A double-sided phase gradient composite sound absorption metasurface structure based on porous material and a design method thereof

Abstract

The application discloses a kind of based on porous material's double-side phase gradient composite sound absorption metasurface structure and design method, it is related to acoustic metamaterial and sound absorption metasurface technical field, structure includes: rigid metal frame and multiple periodic arrangement sound absorption metasurface subunit, each subunit is divided into acoustically isolated first, second functional area along the thickness direction, respectively control transmission, reflection sound wave phase, functional area is equipped with rigid baffle and the sound channel of porous sound absorption material in it. By differentiating design subunit parameter, make it form 0~2π phase distribution at target frequency, form phase gradient on both sides, in combination with the period design of λ / d>2, convert high-order diffraction wave into surface wave, cooperate porous material to realize sound energy efficient dissipation.The total thickness of the application is less than 1 / 8 of target wavelength, predetermined frequency band sound absorption coefficient α≥0.8, the performance is stable from-50° to +50° incident angle, adapts to a variety of porous materials and target frequency, widely used in noise control scene.

Description

Technical Field

[0001] This invention relates to the field of acoustic metamaterials technology, and in particular to a double-sided phase gradient composite sound-absorbing metasurface structure and design method based on porous materials, for applications requiring strict control of low-frequency noise and multi-directional incident noise. Background Technology

[0002] With the advancement of urbanization and industrialization, noise problems generated by transportation, industrial equipment, and electromechanical systems are becoming increasingly prominent. Noise pollution not only affects the comfort of living and working environments but may also endanger human health and equipment operation safety. Therefore, higher demands are being placed on technical solutions that combine high-efficiency sound absorption, compact structure, and ease of engineering in fields such as architectural acoustics, traffic noise control, and industrial noise reduction.

[0003] In existing sound absorption technologies, porous and fibrous materials rely on the viscosity and heat dissipation mechanism within the pores to achieve good sound absorption in the mid-to-high frequency range. However, in the low frequency range, due to the long wavelength of sound waves and the difficulty of sound energy penetrating deep into the material, it is often necessary to significantly increase the thickness to ensure sound absorption performance, which is limited by space and cost. Micro-perforated plates and multi-layer composite structures can improve low frequencies or broaden the frequency band to a certain extent, but the former has a relatively narrow frequency band and is sensitive to parameters, while the latter has a complex structure and a large overall thickness, making it difficult to achieve broadband stable sound absorption under ultra-thin conditions.

[0004] In recent years, acoustic metamaterials and acoustic metasurfaces have provided new ideas for acoustic energy manipulation. Subwavelength units based on local resonance or phase modulation can achieve high sound absorption or anomalous reflection and refraction effects at specific frequencies, and have the advantage of thin and light structures. However, existing structures mostly adopt single-sided arrangement or single-sided phase gradient design, resulting in a limited frequency response range; some phase gradient metasurfaces based on the generalized Snell's law focus on beam deflection and surface wave excitation, and do not adequately consider the broadband dissipation potential of porous materials and the synergistic modulation of bilateral phase, making it difficult to simultaneously achieve high-efficiency sound absorption performance in a thin, broadband, and wide incident angle range.

[0005] Therefore, how to effectively combine porous sound-absorbing materials with phase gradient acoustic metasurfaces while maintaining ultra-thin structure and compact arrangement, and promote the conversion of higher-order diffraction waves into surface waves and enhance the coupling and dissipation of sound energy inside the porous medium by introducing a controllable phase gradient distribution on both sides of the metasurface, thereby obtaining sound absorption performance with wide frequency range, high efficiency and wide-angle robustness, has become an important technical problem to be solved in this field. Summary of the Invention

[0006] In view of the difficulty in achieving both ultra-thin design, stable sound absorption over a wide incident angle, and flexible adaptation to multiple frequencies and materials in traditional sound-absorbing structures, this invention proposes a double-sided phase gradient composite sound-absorbing metasurface structure and design method based on porous materials. To solve the above-mentioned technical problems, this invention provides the following technical solution:

[0007] A rigid metal frame that forms the outer contour and internal partitions of the metasurface structure;

[0008] Multiple sound-absorbing metasurface sub-units are periodically arranged along a first direction and connected to the partition;

[0009] Each of the sound-absorbing metasurface subunits is divided along the thickness direction into a first functional area and a second functional area that are acoustically isolated from each other by the partition.

[0010] The first functional area is used to regulate the phase of the transmitted sound wave, and it is equipped with a sound channel defined by a rigid partition and a porous sound-absorbing material.

[0011] The second functional area is used to adjust the phase of the reflected sound wave, and it is equipped with a sound channel defined by a rigid partition and a porous sound-absorbing material.

[0012] In the first direction, the geometric parameters of the first functional area and / or the second functional area and / or the equivalent acoustic parameters of the porous material filled in the different sub-units are different, so that each sub-unit generates different transmission phase and reflection phase on the transmission side and reflection side of the metasurface at the target operating frequency.

[0013] Furthermore, within each cycle, the phase response of each sub-unit on the same side constitutes a discrete phase distribution covering 0 to 2π, thereby forming a predetermined phase gradient on both sides of the metasurface.

