A directional sound source system and a directional adjusting method using metamaterials

Abstract

The application provides a directional sound source system and a directional adjusting method using a metamaterial, which comprises a non-directional sound source and a directional device, a double-layer fan ring cavity penetrating through a cylinder is arranged in the cylinder to obtain a directional sound source device in the form of a double-layer curved surface resonator; then, a multi-resonator coupling cylinder structure is used to control sound waves, a resonance mode in which a cylinder structure monopole mode and a cylinder structure dipole mode are coupled with each other is activated in a lower frequency range, the resonance mode of the cylinder structure excited by the sound source is coupled with the sound source to interact with each other, so that the sound waves have energy in a specified direction and are cancelled in the remaining directions, thereby realizing the super directivity of the sound source at a far field position and providing a condition for preparing a directional sound source.

Description

Technical Field

[0001] This invention belongs to the field of acoustics technology, and in particular relates to a directional sound source system and a directional adjustment method using metamaterials. Background Technology

[0002] Parametric acoustic arrays use modulation and envelope squaring to modulate audio signals onto high-frequency (ultrasonic) carrier signals, and then use ultrasonic transducers to transmit the modulated signals to achieve strong directivity. However, they are complex in design, manufacturing and operation. Loudspeaker arrays achieve strong directivity by controlling the ratio of the array element spacing to the wavelength and using super-directive beamforming. However, the array size is often large and the design and manufacturing are more complex. Summary of the Invention

[0003] To address the aforementioned problems, this invention provides a directional sound source system and a directional adjustment method utilizing metamaterials, which enables sound waves to have energy only in a specified direction, while all other directions are canceled out, thereby achieving superdirectivity of the sound source at a far-field location.

[0004] A directional sound source system utilizing metamaterials includes an omnidirectional sound source and a directional device. The directional effect of the directional device varies with the distance between the omnidirectional sound source and the directional device, achieving super-directionality of the omnidirectional sound source in a set direction. The directional device is a cylindrical structure with a double-layered fan-ring cavity penetrating the cylinder. When the number of fan-ring cavities is double, there are eight fan-ring cavities inside the cylinder. These eight cavities consist of four inner fan-ring cavities and four outer fan-ring cavities superimposed on the inner fan-ring cavities. Each arc-shaped sidewall of the double-layered fan-ring cavity has a slit penetrating the cylinder, which serves as a throat. Each set of double-layered fan-ring cavities formed by the superposition of inner and outer fan-ring cavities serves as a double-layered curved resonator. The inner and outer fan-ring cavities belonging to the same set of double-layered fan-ring cavities have the same cavity angle, and the angle corresponding to the position of the throat is also the same.

[0005] Furthermore, when the number of fan-ring cavities is double, the depth, throat width, and throat depth of each double-layer fan-ring cavity satisfy the following relationship:

[0006] α2=2*arcsin(0.55 / (1-D2))

[0007] β2 = 2*arcsin(D1)

[0008] R i1 =1-D2*2-L i1 -L i2

[0009] R i2=1-D2*2-L i1

[0010] R i3 =1-D2-L i1

[0011] R i4 =1-D2

[0012] R i5 =1

[0013] Where α2 is the cavity opening angle of the current double-layered sector annulus cavity, β2 is the laryngeal opening angle of the current double-layered sector annulus cavity, D1 is the laryngeal width of the current double-layered sector annulus cavity, D2 is the laryngeal depth of the current double-layered sector annulus cavity, and L i1 L represents the cavity depth of the inner fan-ring cavity in the current double-layer fan-ring cavity. i2 R represents the cavity depth of the outer fan-ring cavity in the current double-layer fan-ring cavity. i1 R is the radius of the circle to which the bottom arc of the inner fan ring cavity in the current double-layer fan ring cavity belongs. i2 R is the radius of the circle to which the bottom arc of the throat of the inner sector ring cavity in the current double-layer sector ring cavity belongs. i3 R is the radius of the circle to which the top arc of the throat of the inner sector ring cavity in the current double-layer sector ring cavity belongs. i4 R is the radius of the circle to which the bottom arc of the throat of the outer sector annulus in the current double-layer sector annulus cavity belongs. i5 It is the radius of the circle to which the top arc of the throat of the outer sector ring cavity in the current double-layer sector ring cavity belongs.

