68 results about "Perfboard" patented technology

A sound absorbing structure having excellent in sound absorbing performance, which is capable of achieving 0.4 or higher in the sound absorbing coefficient even in the case where a perforated panel is a thin plate such as aluminum foil within a range where a reduction in the weight of a vehicle body is not impaired and through holes have a large hole diameter in order to make the processing of providing a large number of through holes in the perforated panel. The sound absorbing structure 1 is the sound absorbing structure 1 for suppressing noise generated on a sound source side, which is equipped with: a perforated panel 2 having a large number of through holes 3 and a fiber material 4, which are provided so as to face the sound source side and provided so as to overlap with each other; and an air layer 5 provided behind the perforated panel 2, in which the density and the thickness of the fiber material 4 and the hole diameter and the aperture rate of the through holes 3 of the perforated panel 2 severally have a specific relationship.

Flexible abrasive sheet articles having precision thickness flat-topped raised island structures that are coated with a monolayer of equal sized abrasive agglomerate are described. Methods of producing high quality equal-sized spherical shaped composite abrasive agglomerate beads containing small diamond abrasive particles are described. Beads are produced by level-filling fine mesh screens or perforated sheets with a water based metal oxide slurry containing abrasive particles and then using a fluid jet to eject the abrasive slurry lumps from the individual screen cells into a dehydrating environment. Surface tension forces form the ejected liquid lumps into spheres that are solidified and then heated in a furnace to form ceramic beads. These porous ceramic abrasive beads can be bonded directly onto the flat planar surface of a flexible backing material or they can be bonded onto raised island surfaces to form rectangular or disk abrasive sheet articles. Abrasive articles having equal sized abrasive beads are particularly suited for lapping and raised island articles are suited for high speed lapping. Non-abrasive equal-sized beads can also be formed using this simple bead manufacturing process, which requires only a very low capital investment.

The invention discloses a broadband micro-perforated board sound absorber, a sound absorber performance prediction method and a sound absorber structure design method. The sound absorber comprises a surface micro-perforated board and a back chamber with unequal periodicity depth, and the back chamber is used for expanding sound absorption bandwidth of the sound absorber. The performance prediction method is used for predicting a sound absorption coefficient frequency spectrum of the sound absorber, through finite element simulation and experiment measurement verification, the performance prediction method is accurate and reliable; the structure design method used for effectively realizing the broadband micro-perforated board sound absorber comprises steps that (1), a depth matrix of the periodic back chamber is designed on the basis of the secondary residual sequence combination arrangement theory; and (2), evaluation is realized on the basis of the performance prediction method, combination of parameters of the sound absorber are sequentially determined, including total sound absorber width of the periodic back chamber, depth of each sub back chamber, board thickness of the micro-perforated board, aperture and perforated percentage. Through the sound absorber performance prediction method and the sound absorber structure design method, the micro-perforated board sound absorber having the broadband sound absorption performance can be accurately, reliably and simply designed.

Improved impact proof capability of a silicon microphone sensing element is achieved with a stopper element that limits the maximum vibration of moveable parts. The stopper has a lower anchor portion and upper finger portion that is elevated a certain distance above the diaphragm and overhangs the outer edges of the perforated plates. The stopper is formed on a stack consisting of a lower substrate, a middle dielectric layer, and an upper membrane layer. There is a back hole in the substrate and an air gap in the dielectric layer to allow sound to impinge on the diaphragm. The number of fingers and composition of the stopper is variable. Optionally, the stopper has a center support design and is formed on a center anchor within an opening in the diaphragm. An upper finger region overhangs the diaphragm near the center opening and thereby prevents breakage due to large vibrations.

