202 results about "Helmholtz resonator" patented technology

The technology described herein is directed towards one or more modular metasurfaces arranged with unit cells for sound absorption, in which the unit cells are based on Helmholtz resonators that are deployed proximate to a server, without substantially obstructing airflow from the server fan(s). Each sound absorbing unit-cells is designed and constructed based on a specific resonance frequency, and includes a neck portion and air chamber dimensioned to resonate at the desired resonance frequency and thereby inverse phase cancel corresponding narrowband frequencies of incoming sound waves. The metasurfaces can be arranged in a modular frame structure of surrounding unit cells, positioned behind the server's fan(s), with an opening in the frame structure to facilitate airflow therethrough, without obstructing or substantially obstructing the airflow to the surrounding environment.

The technology described herein is directed towards modular metasurfaces arranged with unit cells for narrowband, wideband and / or multiband sound absorption, in which the unit cells are based on Helmholtz resonators that are deployed in a server rack, proximate to a server, without substantially obstructing airflow from the server fan(s). Each sound absorbing unit-cells is designed and constructed based on a specific resonance frequency, and includes a neck portion and air chamber dimensioned to resonate at the desired resonance frequency and thereby inverse phase cancel corresponding narrowband frequencies of incoming sound waves. Differently-dimensioned unit cells can be built into a single metasurface module, thereby facilitating wideband and / or multiband sound absorption with that metasurface. The modular metasurfaces can be attached to the sidewalls of a server rack, or positioned in otherwise empty slots above and below a server, optionally coupled to blanking panels for covering the openings of those slots.

The invention discloses a bionic TENG sensor unit for an artificial throat and a preparation method thereof, and relates to the field of artificial throats, and the sensor unit comprises a gradient micro-dome friction layer, a strain amplification layer, an electrode layer and a back cavity substrate layer. The gradient micro-dome array realizes gradual contact through gradient change of height and diameter; the strain amplification layer converts vertical vibration into horizontal strain by using a cantilever beam-sliding block structure; the back cavity array selectively amplifies vibration at a specific frequency based on the Helmholtz resonance principle. The invention further provides a corresponding preparation method. The preparation method comprises the steps of back cavity forming, electrode deposition, microstructure manufacturing, surface treatment and the like. The sensor has the advantages of high sensitivity, good frequency selectivity and strong durability, and is particularly suitable for detecting weak laryngeal vibration signals of laryngeal patients.

The technology described herein is directed towards a metasurface arranged with unit cells for broadband and / or multiband sound absorption, in which the unit cells are based on the principles of Helmholtz resonators. Deeply subwavelength sound absorbing unit cells are designed and constructed based on desired resonance frequencies. Each unit cell includes a neck portion and air chamber dimensioned to resonate at a desired resonance frequency and thereby inverse phase cancel corresponding frequencies of incoming sound waves. Differently designed and arranged subgroups of unit cells are part of the metasurface, which can be positioned proximate to a noise source. As practical examples, the metasurface or multiple metasurfaces can be placed near or wrapped around a computer server or rack of servers to absorb fan noise. The metasurface components (including the unit cells) can be printed by a 3D printer to result in a thin, light-weight, and cost effective noise absorbing metasurface.

------ Acoustic Enclosure and Method for Leveling an Acoustic Enclosure The present invention relates to an acoustic enclosure (20) comprising a loudspeaker (21) mounted flush on a front face of the enclosure (20), characterized in that at least one Helmholtz resonator (26) is formed on the front face of the enclosure (20) between each lateral edge of the front face and the loudspeaker (21), the at least one Helmholtz resonator (26) being dimensioned to have a band gap to block the propagation, in the plane of the front face of the enclosure (20), of acoustic waves in the useful frequency band of the loudspeaker (21). Figure to be published with the abstract: Figure 6a

The technology described herein is directed towards a metasurface arranged with unit cells for narrowband sound absorption, in which the unit cells are based on Helmholtz resonators that can have their resonant frequencies selected via interchangeable portions. A sound absorbing unit cell is designed and constructed in two parts based on a desired resonance frequency, such as a neck portion and air chamber portion. The portions are dimensioned such that when coupled together, Helmholtz resonators are formed that resonate at a desired resonance frequency and thereby inverse phase cancel corresponding narrowband frequencies of incoming sound waves. A portion with different dimensions can be interchanged to adjust the resonant frequencies to cancel acoustic waves of different frequencies corresponding to noise, which can change over time. The unit cells can be distributed as part of a metasurface, which can be positioned proximate to a noise source to phase cancel the noise.

