the arrangement mode is as shown in Figure 6 The four colors blue, red, orange and green correspond to the four kinds of primitive structures with phases from small to large. The encoding of the embodiment of the present application is based on the premise that the scattering effect of the far-field scattering amplitude is the best under wideband multi-angle incidence, and the arrangement is obtained by using an optimization algorithm.

[0065] Further, please refer to Figure 6 The primitive structure of the embodiment of the present application has four kinds, which are divided into: first primitive structure, second primitive structure, third primitive structure and fourth primitive structure according to the phase from small to large; in the uniformly scattered acoustic coding metasurface structure under wideband arbitrary angle incidence. The embodiment of the present application encodes four kinds of primitives by directivity function, and arranges 36 primitives according to the encoding result and perpendicular to the sound wave reflection base body, which can realize the effect of uniform scattering under multi-angle incidence under wideband conditions. Preferably, the arrangement mode of the primitive structure of the embodiment of the present application is: first primitive structure, second primitive structure, second primitive structure, second primitive structure, first primitive structure, third primitive structure, first primitive structure, fourth primitive structure, fourth primitive structure, first primitive structure, fourth primitive structure, fourth primitive structure, third primitive structure, fourth primitive structure, second primitive structure, first primitive structure, second primitive structure, third primitive structure, third primitive structure, second primitive structure, first primitive structure, fourth primitive structure, third primitive structure, second primitive structure, fourth primitive structure, first primitive structure, third primitive structure, third primitive structure, third primitive structure, fourth primitive structure, first primitive structure, third primitive structure, third primitive structure, fourth primitive structure, first primitive structure, third primitive structure. The embodiment of the present application designs the simple structure of the primitive structure, so that the phase response of the four kinds of primitive structures in a wider frequency band is 2^2 discrete gradient distribution in 2π period, and the sound wave reflection phase difference is π / 2.

[0066] In actual application, the size of the primitive structure of the embodiment of the present application is set to one tenth to one fifth of the required sound wave wavelength, and the acoustic coding metasurface action range is: 4000Hz-8000Hz, corresponding to the wavelength in air sound of 42mm-85mm; please refer toFigure 3 In the rectangular strip group of the embodiment of the present application, the width of the upper rectangular strip is 17 mm, and the thickness is 1 mm; the height of the middle position rectangular strip is 5 mm, and the width is 1 mm; the height of the middle rectangular strip is 4 mm, and the width is 1 mm; the height of the end rectangular strip is 6 mm, and the width is 1 mm; the length of the hard acoustic wave reflection base body is 23 mm, the width is 36 mm, and the thickness is 10 mm, and the hard acoustic wave reflection base body has the same cross-sectional dimension.

[0067] Preferably, the rectangular strip group and the hard acoustic wave reflection base body of the embodiment of the present application are made of aluminum material; the density of the rectangular strip group and the hard acoustic wave reflection base body is 2.7 g / m 3 , the Young's modulus is 70 GpPa, and the acoustic velocity is 6300 m / s. The acoustic coding metasurface structure uniformly scatters under wideband arbitrary angle incidence, and the frequency of the sound wave is controlled to be f = 4000 Hz-8000 Hz, and the sound wave is incident at multiple angles, so that the reflected wave is uniformly scattered.

[0068] Please continue to refer to Figure 1 and Figure 2 The side and the bottom of the unit structure of the embodiment of the present application are perpendicular; the unit structures are closely arranged in alignment, and the bottom is perpendicular to the side of the hard acoustic wave reflection base body.

[0069] The directivity function of the embodiment of the present application includes the angle and the frequency of the incident sound wave, the angle and the frequency are known quantities, and the phase information of the coding arrangement is an unknown quantity; the angle is 0°, 30°, 45°, 60° and 70°, and the frequency is 4 kHz-8 kHz; the directivity function is taken as the objective function and is maximized, and the surface of the hard acoustic wave reflection base body is divided into 36 blocks, and the data of each unit structure is 9 as a constraint function, and the multiple unit structures are temporarily placed on the surface of the hard acoustic wave reflection base body according to the unknown arrangement, and the optimal coding arrangement of the multiple unit structures is obtained by using the directivity function.

