An acoustic diffuser based on acoustic metasurface and design method

Abstract

The present application discloses an acoustic diffuser based on an acoustic metasurface and a design method, wherein the acoustic diffuser based on the acoustic metasurface includes at least one diffusion module, and at least one diffusion subunit is provided on the diffusion module. In an embodiment of the present application, the above-mentioned acoustic diffuser based on the acoustic metasurface and the design method are adopted, which is composed of diffusion subunits, has a light and thin structure, is flexible to use, adapts to the needs of modern architectural design, is easy to install and use, can be modularly processed and assembled, is easy to adjust, has low construction difficulty, and can be applied to a variety of acoustic occasions. At the same time, each diffusion subunit contains multiple cavity areas, and the resonance structure is excited by connecting multiple diffusion subunits in series or in parallel, and the sound reflection phase is adjusted, so that the working frequency band can be optimized according to actual needs. The low frequency band can be adjusted to below 50Hz, and the high frequency band can reach above 4000Hz. The working frequency band is wide and the acoustic performance is strong, which can meet the acoustic requirements in different environments.

Description

Technical Field

[0001] The present invention relates to the technical field of acoustic metasurfaces, and in particular to an acoustic diffuser based on an acoustic metasurface and a design method thereof. Background Art

[0002] Acoustic Diffusers are a tool used to deal with indoor sound reflections. They can disperse incident sound waves into small-amplitude sound waves that propagate in multiple directions. That is, by scattering sound waves, harmful reflections and standing waves are reduced, thereby improving the uniformity of the sound field in the room.

[0003] Traditional Schroeder diffusers are widely used in architectural acoustics due to their design principles and material properties. However, since their working wavelength and thickness are positively correlated, their size is too large in the low-frequency range, affecting their actual application effect. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides an acoustic diffuser and design method based on an acoustic metasurface that is broadband, lightweight, and highly flexible in use.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solutions.

[0006] The present application provides an acoustic diffuser based on an acoustic metasurface, comprising at least one diffusion module, wherein at least one diffusion subunit is provided on the diffusion module;

[0007] The diffusion subunit includes a first cavity, a second cavity, a third cavity, and a fourth cavity which are arranged on the diffusion module in the Y-axis direction;

[0008] The third cavity is arranged between the first cavity and the fourth cavity and is connected to the first cavity and the fourth cavity in the X-axis direction, respectively. Two third cavities are provided, and the two third cavities are symmetrically arranged with respect to the second cavity and are connected to the first cavity respectively. The fourth cavity is connected to the outside of the diffusion module on one side in the Z-axis direction;

[0009] Wherein, when there are a plurality of diffusion sub-units on the diffusion module, the plurality of diffusion sub-units form a parallel structure, a series structure or a series-parallel composite structure.

[0010] It is further defined that in the above-mentioned acoustic diffuser based on an acoustic metasurface, a plurality of diffusion subunits are provided on the diffusion module, and the plurality of diffusion subunits form a parallel structure;

[0011] Wherein, the plurality of diffusion sub-units are arranged in a linear array in the Z-axis direction, and the fourth cavities are interconnected in the Z-axis direction.

[0012] It is further defined that in the above-mentioned acoustic diffuser based on an acoustic metasurface, a plurality of diffusion subunits are provided on the diffusion module, and the plurality of diffusion subunits form a series structure;

[0013] One of the diffusion subunits is used as a primary diffusion unit, and the other diffusion subunits are used as secondary diffusion units, and the secondary diffusion units are arranged in the first cavity of the primary diffusion unit;

[0014] The second diffusion unit omits the fourth cavity, and the second cavity is connected with the first cavity of the first diffusion unit in the Y-axis direction.