The invention relates to the field of acoustic panel absorber and discloses a composite sound absorption structure based on combination of a micro-perforated board with an acoustic metamaterial. The composite sound absorption structure comprises a cover plate, side plates, a bottom plate, thin-film units, separation racks and mass blocks. The cover plate and the bottom plate are opposite to each other at an interval; and the side plates are connected with the cover plate and the bottom plate tightly to form a sound absorption back cavity. A plurality of micro sound absorbing holes and a plurality of unit holes are formed in the cover plate; one thin-film unit and one separation racks are arranged in each unit hole; and the thin-film units are fixed at the separation racks. The separation racks separate the unit holes into a plurality of cells. Each mass block is attached to the thin-film unit of one cell in each unit hole. Therefore, the sound absorption bandwidth can be broadened on the premise that the complexity of the sound absorption structure of the micro-perforated board is not increased; and thus the sound absorption effect can be enhanced.

The invention discloses a wide band sound absorption structure of film mechanical impedance combined with micropunched plate acoustic impedance, which comprises an upper support and a lower support which are fixedly and perpendicularly connected with a wall. A front micropunched plate and a rear micropunched plate are fixedly and perpendicularly connected between the two supports. A rectangular cavity is formed respectively between the front micropunched plate and the rear micropunched plate and between the rear micropunched plate and the wall. In the rectangular cavity formed by the rear micropunched plate and the wall, the inner side faces of the two supports are respectively and fixedly connected with a groove structure with the front face of a groove mouth facing the rear micropunchedplate in a vertically symmetrical mode. An elastic ring is closely bonded in the groove mouth of the groove structure in an adhesive mode and bonded with a composite film in an adhesive mode, and thecomposite film is formed by evenly pasting an elastic film and a sound insulation film. A mechanical impedance unit formed by films is added in a rear cavity. The micropunched plate is combined with mechanical impedance of films, the micropunched plate structure is utilized to absorb sound energy at middle and high band, and mechanical impedance of films is utilized to absorb sound energy for lowfrequency. The broadband sound absorption structure has the advantage that sound absorption frequency band is wide.

A magnetic separation apparatus for separating metallic material from a granulated stream of mixed metallic and nonmetallic material comprises a vibratory conveyor having a trough assembly mounted on a suspension system and coupled to a motor for causing the suspension system to vibrate. The trough assembly includes an upper trough having at least two sections aligned in a predetermined direction of material flow and a lower trough extending in the same direction as and beneath the upper. The upper trough includes one or more gaps of a predetermined width so as to permit material to fall onto the lower trough. Each trough is arranged so as to feed a different output collection point. At least one of the gaps between a downstream section of the upper trough and an upstream section of the upper trough includes the downstream section positioned at a height lower than the upstream section thereby forming a vertical drop between the two sections with the gap positioned therebetween. For each gap, an adjustable gate may be used for adjusting the width of the gap. A magnetic separator may be arranged above the gap in the upper trough so as to pick up free metal. Rubber granules fall through the gap and are deposited in a receptacle, while metal is deposited on the upper trough which feeds a separate receptacle. A declumping zone comprising at least one perforated deck may be situated in-line with the upper and lower troughs.

A perforated sheet obtained by forming holes in regular order in a metal sheet, the perforated sheet having holes arranged so that in a case of drawing a first tangential line extending in the tensile direction and passing through the bottom edge of a (1-1) hole, a second tangential line passing through the top edge of a (2-1) hole, a third tangential line passing through the bottom edge of the (2-1) hole, and a fourth tangential line passing through the top edge of a (1-2) hole, the second tangential line passes between the first tangential line and the fourth tangential line, and the third tangential line passes between the first tangential line and the fourth tangential line.

The invention relates to a sound insulation material and a manufacturing process thereof as well as a sound insulation board made of porous foamed aluminum materials and a manufacturing process thereof, aiming to solve the technical problems that the provided foamed aluminum particle board is required to have the characteristics of good sound insulation and sound wave absorption effects, intensity conforming to operational requirements and lower cost, and the provided process is required to have the characteristics of simple working procedures, convenient manufacturing and higher production efficiency. The invention has a technical scheme that the compound foamed aluminum particle board is a flat board formed by the mutual adhesion of foamed aluminum particles, wherein the surface of at least one plane of the flat board is compounded with a screen board or a perforated board. The manufacturing process is carried sequentially according to the following steps of: 1. crushing: crushing waste foamed aluminum materials into foamed aluminum particles with the sizes of 1-6mm in a crushing machine; 2. laminating and molding: uniformly mixing the foamed aluminum particles and adhesive according to the weight ratio of 1:3-7, then pouring in a mold, and laminating and molding in a press; and 3. drying the adhesive, and heating up to bake the molded board so as to dry and solidify the adhesive.

