36 results about "Absorption frequency" patented technology

The invention belongs to the technical field of low-frequency sound absorption, and discloses a micro-perforated plate composite gradient spiral pipe sound absorption device and method.The micro-perforated plate composite gradient spiral pipe sound absorption device comprises a variable cross-section spiral pipe, and the diameter of the inlet end of the variable cross-section spiral pipe is larger than that of the outlet end of the variable cross-section spiral pipe; a plurality of MPP plates are mounted in the variable-cross-section spiral pipe, one MPP plate is embedded into the inlet end of the variable-cross-section spiral pipe, and the other MPP plates are sequentially embedded into the variable-cross-section spiral pipe at equal intervals, so that a multi-stage MPP plate composite sound absorption structure is formed; and the cross-section pipe diameter of the variable cross-section spiral pipe is linearly reduced from the inlet end of the variable cross-section spiral pipe to the outlet end of the variable cross-section spiral pipe. Through the gradient design of the variable cross-section spiral tube integrated micro-perforated plate, low-frequency broadband efficient sound absorption is realized in a compact space, the problem of heavy structure caused by dependence on a deep and large back cavity in the traditional technology is avoided, the limitation of narrow sound absorption frequency band is overcome, and the sound absorption device is particularly suitable for being applied to occasions with limited spaces and has wide application prospects. And low-frequency performance and broadband characteristics are considered in a limited space.

The invention discloses a preparation method of a beaded cobalt-doped Bi25FeO40 / BiFeO3 nanofiber wave-absorbing material, which comprises the following steps: obtaining a precursor by a standing method, and adding the precursor, bismuth nitrate, ferric nitrate and a spinning aid into a mixed solvent compounded by N, N-dimethylformamide and absolute ethyl alcohol to obtain a spinning solution; spinning the spinning solution by adopting an electrostatic spinning technology to obtain a nanofiber membrane; and finally, drying and calcining to obtain the wave-absorbing material. According to the wave-absorbing material, multiple reflection and scattering of electromagnetic waves are increased, the absorption performance of the electromagnetic waves is improved, due to the fact that a heterogeneous interface is generated after two phases are compounded, the interface polarization loss is further increased, when the thickness of the wave-absorbing material is 2.33 mm, the minimum reflection loss reaches-56.01 dB, the effective absorption frequency band width is 6.32 GHz, and the whole Ku wave band is covered.

The invention relates to a sound absorption-vibration reduction integrated structure which comprises sound absorption-vibration reduction composite units, the multiple sound absorption-vibration reduction composite units are arranged on a two-dimensional plane in a periodic array mode, and each sound absorption-vibration reduction composite unit comprises a micro-lattice lattice structure, a rigid vibrator, a rubber layer and a base plate which are sequentially stacked and fixedly connected with one another from top to bottom. A sound absorption structure and a vibration reduction structure are integrated in a three-dimensional space, structural light weight and design simplification are achieved, broadband cooperative control over noise and vibration is also achieved, and a wider control frequency band can be covered; low-frequency vibration control can be achieved through a compact structure far smaller than the wavelength, the size limitation of a traditional vibration isolation material is broken through, the high designability is achieved, the sound absorption frequency spectrum can be optimized by adjusting the unit cell rod diameter and size of the micro-lattice, and by changing the mass of the vibrator and the material and size of the rubber layer, the low-frequency vibration can be achieved. The band gap frequency position can be accurately designed, and different application requirements are met.

The invention relates to the field of terahertz metamaterial devices, and provides a reconfigurable broadband / multi-frequency terahertz wave absorber based on vanadium dioxide. The wave absorber is composed of metamaterial square units which are arranged periodically, and adjacent units are gapless. Each unit is composed of six layers of structures including a vanadium dioxide resonance layer, an upper polyimide dielectric layer, a vanadium dioxide thin film layer, a copper resonance layer, a lower polyimide dielectric layer and a copper substrate layer. Vanadium dioxide can realize reversible phase change between a metal state and an insulation state through external excitation. In a metal state, the wave absorber has an ultra-wideband terahertz wave absorption function; and in an insulated state, a double-narrow-band absorption function is shown. According to the invention, the reconstruction of the absorption frequency and the bandwidth of the terahertz wave absorber is effectively realized, the problems of complex structure and fixed function of a traditional terahertz sensor are solved, and the potential of the terahertz wave absorber in sensing application of a single narrow-band wave absorber is further discussed.