[0015] It is further defined that, in the above-mentioned acoustic diffuser based on acoustic metasurface, a plurality of diffusion subunits are provided on the diffusion module, and the plurality of diffusion subunits constitute a series-parallel composite structure;

[0016] At least one of the diffusion subunits is used as a secondary diffusion unit, and a plurality of the diffusion subunits are used as primary diffusion units and are arranged in a linear array in the Z-axis direction, and the fourth cavities of the plurality of primary diffusion units are interconnected in the Z-axis direction;

[0017] A secondary diffusion unit is disposed in the first cavity of at least one of the primary diffusion units, the fourth cavity is omitted from the secondary diffusion unit, and the second cavity is connected to the first cavity of the primary diffusion unit at the corresponding position in the Y-axis direction.

[0018] It is further defined that, in the above-mentioned acoustic diffuser based on acoustic metasurface, a plurality of diffusion modules are provided, and the plurality of diffusion modules are fixedly connected and each is provided with at least one diffusion sub-unit.

[0019] The present application also provides a design method applicable to any of the above-mentioned acoustic diffusers based on acoustic metasurfaces, including:

[0020] Obtain the equivalent dynamic mass density and bulk modulus of the cavity structure in the acoustic diffuser, and obtain the equivalent impedance matrix of the cavity structure based on the equivalent dynamic mass density and bulk modulus;

[0021] Based on the equivalent impedance matrix of the cavity structure, the theoretical model results of multiple cavity structures in series and parallel are obtained;

[0022] The acoustic reflection phase of the diffusion module is obtained based on the theoretical model results of multiple cavity structures connected in series and in parallel;

[0023] Adjust the structural parameters of the diffusion subunit based on the simulation results of the acoustic reflection phase of the diffusion module, and iteratively optimize to achieve the expected acoustic reflection phase results;

[0024] Among them, the structural parameters of the acoustic diffuser include the number of diffusion subunits, the connection structure, and the cavity size.

[0025] Further defined, in the above-mentioned design method, the equivalent impedance matrix of the cavity structure is obtained based on the equivalent dynamic mass density and the bulk modulus as follows:

[0026] The wave number and characteristic impedance of the cavity structure are obtained based on the equivalent dynamic mass density and bulk modulus, and the equivalent impedance matrix of the cavity structure is obtained based on the wave number and characteristic impedance of the cavity structure.

[0027] Further defined, in the above-mentioned design method, the method for obtaining the equivalent dynamic mass density and bulk modulus of the cavity structure is:

[0028] Equivalent dynamic mass density:

[0029] Bulk modulus:

[0030] in, i is the imaginary unit, w is the cavity scale factor, ω is the angular frequency, ρ0 is the air density, η0 is the dynamic viscosity, K0 is the air bulk modulus, P r is the Prandtl number, γ is the specific heat ratio of air;

[0031] The wave number and characteristic impedance of the cavity structure are obtained as follows:

[0032] Wave number: Characteristic impedance:

[0033] Where, L is the length of the cavity;

[0034] The method for obtaining the equivalent impedance matrix of the cavity structure is:

[0035]

[0036] Further defined, in the above-mentioned design method, the equivalent matrix acquisition method of the theoretical model results of multiple cavity structures in series is:

[0037]

[0038] The equivalent matrix acquisition method of the theoretical model results of multiple cavity structures in parallel is:

[0039]

[0040] Among them, Z t1 =M t1 (1,1) / M t1 (2,1); Z t1 =Mt2 (1,1) / M t2 (2,1).

[0041] Further defined, in the above-mentioned design method, the method for obtaining the acoustic reflection phase of the diffusion subunit is:

[0042] φ=arg(R);

[0043] Among them, the acoustic reflection coefficient of the diffusion subunit is: Impedance of the diffusion subunit: Z0 is the acoustic impedance of air.

