Copper-lanthanum composite acoustic filter screen

Abstract

The utility model provides a copper-lanthanum composite acoustic filter screen which comprises a copper-lanthanum composite acoustic filter screen body. The utility model discloses a three-layer gradient micropore structure, directional gradient structure acoustic modification device and bionic spiral gradient hole array structure, which is characterized in that through the multi-layer structure design, the three-layer gradient micropore structure with the surface layer of 15 + / -2 microns, the middle layer of 25 + / -3 microns and the bottom layer of 35 + / -5 microns are arranged in a hexagonal honeycomb shape, and the length-diameter ratio is controlled to be 1.2-1.5; in combination with at least one directional gradient modification device such as a bionic spiral gradient hole array and a honeycomb lattice damping structure, an acoustic regulation and control system with precisely matched frequency bands is formed, and the surface layer absorbs gt in a targeted manner; the middle layer realizes acoustic impedance optimization matching, and the bottom layer ensures efficient conduction of airflow, so that the fluctuation of the sound pressure level is controlled at lt; and compared with a metal woven mesh in a traditional scheme, the metal woven mesh is effectively improved by more than three times.

Description

Technical Field

[0001] This utility model relates to the field of headphone acoustic device technology, and more specifically, to a copper-lanthanum composite acoustic filter. Background Technology

[0002] Current in-ear headphone back cover filters are typically made of metal woven mesh or sound-tuning filter cotton. However, the metal woven mesh currently on the market (such as 400-mesh stainless steel mesh) faces problems such as significant high-frequency attenuation (10kHz sound transmission loss ≥3.5dB), low porosity (≤32%), insufficient air permeability (45L / min@10Pa), and phase distortion caused by random pore distribution (group delay >0.2ms). On the other hand, sound-tuning filter cotton (PU foam material) has technical bottlenecks such as weak mechanical strength (tensile strength <50MPa), easy moisture absorption leading to acoustic performance degradation, and severe high-frequency cutoff (20kHz attenuation >8dB).

[0003] Meanwhile, existing technologies also have limitations in the processing of back cover filters for in-ear headphones. Taking metal woven mesh as an example: the process of using mechanical stirring to achieve rare earth mixing cannot achieve precise control of micron-level pore structure. Moreover, the pore density of traditional copper powder sintered filters is ≤20000 pores / cm², and the acoustic impedance is >300Rayl. It is difficult to overcome the technical barriers of high frequency attenuation and the contradiction between air permeability and acoustic fidelity. Therefore, innovative design of materials and structures is needed to solve these problems. Utility Model Content

[0004] An embodiment of this utility model provides a copper-lanthanum composite acoustic filter, which aims to solve the problems mentioned in the background art.

[0005] This utility model embodiment provides a copper-lanthanum composite acoustic filter, comprising:

[0006] A copper-lanthanum composite acoustic filter body, the copper-lanthanum composite acoustic filter body comprising;

[0007] The three-layer gradient microporous structure consists of a surface layer with a pore size of 15±2μm and a porosity of 25%, used for high-frequency standing wave sound absorption, targeting frequencies >5kHz; a middle layer with a pore size of 25±3μm and a porosity of 35%; and a bottom layer with a pore size of 35±5μm and a porosity of 45%. The channels of the three-layer gradient microporous structure are arranged in a hexagonal honeycomb pattern with an aspect ratio of 1.2-1.5.

[0008] A directional step gradient structure acoustic modification device, comprising at least one of the following structures:

[0009] Bionic spiral gradient pore array structure: It adopts a micropore structure with double helixes arranged in an alternating pattern. The inner layer pore size gradient gradually changes from 50μm to 80μm, corresponding to the sensitive frequency band of 3000-6000Hz. The outer layer forms an annular damping band with 120μm equidistant pores. The helix angle is 137.5°.

[0010] Honeycomb lattice damping structure: A hexagonal honeycomb unit matrix is ​​constructed, and a micro Helmholtz resonant cavity with a depth of 0.05 mm is etched on the inner wall of each honeycomb. The cavity diameter varies with the frequency response gradient: 80 μm in the low frequency region <1 kHz, 50 μm in the mid frequency region 1-5 kHz, and 30 μm in the high frequency region >5 kHz. The unit spacing is arranged in the Fibonacci sequence, gradually changing from 1.2 mm to 0.8 mm to 0.5 mm.

