Acoustic metamaterial silencing structure and preparation method thereof

Abstract

The invention belongs to the technical field of acoustic metamaterials, and discloses an acoustic metamaterial silencing structure and a preparation method thereof. The structure comprises a microwell plate structure layer, a porous material structure layer and an acoustic metamaterial unit array structure layer, the microwell plate structure layer is provided with a first sound absorption channel group, and the microwell plate structure layer is closer to the sound source side than the porous material structure layer; the porous material structure layer is provided with a second sound absorption channel group; the acoustic metamaterial unit array structure layer is arranged between the microplate structure layer and the porous material structure layer and comprises a silencing unit group, the silencing unit group comprises a plurality of silencing units which are arranged in the circumferential direction, the silencing units define a silencing cavity, neck channels are arranged on the side walls, facing the silencing cavity, of the silencing units in a protruding mode, and the neck channels are communicated with the silencing cavity. The silencing cavity is communicated with the first sound absorption channel set and the second sound absorption channel set through the neck channel, the inner wall face of the neck channel is limited to form a sound absorption face so that sound wave energy entering and exiting the silencing cavity can be reduced, and the purposes of silencing and noise reduction are achieved while the weight is light.

Description

Technical Field

[0001] This invention relates to the field of acoustic metamaterials technology, and in particular to an acoustic metamaterial sound-absorbing structure and its preparation method. Background Technology

[0002] Noise has become a major form of environmental pollution, and its problems are receiving increasing attention. Aircraft manufacturing involves numerous drilling and riveting processes, generating significant impact noise. This structural and airborne noise propagates within the factory, posing a serious threat to the health and safety of workers and to the environment.

[0003] Currently, noise control mainly relies on traditional porous sound-absorbing materials. However, traditional sound-absorbing materials have weak sound absorption capacity, and based on the law of mass density, to achieve effective noise reduction, the thickness and mass of the sound-absorbing material structure would be very large, which cannot meet the lightweight requirements of practical engineering applications.

[0004] Therefore, it is necessary to design an acoustic metamaterial noise reduction structure and its preparation method to solve the problems existing in the prior art. Summary of the Invention

[0005] One objective of this invention is to provide an acoustic metamaterial sound-absorbing structure that achieves sound reduction and noise reduction while being lightweight.

[0006] To achieve this objective, the present invention adopts the following technical solution: An acoustic metamaterial sound-absorbing structure includes a microporous plate structure layer, a porous material structure layer, and an acoustic metamaterial unit array structure layer, wherein: The microporous plate structure layer is provided with a first sound-absorbing channel group, and the microporous plate structure layer is closer to the sound source side than the porous material structure layer. The porous material structure layer is provided with a second sound-absorbing channel group; The acoustic metamaterial unit array structure layer is disposed between the microporous plate structure layer and the porous material structure layer. The acoustic metamaterial unit array structure layer includes a sound-absorbing unit group, which includes multiple sound-absorbing units arranged circumferentially. The multiple sound-absorbing units enclose a sound-absorbing chamber, and each sound-absorbing unit has a neck protruding from its side wall facing the sound-absorbing chamber. The sound-absorbing chamber is connected to the first sound-absorbing channel group and the second sound-absorbing channel group through the neck, and the inner wall surface of the neck defines a sound-absorbing surface to reduce the sound wave energy entering and exiting the sound-absorbing chamber.

[0007] Preferably, the acoustic metamaterial sound-absorbing structure includes two microporous plate structure layers and two acoustic metamaterial unit array structure layers. Along the direction parallel to the stacking of the microporous plate structure layers, the porous material structure layers, and the acoustic metamaterial unit array structure layers, the two acoustic metamaterial unit array structure layers are spaced apart on one side of the porous material structure layer, and each acoustic metamaterial unit array structure layer has a microporous plate structure layer on the side away from the porous material structure layer.

[0008] Preferably, the first sound-absorbing channel group includes multiple first sound-absorbing channels arranged in the same column, and the aperture of the first sound-absorbing channel is set to a, where a≤0.1mm; and / or, The spacing between adjacent first sound-absorbing channels is set to b, where 5mm ≤ b ≤ 10mm.

[0009] Preferably, the second sound-absorbing channel group includes a plurality of second sound-absorbing channels arranged in an array, and the pore size of the second sound-absorbing channel is set to c, 50μm≤c≤200μm; and / or, the porosity of the second sound-absorbing channel group is less than 50%.

