CN114999437A - Asymmetric sound wave separator based on binary ultrastructural surface - Google Patents
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- CN114999437A CN114999437A CN202210513457.7A CN202210513457A CN114999437A CN 114999437 A CN114999437 A CN 114999437A CN 202210513457 A CN202210513457 A CN 202210513457A CN 114999437 A CN114999437 A CN 114999437A
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- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
- G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
- G10K11/18—Methods or devices for transmitting, conducting or directing sound
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- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
- G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
- G10K11/18—Methods or devices for transmitting, conducting or directing sound
- G10K11/26—Sound-focusing or directing, e.g. scanning
- G10K11/28—Sound-focusing or directing, e.g. scanning using reflection, e.g. parabolic reflectors
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- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
- G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
- G10K11/18—Methods or devices for transmitting, conducting or directing sound
- G10K11/26—Sound-focusing or directing, e.g. scanning
- G10K11/30—Sound-focusing or directing, e.g. scanning using refraction, e.g. acoustic lenses
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- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
- G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
- G10K11/36—Devices for manipulating acoustic surface waves
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Abstract
The invention discloses an asymmetric acoustic wave separator based on a binary super-structure surface, which comprises a first super-cell and a second super-cell which are oppositely arranged, wherein the first super-cell is provided with a first acoustic super-structure surface, the second super-cell is provided with a second acoustic super-structure surface, an air gap delta d is arranged between the first super-cell and the second super-cell, the first super-cell comprises a plurality of first cells and second cells which are alternately arranged, the second super-cell comprises a plurality of third cells and fourth cells which are alternately arranged, the third cells comprise two groups of first cells, the fourth cells comprise two groups of second cells, the phase difference between the first cells and the second cells is pi, and the phase difference between the third cells and the fourth cells is pi. The invention constructs two double-layer acoustic ultrastructural surfaces through unit cells with different periods, realizes tunable asymmetric transmission of sound waves based on the transition of a diffraction channel by adjusting an air gap, has robustness on working frequency and an incident angle, and can be applied to devices such as a passive acoustic diode and the like.
Description
Technical Field
The invention belongs to the technical field of sound wave propagation, and particularly relates to an asymmetric sound wave separator based on a binary ultrastructural surface.
Background
Asymmetric transmission allows high transmission of incident energy through the device from one direction, but no or low transmission from the other direction. Due to the fundamental importance of the one-way effect in many applications, asymmetric transmission has been extensively studied in the fields of thermal energy control, directional light transmission, mechanical wave switching, and acoustic diodes. However, large capacity, complex implementation and high loss have been obstacles to the practical implementation of asymmetric transmission devices.
Metamaterials open up new possibilities for controlling classical waves in the sub-wavelength range. In particular, in two-dimensional metamaterials, the super-surface has shown its powerful ability to control wave flow in ultra-thin planar structures. In the acoustic field, acoustic metasurfaces have proven to be good candidates for achieving asymmetric transmission effects in different systems, such as active media, near-zero index media, cylindrical waveguides and non-hermitian systems. Typically, acoustic waves are steered in an abnormal manner, and these acoustic super-surfaces are designed with phase gradients. The phase gradient is realized by a plurality of unit cells, forming a super cell that uniformly covers the 2 pi phase range. The large number of cells not only increases the complexity of the design but also leads to more unavoidable absorption in the acoustic super-surface. Furthermore, the greater number of cells can reduce the cell size of a super cell with a fixed period, which presents a significant challenge to higher frequency sample fabrication. Fortunately, some recent studies have shown that the performance of the acoustic super-surface is not sensitive to the number of cells, and fewer cells can well retain the desired phenomenon. Thus, an acoustic super-surface with a simple design can potentially be used to achieve the AT effect, so that these problems can be effectively solved.
Therefore, in view of the above technical problems, it is necessary to provide an asymmetric acoustic wave separator based on a binary metamaterial surface.
Disclosure of Invention
The invention aims to provide an asymmetric sound wave separator based on a binary ultrastructural surface.