[0014] Furthermore,

[0015] The first functional area is located in the upper part of the rigid metal frame, with rigid cover plates at its top and bottom. Inside, multiple rigid partitions of adjustable length are arranged in an alternating or symmetrical manner to form multiple non-interconnected tortuous sound channels. The second functional area is located in the lower part of the rigid metal frame, with at least one rigid partition of adjustable length and position near one side wall, which together with the side wall defines the reflected sound channel.

[0016] Furthermore,

[0017] N sound-absorbing metasurface sub-units are set within one cycle, where N≥4, so that the reflection phase and / or transmission phase difference between adjacent sub-units at the target operating frequency is 2π / N, thereby achieving phase coverage from 0 to 2π within one cycle.

[0018] Furthermore,

[0019] The period length d of the sound-absorbing metasurface subunit along the first direction satisfies λ / d>2 with the acoustic wavelength λ corresponding to the target operating frequency, so that the higher-order diffraction wave is converted into a surface wave propagating along the interface.

[0020] Furthermore,

[0021] The total thickness H of the metasurface structure is less than 1 / 8 of the acoustic wavelength λ corresponding to the target operating frequency. The total thickness H is the sum of the height H1 of the first functional area and the height H2 of the second functional area.

[0022] Furthermore,

[0023] The rigid metal frame and its internal rigid partitions are made of at least one of aluminum alloy, steel or engineering plastic; the porous sound-absorbing material is at least one of melamine foam, porous polyurethane foam, glass wool or mineral wool.

[0024] Furthermore,

[0025] In the first functional area, the equivalent propagation path of the sound channel is adjusted by changing the length and / or position of each rigid partition, thereby achieving fine control of the phase of the transmitted sound wave; in the second functional area, the length of the reflected sound path is adjusted by changing the length of the rigid partition and / or its height from the bottom, thereby achieving control of the phase of the reflected sound wave.

[0026] Furthermore,

[0027] The periodic structure is arranged repeatedly for at least 10 cycles along the first direction and arranged in several rows in a second direction perpendicular to the first direction to form a two-dimensional sound-absorbing metasurface array; the metasurface structure has a sound absorption coefficient α ≥ 0.8 in a predetermined frequency band including the target operating frequency, and the sound absorption coefficient remains stable in the incident angle range of -50° to +50°.

[0028] Furthermore,

[0029] With N=4, the reflection phase and transmission phase of each sub-unit at the target operating frequency are -π / 2, 0, π / 2 and π, respectively.

[0030] A design method for a double-sided phase gradient composite sound-absorbing metasurface structure based on porous materials includes the following steps:

[0031] S1: Based on the target noise control requirements, determine the target operating frequency f0 of the metasurface, and set the total thickness H and period length d of the metasurface according to the corresponding acoustic wavelength λ.

[0032] S2: Determine the number N of sound-absorbing metasurface sub-units in each cycle, and preset the reflection phase and transmission phase of each sub-unit at the target operating frequency f0, so that the phase difference between adjacent sub-units is 2π / N;

[0033] S3: Construct the initial structure of the sub-unit for achieving dual-sided phase modulation, and divide each sub-unit into a first functional region for transmission phase modulation and a second functional region for reflection phase modulation along the thickness direction;

[0034] S4: Based on the equivalent medium model or numerical simulation method of porous materials, calculate the reflection phase, transmission phase and sound absorption coefficient of each sub-unit under different combinations of structural parameters.

[0035] S5: Compare the phase response obtained in step S4 with the target phase set in step S2. By adjusting the geometric dimensions of the rigid partition and the filling area of ​​the porous material, iteratively optimize each sub-unit until double-sided 0 to 2π phase coverage is achieved at the target operating frequency f0.

[0036] S6: Multiple optimized sub-units are periodically arranged in a predetermined phase gradient order to construct a complete double-sided phase gradient composite sound-absorbing metasurface structure.

[0037] The beneficial effects of this invention are as follows:

[0038] This invention achieves a synergistic unity of ultra-thin characteristics and high-efficiency sound absorption through an innovative dual-sided phase gradient composite structure design. The total thickness H of the metasurface is less than 1 / 8 of the wavelength λ of the sound wave corresponding to the target operating frequency, meeting the requirements of subwavelength ultra-thin design. This solves the industry pain point that traditional sound-absorbing materials need to significantly increase their thickness to ensure low-frequency sound absorption performance. At the same time, with the synergistic effect of dual-functional zone phase modulation and porous material dissipation, the sound absorption coefficient α is ≥0.8 in the target frequency band, and the sound absorption coefficient near the target operating frequency even reaches ≥0.9, achieving high-efficiency sound absorption under an ultra-thin structure.

[0039] Each sub-unit is divided into an independent transmission phase control area (first functional area) and a reflection phase control area (second functional area) along the thickness direction. Through periodic arrangement, it achieves 0-2π phase coverage on both sides, and can simultaneously control the wavefront of reflected and transmitted sound waves. Compared with the single-sided phase control structure, it has a wider range of applications and can flexibly adapt to multi-directional noise incident scenarios.