[0010] Preferably, the porous material structure layer includes one of the following structures: Gyroid surface structure, Schwarz surface structure, Diamond surface structure, and Lidinoid surface structure.

[0011] Preferably, the silencing unit includes a fixed base plate and extensions, with at least two extensions spaced apart on the side of the fixed base plate facing the silencing chamber, and the space between adjacent extensions defining the neck. The anechoic units are arranged rotationally symmetrically around a direction perpendicular to the stacked arrangement of the microporous plate structure layer, the porous material structure layer, and the acoustic metamaterial unit array structure layer. The fixing substrates of two anechoic units in the anechoic unit group are parallel to the horizontal surface of the porous material structure layer, wherein: The fixed substrate of the silencing unit near the horizontal surface has a through hole group, which is used to connect the silencing chamber to the second sound absorption channel group; The fixed substrate of the silencing unit, which is located away from the horizontal surface, defines the microporous plate structure layer and has the second sound-absorbing channel group.

[0012] Preferably, the extension and the fixed base plate have an inclined angle; three extensions are spaced apart on the fixed base plate to form two inclined necks on the silencing unit; a bend is provided on the extension at the tail end; the bend, the fixed base plate and the extension partially enclose to form an opening groove; the opening groove is connected to the silencing chamber. In two adjacent silencing units, the extension portion of the upstream silencing unit located at the head and middle positions is inserted into the opening groove of the downstream silencing unit, and the bent portion of the downstream silencing unit is inserted into the neck of the upstream silencing unit, with the extension portion located at the middle and tail positions of the upstream silencing unit on both sides of the neck being the upstream silencing unit.

[0013] Preferably, the thickness d of the extension is 10mm-50mm; and / or, the thickness e of the bend is 10mm-50mm.

[0014] Preferably, a sound-absorbing gap is provided between adjacent sound-absorbing units, and the sound-absorbing gap is connected to the open groove.

[0015] Preferably, the acoustic metamaterial sound-absorbing structure includes a frame with an internal cavity. The microporous plate structure layer and the acoustic metamaterial unit array structure layer are housed within the frame, and the porous material structure layer is disposed at the end of the frame. The frame, the microporous plate structure layer, the acoustic metamaterial unit array structure layer, and the porous material structure layer are integrally formed.

[0016] Another objective of this invention is to provide a method for preparing an acoustic metamaterial noise reduction structure. The acoustic metamaterial noise reduction structure prepared by this method can achieve noise reduction while achieving lightweight design.

[0017] To achieve this objective, the present invention adopts the following technical solution: A method for preparing an acoustic metamaterial noise-absorbing structure, used to prepare the acoustic metamaterial noise-absorbing structure as described above, the method comprising the following preparation steps: S1. In the first sound-absorbing channel group of the microporous plate structure layer, the aperture of the first sound-absorbing channel and the spacing between adjacent first sound-absorbing channels are designed, and the acoustic metamaterial unit array structure layer and the porous material structure layer are structurally designed. S2. Couple the microporous plate structure layer, the acoustic metamaterial unit array structure layer and the porous material structure layer to form a modeling unit; S3. Determine the materials of the microporous plate structure layer, the acoustic metamaterial unit array structure layer, and the porous material structure layer; S4. The modeling unit is processed into shape.

[0018] The beneficial effects of this invention are: This invention provides an acoustic metamaterial anechoic structure and its preparation method. The acoustic metamaterial anechoic structure is compact and rationally designed. The microporous plate structure layer can dissipate mid-frequency sound energy through the microporous acoustic impedance effect, while the porous material structure layer can dissipate high-frequency sound waves through viscous friction and thermal conduction. The neck channel-anechoic chamber structure of the acoustic metamaterial unit array structure layer constitutes a Helmholtz resonator. By adjusting the neck channel length or cross-sectional area and the volume of the anechoic chamber, the target low-frequency band can be precisely matched, enabling targeted sound absorption for specific low-frequency sound waves. After the sound wave enters the neck channel from the first sound absorption channel, the sound absorption surface formed on the inner wall of the neck channel dissipates through multiple reflections and eddy currents, significantly increasing the propagation path of the sound wave in the neck channel. This improves the low-frequency sound absorption performance that is difficult to cover by the porous material structure layer and the microporous plate structure layer, thus forming a continuous spectrum coverage of "low-frequency resonance + mid-to-high frequency porous sound absorption". This achieves multi-level stepped attenuation of sound wave energy, effectively broadens the sound absorption bandwidth to the full frequency domain, and meets the requirements of lightweight structure. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the acoustic metamaterial noise reduction structure provided by the present invention; Figure 2 This is an isometric view of the noise reduction unit group provided by the present invention; Figure 3 This is a front view of the noise reduction unit assembly provided by the present invention; Figure 4 This is a top view of the acoustic metamaterial noise reduction structure provided by the present invention; Figure 5 This is an isometric view of the porous material structure layer provided by the present invention; Figure 6 The acoustic metamaterial sound-absorbing structure provided by this invention is a schematic diagram of the structure after the frame and the porous material structure layer are hidden.