[0070] Specifically, the above-mentioned directivity function of the embodiment of the present application includes:

[0071]

[0072] In the formula, θ represents the scattering wave elevation angle, represents the scattering wave azimuth angle, θ i represents the incident sound wave elevation angle, represents the incident sound wave azimuth angle, represents the directivity function of the scattering wave, represents the far-field scattering amplitude, represents the directivity function of the coding metasurface, represents the directivity function of the smooth surface of the same size without structure, and σ Rσ represents the diffusivity of the coded metasurface compared with the normal smooth surface R The greater the value is, the better the scattering effect is, and the elevation angle of the scattering wave is defined as The calculation formula of the scattering coefficient is:

[0073]

[0074] In the formula, D represents the scattering coefficient, L represents the sound pressure level of the far field in different directions, M represents the total number of selected angles, and i represents the selected direction. i The greater the value is, the better the scattering effect is, and the elevation angle of the scattering wave is defined as

[0075] The embodiment of the present application expresses the far field scattering amplitude based on the array theory, wherein: θ represents the scattering wave elevation angle, represents the scattering wave azimuth angle, θ represents the incident wave elevation angle, i represents the incident wave azimuth angle, represents the incident wave azimuth angle, is a mode function of an element, which can be ignored in the calculation process, is an array mode. It is assumed that the acoustic coded metasurface structure is composed of an array containing N x ×N y elements, and the size is Λ. Φ(n, m) is Φ 00 , Φ 01 , Φ 10 , Φ 11 , which represents the reflection phase of the four kinds of element structures, and the four kinds of element structures are randomly arranged to obtain uniform scattering effect. The expression is:

[0076]

[0077]

[0078]

[0079] On the basis of the above calculation, the directivity function is introduced in the embodiment of the present application, specifically, the directivity function of the embodiment of the present application contains the angle and frequency of the incident sound wave, the angle and the frequency are known quantities, the angle is 0°, 30°, 45°, 60°, 70°, and the frequency is 4kHz-8kHz; and the phase information of the coded arrangement is an unknown quantity. The directivity function of the embodiment of the present application expresses the scattering effect of the far field sound wave, and the greater the value is, the better the scattering effect is. The embodiment of the present application takes the directivity function as the objective function and makes it maximum, divides the surface into 36 blocks on average, the number of each element structure is 9, temporarily places the four kinds of element structures on the surface according to the unknown arrangement, and obtains the optimal arrangement of the four kinds of elements by using the optimization algorithm, that is, obtains the phase information of the coded arrangement as shown in Figure 4 .

[0080] In combinationFigure 4 , the elevation angle of the scattered wave is defined as In the following formula represents the directivity function of the coded metasurface, represents the directivity function of the smooth surface without structure of the same size, and σ R represents the diffusion performance of the coded metasurface compared with the ordinary smooth surface, and the greater the value, the better the scattering effect.

[0081]

[0082]

[0083] According to the coded unit structure obtained according to the above formula, the scattering effect is obtained by simulation according to the coding arrangement, as shown in FIG. 2, wherein: from FIG. 2a, it can be seen that when the incident sound wave angle is 0°, the scattering coefficient of the coded metasurface structure is improved; from FIG. 2b, it can be seen that when the incident sound wave angle is 30°, the scattering coefficient of the coded metasurface structure is improved; from FIG. 2c, it can be seen that when the incident sound wave angle is 45°, the scattering coefficient of the coded metasurface structure is improved; and from FIG. 2d, it can be seen that when the incident sound wave angle is 60°, the scattering coefficient of the coded metasurface structure is improved. Figures 7-14 Figure 11 Figure 12 Figure 13 Figure 14

[0084] In addition, the scattering coefficient is introduced in the embodiment of the application, and the calculation formula of the scattering coefficient is as follows:

[0085]

[0086] In the formula, L i represents the sound pressure level value of the far field in different directions, and M represents the total number of selected angles.