[0014] Furthermore, the dimensions of each sector ring cavity are not exactly the same. The dimensions of each sector ring cavity, the distance between the omnidirectional sound source and the directional device are obtained by particle swarm optimization algorithm. In the optimization process, the objective function is that the directional factor E in the direction of the set angle of the directional device is greater than the set value.

[0015] Furthermore, when the number of layers in the fan ring cavity is double, the angles corresponding to the setting positions of the throat tubes in each group of double-layer fan ring cavities are 0, π / 2, π, and 3π / 2, respectively.

[0016] A method for adjusting the directivity of a directional sound source system using metamaterials, comprising the following steps:

[0017] Initial values ​​are set for the combination of dimensional parameters of each sector cavity, the distance between the omnidirectional sound source and the directional device. The combination of dimensional parameters includes the cavity opening angle, the throat opening angle, the throat width, the throat depth, the cavity depth, the radius of the circle to which the bottom arc of the cavity belongs, the radius of the circle to which the bottom arc of the throat belongs, and the radius of the circle to which the top arc of the throat belongs.

[0018] Substituting the initial values ​​of the dimensional parameter combination into the sound pressure wave equation, acoustic boundary conditions, and impedance transfer formula corresponding to each double-layer curved surface resonator, we obtain the acoustic impedance of each double-layer curved surface resonator at different radii in various angular directions.

[0019] Based on the acoustic impedance of each double-layer curved surface resonator at different radii in various angular directions, the incident wave sound pressure and scattered wave sound pressure of each double-layer curved surface resonator in various angular directions are obtained.

[0020] Based on the incident wave sound pressure and scattered wave sound pressure of each double-layer curved surface resonator in each angular direction, the directivity factor E of the directivity device in each angular direction is obtained.

[0021] Determine whether the directivity factor E in the set angle direction of the directivity device is greater than the set value. If yes, the sound source directivity adjustment of the directivity device is completed. If no, the particle swarm optimization algorithm is used to update the combination of size parameters of each sector cavity, the distance between the non-directional sound source and the directivity device, and then the updated values ​​are used to re-obtain the directivity factor E of the directivity device in each angle direction until the directivity factor E in the set angle direction of the directivity device is greater than the set value, and the sound source directivity adjustment of the directivity device is completed.

[0022] Furthermore, when the size parameters of each sector ring cavity are fixed, the directional effect of the directional device is optimal when the difference between the distance between the non-directional sound source and the directional device and the diameter of the cylindrical structure is less than a set threshold.

[0023] Beneficial effects:

[0024] 1. This invention provides a directional sound source system realized using metamaterials, including an omnidirectional sound source and a directional device. A double-layer fan-shaped cavity is set inside a cylinder, forming a directional device in the form of a double-layer curved resonator. Then, the sound waves are modulated by coupling the cylindrical structure with multiple resonators, activating the resonant modes of the cylindrical structure's monopole mode and dipole mode in a lower frequency range. The resonant modes of the cylindrical structure excited by the sound source are coupled and interact with the sound source itself, so that the sound waves have energy only in a specified direction, while the energy in other directions is canceled out, thereby realizing the superdirectivity of the sound source at the far field position, providing conditions for the preparation of directional sound sources.

[0025] 2. This invention provides a directional sound source system implemented using metamaterials. By selecting the particle swarm optimization algorithm to solve for the parameters of the resonator, the distance between the non-directional sound source and the directional device, the optimal design parameters of the directional sound source system can be obtained. After obtaining the optimized parameters of the directional sound source system, a model is built in simulation software, and the directional effect of the directional device is calculated. Experiments show that the double-layer curved surface resonator can achieve good directivity.