[0020] In the picture: 1. Microporous plate structure layer; 11. First sound absorption channel; 2. Porous material structure layer; 21. Second sound absorption channel; 3. Acoustic metamaterial unit array structure layer; 31. Noise-absorbing unit; 310. Neck; 311. Fixed substrate; 3111. Through hole group; 312. Extension; 313. Bending part; 32. Noise-absorbing chamber; 33. Sound-absorbing gap; 4. Framework. Detailed Implementation

[0021] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0022] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0023] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0024] In the description of this embodiment, the terms "upper," "lower," "right," and "left," etc., refer to the orientation or positional relationship shown in the accompanying drawings. They are used only for ease of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first" and "second" are used only for distinction in description and have no special meaning.

[0025] The technical solution provided by the present invention will be described below with reference to the accompanying drawings and specific embodiments.

[0026] Combination Figures 1 to 6As shown, this embodiment provides an acoustic metamaterial noise reduction structure, including a microporous plate structure layer 1, a porous material structure layer 2, and an acoustic metamaterial unit array structure layer 3. Among them, the microporous plate structure layer 1 is provided with a first sound-absorbing channel group, and the microporous plate structure layer 1 is closer to the sound source side than the porous material structure layer 2; the porous material structure layer 2 is provided with a second sound-absorbing channel group; the acoustic metamaterial unit array structure layer 3 is disposed between the microporous plate structure layer 1 and the porous material structure layer 2, and the microporous plate structure layer 1, the acoustic metamaterial unit array structure layer 3 and the porous material structure layer 2 are stacked along the X-axis direction in the figure; the acoustic metamaterial unit array structure layer 3 includes a sound-absorbing unit group, which includes multiple sound-absorbing units 31 arranged circumferentially, and the multiple sound-absorbing units 31 enclose a sound-absorbing chamber 32, and the sound-absorbing units 31 have a neck channel 310 protruding from the side wall of the sound-absorbing chamber 32, the sound-absorbing chamber 32 is connected to the first sound-absorbing channel group and the second sound-absorbing channel group through the neck channel 310, and the inner wall surface of the neck channel 310 is defined to form a sound-absorbing surface to reduce the sound wave energy entering and exiting the sound-absorbing chamber 32.

[0027] The acoustic metamaterial anechoic structure provided in this embodiment is compact and rationally designed. The microporous plate structure layer 1 can dissipate mid-frequency acoustic energy (e.g., 500–2000Hz) through the microporous acoustic impedance effect, while the porous material structure layer 2 can dissipate high-frequency sound waves (e.g., >2000Hz) using viscous friction and thermal conduction. The neck channel 310-anechoic chamber 32 structure of the acoustic metamaterial unit array structure layer 3 constitutes a Helmholtz resonator. By adjusting the length or cross-sectional area of ​​the neck channel 310 and the volume of the anechoic chamber 32, the target low frequency can be precisely matched. The range (e.g., 100-500Hz) enables targeted sound absorption for specific low-frequency sound waves. After the sound wave enters the neck channel 310 from the first sound absorption channel 11, the sound absorption surface formed on the inner wall of the neck channel 310 undergoes multiple reflections and eddy current dissipation, significantly increasing the propagation path of the sound wave in the neck channel 310. This enhances the low-frequency sound absorption performance that is difficult to cover by the porous material structure layer 2 and the microporous plate structure layer 1, thereby forming a continuous spectrum coverage of "low-frequency resonance + mid-to-high frequency porous sound absorption", achieving multi-level step-like attenuation of sound wave energy and effectively broadening the sound absorption bandwidth to the full frequency domain.

[0028] Specifically, in this embodiment, as Figure 4 As shown, the first sound-absorbing channel group includes multiple first sound-absorbing channels 11 arranged in the same row. The aperture of the first sound-absorbing channel 11 is set as a, where a≤0.1mm; the spacing between adjacent first sound-absorbing channels 11 is set as b, where 5mm≤b≤10mm.