[0011] Radial fractal branch structure: Based on Koch snowflake fractal geometry, a three-level branched micropore array is generated. The main branch has a pore diameter of 100μm, corresponding to 1-3kHz; the secondary branch has a pore diameter of 60μm, corresponding to 3-8kHz; and the final branch has a pore diameter of 30μm, corresponding to 8-20kHz. The branch angle is designed according to the fractal dimension D=1.85.

[0012] Vortex-starburst composite structure: The central region adopts a 60° starburst-shaped main hole with a diameter of 200μm, surrounded by three layers of vortex-shaped microporous rings with diameters of 120μm, 80μm, and 50μm respectively. The number of vortex blades in each layer increases in a prime number manner, with 7, 11, and 13 blades respectively.

[0013] In one embodiment of this utility model, the thicknesses of the surface layer, the middle layer, and the bottom layer are 15μm, 25μm, and 35μm, respectively.

[0014] In one embodiment of this utility model, the hexagonal honeycomb-shaped arrangement of the channels has a length-to-diameter ratio of 1.3.

[0015] Compared with the prior art, the beneficial effects of this utility model are:

[0016] 1) This utility model, through a multi-level structural design, uses a three-layer gradient microporous structure of 15±2μm surface layer, 25±3μm middle layer, and 35±5μm bottom layer, arranged in a hexagonal honeycomb pattern, with an aspect ratio controlled at 1.2-1.5. Combined with at least one directional gradient modification device such as a biomimetic spiral gradient hole array and a honeycomb lattice damping structure, it forms an acoustic control system with precise frequency band matching. The surface layer specifically absorbs high-frequency standing waves >5kHz, the middle layer achieves optimized acoustic impedance matching, and the bottom layer ensures efficient airflow conduction, so that the sound pressure level fluctuation is controlled at <±0.8dB, which is more than 3 times more effective than the metal braided mesh in the traditional solution. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this utility model and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 A schematic diagram of the structure of a copper-lanthanum composite acoustic filter provided for an embodiment of this utility model;

[0019] Figure 2 A schematic diagram of the gradient microporous structure of a copper-lanthanum composite acoustic filter provided for an embodiment of this utility model.

[0020] Icons: 100, Copper-Lanternium Composite Acoustic Filter Body; 200, Gradient Microporous Structure; 210, Surface Layer; 220, Middle Layer; 230, Bottom Layer; 300, Directional Gradient Structure Acoustic Modification Device; 310, Bionic Spiral Gradient Pore Array Structure; 320, Honeycomb Lattice Damping Structure; 330, Radial Fractal Branch Structure; 340, Vortex Starburst Composite Structure. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0022] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0023] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0024] In the description of this utility model, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and are not intended to indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model.

[0025] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, "a plurality of" means two or more, unless otherwise explicitly specified.

[0026] In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., 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 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. For those skilled in the art, the specific meaning of the above terms in this utility model can be understood according to the specific circumstances.

[0027] 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.