[0044] The present invention has at least the following beneficial effects:

[0045] 1. It is composed of diffusion subunits, with a light and thin structure and flexible use, which can meet the needs of modern architectural design. It is not only easy to install and use, but also can be processed and assembled in a modular manner, easy to adjust, and has low construction difficulty. It can be applied to a variety of acoustic occasions. At the same time, each diffusion subunit contains multiple cavity areas. The resonance structure is excited by connecting multiple diffusion subunits in series or in parallel, and the sound reflection phase is adjusted, so that the working frequency band can be optimized according to actual needs. The low frequency band can be adjusted to below 50Hz, and the high frequency band can reach above 4000Hz. The working frequency band is wide and the acoustic performance is strong, which can meet the acoustic requirements in different environments;

[0046] 2. By performing acoustic finite element simulation on the structure of the diffusion subunit, a diffusion subunit structure suitable for different frequency bands and wide frequency bands is obtained, which can not only achieve better broadband adaptability, but also greatly enhance the sound reinforcement effect and effectively improve the uniformity of the sound field. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 This is a schematic structural diagram of a "diffusion subunit" in an acoustic diffuser based on an acoustic metasurface according to an embodiment of the present application;

[0048] Figure 2 This is a schematic structural diagram of a "diffusion subunit" in an acoustic diffuser based on an acoustic metasurface according to an embodiment of the present application;

[0049] Figure 3 This is a schematic diagram of the parallel structure of multiple "diffusion subunits" in an acoustic diffuser based on an acoustic metasurface according to an embodiment of the present application;

[0050] Figure 4 This is a schematic diagram of the parallel structure of multiple "diffusion subunits" in an acoustic diffuser based on an acoustic metasurface according to an embodiment of the present application;

[0051] Figure 5This is a schematic diagram of the series structure of multiple "diffusion subunits" in an acoustic diffuser based on an acoustic metasurface according to an embodiment of the present application;

[0052] Figure 6 This is a schematic diagram of a composite structure of multiple "diffusion subunits" in series and parallel in an acoustic diffuser based on an acoustic metasurface according to an embodiment of the present application;

[0053] Figure 7 This is a schematic diagram of the structure of an acoustic diffuser based on an acoustic metasurface according to an embodiment of the present application;

[0054] Figure 8 A schematic diagram of a reflection phase diagram of an acoustic diffuser based on an acoustic metasurface according to an embodiment of the present application;

[0055] Fig. 9 This is a comparison diagram of diffusion coefficients of an acoustic diffuser based on an acoustic metasurface according to an embodiment of the present application and a flat plate of the same size under normal incidence;

[0056] Fig.10 This is a comparison chart of diffusion coefficients of an acoustic diffuser based on an acoustic metasurface according to an embodiment of the present application and a flat plate of the same size at 60° oblique incidence;

[0057] Fig.11 A comparison diagram of the sound pressure level distribution of the acoustic diffuser based on the acoustic metasurface in the embodiment of the present application at "500 Hz" and the reflected sound field of the flat plate;

[0058] Fig.12 This is a comparison chart of the diffusion coefficients of an acoustic diffuser based on an acoustic metasurface and a flat plate under normal incidence in an embodiment of the present application.

[0059] Reference numerals

[0060] Diffusion module 100 , first cavity 210 , second cavity 220 , third cavity 230 , fourth cavity 240 . DETAILED DESCRIPTION

[0061] The following will be combined with the drawings in the embodiments of the present application to clearly describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments in the present application belong to the scope of protection of this application.

[0062] The terms "first", "second", etc. in the specification and claims of this application are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable under appropriate circumstances, so that the embodiments of the present application can be implemented in an order other than those illustrated or described here, and the objects distinguished by "first", "second", etc. are generally of one type, and the number of objects is not limited. For example, the first object can be one or more. In addition, "and / or" in the specification and claims represents at least one of the connected objects, and the character " / " generally indicates that the objects associated with each other are in an "or" relationship.

[0063] The acoustic diffuser and design method based on acoustic metasurface provided in the embodiment of the present application are described in detail below with reference to specific embodiments and their application scenarios in conjunction with the accompanying drawings.

[0064] Example 1

[0065] like Figures 1 to 7 As shown, an embodiment of the present application provides an acoustic diffuser based on an acoustic metasurface, including at least one diffusion module 100, and at least one diffusion sub-unit is provided on the diffusion module 100.

[0066] like Figure 1 , Figure 2 As shown, the diffusion subunit includes a first cavity 210, a second cavity 220, a third cavity 230, and a fourth cavity 240 which are arranged on the diffusion module 100 in the Y-axis direction.