[0029] For example, the aperture 'a' of the first sound-absorbing channel 11 can be 0.02mm, 0.04mm, 0.06mm, 0.08mm, or 0.1mm; the spacing 'b' between adjacent first sound-absorbing channels 11 can be 5mm, 6mm, 7mm, 8mm, 9mm, or 10mm. By limiting the aperture of the first sound-absorbing channel 11 to within 0-0.1mm, the first sound-absorbing channel group can form a high acoustic impedance microporous array, generating stronger viscous friction when sound waves pass through. The smaller the aperture of the first sound-absorbing channel 11, the more it can enhance the dissipation of mid-frequency sound energy. Furthermore, by combining and adjusting the aperture and spacing 'b' of the first sound-absorbing channel 11, the dual technical effects of precisely adjustable resonant frequency and on-demand amplification of sound absorption coefficient can be achieved without increasing additional layer thickness or weight. This upgrades the noise reduction performance of the microporous plate structure layer 1 from a fixed frequency point to an adjustable mid-frequency sound-absorbing module.

[0030] Specifically, in this embodiment, reference Figure 5 As shown, the second sound-absorbing channel group includes multiple second sound-absorbing channels 21 arranged in an array. The aperture of the second sound-absorbing channel 21 is set to c, where 50μm≤c≤200μm. In addition, the porosity of the second sound-absorbing channel group is specified to be less than 50%.

[0031] For example, the pore size c of the second sound-absorbing channel 21 can be 50μm, 100μm, 150μm, or 200μm. A pore size of 50-200μm is located at the interface between micropores and mesopores, maintaining low airflow resistance while generating considerable viscous-thermal boundary layer loss on the pore walls of the second sound-absorbing channel 21, providing additional absorption of high-frequency sound waves, thus compensating for the insufficient high-frequency sound wave absorption capacity of the microporous plate structure layer 1. Furthermore, a porosity of less than 50% effectively ensures that the porous material structure layer 2 as a whole still has sufficient rigidity and will not collapse due to excessive pores, guaranteeing the overall structural stability of the sound-absorbing structure.

[0032] Furthermore, in this embodiment, the porous material structure layer 2 includes one of the following structures: a Gyroid surface structure, a Schwarz surface structure, a Diamond surface structure, and a Lidinoid surface structure. By replacing the traditional disordered foam with triple-periodic minimal surfaces such as Gyroid, Schwarz, Diamond, or Lidinoid, the porous material structure layer 2 can further improve the sound absorption coefficient under the constraint of the same porosity and pore size. Simultaneously, the overall weight of the structure can be further reduced, and the thickness can be effectively controlled, for example, within a thickness range of 10-20 mm, thus obtaining a "lightweight-wideband-high load-bearing integrated" noise reduction module.

[0033] refer to Figure 3As shown, the anechoic unit 31 specifically includes a fixed substrate 311 and extensions 312. At least two extensions 312 are spaced apart on the side of the fixed substrate 311 facing the anechoic chamber 32, and the space between adjacent extensions 312 defines a neck 310. The anechoic unit 31 is positioned around the stacked direction of the vertical microporous plate structure layer 1, the porous material structure layer 2, and the acoustic metamaterial unit array structure layer 3. Figure 2 The sound-absorbing unit group is arranged with rotational symmetry along the Y-axis. The fixing substrate 311 of two of the sound-absorbing units 31 is parallel to the horizontal surface of the porous material structure layer 2. In these two sound-absorbing units 31, a reference... Figure 1 As shown, the fixing substrate 311 of the silencing unit 31 near the horizontal surface has a through hole group 3111, which is used to connect the silencing chamber 32 to the second sound absorption channel group; the fixing substrate 311 of the silencing unit 31 away from the horizontal surface defines a microporous plate structure layer 1 and has a second sound absorption channel group.

[0034] In practical use, combine Figures 1 to 5 As shown, when the sound wave enters the neck channel 310 from the first sound absorption channel 11, it is transmitted along the neck channel 310 to the anechoic chamber 32. Since the anechoic chamber 32 is formed by multiple anechoic units 31, the sound wave in the anechoic chamber 32 will be transmitted to the neck channel 310 of any remaining anechoic unit 31. Thus, under the synergistic effect of multiple anechoic units 31, the low-frequency sound wave is absorbed and dissipated, while the high-frequency sound wave will pass through the anechoic chamber 32 and the through-hole group 3111 in sequence into the second sound absorption channel group of the porous material structure layer 2 and be absorbed by the porous material structure layer 2. With the above configuration, the fixed substrate 311 of the silencing unit 31, which is far from the porous material structure layer 2 in the silencing unit group, can serve as the microporous plate structure layer 1. This integrates the microporous plate structure layer 1 and the acoustic metamaterial unit array structure layer 3 into a single design, allowing the silencing structure provided in this embodiment to be optimized from a discrete multilayer stacked structure design to a topological continuum structure. The structure is simpler and lighter, providing a high-quality noise reduction solution for aerospace, energy equipment and other fields.