[0028] Example

[0029] Please see Figure 1-2A copper-lanthanum composite acoustic filter, comprising: a copper-lanthanum composite acoustic filter body 100, the formulation of which includes: copper powder and lanthanum, wherein the copper powder has a D50 of 20 μm and its content ranges from 98.8-99.5 wt%, and the lanthanum exists in the form of La2O3 nanoparticles with a particle size of 50-100 nm and a content range of 0.5-1.2 wt%, and the lanthanum is distributed at the copper grain boundaries; a three-layer gradient microporous structure 200: a surface layer 210 with a pore size of 15±2 μm and a porosity of 25%, used for high-frequency standing wave sound absorption, targeting frequencies >5kHz; a middle layer 220 with a pore size of... The innermost layer has a pore size of 25±3μm and a porosity of 35%. The bottom layer has a pore size of 35±5μm and a porosity of 45%. The three-layer gradient microporous structure has hexagonal honeycomb-like channels with an aspect ratio of 1.2-1.5. The directional gradient structure acoustic modification device 300 includes at least one of the following structures: a biomimetic spiral gradient pore array structure 310: adopts a microporous structure with alternating double helices. The inner layer pore size gradient gradually changes from 50μm to 80μm, corresponding to the sensitive frequency band of 3000-6000Hz. The outer layer forms an annular damping structure with 120μm equidistant pores. The spiral angle is 137.5°; the honeycomb lattice damping structure 320: constructs a hexagonal honeycomb unit matrix, with each honeycomb inner wall etched with a micro Helmholtz resonant cavity to a depth of 0.05 mm. The cavity aperture diameter varies with the frequency response gradient: 80 μm in the low-frequency region <1 kHz, 50 μm in the mid-frequency region 1-5 kHz, and 30 μm in the high-frequency region >5 kHz. The unit spacing is arranged according to the Fibonacci sequence, gradually changing from 1.2 mm to 0.8 mm to 0.5 mm; the radial fractal branch structure 330: based on Koch snowflake fractal geometry. The basic structure generates a three-level branched micropore array. The main branch has a pore diameter of 100μm, corresponding to 1-3kHz; the secondary branch has a pore diameter of 60μm, corresponding to 3-8kHz; and the final branch has a pore diameter of 30μm, corresponding to 8-20kHz. The branch angle is designed according to the fractal dimension D=1.85. The vortex starburst composite structure 340: the central region adopts a 60° starburst-shaped main hole with a diameter of 200μm, surrounded by three layers of vortex-shaped micropore rings with pore diameters of 120μm, 80μm, and 50μm respectively. The number of vortex blades in each layer increases in prime number, with 7, 11, and 13 blades respectively.

[0030] Specifically, in in-ear headphones, copper powder with a D50 of 20μm and 98.8-99.5wt% content, along with 50-100nm, 0.5-1.2wt% La2O3 nanoparticles, are distributed at the copper grain boundaries. The grain boundary segregation effect of lanthanum increases the material's damping coefficient by 40%, reducing energy loss during sound wave propagation. In the three-layer gradient microporous structure 200, the surface layer 210, with a pore size of 15±2μm and a porosity of 25%, forms a dense sound-absorbing barrier for high-frequency sound waves >5kHz. The small aperture restricts sound flow diffusion, and combined with the turbulence suppression effect of the hexagonal honeycomb channel with an aspect ratio of 1.2-1.5, it reduces high-frequency standing wave reflection; the middle layer 220 with a pore size of 25±3μm and a porosity of 35% serves as an acoustic impedance transition layer, adjusting the sound wave transmission resistance through the pore size gradient, so that the acoustic impedance at 1kHz is stabilized at 120-150Rayl; the bottom layer 230 with a pore size of 35±5μm and a porosity of 45% provides a large-aperture channel to ensure airflow conduction and avoid low-frequency distortion caused by insufficient air permeability;

[0031] The directional gradient structure acoustic modification device 300 is precisely optimized according to the needs of different frequency bands: the biomimetic spiral gradient aperture array structure 310 features a double helix with an inner layer of 50-80μm apertures that gradually change in diameter, and an outer layer of 120μm equidistant apertures arranged at a 137.5° golden ratio angle, simulating the frequency response of cochlear hair cells. This guides the sound flow to form a spiral channel in the 3000-6000Hz frequency band, reducing the attenuation of piano overtone peaks by 4.2-5.5dB. The honeycomb lattice damping structure 320 features a Helmholtz resonant cavity with apertures of 80μm in the low-frequency region, 50μm in the mid-frequency region, and 30μm in the high-frequency region, matched with Fibonacci spacing of 1.2mm-0.8mm-0.5mm, achieving optimal performance in the 2000-3000Hz frequency band. The frequency band attenuates the standing wave from 7.5dB to 2.3dB, improving speech intelligibility; the radial fractal branch structure 330 generates three levels of branches using Koch snowflake geometry, with a main branch of 100μm, a secondary branch of 60μm, and a final branch of 30μm. In the 10-16kHz frequency band, the multi-scale diffraction unit attenuates the standing wave by 18-20dB, suppressing diaphragm split vibration; the vortex starburst composite structure 340 has a 200μm starburst main aperture and 120μm, 80μm, and 50μm apertures, and vortex rings with 7 / 11 / 13 blades to form a sound flow convergence-diffusion system. Combined with a lanthanum content gradient substrate, the group delay deviation across the entire frequency band is <±0.8μs, and the phase difference between the left and right channels is reduced from 15° to 5°, optimizing stereo positioning.

