46results about How to "Improve sound absorption efficiency" patented technology

The invention provides a noise reduction sound absorption layer. The sound absorption layer comprises a keel and a sound absorption component, wherein the component comprises a micro-perforated panel 2, non-woven fabrics 3, a bi-component fiber mat 1 and a back plate 4, which are sequentially arranged along the direction from a noise source to a wall. The sound absorption principle of the noise reduction sound absorption layer couples the effects of bi-component resistive sound absorption and dual-layer resonance sound absorption; low-frequency noise of a substation transformer and a high-voltage reactor is effectively absorbed, and thus the target of reducing sensitive points on the boundary of a transformer substation and sensitive points out of the transformer substation is achieved.

The invention discloses a sound absorption wall, which comprises an inner wall, alkali-free glass sound absorption cotton, metal acoustical boards and keels, wherein embedded elements are arranged in the inner wall; the keels are welded on the embedded elements; the metal acoustical boards are fixed on the keels through screw bolts and screw nuts; and a position between the inner wall and the metal acoustical boards is filled with the alkali-free glass sound absorption cotton. The metal acoustical board perforation rate of the sound absorption wall can reach 40 percent or above. Compared with the prior art, the sound absorption wall has the advantages that the sound absorption efficiency is greatly improved; the structural stability is very good; deformation is avoided; the service life is long; the metal sound absorption wall achieves a good fireproof effect, is nonflammable and has high sound absorption efficiency; the installing and fixing mode of the metal acoustical boards is simple; the single-piece fixation of the metal acoustical boards is realized; and the fixation of other metal acoustical boards cannot be influenced by the mounting or the dismounting of any one metal acoustical board.

The invention relates to a single-legged strip seam sound absorption structure. The sound absorption structure comprises a panel formed by parallel arrangement of a plurality of plate strips, gap cavities with slit outlets are formed between the plate strips, fixed legs are arranged on one sides of the plate strips, and the fixed legs are used for fixing and mounting the plate strips. According tothe single-legged strip seam sound absorption structure, the strip seam sound absorption structure of the single fixed leg improves the sound absorption efficiency, meanwhile, the use amount of materials is reduced, and the production cost is reduced; due to the arrangement of the single fixed leg, so that the width of the gap cavities is increased, the collision and the friction probability of incident sound waves in a sound absorption cavity become larger, the dissipation of the sound waves is increased, the gap cavities form a Helmholtz perforated resonator and a resistant muffler at the same time, and the sound absorption effect is enhanced; the single fixed leg acts as a fixing foundation for the plate strips, the sound absorption structure does not form a strong limitation on the vibration of the plate strips under the influence of the incident sound waves, and the energy of the incident sound waves is facilitated to be dissipated through vibration of the plate strips.

The invention discloses an acoustic insulation cover, which comprises a cylindrical side wall and a top cover which is sealed and covered on the top of the side wall, wherein the side wall and the topcover independently comprise an acoustic absorption layer used for absorbing noise, and an acoustic insulation layer used for preventing noise from outwards radiating, and the acoustic absorption layer and the acoustic insulation layer are laminated and spliced from inside to outside. The acoustic insulation cover is characterized in that the acoustic absorption layer is internally at least provided with two acoustic absorption cotton layers; an acoustic absorption cavity is formed between the adjacent acoustic absorption cotton layers; and an acoustic absorption thin film capable of absorbing low and medium frequency noise is arranged in the acoustic absorption cavity. According to the acoustic insulation cover, the low and medium frequency noise can be effectively absorbed, acoustic absorption efficiency for the low and medium frequency noise is improved, noise reduction reliability is improved, convenience for a line to extend out is improved, the practicality of the acoustic insulation cover is improved, the thickness of an air layer in the acoustic absorption layer of the side wall in a use process is guaranteed, and therefore, the acoustic absorption efficiency and the acoustic absorption reliability of the acoustic absorption layer of the side wall are effectively improved. The invention also provides a design method for the acoustic insulation cover, and an acoustic insulation method for a compressor.