[0087] The size of the scattering coefficient in the embodiment of the application reflects the uniformity of the scattered sound field energy, and a high scattering coefficient indicates that the sound energy is more uniformly scattered in different directions. On the contrary, if all the energy is reflected to one direction by mirroring, the reflection coefficient is 0. In the simulation, the sound pressure level values are selected by taking an angle interval of 2°, and M is 90.

[0088] In combination with the above-mentioned uniform scattering acoustic coded metasurface structure under wideband arbitrary angle incidence according to the embodiment of the application, the following embodiments 1-4 are provided:

[0089] Embodiment 1: When the sound wave frequency f is 4.6 kHz and 8.4 kHz, the background medium is air, the sound wave is perpendicular to the metasurface, and the metasurface structure parameters and arrangement are calculated by the directivity function and the optimization algorithm, and the simulation calculation is performed by using COMSOL Multiphysics software.​​​​​Figure 7 Fig. 3 is a schematic diagram of the scattering effect comparison between the flat plate and the coded metasurface according to the embodiment when the incident sound wave frequency is 4.6 kHz and 8.4 kHz, and the incident sound wave angle is 0°, wherein the blue line is the sound pressure level radiation pattern of the external field of the metasurface structure, and the green line is the sound pressure level radiation pattern of the external field of the flat plate structure. Figure 6 It can be seen that the acoustic coded metasurface structure of the embodiment 1 scatters the vertically incident sound wave uniformly. Figure 6 The four colors correspond to the four primitive structures respectively. Figure 1 The four colors of blue, red, orange and green correspond to the four primitives with small to large phases respectively. Therefore, the acoustic coded metasurface structure uniformly scatters sound waves under wideband and arbitrary angle incidence according to the embodiment, and the phase of the reflecting surface is changed by the simple structure and the arrangement to realize the control of the reflected sound wave angle.

[0090] Embodiment 2: When the sound wave frequency f is 4.6 kHz and 8.4 kHz, the background medium is air, the sound wave is perpendicular to the metasurface, the metasurface structure parameters and arrangement are calculated by the directivity function and the optimization algorithm, and the simulation calculation is performed by using the COMSOL Multiphysics software. Figure 8 Fig. 4 is a schematic diagram of the scattering effect comparison between the flat plate and the coded metasurface according to the embodiment 3 when the incident sound wave frequency is 4.6 kHz and 6.3 kHz, and the incident sound wave angle is 30°, wherein the blue line is the sound pressure level radiation pattern of the external field of the metasurface structure, and the green line is the sound pressure level radiation pattern of the external field of the flat plate structure. Figure 8 It can be seen that the acoustic coded metasurface structure of the embodiment 2 scatters the sound wave with the incident sound wave angle of 30° uniformly. Therefore, the acoustic coded metasurface structure uniformly scatters sound waves under wideband and arbitrary angle incidence according to the embodiment, and the phase of the reflecting surface is changed by the simple structure and the arrangement to realize the control of the reflected sound wave angle.

[0091] Embodiment 3: When the sound wave frequency f is 4.6 kHz and 6.3 kHz, the background medium is air, the sound wave is perpendicular to the metasurface, the metasurface structure parameters and arrangement are calculated by the directivity function and the optimization algorithm, and the simulation calculation is performed by using the COMSOL Multiphysics software. Figure 9 Fig. 4 is a schematic diagram of the scattering effect comparison between the flat plate and the coded metasurface according to the embodiment 3 when the incident sound wave frequency is 4.6 kHz and 6.3 kHz, and the incident sound wave angle is 30°, wherein the blue line is the sound pressure level radiation pattern of the external field of the metasurface structure, and the green line is the sound pressure level radiation pattern of the external field of the flat plate structure. Figure 9It can be seen that the acoustic coding metasurface structure of embodiment 3 scatters the sound wave with an incident angle of 45° evenly. Therefore, the acoustic coding metasurface structure of the embodiment of the present application can scatter sound waves evenly under wideband and arbitrary angle incidence, and the phase of the reflecting surface is changed by a simple structure and arrangement to realize the regulation of the reflected sound wave angle.