[0026] 3. This invention provides a method for adjusting the directivity of a sound source. Under different conditions regarding the size of each sector cavity, the distance between the non-directional sound source and the directive device, the acoustic impedance of the directive device is obtained. Then, sound pressure data is obtained based on the acoustic impedance. Finally, the directivity factor E of the directive device in each direction is obtained based on the sound pressure data. If the directivity factor E at a specified location does not meet the requirements, a particle swarm optimization algorithm is used to re-optimize the size of each sector cavity of the directive device, the distance between the non-directional sound source and the directive device, thereby achieving the adjustment of the sound source directivity of the directive device. This method can obtain the required directivity at any angle and has a wide range of applications. Attached Figure Description

[0027] Figure 1 A schematic diagram illustrating the principle of the directional sound source system utilizing metamaterials provided by this invention;

[0028] Figure 2 A schematic diagram of the arrangement of the directional sound source system utilizing metamaterials provided by the present invention;

[0029] Figure 3 A two-dimensional schematic diagram of the directional device formed by the double-layer curved surface resonator coupled to the cylindrical structure provided by the present invention;

[0030] Figure 4 A schematic diagram of the dimensions of the double-layer curved surface resonator provided by the present invention;

[0031] Figure 5 A schematic diagram showing the location for calculating the acoustic impedance of the double-layer curved surface resonator provided by the present invention. Detailed Implementation

[0032] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings.

[0033] It should be noted that in traditional techniques, when using resonators for resonance, rectangular resonators are usually embedded in a cylinder. However, if a conventional rectangular resonator is used, it will introduce a large error when determining the position parameters of the resonator. Based on this, the present invention uses a curved resonator set inside the cylindrical structure. Specifically, the present invention selects the curved resonator inside the cylindrical structure as a single-layer and a double-layer structure, and performs theoretical derivation and simulation experiments to verify these two structures respectively.

[0034] Specifically, such as Figure 1As shown, a directional sound source system utilizing metamaterials includes a non-directional sound source and a directional device, wherein the directional effect of the directional device varies with the distance d between the non-directional sound source and the directional device, as shown. Figure 2 As shown, an omnidirectional sound source can be arranged on the right side of the directional device. By placing the two at a relative distance d, the super-directionality of the sound source is achieved. The directional device is a cylindrical structure, with a double-layered fan-shaped cavity penetrating the cylinder. Figure 3 As shown, when the number of fan-ring cavities is double-layered, there are eight fan-ring cavities inside the cylinder. These eight fan-ring cavities consist of four inner fan-ring cavities and four outer fan-ring cavities superimposed on the inner fan-ring cavities. Each arc-shaped sidewall of the double-layered fan-ring cavities has a slit that penetrates the cylinder, and this slit serves as a throat. Each set of double-layered fan-ring cavities formed by the superposition of inner and outer fan-ring cavities serves as a double-layered curved surface resonator. The inner and outer fan-ring cavities belonging to the same set of double-layered fan-ring cavities have the same cavity opening angle, and the angle corresponding to the position of the throat is also the same. The angles corresponding to the position of the throat on each set of double-layered fan-ring cavities are 0, π / 2, π, and 3π / 2, respectively.

[0035] It should be noted that the dimensions of each sector ring cavity are not exactly the same. The dimensions of each sector ring cavity, the distance between the omnidirectional sound source and the directional device are obtained by particle swarm optimization algorithm. In the optimization process, the objective function is that the directional factor E in the direction of the set angle of the directional device is greater than the set value. The directional factor, like the directionality, is a characterization of the directional strength of the sound pressure signal. The larger the directional factor, the stronger the directionality of the directional device, which means that the sound energy emitted by the directional device is more concentrated in a certain direction.

