96 results about "Micro perforated plate" patented technology

The invention relates to the technical field of noise control, and discloses a combined noise reduction and sound absorption unit and a sound absorption board, sound absorption unit structures are periodically arranged and combined to form the sound absorption board with a large area, the sound absorption board is installed on an indoor wall or ceiling of a gas power plant, and indoor low-frequency broadband sound absorption and noise reduction are achieved. The sound absorption device comprises a first sound absorption assembly, the first sound absorption assembly comprises a first shell and a first micro-perforated plate arranged on the first shell, and the first micro-perforated plate is arranged on the first shell; the second sound absorption assembly comprises a second shell, a second micro-perforated plate arranged above the second shell and a second Helmholtz resonant cavity arranged below the first shell; the third sound absorption assembly comprises a third shell, a third micro-perforated plate arranged above the second shell and a plurality of third Helmholtz resonant cavities arranged below the first shell; the first sound absorption assembly, the second sound absorption assembly and the third sound absorption assembly are distributed in parallel.

The invention discloses a multi-dimensional stealth submarine bionic heterogeneous protective shell and a preparation method thereof, and relates to the technical field of ship and ocean engineering. The submarine bionic heterogeneous protective shell is composed of a sandwich structure and a modified carbon nanotube film; the sandwich structure comprises a bionic Priative multi-stage rotating core layer, a bionic Diamond multi-stage rotating core layer, a bionic octagonal body spiral core layer, a bionic rhombic dodecahedron spiral core layer, a micro-perforated plate and a sound absorption lower plate. According to the design, the Bouligand structure and the acoustic structure principle of the giant bone tongue fish scale are fused, the unique configuration of inter-layer rotation and spiral rising in the microstructure of the giant bone tongue fish scale is used for reference, four bionic structures are innovatively constructed, deformation is effectively restrained, the stability of the overall structure is improved, and through force-sound coupling regulation and control, the mechanical property of the giant bone tongue fish scale is greatly improved. And an innovative solution is provided for achieving the mechanical bearing and sound stealth integrated function of the submarine shell.

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 relates to the technical field of noise treatment, and discloses a composite sound absorption and insulation device which comprises a cavity, a Fabry-Perot resonance structure, gradient structure sound absorption felt, two-dimensional dot matrix scatterer sound insulation rubber and a cover plate. An opening is formed in one side of the cavity, and the two-dimensional dot matrix scatterer sound insulation rubber, the gradient structure sound absorption felt, the Fabry-Perot resonance structure and the cover plate are sequentially arranged at the bottom of the cavity in the direction towards the opening. Wherein an opening is formed in the middle of the top of the cover plate; the Fabry-Perot resonance structure comprises a micro-perforated plate and a space coiling channel, and the micro-perforated plate is arranged right above an opening of the space coiling channel and penetrates through the cover plate to be matched with the opening of the cover plate, so that the cover plate covers the rest part of the space coiling channel; through the combination of a plurality of advanced sound absorption and insulation structures, the low-frequency noise of 100Hz and frequency multiplication of the transformer substation is effectively treated.

The invention discloses a low-frequency light and thin sound insulation structure, a thickness calculation method and application, the low-frequency light and thin sound insulation structure comprises a bottom plate, a partition plate, a perforated plate and a porous material which are sequentially arranged from bottom to top, the partition plate is of a concentric-square-shaped structure, and the porous material is located in a mounting cavity defined by the bottom plate, the partition plate and the perforated plate; the bottom plate, the partition plate, the perforated plate and the porous material are combined together to achieve low-frequency sound insulation. The sound insulation characteristics of thin plate resonance, the porous material and the micro-perforated plate + cavity are effectively combined together, according to the environment sound insulation requirement, double-side low-frequency sound insulation is achieved, the sound insulation performance of the thin plate side is better than that of the perforated plate side, the sound insulation amount is higher than 30 dB, and the low-frequency sound insulation performance is excellent.