[0067] The third cavity 230 is disposed between the first cavity 210 and the fourth cavity 240 and is communicated with the first cavity 210 and the fourth cavity 240 in the X-axis direction, respectively. Two third cavities 230 are provided, and the two third cavities 230 are symmetrically arranged with respect to the second cavity 220 and are communicated with the first cavity 210 respectively. One side of the fourth cavity 240 in the Z-axis direction is communicated with the outside of the diffusion module 100;

[0068] When there are multiple diffusion sub-units on the diffusion module 100, the multiple diffusion sub-units form a parallel structure, a series structure or a series-parallel composite structure.

[0069] like Fig. 9 As shown in the figure, it shows the comparison of the diffusion coefficients of a diffuser composed of 5 diffusion modules (each diffusion module contains a diffusion sub-unit) and a flat plate of the same size under normal incidence. It can be seen from the figure that after the operating frequency exceeds 350Hz, the diffusion coefficient of the diffuser is greater than the diffusion coefficient of the flat plate of the same size, and the attenuation is not obvious. As the operating frequency increases, the stability of the diffusion coefficient can still be guaranteed.

[0070] It should be noted that, compared with the traditional Schroeder diffuser, the thickness of the present invention is only 1 / 10 of the traditional structure at an operating frequency of 500 Hz, and can significantly reduce the size problem of the traditional structure in the low frequency band.

[0071] like Fig.10 As shown in the figure, it shows the comparison of the diffusion coefficients of a diffuser composed of 5 diffusion modules (each diffusion module contains a diffusion sub-unit) and a flat plate of the same size under 60° oblique incidence. It can be seen from the figure that in the same normal incidence working environment, after the working frequency exceeds 350Hz, the diffusion coefficient of the diffuser is more stable than the diffusion coefficient of the flat plate of the same size, and still maintains wide-band working performance with excellent performance, effectively improving the uniformity of the sound field and facilitating practical applications.

[0072] like Fig.11 As shown, it shows the comparison of the sound pressure level distribution of the diffuser and the flat plate of the same size at an operating frequency of 500Hz. It can be seen from the figure that compared with the flat plate of the same size, the sound pressure level distribution of the reflected sound field of the diffuser is more uniform, thus ensuring the sound reinforcement effect.

[0073] In an embodiment of the present application, an acoustic diffuser based on an acoustic metasurface as described above is adopted, which is composed of diffusion sub-units. It has a light and thin structure and is flexible to use. It can adapt to the needs of modern architectural design. It is not only easy to install and use, but also can be modularly processed and assembled. It is easy to adjust and has low construction difficulty. It can be applicable to a variety of acoustic occasions. At the same time, each diffusion sub-unit includes multiple cavity areas. The resonant structure is excited by connecting multiple diffusion sub-units in series or in parallel, and the sound reflection phase is adjusted, so that the working frequency band can be optimized according to actual needs. The low frequency band can be adjusted to below 50 Hz, and the high frequency band can reach above 4000 Hz. The working frequency band is wide and the acoustic performance is strong, which can meet the acoustic requirements in different environments.

[0074] In a preferred embodiment, Figure 3 , Figure 4 As shown, a plurality of diffusion sub-units are disposed on the diffusion module 100, and the plurality of diffusion sub-units form a parallel structure.

[0075] The plurality of diffusion sub-units are arranged in a linear array in the Z-axis direction, and the fourth cavities 240 are interconnected in the Z-axis direction.

[0076] It is understandable that the more diffusion sub-units are connected in parallel, the larger their volume is and the better their acoustic performance is. Conversely, it means that they are lighter and thinner. The specific setting form is based on usage requirements and will not be elaborated here.

[0077] In a preferred embodiment, Figure 3 , Figure 4 As shown, the diffusion subunits are specifically arranged in three, and the three diffusion subunits form a parallel structure.

[0078] The three diffusion sub-units are arranged in a linear array in the Z-axis direction, and the fourth cavities 240 are interconnected in the Z-axis direction.