[0035] More specifically, in this embodiment, the extension 312 and the fixed substrate 311 have an inclined angle, so that the length of the extension 312 is increased, thereby lengthening the reflection path of the sound wave in the neck channel 310 and increasing the number of reflections of the sound wave in the neck channel 310, thereby further improving the sound absorption and noise reduction function of the silencing unit 31; in addition, referring to Figure 4As shown, in this embodiment, three extensions 312 are spaced apart on the fixed substrate 311 to form two inclined necks 310 on the silencing unit 31. A bend 313 is provided on the tail end of the extension 312. The bend 313, the fixed substrate 311, and the extension 312 partially enclose each other to form an opening groove, which communicates with the silencing chamber 32. In two adjacent silencing units 31 of a silencing unit group, the extensions 312 located at the beginning and middle positions of the upstream silencing unit 31 are inserted into the opening groove of the downstream silencing unit 31. The bend 313 of the downstream silencing unit 31 is inserted into the neck 310 of the upstream silencing unit 31, with the extensions 312 located at the middle and tail ends of the upstream silencing unit 31 on either side of the neck 310.

[0036] It is understood that in this embodiment, the fixed substrate 311 on a single silencing unit 31 is provided with two rows of first sound-absorbing channel groups, each row of first sound-absorbing channel groups corresponding to a neck channel 310. Furthermore, by providing the bending portion 313, on the one hand, the opening groove (as shown in region ① in the figure) formed by the bending portion 313, the fixed substrate 311, and the extension portion 312 can be used to insert the extension portion 312 located at the beginning and middle positions of the silencing unit 31 on the upstream side of the rotation, so that the neck channel 310 formed by the extension portion 312 located at the beginning and middle positions can communicate with the opening groove, and the sound waves transmitted from the neck channel 310 can be reflected again by the wall surface of the opening groove, increasing the reflection rate. The number of reflections increases, thereby further reducing the energy of low-frequency sound waves output from the anechoic chamber 32. On the other hand, by inserting the bend 313 into the neck channel 310 of the upstream anechoic unit 31, the bend 313 divides the neck channel 310 into two branches. Sound waves transmitted from the first sound-absorbing channel group into the neck channel 310 are reflected in the two branches, further increasing the sound wave reflection path and thus further reducing the energy of low-frequency sound waves output from the neck channel 310. Through the above design, the low-frequency sound wave noise reduction function of the anechoic unit group provided in this embodiment is significantly improved, ensuring the health of operators and reducing structural fatigue failure caused by low-frequency resonance in industrial equipment.

[0037] Preferably, in this embodiment, the thickness d of the extension 312 is 10mm-50mm; the thickness e of the bending portion 313 is 10mm-50mm. For example, the thickness d of the extension 312 can be 10mm, 20mm, 30mm, 40mm, or 50mm; the thickness e of the bending portion 313 can be 10mm, 20mm, 30mm, 40mm, or 50mm. By coordinating the adjustment of the thicknesses of the extension 312 and the bending portion 313, the absorption frequency range of low-frequency sound waves by the silencing unit 31 can be effectively broadened, thereby providing a reasonable solution for low-frequency noise control under extreme operating conditions.

[0038] Furthermore, in this embodiment, a sound-absorbing gap 33 is provided between adjacent sound-absorbing units 31. The sound-absorbing gap 33 is connected to the opening groove. Compared with a single microporous plate structure layer 1, the combination of sound-absorbing gap 33 can form impedance matching at specific low frequencies (such as below 500HZ), thereby helping to improve low-frequency sound absorption efficiency and peak sound absorption coefficient.