The invention discloses a design method of an array type silencer adaptive to a main ventilation air path between a stator iron core of a hydraulic generator and an air cooler and the array type silencer, and relates to the technical field of suppression or reduction of noise of the hydraulic generator. The method comprises the steps of S1, obtaining aerodynamic noise data and airflow parameters of a main ventilation air path, S2, determining a silencing thought and a micro-perforated plate array core structure according to broadband vortex, discrete rotation, vortex falling and surge noise, S3, determining the boundary dimension and preliminarily calculating the airflow parameters, S4, designing plate parameters in combination with a micro-perforated resonance formula, and S5, calculating the noise of the micro-perforated plate array. S5, performing simulation optimization and S6, accurately accounting airflow parameters, and locking a scheme meeting requirements; the silencer comprises a shell and a plurality of micro-perforated plates, and the multiple layers of micro-perforated plates are arranged in series. The invention has the advantages of no sound absorption material, low wind resistance (the air volume attenuation is less than or equal to 5%, and the pressure loss is less than or equal to 200Pa), the noise of the main wind path is reduced by 5-7dB (A), the service life is long, the operation and maintenance cost is low, and the requirements of the main wind path are met.

The invention discloses a low-turbulence noise-reduction hydro-generator rotor and a hydro-generator, and relates to the technical field of hydro-generators. Inter-pole wind shields are assembled between salient poles of the rotor, the peripheral cambered surfaces of the inter-pole wind shields are consistent with the peripheral radiuses of the poles, and the inner sides of the inter-pole wind shields are attached to magnetic pole transition surfaces, provided with ventilation holes and fixed through tensioning screws; and the fans at the two ends of the rotor adopt wing-shaped fan blades such as NACA0012 / 0016 / 0018 and the like. According to the hydro-generator, a metal micro-perforated plate is assembled on a main ventilation air path between a stator iron core and an air cooler, the array resistance-resistance performance of a non-sound-absorption material conforms to a silencer type silencer, plate bodies are arranged in series, an air inlet / outlet is bent by 45 degrees, and parameters are accurately designed through a resonance formula. Rotor hidden polarization and precise noise elimination of a main air path are achieved, double noise reduction enables the noise of the whole machine to be smaller than or equal to 65 dB (A), the wind resistance is low (the air volume attenuation is smaller than or equal to 5%), heat dissipation reaches the standard, the structure is stable, the operation and maintenance cost is low, and the requirements of a large-capacity and high-rotating-speed unit are met.

The invention discloses a novel double-sided photovoltaic sound barrier, and relates to the field of photovoltaic technology, the novel double-sided photovoltaic sound barrier comprises two mounting parts, and a transparent ultramicro perforated panel assembly and a photovoltaic panel assembly are inserted between the two mounting parts; locking units used for synchronously locking the transparent ultramicro perforated panel assembly and the photovoltaic panel assembly are arranged on the two mounting pieces respectively, and each locking unit comprises a first locking rod and a second locking rod which are slidably connected to the corresponding mounting pieces respectively; the operation part is arranged on the mounting piece and is used for driving the first lock rod to be slidably inserted into a first lock hole formed in the transparent ultramicro perforated panel assembly and driving the second lock rod to be slidably inserted into a second lock hole formed in the photovoltaic panel assembly; an operator can lock and fix the transparent ultramicro perforated panel assembly and the photovoltaic panel assembly on the mounting piece only by one step, so that the transparent ultramicro perforated panel assembly and the photovoltaic panel assembly can be more stably mounted on the mounting piece while the operation of the operator is facilitated.

The invention relates to a multi-physical mechanism synergistic light sound absorption and insulation integrated sandwich structure and a manufacturing method thereof.The multi-physical mechanism synergistic light sound absorption and insulation integrated sandwich structure comprises a panel, a sandwich layer and a micro-perforated panel which are arranged from top to bottom, a cavity is formed in the sandwich layer, and multiple sets of cantilever beam type harmonic oscillators arranged in an array are arranged in the cavity; the cantilever beam type harmonic oscillator comprises a cantilever beam base body and a metal rubber mass block fixed at the top end of the cantilever beam base body. According to the invention, through the coupling design of the micro-perforated plate and the internal grating cavity of the sandwich layer, the sound absorption frequency band is further widened, the sound absorption coefficient of the whole structure in a middle-high frequency band is improved, collaborative optimization of broadband sound absorption and low-frequency sound insulation is realized, the problem that a traditional harmonic oscillator is easy to lose efficacy in high-temperature and low-temperature environments is effectively solved, and the sound absorption efficiency is improved. And meanwhile, due to the design of the integrated sandwich structure, the problems of aging and layering of the adhesive layer in severe environments such as high temperature and damp and hot environments are avoided, and the integrity and durability of the structure are also remarkably improved.

