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

Abstract

The application provides a directional sound source device realized by using a metamaterial, a single-layer fan ring cavity penetrating through a cylinder is arranged in the cylinder to obtain a single-layer curved surface resonator type directional sound source device; then a multi-resonator coupling cylinder structure is used to control sound waves, a resonance mode in which a monopole mode and a dipole mode of the cylinder structure are coupled to each other is activated in a lower frequency range, the resonance mode of the cylinder structure excited by the sound source is coupled to the sound source to interact with each other, so that the sound waves have energy in a specified direction and are all 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 the 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 device 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 device and a directional adjustment method utilizing metamaterials, such that sound waves have energy only in a specified direction, while energy in other directions is canceled out, thereby achieving super-directivity of the sound source at a far-field location.

[0004] A directional sound source device utilizing metamaterials is disclosed. The device is a cylindrical structure with four single-layer fan-shaped cavities penetrating the cylinder. When the number of fan-shaped cavities is single-layer, there are four single-layer fan-shaped cavities inside the cylinder. Each single-layer fan-shaped cavity has a slit penetrating the cylinder on its arc-shaped sidewall, which serves as a throat. The single-layer fan-shaped cavities function as single-layer curved resonators.

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

[0006] α1=2*arcsin(0.55 / (1-d2))

[0007] β2 = 2*arcsin(d1)

[0008] r i1 =1-d2-l i1

[0009] r i2 =1-d2

[0010] r i3 =1

[0011] Where α1 is the cavity opening angle of the current single-layer sector ring cavity, β1 is the laryngeal opening angle of the current single-layer sector ring cavity, d1 is the laryngeal width of the current single-layer sector ring cavity, d2 is the laryngeal depth of the current single-layer sector ring cavity, and l i1 r represents the cavity depth of the current single-layer fan-shaped cavity. i1r is the radius of the circle to which the bottom arc of the current single-layer fan-shaped cavity belongs. i2 Let r be the radius of the circle to which the bottom arc of the throat of the current single-layer sector annular cavity belongs. i3 The radius of the circle to which the top arc of the throat of the current single-layer sector annular cavity belongs.

[0012] Furthermore, the dimensions of each sector ring cavity are not exactly the same. The dimensions of each sector ring cavity are obtained by particle swarm optimization algorithm. During the optimization process, the objective function is that the directivity factor E in the direction of the set angle of the sound source device is greater than the set value.

[0013] Furthermore, when the number of layers in the sector ring cavity is a single layer, the angles corresponding to the setting positions of the throat tubes in each sector ring cavity are 0, π / 2, π, and 3π / 2, respectively.

[0014] A method for adjusting the directivity of a directional sound source device utilizing metamaterials includes the following steps:

[0015] Initial values ​​are set for the combination of dimensional parameters for each sector annular cavity. 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.

[0016] Substituting 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 single-layer curved surface resonator, we obtain the acoustic impedance of each single-layer curved surface resonator at different radii in various angular directions.

[0017] Based on the acoustic impedance of each single-layer curved surface resonator at different radii in various angular directions, the incident wave sound pressure and scattered wave sound pressure of each single-layer curved surface resonator in various angular directions are obtained.

[0018] Based on the incident wave sound pressure and scattered wave sound pressure of each single-layer curved surface resonator in each angular direction, the directivity factor E of the sound source device in each angular direction is obtained.

[0019] Determine whether the directivity factor E of the sound source device in the set angle direction is greater than the set value. If yes, the sound source directivity adjustment of the sound source device is completed. If no, the particle swarm optimization algorithm is used to update the value of the combination of size parameters of each sector ring cavity. Then, the updated value is used to re-obtain the directivity factor E of the sound source device in each angle direction until the directivity factor E of the sound source device in the set angle direction is greater than the set value, and the sound source directivity adjustment of the sound source device is completed.

[0020] Beneficial effects:

[0021] 1. This invention provides a directional sound source device realized using metamaterials. A single-layer fan-shaped cavity is set inside a cylinder to obtain a directional sound source device in the form of a single-layer curved resonator. Then, the sound waves are modulated by coupling the cylindrical structure with multiple resonators. The resonant modes of the cylindrical structure, which are coupled with each other, are activated 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 the specified direction, while the energy in other directions is canceled out. This achieves the superdirectivity of the sound source at the far field position, providing conditions for the preparation of directional sound sources.