This invention discloses a porous Helmholtz resonator with adaptively adjustable sound absorption frequency band, belonging to the fields of noise control and virtual reality technology. It comprises a sound-absorbing structure consisting of a rotating perforated panel, a fixed perforated panel, and a perforated porous material plate arranged sequentially from top to bottom, as well as an adaptive adjustment system composed of a sound pressure sensor, a controller, and a motor. The motor drives the rotating perforated panel to rotate via gear transmission, changing the perforation overlap area; the perforated porous material plate compensates for acoustic impedance, maintaining sound absorption performance. The controller pre-stores spectral data at different rotation angles and selects the optimal rotation angle by comparing the real-time noise spectrum with the pre-stored data. This invention achieves adaptive adjustment of the sound absorption frequency band, maintains a high sound absorption peak value over a wide parameter range, is suitable for large-area deployment, has a compact structure, and low cost, and can be used for noise control and auditory virtual scenes.

The invention discloses a wave-absorbing structure and a wave-absorbing plate, the wave-absorbing structure comprises a skin layer, an impedance layer, a dielectric layer and a substrate layer which are stacked in sequence, the upper surface of the skin layer is an incident plane of electromagnetic waves, the impedance layer comprises a first conductive layer and a plurality of second conductive layers, the first conductive layer is square, and the second conductive layer is square. The plurality of second conductive layers are arranged around the outer side of the first conductive layer, and the second conductive layers are square rings with openings. The wave absorbing plate comprises M * N wave absorbing structures. Through reasonable design of a multi-layer composite structure, after electromagnetic waves are incident from the skin layer, multiple interference occurs between the impedance layer and the dielectric layer, and through the synergistic effect of absorption and reflection of the impedance layer and the substrate layer, efficient dissipation of electromagnetic energy is achieved, and the high-performance electromagnetic absorption effect is achieved. Besides, due to the design form of the open square ring of the second conductive layer, the impedance layer has an impedance compensation effect, the wave-absorbing bandwidth is effectively expanded, and particularly, a relatively wide effective absorption frequency band can still be kept in an oblique incidence state of electromagnetic waves.

This invention discloses a reconfigurable absorbing metasurface based on heterogeneous absorbing units using a tenon-and-mortise interlocking structure, and its configuration method, belonging to the field of electromagnetic wave absorption and metasurface structure technology. The metasurface is formed by assembling multiple lightweight absorbing units through a tenon-and-mortise interlocking structure. The absorbing units use melamine foam, PMI foam, polyurethane foam, or aerogel porous framework materials as the matrix, and are loaded with absorbing components such as graphene, carbon nanotubes, MXene, ferrite particles, carbonyl iron particles, or conductive polymers. The tenon-and-mortise connection structure has multiple levels of insertion positions and limiting structures, allowing adjacent units to form different insertion states, thereby adjusting the unit spacing, air layer thickness, array period, and equivalent electromagnetic parameters, achieving reconfigurable control of the absorption frequency band and response characteristics. Furthermore, heterogeneous absorbing units with different geometries and absorption parameters can be optimized through parametric design and electromagnetic simulation to form planar or curved broadband absorbing structures. This invention combines the advantages of lightweight, modularity, detachability, surface adaptability, and wideband absorption, and can be applied to fields such as electromagnetic stealth, radar absorption, electromagnetic protection, and complex curved electronic equipment.