The invention relates to the technical field of bladeless fans, in particular to a noise reduction air duct structure and a bladeless fan, the noise reduction air duct structure comprises an air outlet frame and a noise reduction flow guide assembly arranged in the air outlet frame, and airflow is input into the bottom of the air outlet frame and output from the air outlet frame; the noise reduction and flow guide assembly is arranged on the side edge, close to an air inlet, of the bottom of the air outlet frame and comprises a first micro-perforated plate, a plurality of micropores are formed in the first micro-perforated plate, airflow is guided through the first micro-perforated plate, and a noise reduction cavity is formed by the first micro-perforated plate and the side wall of the air outlet frame. The silencing flow guide assembly is adopted to enhance the sound wave diffusion effect, so that the operation noise of the bladeless fan is effectively reduced, and a quiet use environment is created for a user.

The utility model relates to the technical field of silencers, and discloses a high temperature resistant pipeline type silencer, which comprises a static pressure box and a sound absorption sheet, the inside of the static pressure box is fixedly connected with a silencing pipe, the inside of the silencing pipe is fixedly connected with the sound absorption sheet, the back surface of the silencing pipe is fixedly connected with a fixing device, the sound absorption sheet comprises a sound absorption body, and the fixing device is fixedly connected with the sound absorption body. The front face and the back face of the sound absorption body are fixedly connected with a flow guide cover, air grooves are formed in the two sides of the interior of the sound absorption body, micro-penetrating holes are formed in the two sides of the sound absorption body, and the micro-penetrating holes are evenly distributed and communicate with the air grooves. Air flow enters the silencer and is separated by the sound absorption sheets, sound enters the air grooves through the micro-perforated holes, the micro-perforated plate where the micro-perforated holes are located and the air grooves form a resonance sound absorption structure, the sound is absorbed, the sound absorption sheets are simple in structure, easy to clean and resistant to high temperature, and the silencer can be used in a high-temperature environment easily.

The application provides a sandwich micro-perforated plate sound absorption structure based on triple periodic minimal surface, comprising: a sandwich layer, comprising a plurality of triple periodic minimal surfaces arranged in an array in the XY direction; a plurality of sandwich layers arranged in an array in the Z direction, and a micro-perforated plate arranged between adjacent sandwich layers, wherein the micro-perforated plate is provided with a plurality of micro-holes; the inner cavities of the plurality of triple periodic minimal surfaces are connected in the XY direction and communicated in the Z direction through the micro-holes, thereby forming an inner cavity series connection system; and the outer cavities of the plurality of triple periodic minimal surfaces are connected in the XY direction and communicated in the Z direction through the micro-holes, thereby forming an outer cavity series connection system. The parallel structure of the inner cavity series connection system and the outer cavity series connection system is entangled and circled with each other, thereby effectively increasing the number of sound absorption peaks, so that the sound absorption effect of medium and low frequencies and wide frequencies is achieved. Meanwhile, the space utilization rate is high, and the structure weight is effectively reduced; and the structure volume can be changed according to the use requirement, and the compatibility is very strong.

This invention discloses a low-frequency noise reduction and sound insulation device for industrial applications, belonging to the field of noise control technology. The device includes an outer soundproof cover, an inner composite sound-absorbing structure, and an active noise control system. The outer soundproof cover is constructed of high-density board. The inner composite sound-absorbing structure is located on the inner wall of the outer soundproof cover and includes an acoustic metamaterial layer and a micro-perforated plate layer, which are spaced apart to form a first resonant cavity. The active noise control system includes: an error microphone embedded in the inner wall of the outer soundproof cover; a controller electrically connected to the error microphone; and a secondary sound source electrically connected to the controller and installed on the inner wall of the outer soundproof cover. This invention achieves broadband passive sound absorption through the composite structure of acoustic metamaterial and micro-perforated plate, providing a high signal-to-noise ratio environment for the active control system. Furthermore, the active control system based on the FxLMS algorithm precisely cancels residual low-frequency line spectra, achieving efficient and stable low-frequency noise reduction.