The invention discloses a water-based inorganic three-proofing coating and a preparation method thereof. The water-based inorganic three-proofing coating comprises the following components in parts byweight: 300 to 312 parts of water, 4 to 8 parts of a dispersant, 0.3 to 0.8 part of a neutralizer, 3 to 4 parts of an antifoaming agent, 180 to 200 parts of titanium dioxide, 180 to 200 parts of calcium carbonate, 3 to 5 parts of cellulose, 8 to 12 parts of an anionic organosilicon emulsion, 4 to 6 parts of a stabilizing agent, 210 to 220 parts of potassium silicate and 45 to 55 parts of a pure acrylic emulsion, wherein the anionic organosilicon emulsion comprises the following components: octamethylcyclotetrasiloxane, an emulsifier, deionized water, sodium hydroxide, gamma-glycidoxypropyltrimethoxysilane and a phenolic aldehyde amine curing agent. The water-based inorganic three-proofing coating has the advantages of suitability for low-temperature construction, high drying speed in a low-temperature environment, short curing time, high adhesive force and excellent sound absorption and noise reduction effect.

The invention provides a tail gas silencer for an automatic clipping system. The tail gas silencer comprises an axial hollow outer cylinder, a frustum-shaped axial hollow inner cylinder and a gas guide block, wherein the axial hollow outer cylinder comprises an inner wall, an outer wall and silencing cotton arranged between the inner wall and the outer wall, the inner wall is provided with gas passing holes distributed densely, one end of the outer cylinder is a gas outlet, and the other end of the outer cylinder is a gas inlet; the inner cylinder is arranged in the outer cylinder, the large section end of the inner cylinder is located at the gas outlet, and the wall of the inner cylinder is provided with gas passing holes; the gas guide block is located at the gas inlet and fixedly connected with the inner wall of the outer cylinder through a supporting piece, the gas guide block is in a solid cone shape, the cone bottom face of the gas guide block and the small section end of the inner cylinder are attached and located, and the gas guide block, the inner cylinder and the outer cylinder are arranged coaxially. According to the tail gas silencer, gas flow is made to vibrate and can enter the silencing cotton more easily, so that the sound absorption efficiency of the silencing cotton is improved.

A sound absorbing structure having a wide sound absorbing frequency range and high sound absorbing efficiency. A sound absorbing structure (1) is provided with a housing (2) having on one surface thereof a surface plate (2a) constructed from a porous plate, and also with porous plate units (3) which are each constructed from porous plates and are mounted in the housing (2). The porous plate units (3) are arranged side by side in the direction of the surface of the surface plate (2a). The porous plate units (3) each composed of two flat surface sections (3a, 4a) facing the surface plate (2a), and of side surface sections (3b, 4b) respectively connected to the flat surface sections (3a, 4a) and extending in a direction crossing the surface plate (2a). The space in the housing (2) is partitioned by the flat surface sections (3a, 4a) into spaces arranged side by side in a depth direction perpendicular to the surface plate (2a) and is partitioned by side surface sections (3b, 4b) into spaces arranged side by side in the direction of the surface of the surface plate (2a).

The present invention relates to a method for producing microporous metal plate and its product, belonging to the field of utilizing microporous plate technology to control noise pollution. In said invention chemically corrosion method is used to produce microporous metal plate, can product lots of metal microporous plates whose pore size is 0.4mm-0.1mm and perforating rate is in the range of 10.01%-0.06% and the pore size and pitch of pores can be regulated according to the requirement. Said invented production method is simple and easy to implement, its cost is low, and its microporous plate possesses good sound-absorbing effect and wide sound-absorbing frequency band, so that it possesses extensive application field.

