An acoustic device applied to multi-modal vortex separation and detection

Abstract

The application discloses an acoustic device applied to multi-modal vortex separation and detection and belongs to the acoustic technical field. The acoustic device adopts a ring cylindrical waveguide structure, a plurality of groups of annular grooves are arranged on the inner wall, the depth of each group of annular grooves is linearly increased along the axial direction in a gradient distribution; the inner diameters of each group of annular grooves are the same and serve as the inner diameter of the waveguide; the outer diameter of the waveguide is larger than the inner diameter; probes are arranged at the annular grooves; and the measured sound pressure information is introduced into a computer through the probes. The application can effectively modulate the dispersion curve of different orbital angular momentum acoustic vortices, can make acoustic vortices of different modes stop at different spatial positions on the axial direction of the waveguide in turn, and can realize high-precision, parallelized distinguishing and detection of multi-modal acoustic vortices.

Description

Technical Field

[0001] This invention relates to the field of acoustics, and more particularly to an acoustic device for multimodal vortex separation and detection. Background Technology

[0002] Acoustic vortices, as acoustic field forms carrying orbital angular momentum, have attracted widespread attention due to their potential applications in acoustic communication, particle manipulation, and acoustic imaging. Different orbital angular momentum numbers of vortices represent different acoustic vortex modes. Especially in acoustic communication systems, multiplexing using different orbital angular momentum modes can significantly improve channel capacity and information security. However, how to achieve efficient separation and accurate detection of multimodal acoustic vortices in practical devices remains a key technical challenge in this field. Existing acoustic vortex separation methods often rely on complex external field manipulation, large transducer arrays, or mode selection devices, resulting in complex structures, low integration, and difficulty in achieving multimodal parallel processing, thus limiting their practical application in compact, integrated acoustic systems. Existing technical solutions can be mainly divided into the following three categories:

[0003] 1) Active modulation method based on phased-array transducers: This method utilizes multiple independent transducer units arranged in a ring or two-dimensional array. By applying an electrical signal with a specific phase delay to each unit, it synthesizes or receives a sound field with a specific orbital angular momentum in space. Its working principle is to actively construct a helical wavefront that matches the target vortex mode. Essentially, this technical solution is a complex acoustic phased-array system, including a signal generator, multi-channel power amplifier, and phase controller. Its system complexity and cost are extremely high, requiring a large number of independently controlled transducer channels, precise synchronization circuits, and complex real-time signal processing algorithms, resulting in bulky equipment, high power consumption, and difficulty in miniaturization and integration. Furthermore, this method essentially generates or analyzes specific modes, rather than physically separating and directly locating different incident modes.

[0004] 2) Passive filtering methods based on acoustic metasurfaces utilize specially designed subwavelength structural units to construct a planar metasurface. When sound waves pass through, each unit introduces a specific phase abrupt change through local resonance. By carefully arranging the spatial phase distribution of these units, the metasurface as a whole can act like a spiral phase plate, thereby generating or filtering acoustic vortices with specific topological charges in the transmission or reflection field. The core of its technical solution lies in the design and spatial coding of the units. Its main drawbacks are that the operating bandwidth is usually narrow, its performance is frequency-sensitive, and its function is relatively singular. A single metasurface is usually optimized only for single-mode conversion or filtering at a single frequency, making it difficult to simultaneously process multiple acoustic vortices with different orbital angular momentum over a wide frequency band and stop them at different spatial locations. It cannot achieve sequential separation and spatial localization of multi-mode vortices along the propagation direction.

[0005] 3) Methods based on traditional helical phase plates or mode selection waveguides employ hard-walled waveguides with fixed helical inner walls or periodic modulation structures. The principle is to match the waveguide geometry to the path difference of the target vortex mode, allowing only that mode to pass with low loss while suppressing other modes. This is a purely passive structural device, its performance determined by a fixed physical structure. Although the structure of this type of method is passive, its design is fixed, typically supporting only single-mode screening and lacking the flexibility for parallel processing of multiple modes. Its working principle is to allow one mode to pass while blocking others, failing to provide an intuitive, location-identifiable detection mechanism. Furthermore, its performance often lacks frequency response characteristics, making it difficult to adapt to changes in operating frequency. Summary of the Invention

[0006] Purpose of the invention: The purpose of this invention is to provide an acoustic device for multimodal vortex separation and detection, which solves the shortcomings of existing technologies that cannot achieve broadband, parallel, and spatially resolved separation and detection of multimodal acoustic vortices in a single passive device. By introducing an axially gradient groove depth to deceive the cylindrical waveguide, the acoustic vortices of different modes are sequentially stopped at different spatial positions along the waveguide axis, thereby achieving high-precision, parallel differentiation and detection of multimodal acoustic vortices.