[0032] The specific performance comparison data is as follows:

[0033] parameter This utility model Traditional metal woven mesh Tuning filter cotton Acoustic impedance 1kHz, Rayl 120-150 300-400 50-80 Air permeability L / min@10Pa 85±3 45±5 120±10 10kHz attenuation dB 1.2 3.5 6.8 Fatigue lifespan <![CDATA[>1×10 6 ]]> <![CDATA[2×10 5 ]]> <![CDATA[5×10 4 ]]>

[0034] Subsequently, the copper-lanthanum composite acoustic filter of this invention achieves acoustic regulation through the synergistic effect of the material 100 formulation, the three-layer gradient microporous structure 200, and the directional step gradient structure acoustic modification device 300.

[0035] In this embodiment, the thicknesses of the top layer, middle layer, and bottom layer are 15μm, 25μm, and 35μm, respectively.

[0036] Specifically, during the sound output of the headphones, high-frequency sound waves >5kHz first contact the 15μm thick surface layer 210, whose 15±2μm pore size and 25% porosity form a dense sound-absorbing layer. Utilizing the scattering effect of the small pore size on high-frequency sound waves, the attenuation at 10kHz is controlled to 1.2dB. The 25μm thick middle layer 220, with its 25±3μm pore size and 35% porosity, forms an impedance buffer band in the sound wave transmission path, ensuring sound pressure level fluctuations <±0.8dB. The 35μm thick bottom layer 230, with its 35±5μm pore size and 4... With a porosity of 5%, the main airflow channel ensures an air permeability of 85±3L / min@10Pa, avoiding low-frequency response distortion caused by airflow blockage. At the same time, the gradient matching of the thickness and pore size of the three layers allows the sound waves to be gradually controlled from high-frequency absorption and impedance matching to airflow conduction within a total thickness of 0.75μm. Compared with traditional uniform thickness and gradient-free planar filter, the acoustic fidelity is significantly improved, especially in the high-frequency overtone range of violin 8000-10kHz, the standing wave attenuation reaches 9dB, and the energy retention rate is improved by 22%.

[0037] In this embodiment: the hexagonal honeycomb-shaped channels have an aspect ratio of 1.3.

[0038] Specifically, in the headphone acoustic cavity environment, the hexagonal geometric structure has an interior angle of 120°, forming an equilateral triangular support structure between adjacent channels. Compared with circular channels, this increases structural strength by 30%, with a tensile strength of 85MPa. It also reduces acoustic performance degradation caused by channel deformation. The 1.3 aspect ratio design creates an optimal hydrodynamic ratio between channel depth and diameter. When sound waves pass through the channels, the turbulence intensity within the channels is reduced by 3-5dB. In the 20-20kHz frequency band, this avoids additional noise caused by turbulence. At the same time, the reflection path of sound waves from the hexagonal hole walls tends to be consistent, reducing phase distortion and ensuring a group delay error of <0.3μs below 10kHz. In the high-frequency response of the headphones, this structure, combined with the 15μm aperture of the 210 surface layer, improves the sensitivity of the 20-22kHz ultra-high frequency range by 1.2dB, preserving overtones that exceed the upper limit of human hearing. In contrast, traditional filters suffer from over 8dB energy attenuation in ultra-high frequencies due to channel turbulence and phase distortion.

[0039] The specific acoustic performance tests are as follows:

[0040] Testing Standard: IEC 60318-4 Artificial Ear Simulation

[0041] result:

[0042] frequency Hz Sound transmission loss dB Phase delay ms 1000 0.02 0.02 5000 0.04 0.05 10000 0.04 0.08

[0043] The copper-lanthanum composite acoustic filter is prepared by laser sintering, specifically including the following steps:

[0044] S1, Powder pretreatment: Copper powder with a D50 of 20 μm and La2O3 nanopowder with a particle size of 50 nm were ball-milled for 2 hours at a speed of 300 rpm, so that the tap density of the mixture was ≥4.5 g / cm³ and the mixing uniformity CV was ≤5%;

[0045] S2, Gradient Energy Sintering: Laser sintering is performed on a three-layer gradient microporous structure. The surface layer has a laser power of 150W, a scanning speed of 800mm / s, and an energy density of 80-100J / cm²; the middle layer has a laser power of 120W, a scanning speed of 1000mm / s, and an energy density of 60-80J / cm²; and the bottom layer has a laser power of 90W, a scanning speed of 1200mm / s, and an energy density of 40-60J / cm².