This invention relates to the field of noise control and acoustic metamaterials technology, and discloses a device and method for synergistically regulating the sound absorption frequency by adjusting the neck length and cavity volume. The sound-absorbing device includes a Helmholtz main structure and an adjustable neck assembly. The main structure includes a perforated top plate, hexagonal honeycomb sidewalls, rubber lining, and a central base plate, which is connected to a drive device via a push rod. The adjustable neck assembly employs a three-layer nested sleeve design, utilizing a spring return mechanism and a sliding hook slot mechanism to achieve graded adjustment of the neck length. The drive device drives the push rod to raise and lower the central base plate, providing thrust to the adjustable neck assembly and simultaneously changing the cavity volume. This metastructure overcomes the limitations of traditional underwater Helmholtz sound-absorbing structures, which suffer from fixed frequency bands and poor adaptability. By synergistically regulating the sound absorption frequency band with dual parameters, it dynamically responds to changes in the complex underwater acoustic environment, significantly reducing the acoustic target intensity of underwater equipment and providing an efficient solution for acoustic stealth in deep-sea equipment.

The application discloses a kind of easily engineering realized metamaterial absorption structure, belong to microwave metamaterial technical field.The metamaterial absorption structure of the application includes: from bottom to top layer stack arrangement metal backplate, intermediate dielectric layer and upper layer resonance layer;Upper layer resonance layer is composed of periodically arranged resonance unit, and the resonance unit is composed of four square slit metal radiation patches connected by lumped capacitance element;Metal backplate is connected with upper layer metal radiation patch by circular metal through-hole, wherein four square slit metal radiation patches are rotationally symmetric and divided into four corners of unit;The slit direction of square slit metal radiation patch is parallel to its side length, and two metal slits in each square slit metal radiation patch are perpendicular to each other, and the right angle formed by two metal slits points to the center of wave-absorbing structure unit.The application obtains multiple perfect absorption frequency points by adjusting the position and length of metal slit, and the wave-absorbing efficiency reaches 99%.

The invention provides a broadband metasurface wave absorber based on an oblique symmetric mosaic structure. The broadband metasurface wave absorber comprises a metal resonance layer, a dielectric layer and a metal reflecting layer which are sequentially stacked, the metal reflecting layer is formed by two inlaid structures which are arranged in an oblique symmetry mode, each inlaid structure comprises a semi-square ring body and a semi-circular ring body wrapping the outer side of the semi-square ring body, and two edge protruding edges of each semi-square ring body are connected with the corresponding semi-circular ring body; the semi-square ring body and the semi-circular ring body are both of an open structure, and the opening directions of the semi-square ring body and the semi-circular ring body are the same. According to the wave absorber disclosed by the invention, a broadband absorption effect on electromagnetic waves in a frequency band of 9.43 GHz to 14.95 GHz is realized; meanwhile, within the absorption frequency band, the absorption rate of electromagnetic waves reaches 90% or above, and the absorption rate of electromagnetic waves reaches 99% or above near two resonance peak values of 10.02 GHz and 13.56 GHz.

The application relates to the technical field of wave-absorbing materials, in particular to a wide-band calcium ferrite wave-absorbing material and a preparation method and application thereof. 1.8 La 0.2‑x Ce x Fe2O5, wherein 0<=x<0.14. The application solves the problems of narrow absorption frequency band and low efficiency of the oxide wave-absorbing material by adjusting the composition and dielectric properties of the material through La and Ce double-element co-doping, and the prepared material has the advantages of wide absorption frequency band and high absorption intensity.

The invention discloses a broadband low-frequency sound absorption structure with sub-wavelength thickness, and relates to the technical field of noise control, the broadband low-frequency sound absorption structure with sub-wavelength thickness comprises a box body and fractal members arranged in the box body in a rectangular array mode, and the four adjacent fractal members arranged in the rectangular array mode are combined to form a first cavity; a plurality of fractal components close to the inner side surface of the box body are combined with the inner side surface of the box body to form a second cavity; the fractal component comprises a first plate body and a second plate body, the first plate body is provided with a third cavity, and the second plate body is provided with a fourth cavity; a cover plate is arranged on the top face of the box body, and a plurality of through holes communicated with the first cavity, the second cavity, the third cavity and the fourth cavity respectively are formed in the cover plate. According to the broadband low-frequency sound absorption structure with the sub-wavelength thickness, the technical problems that an existing composite sound absorption structure can only meet the sound wave resonance requirement of a limited frequency band, the sound absorption frequency band range is narrow, and sub-wavelength magnitude light and thin design cannot be achieved are solved.