The technology described herein is directed towards a metasurface arranged with unit cells for narrowband sound absorption, in which the unit cells are based on Helmholtz resonators that can have their resonant frequencies adjusted via MEMS actuators. A sound absorbing unit-cell is designed and constructed based on a general resonance frequency, and includes a neck portion and air chamber dimensioned to resonate close to the desired resonance frequency and thereby inverse phase cancel corresponding narrowband frequencies of incoming sound waves. A bimorph MEMS actuator and / or moveable part in the resonators, controlled by a controller, facilitates changing of the airflow the unit cells to adjust the resonant frequencies thereof, to cancel acoustic waves of different frequencies corresponding to noise, which can change over time. The unit cells can be distributed as part of a metasurface, which can be positioned proximate to a noise source to phase cancel the noise.

The technology described herein is directed towards a metasurface arranged with unit cells for narrowband sound absorption, in which the unit cells are based on Helmholtz resonators that can have their resonant frequencies adjusted via a shared tuning element, e.g., a screw, or a piezoelectric actuator. A sound absorbing unit-cell is designed and constructed based on a general resonance frequency, and includes a neck portion and air chamber dimensioned to resonate close to the desired resonance frequency and thereby inverse phase cancel corresponding narrowband frequencies of incoming sound waves. Collectively moveable floors in the resonators facilitate changing the resonators' air cavity dimensions, to adjust the resonant frequencies to cancel acoustic waves of different frequencies corresponding to noise, which can change over time. The unit cells can be distributed as part of a metasurface, which can be positioned proximate to a noise source to phase cancel the noise.

The technology described herein is directed towards a metasurface arranged with unit cells for narrowband sound absorption, in which the unit cells are based on Helmholtz resonators that can have their resonant frequencies adjusted via actuators, e.g., piezoelectric motors. A sound absorbing unit-cell is designed and constructed based on a general resonance frequency, and includes a neck portion and air chamber dimensioned to resonate close to the desired resonance frequency and thereby inverse phase cancel corresponding narrowband frequencies of incoming sound waves. Moveable partitions in the resonators, controlled by piezoelectric actuators, facilitates changing of the resonators' air cavity dimensions, to adjust the resonant frequencies to cancel acoustic waves of different frequencies corresponding to noise, which can change over time. The unit cells can be distributed as part of a metasurface, which can be positioned proximate to a noise source to phase cancel the noise.

The technology described herein is directed towards a metasurface arranged with unit cells for narrowband sound absorption, in which the unit cells are based on Helmholtz resonators that can have their resonant frequencies adjusted via MEMS actuators. A sound absorbing unit-cell is designed and constructed based on a general resonance frequency, and includes a neck portion and air chamber dimensioned to resonate close to the desired resonance frequency and thereby inverse phase cancel corresponding narrowband frequencies of incoming sound waves. A moveable partition in the resonators, controlled by MEMS actuators, facilitates changing of the resonators' air cavity dimensions, to adjust the resonant frequencies to cancel acoustic waves of different frequencies corresponding to noise, which can change over time. The unit cells can be distributed as part of a metasurface, which can be positioned proximate to a noise source to phase cancel the noise.

The invention discloses a tunable MEMS (Micro Electro Mechanical System) structure based on a piezoelectric laminated structure, which comprises a substrate, the substrate is provided with a front surface and a back surface, the back surface of the substrate is provided with a back cavity, the back cavity provides a vibration space for a vibrating diaphragm, and a piezoelectric layer grows on the front surface of the substrate. A height plate is arranged on the front side of the substrate in a sealed mode, a dielectric cavity is formed by the internal space of the height plate and the substrate, the piezoelectric layer is located in the dielectric cavity, a through hole communicated with the dielectric cavity is formed in the side wall of the height plate, and a Helmholtz resonant cavity of the vibrating diaphragm is constructed by the dielectric cavity. According to the tunable MEMS structure based on the piezoelectric laminated structure, the height plate can form a Helmholtz resonant cavity of the vibrating diaphragm, the resonant frequency of the vibrating diaphragm is adjusted, and energy is efficiently coupled.

