Multi-order asymmetric acoustic vortex generator based on acoustic metamaterial and generation method thereof

Abstract

The present application relates to the technical field of acoustic metamaterials, and specifically relates to a multi-order asymmetric acoustic vortex generator and a generation method based on acoustic metamaterials, which comprises a phased structure I, a phased structure II, a three-dimensional mirror structure, a three-dimensional cylindrical waveguide base, a signal input structure and a quantitative evaluation structure; the phased structure I, the phased structure II and the three-dimensional mirror structure are coaxially arranged in the three-dimensional cylindrical waveguide base in sequence, the phased structure I and the phased structure II are sound wave incidence ends, and the three-dimensional mirror structure is a sound wave transmission end; the other end of the three-dimensional cylindrical waveguide base is provided with the quantitative evaluation structure, which is used for detecting the generation quality of the multi-order asymmetric acoustic vortex, and can realize the asymmetric generation of-2~+2 order acoustic vortexes in a wideband range, and has the characteristics of high mode purity, high acoustic energy transmission efficiency and structural integration, so as to solve the difficulties faced by the prior art in the collaborative realization of multi-order, wideband and asymmetric acoustic vortexes.

Description

Technical Field

[0001] This invention relates to the field of acoustic metamaterials technology, specifically to a multi-order asymmetric acoustic vortex generator and generation method based on acoustic metamaterials. Background Technology

[0002] Acoustic vortexes have significant applications in the field of acoustic communication. Asymmetric acoustic transmission can prevent information leakage while receiving information in acoustic communication. The topological order of acoustic vortexes can serve as a new transmission channel in acoustic communication. Acoustic vortex generators with multi-order characteristics can greatly improve their channel capacity. Therefore, acoustic vortex generation, which combines asymmetric transmission and multi-order characteristics, has a great driving effect on the development of the field of acoustic communication.

[0003] Traditional passive or active acoustic vortex field generation technologies have a single orbital angular momentum order, which can only achieve asymmetric transmission of single-order acoustic vortices and cannot generate multi-order asymmetric acoustic vortices. This makes it difficult to improve the channel capacity of acoustic communication and meet the needs of multi-channel transmission. Furthermore, due to the inherent narrow bandwidth limitations of accumulated phase shift and acoustic resonance structure, the generated multi-order acoustic vortices have a narrow working bandwidth, making it difficult to achieve broadband flexible control and lacking broadband robust control capabilities.

[0004] Meanwhile, existing acoustic vortex generation technologies cannot effectively integrate broadband mode conversion and multi-order asymmetric transmission mechanisms, making it difficult to guarantee asymmetric transmission characteristics while generating multi-order acoustic vortices. This limits their application to acoustic communication scenarios where information security is critical. Furthermore, some structural modes suffer from low purity, resulting in poor vortex generation quality. Moreover, the generated structure and the asymmetric transmission structure are independent, leading to complex combined structures and increased technical costs due to the resulting complex control circuitry, resulting in low sound energy transmission efficiency. Additionally, there is a lack of quantitative measurement of the generated quality of multi-order acoustic vortices, making it impossible to accurately evaluate the mode purity and transmission characteristics of the vortices. Therefore, a novel acoustic vortex generation technology is urgently needed in this field. To address this, a multi-order asymmetric acoustic vortex generator and generation method based on acoustic metamaterials are proposed. Summary of the Invention

[0005] To address the technical problems existing in the prior art, the present invention provides a multi-order asymmetric acoustic vortex generator and generation method based on acoustic metamaterials.

[0006] To address the aforementioned technical problems, this invention provides the following technical solution: a multi-order asymmetric acoustic vortex generator and generation method based on acoustic metamaterials, comprising a phased array assembly, a three-dimensional mirror structure, a three-dimensional cylindrical waveguide substrate, a signal input structure, and a quantitative evaluation structure; the phased array assembly includes phased array structure I and phased array structure II; phased array structure I, phased array structure II, and the three-dimensional mirror structure are coaxially arranged sequentially inside the three-dimensional cylindrical waveguide substrate, phased array structure I and phased array structure II are acoustic wave incident ends, and the three-dimensional mirror structure is acoustic wave transmission end; a signal input structure is provided at one end of the three-dimensional cylindrical waveguide substrate near phased array structure I, for inputting a stable plane wave signal to the integrated device, providing an incident acoustic wave source for the generation of acoustic vortices; a quantitative evaluation structure is provided at the other end of the three-dimensional cylindrical waveguide substrate, for detecting the generation quality of the multi-order asymmetric acoustic vortex;

[0007] Both phase control structure I and phase control structure II are composed of eight evenly distributed sector units; each sector unit is provided with several baffle assemblies to form a sawtooth acoustic channel.