[0040] The period length d satisfies the design condition λ / d>2, converting higher-order diffracted waves into surface waves propagating along the interface. Combined with the viscous dissipation and thermal dissipation mechanisms of porous materials, the sound absorption bandwidth is significantly broadened, and the sound absorption coefficient remains stable over a wide incident angle range of -50° to +50°. This effectively solves the problem of traditional sound absorption structures being sensitive to the incident angle, making it suitable for complex multi-directional noise control scenarios. The structural design has extremely high flexibility and adaptability, supporting a periodic arrangement design of N≥4 (preferably N=4) sub-units. It can be adapted to different target operating frequencies such as 1000Hz, 1500Hz, 2000Hz, and 3000Hz by adjusting the geometric parameters of the sub-units and the equivalent acoustic parameters of the porous materials. It is also compatible with various porous sound-absorbing materials such as melamine foam, porous polyurethane foam, glass wool, and mineral wool, allowing for flexible selection based on engineering costs and environmental requirements, making it highly practical for engineering applications.

[0041] The overall structure adopts a combination of rigid metal frame (aluminum alloy, steel, etc.) and porous sound-absorbing material. The sub-units are arranged periodically and regularly. Mass production can be achieved through conventional processes such as welding, splicing, and embedded filling. The overall structure has low density and light weight. It can be processed into plate-shaped or wall-mounted two-dimensional arrays, and is suitable for installation needs in various engineering scenarios such as architectural acoustics engineering, transportation noise control, and industrial equipment noise reduction.

[0042] Furthermore, this invention provides a complete design process from target setting, structural construction, simulation calculation to optimization and finalization. Based on the Johnson–Champoux–Allard equivalent medium model and numerical simulation method, it achieves precise control of phase response and sound absorption performance, avoids the blindness of traditional sound absorption structure design, ensures the consistency of structural performance in different batches and different application scenarios, and has high repeatability. Attached Figure Description

[0043] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 This is an isometric view of the overall structure of the double-sided phase gradient composite sound-absorbing metasurface of the present invention;

[0045] Figure 2 This is a front view schematic diagram of the overall structure of the double-sided phase gradient composite sound-absorbing metasurface of the present invention;

[0046] Figure 3 This is an isometric view of a single sub-unit of the sound-absorbing metasurface of the present invention;

[0047] Figure 4 This is a front view of a single sub-unit of the sound-absorbing metasurface of the present invention;

[0048] Figure 5 This is a schematic diagram of the sound-absorbing metasurface layer and sub-unit structure with a periodic composite structure according to the present invention;

[0049] Figure 6 This is a schematic diagram of the equivalent sound field of each sub-unit of the sound-absorbing metasurface of the present invention;

[0050] Figure 7 This is a schematic diagram of the phase response between reflected and transmitted waves in each sub-unit of the metasurface of the present invention;

[0051] Figure 8 This is a schematic diagram of a melamine foam sample and its microstructure in one embodiment of the present invention;

[0052] Figure 9 This is a schematic diagram illustrating the extraction of sub-unit phase and sound absorption coefficient in COMSOL Multiphysics according to the present invention;

[0053] Figure 10 This is a schematic diagram of the simulation setup for the present invention;

[0054] Figure 11 This is a graph showing the reflection phase change of each sub-unit in the frequency domain of this invention.

[0055] Figure 12 This is a graph showing the transmission phase variation of each subunit in the frequency domain of this invention.

[0056] Figure 13 This is a graph showing the relationship between relevant parameters of the periodic structure of the present invention when λ / d>2;

[0057] Figure 14 This is a schematic diagram of the simulated scattering pressure field under vertically incident waves at different frequencies according to the present invention;

[0058] Figure 15 This is a schematic diagram of the simulated scattering pressure field at different incident angles at 2000Hz according to the present invention;

[0059] Figure 16 This is a graph showing the sound absorption coefficient of the metasurface and each unit of the present invention.

[0060] Figure 17 This is a graph showing the sound absorption coefficient of the metasurface and each subunit of the present invention at 2000Hz as a function of the incident angle.

[0061] Figure 18 This is a graph showing the sound absorption coefficient of the metasurface and the porous material layer of equal thickness at 2000Hz as a function of the incident angle.

[0062] Figure 19This is a flowchart illustrating the design method of the double-sided phase gradient composite sound-absorbing metasurface structure based on porous materials according to the present invention. Detailed Implementation

[0063] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0064] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0065] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0066] Example 1

[0067] This embodiment is a basic structural design of a double-sided phase gradient composite sound-absorbing metasurface based on melamine foam;

[0068] like Figure 1 , Figure 2 As shown, the dual-phase gradient composite sound-absorbing metasurface structure of this embodiment is constructed entirely of a rigid metal frame. The frame is made of aluminum alloy and welded together, forming the outer contour and internal partitions of the metasurface. It satisfies rigid boundary conditions within the operating frequency band and has no elastic deformation units. Multiple sound-absorbing metasurface sub-units are arranged periodically along a first direction within the frame. The sub-units are fixedly connected to the internal partitions to form a stable periodic structure. By arranging several rows of this periodic structure along a second direction perpendicular to the first direction, a two-dimensional sound-absorbing metasurface array can be formed, adapting to engineering installation requirements.

[0069] like Figure 3 , Figure 4 , Figure 5 As shown, each sound-absorbing metasurface subunit is divided into a first functional area (upper part) and a second functional area (lower part) that are acoustically isolated from each other by an internal partition along the thickness direction. The total thickness H = H1 + H2, where the height of the first functional area H1 = 30 mm, the height of the second functional area H2 = 20 mm, and the total thickness H = 50 mm.