The invention discloses a neck embedded ring type Helmholtz resonator, which relates to the technical field of low-frequency sound absorption structures and comprises a resonator main body, an embedded neck and a porous material lining. The resonator main body comprises an outer wall surface and a closed cavity; the embedded neck part penetrates through the top wall surface of the main body and comprises a neck part wall surface and an internal periodic convex ring structure; the porous material lining is attached to the inner wall of the closed cavity, and a first gap is formed between the porous material lining and the wall face of the neck. According to the resonator, the sound energy dissipation capacity and parameter harmonility are improved through the neck circular ring, the low-frequency sound absorption capacity is enhanced through the porous material in the cavity, the sound absorption peak value and frequency can be regulated and controlled by adjusting the parameters of the neck and the circular ring and selecting the type of the porous material, and the resonator is simple in structure, wide in application and beneficial to production.

The invention relates to the field of building materials, in particular to a novel light sound insulation composite wallboard and a preparation method thereof.The composite wallboard comprises a first layer and a second layer which are compounded in sequence; the first layer is a gradient closed-cell foam layer, and the density of the first layer is distributed in a gradient increasing mode from the first surface away from the second layer to the second surface compounded with the second layer. The second layer is an integrated micro-perforated-adjustable neck depth honeycomb layer and comprises a micro-perforated panel, an adjustable neck depth element and a honeycomb core which are arranged in sequence; the micro-perforated panel is connected with the first layer, the neck depth adjustable element is an elastic film, and the elastic film, the micro-perforated panel and the honeycomb core jointly define a plurality of Helmholtz resonant cavities. According to the light sound insulation composite wallboard, efficient introduction of sound waves is achieved through impedance gradual change design, the adjustable resonance dissipation unit conducts targeted absorption on low-frequency noise, full-frequency-band and high-performance air sound isolation from low frequency to high frequency is achieved, and dual optimization of acoustic performance and space efficiency is achieved.

The invention discloses a strong premixing combustion chamber for restraining combustion noise based on a Helmholtz resonant cavity, and relates to the technical field of energy and power. Air and fuel enter the mixing cavity through corresponding connectors to be strongly premixed, premixed gas enters the hearth to be combusted through slit channels among water cooling channel branch pipes, a water cooling channel array can prevent backfire, the Helmholtz resonant cavity is connected with the hearth through a cavity neck and is provided with an air film cooling channel, the size of the Helmholtz resonant cavity needs to measure combustion noise, and a frequency spectrum is analyzed to obtain characteristic frequency. The neck length, the cross section area and the resonant cavity volume are calculated according to a Helmholtz resonance formula, and the sound absorption effect is verified in combination with a low-order thermoacoustic model. Combustion efficiency is improved through the strong premixing and slit water cooling design, tempering is prevented, NOx is reduced, the diffusion combustion problem is solved, the targeted design resonant cavity is matched with air film cooling, the defects that an existing silencing structure is large in size, poor in adaptation and low in high-temperature reliability are overcome, complex active control is not needed, cost is low, applicability is high, and the application range is wide. And cooperative control of high efficiency, low emission and unstable combustion is realized.

The invention discloses an active regulation and control type piezoelectric acoustic coding metasurface and a use method thereof in the acoustic field, the acoustic coding metasurface comprises a plurality of active regulation and control type piezoelectric acoustic coding units, and each active regulation and control type piezoelectric acoustic coding unit comprises a shell, a piezoelectric composite sheet and an external circuit; the two ends of the shell are open, and piezoelectric compacts are embedded in the shell. The piezoelectric compacts divide the interior of the shell into two symmetrical Helmholtz resonators. The piezoelectric composite sheet is connected with an external circuit of the shell; the external circuit switches open and short circuit states, so that the transmission phase difference of sound waves with working frequency is pi after passing through the active regulation and control type piezoelectric acoustic coding unit, and the sound waves are respectively used as a coding type 0 and a coding type 1. According to the invention, the problems of insufficient reconfigurable capability and slow switching response speed of the existing acoustic coding metasurface are solved.

The invention relates to the technical field of acoustic metamaterial, in particular to an acoustic metamaterial integrating vibration reduction, sound insulation and sound absorption and a preparation method of the acoustic metamaterial. The acoustic metamaterial capable of giving consideration to vibration reduction, sound insulation and sound absorption comprises a sound absorption functional layer, a sound insulation functional layer and a vibration reduction functional layer, the sound absorption function layer adopts a series-parallel Helmholtz resonant cavity coupling porous material and is used for realizing a broadband sound absorption effect; the sound insulation functional layer adopts a polyurethane filling gradient gradual change minimal curved surface and is used for realizing a broadband sound insulation effect; the vibration reduction function layer is coupled based on a band gap mechanism and used for achieving the broadband vibration reduction effect. The function of comprehensively controlling the environmental noise by means of vibration reduction, sound insulation and sound absorption can be achieved, the efficient control capability on the environmental noise is achieved, the design and manufacturing complexity is low, and the device can be conveniently used in various noise occasions.