The utility model discloses a composite absorption device for enhancing low frequency sound absorption, which belongs to the technical field of pipeline acoustics black holes, and comprises a sound tube, a plurality of micro-perforated plates and a Helmholtz sound absorber, the micro-perforated plates are distributed at equal intervals along the axial direction of the inlet end of the sound tube and are arranged from large to small according to the perforated distribution area, and the Helmholtz sound absorber is arranged on the sound tube. Micro-pores are uniformly distributed in each micro-perforated plate; every two adjacent micro-perforated plates are connected through a separation ring; the Helmholtz sound absorbers are distributed at equal intervals in the axial direction of the outlet end of the sound tube, the diameters of the gradually-changed embedded necks are gradually reduced, the center of each Helmholtz sound absorber is provided with a gradually-changed embedded neck, and the inner diameter of each gradually-changed embedded neck is gradually reduced from the inlet end to the outlet end; every two adjacent Helmholtz sound absorbers are connected through a sound absorber cavity. According to the utility model, through the combination of the composite gradually-changed micro-perforated plate and the gradually-changed cascaded Helmholtz sound absorbers which are embedded in the neck part, low-frequency sound absorption and medium-high frequency broadband sound absorption are realized under the sub-wavelength length.

The invention relates to the technical field of building noise control, and discloses a building noise control method based on sound absorption cavity design, which comprises the following steps: arranging a plurality of sound absorption cavities in a concrete truss, filling a porous sound absorption material in the cavities, covering a micro-perforated plate, and optimizing the noise reduction effect by adjusting the geometric dimensions and the arrangement mode of the cavities. According to the method, the internal space of the concrete truss can be fully utilized, the design parameters are optimized in combination with experimental testing and numerical simulation, low-frequency noise propagation is effectively inhibited, and the additional burden on a building structure is relieved. The sound absorption cavity is formed in the inner space of the concrete truss, and the porous sound absorption material and the micro-perforated plate are combined, so that the inner space of the concrete truss is fully utilized, and the additional burden of a traditional sound insulation measure on a building structure is avoided; the geometric dimension and the arrangement mode of the sound absorption cavities can be flexibly adjusted according to the building floor height and the noise frequency characteristic, and therefore the low-frequency noise suppression capacity is improved.

This invention discloses a superstructure design method for suppressing noise loads in aircraft under high-speed environments, relating to the field of aircraft design. The method includes: obtaining characteristic noise frequencies through simulation using a typical cavity model; introducing various designable structures such as micro-perforated plates, Helmholtz resonators, and porous materials to construct acoustic superstructures capable of suppressing or phase-shifting noise loads at these frequencies; and solidifying the acoustic superstructure assembly style through ground tests or wind tunnel tests to facilitate its physical realization. This invention addresses the problem that commonly used cavity noise reduction methods cannot be applied to high-speed cavity structures by designing and optimizing various acoustic superstructure assemblies capable of suppressing or phase-shifting noise loads to achieve optimized suppression of noise loads in aircraft cavities under high-speed environments.

The present invention provides a micro-perforated panel sound absorber with an axially periodically rough surface annular micropore, which includes a micro-perforated panel, a rigid backing, and a cavity between the micro-perforated panel and the rigid backing. An annular sound absorption through-hole is provided on the micro-perforated panel, and the opening directions of the annular sound absorption through-holes are all perpendicular to the micro-perforated panel. The axially periodically rough surface morphology of the annular sound absorption through-holes provided on the micro-perforated panel is controlled by a function. The structure of the present invention is simple, light in weight, and has a high sound absorption coefficient in the mid-low frequency band. Through reasonable design of the structure, the sound absorption frequency band can be flexibly and effectively adjusted, and the sound absorption performance in the corresponding frequency band can be improved, having a wide range of engineering application prospects.