[0036] Furthermore, such as Figure 4 As shown, the directional device consists of a cylinder and four double-layered curved surface resonators evenly arranged inside the cylinder. The angle of the i-th (1≤i≤4) double-layered curved surface resonator corresponding to the cylinder is φ. i (respectively 0, π / 2, π, 3π / 2), and the parameter settings for the double-layer curved surface resonator are as follows:

[0037] The center of the cylindrical structure coincides with the origin of the coordinate system. The parameters of the four double-layer curved surface resonators inside the cylindrical structure are set as follows: the depths of the two cavities of the curved surface resonator at the 0° position are set to L respectively. 11 L 12 , where L 11 L is the cavity depth parameter near the surface of the cylindrical structure. 12 The depth parameter of the cavity near the center of the cylindrical structure; the depths of the two cavities of the curved resonator at a position rotated 90° counterclockwise are respectively set to L.21 L 22 , where L 21 L is the cavity depth parameter near the surface of the cylindrical structure. 22 The depth parameter is the cavity depth near the center of the cylindrical structure; the depths of the two cavities of the curved resonator at a position rotated 180° counterclockwise are respectively set to L. 31 L 32 , where L 31 L is the cavity depth parameter near the surface of the cylindrical structure. 32 The depth parameter of the cavity near the center of the cylindrical structure; the depths of the two cavities of the curved resonator at a position rotated 270° counterclockwise are respectively set as L. 41 L 42 , where L 41 L is the cavity depth parameter near the surface of the cylindrical structure. 42 For the cavity depth parameters near the center of the cylindrical structure, the above eight depth parameters all range from 0 to 0.4. The ranges for these parameters and the following parameters are dimensionless normalized values. At this point, the sound source can be placed on the negative y-axis. The throat angle and cavity angle are optimized using the throat width and throat depth, respectively. The throat width parameter is set to D1, with a range of 0.07-0.125, and the throat depth parameter is set to D2, with a range of 0.05-0.09.

[0038] Based on the above-mentioned parameters, the required optimization parameters can be obtained by solving the following formula:

[0039] α2=2*arcsin(0.55 / (1-D2))

[0040] β2 = 2*arcsin(D1)

[0041] R i1 =1-D2*2-L i1 -L i2

[0042] R i2 =1-D2*2-L i1

[0043] R i3 =1-D2-L i1

[0044] R i4 =1-D2

[0045] R i5 =1

[0046] Where α2 is the cavity opening angle of the current double-layered sector annulus cavity, β2 is the laryngeal opening angle of the current double-layered sector annulus cavity, D1 is the laryngeal width of the current double-layered sector annulus cavity, D2 is the laryngeal depth of the current double-layered sector annulus cavity, and L i1 L represents the cavity depth of the inner fan-ring cavity in the current double-layer fan-ring cavity. i2 R represents the cavity depth of the outer fan-ring cavity in the current double-layer fan-ring cavity. i1 R is the radius of the circle to which the bottom arc of the inner fan ring cavity in the current double-layer fan ring cavity belongs. i2 R is the radius of the circle to which the bottom arc of the throat of the inner sector ring cavity in the current double-layer sector ring cavity belongs. i3 R is the radius of the circle to which the top arc of the throat of the inner sector ring cavity in the current double-layer sector ring cavity belongs. i4 R is the radius of the circle to which the bottom arc of the throat of the outer sector annulus in the current double-layer sector annulus cavity belongs. i5 Let be the radius of the circle to which the top arc of the throat of the outer sector annulus in the current double-layer sector annulus cavity belongs. When solving for the cavity opening angle α2 and throat opening angle β2 using the throat depth and width parameters, a certain approximation condition is used: when the angle θ is very small, sin(θ) = θ.

[0047] Based on the optimized parameters, single-layer and double-layer resonators were designed and fabricated, and the experimental environment was set up. Then, sound pressure data was collected at the designated location of the directional device using a microphone and other acquisition equipment. The collected sound pressure signals were processed using a signal processing program to obtain the directional results around the directional device.