The invention belongs to the technical field of sound absorption and noise reduction devices. In particular, the present disclosure provides acoustic structures and related methods that may be used to buffer or attenuate medium-high frequency acoustic waves. The sound absorption and noise reduction composite structure comprises a back plate; a honeycomb core; the honeycomb core is filled with the porous sound absorption material in four sections with equal thickness according to the density gradient change; the perforated top plate is bonded with the honeycomb core through an adhesive film; corresponding to the round holes in the perforated top plate, the porous material in the honeycomb core needs to be perforated. The problems that a traditional perforated plate-honeycomb sandwich structure is narrow in sound absorption frequency band and poor in middle-high frequency band sound absorption effect are solved, and meanwhile the defects that a porous material with low strength is insufficient in mechanical support and prone to loss in use are overcome. According to the sound absorption and noise reduction composite structure, the porous sound absorption material is filled in the honeycomb core in a gradient manner, and the through hole structure is introduced, so that the sound absorption performance of the composite structure in middle and high frequency bands is greatly improved, and the sound absorption and noise reduction frequency band width of the whole composite structure is widened. The device is simple in structure and has the characteristic of light weight.

The wave energy capturing and wave absorbing integrated device based on the Helmholtz resonance principle comprises a dike body, the dike body is sequentially provided with a front baffle, a front air chamber, a middle air chamber, a rear air chamber and a rear baffle in the wave incidence direction, and a three-stage series type wave absorbing structure is jointly formed; a front gas-guide tube and a rear gas-guide tube are respectively arranged at the tops of the front gas chamber and the rear gas chamber, and the front gas-guide tube, a top gas cavity of the middle gas chamber and the rear gas-guide tube are respectively connected with a confluence header pipe through pipelines; a one-way air inlet valve and a one-way exhaust valve are arranged on the top of each air chamber and each air guide pipeline; the air outlet end of the confluence header pipe is connected with a one-way air turbine. On the premise that the physical size of the structure and the construction cost are not remarkably increased, the wave absorbing frequency band can be effectively widened, particularly the wave absorbing performance on long-period waves is remarkably improved, and therefore the defects of a traditional breakwater and a traditional OWC device in the aspects are overcome.

The invention relates to the technical field of silencers, and discloses an impedance combined silencer which comprises a shell with an inner cavity, an air outlet is formed in the side wall of the shell, an air inlet is formed in the bottom of the shell, a sheet type resistive silencing section, a reactive sound absorption resonant cavity and an expansion section which are communicated are sequentially arranged in the inner cavity, the sheet type resistive silencing section is communicated with the air outlet, and the reactive sound absorption resonant cavity is communicated with the expansion section. The expansion section communicates with the air inlet; the first cavity wall and the second cavity wall of the resistant sound absorption resonant cavity are provided with a plurality of holes communicating with the inner cavity and the resistant sound absorption resonant cavity, the first cavity wall and the second cavity wall are oppositely arranged, and the air outlet faces the first cavity wall and the second cavity wall. According to the reactive sound absorption resonant cavity, the cavity wall holes are used for guiding sound waves to be coupled into the reactive sound absorption resonant cavity, Helmholtz resonance is formed, low-frequency noise is effectively absorbed, medium-high frequency noise is further absorbed with the assistance of the sheet type resistive noise elimination section, then the noise elimination frequency band is effectively widened, and low-frequency and medium-high frequency cooperative noise elimination is achieved.

The invention discloses a bent channel-Helmholtz composite low-frequency broadband sound absorber and a design method thereof. The sound absorber is formed by connecting a plurality of bent channel metamaterial sound absorption units around a Helmholtz resonator unit in parallel in a coupling mode. By controlling the impedance of the Helmholtz neck and the impedance of the bending channel, each unit is in an under-loss state, and then the overall critical coupling is realized by utilizing the area coupling effect, so that the sound absorber has the sound absorption coefficient of more than or equal to 0.5 in the frequency band of 267-382Hz under the thickness of 35mm. According to the sound absorber, broadband efficient sound absorption is achieved through impedance coupling of the Helmholtz resonators and the bent channels, the problems that a traditional structure is narrow in frequency band, difficult to regulate and control and the like are solved, and theoretical and technical supports are provided for low-frequency noise control.

