Dynamic adjustable sound multi-channel selection transmission method based on non-uniform Mie resonance metamaterial

Abstract

The invention designs a non-uniform Mie resonance structure, and according to an isofrequency curve and rotation characteristics of a metamaterial formed by the non-uniform Mie resonance structure when dipole resonance frequency occurs, the isofrequency curve of the non-uniform Mie resonance metamaterial is found to be a hyperbolic curve with great curvature and correspondingly rotates along with different rotation angles of unit structures under the frequency. The general direction of the refraction angle of the sound wave in the material corresponds to the rotation angle of the unit structure, and the angle of the sound wave emitted from the metamaterial is consistent with the angle of the sound wave emitted to the metamaterial. According to the invention, the non-uniform Mie resonance metamaterial capable of dynamically regulating and controlling the propagation of sound waves leftwards, rightwards and forwards and the total reflection of the sound waves in a sound channel is designed, an adjustable sound transmission channel similar to a labyrinth is established, and a single sound wave transmission path can be realized by dynamically changing the rotation angle of the non-uniform Mie resonance structure in the metamaterial; and simultaneous transmission of a plurality of sound waves can be realized.

Description

Technical field:

[0001] The present invention relates to a dynamically adjustable sound multi-channel selective transmission based on a non-uniform Mie resonance metamaterial, belonging to the field of sound wave regulation of metamaterials. Background technology:

[0002] Sound waves can propagate along the waveguide in a straight channel with hard boundaries and keep the wavefront unchanged, but when the waveguide is bent, reflection will occur, which will reduce the sound transmission efficiency and disturb the wavefront. Near-zero refractive index materials can achieve sound wave propagation without amplitude and phase changes in sound channels of any angle and shape due to their super sound transmission efficiency and nearly infinite phase velocity, which is the sound tunneling effect. However, the sound wave steering achieved by traditional zero refractive index materials using the sound tunneling effect can only make the sound wave turn in a specific direction, and cannot achieve dynamic adjustment of the propagation direction of the sound wave in the sound channel, which also limits its practical application to a certain extent, especially the transmission of sound waves between multiple acoustic devices. Of course, the sound wave signal can be converted into an electrical signal for transmission, but that will result in information loss of the sound wave signal, waste of sound wave energy and increase in equipment costs. Therefore, it is necessary to explore new methods to solve the problem of sound wave transmission in multiple channels. Summary of the invention:

[0003] The technical problem to be solved by the present invention is that the sound wave steering achieved by the traditional zero-refractive-index material using the acoustic tunneling effect can only steer the sound wave in a specific direction, and cannot achieve the dynamic adjustment of the propagation direction of the sound wave in the sound channel, which also limits its practical application to a certain extent, especially the transmission of sound waves between multiple acoustic devices. Therefore, the main purpose is to explore an acoustic metamaterial model of a sound channel with a dynamically adjustable transmission route.

[0004] The key technology adopted by the present invention to solve its technical problem is:

[0005] (1) Structural design based on non-uniform Mie resonance

[0006] The wider the channel of the Mie resonance structure, the higher the resonance frequency under the same resonance mode, but the scattering ratio under the resonance mode will increase, thereby improving the transmission performance of the structure. The Mie resonance structure is designed so that each area has the same proportion but the number of bends of the channel in the area is different, which divides the entire structure evenly, increases the symmetry of the structure, and reduces the difficulty of making the structural model. At the same time, the equal division of regions makes it easier for the rotation angles with special acoustic properties to fall at special angles such as 0°, 45°, and 90°, which makes it easier to realize the adjustable characteristics of metamaterials, that is, to control the acoustic properties of metamaterials by the rotation angle of the unit structure.

[0007] (2) Dipole acoustic wave directivity and rotational anisotropy based on the structure

[0008] For the non-uniform Mie resonance structure, it will show different resonance modes under the excitation of sound waves of different frequencies. When the microstructure unit is in the dipole resonance mode, the upper and lower folded space regions and the left and right folded space regions have two different states of dipole resonance, and the frequencies corresponding to the two states are also different. When the sound wave is incident at a certain dipole resonance frequency, the area where the resonance occurs is fixed. Therefore, by rotating the non-uniform Mie resonance structure, the rotation of the resonance area can be achieved, thereby changing the acoustic properties of the metamaterial constructed by it.