[0048] Based on the above-mentioned directional device utilizing metamaterials, the present invention also provides a method for adjusting the directionality of a sound source, comprising the following steps:

[0049] S1: Set initial values ​​for the combination of dimensional parameters of each sector ring cavity, the distance between the omnidirectional sound source and the directional device, wherein the combination of dimensional parameters includes the cavity opening angle, the throat opening angle, the throat width, the throat depth, the cavity depth, the radius of the circle to which the bottom arc of the cavity belongs, the radius of the circle to which the bottom arc of the throat belongs, and the radius of the circle to which the top arc of the throat belongs.

[0050] S2: Substitute the initial values ​​of the combination of size parameters into the sound pressure wave equation, acoustic boundary conditions and impedance transfer formula corresponding to each double-layer curved surface resonator to obtain the acoustic impedance of each double-layer curved surface resonator at different radii in various angular directions.

[0051] S3: Based on the acoustic impedance of each double-layer curved surface resonator at different radii in various angular directions, obtain the incident wave sound pressure and scattered wave sound pressure of each double-layer curved surface resonator in various angular directions.

[0052] It should be noted that obtaining the incident wave sound pressure and the scattered wave sound pressure based on acoustic impedance is a common method, and this invention will not elaborate on it.

[0053] S4: Based on the incident wave sound pressure and scattered wave sound pressure of each double-layer curved surface resonator in each angular direction, obtain the directivity factor E of the directivity device in each angular direction.

[0054] The directionality factor E is calculated as follows:

[0055]

[0056] Where, p k p represents the sound pressure data at the k-th (1≤k≤360) sampling point. max This represents the maximum sound pressure level among 360 sampling points. Assuming the objective of this invention is to obtain maximum directivity in the 0° direction, then p... k 2 The maximum value should be obtained when k=1.

[0057] S5: Determine whether the directivity factor E in the set angle direction of the directivity device is greater than the set value. If yes, the sound source directivity adjustment of the directivity device is completed. If no, the particle swarm optimization algorithm is used to update the combination of size parameters of each sector ring cavity, the distance between the non-directional sound source and the directivity device, and then the updated values ​​are used to re-obtain the directivity factor E of the directivity device in each angle direction until the directivity factor E in the set angle direction of the directivity device is greater than the set value, and the sound source directivity adjustment of the directivity device is completed.

[0058] It should be noted that when the size parameters of each sector ring cavity are fixed, the directional effect of the directional device is optimal when the difference between the distance between the non-directional sound source and the directional device and the diameter of the cylindrical structure is less than a set threshold.

[0059] It should be noted that in deriving the theoretical expression for the acoustic impedance at the throat opening, the impedance transfer formula can be directly applied to the throat portion of the resonator, but this formula cannot be directly applied to the cavity portion of the resonator because its internal higher-order modes need to be considered. To solve for its acoustic impedance, the following section uses a double-layered curved surface resonator as an example to introduce the basic principles of this invention for calculating the acoustic impedance of a double-layered curved surface resonator using methods such as continuous sound pressure and continuous volume velocity boundary conditions:

[0060] First, assume r1 is the distance from the bottom of cavity 1 to the center of the cylinder, i.e. Figure 5 The distance between the first black arc on the left and the origin O, r2 is the distance from the top of cavity 1 to the center of the cylinder, i.e. Figure 5The distance between the second black arc from the left and the origin O, r3 is the distance from the top of throat 2 to the center of the cylinder, i.e. Figure 5 The distance between the third black arc from the left and the origin O, r4 is the distance from the top of cavity 3 to the center of the cylinder, i.e. Figure 5 The distance between the fourth black arc from the left and the origin O, r5 is the distance from the top of the throat 4 to the center of the cylinder, i.e. Figure 5 The distance between the fifth black arc on the left and the origin O is equal to the radius r0 of the cylinder's base. The central angles of the two cavities 1 and 3 are equal, denoted as α. The central angles of the two tracheae 2 and 4 are equal, denoted as β.

[0061] The fundamental equation for sound pressure in a cylindrical structure is as follows:

[0062]

[0063] p(r) is the sound pressure at radius r, where r ranges from [r1, r5], k is the wave number, and φ represents the angle of the throat on the cylinder.