In order to achieve the above object, an embodiment of the present invention provides the following technical solutions:
an asymmetric sound wave separator based on a binary super-structure surface comprises a first super cell and a second super cell which are oppositely arranged, wherein the first super cell is provided with a first acoustic super-structure surface, the second super cell is provided with a second acoustic super-structure surface, an air gap delta d is formed between the first super cell and the second super cell, the first super cell comprises a plurality of first cells and second cells which are alternately arranged, the second super cell comprises a plurality of third cells and fourth cells which are alternately arranged, the third cells comprise two groups of first cells, the fourth cells comprise two groups of second cells, and the heights h and the widths w of the first cells and the second cells 1 Are all equal, the phase difference is pi, the height h and the width w of the third and fourth cells 2 Are all equal, the phase difference is pi, and w 2 ＝2w 1 Period length p of the first super cell 1 And the period length p of the second super cell 2 Satisfies p 2 ＝2p 1 。
In one embodiment, the separator satisfies:
p 1 ＝2w 1 ＜λ，p 2 ＝2w 2 ＞λ，θ＝arcsin(λ/p 2 )；
where λ is the wavelength of the acoustic wave and θ is the splitting angle of the acoustic wave.
In one embodiment, the separator satisfies: Δ d >0.3 λ, h ═ 0.5 λ,
θ＝arcsin(λ/p 2 )＝45°。
in one embodiment, Δ d in the separator is 0.5 λ.
In one embodiment, the contrast η of the separator is:
η＝|E PI -E NI |/(E PI +E NI )；
wherein E is PI And E NI Respectively, positive and negative incident transmitted energy.
In one embodiment, the working frequency of the separator is 3.28 kHz-3.54 kHz, and the contrast eta is more than or equal to 0.8.
In one embodiment, the working frequency of the separator is 3.43kHz, and the wavelength λ of the sound wave is 10 cm.
In one embodiment, the first unit cell is a hollow substrate, and the second unit cell includes a hollow substrate and a plurality of partitions alternately disposed on two opposite inner walls of the substrate.
In one embodiment, the substrate and the spacer are made of acrylic acid.
Compared with the prior art, the invention has the following advantages:
the invention constructs two double-layer acoustic ultrastructural surfaces through unit cells with different periods, realizes tunable asymmetric transmission of sound waves based on the transition of a diffraction channel by adjusting an air gap, has robustness on working frequency and an incident angle, and can be applied to devices such as a passive acoustic diode and the like.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments described in the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a schematic structural diagram of an asymmetric acoustic wave separator (air gap Δ d) according to the present invention;
fig. 2 is a schematic diagram of the structure of a first unit cell and a second unit cell in an embodiment of the present invention;
FIG. 3 is a schematic structural diagram of an asymmetric acoustic wave separator (air gap 0) according to the present invention;
fig. 4a, 4c are respectively a numerical simulation field diagram of a two-layer acoustic metamaterial surface at positive and negative incidence (Δ d ═ 0.5 λ);
fig. 4b and 4d are graphs showing experimental results at positive incidence and negative incidence (Δ d ═ 0.5 λ), respectively;
fig. 4e is a far field profile of beam splitting at positive and negative incidence (Δ d ═ 0.5 λ);
fig. 5a, 5c are numerical simulation field diagrams of a two-layer acoustic metamaterial surface at normal incidence and negative incidence (Δ d ═ 0), respectively;
fig. 5b and 5d are graphs showing experimental results at positive incidence and negative incidence (Δ d ═ 0), respectively;
fig. 5e is a far field profile of beam splitting at positive and negative incidence (Δ d ═ 0);
fig. 6 is a graph of contrast and operating frequency in a two-layer acoustic metamaterial surface (Δ d ═ 0.5 λ and Δ d ═ 0).
Detailed Description
The present invention will be described in detail below with reference to embodiments shown in the drawings. The embodiments are not intended to limit the present invention, and structural, methodological, or functional changes made by those skilled in the art according to the embodiments are included in the scope of the present invention.