[0022] 2. This invention provides a directional sound source device using metamaterials. By selecting the particle swarm optimization algorithm to solve the parameters of the resonator, the optimal design parameters of the directional sound source device can be obtained. After obtaining the optimized parameters of the directional sound source device, it is modeled in simulation software and the directional effect of the directional sound source device is calculated. Experiments show that the single-layer curved surface resonator can achieve good directivity.

[0023] 3. This invention provides a method for adjusting the directivity of a sound source. When the dimensions of each sector cavity are different, the acoustic impedance of the directional sound source device is obtained. Then, sound pressure data is obtained based on the acoustic impedance. Finally, the directivity factor E of the directional sound source 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, the dimensions of each sector cavity of the directional sound source device are re-optimized using a particle swarm optimization algorithm, thereby achieving the adjustment of the sound source directivity of the directional sound source device. This method can obtain the required directivity at any angle and has a wide range of applications. Attached Figure Description

[0024] Figure 1 A two-dimensional schematic diagram of a directional sound source device formed by a single-layer curved surface resonator coupled to a cylindrical structure, provided by the present invention.

[0025] Figure 2 A schematic diagram showing the dimensions of the single-layer curved surface resonator provided by the present invention;

[0026] Figure 3 A schematic diagram showing the location for calculating the acoustic impedance of the single-layer curved surface resonator provided by the present invention. Detailed Implementation

[0027] 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.

[0028] 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.

[0029] Specifically, a directional sound source device utilizing metamaterials, wherein the device is an overall cylindrical structure, and the cylinder contains a single-layer or double-layer fan-shaped cavity that penetrates the cylinder, such as... Figure 1 As shown, when the number of fan ring cavities is single-layer, there are four single-layer fan ring cavities inside the cylinder, and each single-layer fan ring cavity has a slit that penetrates the cylinder through its arc-shaped sidewall, which serves as a throat. Meanwhile, the angles corresponding to the positions of the throats on each fan ring cavity are 0, π / 2, π, and 3π / 2, respectively. The single-layer fan ring cavity serves as a single-layer curved surface resonator.

[0030] It should be noted that the dimensions of each sector ring cavity are not exactly the same. The dimensions of each sector ring cavity are obtained by particle swarm optimization algorithm. In the optimization process, the objective function is that the directivity factor in the direction of the set angle of the sound source device is greater than the set value. The directivity factor, like directivity, represents the strength of the directivity of the sound pressure signal. The larger the directivity factor, the stronger the directivity of the directional device, which means that the sound energy emitted by the directional device is more concentrated in a certain direction.

[0031] Furthermore, such as Figure 2 As shown, the directional sound source device consists of a cylinder and four single-layer curved surface resonators evenly arranged inside the cylinder. The angle of the i-th (1≤i≤4) single-layer curved surface resonator corresponding to the cylinder is φ. i (respectively 0, π / 2, π, 3π / 2), and the parameter settings for the single-layer curved surface resonator are as follows:

[0032] The center of the cylindrical structure coincides with the origin of the coordinate system. The parameters of the four single-layer curved surface resonators inside the cylindrical structure are set as follows: the depth of the curved surface resonator cavity at the 0° position is set to l. 11 The depth of the curved resonator cavity at the position rotated 90° counterclockwise is set to l. 21 The depth of the curved resonator cavity at a position rotated 180° counterclockwise is set to l. 31 The depth of the curved resonator cavity at a position rotated 270° counterclockwise is set to l. 41The range of the above four depth parameters is 0-0.8 (the range of this parameter and the following parameters is dimensionless normalized). The laryngeal opening angle and the cavity opening angle are optimized using the laryngeal width and laryngeal depth, respectively. The laryngeal width parameter is set as d1, with a range of 0.07-0.125, and the laryngeal depth parameter is set as d2, with a range of 0.05-0.09.