[0008] Preferably, both phase control structure I and phase control structure II are made of high-stiffness, low-velocity superstructure materials. The last four of the eight sector units correspond one-to-one with the first four phase values, which are characterized by four different phase parameters. Each sector unit is a wound spatial structure.

[0009] Preferably, both the phased array structure I and the phased array structure II are composed of two groups of four different sector units. The eight groups of sector units in the phased array structure I and the phased array structure II are arranged in a cylindrical shape from number one to number eight. The parameters of sector unit one are the same as those of sector unit five, the parameters of sector unit two are the same as those of sector unit eight, the parameters of sector unit three are the same as those of sector unit seven, and the parameters of sector unit four are the same as those of sector unit six.

[0010] Preferably, the material of the three-dimensional mirror structure is the same as that of the phased array structure I. The three-dimensional mirror structure is composed of three periodically distributed scatterers that are symmetrically mirrored in the horizontal axis direction, forming a three-dimensional periodic unit cell structure. The three scatterers are fixed together by a number of evenly distributed connecting rods. One end of all the connecting rods is fixedly connected to the phased array structure II. The connecting rods are made of the same material as the scatterers.

[0011] The phased structure I, phased structure II and three-dimensional mirror structure are an integral structure. The two phased cylinders (1) are tightly fitted to the inner wall of the three-dimensional cylindrical waveguide substrate without gaps. The acoustic medium between the phased structure I, phased structure II and three-dimensional mirror structure is continuous.

[0012] Preferably, each of the scatterers is cylindrical, and the radius of each of the mirror scatterers is three-quarters of the radius of the three-dimensional cylindrical waveguide, the period constant is two-thirds of the radius of the three-dimensional cylindrical waveguide, and the thickness is 2 mm.

[0013] Preferably, the three-dimensional cylindrical waveguide substrate uses a low-loss acoustic medium to match the acoustic characteristics of air. The three-dimensional cylindrical waveguide substrate is a hollow cylinder with a radius R of 50 mm. λ is the wavelength corresponding to the center frequency.

[0014] Preferably, the signal input structure includes a plane wave transmitter and a power amplifier, wherein the plane wave transmitter is a high-fidelity acoustic wave emitting device, the plane wave transmitter is coaxially connected to the input end of the three-dimensional cylindrical waveguide substrate, and there is acoustic matching between the plane wave transmitter and the input end of the three-dimensional cylindrical waveguide substrate.

[0015] Preferably, the quantitative evaluation structure includes a microphone, an M+P signal analyzer, and a computer. The microphone is used to receive acoustic signals, and the M+P signal analyzer and computer perform signal analysis and evaluation on the received acoustic signals. Sound-absorbing cotton is provided inside the three-dimensional cylindrical waveguide substrate outside the microphone.

[0016] A method for generating multi-order asymmetric acoustic vortices, the method comprising the following steps:

[0017] S1, Assemble and adjust settings according to the generated order: Install the phased array components and the three-dimensional mirror structure into the three-dimensional cylindrical waveguide substrate, connect the signal input structure to the incident end of the three-dimensional cylindrical waveguide substrate, the plane wave transmitter generates an excitation signal, the power amplifier amplifies the generated excitation signal, and finally the signal is output through the speaker. Then fix the three-dimensional cylindrical waveguide substrate on the acoustic experimental platform, and select the corresponding phased array components according to the required order of the acoustic vortex.

[0018] S2, Plane wave input: A stable plane wave is input to the incident end of the three-dimensional cylindrical waveguide substrate through a plane wave transmitter. The frequency of the incident sound wave is adjusted within a wide bandwidth, specifically: first order 2740~3850Hz, second order 3350~4154Hz, and common bandwidth 3350~3850Hz. After passing through eight sector units of phase control structure I and phase control structure II, the plane wave completes phase modulation and forms a phase distribution that satisfies the adjacent phase difference of 2mπ / L, where L=8 and m is the order.

[0019] S3, Multi-order acoustic vortex mode conversion: The acoustic wave after phase modulation by the phase control component completes the mode conversion from plane wave to acoustic vortex of a specified order based on the multipole superposition mechanism, generating -2 to +2 order acoustic vortices. During this process, the winding space structure of the fan-shaped unit ensures the phase modulation stability in the broadband range, so that the acoustic vortex maintains high mode purity in the broadband band.