Referring to fig. 1, the invention discloses an asymmetric acoustic wave separator based on binary super-structure surfaces, comprising a first super-cell 10 and a second super-cell 20 which are oppositely arranged, wherein the first super-cell 10 has a first acoustic super-structure surface (ABM-1), the second super-cell 20 has a second acoustic super-structure surface (ABM-2), an air gap Δ d is arranged between the first super-cell and the second super-cell, the first super-cell 10 comprises a plurality of first cells 11 and second cells 12 which are alternately arranged, the second super-cell 20 comprises a plurality of third cells 21 and fourth cells 22 which are alternately arranged, the third cells 21 comprise two groups of first cells 11, the fourth cells 22 comprise two groups of second cells 12, and the heights h and the widths w of the first cells 11 and the second cells 12 1 Are equal, the phase difference is pi, the height h and the width w of the third cell 21 and the fourth cell 22 2 Are all equal, the phase difference is pi, and w 2 ＝2w 1 The period length p of the first super cell 10 1 And the period length p of the second super cell 20 2 Satisfies p 2 ＝2p 1 。
In the present invention, p is set 1 ＝2w 1 ＜λ，p 2 ＝2w 2 λ > λ, λ being the wavelength of the acoustic wave incident from the first acoustic metamaterial surface (ABM-1), the exit direction of the transmitted or reflected wave being determined by:
wherein G is 1 ＝2π/p 1 The reciprocal lattice vector of the first acoustic metamaterial surface (ABM-1), n being a diffraction order,
(k 0 ＝2π/λ，θ in as the angle of incidence of the sound wave). Apparently, due to G in ABM-1 1 >k 0 These non-zero diffraction orders are normal incidence (θ) in 0) of the evanescent wave. It is envisioned that the emergent waves may be in the order of n ═ 0. Since ABG-1 consists of two elements, an incident wave can experience an even number of guided waves through the metamaterial surface. According to the odd-even diffraction law, the incident wave is totally reflected and the surface modes are bounded at the interface. While for p normally incident on ABM-2 2 ＝4w 1 >λ, the emergent wave follows:
wherein G is 2 ＝2π/p 2 (G 2 <k 0 )。
In this case, both of these propagating diffraction orders, n-0 and n-1, are possible for the incident wave. However, due to the phase gradient, the diffraction order n ± 1 is preferred. Therefore, the outgoing wave diffracted from the n ═ 1 channel can produce a beam splitting effect. According to the formula (2), the splitting angle of the acoustic wave is θ ═ arcsin (λ/p) 2 )。
Referring to fig. 2, the first cell 11 is a hollow substrate, the second cell 12 includes a hollow substrate and a plurality of partitions alternately disposed on two opposite inner walls of the substrate, and the substrate and the partitions are made of acrylic acid. The phase of two unit cells is respectively 0 and pi finally realized by the structure.
By combining the first acoustic metastructural surface (ABM-1), the second acoustic metastructural surface (ABM-2) and the air gap Δ d, an asymmetric beam splitting of the acoustic wave can be achieved. For normal incidence (incident wave propagating in the + y direction), the incident wave may pass through the ABM-2 with a beam splitting effect. Theta in air gap ═ arcsin (lambda/p) 2 ) The emergent wave may further impinge on ABM-1. According to the equation (1),
can pass through
The negative refraction effect caused by the order passes through ABM-1 to realize the emergent angle theta ═ arcsin (lambda/p) 2 ). Efficient splitting at normal incidence is well seen from equation (3):
For negative incidence, i.e., incident waves propagating in the-y direction, weakly transmitted waves are generally incident on ABM-2 due to the effect of total reflection in ABM-1, resulting in inefficient beam splitting.
Referring to fig. 3, for the case of a closed air gap (Δ d ═ 0), ABM-1 and ABM-2 can form a single layer super surface with periodic modulations of "0", "pi", and "0" and a period length of p 2 . It is clear that the asymmetric diffraction orders disappear, so that efficient beam splitting can take place for both positive and negative incidence.