The invention relates to a vehicle exhaust pipe noise reducing device, and belongs to the technical field of vehicle exhaust pipes. The vehicle exhaust pipe noise reducing device comprises an intake pipe, a noise reducing main body and an exhaust pipe; the noise reducing main body comprises an outer shell and an inner shell; a vacuum cavity is formed between the outer shell and the inner shell; and a first flow separation channel and a second flow separation channel are arranged in the inner shell, and are both provided with first noise absorbing cottons. Carbon dioxide of noise gas is absorbed through a carbon dioxide absorber, and is filtered through a filter screen; through arrangement of the flow separation channels, a flow separator, a noise absorbing plate and a noise absorbing pipe,sound waves are absorbed, so that the noise absorbing effect is good, and the noise absorbing efficiency is high; the filter screen is conveniently cleaned and replaced; and the noise reducing deviceis conveniently installed and fixed.

The invention discloses a combined self-regulation sound barrier and relates to the technical field of treatment on sound pollution. The combined self-regulation sound barrier comprises a sound barrier body, and a plurality of cavities are formed in the sound barrier body. The combined self-regulation sound barrier further comprises a control unit and a plurality of sound absorption units made of porous materials. The sound absorption units are arranged in the cavities and fixed to the side walls of the cavities. Each sound absorption unit and the side wall of the corresponding cavity are provided with electromagnets corresponding to each other. The control unit comprises sound sensors and a controller, and the sound sensors and the electromagnets are all connected with the controller. By controlling stretching or compression of the sound absorption units, the porous structure inside each sound absorption unit is changed, the absorption capacity for sounds of various frequency bands is changed, the combined self-regulation sound barrier can absorb sounds in a more targeted mode, and the noise absorption capacity of the combined self-regulation sound barrier is improved.

The invention relates to a noise reduction double-sided sound absorption barrier for a transformer, which comprises an upper V-shaped part with an upward opening, a middle vertical part and a lower V-shaped part with a downward opening, wherein the upper V-shaped part and the lower V-shaped part are the same in structure and material, the left sides of the upper V-shaped part and the lower V-shaped part and the left side face of the middle vertical part face one transformer noise source, and the right sides of the upper V-shaped part and the lower V-shaped part and the right side face of the middle vertical part face the other transformer noise source. Based on the characteristic that the transformer generates noise frequency, the internal size of the sound absorption barrier is designed,noise propagated through the foundation and the underground after the transformer oil tank is connected with the foundation can be effectively reduced, the spread of noise in the air can be effectively reduced, the barrier is particularly suitable for noise reduction and absorption of a plurality of transformers which are arranged in a row, the structure is stable, the sound absorption efficiencyis high, sound absorption and noise reduction between two transformers can be carried out, the operation environment of the transformer can be improved, and effective support is made for an environment-friendly power grid.

A sound-absorbing device for a track, which reduces noise generated from a part below a vehicle floor, among noises generated by a track, characterized in that a thin sound-absorbing panel with high impact strength is installed on the track near a noise source on or near the track. Here we offer sound absorbing devices for rails that not only have good sound absorbing effects, but also have durability such as impact resistance.

The invention discloses a sound-absorbing body, comprising a shell (5) and a perforated plate (1) connected with the shell (5), and further comprising a sound-absorbing assembly (2). The sound-absorbing assembly (2) is composed of at least two materials with different acoustic properties and in staggered arrangement. Interfaces (6) of the two different acoustical materials are serrated. The sound-absorbing assembly (2) includes sound-absorbing wedges (3) and sound-absorbing cotton (4). The sound-absorbing cotton (4) is filled between the sound-absorbing wedges (3) and the perforated plate (1).The sound-absorbing assembly (2) may be arranged in multiple layers. The sound absorbing body of the invention has a better sound-absorbing effect.

The invention discloses a self-circulating evaporating cooling distribution transformer, relating to the technical field of transformers. The self-circulating evaporating cooling distribution transformer comprises a transformer body, a base and a grounded rod lifting device, wherein the transformer body is fixed on the base, the grounded rod lifting device comprises a first chute, a first contactroller, a first connection rod, a first electric push rod, a second chute, a second contact roller, a second connection rod, a second electric push rod and a grounded rod, a rotary shaft penetrates the upper end of the grounded rod, a round hole penetrates the middle of the base, and the upper part of the round hole is opposite to the lower end of the grounded rod. The two electric push rods are adopted as a power source so as to drive the middles of the two connection rods to move up and down, so that one end of each connection rod can move in the chute through the contact rollers, the otherend of each connection rod and the grounded rod that are coaxially connected move up and down as a whole, therefore, the grounded rod can insert into and pull out from ground automatically, manual operation intensity is relieved, and the grounded rod is replaced more efficiently.