[0020] S4, Multi-order Asymmetric Acoustic Vortex Transmission: The generated multi-order acoustic vortices propagate to the three-dimensional mirror structure. The multi-order vortex mode band of the three-dimensional mirror structure allows -2 to +2 order acoustic vortices to pass through, while blocking the reverse propagation of plane waves. When the acoustic wave is incident from one side of the combined phased array structure, the acoustic vortex can be transmitted efficiently. When the acoustic wave is incident from the other side of the three-dimensional mirror structure, the plane wave is completely blocked, realizing the asymmetric transmission of multi-order acoustic vortices.

[0021] S5, Acoustic Vortex Output and Performance Testing: Broadband multi-order asymmetric acoustic vortices are output from the transmission end of a three-dimensional mirror structure. The sound pressure field, amplitude field, and phase field of the transmission end are measured using acoustic testing equipment. The sound pressure data of the transmission end section are extracted, and the transmission coefficient, transmission contrast, and mode purity of the acoustic vortex are calculated to quantitatively evaluate the generation quality of the multi-order asymmetric acoustic vortex.

[0022] Preferably, the specific control method in step S1 is as follows: the phased array component consisting of the first sector unit of phased array structure I and the second sector unit of phased array structure II is placed in the three-dimensional cylindrical waveguide substrate (4) to generate a +1 order acoustic vortex; the phased array component consisting of the first sector unit of phased array structure I and the eighth sector unit of phased array structure II is placed in the three-dimensional cylindrical waveguide substrate (4) to generate a -1 order acoustic vortex; the phased array component consisting of the first sector unit of phased array structure I and the third sector unit of phased array structure II is placed in the three-dimensional cylindrical waveguide substrate (4) to generate a +2 order acoustic vortex; the phased array component consisting of the first sector unit of phased array structure I and the seventh sector unit of phased array structure II is placed in the three-dimensional cylindrical waveguide substrate (4) to generate a -2 order acoustic vortex.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] 1. This invention uses phase superposition theory to design an integrated device that combines a combined phased array structure and a three-dimensional mirror structure. It extends the mode conversion and asymmetric mechanism from single-order to multi-order, successfully realizing the asymmetric generation of -2 to +2 order acoustic vortices. This broadens the order of controllable acoustic vortex fields and provides a core device for multi-channel transmission in unidirectional acoustic communication. It can realize the mode conversion from plane wave to multi-order vortex, greatly improving the channel capacity of acoustic communication. Furthermore, by using a three-dimensional cylindrical waveguide substrate to achieve the coaxial arrangement of the phased array structure and the three-dimensional mirror structure, the structure is compact and highly integrated, avoiding the complex combination of traditional independent structures. The connecting rods fix each substructure into a whole, ensuring the structural stability during sound wave propagation and reducing sound energy loss.

[0025] 2. This invention constructs an integrated phased array structure and a three-dimensional mirror structure with broadband mode conversion function. The three-dimensional mirror structure forms a multi-order vortex energy band through dispersion relation, allowing vortices to pass through and blocking plane waves from propagating in the opposite direction. It realizes broadband asymmetric generation of first-order acoustic vortices (2740~3850Hz) and second-order acoustic vortices (3350~4154Hz), with a common broadband of 3350~3850Hz. Moreover, the transmission coefficient within the broadband is higher than 0.61, which solves the problem of narrow working bandwidth in the prior art, gets rid of the single wavelength limitation, and improves the broadband robust control capability of the acoustic vortex field.

[0026] 3. This invention reveals a broadband multi-order asymmetric mechanism, achieving efficient synergy between mode conversion and asymmetric effects. The purity of the principal order modes of the -2 to +2 order acoustic vortices is higher than 0.85, and the purity of the +1 order mode at the operating frequency of 3430 Hz reaches 0.9. The transmission coefficient in the PⅠ direction is above 0.93, the transmission coefficient in the MⅠ direction is close to 0, and the transmission contrast is above 0.94, ensuring high mode purity and high acoustic energy transmission efficiency.

[0027] 4. This invention introduces a mode purity index and establishes a quantitative evaluation method for the generation quality of multi-order asymmetric acoustic vortices. This method can accurately measure the mode purity and transmission performance of acoustic vortices, providing a quantitative basis for optimizing structural parameters and improving the generation performance of acoustic vortices. This enhances the optimizability and engineering practicality of the technology, ensures the generation quality of multi-order asymmetric acoustic vortices, and facilitates the widespread application of multi-order asymmetric acoustic vortices in unidirectional underwater acoustic communication.