[0070] This embodiment uses a target operating frequency f0=2000Hz as the design benchmark. The sound speed in air of 340m / s corresponds to a sound wavelength λ≈0.17m, and the total thickness H is less than λ / 8 (0.02125m), meeting the subwavelength ultrathin design constraints. Rigid covers are set at the top and bottom of the first functional area. Inside, multiple rigid partitions with adjustable lengths are arranged in an alternating or symmetrical manner to form multiple non-interconnected tortuous sound channels, which are filled with porous sound-absorbing material.

[0071] Inside the second functional area, a rigid partition with adjustable length and position is installed near one side wall, which together with the side wall defines the reflected sound channel, which is also filled with porous sound-absorbing material.

[0072] In this embodiment, the porous sound-absorbing material is melamine foam, such as... Figure 8 As shown, this material is a three-dimensional open-cell lightweight porous material with a porosity of approximately 0.99 and a flow resistance of approximately 1.25 × 10⁻⁶. 4 Pa×s / m 2 The viscosity and thermal characteristic length are at 10 -4 It is on the order of meters and has excellent acoustic impedance matching and wideband dissipation capabilities.

[0073] like Figure 5 As shown, in this embodiment, N=4 sound-absorbing metasurface sub-units are set in each cycle. The length of the sub-unit along the first direction is 21mm, and the total length of the cycle is d=84mm, which satisfies the cycle design condition of λ / d≈2.04>2, allowing the higher-order diffracted wave to be converted into a surface wave propagating along the interface. By changing the length and position of the rigid partition in the first functional area of ​​different sub-units, as well as the length and height from the bottom of the rigid partition in the second functional area, the reflection phase and transmission phase of each sub-unit at the target frequency of 2000Hz are −π / 2, 0, π / 2, and π, respectively, forming a discrete phase distribution covering 0-2π. This creates a predetermined linear phase gradient on both sides of the metasurface, achieving dual-sided wavefront modulation of the reflected and transmitted sound waves.

[0074] It should be noted that N=4 is only a preferred implementation scheme. Depending on the design requirements, N can also take other integers greater than or equal to 4 (such as N=6, N=8, etc.). As long as the reflection phase and / or transmission phase difference between adjacent sub-units at the target operating frequency is 2π / N, phase coverage from 0 to 2π can be achieved within one cycle. The specific value of N can be determined comprehensively based on factors such as the target operating frequency, structural size constraints, and processing accuracy.

[0075] Example 2

[0076] This embodiment demonstrates the numerical simulation verification of the phase response and sound absorption performance of a double-sided phase gradient composite sound-absorbing metasurface. Based on the basic structural parameters of Embodiment 1, the phase modulation capability, surface wave conversion characteristics, and sound absorption performance of the metasurface are verified through numerical simulation. This embodiment uses COMSOL Multiphysics acoustic finite element simulation software and conducts simulations according to the design methodology.

[0077] like Figure 9 , Figure 10 As shown, periodic boundary conditions are applied laterally to the metasurface sub-units in the simulation model. A perfectly matched layer (PML) is set in the far-field region to absorb outgoing waves and eliminate false reflected waves. A plane wave background sound pressure field with an amplitude of 1 Pa is applied to the lower region to simulate the vertical incidence condition. The software's "Pressure Acoustics, Frequency Domain" and "Porous Medium Acoustics, Frequency Domain" physical field interfaces are enabled. The equivalent density and equivalent bulk modulus of melamine foam, solved based on the Johnson–Champoux–Allard (JCA) equivalent medium model, are imported into the model to define the constitutive parameters of the porous medium acoustic region.

[0078] An integration line is set up upstream and downstream of the sub-unit. The complex sound pressure of the reflected and transmitted waves is extracted by line integration. The reflection coefficient and transmission coefficient are obtained by solving. Then, the reflection phase, transmission phase and sound absorption coefficient of the sub-unit are calculated. Based on the sound pressure and particle velocity boundary conditions of the incident region, transmission region and metasurface region, the equivalent impedance and equivalent wavenumber of the metasurface unit are obtained by the equivalent medium inversion method.

[0079] Simulation results are as follows Figure 7 , Figure 11 , Figure 12 As shown, at the target frequency of 2000Hz, the phase response of the transmission and reflection sides of the four sub-units completely covers the range of 0-2π. The phase difference between the reflection and transmission of adjacent sub-units is approximately π / 2, which is consistent with the preset phase gradient in Example 1, thus achieving the design goal of a linear phase gradient on both sides. In the frequency domain of 1000Hz-4000Hz, the phase change trend of each sub-unit is stable, providing a stable phase basis for broadband sound absorption.

[0080] like Figure 13 As shown, under the periodic condition of λ / d>2, the higher-order diffracted waves of the periodic structure no longer enter the far field as propagating waves, but are transformed into surface waves or evanescent waves that propagate along the metasurface interface, thus ensuring efficient dissipation of acoustic energy. The simulation process of this embodiment fully reproduces the steps of equivalent acoustic parameter solving, phase response calculation, and surface wave characteristic analysis in the design method, verifying the core performance of the basic structure of Embodiment 1 at the target frequency.