The invention relates to a shock-absorbing and noise-reducing sound-insulating room, which comprises four side walls, a bottom plate and a top plate, and is characterized in that a shock-absorbing pad made of rubber elastic body is laid on the surface of the bottom plate of the sound-insulating room, and the shock-absorbing pad is passed through a screw fixed on the bottom plate of the sound-proof room; the surface of the side wall and the top plate inside the sound-proof room is provided with a shock-absorbing layer made of PU foam by gluing; the surface of the shock-absorbing layer is provided with a sound-absorbing board, The sound-absorbing board includes a sound-absorbing board body, an anti-collision layer made of PU foam and a sound-absorbing layer made of glass fiber sound-absorbing cotton. The invention has the advantages of simple structure, high strength and good shock and noise reduction effect.

The invention relates to the technical field of acoustical materials, and particularly relates to a preparation method of an acoustical material. Cogongrass is used as a substrate, and is treated by phenylenediamine, inner fibers of the cogongrass is hardened preliminarily, then the cogongrass is subjected to pre-carbonation, saccharides, lignin and the like on the surface of the cogongrass are partially pyrolyzed, surface active groups are exposed, acrylic acid and methyl methacrylate are polymerized under the effects of a conditioner and ammonium persulfate, meanwhile, the acrylic acid and the methyl methacrylate are combined to the exposed surface active groups, the combination degree is improved, silylation is also introduced, the degree of combination between acoustical materials is increased, weather resistance is improved, a net-shaped structure is formed, and the sound absorption efficiency is improved; and because enzyme is added in a polymerization process, on one hand, bioactivity is improved, on the other hand, the cogongrass subjected to pre-carbonation is subjected to enzymolysis by the enzyme, abundant pore structures are formed in the cogongrass, and the sound absorption efficiency is further improved.

The invention discloses a road honeycomb noise reduction screen, comprising: a cover plate, a honeycomb cylinder arranged on the cover plate, a sound absorption material is arranged in the honeycomb cylinder, and through holes are arranged on the sound absorption material; a highway honeycomb A mass block is set in the hexagonal honeycomb cylinder in the sound insulation area at the bottom of the noise reduction screen. The mass block and the honeycomb cylinder are filled with sound-absorbing material and sealed. The quality of the mass block decreases layer by layer from bottom to top. They are set at an angle of 90° to 150° in the form of a folding screen or a folding fan. The road honeycomb noise reduction screen provided by the present invention can reduce the noise on the road to a reasonable range while achieving a low level of off-road noise by means of absorption and negative reflection, thereby maintaining the noise in the vehicle cabin at an acceptable 20 decibels for human ears comfort range left and right.

The invention relates to a noise-reducing double-sided sound-absorbing barrier for a transformer, which comprises an upper V-shaped portion with an upward opening, a middle upright portion, and a lower V-shaped portion with an opening downward. The structures of the upper V-shaped portion and the lower V-shaped portion are the same Same material, left side of upper and lower vee and left side of middle upright facing a transformer noise source, right side of upper and lower vee and right side of middle upright facing Another transformer noise source; the present invention designs the internal size of the sound-absorbing barrier based on the characteristics of the noise frequency generated by the transformer, which can effectively reduce the noise transmitted through the foundation and underground after the transformer oil tank is connected to the foundation, and can also effectively reduce the noise in the air. Spreading to a distance, it is especially suitable for noise reduction and sound absorption of multiple transformers arranged in rows. provide effective support.