The invention relates to the technical field of terahertz metamaterials, and provides a graphene-VO2 composite film tunable terahertz wave absorber. The wave absorber sequentially comprises a VO2 resonance layer, a graphene patch layer, a dielectric layer and a metal grounding layer from top to bottom, and the overall thickness of the wave absorber is 1t. And the structure is compact. The graphene Fermi level and the VO2 phase state are independently regulated and controlled through external bias voltage, and instantaneous switching of absorption frequency spectrums is achieved: when the graphene Fermi level is 0 eV and VO2 is in a metal state, the absorptivity of the device within the frequency band of 1.92-7.22 THz is larger than or equal to 90%, and the relative bandwidth is 115%; when the Fermi level of graphene is increased to 0.9 eV and VO2 is converted into an insulated state, the absorptivity of the device within the frequency band of 5.13-6.58 THz is larger than or equal to 90%. And meanwhile, the absorber has excellent polarization insensitivity and wide-angle incidence characteristics. The invention has the advantages of ultrafast speed, reconfigurability, low power consumption and flexible substrate compatibility, can be widely applied to terahertz imaging, intelligent stealth and adjustable filter devices, and provides a new generation of core function unit for a terahertz system.

The invention provides a built-in microwell plate sound absorption cavity structure which comprises a plurality of silencing units, every two of the silencing units are in contact with each other to form a three-dimensional novel built-in microwell plate sound absorption cavity structure, each silencing unit comprises a shell, through holes are formed in the shells, and the through holes are communicated with the silencing units. The micro noise elimination unit is adopted, a micro-pore plate resonance structure is arranged in the noise elimination unit, the sound absorption and noise reduction efficiency of the noise elimination unit is greatly improved, the novel sound absorption cavity structure provided with the micro-pore plate is small in size, the noise reduction effect is good, the noise reduction effect is good, and the noise reduction effect is good. The correspondingly combined novel built-in microwell plate sound absorption cavity structure is small in size, has the 1 / 23-time sub-wavelength sound absorption characteristic, has the ultra-thin characteristic, is wide in sound absorption frequency band and good in noise reduction effect, and can be suitable for sound absorption and noise reduction of various small places and spaces.

The application discloses a preparation method of a frequency band magnetic control adjustable aerogel-based wave-absorbing material. First, ferromagnetic iron-cobalt nanosheets are obtained through a liquid phase reduction method, and then the nanosheets are ultrasonically mixed and dispersed with graphene oxide. The mixed system is subjected to a hydrothermal reaction to obtain a composite hydrogel precursor. After freeze-drying, a graphene aerogel-based composite wave-absorbing structure is obtained, wherein the ferromagnetic nanosheets exist in the hollow skeleton structure of the aerogel. The precursor aerogel structure is quickly immersed in a sodium alginate solution, and a hydrogel medium is formed in the structure by adding calcium ions, so that the nanosheets are suspended in the hollow skeleton of the aerogel, and an adjustable composite wave-absorbing material is obtained. By applying an external magnetic field at different angles, the nanosheets are oriented in the hollow skeleton. By changing the angle between the interface dielectric dipole array and the easy magnetization magnetic moment and the electromagnetic wave vector, respectively, the microwave electromagnetic parameters and the impedance of the material are dynamically adjusted, so that the real-time dynamic adjustment of the wave-absorbing performance and the absorption frequency band is realized.

The invention relates to the technical field of electromagnetic wave absorption, and discloses a stacked annular water-based metamaterial absorbing material with a scattering characteristic and a process thereof, the material is composed of periodically arranged unit structures, each unit structure comprises a metal substrate, a structure support body arranged on the metal substrate and a liquid absorbing medium filled in the metal substrate, the structure supporting body is integrally formed by a photosensitive resin material, and a three-dimensional water cavity structure formed by vertically stacking or combining various geometrical shapes such as a cross shape, a cylinder shape, a ring shape or an open ring shape is formed in the structure supporting body. According to the structural design, multiple resonance modes can be excited under electromagnetic wave incidence, a wide absorption frequency band is formed through coupling and superposition of the multiple resonance modes, the invention further discloses a preparation process of the structure, the structure supporting body is manufactured through the 3D printing technology, and then liquid filling and overall assembling are conducted. The problem that the bandwidth of an existing absorbing material is limited is solved, the preparation process is simple, and the cost is low.