The invention discloses a wideband perforated plate which comprises a back plate. The back plate is provided with a plurality of first hollow chambers and a plurality of second hollow chambers. A second hollow chamber is arranged between each two adjacent first hollow chambers. The first hollow chamber comprises a pore plate A, and the second hollow chamber comprises a pore plate B. The pore plate A and the pore plate B are sound absorbing plates with a plurality of pores. The distance between the pore plate A and the back plate is larger than that between the pore plate B and the back plate. The wideband perforated plate can effectively enlarge a sound absorbing band width and realizes high sound absorbing performance. Furthermore the performance testing method according to the invention has advantages of simple operation and high practicability.

The invention discloses an efficient backwash-free high-precision filter, which belongs to the technical field of high-precision filters, and is characterized in that a filtering mechanism comprises more than three layers of laminated perforated plates, and the perforated plates are uniformly provided with filtering holes of which the hole diameters are greater than the diameter of the maximum particulate matters to be filtered, the distance D between the centers of the adjacent filtering holes is larger than or equal to two times of the diameter d of the filtering holes, pre-pressing mechanisms are arranged on the perforated plates, the adjacent perforated plates are tightly connected in a sliding mode through the pre-pressing mechanisms, and the adjacent perforated plates move relativelyin a staggered mode. More than two filtrate holes with different hole diameters are formed between every two adjacent filter holes in a staggered manner, the hole diameters of the filtrate holes aregradually reduced from top to bottom, and the filtrate holes are communicated to form a filtrate channel. The filter has high-precision filtering capacity, is convenient to clean and does not need tobe backwashed.

The invention provides refrigerating equipment which comprises a shell, a compressor, a sound isolating cover and a viscoelastic film layer, wherein an accommodating space is formed in the shell; thecompressor is arranged in the shell; the sound isolating cover at least comprises a sound absorbing layer and micro perforation plates which are successively arranged from outside to inside, the soundabsorbing layer is provided with a plurality of first sound absorbing parts penetrating the sound absorbing layer, and at least one perforation plate is arranged and a plurality of second sound absorbing parts penetrating the micro perforation plate are arranged on the micro perforation plate; when the radiation noise frequency of the compressor reaches a first frequency, the viscoelastic film layer resonates to consume energy and drive air to fluctuate in a reciprocating manner between the first and second sound absorbing parts to rub to consume energy; when the radiation noise frequency ofthe compressor reaches a second frequency, an air column in the second sound absorbing part resonates, rubs with the second sound absorbing part to consume energy, and at least can drive the viscoelastic film layer in the second sound absorbing part to vibrate to consume energy an drive air in the first absorbing part to fluctuate to consume energy. The refrigerating equipment solves the problem that the refrigerating equipment in the prior art is poor in sound isolating effect to the compressor.

Identity labeling system for a typical tight switch cover plate (5) used in a manner that is common for covering typical light switches and their electrical connections. The switch plate cover includes openings (25) that expose the electrical switches or devices and holes (35) to accept screws (45) that secure the switch plate cover onto the wall to cover the electrical connections. The improved method of labeling an existing switch plate comprises a label cover plate (15) attached to the switch cover plate (5) with the existing screw (45) that typically secures an existing switch cover plate to the wall. The cover plate is made of a clear material. The cover plate (15) includes a recess (55) in the back of the cover to hold the identity label (95) tabs (65) and grooves (75) to insure correct alignment during installation. The identity label (95) is a typical label that is used in offices to identify file folders. The labels come in perforated sheets (85) that can be imprinted by running them through a common computer printer to customize the labels to be used in any location to identify the switch.