[0009] (3) Build a dynamically adjustable sound channel

[0010] An adjustable sound channel composed of a metamaterial and a sound channel wrapped by a hard boundary is designed, which can dynamically adjust the transmission route of the sound channel according to the difference between the transmitting source and the receiving object, and the adjustment is dynamic and does not require the structure and arrangement of the metamaterial to be changed, which can improve the utilization efficiency of the sound channel during multi-device transmission. The four corners of the metamaterial are connected to the four corners of the junction, which can prevent sound waves from leaking from the gaps in the four corners to the external space and reduce the sound loss during the transmission process.

[0011] The beneficial effects of the present invention are:

[0012] Since the present invention designs a non-uniform Mie resonance structure with sub-wavelength size, an adjustable sound channel is constructed by using the directional response characteristics and rotational anisotropy of its dipole resonance. On this basis, an adjustable sound channel consisting of 3×3 metamaterials and 6 intersecting hard boundary sound channels is constructed. In addition to realizing a single sound wave transmission route, multiple channels can also transmit sound waves simultaneously.

[0013] (1) Since the present invention designs a non-uniform Mie resonance structure metamaterial, sound waves can be regulated at sub-wavelength scale. Compared with the traditional zero-refractive index method of using acoustic tunneling effect to achieve sound wave steering, the non-uniform Mie resonance structure has unique advantages in size and reconfigurability.

[0014] (2) Compared with traditional acoustic metamaterials with relatively fixed acoustic parameters, the metamaterial designed in the present invention has dynamic adjustability and can dynamically adjust the rotation angle of the microstructure according to demand, thereby changing the refraction angle of the sound wave.

[0015] (3) In addition to realizing a single channel transmission route, the sound channel constructed by the present invention can also realize multiple channels to transmit sound waves simultaneously without causing obvious interference. Description of the drawings:

[0016] Figure 1 Schematic diagram of the inhomogeneous Mie resonance structure;

[0017] Figure 2 (a) Isofrequency curve of air at 794 Hz, (b) rotation angle The isofrequency curves of the non-uniform Mie resonance metamaterial near the frequency of 794 Hz;

[0018] Figure 3 (a) Isofrequency curve of air at 794 Hz, (b) rotation angle The isofrequency curves of the non-uniform Mie resonance metamaterial near the frequency of 794 Hz;

[0019] Figure 4 (a) Isofrequency curve of air at 794 Hz, (b) rotation angle The isofrequency curves of the non-uniform Mie resonance metamaterial near the frequency of 794 Hz;

[0020] Figure 5 (a) Isofrequency curve of air at 794 Hz, (b) rotation angle The isofrequency curves of the non-uniform Mie resonance metamaterial near the frequency of 794 Hz;

[0021] Figure 6 When a plane wave is incident from the left acoustic channel, the rotation angle of the metamaterial (a) (b) (c) and (d) The sound pressure field distribution diagram under ;

[0022] Figure 7 (a) Rotation angle The sound pressure field distribution diagram when the incident wave exists in the left and lower sound channels of the metamaterial at the same time, (b) the rotation angle When , the sound pressure field distribution diagram of the incident wave exists simultaneously in the left and upper sound channels of the metamaterial;

[0023] Figure 8 The sound pressure field distribution diagram of the plane wave being incident from end A and exiting from end H, and incident from end B and exiting from end G.

[0024] Fig. 9 The sound pressure field distribution diagram when the two sound transmission paths of plane wave are connected: incident from end A and emitted from end H, and incident from end B and emitted from end G. Specific implementation method:

[0025] The preferred implementation scheme of the dynamically adjustable acoustic multi-channel selective transmission based on the inhomogeneous Mie resonance metamaterial of the present invention is described in detail below with reference to the accompanying drawings. Figures 1 to 9The specific implementation method of the dynamically adjustable acoustic multi-channel selective transmission based on the non-uniform Mie resonance metamaterial is demonstrated. In order to make the features and advantages of this patent more obvious and easy to understand, the following embodiments are specifically cited and explained in detail as follows:

[0026] S1 Design of non-uniform Mie structure metamaterials: design of microstructure units based on factors such as wall thickness, air channel width, number of bends, inner and outer circle radii, opening width and orientation, and proportion;

[0027] S2 uses the characteristic frequency research of COMSOL Multiphysics to analyze the designed microstructure and analyze the special modal frequency of the microstructure. The present invention mainly uses the dipole mode of the microstructure. Under this mode, the microstructure has a strong anisotropic characteristic.

[0028] S3 analyzes the isofrequency curve of the metamaterial at the frequency analyzed by S2, finds the special rotation angle, and uses the isofrequency surface theory to analyze the relationship between the structural rotation angle and the sound wave refraction angle;

[0029] S4 uses metamaterials and hard-boundary wrapped sound channels to form an adjustable sound channel. By dynamically changing the rotation angle of the non-uniform Mie resonance structure in the metamaterial, the sound transmission route in the channel can be changed, thereby achieving dynamically adjustable sound multi-channel selective transmission.