[0028] 5. The substructures of the multi-order asymmetric acoustic vortex generator in this invention are all made of standardized acoustic metamaterials. The fan-shaped unit, mirror scatterer and other structures can be precisely processed by 3D printing technology. The phase modulation parameters of the phase control components can be determined by finite element simulation optimization. The process is mature, the preparation is easy, and the structural parameters can be flexibly adjusted according to the actual application requirements. It has good engineering application prospects in acoustic manipulation fields such as acoustic levitation, ultrasound diagnosis and treatment, and targeted drug delivery. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the overall structure of the multi-order asymmetric acoustic vortex generator of the present invention during operation.

[0030] Figure 2 This is a schematic diagram of the phase control structure I, phase control structure II, and three-dimensional mirror structure of the present invention;

[0031] Figure 3 This is a schematic diagram of the phase control structure I of the present invention;

[0032] Figure 4 This is a schematic diagram of the Roz cross-section of the sector-shaped unit of the present invention;

[0033] Figure 5 This is a schematic diagram of the internal structure of the phase control structure of the present invention;

[0034] Figure 6 This is a front cross-sectional view of the phase control structure I and phase control structure II of the present invention;

[0035] Figure 7 This is a schematic diagram of the sector unit structure of the phase control structure I of the present invention;

[0036] Figure 8 This is a schematic diagram of the sector-shaped unit structure of the phase control structure II of the present invention;

[0037] Figure 9 This is a schematic diagram illustrating the effect of the multi-order asymmetric acoustic vortex generated by the present invention.

[0038] Figure 10 This is a schematic diagram of the multi-order broadband transmission coefficient and contrast of the present invention;

[0039] Figure 11 This is a schematic diagram of the purity of the multi-order acoustic vortex mode of the present invention.

[0040] Figure 12 This is a schematic diagram of the broadband mode purity of the multi-order acoustic vortex of the present invention.

[0041] The numbers in the diagram represent:

[0042] 1. Phased array tube; 2. Unit partition; 3. Baffle assembly; 4. Three-dimensional cylindrical waveguide substrate; 5. Loudspeaker; 6. Microphone; 7. Sound-absorbing cotton; 8. Power amplifier; 9. M+P signal analyzer; 10. Computer. Detailed Implementation

[0043] The present invention will be further described below with reference to the accompanying drawings and embodiments, which illustrate the above and other technical features and advantages of the present invention. However, the following embodiments are merely preferred embodiments of the present invention and are not exhaustive.

[0044] Example:

[0045] like Figure 1-12 As shown, this invention provides a multi-order asymmetric acoustic vortex generator and generation method based on acoustic metamaterials, including a phased array assembly, a three-dimensional mirror structure, a three-dimensional cylindrical waveguide substrate 4, a signal input structure, and a quantitative evaluation structure. The phased array assembly includes a phased array structure I and a phased array structure II. The phased array structure I, phased array structure II, and the three-dimensional mirror structure are arranged coaxially inside the three-dimensional cylindrical waveguide substrate 4. The phased array structure I and phased array structure II are the acoustic wave incident ends, and the three-dimensional mirror structure is the acoustic wave transmission end. A signal input structure is provided at one end of the three-dimensional cylindrical waveguide substrate 4 near the phased array structure I, for inputting a stable plane wave signal to the integrated device, providing an incident acoustic wave source for the generation of acoustic vortices. A quantitative evaluation structure is provided at the other end of the three-dimensional cylindrical waveguide substrate 4, for detecting the generation quality of the multi-order asymmetric acoustic vortex.

[0046] Both phase control structure I and phase control structure II are composed of eight evenly distributed sector units; each sector unit is provided with several baffle assemblies to form a sawtooth acoustic channel.

[0047] In this embodiment, both phase control structure I and phase control structure II are made of high-stiffness, low-sound-velocity superstructure material (density 1400kg / m3, sound velocity 1950m / s) to ensure the phase modulation effect of sound waves and structural stability. The last four of the eight sector units correspond one-to-one with the phase values ​​of the first four, and are characterized by four different phase parameters. Each sector unit is a wound space structure.