[0007] Technical solution: An acoustic device for multimodal vortex separation and detection, which adopts a ring-shaped cylindrical waveguide structure with multiple sets of ring grooves on the inner wall. The depth of each set of ring grooves is linearly increasing along the axial direction. The inner diameter of each set of ring grooves is the same, which serves as the inner diameter of the waveguide. The outer diameter of the waveguide is larger than the inner diameter.

[0008] Probes are installed at each annular groove, and the measured sound pressure information is imported into a computer through the probes.

[0009] Furthermore, the depth of each group of annular grooves increases linearly along the direction of sound wave propagation.

[0010] Furthermore, each group consists of four annular grooves.

[0011] Furthermore, the outer diameter of the first set of annular grooves at the acoustic input end is the same as the outer diameter of the waveguide.

[0012] Furthermore, the waveguide is made of acoustically hard material, and the medium for each set of annular grooves and the inner diameter of the waveguide is air.

[0013] Compared with the prior art, the significant advantages of this invention are as follows:

[0014] 1. This invention adopts a cylindrical waveguide structure based on gradient groove depth. By precisely designing the axial distribution of the groove depth, the dispersion curves of acoustic vortices with different orbital angular momentum can be effectively modulated, so that acoustic vortices of different modes are successively stopped at different spatial positions along the waveguide axis, thereby realizing high-precision and parallel differentiation and detection of multi-mode acoustic vortices.

[0015] 2. This invention can adapt to the separation requirements of different frequency bands and modal numbers by adjusting the groove depth gradient and period parameters. Its structural design is flexible and easy to integrate. In acoustic communication systems, it can improve signal security; in the field of acoustic signal detection, it can achieve interference-free identification of acoustic vortex modes; and it can also be applied to integrated ventilation and sound insulation structures, effectively suppressing and separating specific acoustic modes while ensuring airflow. Therefore, this invention has significant practical value and broad application prospects in cutting-edge acoustic technologies and engineering applications. Attached Figure Description

[0016] Figure 1 This is an axonometric view of the overall structure of the present invention;

[0017] Figure 2 This is a two-dimensional cross-sectional view of the gradient deception waveguide structure.

[0018] Figure 3 for A schematic diagram showing the change in the stopping position of an acoustic vortex with frequency;

[0019] Figure 4 The diagram shows a comparison of the acoustic vortex responses of different orbital angular momentum at a frequency of 5600 Hz. In the diagram, (a) is the dispersion curve and (b) is the group velocity curve.

[0020] Figure 5 Comparison diagrams of acoustic pressure fields of acoustic vortices with different orbital angular momentum and cross-sectional fields of the groove surface at a frequency of 5600Hz are shown. Among them, (a) is a structural cross-sectional field diagram of the incident acoustic vortex, and (b) is a distribution diagram of the acoustic field modes along the surface of the gradient groove. Detailed Implementation

[0021] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0022] like Figure 1 As shown, the present invention provides an acoustic device for multimodal vortex separation and detection. The acoustic device adopts a gradient groove deep cylindrical deception waveguide structure. The present invention achieves effective modulation of the dispersion curves of acoustic vortices with different orbital angular momentum by precisely designing the axial distribution of the groove depth.

[0023] The two-dimensional cross-section of the acoustic device is as follows: Figure 2As shown, the waveguide is made of acoustically rigid materials (such as resin, concrete, stone, glass, etc.), and the medium for each annular groove and the inner diameter of the waveguide is air. The basic unit dimensions of this structure are as follows: annular groove period , width of the annular groove waveguide inner radius outer radius The depth of the annular grooves exhibits a linear gradient distribution along the z-direction. The overall structure comprises 44 annular grooves, arranged in groups of four, for a total of 11 groups. The depth of each group of annular grooves increases linearly from 12mm to 22mm along the direction of sound wave propagation, with an increment of 1mm. The ending position of each group of annular grooves is determined by the formula... Determine (wherein) The total length of the overall gradient annular groove region is 264mm. By installing a probe at the annular groove position and importing the measured sound pressure information into a computer for processing, the input sound vortex can be detected.

[0024] The response of this gradient-groove deep cylindrical deception waveguide structure to a vortex sound source can be obtained by analyzing the dispersion curves at equal groove depths. The sound pressure field P1 in (Region I) The sound pressure field P2 in (Region II) can be expressed as follows:

[0025] (1)

[0026] (2)

[0027] in, , , The amplitude is unknown. For angular variables in cylindrical coordinates, This is the initial phase; ω represents the angular frequency of the sound wave; z represents the z-direction variable in cylindrical coordinates. , These are the radial wave vectors in region I and region II, respectively. Let z be the propagation constant along the z-direction. , , respectively, are the l-th order first and second type Bessel functions; i represents a complex number; r is the radial variable in cylindrical coordinates; t represents the sound wave propagation time.