[0092] In embodiment 4, when the frequency of the sound wave is f=4.7 kHz and 6 kHz, the background medium is air, the sound wave is perpendicular to the metasurface, the structure parameters and arrangement of the metasurface are calculated by the directivity function and the optimization algorithm, and the simulation calculation is performed by using COMSOL Multiphysics software. Figure 10 FIG. 4 is a schematic diagram of the scattering effect comparison between the flat plate and the coding metasurface in embodiment 4 when the incident sound wave frequency is 4.7 kHz and 6 kHz and the incident sound wave angle is 60°. The blue line is the sound pressure level radiation pattern of the external field of the metasurface structure, and the green line is the sound pressure level radiation pattern of the external field of the flat plate structure. It can be seen that the acoustic coding metasurface structure of embodiment 4 scatters the sound wave with an incident angle of 60° evenly. Figure 10 It can be seen that the acoustic coding metasurface structure of embodiment 4 scatters the sound wave with an incident angle of 60° evenly. Therefore, the acoustic coding metasurface structure of the embodiment of the present application can scatter sound waves evenly under wideband and arbitrary angle incidence, and the phase of the reflecting surface is changed by a simple structure and arrangement to realize the regulation of the reflected sound wave angle.

[0093] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can easily think of various equivalent modifications or replacements within the technical range disclosed by the present application, and these modifications or replacements should be covered within the protection scope of the present application.

Claims

1. A uniform scattering acoustic coding metasurface structure under wideband arbitrary angle incidence, characterized in that, The application relates to an acoustic coding metasurface structure, which comprises the following: A plurality of basic structures, a hard sound wave reflection matrix for vertically placing the basic structures, and a plurality of the basic structures are arranged based on a directivity function; Each of the basic structures comprises a Helmholtz cavity and a rectangular strip group, and the Helmholtz cavities are arranged in a transverse parallel mode; The rectangular strip group is vertically added to the inside of the Helmholtz cavity to form the basic structure, and the rectangular strip group is used for increasing a sound path difference; In a two-dimensional structure and a three-dimensional structure with the same cross section as the two-dimensional structure, the propagation characteristics of sound wave propagation are the same, so the cross section and two-dimensional design of the basic structure in the acoustic coding metasurface structure are as follows: Each of the basic structures is placed perpendicularly to the long side of the hard sound wave reflection matrix, the rectangular strip group comprises upper rectangular strips, middle position rectangular strips, middle rectangular strips and end rectangular strips, the long side of the upper rectangular strips is placed in parallel to the sound wave reflection matrix, the long side of the middle position rectangular strips is placed perpendicularly to the center of the upper rectangular strips and the short side is placed in parallel to the sound wave reflection matrix, and the two form a T-shaped structure; the middle rectangular strips are divided into two groups and arranged perpendicularly to the upper rectangular strips and in parallel to the middle position rectangular strips, a plurality of the middle rectangular strips are located on both sides of the middle position rectangular strips, and the end rectangular strips are located at both ends of the long side of the sound wave reflection matrix; The rectangular strip group is attached to the hard sound wave reflection matrix to form the effect of the joint action of the Helmholtz cavity and the labyrinth structure, and the middle position rectangular strips and the middle rectangular strips are fixed to form a mountain-like structure; In the plurality of basic structures, the number and attachment positions of the rectangular strips located at the middle positions of the hard sound wave reflection matrix are different.

2. The uniform scattering acoustic coding metasurface structure under wideband arbitrary angle incidence according to claim 1, characterized in that, Corresponding to different frequency ranges, the number of the end rectangular bars and the distance between the end rectangular bars are adjusted, and then the phase response of the unit structure is adjusted, so that a plurality of the unit structures can be used in The phase response difference is .