[0048] In this embodiment, both phased-array structure I and phased-array structure II are composed of two groups of four different sector units. The eight groups of sector units in phased-array structure I and phased-array structure II are arranged in a cylindrical phased-array structure in order from number one to number eight. The parameters of sector unit one are the same as those of sector unit five, the parameters of sector unit two are the same as those of sector unit eight, the parameters of sector unit three are the same as those of sector unit seven, and the parameters of sector unit four are the same as those of sector unit six. Figure 5 As shown, the unit partition 2 is set to 1mm, and the parameters of the baffle assembly 3 are simulated in COMSOL under two-dimensional axisymmetric conditions. The length of the baffle assembly is measured by parametric scanning. Figure 5 (Based on the b value in the equation), the appropriate baffle assembly parameters for each sector unit are obtained according to the final phase output of each parameter b.

[0049] By changing the number, length, and spacing of the baffles inside the sector unit, the effective path of sound wave propagation is modulated, the required adjacent phase difference is obtained, and the phase modulation stability within the broadband range is guaranteed.

[0050] In this embodiment, the material of the three-dimensional mirror structure is the same as that of the phased structure I, which ensures the continuity of the medium for sound wave propagation and reduces sound energy loss. The three-dimensional mirror structure consists of three periodically distributed scatterers that are symmetrically mirrored in the horizontal axis direction, forming a three-dimensional periodic unit cell structure. The three scatterers are fixed together by a number of evenly distributed connecting rods. One end of all the connecting rods is fixedly connected to the phased structure II. The connecting rods are made of the same material as the scatterers.

[0051] Phased structure I, phased structure II, and three-dimensional mirror structure are integrated into a single structure, ensuring the coaxiality and stability of the structure without affecting the propagation characteristics of sound waves. The two phased cylinders 1 are tightly fitted to the inner wall of the three-dimensional cylindrical waveguide substrate 4 without gaps, preventing the reflection and leakage of sound waves at the gaps. The acoustic medium between phased structure I, phased structure II, and three-dimensional mirror structure is continuous.

[0052] In this embodiment, each scatterer is cylindrical, and the radius of each mirror scatterer is three-quarters of the radius of the three-dimensional cylindrical waveguide, the period constant is two-thirds of the radius of the three-dimensional cylindrical waveguide, and the thickness is 2mm.

[0053] By controlling the dispersion relation to form a multi-order vortex mode energy band, -2 to +2 order acoustic vortices are allowed to pass through within a specific frequency band, while blocking plane wave propagation, thus realizing the asymmetric transmission of multi-order acoustic vortices; the intrinsic vortex modes in the three-dimensional cylindrical waveguide are decoupled to ensure the high mode purity of the acoustic vortices.

[0054] In this embodiment, the three-dimensional cylindrical waveguide substrate 4 uses a low-sound-loss acoustic medium to match the acoustic characteristics of air (air density is 1.21 kg / m³, sound velocity is 343 m / s), reducing sound wave reflection and loss within the waveguide. The three-dimensional cylindrical waveguide substrate 4 is a hollow cylinder with a radius R of 50 mm. λ is the wavelength corresponding to the center frequency.

[0055] In this embodiment, the signal input structure includes a plane wave transmitter and a power amplifier 8. The plane wave transmitter is a high-fidelity acoustic wave emitting device. The plane wave transmitter is coaxially connected to the input end of the three-dimensional cylindrical waveguide substrate 4. The plane wave transmitter and the input end of the three-dimensional cylindrical waveguide substrate 4 are acoustically matched (the two are acoustically impedance matched, with minimal interface reflection, maximum energy transmission efficiency, and minimal waveform distortion).

[0056] In this embodiment, the quantitative evaluation structure includes a microphone 6, an M+P signal analyzer 9, and a computer 10. The microphone 6 is used to receive acoustic signals, and the M+P signal analyzer 9 and the computer 10 perform signal analysis and evaluation on the received acoustic signals. Sound-absorbing cotton 7 is provided inside the three-dimensional cylindrical waveguide substrate 4 outside the microphone 6.

[0057] In this embodiment, the generation method includes the following steps:

[0058] S1, Assemble and adjust settings according to the generated order: Install the phase control component and the three-dimensional mirror structure into the three-dimensional cylindrical waveguide substrate 4, connect the signal input structure to the incident end of the three-dimensional cylindrical waveguide substrate 4, the plane wave transmitter generates an excitation signal, the power amplifier 8 amplifies the generated excitation signal, and finally outputs the signal through the speaker 5. Then fix the three-dimensional cylindrical waveguide substrate 4 on the acoustic experimental platform, and select the corresponding phase control component according to the required generated acoustic vortex order.