[0081] Example 3

[0082] This embodiment demonstrates the broadband sound absorption and incident angle robustness verification of the dual-phase gradient composite sound-absorbing metasurface. Based on the simulation model of Embodiment 2, the broadband sound absorption performance and multi-incident angle sound absorption stability of the metasurface are verified, and the performance is compared with that of a traditional uniform porous material layer.

[0083] like Figure 16 As shown, under the condition of perpendicular plane wave incidence, the sound absorption coefficient of the entire metasurface and individual sub-units was calculated as a function of frequency. The results show that the overall sound absorption coefficient of the metasurface remains above 0.9 within a wide frequency range of 1500Hz-3200Hz. It should be noted that the "predetermined frequency band" mentioned in this invention refers to a continuous frequency range centered on the target operating frequency f0 with a sound absorption coefficient α ≥ 0.8. The width of this frequency band varies with different structural parameters and porous materials; in this embodiment, it corresponds to 1500Hz to 3200Hz.

[0084] At the target frequency of 2000Hz, the sound absorption coefficient is close to 0.99, achieving near-perfect sound absorption. The sound absorption coefficient of a single sub-unit is significantly lower than that of the metasurface as a whole, which reflects the broadband sound absorption enhancement effect brought about by the periodic arrangement of multiple units, synergistic effect and surface wave conversion.

[0085] like Figure 14 As shown, for 1400Hz ( Figure 14 a) 1600Hz ( Figure 14 b) 1800Hz Figure 14 c) 2000Hz Figure 14 d) Simulations were performed on the scattering pressure field of vertically incident waves at four frequencies. The results show that at 2000Hz ( Figure 14 d) At the target frequency, obvious surface wave modes appear on both the upper and lower sides of the metasurface. The energy of higher-order reflected and transmitted waves is concentrated near the interface, and the far-field specular reflection energy is significantly reduced. However, when the frequency deviates from 2000Hz, the surface wave conversion effect gradually weakens, the specular reflection energy increases, and the sound absorption performance decreases accordingly. This verifies the key role of the combination of the λ / d>2 condition and the two-sided phase gradient in exciting surface waves and enhancing sound absorption.

[0086] like Figure 15 , Figure 17 As shown, at a target frequency of 2000Hz, 10° ( Figure 15 a) 20° Figure 15 b) 30° Figure 15 c), 40° Figure 15 d) The simulation results show that the overall sound absorption coefficient of the metasurface remains above 0.9 with fluctuations of less than 10% in the wide incident angle range of -50° to +50°, while the sound absorption coefficient of a single sub-unit decreases significantly with the increase of the incident angle.

[0087] like Figure 18 As shown, the sound absorption performance of the metasurface structure of this embodiment is compared with that of a uniform melamine foam layer of the same thickness (50 mm). In the range of 2000 Hz and incident angle of −60° to +60°, the sound absorption coefficient of the metasurface structure is always higher than that of the uniform porous material layer. Especially under large incident angles of ±40° and above, the performance difference is more significant. This verifies that the present invention significantly improves the sound energy utilization efficiency of porous materials by introducing a two-sided phase gradient and surface wave conversion mechanism.

[0088] Example 4

[0089] This embodiment demonstrates the engineered two-dimensional array structure design of a dual-phase gradient composite sound-absorbing metasurface. Based on the basic structure and performance verification results of embodiments 1-3, this embodiment completes the engineered two-dimensional array design of the metasurface, which is suitable for practical engineering scenarios such as architectural acoustics and traffic noise control.

[0090] like Figure 1 , Figure 2 As shown, in this embodiment, the one-dimensional periodic structure of Embodiment 1 is repeated 15 times along the first direction, and 8 rows of periodic structures are arranged along the second direction perpendicular to the first direction to form a plate-shaped two-dimensional sound-absorbing metasurface array with a size of 600mm×400mm. The array as a whole can be cut to size according to engineering installation requirements. The core structural parameters are consistent with those of Embodiment 1, and the total thickness is still 50mm, which meets the space constraints of the engineering scenario.

[0091] like Figure 5 As shown, in order to reduce the phase crosstalk caused by acoustic field coupling between adjacent sub-units and adjacent cycles and to ensure the effectiveness of phase gradient design, rigid partition walls are set between each sub-unit and between adjacent cycles, so that the incident sound wave mainly interacts with the porous material and partition structure within the current sub-unit, thereby improving the accuracy and reliability of phase design.

[0092] The two-dimensional array structure in this embodiment has a simple manufacturing process. The rigid metal frame, internal partitions, rigid partitions, and rigid cover plates are all formed from aluminum alloy sheets through welding and splicing processes. The porous sound-absorbing material is embedded and filled, enabling industrial mass production. The structure has low overall density and light weight, facilitating engineering installation and maintenance. This array structure has a sound absorption coefficient α≥0.9 near the target frequency of 2000Hz, a sound absorption coefficient α≥0.8 within the predetermined frequency band of 1500Hz-3200Hz, and maintains a basically stable sound absorption coefficient within the incident angle range of -50° to +50°. It fully adapts to the engineering control requirements of multi-directional, broadband noise and can be directly applied to building walls, traffic noise barriers, industrial equipment noise reduction enclosures, and other scenarios.