[0039] Optionally, combined Figure 1 , Figure 6 As shown, the sound-absorbing structure provided in this embodiment includes two microporous plate structure layers 1 and two acoustic metamaterial unit array structure layers 3. Along the direction parallel to the stacking of the microporous plate structure layer 1, the porous material structure layer 2, and the acoustic metamaterial unit array structure layer 3, that is, along the direction parallel to the X-axis, the two acoustic metamaterial unit array structure layers 3 are spaced apart on one side of the porous material structure layer 2, and each acoustic metamaterial unit array structure layer 3 has a microporous plate structure layer 1 on the side away from the porous material structure layer 2. Thus, a sound-absorbing structure with the structure of "microporous plate structure layer 1 - acoustic metamaterial unit array structure layer 3 - microporous plate structure layer 1 - acoustic metamaterial unit array structure layer 3 - porous material structure layer 2" is formed along the X-axis. This further enhances the absorption capacity of mid-frequency and low-frequency sound waves, which account for a large proportion of sound. While effectively controlling the cost, weight, and volume occupancy of the sound-absorbing structure, it ensures that the sound-absorbing structure has excellent noise reduction effect, thereby meeting the usage requirements under actual working conditions.

[0040] Of course, in other parallel embodiments, more microporous plate structure layers 1 and more acoustic metamaterial unit array structure layers 3 may be provided, and the present invention is not limited thereto.

[0041] Optionally, the anechoic structure provided in this embodiment further includes a frame 4, with an internal cavity. The microporous plate structure layer 1 and the acoustic metamaterial unit array structure layer 3 are housed within the frame 4, and the porous material structure layer 2 is disposed at the end of the frame 4. The frame 4, the microporous plate structure layer 1, the acoustic metamaterial unit array structure layer 3, and the porous material structure layer 2 are integrally formed. Through the above arrangement, the basic structural form of the anechoic structure can be stably maintained by the frame 4, preventing deformation and damage to the anechoic structure due to external environmental factors. Furthermore, the frame 4 can also integrate multiple anechoic units 31 in the anechoic unit group into a stable structure, facilitating the shaping of the anechoic structure. In addition, the number of acoustic metamaterial unit array structure layers 3 can be designed according to actual working conditions. For example, in this embodiment, the acoustic metamaterial unit array structure layer 3 includes two anechoic unit groups arranged side-by-side. The two anechoic unit groups can be relatively fixed by being jointly fixed inside the frame 4, thereby further improving the low-frequency sound wave absorption capability of the acoustic metamaterial unit array structure layer 3.

[0042] This embodiment also provides a method for preparing an acoustic metamaterial noise-absorbing structure, used to prepare the acoustic metamaterial noise-absorbing structure described above. The preparation method includes the following steps: S1. In the first sound-absorbing channel group of the microporous plate structure layer 1, the aperture of the first sound-absorbing channel 11 and the spacing between adjacent first sound-absorbing channels 11 are designed, and the acoustic metamaterial unit array structure layer 3 and the porous material structure layer 2 are structurally designed.

[0043] In practice, the basic topological structures of the microporous plate structure layer 1, the acoustic metamaterial unit array structure layer 3, and the porous material structure layer 2 are first established in 3D modeling software (such as SolidWorks, Creo, Fusion 360, Meshmixer, etc.). The diameter a of the first sound-absorbing channel 11 in the microporous plate structure layer 1 is required to be less than 0.1 mm. The number of first sound-absorbing channels 11 in each first sound-absorbing channel group is selected according to the actual working conditions. The spacing b between adjacent first sound-absorbing channels 11 is required to be between 5 mm and 10 mm. In the acoustic metamaterial unit array structure layer 3, each sound-absorbing unit group includes four sound-absorbing units 31. The four sound-absorbing units 31 are 90° rotationally symmetrical. The thickness d of the extension 312 and the thickness e of the bending part 313 in the sound-absorbing unit 31 are both required to be within 10 mm to 50 mm. In the porous material structure layer 2, the opening diameter c of the second sound-absorbing channel 21 is required to be within the range of 50 μm to 200 μm. The porosity of the second sound-absorbing channel group is less than 50%.

[0044] S2. Couple the microporous plate structure layer 1, the acoustic metamaterial unit array structure layer 3, and the porous material structure layer 2 to form a modeling unit.

[0045] In specific operation, in this embodiment, taking one of the silencing unit groups as an example, the four silencing units 31 in the silencing unit group are distributed circumferentially around the Y-axis. Among them, two silencing units 31 are parallel to the horizontal surface of the porous material structure layer 2. A through-hole group 3111 is formed on the fixed substrate 311 of the silencing unit 31 near the horizontal surface, and a first sound absorption channel group is formed on the fixed substrate 311 of the silencing unit 31 away from the horizontal surface, so that the microporous plate structure layer 1 and the fixed substrate 311 are integrated into one unit.