A chucking device is provided, the chucking device having low dusting characteristics and high detergent properties, and being capable of vacuum-sucking even a substrate having a large warpage, and a chucking method using the chucking device is also provided. The chucking device vacuum-sucks and holds a wafer. The chucking device includes a perforated plate having a plurality of through-holes and being mounted with a wafer, the through-holes penetrating through both sides of the perforated plate; a porous plate that supports a surface other than a mounting surface of the perforated plate, on which the wafer is mounted, transmits a vacuum state to the wafer through the plurality of through-holes, and has a pore to limit a flow rate; and a vacuum pump that exhausts an air through the pore of the porous plate.

The invention relates to the technical field of airflow sound elimination, and discloses a novel micro-perforated plate muffler with barbed triangular micro-perforation. The micro-perforated plate muffler includes a shell, the shell internally sleeves two micro-perforated plates in a sealed mode through a sealing tape, the two micro-perforated plates are mutually symmetrical with the center line of the vertical direction of the shell as the axis of symmetry, the left side and the right side of the inner wall of the shell sleeve an air outlet pipeline and an air inlet pipeline correspondingly,and the right end of the air inlet pipeline penetrates through the shell and extends to the right side of the shell. According to the novel micro-perforated plate muffler with barbed triangular micro-perforation, a clockwise thread and a counterclockwise thread with opposite grains are formed in a distance adjusting device, a user conveniently and simultaneously adjusts and controls the distance between the two micro-perforated plates and the adjacent side of the shell according to the volume of a noise source and the audio frequency, by adjusting and controlling the depth of an inner cavity,noise and audio with different sizes are silenced conveniently, and the applicability of the novel micro-perforated panel muffler to noise reduction of different volume and different audio frequency is improved.

The invention discloses a multilayer micro-perforated plate sound absorption structure which comprises a frame body and a micro-perforated plate which are sequentially arranged at intervals, and a sound absorption cavity defined by the frame body and the micro-perforated plate. The frame body is a hollow right-angled hexahedron, and the micro-perforated plate is a right-angled hexahedron sheet. The total thickness of the frame body is 30-100 mm; through holes are uniformly distributed in the surface of the micro-perforated plate; the cross section of the through hole is circular or quadrilateral, and the size of the through hole is 0.1-1.0 mm; the perforation rate of the micro-perforated plate is 1.0-15.0%; the thickness of the micro-perforated plate is 0.1-1.0 mm; the number of the micro-perforated plates is 2-6; and the depth of the sound absorption cavity is 5-60 mm. Grooves are formed in one side of the frame body, and protrusions are arranged on the other side of the frame body, wherein the grooves are matched with the adjacent protrusion and are used for determining the position of the micro-perforated plate in the frame body and fixing the micro-perforated plate. The multilayer micro-perforated plate sound absorption structure is light in weight, small in surface density, high in full-band sound-absorbing coefficient and particularly good in low-frequency sound-absorbingperformance.

The invention relates to the technical field of industrial site noise reduction. The invention relates to a noise reduction device for industrial sites. The device comprises a main body device, an adjusting device, a noise reduction device and a cleaning device, the top end of the main body device is fixedly connected with the adjusting device; the top end of the adjusting device is fixedly connected with the noise reduction device; one end of the noise reduction device is fixedly connected with the cleaning device; the cleaning device is fixedly connected with the adjusting device; in the present invention, closed-cell foamed plastic, a filter screen, canvas, a noise reduction shell, a perforated plate, a hard fiber plate and the like are arranged; noise generated by production equipmentcan be absorbed through an acoustic board; and then the absorbed noise is transmitted to the noise reduction shell on the upper side and the lower side through a first sound guide pipe, a second soundguide pipe and a third sound guide pipe correspondingly, the noise is processed correspondingly, the noise processing efficiency and effect of the noise reduction shell are improved, the noise processed by the noise reduction shell cannot influence the surrounding working environment, and the noise cannot be transmitted remotely.