[0064] Acoustic boundary conditions:

[0065] p1 = p2

[0066] v1S1=v2S2

[0067] p1 and p2 are the sound pressures on both sides of the interface; v1S1=v2S2 is the continuous boundary condition for volume velocity, v1 and v2 are the sound velocities on both sides of the interface, and S1 and S2 are the cross-sectional areas on both sides of the interface.

[0068] Separate the variables from equation (2-1) and let...

[0069]

[0070] Among them, P m (r) represents the sound pressure levels of different orders, F n (r) is a function that includes a distance variable, ψ n (φ,φ m ) is a constant containing the angle variable, φ m Here, n represents the order of the angle variable, and m represents the sound pressure order.

[0071] Substituting equation (2-2) into equation (2-1), we obtain two independent ordinary differential equations.

[0072]

[0073]

[0074] Ψn (φ,φ m The following boundary conditions must be met:

[0075]

[0076] Solving the above formula yields...

[0077]

[0078]

[0079] Where, η n For different orders of sound wavefront coefficients, and A ηn B is the first variable with undetermined coefficients. ηn H is the second variable to be determined. ηn (kr) is the Hankel function at position r. H is the first derivative of the Hankel function at position r. ηn (kr1) is the Hankel function at position r1. H is the first derivative of the Hankel function at position r1. ηn (kr2) is the Hankel function at position r2. J is the first derivative of the Hankel function at position r2. ηn (kr) is the Bessel function at position r, δ 0n It is a delta function;

[0080] When r1 < r < r2, the sound pressure p inside the cavity m (r) and velocity v mr Satisfy the following equation

[0081]

[0082]

[0083] Where ρ is the air density and ω is the angular frequency;

[0084] Considering the rigid boundary conditions at the bottom of the cavity, the velocity at the bottom of the cavity is 0, satisfying the expression

[0085]

[0086] Among them, Ψ is used n (φ,φ m The orthogonality of ) can be obtained

[0087]

[0088] Substituting the velocity continuity boundary condition at r = r2 and simplifying, we get...

[0089]

[0090] Where c is the speed of sound in air, U throat_r The volume velocity at the location of the larynx;

[0091] Solving equations (2-11) and (2-12) simultaneously yields the auxiliary coefficient A. ηn B ηn

[0092]

[0093]

[0094] Equation Z a (r2) represents the acoustic impedance at r = r2.

[0095]

[0096] in, This represents the average sound pressure level at the throat.

[0097] Equation (2-1) for sound pressure wave also applies to the larynx, as follows:

[0098]

[0099] Based on the above equation, assuming that the sound field in the throat has a weak dependence on angle, the equations satisfying the sound pressure and sound velocity in the throat can be simplified to the following form.

[0100]

[0101]

[0102] Where A is the first coefficient, B is the second coefficient, J0(kr) is the 0th-order Bessel function at position r, and J1(kr) is the 1st-order Bessel function at position r. Let r be the first derivative of the 0th-order Hankel function at position r3. The first derivative of the 0th order Hankel function at position r2. Let r be the first derivative of the 0th order Hankel function at position r;

[0103] Based on the expression of acoustic impedance in the larynx

[0104] Substitute (2-17) and (2-18) into the above equation

[0105]

[0106]

[0107] Z a (r2) represents the acoustic impedance at r = r2, Z a (r3) represents the acoustic impedance at r = r3, ρ is the density of the medium, c is the sound velocity in the medium, and k is the sound wave number. The first derivative of the first-order Hankel function at position r2. J0(kr2) is the first derivative of the first-order Hankel function at position r3, J1(kr2) is the 0th-order Bessel function at position r2, J0(kr3) is the 0th-order Bessel function at position r3, and J1(kr3) is the 1st-order Bessel function at position r3.