This application discloses a low-noise air supply system for cleanrooms, comprising an air supply power module, a silencing module, and an air outlet module. The silencing module includes a housing, connecting pipes, two noise sensors, and a noise reduction mechanism. Two connecting pipes are provided, each located at an opening at one end of the housing. The two noise sensors are respectively located at both ends of the housing. The noise reduction mechanism includes two square plates, four outer micro-perforated plates, and four inner micro-perforated plates. The four outer micro-perforated plates and two square plates form an outer noise reduction cavity, and the four inner micro-perforated plates, four outer micro-perforated plates, and two square plates form an inner noise reduction cavity. The noise reduction mechanism also includes multiple partitions that divide the outer and inner micro-perforated plates into multiple unit plates, which are connected by a connecting mechanism. The low-noise air supply system provided by this application can achieve noise reduction effects at different noise frequencies depending on different air supply conditions.

This invention relates to the field of bearings, specifically to a noise-reducing bearing with an integrated micro-perforated plate sound-absorbing structure. Rolling elements are disposed between the inner and outer rings of the bearing, and these rolling elements are positioned at intervals by a cage. A sealing ring is disposed on one side of the outer ring. The sealing ring has a mounting structure for installing the micro-perforated plate. The micro-perforated plate is annular and installed at the sealing ring, with a uniform array of micropores. An air cavity is formed between the micro-perforated plate and the sealing ring, constituting the back cavity of the sound-absorbing structure. In this invention, by setting a micro-perforated plate sound-absorbing structure at the bearing's sealing structure, the bearing maintains its original sealing function while possessing active sound absorption capability. When noise generated during bearing operation propagates to the micro-perforated plate, sound waves enter the micropores, generating viscous friction and heat exchange between the air and the pore walls within the micropore channels, thereby converting some of the sound energy into heat energy and dissipating it.

The invention discloses a submarine sound absorption material underwater sound absorption performance life prediction method and device, and relates to the technical field of deep learning. The method comprises the following steps: constructing a life prediction model integrating a macroscopic composite sound absorption model, a micro-fluid model, a micro-fluid model and a micro-perforated plate-like micro-structure model; acquiring a sound absorption material to be detected, inputting the sound absorption material to be detected into the model, calculating a sound wave loss transmission parameter value by utilizing a microscopic fluid model, a microscopic fluid model and a micro-perforated plate-like microscopic structure model, and inputting the sound wave loss transmission parameter value into the macroscopic composite sound absorption model to obtain sound absorption coefficients and sound pressures at different aging times; and determining the sound absorption performance and the material life according to the sound absorption coefficient curve and the sound pressure distribution diagram. According to the method, microstructure changes caused by aging are considered, a sound absorption coefficient curve at any time point is obtained, and life prediction of the long-term sound absorption performance of the underwater sound absorption material is achieved.

The utility model belongs to the technical field of musical instrument manufacturing, and particularly relates to a micro-perforated plate adjusting device for a bottom drum. Comprising a drum body shell and a drum beating surface arranged on the front side of the drum body shell, and further comprises a micro-perforated plate arranged in the drum body shell; the supporting mechanism comprises a supporting frame arranged in the drum body shell and located behind the micro-perforated plate and a supporting sleeve arranged in the middle of the supporting frame; the translation adjusting mechanism comprises a translation threaded rod of which the front end is connected with the middle part of the micro-perforated plate and the rear end is arranged in the supporting sleeve in a penetrating manner, a belt wheel part for driving the translation threaded rod to rotate so as to change the distance between the micro-perforated plate and the drumbeat surface, and an anti-rotation part for preventing the micro-perforated plate from rotating during translation. According to the utility model, the distance between the micro-perforated plate and the drumbeat surface is changed through the translation adjusting mechanism, so that the bottom drum has the effects of sound absorption and sound quality improvement at the same time.

The utility model provides a kind of road noise barrier based on sound-absorbing material, including barrier support assembly and barrier body, barrier support assembly includes the barrier support post of pair arrangement, and the sliding slot upper end of barrier support post is connected with buffer sliding block, and one barrier hanging pole is connected between buffer sliding block, barrier hanging pole is connected with barrier assembly support by hinged link, and barrier assembly support is connected with barrier body by bolt.The utility model in barrier body is converted into heat energy dissipation by the sound hole hole of sound hole board body, and the sound-absorbing micropore on microporous attraction cloth layer is based on micro-perforated plate theory, and the sound-absorbing coefficient is excellent in full frequency band, especially in low frequency part, further improve sound-absorbing effect, significantly improve the sound-absorbing performance of low frequency band by sound-absorbing cotton layer, and the porous structure of sound-absorbing cotton layer effectively insulates internal air convection and heat radiation, significantly reduce heat loss, while large aperture area absorbs and reflects sound wave, effectively reduce noise.