The invention discloses a protective fence for municipal construction engineering. The protective fence comprises a fence body and a protection and noise reduction integrated module. The fence body is composed of a left support, a right support and detachable horizontal handrails, and a mounting groove is formed between every two adjacent handrails. The protection and noise reduction integrated module is installed in the groove through a base plate, a flexible bag body filled with shear thickening fluid is arranged on the outer side of the protection and noise reduction integrated module to serve as a protection unit, and the impact self-adaptive response characteristic is achieved. A Helmholtz resonance silencer is arranged on the inner side of the noise reduction device to serve as a noise reduction unit, a water collection funnel with a flow guide piece and a one-way drainage valve is integrated at the bottom of the silencer, and cooperation of efficient targeted noise reduction and automatic drainage and water accumulation prevention is achieved. The device integrates intelligent physical protection and acoustic treatment functions, the problems that a traditional fence is single in function, noise reduction equipment is prone to failure and inconvenient to maintain are solved, and the safety and environment management level of a building construction site is remarkably improved.

The application discloses a kind of 3D printing auxiliary freeze casting preparation wide frequency high-strength sound-absorbing material method, product and application, belong to sound-absorbing material technical field, including the following steps: using 3D printing process, polymer I and polymer II are prepared to obtain Helmholtz resonator, and slurry is dispersed in Helmholtz resonator by freeze casting process to realize dispersion orientation, and wide frequency high-strength sound-absorbing material is prepared.The application utilizes 3D printing to manufacture specific structure shape on demand, to a certain extent, the sound-absorbing performance and mechanical properties of sound-absorbing material are realized;Combined with the directional orientation of freeze casting technology, effective sound absorption in wide frequency range is realized, and the sound-absorbing performance of sound-absorbing material is greatly improved.

The invention relates to the technical field of underwater acoustic superstructures and acoustic camouflage, in particular to an acoustic superstructure dynamic regulation and control device and method based on a variable structure, and is suitable for deep sea equipment. The superstructure is of a hexagonal honeycomb structure, and each unit comprises a metal framework, a rubber layer, a push rod mechanism and a water cavity. The metal framework comprises a bottom plate, a side wall and six independent sectional type top plates, each top plate is connected with the side wall through a hinge, and a through hole is formed in the center of each top plate to form a Helmholtz resonant cavity neck; the rubber layer is attached to the inner surfaces of the bottom plate and the side wall; the push rod mechanism comprises a hydraulic push rod and a driving device. The hydraulic push rod is embedded in the rubber layer and hinged to the top plate. The top plate is closed in the silent mode to form an efficient sound absorption structure so as to reduce target acoustic characteristics, the intensity and spatial distribution of a reflected sound field are actively regulated and controlled by adjusting opening and closing of the top plate in the camouflage mode, and switching from acoustic stealth to dynamic camouflage is achieved. The method is suitable for acoustic stealth and acoustic camouflage tasks of deep sea equipment in a complex acoustic environment.

The invention relates to the technical field of fan blade hubs, in particular to an axial flow fan blade gradient porosity lightweight hub structure. Comprising a hub body and axial flow fan blades, the hub body comprises an annular wall, and arc-shaped grooves are formed in the annular wall in the circumferential direction; the arc-shaped groove comprises a mounting groove for mounting the axial-flow fan blade and a noise reduction groove without the axial-flow fan blade; grid-shaped connecting ribs are arranged at openings of the noise reduction grooves. The elastic pieces are arranged in the back cavities of the noise reduction grooves, the wave-shaped elastic pieces are arranged in the back cavities of the noise reduction grooves, captured vibration mechanical energy is converted into heat energy to be dissipated through the structural damping effect of the elastic pieces, and noise is restrained from the source; meanwhile, the elastic sheet is excited through the side face of the micro jet flow generated by modulating the airflow through the connecting rib grid, and the elastic sheet and the Helmholtz resonator composed of the back cavity volume and the rectangular hole opening act synergistically, specific aerodynamic noise is actively absorbed and offset, and therefore on the premise that the structural strength is guaranteed, the purposes of broadband noise reduction and light weight are achieved synergistically.