[0030] Figure 1 Schematic diagram of the non-uniform Mie resonance structure. The basic unit cancels the square air domain with its upper and lower hard boundaries and is only composed of the non-uniform Mie resonance structure. The non-uniform Mie resonance structure as a whole is composed of four fan-shaped folded space regions and a hollow circle in the center. Its anisotropy is reflected in the different bending times of the four folded space regions while the area accounts for the same proportion. The bending times of the upper and lower folded spaces are 8, and the bending times of the left and right folded spaces are 4. The four regions divide the entire structure equally, each accounting for 1 / 4 of the total.

[0031] Figure 2 It is the equal frequency curve when the rotation angle of the non-uniform Mie resonance structure is 0 degrees. Figure 2 As shown by the black arrow in (a), the normal is perpendicular to the interface between the air and the metamaterial composed of the inhomogeneous Mie resonance structure. According to the isofrequency surface theory, it can be determined that the directions of the sound waves in the metamaterial in these two cases are v and g1 and v g2 ,like Figure 2As shown by the black arrows in (b), it can be found that since the 794Hz isofrequency curve is approximately a straight line and has an angle of about 135° with the x-axis, the refraction angles of the two sound waves are both about 45°, and the deviation from 45° is small, and positive refraction and negative refraction occur respectively. Similarly, when the sound wave is incident at 0°, the refraction angle of the sound wave is also about 45°.

[0032] Figure 3 (a) and 3(b) show the isofrequency curve of air at 794 Hz and the isofrequency curve of the inhomogeneous Mie resonant metamaterial near 794 Hz when the unit structure is rotated by 90°. Compared with the case where the rotation angle is 0°, this is equivalent to the incident interface rotating by 90°. Therefore, the isofrequency curve at 794 Hz (black solid line) also rotates by about 90°. i1 and θ i2 When the sound wave is incident from air to the metamaterial, according to the equal frequency surface theory, the refraction direction of the sound wave will also rotate to -45° accordingly, such as Figure 3 The black arrow v in (b) g1 and v g2 shown.

[0033] Figure 4 As shown in (b), at that time, the isofrequency curve of the metamaterial at a frequency of 794 Hz is a hyperbola (black solid line) located on both sides of the y-axis, and the curvature of the hyperbola is reduced compared to the case where the rotation angle is 0°. i1 and θ i2 When the sound wave is incident from air to the metamaterial, according to the isofrequency surface theory, the refraction angle of the sound wave is about 0°. However, due to the increase in the curvature of the isofrequency curve, the deviation between the refraction angle and the 0° angle is more obvious. Figure 4 The black arrow v in (b) g1 and v g2 shown.

[0034] Figure 5 As shown in (b), when the rotation angle is 43.1°, the isofrequency curve of the inhomogeneous Mie resonant metamaterial near the frequency of 794 Hz is rotated by 90° compared with the isofrequency curve at 794 Hz. At this time, the isofrequency curve at 794 Hz (black solid line) is almost parallel to the x-axis. Figure 5 (a) is the isofrequency curve of air at a frequency of 794 Hz. If the incident sound wave vector with a small or large incident angle cannot intersect with the isofrequency curve of the metamaterial, the sound wave cannot propagate in the metamaterial and total reflection will occur.

[0035] Figure 6(a)-6(d) shows the distribution of the sound pressure field when the rotation angles of the metamaterial are 0°, 90°, -46.9° and 43.1°. It is found that when the rotation angle of the metamaterial is 0°, the sound wave is deflected and propagated in the metamaterial in the upward direction of 45° and is transmitted to the upper sound channel perpendicular to the left boundary of the metamaterial. The sound wave propagates in the upper sound channel along the +y direction and the plane wave remains basically intact. At this time, the sound pressure amplitude in the right and lower sound channels is very small and close to 0Pa, as shown in Figure 6 (a) When the rotation angle of the metamaterial is 90°, the sound wave is deflected and propagated downward at -45° and is transmitted perpendicularly to the left boundary of the metamaterial to the lower sound channel. The sound wave is emitted in the lower sound channel along the -y direction and the plane wave remains basically intact. At this time, the sound pressure amplitude in the right and upper sound channels is very small and close to 0Pa, as shown in Figure 6 (b) When the rotation angle of the metamaterial is -46.9°, the propagation direction of the sound wave does not deflect in the metamaterial and is perpendicular to the left boundary of the metamaterial and is transmitted to the right boundary. The sound wave propagates along the +x direction in the right sound channel and the plane wave remains basically intact. At this time, the sound pressure amplitude in the upper and lower sound channels is very small and close to 0Pa, as shown in Figure 6 (c) When the rotation angle of the metamaterial is 43.1°, the sound wave is totally reflected and cannot enter the metamaterial. Figure 6 (d) as shown.

