Abnormal sound wave transmission device and method

Abstract

The present invention discloses a device and method for abnormal acoustic wave transmission, comprising a meta-acoustic grating structure and a two-dimensional waveguide. The two-dimensional waveguide is composed of two parallel plates spaced a certain distance apart. The meta-acoustic grating structure is disposed between the two parallel plates of the two-dimensional waveguide. The meta-acoustic grating structure comprises at least three side-open Helmholtz resonant cavity units, which are arranged sequentially and continuously. Each side-open Helmholtz resonant cavity unit comprises several open resonant cavities, the sides of which are sequentially connected. A thin plate parallel to the bottom surface of each open resonant cavity is disposed within the open resonant cavity. The transmission phase can be controlled by adjusting the height of the thin plate, thereby achieving control of abnormal acoustic wave transmission under different incident angles using the same structure. By utilizing a simple structure to control acoustic wave transmission characteristics, the numerous unit structures required for the phase gradient metasurface are avoided, resulting in miniaturization and simplification of the beam abnormal transmission control device.

Description

Technical Field

[0001] The present invention belongs to the technical field of acoustic metasurfaces, and in particular to a device and method for abnormal transmission of acoustic waves. Background Art

[0002] In recent years, the use of artificial microstructures to manipulate wave propagation has garnered considerable research interest. Metasurfaces, using subwavelength-thick unit cells, can arbitrarily manipulate wavefront amplitude and phase. By utilizing folded structures, Helmholtz resonators, and membrane-like structures, they can achieve phenomena unattainable with natural materials. Metasurfaces offer a new degree of freedom in manipulating acoustic wavefronts, with potential applications in sound absorption, stealth, and superlenses.

[0003] In numerous previous studies, wavefront manipulation of acoustic waves was mostly based on the generalized Snell's law. When the phase of the designed metasurface covers a phase distribution from 0 to 2π, the desired phase can be appropriately introduced along the surface according to different beam steering requirements, thereby controlling the propagation direction of the beam. However, due to impedance mismatch, the efficiency of metasurfaces based on phase gradients is limited. The coupling effect between complex and numerous structural units also limits work efficiency. In addition, the design of metasurfaces based on this principle requires multiple structural units to be arranged on a subwavelength scale, which is not conducive to structural simplification. To overcome the control limitations, a single metaacoustic grating that directly operates at high diffraction orders (usually positive and negative orders 1) has come into being. Metaacoustic gratings control beam transmission mainly by finding a suitable resonant unit structure. Through the coupling effect between units, the incident beam can be directly guided to the desired diffraction order direction. No linear gradient phase distribution is required, providing a simpler and more effective method for wavefront morphology control and beam transmission. Based on this, some research works have explored the application of meta-gratings in acoustic beam control, but most of these works focus on single-angle control, with a single beam direction, which limits their practical application scenarios. In addition, most previous research works have explored oblique incident beams working directly at high diffraction orders, and there has been less research on controlling vertical incident beams. When the sound wave is incident vertically, more diffraction orders will inevitably be generated, making actual control more complex, but more widely used in practical applications. Therefore, how to achieve a multi-angle incident acoustic wave abnormal transmission control (especially for vertical incident beams) is crucial. Summary of the Invention

[0004] The purpose of the present invention is to solve the problems in the prior art and provide a device and method for abnormal transmission of sound waves, which realizes abnormal transmission behavior under multiple incident angles under the same structure based on a meta-acoustic grating.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A device for abnormal transmission of sound waves comprises a metaacoustic grating structure and a two-dimensional waveguide, wherein the two-dimensional waveguide is two parallel plates with a certain distance between them, and the metaacoustic grating structure is arranged between the two parallel plates of the two-dimensional waveguide. The metaacoustic grating structure comprises at least three side-open Helmholtz resonance cavity units, which are arranged in sequence and continuously. Each side-open Helmholtz resonance cavity unit comprises a plurality of open resonance cavities, the side surfaces of the open resonance cavities are connected in sequence, and a thin plate parallel to the bottom surface of the open resonance cavity is arranged in the open resonance cavity.

[0007] Furthermore, baffles are provided at both ends of the open resonant cavity.

[0008] Furthermore, an opening is provided on the top of the open resonant cavity, and the opening is a slit parallel to the side surface of the open resonant cavity.

[0009] Furthermore, the height of the thin plate in the open resonant cavity from the bottom surface of the open resonant cavity is adjustable.