The invention discloses an acoustic filter, and belongs to the technical field of filters. The acoustic filter comprises a first transmission port (port1), a second transmission port (port2) and a third transmission port (port3), wherein the port3 is connected to an absorption load (6) at the same time; the band-pass filter is connected between the first transmission port and the second transmission port and is used for transmitting the signal of the working frequency band PB1 received by the first transmission port to the second transmission port and inhibiting the signal of the non-working frequency band RB received by the first transmission port; the notch filter is connected between the first transmission port and the third transmission port and is used for transmitting a signal of an absorption frequency band RB1 (RB comprises an RB1 frequency band) received by the first transmission port to the third transmission port and suppressing a signal of a working frequency band PB1 received by the first transmission port in a notch manner; and an intermodulation PIM signal generated by the absorption frequency band RB1 falls into the working frequency band PB1. Nonlinearity of the acoustic filter can be reduced, and intermodulation performance can be improved.

According to the method for widening the sound absorption frequency band of the micro-perforated plate sound absorber array under the excitation of the free field oblique incidence plane wave, the coupling sound absorption rule between units in the array is analyzed and fully utilized according to the excitation condition of the free field oblique incidence plane wave; unit structure parameters in the array are subjected to optimization design, the optimal sound absorption performance is achieved, the effective sound absorption frequency band of the MPPA array is greatly widened, and broadband efficient sound absorption of the MPPA array under free field oblique incidence excitation is achieved. The invested cost is low, the sound absorption frequency band broadening effect of the MPPA array is obvious, and therefore the MPPA array has important engineering application value.

Embodiments can include, for example: a conductor-backed dielectric; and circuitry connected in parallel with the conductor-backed dielectric, wherein the circuitry connected in parallel with the conductor‑backed substrate exhibits an admittance with an imaginary component having a negative slope within a design absorption frequency range of the absorber structure.

The invention provides a sound absorption unit and structure based on micro crack and spiral coupling and a preparation method of the sound absorption unit and structure, and belongs to the technical field of acoustic metamaterials. The sound absorption unit comprises a housing with a rectangular inner cavity, the incidence side of the housing is provided with a micro-slit incidence channel communicated with the rectangular inner cavity, the rectangular inner cavity is internally provided with a spiral curly channel with the outer side end communicated with the micro-slit incidence channel, and the spiral curly channel is formed by a partition plate and the two opposite side walls of the rectangular inner cavity in a sealed surrounding mode. The partition plate is in the shape of a spiral curve on a section plane perpendicular to the incidence direction of the spiral curled channel and extends in the incidence direction. Broadband efficient sound absorption can be achieved, and the technical problem that in the prior art, a traditional sound absorption metamaterial is narrow in sound absorption frequency band is effectively solved.

The application provides a frequency stabilizing device based on combination of an F-P cavity and a reference cell, wherein atomic and molecular gas is filled in a traditional F-P cavity, a feedback signal is applied to the F-P cavity length by using a saturated absorption frequency stabilizing technology, the cavity length is locked on an atomic and molecular energy level transition frequency, disturbance of the cavity length caused by the environment is overcome, and the F-P cavity with the locked cavity length is applied to PDH frequency stabilization of a laser. The device has compact structure, can consider short-term frequency stability of the PDH frequency stabilization and long-term frequency stability of the saturated absorption frequency stabilization, and improves environmental adaptability of the frequency stabilized laser.

This application provides a pulsed frequency-stabilized vortex laser, which constructs a highly stable frequency locking system through a carefully designed continuous light amplification, frequency doubling, and potassium atom saturated absorption frequency stabilization stage. This system can quickly and accurately detect and correct minute drifts in laser frequency, effectively suppressing frequency drift. Compared with traditional vortex lasers, the frequency stability of this invention is improved by more than an order of magnitude.