The invention discloses an array type silencer for a main exhaust fan with large air volume and strong mixed noises. The array type silencer comprises a reducing air pipe, a matrix type silencing unit, a silencer shell and a rainproof cap, wherein the matrix type silencing unit comprises a silencing unit body and flow guide heads at the two ends of the silencing unit body, and the silencing unit body is formed by compositing a sound absorption plate and sound absorption cotton. According to the invention, the characteristics of good low-frequency frequency multiplication and low-frequency sound absorption coefficients of an ultra-microporous aluminum perforated plate invented by Professor Ma Dayou are utilized, and thethe characteristics of good low-frequency frequency multiplication and low-frequency sound absorption coefficients at low, medium and high frequency of Huamei glass wool are utilized, so that low, medium and high-frequency noises in the noises are effectively eliminated.

The embodiment of the invention discloses a transformer substation silencing wall. The transformer substation silencing wall comprises a silencing plate arranged close to the side of a transformer substation and a ventilation plate arranged far away from the side of the transformer substation, a noise reduction cavity is arranged between the silencing plate and the ventilation plate, an external silencing structure is arranged on the silencing plate, an opening structure in transmission connection with the external silencing structure is arranged in the noise reduction cavity, and an internalsilencing structure is arranged in the noise reduction cavity and close to the ventilation plate. Through the silencing wall formed by the ventilation plate and the silencing plate, sound is subjectedto primary noise reduction treatment through the external silencing structure arranged on the silencing plate, and then subjected to secondary noise reduction treatment through the internal silencingstructure arranged in the noise reduction cavity, so that the noise reduction effect of the silencing wall is improved, and the problem that the sound absorption effect is reduced due to the fact that a sound absorption material in a perforated board is prone to damp in the prior art is solved.

An interchangeable fastener system for use in combination with a perforated board or other surface on a vertical plane includes a main fastener including a base for supporting the main fastener on the perforated board; the base surrounding a channel defined by an inner surface including opposing ramp surfaces to facilitate tightening of an attachment member, and a mechanical stop adjacent each ramp surface to prevent over rotation of the attachment member; and the attachment member including an elongate member having opposing ends, wherein the elongate member is sized and configured for selective passage through the channel from the front surface through the rear surface and wherein the attachment member may be selectively rotated so that opposing ends of the elongate member are each in engaged abutment against a corresponding one of the opposing ramp surfaces and mechanical stops.

The invention relates to a medium support device and a recording device. The medium support device suppresses deformation of a support portion, which supports a roll body around which a sheet-like medium is wound, with respect to a shaft portion. A medium support device (2) is provided with a support unit (3) that supports a roll body (R) around which a sheet-like medium is wound; a shaft part (4)which constitutes a rotating shaft of the roll body (R) and to which the support part (3) is fixed; a drive unit (10), and a rotating part (4) for rotating the roll body (R) supported by the supportpart (3). The shaft part (4) and the support part (3) are fixed together using a metal plate (32) having a flat surface (32b) in which an insertion hole (32a) through which the shaft part (4) is inserted is provided, and the outer peripheral part (32c) of the metal plate (32) is restricted in the rotational direction of the roll body (R) with respect to the inner peripheral part (33a) of the support part (3).

The invention discloses a multi-cavity sandwich type micro-perforated plate silencing structure. The silencing structure comprises a micro-perforated plate, wherein the micro-perforated plate is of acylindrical structure, and the exterior is provided with a shell; a resonance cavity of an annular structure is arranged between the shell and the micro-perforated plate; a plurality of partition plates are arranged between the shell and the micro-perforated plate in the radial direction; the partition plates divide the resonance cavity into a plurality of small resonant cavities with the same size; a sandwich plate is arranged in each small resonant cavity along the circumferential direction of the micro-perforated plate; a closed inner cavity is formed among the sandwich plates and the partition plates and the micro-perforated plate; a closed outer cavity is formed among the sandwich plates and the partition plates and the shell; and the shell and the two ends of the micro-perforated plate are connected through flanges. The micro-perforated silencing structure provided by the invention has the sound absorption performance of the medium-low frequency band and the medium-high frequencyband, is high in mechanical property, and is a multifunctional integrated structure for mechanically bearing-wide-frequency sound absorption.