[0079] In a preferred embodiment, Figure 5 As shown, a plurality of diffusion sub-units are disposed on the diffusion module 100, and the plurality of diffusion sub-units form a series structure.

[0080] One of the diffusion sub-units is used as a primary diffusion unit, and the remaining diffusion sub-units are used as secondary diffusion units. The secondary diffusion unit is disposed in the first cavity 210 of the primary diffusion unit.

[0081] The fourth cavity 240 is omitted in the secondary diffusion unit, and the second cavity 220 is connected to the first cavity 210 of the primary diffusion unit in the Y-axis direction.

[0082] like Figure 8 As shown, it represents the reflection phase comparison between a single diffusion sub-unit and the series structure of the primary diffusion unit and the secondary diffusion unit. From this figure, it can be found that the series structure of the primary diffusion unit and the secondary diffusion unit can obtain a higher frequency adjustment capability and has a wider operating frequency band.

[0083] It is understandable that a diffusion sub-unit can be further arranged in the first cavity 210 of the secondary diffusion unit as a tertiary diffusion unit. The more series-connected diffusion units are, the stronger the frequency bandwidth performance is, which will not be elaborated here.

[0084] In a preferred embodiment, Figure 5 As shown, a plurality of secondary diffusion units are disposed in the first cavity 210 of the primary diffusion unit.

[0085] Wherein, a plurality of secondary diffusion units are arranged in a linear array in the Z-axis direction.

[0086] In a preferred embodiment, Figure 5 As shown, the diffusion module 100 is provided with three diffusion sub-units, and the three diffusion sub-units form a series structure.

[0087] One of the diffusion sub-units is used as a primary diffusion unit, and the other two diffusion sub-units are used as secondary diffusion units. The secondary diffusion unit is arranged in the first cavity 210 of the primary diffusion unit.

[0088] The fourth cavity 240 is omitted in the secondary diffusion unit, and the second cavity 220 is connected to the first cavity 210 of the primary diffusion unit in the Y-axis direction.

[0089] In a preferred embodiment, Figure 6As shown, a plurality of diffusion sub-units are disposed on the diffusion module 100, and the plurality of diffusion sub-units form a series-parallel composite structure.

[0090] At least one diffusion subunit is used as a secondary diffusion unit, and a plurality of diffusion subunits are used as primary diffusion units and are arranged in a linear array in the Z-axis direction. The fourth cavities 240 of the plurality of primary diffusion units are interconnected in the Z-axis direction.

[0091] The first cavity 210 of at least one primary diffusion unit is provided with a secondary diffusion unit, the secondary diffusion unit omits the fourth cavity 240, and the second cavity 220 is connected to the first cavity 210 of the corresponding primary diffusion unit in the Y-axis direction.

[0092] In a preferred embodiment, Figure 6 As shown, the diffusion module 100 is provided with six diffusion sub-units, and the six diffusion sub-units form a series-parallel composite structure.

[0093] The two diffusion sub-units serve as primary diffusion units and are arranged in a linear array in the Z-axis direction. The fourth cavities 240 of the two primary diffusion units are interconnected in the Z-axis direction.

[0094] Two diffusion sub-units are respectively disposed in the first cavities 210 of the two primary diffusion units, and the diffusion sub-units in the first cavities 210 of the primary diffusion units serve as secondary diffusion units.

[0095] The plurality of secondary diffusion units are arranged in a linear array in the Z-axis direction, the fourth cavity 240 is omitted from the secondary diffusion unit, and the second cavity 220 is connected to the first cavity 210 of the corresponding primary diffusion unit in the Y-axis direction.

[0096] It can be understood that two diffusion sub-units are used as primary diffusion units and are connected in parallel to form a two-layer parallel structure, and two secondary diffusion units are connected in series in each layer of primary diffusion units.

[0097] like Fig.12 As shown in FIG. 1 , the diffusion coefficients of a diffuser composed of five diffusion modules (each diffusion module contains a diffusion subunit) and a flat plate of the same size under normal incidence are compared. It can be found that the double-layer diffuser can further improve the overall diffusion performance.