In one embodiment of the present inventionThe working frequency is 3430Hz (lambda is 10cm), h is 0.5 lambda,
therefore, the splitting angle θ is arcsin (λ/p) 2 )＝45°。
Two samples of designed ABM-1 and ABM-2 were made according to the above parameters and their total reflection and transmission beam splitting wave functions were revealed through experiments. Tunable asymmetric transmission of beam splitting was observed by placing two ABMs in a two-dimensional acoustic waveguide. The loudspeaker array was used to generate incident plane waves and the pressure field distribution in the waveguide was measured using a moving microphone stepped at 1.0 cm. To eliminate unwanted reflections, a foam is placed at the boundary of the waveguide.
Applicants studied double-layer acoustic ultrastructural surface ABMs with an air gap Δ d and found that the coupling between ABM-1 and ABM-2 can be effectively reduced when Δ d >0.3 λ. Therefore, the air gap Δ d of 0.5 λ is designed in the present invention for observing the asymmetric transmission effect.
A numerically simulated field pattern for a normal incidence two-layer acoustic metamaterial surface is shown in fig. 4a, where a highly efficient beam splitting effect with θ equal to 45 ° can be seen. Experiments were performed to measure the efficient beam splitting, the measurement area being indicated by the white dashed box in fig. 2 a. The experimental results in fig. 4b show that the emergent wave is ejected in two directions and confirms efficient beam splitting, which is consistent with the values. For negative incidence, fig. 4c shows numerically inefficient beam splitting in a two-layer acoustic superstructure surface, and the incident wave is almost reflected back. The results of the experiment in 4d confirm this inefficient beam splitting. To further demonstrate asymmetric beam splitting, the far field distribution of the two incident beam splits is shown in FIG. 4e, where the measured radius is 10 λ (0cm, 7.5cm) from the center of the exit end. In the planar acoustic waveguide formed by two acrylic plates, the experimental results were normalized to the maximum of the simulation results, and both results consistently show the asymmetric performance of the beam splitting.
The air gap Δ d may be used as an additional degree of freedom to achieve switching of asymmetric and symmetric transmission in a two-layer acoustic metamaterial surface. When the air gap is closed, i.e., Δ d ═ 0, symmetric transmission of the split beam can be achieved. As shown in the numerically simulated field diagrams in fig. 5a and 5c, efficient beam splitting can occur independent of the direction of incidence. The corresponding experimental results in fig. 5b and 5d demonstrate efficient splitting of positive and negative incidence. The corresponding far field performance for symmetric splitting is shown in fig. 5e, with experimental results consistent with simulation results.
To quantitatively reveal the performance of symmetric/asymmetric transport effects, the contrast η of the transmitted energy from opposite incidence is defined as:
η＝|E PI -E NI |/(E PI +E NI )；
wherein, E PI And E NI Respectively, positive and negative incident transmitted energy.
The transmission energy was measured at a distance of 2 λ from the sample in both cases, and fig. 6 shows the relationship between the contrast and the operating frequency, where the upper and lower curves represent the cases of asymmetric and symmetric transmission, respectively, and the realized and dotted lines represent the simulated value (Sim) and the experimental value (Exp), respectively. The operating frequency range considered runs around a central frequency of 3430Hz, i.e. from 3.0kHz to 3.8 kHz.
It is excellent that the contrast of the asymmetric transmission in the experiment can keep good performance (eta is more than or equal to 0.8) in the range of 3.28kHz to 3.54kHz, so the bandwidth is about 7.8 percent of the central frequency and slightly deviates from 6.8 percent in the simulation.
For the case of symmetric transmission, the contrast was below 20% in both the simulation and the experiment. Although the proposed double-layer acoustic metamaterial surface is made of a simple acoustic structure, the asymmetric transmission performance can maintain a certain frequency band, which is useful in practical applications. Furthermore, the applicants have found that asymmetric transmission can operate not only at normal incidence, but also at oblique incidence.