[0059] S2, Plane wave input: A stable plane wave is input to the incident end of the three-dimensional cylindrical waveguide substrate 4 through a plane wave transmitter. The frequency of the incident sound wave is adjusted within a wide range, specifically: first order 2740~3850Hz, second order 3350~4154Hz, and common wide range 3350~3850Hz. After passing through eight sector units of phase control structure I and phase control structure II, the plane wave completes phase modulation, forming a phase distribution that satisfies the adjacent phase difference of 2mπ / L, where L=8 and m is the order.

[0060] S3, Multi-order acoustic vortex mode conversion: The acoustic wave after phase modulation by the phase control component completes the mode conversion from plane wave to acoustic vortex of a specified order based on the multipole superposition mechanism, generating -2 to +2 order acoustic vortices. During this process, the winding space structure of the fan-shaped unit ensures the phase modulation stability in the broadband range, so that the acoustic vortex maintains high mode purity in the broadband band.

[0061] Based on the phase definition of acoustic vortices, an m-order acoustic vortex occurs uniformly within a circular angular range. The phase change divides the circumferential phase distribution into equal parts. If the phase difference between adjacent m-order acoustic vortices is given by... Therefore, adjacent A phase difference that is a multiple of is key to generating acoustic vortices; using equal arithmetic progressions... and Two sets of equally arithmetic adjacent phase differences are superimposed to form multi-order acoustic vortices, namely phased-array structure I and phased-array structure II, which are divided into eight parts, numbered 1 to 8. When part 1 of phased-array I is superimposed with part 1 of phased-array II, the resulting adjacent phase differences are all 0, and the output is a plane wave. However, when part 2 of phased-array II is superimposed with part 1 of phased-array I at the same position, it is equivalent to adding an equally arithmetic phase difference to the previous case. This is the adjacent phase difference of a first-order acoustic vortex, generating a first-order acoustic vortex; similarly, when the third vortex in phased structure II is superimposed on the first vortex in phased structure I at the same position, it is equivalent to adding two equally arithmetic phases to the previous case. This is the phase difference between adjacent second-order acoustic vortices, thus generating second-order acoustic vortices. Similarly, acoustic vortices of any order can be generated.

[0062] S4, Multi-order Asymmetric Acoustic Vortex Transmission: The generated multi-order acoustic vortices propagate to the three-dimensional mirror structure. The three-dimensional mirror structure ensures the asymmetry of sound wave propagation. The multi-order vortex mode band of the three-dimensional mirror structure allows -2 to +2 order acoustic vortices to pass through, while blocking the reverse propagation of plane waves. When the sound wave is incident from one side of the combined phased array structure (PI direction), the acoustic vortex can be transmitted efficiently. When the sound wave is incident from the other side of the three-dimensional mirror structure (MI direction), the plane wave is completely blocked, realizing the asymmetric transmission of multi-order acoustic vortices.

[0063] The diversity of vortex mode bands in a three-dimensional mirror structure is caused by its geometric mirror characteristics. The mirror characteristics induce the decoupling of intrinsic vortex modes within the waveguide structure, keeping its vortex modes independent and creating a single vortex mode band. Only specific modes are allowed to pass through the single mode band, which promotes the selectivity of vortex modes and plane wave modes.

[0064] The three-dimensional mirror structure determines the parameters of three scatterers, fixing vortex waves of different orders in different frequency ranges. The frequency ranges of different orders may overlap. For example, the plane wave bandgap in this structure is 0-2732Hz, the bandgap of the first-order acoustic vortex is 1989 to 4178Hz, and the bandgap of the second-order vortex wave is 3306 to 5385Hz. Within the energy band of 3306 to 4178Hz, the propagation of the first-order and second-order acoustic vortices can be allowed while blocking other modes of vortex waves.

[0065] S5, Acoustic Vortex Output and Performance Testing: Broadband multi-order asymmetric acoustic vortices are output from the transmission end of a three-dimensional mirror structure (any cross-section after the sound wave modulated by the phase control component has completely passed through the three-dimensional mirror structure). The sound pressure field, amplitude field, and phase field of the transmission end are measured by acoustic testing equipment (microphone, signal analyzer). The sound pressure data of the transmission end cross-section are extracted, and the transmission coefficient, transmission contrast, and mode purity of the acoustic vortex are calculated to quantitatively evaluate the generation quality of the multi-order asymmetric acoustic vortex.