[0033] Based on the above-mentioned parameters, the required optimization parameters can be obtained by solving the following formula:

[0034] α1=2*arcsin(0.55 / (1-d2))

[0035] β2 = 2*arcsin(d1)

[0036] r i1 =1-d2-l i1

[0037] r i2 =1-d2

[0038] r i3 =1

[0039] Where α1 is the cavity opening angle of the current single-layer sector ring cavity, β1 is the laryngeal opening angle of the current single-layer sector ring cavity, d1 is the laryngeal width of the current single-layer sector ring cavity, d2 is the laryngeal depth of the current single-layer sector ring cavity, and l i1 r represents the cavity depth of the current single-layer fan-shaped cavity. i1 r is the radius of the circle to which the bottom arc of the current single-layer fan-shaped cavity belongs. i2 Let r be the radius of the circle to which the bottom arc of the throat of the current single-layer sector annular cavity belongs. i3 Let θ be the radius of the circle to which the top arc of the throat tube of the current single-layer fan-shaped cavity belongs; where, when using the throat tube depth and width parameters to solve for the cavity opening angle α1 and the throat tube opening angle β1, a certain approximation condition is used, that is, when the angle θ is very small, sin(θ)=θ.

[0040] Based on the optimized parameters, a single-layer resonator was designed and prepared, and the experimental environment was set up. Then, sound pressure data was collected at a designated location of the directional sound source 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 sound source device.

[0041] Based on the above-mentioned directional sound source device utilizing metamaterials, the present invention also provides a method for adjusting the directivity of a sound source, comprising the following steps:

[0042] S1: Set initial values ​​for the combination of dimensional parameters for each sector annular cavity, where the combination of dimensional parameters includes cavity opening angle, throat opening angle, throat width, throat depth, cavity depth, radius of the circle to which the bottom arc of the cavity belongs, radius of the circle to which the bottom arc of the throat belongs, and radius of the circle to which the top arc of the throat belongs.

[0043] 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 single-layer curved surface resonator to obtain the acoustic impedance of each single-layer curved surface resonator at different radii in various angular directions.

[0044] S3: Based on the acoustic impedance of each single-layer curved surface resonator at different radii in various angular directions, obtain the incident wave sound pressure and scattered wave sound pressure of each single-layer curved surface resonator in various angular directions.

[0045] 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.

[0046] S4: Based on the incident wave sound pressure and scattered wave sound pressure of each single-layer curved surface resonator in each angular direction, obtain the directivity factor E of the sound source device in each angular direction.

[0047] The directionality factor E is calculated as follows:

[0048]

[0049] 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.

[0050] S5: Determine whether the directivity factor E in the set angle direction of the sound source device is greater than the set value. If yes, the sound source directivity adjustment of the sound source device is completed. If no, the particle swarm optimization algorithm is used to update the value of the combination of size parameters of each sector ring cavity, and then the updated value is used to re-obtain the directivity factor E of the sound source device in each angle direction until the directivity factor E in the set angle direction of the sound source device is greater than the set value, and the sound source directivity adjustment of the sound source device is completed.

[0051] 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:

[0052] First, assume r1 is the distance from the bottom of cavity 1 to the center of the cylinder, i.e. Figure 3 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 3 The 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 3 The distance between the third black arc from 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.

[0053] The fundamental equation for sound pressure in a cylindrical structure is as follows:

[0054]

[0055] 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.

[0056] Acoustic boundary conditions:

[0057] p1 = p2

[0058] v1S1=v2S2

[0059] 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.

[0060] Separate the variables from equation (2-1) and let...

[0061]

[0062] 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.

[0063] Substituting equation (2-2) into equation (2-1), we obtain two independent ordinary differential equations.

[0064]

[0065]

[0066] Ψ n (φ,φ m The following boundary conditions must be met:

[0067]

[0068] Solving the above formula yields...

[0069]

[0070]

[0071] 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;

[0072] When r1 < r < r2, the sound pressure p inside the cavity m (r) and velocity v mr Satisfy the following equation

[0073]

[0074]

[0075] Where ρ is the air density and ω is the angular frequency;

[0076] Considering the rigid boundary conditions at the bottom of the cavity, the velocity at the bottom of the cavity is 0, satisfying the expression

[0077]

[0078] Among them, Ψ is used n (φ,φ m The orthogonality of ) can be obtained

[0079]

[0080] Substituting the velocity continuity boundary condition at r = r2 and simplifying, we get...