[0036] Figure 7 (a) shows the sound pressure field distribution diagram when the rotation angle is 0° and sound waves are incident on the left and lower sound channels of the metamaterial at the same time, where the phase difference between the incident sound wave on the left and the incident sound wave on the lower side is π. It can be found that both sound waves can be propagated and deflected, and the waveform remains intact, the sound wave phase difference is consistent with that at the time of incidence, and there is almost no sound wave interference except for the diagonal area of ​​the metamaterial. Similarly, Figure 6 (d) When the sound wave is totally reflected in the left sound channel, there is almost no sound wave transmission in the metamaterial. At this time, the upper and lower sound channels can realize the forward propagation of sound waves. Figure 7 (b) shows the sound pressure field distribution diagram when the left and upper sound channels of the metamaterial are simultaneously incident with sound waves when the rotation angle is 43.1°, where the phase difference between the incident sound wave on the left and the incident sound wave on the upper side is also π. The sound wave is incident from the upper sound channel along the -y direction and exits from the lower sound channel along the -y direction, and the waveform remains intact. Therefore, the designed adjustable sound channel has a certain degree of multiplexing, which can simultaneously regulate sound waves from two directions and ensure that the sound waves in the two transmission directions are independent of each other and do not interfere with each other, thereby improving the utilization rate of the metamaterial.

[0037] Figure 8The sound pressure field distribution diagram is shown when a plane wave is simultaneously transmitted along two sound transmission routes: incident from end A and emitted from end H, and incident from end B and emitted from end G. It can be seen that both sound waves can propagate along the designed transmission routes and maintain good waveforms. Except for these two transmission routes, the sound pressure amplitude in the sound channel is very small and close to 0Pa.

[0038] Fig. 9 The sound pressure field distribution diagram when two sound transmission paths meet is shown. One path is incident from end A and emitted from end H, and the other path is incident from end B and emitted from end G. The two sound transmission paths meet at the center of the metamaterial. It can be found that the shapes and distances of the two transmission paths are the same, so the sound wave waveforms of the two transmission paths are basically the same. Figure 8 The waveforms of the transmission route from end B to end G are also basically the same, which proves that even if the same metamaterial is used in the two sound wave transmission routes, there will be almost no interference.

Claims

1. A method for realizing dynamic adjustable sound multi-channel selective transmission using a non-uniform Mie resonance structure, characterized in that: The following steps are involved: Step 1: Design a cylindrical non-uniform Mie resonance metamaterial and set various physical parameters; Step 2: Analyze the designed microstructure using the eigenfrequency study of COMSOL Multiphysics; Step 3: Analyze the refractive properties of the Mie resonance structure at different rotation angles; Step 4: Build a sound channel wrapped with metamaterials and hard boundaries to achieve dynamically adjustable sound multi-channel selective transmission.

2. The method for realizing dynamic adjustable sound multi-channel selective transmission based on non-uniform Mie resonance structure according to claim 1, characterized in that: In Step 1, relevant microstructure units are designed by considering factors such as wall thickness, air channel width, number of bends, inner and outer circle radii, opening width and orientation, and proportion.

3. The method for realizing dynamic adjustable sound multi-channel selective transmission based on non-uniform Mie resonance structure according to claim 1, characterized in that: In step 2, the special modal frequency of the microstructure is analyzed. The present invention mainly uses the dipole resonance mode of the microstructure. Under this mode, the microstructure has a strong anisotropic characteristic.

4. The method for realizing dynamic adjustable sound multi-channel selective transmission based on non-uniform Mie resonance structure according to claim 1, characterized in that: In step 3, the dipole resonance frequency sound wave analyzed in step 2 is used for excitation, and the relationship between the structural rotation and the sound wave refraction angle is analyzed using the principle of equal frequency surfaces.

5. The method for realizing dynamic adjustable sound multi-channel selective transmission based on non-uniform Mie resonance structure according to claim 1, characterized in that: The adjustable sound channel is composed of the non-uniform Mie resonance metamaterial and the sound channel wrapped by the hard boundary. The rotation angle of the non-uniform Mie resonance structure is adjusted to refract the sound waves in different directions, thereby realizing dynamically adjustable sound multi-channel selective transmission.

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