[0010] Furthermore, the heights of the plurality of thin plates in each of the side-open Helmholtz resonant cavity units from the bottom surface of the open resonant cavity are the same.

[0011] Furthermore, the heights of the thin plates in different side-open Helmholtz resonant cavity units from the bottom surface of the open resonant cavity are different.

[0012] Furthermore, the two-dimensional waveguide is two hard glass plates or acrylic plates.

[0013] Furthermore, the metaacoustic grating structure is a 3D printed structure, and the material of the metaacoustic grating structure is polylactic acid material, resin material or ABS plastic material.

[0014] A method for abnormal transmission of acoustic waves based on the device, comprising:

[0015] Determine the acoustic grating constant according to the wavelength and operating frequency of the sound wave;

[0016] The number of side-open Helmholtz resonant cavity units and the number of open resonant cavities are determined according to the grating constant to form a meta-acoustic grating structure, and the meta-acoustic grating structure is placed in a two-dimensional waveguide;

[0017] The height of the thin plate inside the open resonant cavity is adjusted to control the phase of sound wave transmission.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The present invention provides a device for anomalous acoustic wave transmission. This device employs a meta-grating structure composed of a series of side-open Helmholtz resonant cavity units placed within a two-dimensional waveguide. By rationally designing the grating constant and wavelength of the meta-grating structure, only 0th, +1st, and -1st order diffraction can be present in the diffracted acoustic field. Phase manipulation by the side-open Helmholtz resonant cavity units can minimize the number of unnecessary diffraction orders while retaining specific diffraction orders, achieving anomalous beam control. A thin plate parallel to the bottom surface is provided within the open resonant cavity of the side-open Helmholtz resonant cavity unit. Adjusting the height of the thin plate allows for anomalous acoustic wave transmission control at different incident angles within the same structure. By utilizing a simple structure to control acoustic wave transmission characteristics, the numerous unit structures required for phase-gradient metasurfaces are avoided, resulting in a miniaturized and simplified device for anomalous beam transmission control. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0021] Figure 1 It is a structural schematic diagram of the abnormal sound wave transmission device of the present invention.

[0022] Figure 2 Schematic diagram of the structure of the open resonant cavity in the abnormal sound wave transmission device of the present invention.

[0023] Figure 3 This is a simulation diagram of the normalized proportion of diffraction orders in the transmitted sound wave of Example 1 of the present invention.

[0024] Figure 4 This is a diagram of the transmitted sound pressure at the working frequency of Example 1 of the present invention.

[0025] Figure 5 This is a real-life example of Example 1 of the present invention.

[0026] Figure 6 This is a diagram showing the experimental results of Example 1 of the present invention tested in a two-dimensional waveguide.

[0027] Figure 7 Graphs of transmitted sound pressure at different incident angles according to Example 1 of the present invention are shown.

[0028] Figure 8 This is a diagram of the transmitted sound pressure at the working frequency of Example 2 of the present invention.

[0029] Figure 9 Graphs of transmitted sound pressure at different incident angles at the operating frequency of Example 2 of the present invention.

[0030] Figure 10 This is a diagram of the transmitted sound pressure at the working frequency of Example 3 of the present invention.

[0031] Figure 11 Graphs of transmitted sound pressure at different incident angles at the operating frequency of Example 3 of the present invention.

[0032] Wherein: 1-first side-opened Helmholtz resonant cavity, 2-second side-opened Helmholtz resonant cavity, 3-third side-opened Helmholtz resonant cavity, 4-two-dimensional waveguide, 5-thin plate, 101-open resonant cavity, 102-baffle. DETAILED DESCRIPTION

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0034] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0035] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0036] In the description of the embodiments of the present invention, it should be noted that if the terms "upper," "lower," "horizontal," "inner," etc. appear, the orientation or positional relationship indicated is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the inventive product is typically placed when in use. These terms are merely for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first," "second," etc. are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0037] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0038] In the description of the embodiments of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0039] The present invention is described in further detail below with reference to the accompanying drawings:

[0040] See also Figures 1 to 11 The present invention provides an abnormal sound wave transmission device, comprising a metaacoustic grating structure and a two-dimensional waveguide 4. The two-dimensional waveguide 4 is composed of two hard glass plates or acrylic plates, with a certain thickness between the two plates. The size of the waveguide is adjustable according to the operating wavelength and the size of the metaacoustic grating structure. The metaacoustic grating structure includes at least three independent side-open Helmholtz resonant cavity units arranged periodically and continuously along the y direction. The side-open Helmholtz resonant cavity units are composed of a plurality of open resonant cavities 101 arranged along the x direction and baffles 102 on the left and right sides. The baffles 102 seal the cavity of the open resonant cavity 101. The use of a plurality of open resonant cavities 101 can ensure that the phase has a sufficient control range. Each open resonant cavity 101 has an opening on its upper surface and a thin plate 5 with adjustable height inside. The difference between the three side-open Helmholtz resonant cavity units lies in the height of the thin plate 5 from the bottom surface of the open resonant cavity 101. The heights of the thin plates 5 from the bottom surface of the open resonant cavity 101 in the three side-open Helmholtz resonant cavity units are different. The sound wave characteristics of the working frequency band can be controlled by changing the height of the thin plates 5 in the open resonant cavity 101.

[0041] When an acoustic wave is incident on a transmissive metaacoustic grating structure at an angle of incidence θ, the refractive indices of the media above and below the metaacoustic grating are n1 and n2, respectively. When the wavelength of the acoustic wave is sufficiently short compared to the grating constant, one or more diffraction orders may occur. The condition for generating a diffracted acoustic wave of a certain order is that the acoustic waves along the two paths produce constructive interference, satisfying:

[0042] mλ=d(n2sinγ m -n1sinθ)(m=0,±1,±2,......)

[0043] Where: the wavelength of the sound wave is λ, the grating constant is d, m is the diffraction order, γ m is the diffraction angle of the m-order diffracted sound wave.

[0044] When the incident angle θ = 0°, the diffracted sound wave does not have second-order and higher-order diffraction orders and needs to satisfy the formula: When the working wavelength and the acoustic grating constant are reasonably designed, only the 0th, +1st, and -1st order diffractions can exist in the diffraction sound field. To achieve the efficient extraordinary transmission behavior of only retaining the negative first order, at least three off-centered Helmholtz resonance cavity units are required within one acoustic grating period. The off-centered Helmholtz resonance cavity units can regulate the sound waves to eliminate the unwanted diffraction orders as much as possible, retain the specific diffraction orders, and achieve the efficient extraordinary regulation behavior.

[0045] The acoustic grating constant refers to the length of the metasurface acoustic grating structure along the y-direction within one period. According to the working frequency, the acoustic grating constant d is designed to satisfy: Select an appropriate number of off-centered Helmholtz resonance cavity units within one period according to the actual situation. For the regulation of sound waves with an incident angle θ = 0°, at least 3 off-centered Helmholtz resonance cavity units are required. To achieve the wide-angle operation of the metasurface acoustic grating structure, three off-centered Helmholtz resonance cavity units are selected in this invention. Each off-centered Helmholtz resonance cavity unit consists of several open resonators 101 arranged along the x-direction. The number of open resonators 101 can be determined according to the phase modulation situation. By optimizing the height of the thin plate 5 inside the open resonator 101, the negative first order diffracted sound waves can be obtained. The metasurface acoustic grating structure is prepared by 3D printing technology. The materials can be polylactic acid materials, resin materials, ABS plastics, etc. The fabricated metasurface acoustic grating structures are arranged periodically along the y-direction in a two-dimensional waveguide for experiments.

[0046] Example 1:

[0047] The working frequency of the sound wave is 1720 Hz, and it can be obtained that 199.5 mm < d < 399 mm. The metasurface acoustic grating structure is three off-centered Helmholtz resonance cavity units. The length of the off-centered Helmholtz resonance cavity unit is 90 mm, and the height is 35.6 mm. At this time, the acoustic grating constant d is 270 mm. Each off-centered Helmholtz resonance cavity unit consists of 5 open resonators 101 arranged along the x-direction and is closed with baffles with a thickness of 5 mm on both the left and right sides. The internal structure of a single off-centered Helmholtz resonance cavity unit is as Figure 2As shown, it is composed of 5 open resonant cavities 101, each of which has an opening with a width of 3 mm on the upper surface. The side wall thickness and bottom wall thickness of the open resonant cavity 101 are both 3.6 mm, and the upper wall thickness of the open resonant cavity 101 is 2 mm. Each open resonant cavity 101 has a thin plate 5 with an adjustable thickness of 1 mm inside. The height of the thin plate 5 from the upper surface of the lower wall of the open resonant cavity 101 can be adjusted. By changing the height of the thin plate 5 in the open resonant cavity 101, the resonance characteristics of the structural unit can be changed, and the sound wave transmission phase can be modulated accordingly. When the incident angle is 0°, by optimizing the height of the thin plate 5 inside the three side-opening Helmholtz resonant cavity units and modulating the transmission phase, the 0th and +1st order diffraction waves are suppressed, leaving only the -1st order diffraction sound wave with a diffraction angle of γ-1, thus achieving efficient abnormal transmission. After optimization, the height of the thin plate 5 in the first side-opening Helmholtz resonant cavity 1 is 1mm, the height of the thin plate 5 in the second side-opening Helmholtz resonant cavity 2 is 5.5mm, and the height of the thin plate 5 in the third side-opening Helmholtz resonant cavity 3 is 19mm. According to the set geometric parameters, using three independently designed side-opening Helmholtz resonant cavity units, the transmitted sound wave can be deflected toward the specific -1st order diffraction direction when the incident angle is 0°. The simulation results of the normalized proportion of diffraction orders in the transmitted sound wave are shown as follows: Figure 3 As shown, from Figure 3 It can be seen that -1 order diffraction accounts for 80% of the transmitted sound wave, indicating that the 0th and +1st order diffraction sound waves are suppressed, and the -1st order diffraction sound wave is dominant. The distribution of its diffraction sound pressure field is as follows: Figure 4 As shown, the sound pressure field is the angle between the propagation angle and the normal line is γ -1 = -48° plane acoustic wave, which is consistent with the -1st order diffraction angle γ calculated using diffraction theory. -1 =-48°.

[0048] According to the set geometric parameters, the metaacoustic grating structure is prepared using polylactic acid material using 3D printing technology. The actual object of the open resonant cavity 101 in Example 1 is as shown in FIG. Figure 5 As shown in the figure, the prepared metaacoustic grating structure is periodically arranged along the y direction in a two-dimensional waveguide 4 with a length of 2m, a width of 1.2m and a height of 6cm for testing. The experimental results are shown in Figure 6 As shown in the figure, it can be seen that when the incident angle is 0°, the transmitted sound field of the vertically incident plane sound wave after passing through the meta-acoustic grating structure is approximately a -1 = -50°, which is consistent with the simulation results, indicating that the -1st order diffraction sound wave dominates the transmission field, and the meta-grating structure achieves abnormal transmission of vertically incident plane sound waves. When the incident angle is 0° to 29°, the transmitted sound pressure at different incident angles is as follows: Figure 7 As shown, from Figure 7It can be observed that for different incident angles of θ = 9°, θ = 15°, θ = 19° and θ = 29°, the meta-acoustic grating structure can achieve abnormal control of sound waves.

[0049] Example 2:

[0050] The superstructure acoustic grating structure consists of three side-open Helmholtz resonant cavity units with an operating frequency of 1625Hz. The side-open Helmholtz resonant cavity unit has a length of 110mm and a height of 35.6mm. At this time, the acoustic grating constant d is 330mm. Each side-open Helmholtz resonant cavity unit is composed of four open resonant cavities 101 arranged along the x-direction. The side wall thickness and bottom wall thickness of the open resonant cavity 101 are both 3.6mm, the upper wall thickness of the open resonant cavity 101 is 2mm, and the left and right sides are closed with baffles with a thickness of 2.5mm. Each open resonant cavity 101 has an opening with a width of 2.5 mm on its upper surface. The height of the thin plate 5 from the upper surface of the lower wall of the open resonant cavity 101 can be adjusted. After optimization, the height of the thin plate 5 in the first side-open Helmholtz resonant cavity 1 is 1 mm, the height of the thin plate 5 in the second side-open Helmholtz resonant cavity 2 is 7 mm, and the height of the thin plate 5 in the third side-open Helmholtz resonant cavity 3 is 27 mm. The three independent side-open Helmholtz resonant cavity units are periodically arranged along the y direction in a two-dimensional waveguide 4 with a height of 6 cm. When the incident angle is 0°, the diffracted sound pressure field distribution of a vertically incident plane sound wave passing through the meta-grating structure is as follows: Figure 8 As shown, the sound pressure field is the angle between the propagation angle and the normal line is γ -1 = -40° plane acoustic wave, which is consistent with the -1st order diffraction angle γ calculated using diffraction theory. -1 =-39.8°. When the incident angle is 0°~34°, the transmitted sound pressure at different incident angles is as follows Figure 9 As shown, from Figure 9 It can be observed that for different incident angles of θ = 14°, θ = 24° and θ = 34°, the sound pressure field of the transmitted wave is a plane sound wave deflected at different angles, and the -1 order diffraction sound wave is dominant, indicating that the meta-acoustic grating structure can achieve abnormal control of wide-angle incident sound waves.