[0066] In this embodiment, when +1 order acoustic vortices need to be generated: the phased array assembly consisting of the first sector unit of phased array structure I and the second sector unit of phased array structure II is placed in the three-dimensional cylindrical waveguide substrate 4; when -1 order acoustic vortices need to be generated: the phased array assembly consisting of the first sector unit of phased array structure I and the eighth sector unit of phased array structure II is placed in the three-dimensional cylindrical waveguide substrate 4; when +2 order acoustic vortices need to be generated: the phased array assembly consisting of the first sector unit of phased array structure I and the third sector unit of phased array structure II is placed in the three-dimensional cylindrical waveguide substrate 4; when -2 order acoustic vortices need to be generated: the phased array assembly consisting of the first sector unit of phased array structure I and the seventh sector unit of phased array structure II is placed in the three-dimensional cylindrical waveguide substrate 4.

[0067] The above description is merely a preferred embodiment of the present invention and is illustrative rather than restrictive. Those skilled in the art will understand that many changes, modifications, and even equivalents can be made within the spirit and scope defined by the claims of the present invention, all of which will fall within the protection scope of the present invention.

Claims

1. A multi-order asymmetric acoustic vortex generator based on acoustic metamaterials, characterized in that, The system includes a phased array assembly, a three-dimensional mirror structure, a three-dimensional cylindrical waveguide substrate (4), a signal input structure, and a quantitative evaluation structure. The phased array assembly includes a phased array structure I and a phased array structure II. The phased array structure I, the phased array structure II, and the three-dimensional mirror structure are arranged coaxially inside the three-dimensional cylindrical waveguide substrate (4). The phased array structure I and the phased array structure II are the acoustic wave incident ends, and the three-dimensional mirror structure is the acoustic wave transmission end. A signal input structure is provided at one end of the three-dimensional cylindrical waveguide substrate (4) near the phased array structure I, which is used to input a stable plane wave signal to the integrated device and provide an incident acoustic wave source for the generation of acoustic vortices. The other end of the three-dimensional cylindrical waveguide substrate (4) is provided with a quantitative evaluation structure for detecting the generation quality of multi-order asymmetric acoustic vortices; Both phase control structure I and phase control structure II are composed of eight evenly distributed sector units; each sector unit is provided with several baffle assemblies to form a sawtooth acoustic channel.

2. The multi-order asymmetric acoustic vortex generator based on acoustic metamaterials as described in claim 1, characterized in that, Both phase control structure I and phase control structure II are made of high-stiffness, low-sound-velocity superstructure materials. The last four of the eight sector units correspond one-to-one with the first four phase values, and are characterized by four different phase parameters. Each sector unit is a wound-up space structure.

3. The multi-order asymmetric acoustic vortex generator based on acoustic metamaterials as described in claim 1, characterized in that, Both the phased array structure I and the phased array structure II are composed of two groups of four different sector units. The eight groups of sector units in the phased array structure I and the phased array structure II are arranged in a cylindrical shape from number one to number eight. The parameters of sector unit one are the same as those of sector unit five, the parameters of sector unit two are the same as those of sector unit eight, the parameters of sector unit three are the same as those of sector unit seven, and the parameters of sector unit four are the same as those of sector unit six.

4. The multi-order asymmetric acoustic vortex generator based on acoustic metamaterials as described in claim 1, characterized in that, The three-dimensional mirror structure is made of the same material as the phased structure I. The three-dimensional mirror structure is composed of three periodically distributed scatterers that are symmetrically mirrored in the horizontal axis direction, forming a three-dimensional periodic unit cell structure. The three scatterers are fixed together by a number of evenly distributed connecting rods. One end of all the connecting rods is fixedly connected to the phased structure II. The connecting rods are made of the same material as the scatterers. The phased structure I, phased structure II and three-dimensional mirror structure are an integral structure. The two phased cylinders (1) are tightly fitted to the inner wall of the three-dimensional cylindrical waveguide substrate (4) without gaps. The acoustic medium between the phased structure I, phased structure II and three-dimensional mirror structure is continuous.

5. The multi-order asymmetric acoustic vortex generator based on acoustic metamaterials as described in claim 4, characterized in that, Each of the scatterers is cylindrical, and each of the mirror scatterers has a radius of three-quarters of the radius of the three-dimensional cylindrical waveguide, a period constant of two-thirds of the radius of the three-dimensional cylindrical waveguide, and a thickness of 2 mm.

6. The multi-order asymmetric acoustic vortex generator based on acoustic metamaterials as described in claim 1, characterized in that, The three-dimensional cylindrical waveguide substrate (4) uses a low-loss acoustic medium to match the acoustic characteristics of air. The three-dimensional cylindrical waveguide substrate (4) is a hollow cylinder with a radius R of 50 mm. λ is the wavelength corresponding to the center frequency.