[0046] Next, the two sets of silencing unit groups are stacked in a direction parallel to the X-axis. The through-hole group 3111 in the upper silencing unit group needs to be connected to the first sound-absorbing channel group on the lower silencing unit group to ensure that sound waves can enter the lower silencing chamber 32 from the upper silencing chamber 32 through the through-hole group 3111 and the first sound-absorbing channel group, so as to ensure that the porous material structure layer 2 can absorb high-frequency sound waves.

[0047] Subsequently, the two microporous plate structure layers 1 and the two acoustic metamaterial unit array structure layers 3 are housed in the receiving cavity through the frame 4, and the porous material structure layer 2 is placed at the bottom of the frame 4. A modeling unit with the preliminary shape of the acoustic metamaterial sound-absorbing structure is formed by using the Boolean operation combination method.

[0048] S3. Determine the materials of microporous plate structure layer 1, acoustic metamaterial unit array structure layer 3, and porous material structure layer 2.

[0049] In specific operation, the materials of both the microporous plate structure layer 1 and the acoustic metamaterial unit array structure layer 3 are selected as polymer composite materials. The polymer composite materials include a resin matrix and reinforcing fibers. The resin matrix can be selected from one or more of epoxy resin, PA (polyamide), PC (polycarbonate), PEI (polyetherimide), and PEEK (polyether ether ketone). The reinforcing fibers include one or more of glass microspheres, glass fibers, long-cut and short-cut carbon fibers.

[0050] The porous material structure layer 2 is a rigid, ribbed, porous sound-absorbing material, such as a metal-based rigid ribbed material (e.g., gradient aluminum foam), a polymer-based composite porous material (carbon fiber reinforced epoxy resin, PEEK-based biomimetic honeycomb material), or an inorganic non-metallic material (e.g., silicon carbide ribbed mullite foam ceramic), etc. This invention is not limited to these types. Preferably, to reduce the mass proportion of the porous material structure layer 2, the material of the porous material structure layer 2 is a polymer-based composite porous material or an inorganic non-metallic material.

[0051] S4. Process the modeling unit into shape.

[0052] In practice, additive manufacturing technology is used to integrally mold the sound-absorbing structure with multiple materials to improve the strength, durability and stability of the entire structure.

[0053] In the description of this specification, references to terms such as "some embodiments," "other embodiments," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0054] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art will be able to make various obvious changes, readjustments, and substitutions without departing from the scope of protection of the present invention. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. An acoustic metamaterial sound-absorbing structure, characterized in that, It includes a microporous plate structure layer (1), a porous material structure layer (2), and an acoustic metamaterial unit array structure layer (3), wherein: The microporous plate structure layer (1) is provided with a first sound-absorbing channel group, and the microporous plate structure layer (1) is closer to the sound source side than the porous material structure layer (2); The porous material structure layer (2) is provided with a second sound-absorbing channel group; The acoustic metamaterial unit array structure layer (3) is disposed between the microporous plate structure layer (1) and the porous material structure layer (2). The acoustic metamaterial unit array structure layer (3) includes a sound-absorbing unit group, which includes a plurality of sound-absorbing units (31) arranged circumferentially. The plurality of sound-absorbing units (31) enclose a sound-absorbing chamber (32). The sound-absorbing unit (31) has a neck channel (310) protruding from the side wall facing the sound-absorbing chamber (32). The sound-absorbing chamber (32) is connected to the first sound-absorbing channel group and the second sound-absorbing channel group through the neck channel (310). The inner wall surface of the neck channel (310) defines a sound-absorbing surface to reduce the sound wave energy entering and exiting the sound-absorbing chamber (32).

2. The acoustic metamaterial noise reduction structure according to claim 1, characterized in that, The acoustic metamaterial sound-absorbing structure includes two microporous plate structure layers (1) and two acoustic metamaterial unit array structure layers (3). Along the direction in which the microporous plate structure layer (1), the porous material structure layer (2) and the acoustic metamaterial unit array structure layer (3) are stacked, the two acoustic metamaterial unit array structure layers (3) are spaced apart on one side of the porous material structure layer (2), and each acoustic metamaterial unit array structure layer (3) has a microporous plate structure layer (1) on the side away from the porous material structure layer (2).

3. The acoustic metamaterial noise reduction structure according to claim 1, characterized in that, The first sound-absorbing channel group includes multiple first sound-absorbing channels (11) arranged in the same column, and the aperture of the first sound-absorbing channel (11) is set to a, where a≤0.1mm; and / or, The spacing between adjacent first sound-absorbing channels (11) is set to b, 5mm≤b≤10mm.