[0093] Example 5

[0094] This embodiment demonstrates the multi-target frequency adaptation structure design of a double-sided phase gradient composite sound-absorbing metasurface. Based on the structural design constraints and structural scheme of this invention, the metasurface structure is differentiated for two different target operating frequencies of 1000Hz and 3000Hz, verifying the adaptability of this invention to noise of different frequencies.

[0095] The total thickness H of the metasurface is less than 1 / 8 of the acoustic wavelength λ corresponding to the target operating frequency, and the period length d satisfies λ / d>2. At the same time, the core structural form of the sub-unit "dual functional area" remains unchanged, and the structural geometric parameters are adjusted only according to the wavelength change of the target frequency. For the target frequency f0=1000Hz, the wavelength of sound waves in air λ≈0.34m, the total thickness of the metasurface is designed to be H=40mm (less than λ / 8=42.5mm), where the height of the first functional area is H1=25mm, the height of the second functional area is H2=15mm, and H1:H2=5:3; each cycle still has 4 sub-units, the length of the sub-unit along the first direction is 42mm, and the total length of the cycle is d=168mm, satisfying λ / d≈2.02>2; the thickness of the rigid partition in the first functional area is adjusted to 0.6mm, and the staggered spacing is 3mm; the length of the rigid partition in the second functional area is increased to 10mm; melamine foam is selected as the porous sound-absorbing material, and its equivalent acoustic parameters are calculated by the JCA model. The geometric parameters of the sound channel are adjusted so that the transmission and reflection phases of the 4 sub-units at 1000Hz are -π / 2, 0, π / 2, and π, respectively.

[0096] For the target frequency f0=3000Hz, the wavelength of sound waves in air λ≈0.113m, the total thickness of the metasurface is designed to be H=30mm (less than λ / 8=14.125mm). Among them, the height of the first functional area is H1=18mm, the height of the second functional area is H2=12mm, and H1:H2=3:2. The length of the sub-unit along the first direction is 14mm, and the total period length is d=56mm, which satisfies λ / d≈2.02>2. The thickness of the rigid partition in the first functional area is adjusted to 0.4mm, the spacing is adjusted to 1.5mm, and the length of the rigid partition in the second functional area is shortened to 6mm. The porous sound-absorbing material is selected as porous polyurethane foam to meet the sound energy dissipation requirements of the high-frequency band.

[0097] This embodiment is verified through numerical simulation, such as Figure 14 According to the frequency scattering pressure field law, the metasurface structures at 1000Hz and 3000Hz can both excite obvious surface waves at their respective target frequencies. The 1000Hz structure has a sound absorption coefficient ≥0.8 in the 700Hz-1500Hz frequency band, and the 3000Hz structure has a sound absorption coefficient ≥0.8 in the 2000Hz-4000Hz frequency band. Both structures maintain stable sound absorption performance within the incident angle range of -50° to +50°, which verifies that the core structural scheme and design method of this invention can flexibly adapt to the noise control requirements of different target operating frequencies.

[0098] Example 6

[0099] This embodiment demonstrates the multi-porous material adaptation verification of the dual-phase gradient composite sound-absorbing metasurface. The melamine foam in Example 1 is replaced with open-cell porous materials with rigid / semi-rigid skeletons such as porous polyurethane foam, glass wool, and mineral wool to complete the multi-material adaptation verification.

[0100] This embodiment maintains the core structural form, target operating frequency of 2000Hz, and geometric parameter reference of Embodiment 1, only replacing the porous sound-absorbing material, and finely adjusting the length and position of the rigid partitions in the first and second functional areas according to the equivalent acoustic characteristics of different materials, so that the metasurface structure can still achieve double-sided 0-2π phase coverage.

[0101] When porous polyurethane foam is selected, the material has a porosity of approximately 0.95 and a flow resistance of approximately 2.0 × 10⁻⁶. 4 Pa×s / m 2 The acoustic impedance is slightly higher than that of melamine foam. The length of the partition in the first functional area is increased by 2mm to enlarge the equivalent path of the transmitted sound channel. The height of the rigid partition in the second functional area from the substrate is increased by 3mm to ensure that the reflection phase matches the target value. When glass wool is used, its flow resistance is approximately 3.0 × 10⁻⁶. 4 Pa×s / m 2 The sound energy dissipation capability is stronger. The equivalent propagation path of the sound channel is appropriately reduced. The length of the partition in the first functional area is shortened by 3mm, and the length of the rigid partition in the second functional area is shortened by 2mm to avoid excessive phase delay. When mineral wool is selected, its equivalent acoustic characteristics are similar to those of glass wool. The partition spacing is finely adjusted to 2.2mm to match its viscous dissipation characteristics.

[0102] The equivalent acoustic parameters of all materials were solved using the JCA model and then imported into simulation software to verify the phase response and sound absorption performance. Figure 16 The sound absorption coefficient curves show that the metasurface structures adapted to different materials all have a sound absorption coefficient ≥0.9 at the target frequency of 2000Hz, and a sound absorption coefficient ≥0.8 in the frequency band of 1500Hz-3200Hz. Furthermore, they maintain stable performance within the incident angle range of -50° to +50°. This verifies that the present invention is compatible with various rigid / semi-rigid skeleton open porous materials, thus improving the engineering practicality of the invention.