[0028] The corresponding velocity field along the inner diameter r of the waveguide in region I The corresponding velocity field along the inner diameter r of the waveguide in region II They are respectively:

[0029] (3)

[0030] (4)

[0031] in, It is the mass density of air. It is the radial air equivalent mass density of region II.

[0032] By applying boundary conditions, the dispersion relation of a cylindrical deception waveguide with uniform groove depth is obtained:

[0033] (5)

[0034] in, , These are the first derivatives of the l-th order Bessel functions of the first and second kind with respect to the radial direction.

[0035] To verify the acoustic vortex separation performance of the device of this invention within the operating frequency range, theoretical calculations and simulation experiments were conducted in the 5200Hz to 6000Hz frequency band in this embodiment. For example... Figure 3 As shown, the green, yellow, and red curves (and the sphere) represent orbital angular momentum, respectively. The incident sound vortex. Figure 3 The curve represents the theoretical analytical calculation result, while the sphere represents the COMSOL simulation numerical calculation result. The two show good agreement, verifying the reliability of the design. Within the frequency range of 5200Hz to 6000Hz, acoustic vortices with different orbital angular momentum are successively cut off at different axial positions of the cylindrical structure. As the incident frequency increases from 5200Hz to 6000Hz... The cutoff positions of the acoustic vortices all shift in the direction of decreasing z, meaning the corresponding groove depth gradually becomes shallower. This result indicates that the device designed in this invention can achieve accurate mode separation of acoustic vortices with different orbital angular momentum within this frequency band, and the separation position has good frequency response characteristics, operating effectively in the range of 5200Hz to 6000Hz.

[0036] To further verify the separation performance of the device at a specific frequency, the orbital angular momentum was measured at 5600 Hz. The acoustic vortex response was analyzed. Figure 4 (a) in the text shows trench depth ; trench depth ; trench depth Three dispersion curves are shown. Green, yellow, and red represent acoustic vortices with orbital angular momentum l of 1, 2, and 3, respectively. The curves represent theoretical analytical results, and the rings represent COMSOL simulation numerical calculation results, which are in good agreement. The dispersion curves show that all three curves tend to flatten out at 5600Hz, indicating that at 5600Hz, vortex sound sources with orbital angular momentum l of 1, 2, and 3 will stop at the groove depths of [insert depths here]. The position is determined to achieve effective separation of acoustic vortices. Figure 4 (b) shows the group velocity curves of acoustic vortices with orbital angular momentum of 1, 2, and 3 at a frequency of 5600 Hz. The vertical axis represents the normalized group velocity. (c is the speed of sound in air). When the group velocity At that point, the sound wave stops, that is... The acoustic vortexes will stop at... , , Positioning enables efficient separation of different acoustic vortex modes.

[0037] Figure 5 (a) shows the orbital angular momentum at 5600 Hz. A cross-sectional field diagram of the structure with incident acoustic vortex. The vortex acoustic wave is incident from the left side of the structure. The field diagram shows the orbital angular momentum. The acoustic vortices stopped at... , , The position, this result is consistent with Figure 4 The group velocity curve results shown in (b) are basically consistent. Figure 5 (b) shows the acoustic field mode distribution along the surface of the gradient groove (normalized to its maximum value). From the amplitude modes of the sectional field, we can see the orbital angular momentum. The acoustic vortices stopped at respectively , , The position, and Figure 5 The results shown in (a) are consistent. These results consistently demonstrate that the device designed in this invention possesses excellent spatial separation capability of acoustic vortex modes.

Claims

1. An acoustic device for multimodal vortex separation and detection, characterized in that, The waveguide employs a ring-shaped cylindrical waveguide structure with multiple sets of ring grooves on its inner wall. The depth of each set of ring grooves is linearly increasing along the axial direction. The inner diameter of each set of ring grooves is the same, serving as the inner diameter of the waveguide. The outer diameter of the waveguide is larger than its inner diameter. Probes are installed at each annular groove, and the measured sound pressure information is imported into a computer through the probes; The depth of each group of annular grooves increases linearly along the direction of sound wave propagation; Each group consists of four annular grooves, with the outer diameter of the first group of annular grooves at the acoustic wave input end being the same as the outer diameter of the waveguide; the ending position of each group of annular grooves is determined by the formula... Confirmed, among which , The period is the annular groove.

2. The acoustic device for multimodal vortex separation and detection according to claim 1, characterized in that, The waveguide material can be resin, concrete, stone, or glass; the medium for each set of annular grooves and the inner diameter of the waveguide is air.

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