The invention discloses a composite sound absorbing and insulating barrier. The composite sound absorbing and insulating barrier comprises a sound absorbing combined module, the sound absorbing combined module comprises an aluminum fiber microporous plate, and a waterproof and breathable du pont membrane, a carbon fiber sound absorbing cotton, an aluminum silicate acoustic baffle and a galvanized sheet shell are sequentially arranged on the aluminum fiber microporous plate. The composite sound absorbing and insulating barrier further comprises a sound absorbing combined module mounting bracket, the sound absorbing combined module mounting bracket comprises a plurality of mounting units composed of H-shaped steel, each mounting unit comprises the H-shaped steel on the left side, the H-shaped steel on the right side and beams on the upper portion and the lower portion, the mounting units are arranged on the upper row and the lower row, and a PC transparent screen is arranged between the mounting units on the upper row and the lower row. According to the composite sound absorbing and insulating barrier, the way of noise transmission is effectively blocked, the purpose of good noise governance is achieved, the field of vision cannot be blocked, after double sound insulation, the vibration effect is reduced, and the noise reduction effect is improved.

The invention discloses an installation method of a honeycomb sound-absorbing wooden decorative plate structure, and belongs to the field of sound-absorbing faceplate installation. The honeycomb sound-absorbing wooden decorative plate structure comprises a decorative plate layer, a connecting mechanism and a sound-absorbing layer, wherein the connecting mechanism is installed on the side surface of the decorative plate layer; the sound-absorbing layer is fixedly connected to the side surface of the decorative plate layer; the decorative plate layer comprises attraction seams, splice plates, transverse plate grooves and transverse strip-shaped plates, wherein the attraction seams are arranged on the front side surface of the decorative plate layer; the splice plates are fixedly connected to two side surfaces of the decorative plate layer; the transverse plate grooves are arranged on the back surface of the decorative plate layer; the transverse strip-shaped plates are fixedly connected to the inner sides of the transverse plate grooves; a connecting vertical rod is arranged at the rear side end of the connecting mechanism; and a connecting transverse rod is arranged at the top end of the connecting mechanism. By use of the honeycomb sound-absorbing wooden decorative plate structure, sound absorption efficiency can be improved, use of traditional fixing screws is reduced, overall mounting efficiency is improved, follow-up dismounting and mounting are facilitated, reutilization is facilitated, and resources are saved.

The invention relates to a sound-absorbing panel for a sound-proof room, which comprises a sound-absorbing panel body. One side of the sound-absorbing panel body is provided with an anti-collision layer made of PU foam, and one side of the anti-collision layer is provided with a sound-absorbing layer made of glass fiber sound-absorbing cotton. The sound-absorbing layer is provided with a plurality of first sound-absorbing ribs and a plurality of second sound-absorbing ribs. There is a reinforcement member, the reinforcement member includes a first reinforcement board and a second reinforcement board, the first reinforcement board is arranged vertically inside the sound-absorbing panel body, the number is one, and it is located in the center of the sound-absorbing board body, and the cross-section of the first reinforcement board is sawtooth shape; the second reinforcing plate is horizontally arranged inside the sound-absorbing panel body, and there are two in number, located at the upper and lower parts of the sound-absorbing panel body, and the cross-section of the second reinforcing plate has an S-shaped structure. The invention has the advantages of simple structure, high strength and good sound-absorbing effect.

The invention discloses a petal-shaped channel porous sound absorption structure, which is characterized in that a perforated panel is arranged on a rigid backing, a plurality of petal-shaped micro-channels are arranged on the perforated panel in parallel at intervals, and the radius r of each petal-shaped micro-channel meets the function relation of polar coordinates theta. The petal-shaped channel porous sound absorption structure is simple in structure, convenient to use, excellent in sound absorption effect, wide in sound absorption frequency band, suitable for indoor walls and inner wall faces of vehicles and capable of well replacing an existing artificial porous sound absorber.