[0103] Example 7

[0104] This embodiment implements a complete design method for a double-sided phase gradient composite sound-absorbing metasurface structure based on porous materials; taking the target operating frequency f0=1500Hz and low-frequency noise control in building acoustics as the application scenario, it fully realizes the entire process design from target setting to structural finalization.

[0105] Step S1:

[0106] The target frequency and structural constraints were determined. Based on the requirements for building acoustic noise control, the target operating frequency f0 = 1500 Hz and the target frequency band was determined to be 1200 Hz - 1800 Hz. The speed of sound in air is 340 m / s, and the wavelength of the sound wave corresponding to f0 is λ = 340 / 1500 ≈ 0.227 m. According to the design method constraints, the total thickness of the metasurface H = 35 mm (less than λ / 8 ≈ 0.0284 m), and the period length d satisfies λ / d > 2, that is, d < 0.1135 m. Finally, d = 80 mm was determined.

[0107] Step S2:

[0108] The metasurface period and the number of sub-units are determined; the number of sub-units in each period is N=4, and the phase difference between adjacent sub-units is approximately 2π / N=π / 2. The transmission and reflection phases of the four sub-units at 1500Hz are preset to be -π / 2, 0, π / 2 and π respectively, to achieve phase coverage of 0-2π on both sides of the metasurface; combined with the period length d=80mm, the length of a single sub-unit along the first direction is determined to be 20mm.

[0109] Step S3:

[0110] Dual-functional area construction; such as Figure 5 As shown, the initial structure of the sub-unit is constructed, and each sub-unit is divided into a first functional area (transmission phase modulation) and a second functional area (reflection phase modulation) along the thickness direction, with a total thickness H=35mm. The height of the first functional area is determined to be H1=22mm and the height of the second functional area is determined to be H2=13mm. The top and bottom of the first functional area are provided with rigid cover plates, and four adjustable rigid partitions (0.5mm thick) are provided on each of the left and right sides inside, which are staggered to form a tortuous sound channel that is not connected to each other. The second functional area is provided with a rigid partition near the right side wall, which together with the side wall defines the reflected sound channel. Both functional areas are filled with melamine foam as a porous sound-absorbing material.

[0111] Step S4:

[0112] Phase modulation based on equivalent acoustic parameters; the acoustic properties of melamine foam are described using the JCA equivalent medium model, with macroscopic parameters such as porosity, flow resistance, tortuosity, viscous characteristic length, and thermal characteristic length input, to calculate the equivalent density and equivalent bulk modulus in the 1500Hz frequency band; the equivalent parameters are then imported into COMSOL Multiphysics software, and... Figure 9 , Figure 10 The simulation settings are used to calculate the reflection phase, transmission phase, and sound absorption coefficient of each sub-unit under different combinations of structural parameters, and to obtain the equivalent impedance and equivalent wavenumber of the sub-unit.

[0113] Step S5:

[0114] Numerical simulation and parameter optimization: The phase response obtained in step S4 was compared with the target phase distribution set in step S2. It was found that the transmission phase deviation of some sub-units in the initial structure exceeded 5%. By adjusting the length of the rigid partition of the first functional area (maximum adjustment amount 3mm), the height of the rigid partition of the second functional area from the bottom (adjustment amount 2mm), and the filling range of the porous material, three rounds of iterative optimization were carried out on each sub-unit. Finally, double-sided 0-2π phase coverage was achieved at the target operating frequency of 1500Hz, and the sound absorption coefficient reached 0.92.

[0115] Step S6:

[0116] Periodic arrangement and overall performance verification: The four optimized sub-units are arranged periodically for 12 cycles along the first direction according to the predetermined phase gradient order, and arranged in 6 rows along the second direction to construct a complete two-dimensional sound-absorbing metasurface array; numerical simulation verifies that its sound absorption coefficient is ≥0.85 in the 1200Hz-1800Hz frequency band, and the sound absorption coefficient fluctuation is less than 8% in the incident angle range of -50° to +50°, meeting the preset performance indicators and completing the structural finalization.

[0117] In the description of this invention, it should be noted that the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0118] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0119] In the several embodiments provided by this invention, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. The apparatus embodiments described above are merely illustrative. For example, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. Furthermore, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Additionally, the coupling or direct coupling or communication connection shown or discussed may be through some communication interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0120] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0121] In addition, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0122] Finally, it should be noted that the above-described embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit it. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the technical scope disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

[0123] Furthermore, although the operations of the method of the present invention are described in a specific order in the accompanying drawings, this does not require or imply that these operations must be performed in that specific order, or that all the operations shown must be performed to achieve the desired result. Additionally or alternatively, certain steps may be omitted, multiple steps may be combined into one step, and / or one step may be broken down into multiple steps.