3. The uniform scattering acoustic coding metasurface structure according to claim 2, wherein, The basic structures are four kinds, and the number of each of the basic structures is nine; After the 36 basic structures are arranged based on the directivity function, the basic structures are arranged perpendicularly to the hard sound wave reflection matrix.

4. The uniform scattering acoustic coding metasurface structure under wideband arbitrary angle incidence of claim 1, wherein, The size of the basic structure is set to be 1 / 10-1 / 5 of the required sound wave wavelength, and the action range of the acoustic coding metasurface is 4000Hz-8000Hz, corresponding to the wavelength of 42mm-85mm in air sound; The size of a single basic structure is set to be 23mm in width and 6mm in thickness, and the thickness is 1 / 10-1 / 5 of the corresponding wavelength of the action frequency; In the rectangular strip group, the width of the upper rectangular strip is 17mm, the thickness is 1mm, the height of the middle position rectangular strip is 5mm, the width is 1mm, the height of the middle rectangular strip is 4mm, the width is 1mm, and the height of the end rectangular strip is 6mm, the width is 1mm; The length of the hard sound wave reflection matrix is 23mm, the width is 6mm, and the thickness is 10mm, and the hard sound wave reflection matrix has the same cross section size.

5. The uniform scattering acoustic coding metasurface structure of claim 1, wherein, The basic structures are four kinds, and the phases are divided into a first basic structure, a second basic structure, a third basic structure and a fourth basic structure from small to large; In the acoustic coding metasurface structure which uniformly scatters sound waves under wide frequency and arbitrary angle incidence, the arrangement mode of the basic structure is as follows: the first basic structure, the second basic structure, the second basic structure, the second basic structure, the first basic structure, the third basic structure, the first basic structure, the fourth basic structure, the fourth basic structure, the first basic structure, the fourth basic structure, the fourth basic structure, the third basic structure, the fourth basic structure, the second basic structure, the first basic structure, the second basic structure, the third basic structure, the third basic structure, the second basic structure, the first basic structure, the fourth basic structure, the third basic structure, the second basic structure, the fourth basic structure, the first basic structure, the third basic structure, the third basic structure, the third basic structure, the fourth basic structure, the first basic structure, the third basic structure, the third basic structure, the fourth basic structure, the first basic structure, the third basic structure.

6. The uniform scattering acoustic coding metasurface structure of claim 1, wherein, the side of the basic structure is perpendicular to the bottom thereof; the basic structures are closely arranged in alignment respectively, and are perpendicular to the bottom and parallel to the side of the hard acoustic wave reflecting matrix.

7. The uniform scattering acoustic coding metasurface structure of claim 1, wherein, the rectangular strip group and the hard acoustic wave reflecting matrix are made of aluminum material; The density of the rectangular bar group and the hard acoustic wave reflection matrix is 2.7g / m 3 The Young's modulus is 70GpPa, and the acoustic velocity is 6300m / s.

8. The uniform scattering acoustic coding metasurface structure according to claim 1 or 5, characterized in that, The acoustic coding metasurface structure uniformly scatters sound waves under broadband arbitrary angle incidence The frequency and multi-angle incident sound waves are regulated to make the reflected waves uniformly scattered.

9. The uniform scattering acoustic coding metasurface structure of claim 1, wherein, the directivity function includes the angle and frequency of incident acoustic wave, the angle and frequency are known quantities, and the phase information of the coded arrangement is an unknown quantity; the angle is 0°, 30°, 45°, 60°, 70°, and the frequency is 4kHz-8kHz; the directivity function is taken as a target function and is maximized, and the surface of the hard acoustic wave reflecting matrix is divided into 36 blocks, and the data of each basic structure is 9 as a constraint function; a plurality of basic structures are temporarily placed on the surface of the hard acoustic wave reflecting matrix in unknown arrangement, and the optimal coded arrangement of the plurality of basic structures is obtained by using the directivity function.

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