[0108] The acoustic impedance Z can be obtained by combining (2-19) and (2-20). a (r3)

[0109]

[0110] Based on equations (2-8) and (2-12)

[0111] At r = r3, the sound pressure and volume velocity satisfy the following equations.

[0112]

[0113]

[0114] in, C represents the average sound pressure at position r3. ηn D is an undetermined coefficient. ηn Let ψ be an undetermined coefficient. n' (φ,φ m U is an angle function that includes an angle variable. throat_r3 The volume velocity at position r3. The first derivative of the Hankel function at position r3. The first derivative of the Hankel function at position r4;

[0115] At r = r4

[0116]

[0117] in, U is the average sound pressure at position r4. throat_r4 The volume velocity at position r4;

[0118] Combine equations (2-22)-(2-25) into a single system, and according to... At r = r4, the acoustic impedance Z aThe expression for (r4) is as follows:

[0119]

[0120] in

[0121]

[0122] Among them, AA n BB is the first auxiliary variable. n CC is the second auxiliary variable. n As the third auxiliary variable, DD n The fourth auxiliary variable; the number of 'n' for each auxiliary variable remains consistent, representing the sound wave order.

[0123] In the throat section where r4 < r < r5, according to the impedance transfer formula (2-21), the acoustic impedance Z at the top of the upper throat at r = r5 is... a The expression for (r5) is as follows:

[0124]

[0125] in, Let r5 be the first derivative of the 0th order Hankel function. Let r be the first derivative of the 0th order Hankel function at position r4. The first derivative of the first-order Hankel function at position r4. J1(kr4) is the first derivative of the first-order Hankel function at position r5, J1(kr5) is the first derivative of the first-order Bessel function at position r4, J0(kr4) is the first derivative of the first-order Bessel function at position r5, and J0(kr5) is the first derivative of the first-order Bessel function at position r4.

[0126] Thus, the present invention obtains as follows Figure 5 The acoustic impedance at the five black arcs shown can be obtained similarly for the acoustic impedance at the other positions of the directional device, and will not be elaborated further in this invention.

[0127] In summary, this invention utilizes a multi-resonator coupled cylindrical structure to modulate sound waves, activating a resonant mode in the lower frequency range where the monopole and dipole modes of the cylindrical structure are coupled together. The resonant mode of the cylindrical structure excited by the sound source interacts with the sound source itself, causing the sound wave to have energy only in a specified direction, while canceling it out in other directions, thus achieving superdirectivity of the sound source at the far field. This multi-resonator coupled cylindrical structure can realize the resonant mode of coupling monopole and dipole modes, providing conditions for the preparation of directional sound sources.

[0128] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the appended claims.

Claims

1. A directional sound source system utilizing metamaterials, characterized in that, It includes an omnidirectional sound source and a directional device, and the directional effect of the directional device changes with the distance between the omnidirectional sound source and the directional device, achieving super-directionality of the omnidirectional sound source in a set direction; wherein, the directional device is a cylindrical structure, and the cylinder has a double-layer fan-ring cavity that runs through the cylinder; when the number of fan-ring cavities is double, there are eight fan-ring cavities inside the cylinder, wherein the eight fan-ring cavities consist of four inner fan-ring cavities and four outer fan-ring cavities superimposed on the outer side of the inner fan-ring cavities, and each fan-ring cavity in the double-layer fan-ring cavity has a slit that runs through the cylinder on its arc-shaped sidewall, and this slit serves as a throat tube. Each set of double-layer fan-ring cavities formed by superimposing the inner and outer fan-ring cavities serves as a double-layer curved surface resonator. The inner and outer fan-ring cavities in the same set of double-layer fan-ring cavities correspond to the same cavity angle, and the angle corresponding to the position of the throat tube is also the same.