According to the complex closed space global low-frequency noise reduction method based on the active micro-perforated plate sound absorber, an active control technology is introduced into a small-size MPPA, the low-frequency acoustic reactance of a cavity of the MPPA is reduced by offsetting the sound field of the cavity of the MPPA, and the sound energy dissipation performance of the MPP is improved by breaking the waveform matching of the sound fields on the two sides of the MPP; the noise of the whole complex closed space is reduced in an active sound absorption mode, and meanwhile the problem that the noise reduction performance of some medium-high frequency resonance frequency points is weak due to coupling of a closed space sound field and an MPPA cavity sound field can be solved. The invested active control measure is low in cost, and the low-frequency noise reduction performance of the complex closed space is remarkable, so that the method has important engineering application value.

The utility model provides a composite sound absorption structure and a vehicle provided with the composite sound absorption structure, the composite sound absorption structure comprises a perforated plate, a sound absorption part and a support part; a gap exists between the sound absorption part and the perforated plate, a square containing cavity is defined by the micro-perforated plate in the sound absorption part, and the honeycomb filler is arranged in the square containing cavity; the perforated plate is provided with a plurality of through holes to form a sound transmission channel in the compartment body, so that noise reaches the sound absorption component connected with the perforated plate through the through holes, the micro-perforated plate of the sound absorption component is a direct reflection surface of the noise, and sound waves consume energy due to a viscous friction effect when passing through micropores of the micro-perforated plate. Cavities and micropores in the honeycomb filler form resonance sound absorption; and compared with a single-layer micro-perforated plate which can only cover low and medium frequency sound, the micro-perforated plates encircle to form the square accommodating cavity to form three groups of double-layer micro-perforated plate structures, namely an up-down double-layer micro-perforated plate structure, a left-right double-layer micro-perforated plate structure and a front-back double-layer micro-perforated plate structure, so that the sound absorption frequency band can be expanded to

The present application relates to a kind of sound barrier noise reduction structure and its design method, comprising: the high-frequency valley of high-frequency noise of the measured noise spectrum is determined as the valley frequency of the high-frequency sound insulation amount of the resonant unit, the low-frequency peak of low-frequency noise is determined as the peak frequency of the low-frequency sound insulation amount of the composite waveguide layer, according to the number of low-frequency peak determines the number of Helmholtz cavity;According to valley frequency, obtain the thickness of micro-perforated plate layer, the diameter of small hole on micro-perforated plate layer, the thickness of hollow cavity layer and its cross-sectional size parameter relationship formula, so as to optimize the selection of relevant parameters;According to each peak frequency, respectively calculate and obtain the volume of corresponding Helmholtz cavity, and the effective area, cross-sectional length relationship of its corresponding throat pipe, so as to optimize the selection of effective area.The structure designed by resonance system controls high-frequency noise, utilizes the Helmholtz cavity of composite waveguide layer to control low-frequency noise, realizes selective sound insulation in large frequency range.

The utility model discloses an exhaust silencer which comprises a first silencer body, one side of the first silencer body is in threaded connection with a hollow threaded connection pipe, and one side of the hollow threaded connection pipe is in threaded connection with a second silencer body. By means of the structure, the outer threads are arranged on one side of the first silencer body and one side of the second silencer body, the first inner threads are arranged on the other side of the first silencer body and the other side of the second silencer body, the sliding grooves are formed in the side walls of the first silencer body and the second silencer body, the sliding blocks are arranged in the sliding grooves, the sliding covers are arranged at the upper ends of the sliding blocks, and therefore silencing materials can be replaced conveniently; micro-perforated plates are arranged in the first silencer body and the second silencer body, flow guide plates are arranged on one sides of the micro-perforated plates, silencing material layers are arranged on one sides of the flow guide plates, filter cotton is arranged on one sides of the silencing material layers, and sound absorption cotton, metal fiber layers, glass fiber layers, porous ceramics and foam materials are arranged in the silencing material layers, so that the silencing effect of the silencer is better.