According to the preparation method of the reversible electromagnetic function conversion material and the application of the obtained product, the impedance and thickness of hydrogel can be effectively adjusted by changing the water content, and the defects that electromagnetic shielding and microwave absorption cannot be converted, and the electromagnetic wave absorption frequency is fixed and single are overcome. The reversible dynamic adjustment electromagnetic performance conversion can be converted from the electromagnetic shielding performance to the microwave absorption performance and can also be converted from the microwave absorption performance to the electromagnetic shielding performance, and the reversible conversion process can be reversibly and dynamically adjusted along with the microwave absorption frequency band. The reversible electromagnetic function conversion material integrates reversible conversion of electromagnetic performance and dynamic adjustment of microwave absorption frequency band, opens up a new way for development of next-generation intelligent convertible electromagnetic equipment crossing different fields, and provides a theoretical basis.

A multi-gradient micro-perforated plate low-frequency broadband sound absorption structure based on a sound wave black hole effect belongs to the field of low-frequency vibration and noise reduction, is integrally cylindrical and consists of N micro-perforated plates, N connecting plate sleeves and a base, the micro-perforated plates and the connecting plate sleeves are sequentially arranged from top to bottom, the micro-perforated plate is arranged on the topmost layer, the micro-perforated plates are connected through the connecting plate sleeves, and the micro-perforated plate on the lowermost layer is connected with the base through the connecting plate sleeve. The aperture, the perforation rate and the plate distance of the designed micro-perforated plate are gradually changed layer by layer from top to bottom, a multi-gradient structure is formed, the sound wave black hole effect is introduced, the sound wave propagation speed is gradually reduced, the path is prolonged, and step-by-step gathering and dissipation of sound energy are achieved in combination with viscous damping and resonance effects; the base is used for preventing sound energy leakage and enhancing low-frequency absorption; the invention has the advantages of wide sound absorption frequency band, excellent low and medium frequency absorption performance, compact structure, controllable parameters, easy processing and modular combination, and is suitable for the engineering fields of noise control, architectural acoustics and the like.

The application discloses an aero-engine three-dimensional outer channel sound attenuation parameter generation method, comprising the following steps: constructing a three-dimensional fan post-transmission noise physical simplified calculation model according to a frequency domain convection wave control equation; and obtaining an optimal solution of the model with high precision based on a high-order space discretization and time advancing algorithm to obtain parameters corresponding to aero-engine three-dimensional outer channel sound attenuation. The application solves the problem that a traditional two-dimensional sound attenuation design method can only reduce noise at a specific frequency under one working condition or at most two working conditions, has no inhibitory effect on noise under other working conditions, solves the defect of a narrow sound absorption frequency band of the traditional two-dimensional sound attenuation design method, proposes a three-dimensional fan post-transmission noise calculation method, a gradient guide, a multi-island genetic algorithm and a secondary optimization combination technology with consideration of precision and efficiency, and develops a three-dimensional multi-section outer channel sound attenuation design method, which can inhibit noise at three noise airworthiness examination points of approach, sideline and flyover, significantly expands a sound absorption frequency band, and has a broadband sound attenuation effect.

The invention relates to the technical field of electromagnetic shielding, and provides a variable-frequency-ratio metasurface absorber which is characterized in that a first metal sheet and a second metal sheet are arranged on the upper surface and the lower surface of a substrate respectively, the second metal sheet is grounded, and the first metal sheet receives electromagnetic waves and is connected with an absorption circuit so as to selectively absorb target electromagnetic waves through the absorption circuit; the first metal sheet is provided with a fishbone-shaped groove, the fishbone-shaped groove comprises a first main groove, a second main groove and a plurality of secondary grooves, and the first metal sheet is symmetrical in the transverse direction and the longitudinal direction; the second main grooves are arranged on two sides of the first main groove and are separated from the first main groove through the connecting branches. The first main groove and the secondary groove are isolated through the second main groove and the connecting branch knot, resonance interference between the first main groove and the secondary groove is reduced, and therefore when the corresponding target absorption frequency is adjusted by adjusting the length of the secondary groove, interference on the absorption frequency corresponding to the first main groove can be reduced, and the absorption efficiency of the device is improved. And the design cost of absorption frequency adjustment is reduced.