[0046] S3, Post-treatment: Annealing is performed under an argon + 3% H2 protective atmosphere at a temperature of 400℃ for 1 hour. Afterward, a 5μm polyurethane hydrophobic layer is sprayed onto the filter screen surface to make the contact angle >120°.

[0047] Specifically, in the laser sintering preparation of copper-lanthanum composite acoustic filters, the precise control of filter structure and performance is achieved through the synergistic process of powder pretreatment (S1), gradient energy sintering (S2), and post-treatment (S3). In the powder pretreatment stage, 20μm copper powder and 50nm La2O3 nanoparticles are ball-milled at 300rpm for 2 hours to ensure uniform distribution of lanthanum at the copper grain boundaries, achieving a mixing uniformity (CV) ≤ 5% and a tap density ≥ 4.5g / cm³. During gradient energy sintering, the surface layer 210 uses a 150W laser power and a scanning speed of 800mm / s, with an energy density of 80-100J / cm². This high energy density ensures the forming accuracy of the 15μm small pores and avoids pore blockage caused by insufficient powder melting. The middle layer 220 uses a 120W power, a 1000mm / s speed, and an energy density of 60-80J / cm². m² sintering balances the forming strength and porosity of the 25μm pore size. The bottom layer, 230, uses 90W power at 1200mm / s speed and 40-60J / cm² to reduce the melting depth, ensuring the continuity of the 35μm pore size. The 1064nm laser wavelength has a high match with the absorption rate of the copper powder, reducing energy loss. In post-treatment, 400℃ argon + H2 annealing eliminates sintering stress, improves material ductility, and achieves a tensile strength of 85MPa. A 5μm polyurethane hydrophobic layer with a contact angle >120° prevents sweat corrosion, resulting in a fatigue life >1×10⁻⁶. 6 The next step, ultrasonic cleaning, removes residual powder from the surface, ensuring the pores are clean.

[0048] In this embodiment: In the gradient energy sintering of step S2, the energy density of the surface layer is 90 J / cm², the energy density of the middle layer is 70 J / cm², and the energy density of the bottom layer is 50 J / cm².

[0049] Specifically, when the energy densities of the surface layer, middle layer, and bottom layer are 90 J / cm², 70 J / cm², and 50 J / cm², respectively, the laser energy is precisely coupled with the three-layer structure. The surface layer 210, with an energy density of 90 J / cm², fully melts the copper powder and La₂O₃ nanoparticles, achieving a pore wall smoothness Ra < 1.6 μm with a pore size of 15 μm, reducing acoustic flow friction loss. Combined with the 137.5° angle of the biomimetic spiral pore 310, this reduces the attenuation of the mid-to-high frequency overtone peaks in the 3200-4500 Hz range by 4.2-5.5 dB. The middle layer 220, with an energy density of 70 J / cm², forms a semi-molten sintered neck with a pore size of 25 μm, ensuring structural strength while retaining 35% porosity for use in... Acoustic impedance matching, combined with the Helmholtz resonant cavity of the honeycomb lattice damping structure 320, attenuates the high-frequency standing wave of 8000-10kHz by 9dB; the bottom layer 230 melts only the powder surface with an energy density of 50J / cm², forming a 35μm through-hole, and the 45% porosity ensures airflow conduction. Combined with the final 30μm branches of the radial fractal branch structure 330, the energy retention rate of the ultra-high frequency of 18-20kHz is increased by 22%. Therefore, the energy gradient design controls the sintering density of the three-layer structure to 88%, 82%, and 75% respectively, corresponding to a gradual decrease in acoustic impedance from the surface to the bottom layer, forming a uniform impedance curve of 120-150Rayl, with fluctuation of <±1.5Ω in the 1-20kHz range.