The invention relates to the technical field of silencers, in particular to a sheet type silencer which comprises silencing sheets and a silencer outer shell, the silencer outer shell is suitable forcontaining at least two silencing sheets at intervals, and an airflow channel is formed between the two silencing sheets. The silencing sheets comprise silencing sheet shells which are at least partially composed of perforated plates and are composed of at least two kinds of perforated plates with different perforation rates, and sound absorption materials uniformly loaded in the silencing sheet shells. According to the sheet type silencer provided by the invention, the silencing sheet shells are composed of at least two perforated plates with different perforation rates, and different perforation rates are adopted such that silencing can be carried out on different frequency spectrum parts of a noise source, and the optimal overall silencing amount under the same pressure loss condition is achieved.

The invention provides a method for manufacturing a micro-perforated plate. Through the characteristic of heating shrinkage of a heat shrinkage plate, millimeter-level holes are machined in the heat shrinkage plate, and holes of the decimillimetre level or below are manufactured through heating shrinkage. Considering the defects that as for a traditional metal micro-perforated plate, a large number of holes of the millimeter level or below are difficult to manufacture in a thin plate, and the cost is high, through the characteristic of heating shrinkage of the heat shrinkage sheet, the millimeter-level holes are machined in the heat shrinkage plate and become micron-level holes through heating shrinkage. The micro-perforated plate structure is suitable for being machined, the price is low,mounting is convenient, exquisite patterns can be drawn, and the micro-perforated plate can be used for places, needing decoration and noise reduction, such as home decoration, halls, meeting rooms,hotels and sound barriers.

Disclosed herein is a composite panel for sound absorption that may absorb and block noise. The composite panel may include: a first perforated panel comprising first embosses and first perforation groups formed in a predetermined pattern, wherein the first embosses are formed by forming a plurality of cells and the first perforation groups are formed by collecting a plurality of first perforated holes; an embossed panel comprising second embosses formed by forming the plurality of cells and coupled to the first perforated panel wherein the embossed panel is laminated with the first perforated panel; and a sound absorbing and insulating material inserted between the first perforated panel and the embossed panel.

The invention discloses a frequency-adjustable sound absorption and insulation light composite board which comprises a perforated board, the perforated board is an open box-shaped body provided with a frame, a sound absorption layer, the damping layers, a middle thin board, a sound insulation layer and a sound insulation board are sequentially arranged in the box body from bottom to top in a tightly attached mode, the sound insulation board is fixedly connected with the frame of the perforated board, the damping layers are bonded to the plate face, opposite to the sound insulation layer, of the middle thin plate in a periodic arrangement mode. The sound absorption and insulation light composite board is simple in structure, diversified in form and convenient to manufacture, particularly, the periodic damping structure greatly reduces the surface density and cost of the sound absorption and insulation light composite board compared with a traditional laying full-damping structure, and the resonance and coincidence effect of components are restrained through laying of periodic damping. The periodic arrangement mode of the damping layers realizes sound insulation of noise sources with different frequencies.