The utility model relates to the related technical field of sound insulation wall structures, and discloses a wall structure with a sound insulation function, which comprises a base layer wall, a first damping layer, a main sound insulation layer, a Helmholtz resonant cavity, a second damping layer and a facing layer, and a conical sound absorption wedge array is arranged in the Helmholtz resonant cavity. The sound insulation index of sound waves can be improved through the arrangement of the main sound insulation layer, and an effective air flow resistance optimization structure can be formed along with the arrangement of the conical sound absorption wedges in the Helmholtz resonant cavity, so that the aim of effectively absorbing sound is ensured; and through the arrangement of the first damping layer and the second damping layer, the inherent frequency of the wall body can be shifted to a non-sensitive frequency band, so that the vibration energy is attenuated, and the effective sound insulation purpose of the whole wall body structure is achieved.

The invention discloses a self-adaptive tuning light portable sound absorption device which comprises a sound absorption body, a circuit and control unit and a mechanical structure. The sound absorber comprises a flexible perforated plate and a back cavity support, and the flexible perforated plate and the back cavity support define a variable-volume Helmholtz resonant cavity. The mechanical structure comprises a telescopic adjusting mechanism which is connected with the back cavity support and used for adjusting the shape or size of the back cavity support. The circuit and control unit comprises a sensor, a microprocessor and a driving circuit. According to the invention, closed-loop intelligent control of sensing-decision-execution is realized, so that the volume of the Helmholtz resonant cavity is automatically and accurately adjusted, real-time sensing and self-adaptive regulation and control of an environmental noise spectrum are realized, a resonant frequency dynamically tracks a dominant noise frequency, and a sound absorption effect on an unstable noise source is remarkably improved; the device is light in weight, small in size and convenient to mount and dismount, and the deployment efficiency and the use convenience in temporary and mobile scenes are greatly 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.

This invention discloses a broadband duct silencing structure combining perforated tubes and cavities. The structure uses a galvanized housing as its main body, with perforated tubes coaxially arranged inside. A perforated partition divides the structure into front and rear silencing chambers. The front silencing chamber contains a first sound absorber and an air layer, forming a Helmholtz resonant cavity to efficiently eliminate low-frequency fan noise. The rear silencing chamber is filled with a second sound absorber and is equipped with perforated tubes, micro-perforated tubes, and micro-perforated inserts with progressively smaller apertures, forming a gradient microporous structure to achieve broadband absorption of mid-to-high frequency noise. The structure utilizes the airflow in the duct to drive the impeller to rotate, which in turn drives a bidirectional reciprocating screw via bevel gear transmission. This drives a delivery rod and a one-way valve to form a directional airflow circulation. The sound absorber is automatically purged through the air duct and comb-shaped air duct to remove fiber dust, preventing secondary pollution and stabilizing acoustic performance. This invention combines the advantages of low-frequency resonance silencing and mid-to-high frequency gradient microporous sound absorption, featuring a compact structure, wide silencing bandwidth, and stable and reliable operation.

The utility model discloses a sound reflecting cover structure for a stage. And the side plate of which the upper part is provided with the hanging bracket is arranged on a side plate balance frame with a hanging point through a hinge. A movable support with trundles and adjusting supporting legs is installed on the rear plate, and the movable support can be opened and can be fixed through a lock catch after being folded. A penetrating steel pipe is installed in the aluminum square pipes on the two sides of the aluminum honeycomb plate inner frame of the side plate, the side plate and the penetrating steel pipe are fixed together through screws, and a hanging bracket is installed on the penetrating pipe.

The invention discloses a low-frequency broadband sound absorption metamaterial plate based on a curved neck Helmholtz resonator, and belongs to the technical field of ventilation pipeline sound absorption. According to the device, an upper cover plate, a lower bottom plate and a separation frame for connecting the upper cover plate and the lower bottom plate are jointly enclosed to form a sealed cavity. The interior of the cavity is divided into a public cavity arranged in the center and four curved neck Helmholtz resonance units which are distributed around the public cavity in a central rotational symmetry mode. And the internal part of the curved neck Helmholtz resonance unit comprises a suspended L-shaped embedded pipe and a suspended C-shaped embedded sub-cavity structure. By means of the nested coupling effect of the L-shaped embedded pipe and the C-shaped sub-cavity, the structure effectively prolongs the sound propagation path, and an additional absorption peak is introduced. On the premise that the total volume is not increased, adjustable low-frequency broadband efficient sound absorption under the deep sub-wavelength scale is achieved, the structure is smooth, the thickness is small, geometric parameters are independently adjustable, and the influence on fluid resistance is small, and the engineering problem that low-frequency noise in a narrow space (such as a ventilation pipeline) is difficult to eliminate is effectively solved.