[0081]

[0082] Where c is the speed of sound in air, U throat_r This represents the volume velocity at the location of the larynx;

[0083] Solving equations (2-11) and (2-12) simultaneously yields the auxiliary coefficient A. ηn B ηn

[0084]

[0085]

[0086] Equation Z a (r2) represents the acoustic impedance at r = r2.

[0087]

[0088] in, This represents the average sound pressure level at the throat.

[0089] Equation (2-1) for sound pressure wave also applies to the larynx, as follows:

[0090]

[0091] 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.

[0092]

[0093]

[0094] 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;

[0095] Based on the expression of acoustic impedance in the larynx

[0096] Substitute (2-17) and (2-18) into the above equation

[0097]

[0098]

[0099] 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.

[0100] The acoustic impedance Z can be obtained by combining (2-19) and (2-20). a (r3)

[0101]

[0102] Based on equations (2-8) and (2-12)

[0103] At r = r3, the sound pressure and volume velocity satisfy the following equations.

[0104]

[0105]

[0106] 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. Let r be the first derivative of the Hankel function at position r4.

[0107] Thus, the present invention obtains as follows Figure 3The acoustic impedance at the five black arcs shown can be obtained similarly for the acoustic impedance at other locations of the directional sound source device, and will not be elaborated upon in this invention.

[0108] 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.

[0109] 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 device utilizing metamaterials, characterized in that, The device is a cylindrical structure with four single-layer fan-shaped annular cavities penetrating the cylinder. When the number of fan-shaped annular cavities is single-layered, the cylinder has four single-layered fan-shaped annular cavities, and each single-layered fan-shaped annular cavity has a slit penetrating the cylinder on its arc-shaped sidewall, which serves as a throat. The single-layered fan-shaped annular cavity acts as a single-layered curved resonator. When the number of fan-shaped annular cavities is single-layered, the depth, throat width, and throat depth of each single-layered fan-shaped annular cavity satisfy the following relationship: in, This refers to the cavity angle of the current single-layer fan-shaped cavity. This refers to the throat angle of the current single-layer sector ring cavity. This refers to the throat width of the current single-layer sector ring cavity. This represents the throat depth of the current single-layer sector annulus cavity. This represents the cavity depth of the current single-layer fan-shaped cavity. The radius of the circle to which the bottom arc of the current single-layer fan-shaped cavity belongs. The radius of the circle to which the bottom arc of the throat of the current single-layer sector annular cavity belongs. The radius of the circle to which the top arc of the throat of the current single-layer sector annular cavity belongs.

2. The directional sound source device utilizing metamaterials as described in claim 1, characterized in that, The dimensions of each sector cavity are not exactly the same. The dimensions of each sector cavity are obtained by particle swarm optimization algorithm, and during the optimization process, the directivity factor in the angular direction set by the sound source device is used. The value is greater than the target function.

3. A directional sound source device utilizing metamaterials as described in any one of claims 1 to 2, characterized in that, When the number of layers in the sector annulus cavity is single-layered, the angles corresponding to the placement positions of the throat tubes in each sector annulus cavity are as follows: .

4. A method for adjusting the directivity of a directional sound source device 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 for each sector annular cavity. 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 combination of size parameters into the sound pressure wave equation, acoustic boundary conditions, and impedance transfer formula corresponding to each single-layer curved surface resonator, we obtain the acoustic impedance of each single-layer curved surface resonator at different radii in various angular directions. Based on the acoustic impedance of each single-layer curved surface resonator at different radii in various angular directions, the incident wave sound pressure and scattered wave sound pressure of each single-layer curved surface resonator in various angular directions are obtained. Based on the incident and scattered sound pressures of each single-layer curved surface resonator at various angular directions, the directivity factor of the sound source device at each angular direction is obtained. ; Determine the directivity factor of the sound source device in the set angular direction. If the value is greater than the set value, the sound source directivity adjustment of the sound source device is completed; otherwise, the particle swarm optimization algorithm is used to update the values ​​of the size parameter combinations of each sector cavity, and then the updated values ​​are used to re-obtain the directivity factor of the sound source device in each angular direction. Until the directivity factor in the angular direction set by the sound source device is... If the value is greater than the set value, the sound source directivity adjustment of the sound source device is completed.

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