2. The directional sound source system utilizing metamaterials as described in claim 1, characterized in that, When the number of fan-ring cavities is double, the depth, tracheal width, and tracheal depth of each double-layer fan-ring cavity satisfy the following relationship: α2=2*arcsin(0.55 / (1-D2)) β2 = 2*arcsin(D1) R i1 =1-D2*2-L i1 -L i2 R i2 =1-D2*2-L i1 R i3 =1-D2-L i1 R i4 =1-D2 R i5 ＝1 Where α2 is the cavity opening angle of the current double-layered sector annulus cavity, β2 is the laryngeal opening angle of the current double-layered sector annulus cavity, D1 is the laryngeal width of the current double-layered sector annulus cavity, D2 is the laryngeal depth of the current double-layered sector annulus cavity, and L i1 L represents the cavity depth of the inner fan-ring cavity in the current double-layer fan-ring cavity. i2 R represents the cavity depth of the outer fan-ring cavity in the current double-layer fan-ring cavity. i1 R is the radius of the circle to which the bottom arc of the inner fan ring cavity in the current double-layer fan ring cavity belongs. i2 R is the radius of the circle to which the bottom arc of the throat of the inner sector ring cavity in the current double-layer sector ring cavity belongs. i3 R is the radius of the circle to which the top arc of the throat of the inner sector ring cavity in the current double-layer sector ring cavity belongs. i4 R is the radius of the circle to which the bottom arc of the throat of the outer sector annulus in the current double-layer sector annulus cavity belongs. i5 It is the radius of the circle to which the top arc of the throat of the outer sector ring cavity in the current double-layer sector ring cavity belongs.

3. The directional sound source system utilizing metamaterials as described in claim 2, characterized in that, The dimensions of each sector ring cavity are not exactly the same. The dimensions of each sector ring cavity, the distance between the non-directional sound source and the directional device are obtained by particle swarm optimization algorithm. In the optimization process, the objective function is that the directional factor E in the direction of the directional device setting angle is greater than the set value.

4. A directional sound source system utilizing metamaterials as described in any one of claims 1 to 3, characterized in that, When the number of layers in the sector ring cavity is double, the angles corresponding to the setting positions of the throat tubes in each group of double-layer sector ring cavities are 0, π / 2, π, and 3π / 2, respectively.

5. A method for adjusting the directivity of a directional sound source system based on metamaterials as described in claim 1, characterized in that, Includes the following steps: Initial values ​​are set for the combination of dimensional parameters of each sector cavity, the distance between the omnidirectional sound source and the directional device. The combination of dimensional parameters includes the cavity opening angle, the throat opening angle, the throat width, the throat depth, the cavity depth, the radius of the circle to which the bottom arc of the cavity belongs, the radius of the circle to which the bottom arc of the throat belongs, and the radius of the circle to which the top arc of the throat belongs. Substituting the initial values ​​of the dimensional parameter combination into the sound pressure wave equation, acoustic boundary conditions, and impedance transfer formula corresponding to each double-layer curved surface resonator, we obtain the acoustic impedance of each double-layer curved surface resonator at different radii in various angular directions. Based on the acoustic impedance of each double-layer curved surface resonator at different radii in various angular directions, the incident wave sound pressure and scattered wave sound pressure of each double-layer curved surface resonator in various angular directions are obtained. Based on the incident wave sound pressure and scattered wave sound pressure of each double-layer curved surface resonator in each angular direction, the directivity factor E of the directivity device in each angular direction is obtained. Determine whether the directivity factor E in the set angle direction of the directivity device is greater than the set value. If yes, the sound source directivity adjustment of the directivity device is completed. If no, the particle swarm optimization algorithm is used to update the combination of size parameters of each sector cavity, the distance between the non-directional sound source and the directivity device, and then the updated values ​​are used to re-obtain the directivity factor E of the directivity device in each angle direction until the directivity factor E in the set angle direction of the directivity device is greater than the set value, and the sound source directivity adjustment of the directivity device is completed.

6. The sound source directivity adjustment method as described in claim 5, characterized in that, When the size parameters of each sector ring cavity are fixed, the directional effect of the directional device is optimal when the difference between the distance between the non-directional sound source and the directional device and the diameter of the cylindrical structure is less than a set threshold.

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