The invention discloses a compound silencing device for air suction of a high speed centrifugal fan. The compound silencing device comprises an inlet flange, a first diverging tube, a second divergingtube, a silencing device, an upper end cover, a lower end cover and an outlet flange, wherein the small end of the first diverging tube is connected to the inlet flange and the large end of the firstdiverging tuber is connected to one surface of the upper end cover, the silencing device is mounted between the upper end cover and the lower end cover, the other surface of the lower end cover is connected to the large end of the second diverging tube, the small end of the second diverging tube is connected to the outlet flange, and the outlet flange is connected to an air inlet of the fan; thesilencing device comprises a silencing channel and a housing, the silencing channel is arranged in the housing and comprises a perforating plate, a surface cover layer and a sound absorption material,and the surface cover layer is located between the perforating plate and the sound absorption material. Based on expanding and resistant silencing principles, noises at low, intermediate and high frequency bands are eliminated effectively, and the silencing frequency band is wide. A high frequency failure problem of a conventional silencer is solved. The compound silencing device is simple in structure, simple in manufacturing process, easy to manufacture and convenient to maintain and mount.

The invention provides a low-frequency broadband composite micro-perforated plate sound absorption structure which comprises a perforated plate, a sound absorption back cavity with an opening in the upper end and a plurality of inclined back plates, submillimeter holes are formed in the perforated plate, the perforated plate covers the opening in the upper end of the sound absorption back cavity, and the inclined back plates are arranged in the sound absorption back cavity. All the inclined back plates are sequentially and fixedly connected end to end from top to bottom to form a snakelike fold line structure, the included angles between all the inclined back plates and the horizontal plane are the same, one ends of the inclined back plates are alternately fixed to the front frame plate and the rear frame plate, and slits are formed between the other ends of the inclined back plates and the left frame plate and the right frame plate. And all the inclined back plates divide the sound absorption back cavity into bent channels. The inclined back plate structure is added in the micro-perforated plate sound absorber, so that the frequency of the sound absorption peak of the micro-perforated plate sound absorber is reduced, and the sound absorption coefficient at the peak frequency is improved; an additional absorption peak is introduced on an original sound absorption curve; and after the porous material is added into the structure, the sound absorption frequency band of the perforated plate is effectively widened.

The invention relates to an air outlet cover assembly of a dust collector and the dust collector with same, the air outlet cover assembly comprises an air outlet cover, an air duct is defined in the air outlet cover, the air duct is provided with an air inlet and an air outlet, the air inlet is suitable for being communicated with an air outlet of a motor cover of the dust collector, and the air outlet is suitable for being communicated with the external environment; a silencing assembly is arranged in the air duct and comprises a micro-perforated plate, a plurality of micro-perforations penetrating through the micro-perforated plate in a thickness direction of the micro-perforated plate are formed in the micro-perforated plate, and the multiple micro-perforations are arranged at intervals; a back plate is provided with at least one back cavity, each back cavity is provided with a communication port, the micro-perforated plate is arranged on the side, provided with the communication port, of the back plate, and the communication port of each back cavity is opposite to the at least one micro-perforated hole, so that each back cavity is communicated with the at least one micro-perforated hole. According to the air outlet cover assembly, the sound attenuation and noise reduction effects are good, and therefore noise generated when the dust collector works can be better reduced, and the overall quality and user experience of the dust collector are improved.

The invention provides a multi-frequency-spectrum sound barrier unit plate. The multi-frequency-spectrum sound barrier unit plate comprises a supporting structure and a sound absorption structure. Thesupporting structure is a frame. And the sound absorption structure is clamped in the middle of the protective plate and is clamped in the groove of the supporting structure. In order to improve thesound absorption coefficient and the effective sound absorption frequency band width, a multi-layer perforated plate series composite structure with different apertures, different perforation rates and different cavity depths is adopted. And the panel and the micro-perforated plate, the micro-perforated plate and the micro-perforated plate, and the micro-perforated plate and the back plate form amulti-cavity structure. The medium-frequency noise and the low-frequency noise can achieve a good effect by consuming energy through resonance in the process of passing through the cavity, and the frequency band amplitude can be expanded for the noise with different frequencies through the cavities with different depths. The invention has the characteristics of high overall strength, universalityof aluminum profiles, few specifications, convenience in installation, flexibility in sound absorption material selection, low cost, wide sound absorption frequency amplitude and the like.