Claims

1. A double-sided phase gradient composite sound-absorbing metasurface structure based on porous materials, Its features are, include: A rigid metal frame that forms the outer contour and internal partitions of the metasurface structure; Multiple sound-absorbing metasurface sub-units are periodically arranged along a first direction and connected to the partition; Each of the sound-absorbing metasurface subunits is divided along the thickness direction into a first functional area and a second functional area that are acoustically isolated from each other by the partition. The first functional area is used to regulate the phase of the transmitted sound wave, and it is equipped with a sound channel defined by a rigid partition and a porous sound-absorbing material. The second functional area is used to adjust the phase of the reflected sound wave, and it is equipped with a sound channel defined by a rigid partition and a porous sound-absorbing material. In the first direction, the geometric parameters of the first functional area and / or the second functional area and / or the equivalent acoustic parameters of the porous material filled in the different sub-units are different, so that each sub-unit generates different transmission phase and reflection phase on the transmission side and reflection side of the metasurface at the target operating frequency. Furthermore, within each cycle, the phase response of each sub-unit on the same side constitutes a discrete phase distribution covering 0 to 2π, thereby forming a predetermined phase gradient on both sides of the metasurface.

2. The double-sided phase gradient composite sound-absorbing metasurface structure based on porous materials according to claim 1, Its features are, The first functional area is located in the upper part of the rigid metal frame, with rigid cover plates at its top and bottom. Inside, multiple rigid partitions of adjustable length are arranged in an alternating or symmetrical manner to form multiple non-interconnected tortuous sound channels. The second functional area is located in the lower part of the rigid metal frame, with at least one rigid partition of adjustable length and position near one side wall, which together with the side wall defines the reflected sound channel.

3. The double-sided phase gradient composite sound-absorbing metasurface structure based on porous materials according to claim 1, Its features are, N sound-absorbing metasurface sub-units are set within one cycle, where N≥4, so that the reflection phase and / or transmission phase difference between adjacent sub-units at the target operating frequency is 2π / N, thereby achieving phase coverage from 0 to 2π within one cycle.

4. The double-sided phase gradient composite sound-absorbing metasurface structure based on porous materials according to claim 3, Its features are, The period length d of the sound-absorbing metasurface subunit along the first direction satisfies λ / d>2 with the acoustic wavelength λ corresponding to the target operating frequency, so that the higher-order diffraction wave is converted into a surface wave propagating along the interface.

5. The double-sided phase gradient composite sound-absorbing metasurface structure based on porous materials according to claim 1, Its features are, The total thickness H of the metasurface structure is less than 1 / 8 of the acoustic wavelength λ corresponding to the target operating frequency. The total thickness H is the sum of the height H1 of the first functional area and the height H2 of the second functional area.

6. The double-sided phase gradient composite sound-absorbing metasurface structure based on porous materials according to claim 1, Its features are, The rigid metal frame and its internal rigid partitions are made of at least one of aluminum alloy, steel or engineering plastic; the porous sound-absorbing material is at least one of melamine foam, porous polyurethane foam, glass wool or mineral wool.

7. A double-sided phase gradient composite sound-absorbing metasurface structure based on porous materials according to claim 2, Its features are, In the first functional area, the equivalent propagation path of the sound channel is adjusted by changing the length and / or position of each rigid partition, thereby achieving fine control of the phase of the transmitted sound wave; in the second functional area, the length of the reflected sound path is adjusted by changing the length of the rigid partition and / or its height from the bottom, thereby achieving control of the phase of the reflected sound wave.

8. The double-sided phase gradient composite sound-absorbing metasurface structure based on porous materials according to claim 1, Its features are, The periodic structure is arranged repeatedly for at least 10 cycles along the first direction and arranged in several rows in a second direction perpendicular to the first direction to form a two-dimensional sound-absorbing metasurface array; the metasurface structure has a sound absorption coefficient α ≥ 0.8 in a predetermined frequency band including the target operating frequency, and the sound absorption coefficient remains stable in the incident angle range of -50° to +50°.

9. A double-sided phase gradient composite sound-absorbing metasurface structure based on porous materials according to claim 3. Its features are, With N=4, the reflection phase and transmission phase of each sub-unit at the target operating frequency are -π / 2, 0, π / 2 and π, respectively.

10. A design method for a double-sided phase gradient composite sound-absorbing metasurface structure based on porous materials. The double-sided phase gradient composite sound-absorbing metasurface structure based on porous materials as described in any one of claims 1 to 9 is employed. Its features are, Includes the following steps: S1: Based on the target noise control requirements, determine the target operating frequency f0 of the metasurface, and set the total thickness H and period length d of the metasurface according to the corresponding acoustic wavelength λ. S2: Determine the number N of sound-absorbing metasurface sub-units in each cycle, and preset the reflection phase and transmission phase of each sub-unit at the target operating frequency f0, so that the phase difference between adjacent sub-units is 2π / N; S3: Construct the initial structure of the sub-unit for achieving dual-sided phase modulation, and divide each sub-unit into a first functional region for transmission phase modulation and a second functional region for reflection phase modulation along the thickness direction; S4: Based on the equivalent medium model or numerical simulation method of porous materials, calculate the reflection phase, transmission phase and sound absorption coefficient of each sub-unit under different combinations of structural parameters. S5: Compare the phase response obtained in step S4 with the target phase set in step S2. By adjusting the geometric dimensions of the rigid partition and the filling area of ​​the porous material, iteratively optimize each sub-unit until double-sided 0 to 2π phase coverage is achieved at the target operating frequency f0. S6: Multiple optimized sub-units are periodically arranged in a predetermined phase gradient order to construct a complete double-sided phase gradient composite sound-absorbing metasurface structure.

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