[0098] In a preferred embodiment, Figure 7 As shown, a plurality of diffusion modules 100 are provided, and the plurality of diffusion modules 100 are fixedly connected and each of them is provided with at least one diffusion sub-unit.

[0099] In a preferred embodiment, the physical material of the diffusion module 100 is specifically set to wood or metal, and the filling material in the first cavity 210, the second cavity 220, the third cavity 230, and the fourth cavity 240 is air.

[0100] It is understandable that the physical material of the diffusion module 100 is not limited to the above-mentioned one, and is specifically formulated based on different architectural styles and environmental requirements. As long as the overall structure of the diffusion module 100 can be guaranteed, it will not be elaborated here.

[0101] Example 2

[0102] The present application embodiment provides a design method, which is applicable to the acoustic diffuser based on the acoustic metasurface in the above embodiment 1, including:

[0103] Step S1, obtaining an equivalent dynamic mass density and a bulk modulus of a cavity structure in an acoustic diffuser, and obtaining an equivalent impedance matrix of the cavity structure based on the equivalent dynamic mass density and the bulk modulus;

[0104] Step S2, obtaining theoretical model results of multiple cavity structures connected in series and in parallel based on the equivalent impedance matrix of the cavity structure;

[0105] Step S3, obtaining the acoustic reflection phase of the diffusion module based on the theoretical model results of multiple cavity structures connected in series and in parallel;

[0106] Step S4: adjusting the structural parameters of the diffusion subunit based on the acoustic reflection phase result of the diffusion module, and iteratively optimizing to achieve the expected acoustic reflection phase result.

[0107] Among them, the structural parameters of the acoustic diffuser include the number of diffusion subunits, the connection structure, and the cavity size.

[0108] It can be understood that the connection structure of the diffusion sub-unit specifically represents the number of parallel structural layers and the number of series structural levels of multiple diffusion sub-units. By adjusting the number and size of cavities of the diffusion sub-unit, a variety of working frequency band selections can be achieved to meet the needs of different acoustic environments.

[0109] In an embodiment of the present application, the above-mentioned design method is adopted to perform acoustic finite element simulation on the structure of the diffusion sub-unit to obtain a diffusion sub-unit structure suitable for different frequency bands and wide frequency bands, which can not only achieve better wide-band adaptability, but also greatly enhance the sound reinforcement effect, effectively improving the uniformity of the sound field.

[0110] In a preferred embodiment, in step S1, the equivalent impedance matrix of the cavity structure is obtained based on the equivalent dynamic mass density and the bulk modulus as follows:

[0111] The wave number and characteristic impedance of the cavity structure are obtained based on the equivalent dynamic mass density and bulk modulus, and the equivalent impedance matrix of the cavity structure is obtained based on the wave number and characteristic impedance of the cavity structure.

[0112] In a preferred embodiment, in step S1, the method for obtaining the equivalent dynamic mass density and bulk modulus of the cavity structure is:

[0113] Equivalent dynamic mass density:

[0114] Bulk modulus:

[0115] in, i is the imaginary unit, w is the cavity scale factor, ω is the angular frequency, ρ0 is the air density, η0 is the dynamic viscosity, K0 is the air bulk modulus, P r is the Prandtl number, and γ is the specific heat ratio of air.

[0116] It can be understood that each cavity area in the diffusion subunit has a different size factor w, and multiple diffusion subunits can further form a series structure, a parallel structure or a series-parallel composite structure to obtain better acoustic performance.

[0117] In a preferred embodiment, in step S1, the wave number and characteristic impedance of the cavity structure are obtained by:

[0118] Wave number: Characteristic impedance:

[0119] Where L is the length of the cavity.