According to the technical scheme, the invention has the following beneficial effects:
the invention constructs two double-layer acoustic ultrastructural surfaces through unit cells with different periods, realizes tunable asymmetric transmission of sound waves based on the transition of a diffraction channel by adjusting an air gap, has robustness on working frequency and an incident angle, and can be applied to devices such as a passive acoustic diode and the like.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.
Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.
Claims (9)
1. An asymmetric acoustic wave separator based on binary super-structure surfaces, characterized in that the separator comprises a first super-cell and a second super-cell which are oppositely arranged, the first super-cell has a first acoustic super-structure surface, the second super-cell has a second acoustic super-structure surface, an air gap delta d is arranged between the first super-cell and the second super-cell, the first super-cell comprises a plurality of first cells and second cells which are alternately arranged, the second super-cell comprises a plurality of third cells and fourth cells which are alternately arranged, the third cells comprise two groups of first cells, the fourth cells comprise two groups of second cells, the height h and the width w of the first cells and the second cells are 1 Are all equal, the phase difference is pi, the height h and the width w of the third and the fourth unit cell 2 Are all equal, the phase difference is pi, and w 2 ＝2w 1 Period length p of the first super cell 1 And the period length p of the second super cell 2 Satisfies p 2 ＝2p 1 。
2. The binary unstructured surface based asymmetric sound wave separator according to claim 1, characterized in that the separator satisfies:
p 1 ＝2w 1 ＜λ，p 2 ＝2w 2 ＞λ，θ＝arcsin(λ/p 2 )；
where λ is the wavelength of the acoustic wave and θ is the splitting angle of the acoustic wave.
3. The binary unstructured surface based asymmetric sound wave separator according to claim 1, characterized in that the separator satisfies: Δ d >0.3 λ, h ═ 0.5 λ,
θ＝arcsin(λ/p 2 )＝45°。
4. the binary unstructured surface based asymmetric acoustic wave separator of claim 3, wherein Δ d ═ 0.5 λ in the separator.
5. The binary metastructural surface based asymmetric acoustic wave separator according to claim 4, wherein a contrast η of the separator is:
η＝|E PI -E NI |/(E PI +E NI )；
wherein E is PI And E NI Respectively, positive and negative incident transmitted energy.
6. The binary metastasized surface based asymmetric acoustic separator of claim 5 where the separator has a frequency of operation between 3.28kHz and 3.54kHz and a contrast η of 0.8 or more.
7. The binary unstructured surface based asymmetric acoustic wave separator as claimed in claim 5, wherein the separator has an operating frequency of 3.43kHz and an acoustic wavelength λ of 10 cm.
8. The separator of claim 1, wherein the first unit cell is a hollow base, and the second unit cell comprises a hollow base and a plurality of staggered partitions on two opposite inner walls of the base.
9. The binary microstructured surface based asymmetric acoustic wave separator as claimed in claim 8, wherein the material of the base and the spacer is acrylic.
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| CN202210513457.7A CN114999437A (en) | 2022-05-11 | 2022-05-11 | Asymmetric sound wave separator based on binary ultrastructural surface |
| PCT/CN2022/126125 WO2023216507A1 (en) | 2022-05-11 | 2022-10-19 | Asymmetric acoustic wave separator based on binary metasurface |
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| CN105895074A (en) * | 2016-04-11 | 2016-08-24 | 南京大学 | Acoustic unidirectional hyper surface |
| CN111489732B (en) * | 2020-03-16 | 2024-01-19 | 中国农业大学 | Acoustic super-surface and design method thereof and acoustic device |
| CN111681634B (en) * | 2020-07-01 | 2023-06-20 | 南京航空航天大学 | Acoustic vortex separator based on angular super-structured surface |
| CN111665582A (en) * | 2020-07-06 | 2020-09-15 | 苏州大学 | Asymmetric electromagnetic wave separator based on binary ultrastructural surface |
| CN114999437A (en) * | 2022-05-11 | 2022-09-02 | 苏州大学 | Asymmetric sound wave separator based on binary ultrastructural surface |
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