The invention provides a double-layer broadband metamaterial wave absorber covering a C-X-Ku wave band. The double-layer broadband metamaterial wave absorber comprises a copper substrate layer, a first filling layer, a first dielectric layer, a first copper resonance layer, a second filling layer, a second dielectric layer and a second copper resonance layer which are sequentially stacked from bottom to top. The first copper resonance layer comprises a copper square resonance ring, and four edges of the first copper resonance layer are respectively provided with two gaps with fixed intervals. A resistor element is loaded at each gap, and eight resistors are periodically and symmetrically distributed along the ring arms. And the second copper resonance layer comprises four copper right-angle resonance units which are arranged in a central symmetry manner. The two orthogonal arms of each unit are respectively provided with a notch, resistors are loaded at the notches, and the eight resistors are symmetrically distributed on the copper right-angle resonance layer. The invention has the characteristics of high absorption efficiency, wide absorption frequency band and low profile; the method has wide application prospects in the fields of electromagnetic modulation, electromagnetic stealth and the like, and is extremely high in practicability.

The invention discloses an optimization and application method of a microporous acoustic board, and relates to the field of structural design of microporous acoustic boards. The aperture and pitch of the micropores in the microporous membrane in the microporous acoustic board and the depth of the cavity reserved after the perforated substrate is installed can be effectively optimized and adjusted, so that the sound absorption performance and sound absorption effect of a specific frequency band are effectively ensured in a specific scene. The method comprises the steps of 1, establishing a sound absorption coefficient calculation model; step 2, giving initial preset values of the pore diameter and the pore pitch of the micropores; step 3, optimizing the depth of the cavity; step 4, optimizing the pore diameter of the micropores; and step 5, optimizing the hole pitch. According to the optimization method provided by the invention, specific size parameter and installation parameter adjustment can be carried out on the to-be-processed and to-be-installed micropore acoustic board according to a specific target silencing frequency band, so that the micropore acoustic board can be effectively adapted and coped with different sound absorption requirements of feature scenes.

The application discloses a three-dimensional water-based frequency selective absorber with switchable electromagnetic properties, comprising a plurality of symmetrically designed three-dimensional gradient structure medium square waveguide frequency selective surface unit structures and periodic water-based metamaterial absorber units; the three-dimensional gradient structure medium square waveguide frequency selective surface unit structure has wideband transmission performance with high frequency selectivity; the periodic water-based metamaterial absorber unit is encapsulated around the frequency selective surface unit structure and has super wideband absorption performance; three transmission poles and two transmission zeros are generated in the three-dimensional gradient structure medium square waveguide frequency selective surface unit structure through cascading three metal square rings in an up-down mode, so that a high-frequency-selectivity wideband three-dimensional frequency selective surface is realized; the transmission out-of-band absorption and the conversion of reflection electromagnetic characteristics are realized by controlling the on-off of water in the periodic water-based metamaterial absorber unit. The application expands the transmission bandwidth, has wide absorption frequency band and high absorption rate, and can realize dual polarization.

The application discloses a center transmission and two-side absorption frequency selective wave-absorbing body, which comprises m*n periodic arranged wave-absorbing body units, m>=6, n>=6; each wave-absorbing body unit comprises a first metal layer, a first dielectric layer, an intermediate air layer, a second dielectric layer and a second metal layer from top to bottom; the first metal layer is composed of loaded Jerusalem cross with lumped resistance and simple parallel LC resonator composed of metal microstrip; the simple parallel LC resonator is embedded between the terminal microstrip of every two adjacent Jerusalem crosses; the lumped resistance is loaded at the middle position of the four arms of the Jerusalem cross; the second metal layer is periodically arranged by square ring aperture units; the materials and sizes of the first dielectric layer and the second dielectric layer are the same. The application has the advantages of simple structure, easy processing, low cost, small in-band insertion loss and the like, and simultaneously has a wide absorption band and good angle and polarization stability.