[0120] In a preferred embodiment, in step S1, the method for obtaining the equivalent impedance matrix of the cavity structure is:

[0121]

[0122] In a preferred embodiment, in step S2, the equivalent matrix acquisition method of the theoretical model results of multiple cavity structures in series is:

[0123]

[0124] In a preferred embodiment, in step S2, the equivalent matrix of the theoretical model results of multiple cavity structures in parallel is obtained by:

[0125]

[0126] Among them, Z t1 =M t1 (1,1) / M t1 (2,1); Z t1 =M t2 (1,1) / M t2 (2,1).

[0127] In a preferred embodiment, in step S3, the method for acquiring the acoustic reflection phase of the diffusion subunit is:

[0128] φ=arg(R);

[0129] Among them, the acoustic reflection coefficient of the diffusion subunit is: Impedance of the diffusion subunit: where Z0 is the acoustic impedance of air.

[0130] In an embodiment of the present application, the above-mentioned design method is adopted, and the impedance transfer method is used to obtain the overall impedance of the series and parallel structures, so as to obtain the sound wave reflection phase parameters of the entire structure, and then realize the adjustment of the diffusion coefficient in the diffuse sound field.

[0131] In a preferred embodiment, in step S4, the cavity sizes of the first cavity 210, the second cavity 220, the fourth cavity 240 and the two third cavities 230 in the diffusion subunit are determined based on the acoustic reflection phase of the diffusion subunit.

[0132] In a preferred embodiment, in step S4, a quadratic residue sequence QRD algorithm is used to form a diffuser with 5 diffuser sub-units, and the acoustic reflection phase of each diffuser sub-unit is respectively 0°, 72°, 288°, 288°, and 72°. The structural parameters of the diffuser sub-unit are adjusted based on the parameters to obtain the required equivalent dynamic mass density and bulk modulus, and then iterative optimization is performed to achieve the expected acoustic reflection phase result.

[0133] In a preferred embodiment, in step S4, the acoustic reflection phase of the diffusion subunit is verified by simulation.

[0134] In order to illustrate the diffusion performance of the diffuser composed of diffusion subunits, the diffusion coefficient is calculated for the diffuse sound field. The calculation expression is:

[0135]

[0136] Among them, L i is the sound pressure level received by the i-th microphone in the diffuse sound field. There are N microphones in the semicircle.

[0137] It should be noted that, in this article, the term "comprises", "includes" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "including one..." do not exclude the presence of other identical elements in the process, method, article or device including the element. In addition, it should be pointed out that the scope of the method and device in the embodiment of the present application is not limited to performing functions in the order shown or discussed, and may also include performing functions in a substantially simultaneous manner or in reverse order according to the functions involved, for example, the described method may be performed in an order different from that described, and various steps may also be added, omitted, or combined. In addition, the features described with reference to certain examples may be combined in other examples.

[0138] The embodiments of the present application are described above in conjunction with the accompanying drawings, but the present application is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present application, ordinary technicians in this field can also make many forms without departing from the purpose of the present application and the scope of protection of the claims, all of which are within the protection of the present application.

Claims

1. An acoustic diffuser based on an acoustic metasurface, characterized in that: It comprises at least one diffusion module, and the diffusion module is provided with at least one diffusion subunit; The diffusion subunit includes a first cavity, a second cavity, a third cavity, and a fourth cavity which are arranged on the diffusion module in the Y-axis direction; The third cavity is arranged between the first cavity and the fourth cavity and is connected to the first cavity and the fourth cavity in the X-axis direction, respectively. Two third cavities are provided, and the two third cavities are symmetrically arranged with respect to the second cavity and are connected to the first cavity respectively. The fourth cavity is connected to the outside of the diffusion module on one side in the Z-axis direction; Wherein, when there are multiple diffusion sub-units on the diffusion module, the multiple diffusion sub-units form a parallel structure, a series structure or a series-parallel composite structure.

2. The acoustic diffuser based on acoustic metasurface according to claim 1, characterized in that: The diffusion module is provided with a plurality of diffusion sub-units, and the plurality of diffusion sub-units form a parallel structure; Wherein, the plurality of diffusion sub-units are arranged in a linear array in the Z-axis direction, and the fourth cavities are interconnected in the Z-axis direction.