This invention discloses a multi-layer composite sound-absorbing device. The double-layer micro-perforated plate of this invention includes an upper micro-perforated plate and a lower micro-perforated plate, which are connected by a disc spring device. The upper and lower micro-perforated plates are connected around their perimeter by a frame, ensuring the disc spring device between them is compressed. The density gradient porous sound-absorbing material layer is composed of at least two layers of sound-absorbing material with different densities stacked together. This multi-layer composite sound-absorbing device is composed of resonant and resistive sound-absorbing materials, achieving excellent low-frequency broadband sound absorption, effectively solving low-frequency noise pollution problems in substations, converter stations, and other fields. By adjusting the plate spacing to change the compression state of the disc springs, different stiffness characteristics are obtained, thereby enhancing the resonant sound absorption effect for specific frequency bands of noise and specifically improving the sound absorption coefficient of the device for specific frequency bands of noise.

The utility model discloses a transparent defibration broadband straight pipe type micro-perforated plate silencer which comprises a silencer shell, a silencer inner wall and an air spring layer located between the silencer shell and the silencer inner wall. A plurality of through holes penetrating through the thickness direction are formed in the perforated surface protection supporting layer, a plurality of micro cracks are formed in the micro crack film sound absorption layer, and the micro cracks and the through holes are distributed correspondingly. The silencer adopts a transparent structure, so that the internal state of the silencer is convenient to observe; fiber porous sound absorption materials such as mineral wool are not filled, so that pollution and silencing performance degradation are avoided; and the perforated surface protection supporting layer is compounded with the micro-crack film sound absorption layer, so that the low-and-medium-frequency silencing performance of the silencer is also enhanced.

The present application provides a turbojet engine and aircraft, relating to the field of aero-engine technology, comprising a casing having a combustion chamber, a compressor and a turbine respectively arranged at the air inlet and air outlet of the casing, and a tail nozzle connected to the turbine, wherein the compressor and the turbine are connected in a transmission manner, and a micro-perforated plate metal foam composite structure is provided along the circumferential direction on the inner wall of the air inlet of the casing to reduce the noise generated when air enters the casing. A plurality of axially extending airflow channels are provided along the circumferential direction on the inner wall of the tail nozzle, each airflow channel including a plurality of interconnected airflow grooves, and the plurality of airflow grooves constituting the same airflow channel are connected end to end along the axial direction of the tail nozzle so that each airflow channel forms a Tesla valve structure. The flow diversion direction of the Tesla valve structure is consistent with the direction of airflow ejected from the casing into the atmosphere, effectively suppressing the generation of noise at the sound source, achieving a broadband noise reduction effect, and reducing the complexity and weight of the system, thereby controlling thrust loss to an extremely low level.

The invention designs an acoustic metamaterial sound insulation barrier capable of being used for reducing low-frequency noise in a transformer. The acoustic metamaterial sound insulation barrier comprises a supporting plate, a honeycomb-shaped frame, a distributed film acoustic metamaterial structure, a porous sound absorption material and a micro-perforated plate. Wherein the supporting plate is arranged at the bottom of the structure and supports the whole structure; the honeycomb-shaped frame is installed on the supporting plate and is perpendicular to the supporting plate. The micro-perforated plate is mounted at the topmost end of the honeycomb-shaped frame; the distributed film acoustic metamaterial structure is mounted below the micro-perforated plate; and the porous sound absorption material is arranged below the distributed film acoustic metamaterial structure. A traditional film acoustic metamaterial structure is optimized, the distribution mode of the elastic layers is improved on the basis that the elastic layers are added, the distributed film acoustic metamaterial structure is designed, the low-frequency sound insulation performance of the whole structure is optimized, and the sound insulation performance of the whole structure is improved. And a film acoustic metamaterial sound insulation barrier for reducing low-frequency noise in the transformer is designed by combining a traditional sound insulation material, so that the sound insulation performance of the barrier is improved.