[0050] In the ball milling process, the grinding media is agate balls. When agate balls are used as the ball milling mixing media, grinding at 300 rpm for 2 hours can achieve uniform dispersion of copper powder and La2O3 nanoparticles without impurities. The Mohs hardness of agate balls is 7-7.5, which is higher than that of copper powder and La2O3. The wear of agate balls during the grinding process is minimal, avoiding the introduction of impurities that may affect the electrical conductivity and acoustic damping characteristics of the material. The electrical conductivity is 85% IACS.

[0051] By utilizing the collision and rolling action of agate balls during ball milling, 50nm La2O3 nanoparticles are uniformly embedded into the gaps between 20μm copper powder particles. They are distributed on the surface of copper powder through a cold welding effect and are then precisely positioned at the copper grain boundaries after subsequent sintering, achieving grain boundary segregation of lanthanum. This increases the material's damping coefficient from 0.05 to 0.07, effectively absorbing the mechanical vibration energy in the propagation of sound waves.

[0052] The process includes an ultrasonic cleaning step after annealing, using anhydrous ethanol as the cleaning solution and a cleaning time of 15-20 minutes. Adding an ultrasonic cleaning step after annealing, using anhydrous ethanol as the cleaning material and cleaning for 15-20 minutes, can remove residual sintering aids and oxides from the filter surface, ensuring unobstructed pores.

[0053] During ultrasonic cleaning, anhydrous ethanol generates a cavitation effect under high-frequency vibration, impacting the inner wall and gaps of the pores, peeling off and dissolving impurity particles with a diameter >5μm, achieving a pore cleanliness of over 99%. After cleaning, the throughput of the 15±2μm pores on the surface layer 210 increases to 98%, and the air permeability increases from 80L / min@10Pa to 85±3L / min@10Pa. At the same time, it reduces the scattering of acoustic flow by impurities, reducing 5kHz harmonic distortion from 0.8% to 0.35%. It is particularly effective in cleaning the 0.05mm deep Helmholtz resonant cavity of the honeycomb lattice damping structure 320, avoiding resonant frequency shift caused by cavity blockage, and ensuring precise matching of acoustic resonance effects at the 80μm cavity opening in the low-frequency region and the 50μm cavity opening in the mid-frequency region.

[0054] The polyurethane hydrophobic layer is applied using electrostatic spraying. When preparing the 5μm polyurethane hydrophobic layer using electrostatic spraying, a uniform and dense protective film is formed on the filter surface. During electrostatic spraying, polyurethane droplets become negatively charged under the influence of a high-voltage electric field and migrate towards the positively charged filter surface. Nanoscale spreading is achieved using Coulomb force, with film thickness uniformity controlled within ±0.5μm. This avoids the pore blockage caused by uneven thickness in traditional spraying. Furthermore, the hydrophobic layer has a contact angle >120°, effectively blocking the intrusion of sweat, water vapor, and other liquids, preventing copper powder oxidation and La2O3 hydrolysis, and ensuring the filter maintains stable acoustic impedance even in humid environments.

[0055] For the 200μm starburst main pores and 50μm eddy current micropores of the 340 eddy current starburst composite structure, electrostatic spraying can precisely control the film thickness without affecting the pore size, while improving surface wear resistance and enabling fatigue life to exceed 1×10 6 In the second cycle, the low surface energy of the hydrophobic layer reduces dust adhesion and maintains a long-term stable density of 27,000 pores / cm², avoiding acoustic performance degradation caused by pore blockage.

[0056] In the gradient energy sintering process of step S2, a laser wavelength of 1064nm is used. When laser sintering uses a wavelength of 1064nm, it matches the optical absorption characteristics of copper powder, improving energy utilization and sintering precision. 1064nm is in the near-infrared band, and the absorption rate of copper powder at this wavelength is about 30%. The laser energy can effectively penetrate the powder surface, allowing 20μm copper powder and 50nm La2O3 nanoparticles to melt simultaneously, forming a uniform copper-lanthanum solid solution. Moreover, the focused beam diameter of the wavelength can be controlled within 50μm, meeting the 15±2μm pore size forming requirement of the surface layer 210, avoiding pore adhesion caused by large beams. At the same time, the excitation effect of this wavelength laser on lanthanum is relatively weak, avoiding the overheating decomposition of La2O3 nanoparticles, ensuring the uniform distribution of lanthanum at the copper grain boundaries, and maintaining a stable material damping coefficient of 0.07.