7. The multi-order asymmetric acoustic vortex generator based on acoustic metamaterials as described in claim 1, characterized in that, The signal input structure includes a plane wave transmitter and a power amplifier (8). The plane wave transmitter is a high-fidelity acoustic wave transmitting device. The plane wave transmitter is coaxially connected to the input end of the three-dimensional cylindrical waveguide substrate (4). The plane wave transmitter and the input end of the three-dimensional cylindrical waveguide substrate (4) are acoustically matched.

8. The multi-order asymmetric acoustic vortex generator based on acoustic metamaterials as described in claim 1, characterized in that, The quantitative evaluation structure includes a microphone (6), an M+P signal analyzer (9), and a computer (10). The microphone (6) is used to receive acoustic signals. The M+P signal analyzer (9) and the computer (10) perform signal analysis and evaluation on the received acoustic signals. The three-dimensional cylindrical waveguide substrate (4) outside the microphone (6) is provided with sound-absorbing cotton (7).

9. A method for generating multi-order asymmetric acoustic vortices, used in the multi-order asymmetric acoustic vortex generator according to any one of claims 1-8, characterized in that, The generation method includes the following steps: S1, Assemble and adjust settings according to the generation order: Install the phase control component and the three-dimensional mirror structure into the three-dimensional cylindrical waveguide substrate (4), connect the signal input structure to the incident end of the three-dimensional cylindrical waveguide substrate (4), the plane wave transmitter generates an excitation signal, the power amplifier (8) amplifies the generated excitation signal, and finally outputs the signal through the loudspeaker (5), then fix the three-dimensional cylindrical waveguide substrate (4) on the acoustic experimental platform, and select the corresponding phase control component according to the required generation order of the acoustic vortex; S2, plane wave input: A stable plane wave is input to the incident end of the three-dimensional cylindrical waveguide substrate (4) through a plane wave transmitter. The frequency of the incident sound wave is adjusted to be within the broadband range, specifically: first order 2740~3850Hz, second order 3350~4154Hz, and common broadband 3350~3850Hz. After passing through the eight sector units of phase control structure I and phase control structure II, the plane wave completes phase modulation and forms a phase distribution that satisfies the adjacent phase difference of 2mπ / L, where L=8 and m is the order. S3, Multi-order acoustic vortex mode conversion: The acoustic wave after phase modulation by the phase control component completes the mode conversion from plane wave to acoustic vortex of a specified order based on the multipole superposition mechanism, generating -2 to +2 order acoustic vortices. During this process, the winding space structure of the fan-shaped unit ensures the phase modulation stability in the broadband range, so that the acoustic vortex maintains high mode purity in the broadband band. S4, Multi-order Asymmetric Acoustic Vortex Transmission: The generated multi-order acoustic vortices propagate to the three-dimensional mirror structure. The multi-order vortex mode band of the three-dimensional mirror structure allows -2 to +2 order acoustic vortices to pass through, while blocking the reverse propagation of plane waves. When the acoustic wave is incident from one side of the combined phased array structure, the acoustic vortex can be transmitted efficiently. When the acoustic wave is incident from the other side of the three-dimensional mirror structure, the plane wave is completely blocked, realizing the asymmetric transmission of multi-order acoustic vortices. S5, Acoustic Vortex Output and Performance Testing: Broadband multi-order asymmetric acoustic vortices are output from the transmission end of a three-dimensional mirror structure. The sound pressure field, amplitude field, and phase field of the transmission end are measured using acoustic testing equipment. The sound pressure data of the transmission end section are extracted, and the transmission coefficient, transmission contrast, and mode purity of the acoustic vortex are calculated to quantitatively evaluate the generation quality of the multi-order asymmetric acoustic vortex.

10. The method for generating multi-order asymmetric acoustic vortices based on acoustic metamaterials as described in claim 9, characterized in that, The specific control method in step S1 is as follows: the phased component of the superimposed sector unit of phased structure I and sector unit of phased structure II is placed in the three-dimensional cylindrical waveguide substrate (4) to generate a +1 order acoustic vortex; the phased component of the superimposed sector unit of phased structure I and sector unit of phased structure II is placed in the three-dimensional cylindrical waveguide substrate (4) to generate a -1 order acoustic vortex; the phased component of the superimposed sector unit of phased structure I and sector unit of phased structure II is placed in the three-dimensional cylindrical waveguide substrate (4) to generate a +2 order acoustic vortex; the phased component of the superimposed sector unit of phased structure I and sector unit of phased structure II is placed in the three-dimensional cylindrical waveguide substrate (4) to generate a -2 order acoustic vortex.

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