[0051] Example 3:

[0052] The meta-acoustic grating structure consists of three side-open Helmholtz resonator units operating at a frequency of 2539 Hz. Each side-open Helmholtz resonator unit is 60 mm long and 35.6 mm high, resulting in a grating constant d of 180 mm. Each side-open Helmholtz resonator unit consists of three open resonators 101 arranged along the x-direction. The side and bottom walls of each open resonator 101 are both 3.6 mm thick, and the top wall of each open resonator 101 is 2 mm thick. The left and right sides are enclosed by 2.5 mm thick baffles. Each open resonator 101 has a 1.5 mm wide opening on its upper surface. After optimization, the height of the thin plate 5 in the first side-open Helmholtz resonator 1 is 17 mm, the height of the thin plate 5 in the second side-open Helmholtz resonator 2 is 27 mm, and the height of the thin plate 5 in the third side-open Helmholtz resonator 3 is 15 mm. The three independent side-open Helmholtz resonator units are periodically arranged along the y-direction within a two-dimensional waveguide 4 with a height of 6 cm. When the incident angle is 0°, the diffracted sound pressure field distribution of the vertically incident plane sound wave passing through the meta-grating structure is as follows: Figure 10 As shown, the sound pressure field is the angle between the propagation angle and the normal line is γ -1 = -49° plane acoustic wave, which is consistent with the -1st order diffraction angle γ calculated using diffraction theory. -1 =-48.6°. When the incident angle is 0°~19°, the transmitted sound pressure at different incident angles is as follows Figure 11 As shown, from Figure 11 It can be observed that for different incident angles of θ=7° and θ=19°, the transmitted sound wave and the incident sound wave are on the same side of the normal, and the -1 order diffraction sound wave is dominant, indicating that the meta-acoustic grating structure can achieve abnormal control of sound waves at different incident angles.

[0053] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. An abnormal sound wave transmission device, characterized in that: The invention comprises a metaacoustic grating structure and a two-dimensional waveguide (4), wherein the two-dimensional waveguide (4) is two parallel plates with a certain distance between them, and the metaacoustic grating structure is arranged between the two parallel plates of the two-dimensional waveguide (4). The metaacoustic grating structure comprises at least three side-open Helmholtz resonance cavity units, and the side-open Helmholtz resonance cavity units are arranged in sequence. The side-open Helmholtz resonance cavity units comprise a plurality of open resonance cavities (101), and the side surfaces of the open resonance cavities (101) are connected in sequence. A thin plate (5) parallel to the bottom surface of the open resonance cavity (101) is arranged in the open resonance cavity (101); The height of the thin plate (5) in the open resonant cavity (101) from the bottom surface of the open resonant cavity (101) is adjustable; The heights of the plurality of thin plates (5) in each of the side-open Helmholtz resonance cavity units from the bottom surface of the open resonance cavity (101) are the same; The heights of the thin plates (5) in different side-open Helmholtz resonant cavity units from the bottom surface of the open resonant cavity (101) are different.

2. The abnormal sound wave transmission device according to claim 1, characterized in that: Baffles (102) are provided at both ends of the open resonant cavity (101).

3. The abnormal sound wave transmission device according to claim 1, characterized in that: An opening is provided at the top of the open resonant cavity (101), and the opening is a slit parallel to the side surface of the open resonant cavity (101).

4. The abnormal sound wave transmission device according to claim 1, characterized in that: The two-dimensional waveguide (4) is two hard glass plates or acrylic plates.

5. The abnormal sound wave transmission device according to claim 1, characterized in that: The metaacoustic grating structure is a 3D printed structure, and the material of the metaacoustic grating structure is polylactic acid material, resin material or ABS plastic material.

6. A method for abnormal transmission of sound waves based on the device according to any one of claims 1 to 5, characterized in that: include: Determine the acoustic grating constant according to the wavelength and operating frequency of the sound wave; Determining the number of side-open Helmholtz resonance cavity units and the number of open resonance cavities (101) according to the grating constant to form a meta-acoustic grating structure, and placing the meta-acoustic grating structure in a two-dimensional waveguide (4); The height of the thin plate (5) inside the open resonant cavity (101) is adjusted to control the phase of the sound wave transmission.

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