[0057] In step S1, the powder pretreatment involves drying the mixed powder at 100-120℃ for 2-3 hours. During ball milling, the copper powder and La2O3 nanoparticles adsorb moisture from the air. This moisture vaporizes during laser sintering, creating pores and reducing the 15μm pore size penetration rate of the surface layer 210. Microcracks also form inside the filter, lowering the tensile strength from 85MPa to 70MPa. The drying process ensures a powder moisture content of <0.05%, preventing gas escape and resulting pore defects during sintering, thus guaranteeing the integrity of the three-layer gradient microporous structure 200. The molding precision is improved. For the 0.05mm Helmholtz resonant cavity of the honeycomb lattice damping structure 320, the sintering density of the dried powder is increased by 5%, the cavity wall integrity is better, and the resonance effect is more significant. This reduces the mid-frequency standing wave of 2000-3000Hz from 7.5dB to 2.3dB. The flowability of the dried powder is also improved. During the powder spreading process, it can be filled more evenly into the three-level branch micropores of the radial fractal branch structure 330, avoiding branch breakage caused by powder accumulation. This ensures the design effect of 18-20dB attenuation of ultra-high frequency standing wave of 10-16kHz.

[0058] It should also be noted that:

[0059] Lanthanum substitution: Cerium (Ce) can be used to partially replace lanthanum (La / Ce=7:3), and the acoustic impedance can be maintained at 140-160 Rayl.

[0060] Hole design: The circular pores with a diameter of 20μm, combined with a diamond arrangement, still achieve a density of 27,000 pores / cm²;

[0061] Sintering process: Electron beam melting (EBM) replaces laser sintering, and the energy density is adjusted to 50-80 J / cm².

[0062] The above are merely preferred embodiments of this utility model and are not intended to limit the scope of this utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A copper-lanthanum composite acoustic filter, characterized in that, include: A copper-lanthanum composite acoustic filter body (100), the copper-lanthanum composite acoustic filter body (100) comprising: The three-layer gradient microporous structure (200) has the following characteristics: the surface layer (210) has a pore size of 15±2μm and a porosity of 25%; the middle layer (220) has a pore size of 25±3μm and a porosity of 35%; and the bottom layer (230) has a pore size of 35±5μm and a porosity of 45%. The channels of the three-layer gradient microporous structure (200) are arranged in a hexagonal honeycomb pattern with an aspect ratio of 1.2-1.

5. A directional step gradient structure acoustic modification device (300) includes at least one of the following structures: Bionic spiral gradient hole array structure (310): It adopts a micropore structure with double helixes arranged in an alternating pattern. The inner layer pore size gradient gradually changes from 50μm to 80μm, corresponding to the sensitive frequency band of 3000-6000Hz. The outer layer forms an annular damping band with 120μm equidistant holes and the helix angle is 137.5°. Honeycomb lattice damping structure (320): Construct a hexagonal honeycomb unit matrix, with each honeycomb inner wall etched with a micro Helmholtz resonant cavity to a depth of 0.05 mm. The unit spacing is arranged in the Fibonacci sequence, gradually changing from 1.2 mm to 0.8 mm to 0.5 mm. Radial fractal branch structure (330): Based on Koch snowflake fractal geometry, a three-level branched micropore array is generated. The main branch has a pore diameter of 100μm, corresponding to 1-3kHz, the secondary branch has a pore diameter of 60μm, corresponding to 3-8kHz, and the final branch has a pore diameter of 30μm, corresponding to 8-20kHz. The branch angle is designed according to the fractal dimension D=1.

85. Vortex starburst composite structure (340): The central region adopts a 60° starburst-shaped main hole with a diameter of 200μm, surrounded by three layers of vortex-shaped microporous rings with pore diameters of 120μm, 80μm and 50μm respectively. The number of vortex blades in each layer increases in a prime number manner, with 7, 11 and 13 blades respectively.

2. The copper-lanthanum composite acoustic filter according to claim 1, characterized in that, The thicknesses of the top layer, middle layer, and bottom layer are 15 μm, 25 μm, and 35 μm, respectively.

3. The copper-lanthanum composite acoustic filter according to claim 1, characterized in that, The hexagonal honeycomb-shaped arrangement of the channels has an aspect ratio of 1.3.

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