3. The acoustic diffuser based on acoustic metasurface according to claim 1, characterized in that: The diffusion module is provided with a plurality of diffusion sub-units, and the plurality of diffusion sub-units form a series structure; One of the diffusion subunits is used as a primary diffusion unit, and the other diffusion subunits are used as secondary diffusion units, and the secondary diffusion units are arranged in the first cavity of the primary diffusion unit; The second diffusion unit omits the fourth cavity, and the second cavity is connected with the first cavity of the first diffusion unit in the Y-axis direction.

4. An acoustic diffuser based on an acoustic metasurface according to any one of claims 1 to 3, characterized in that: The diffusion module is provided with a plurality of diffusion sub-units, and the plurality of diffusion sub-units form a series-parallel composite structure; At least one of the diffusion subunits is used as a secondary diffusion unit, and a plurality of the diffusion subunits are used as primary diffusion units and are arranged in a linear array in the Z-axis direction, and the fourth cavities of the plurality of primary diffusion units are interconnected in the Z-axis direction; A secondary diffusion unit is disposed in the first cavity of at least one of the primary diffusion units, the fourth cavity is omitted from the secondary diffusion unit, and the second cavity is connected to the first cavity of the primary diffusion unit at the corresponding position in the Y-axis direction.

5. The acoustic diffuser based on acoustic metasurface according to claim 1, characterized in that: The diffusion modules are provided in plurality, and the plurality of diffusion modules are fixedly connected and each of the plurality of diffusion modules is provided with at least one diffusion sub-unit.

6. A design method, characterized in that: An acoustic diffuser based on an acoustic metasurface according to any one of claims 1 to 5, comprising: Obtain the equivalent dynamic mass density and bulk modulus of the cavity structure in the acoustic diffuser, and obtain the equivalent impedance matrix of the cavity structure based on the equivalent dynamic mass density and bulk modulus; Based on the equivalent impedance matrix of the cavity structure, the theoretical model results of multiple cavity structures in series and parallel are obtained; The acoustic reflection phase of the diffusion module is obtained based on the theoretical model results of multiple cavity structures connected in series and in parallel; Adjust the structural parameters of the diffusion subunit based on the simulation results of the acoustic reflection phase of the diffusion module, and iteratively optimize to achieve the expected acoustic reflection phase results; Among them, the structural parameters of the acoustic diffuser include the number of diffusion subunits, the connection structure, and the cavity size.

7. A design method according to claim 6, characterized in that: The equivalent impedance matrix of the cavity structure is obtained based on the equivalent dynamic mass density and bulk modulus: The wave number and characteristic impedance of the cavity structure are obtained based on the equivalent dynamic mass density and bulk modulus, and the equivalent impedance matrix of the cavity structure is obtained based on the wave number and characteristic impedance of the cavity structure.

8. A design method according to claim 6 or 7, characterized in that: The equivalent dynamic mass density and bulk modulus of the cavity structure are obtained as follows: Equivalent dynamic mass density: Bulk modulus: in, i is the imaginary unit, w is the cavity scale factor, ω is the angular frequency, ρ0 is the air density, η0 is the dynamic viscosity, K0 is the air bulk modulus, P r is the Prandtl number, γ is the specific heat ratio of air; The wave number and characteristic impedance of the cavity structure are obtained as follows: Wave number: Characteristic impedance: Where, L is the length of the cavity; The method for obtaining the equivalent impedance matrix of the cavity structure is:

9. A design method according to claim 8, characterized in that: The equivalent matrix acquisition method of the theoretical model results of multiple cavity structures in series is: The equivalent matrix acquisition method of the theoretical model results of multiple cavity structures in parallel is: Among them, Z t1 =M t1 (1,1) / M t1 (2,1); Z t1 =M t2 (1,1) / M t2 (2,1).

10. A design method according to claim 9, characterized in that: The method for obtaining the acoustic reflection phase of the diffusion subunit is: φ=arg(R); Among them, the acoustic reflection coefficient of the diffusion subunit is: Impedance of the diffusion subunit: Z0 is the acoustic impedance of air.

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