4. The acoustic metamaterial noise reduction structure according to claim 1, characterized in that, The second sound-absorbing channel group includes multiple second sound-absorbing channels (21) arranged in an array, and the pore size of the second sound-absorbing channel (21) is set to c, 50μm≤c≤200μm; and / or, the porosity of the second sound-absorbing channel group is less than 50%.

5. The acoustic metamaterial noise reduction structure according to claim 1, characterized in that, The porous material structure layer (2) includes one of the following structures: Gyroid surface structure, Schwarz surface structure, Diamond surface structure and Lidinoid surface structure.

6. The acoustic metamaterial sound-absorbing structure according to any one of claims 1-5, characterized in that, The silencing unit (31) includes a fixed base plate (311) and an extension (312). At least two extensions (312) are spaced apart on the side of the fixed base plate (311) facing the silencing chamber (32). The space between adjacent extensions (312) defines the neck (310). The silencing units (31) are arranged in a rotationally symmetrical manner around the direction in which the microporous plate structure layer (1), the porous material structure layer (2), and the acoustic metamaterial unit array structure layer (3) are stacked perpendicular to each other. The fixing substrate (311) of the two silencing units (31) in the silencing unit group is parallel to the horizontal surface of the porous material structure layer (2), wherein: The fixed base plate (311) of the silencing unit (31) near the horizontal surface has a through hole group (3111) for connecting the silencing chamber (32) to the second sound absorption channel group. The fixed substrate (311) of the sound-absorbing unit (31) located away from the horizontal surface defines the microporous plate structure layer (1) and has the second sound-absorbing channel group.

7. The acoustic metamaterial noise reduction structure according to claim 6, characterized in that, The extension (312) and the fixed base plate (311) have an inclined angle; three extensions (312) are spaced apart on the fixed base plate (311) to form two inclined necks (310) on the silencing unit (31); a bend (313) is provided on the extension (312) at the tail end; the bend (313), the fixed base plate (311) and the extension (312) partially enclose to form an opening groove; the opening groove is connected to the silencing chamber (32). In two adjacent silencing units (31), the extension (312) located at the head and middle positions of the silencing unit (31) on the upstream side is inserted into the opening groove of the silencing unit (31) on the downstream side, and the bent portion (313) of the silencing unit (31) on the downstream side is inserted into the neck (310) of the silencing unit (31) on the upstream side, and the two sides of the neck (310) are the extension (312) located at the middle and tail positions of the silencing unit (31) on the upstream side, respectively.

8. The acoustic metamaterial noise reduction structure according to claim 7, characterized in that, The thickness d of the extension (312) is 10mm-50mm; and / or the thickness e of the bending portion (313) is 10mm-50mm.

9. The acoustic metamaterial noise reduction structure according to claim 7, characterized in that, A sound-absorbing gap (33) is provided between adjacent sound-absorbing units (31), and the sound-absorbing gap (33) is connected to the open groove.

10. The acoustic metamaterial noise reduction structure according to claim 6, characterized in that, The acoustic metamaterial sound-absorbing structure includes a frame (4), the frame (4) has a cavity inside, the microporous plate structure layer (1) and the acoustic metamaterial unit array structure layer (3) are housed in the frame (4), the porous material structure layer (2) is disposed at the end of the frame (4), and the frame (4), the microporous plate structure layer (1), the acoustic metamaterial unit array structure layer (3) and the porous material structure layer (2) are integrally formed.

11. A method for preparing an acoustic metamaterial sound-absorbing structure, used to prepare an acoustic metamaterial sound-absorbing structure as described in any one of claims 1-10, characterized in that, The method for preparing the acoustic metamaterial noise-absorbing structure includes the following preparation steps: S1. In the first sound-absorbing channel group of the microporous plate structure layer (1), the aperture of the first sound-absorbing channel (11) and the spacing between adjacent first sound-absorbing channels (11) are designed, and the acoustic metamaterial unit array structure layer (3) and the porous material structure layer (2) are structurally designed. S2. The microporous plate structure layer (1), the acoustic metamaterial unit array structure layer (3) and the porous material structure layer (2) are coupled together to form a modeling unit; S3. Determine the materials of the microporous plate structure layer (1), the acoustic metamaterial unit array structure layer (3), and the porous material structure layer (2); S4. The modeling unit is processed into shape.

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