The invention relates to a soundproof door frame for an acoustical experiment. The soundproof door frame comprises a door frame body, and a buffer layer composed of a rubber elastic body is arranged on the contact surface of the inner side of the door frame body and a door plate. Reinforcing layers composed of steel plates and sound-absorbing layers composed of PET fibers are sequentially arrangedon the two sides of the door frame body from inside to outside, and a plurality of first sound-absorbing convex strips and a plurality of second sound-absorbing convex strips are arranged on the exteriors of the sound-absorbing layers. The section of each first sound-absorbing convex strip is of a semicircle structure, the section of each second sound-absorbing convex strip is of an inverted-trapezoid structure, and the first sound-absorbing convex strips, the second sound-absorbing convex strips and the sound-absorbing layers are of an integrated structure. The first sound-absorbing convex strips and the second sound-absorbing convex strips are arranged at intervals and evenly distributed at the sound-absorbing layers. The ratio of the thickness L1 of each reinforcing layer to the thickness L2 of the door frame body to the thickness L3 of each sound-absorbing layer is 2:3:19, the sound-absorbing layers are connected with the reinforcing layers in a glued mode, and the reinforcing layers are connected with the door frame body in a glued mode. The soundproof door frame is simple in structure, high in strength and good in soundproof effect.

The invention discloses a noise reduction shell for a wing gate. The noise reduction shell comprises a shell body; the noise reduction device is arranged at the bottom of the shell body, and the noise reduction device comprises a pair of buffer strips which are oppositely laid at the bottom of the shell body; the supporting plate is fixed above the buffer strip through a plurality of supporting columns and is used for fixing a base of a wing gate machine core; the sound absorption layer I is laid at the bottom of the shell body and located between the buffer strips, and a gap is formed between the sound absorption layer I and the buffer strips; the sound absorption layer II is laid at the bottom of the supporting plate and located above the sound absorption layer I; the springs are arranged at intervals, and the upper ends and the lower ends of the springs are fixed to the sound absorption layer I and the sound absorption layer II respectively. The wing gate has the beneficial effects that the operation noise of the wing gate is remarkably reduced, and outward transmission of noise generated by a wing gate machine core is reduced.

The invention relates to a soundproof door for an acoustical laboratory. The soundproof door comprises a door body, and a buffer layer composed of a rubber elastic body is arranged on the contact surface of the outer side of the door body and a door plate. Sound-absorbing layers composed of PET fibers are arranged on the two sides of the door body, and a plurality of first sound-absorbing convex strips and a plurality of second sound-absorbing convex strips are arranged on the exteriors of the sound-absorbing layers. The section of each first sound-absorbing convex strip is of a semicircle structure, the section of each second sound-absorbing convex strip is of an inverted-trapezoid structure, and the first sound-absorbing convex strips, the second sound-absorbing convex strips and the sound-absorbing layers are of an integrated structure. The first sound-absorbing convex strips and the second sound-absorbing convex strips are arranged at intervals and evenly distributed at the sound-absorbing layers. The door body is internally provided with a reinforcing member which comprises three reinforcing steel plates, and the section of each reinforcing steel plate is of an S-shape structure. The soundproof door is simple in structure, high in strength and good in soundproof effect.

The invention discloses a sound-absorbing and heat-insulating pad of an automobile engine compartment, belonging to the technical field of automobile parts. The sound-absorbing and heat-insulating padcomprises: a sound-absorbing pad body having a near-heat-source area; and an aluminum heat-insulating layer, which is located in the near-heat-source area, wherein the edge of the aluminum heat-insulating layer is divided into a first part and a second part, the first part is connected with the sound-absorbing pad body so as to allow an echo cavity to be formed between the aluminum heat-insulating layer and the sound-absorbing pad body, and a sound wave inlet allowing sound waves to enter the echo cavity is formed between the second part and the sound-absorbing pad body and communicates withthe echo cavity. The sound-absorbing and heat-insulating pad utilizthese a conventional sound-absorbing pad and a conventional aluminum heat-insulating pad, the echo cavity is formed between the aluminum heat-insulating pad and the sound-absorbing pad only by allowing the aluminum heat-insulating pad to be arched, so cost is saved, the back-and-forth reflection energy of sound waves in the echo cavity is weakened, and meanwhile, the effects of heat insulation and sound absorption are achieved.

The invention relates to an aluminum honeycomb ceiling board with a micro-perforated sandwich layer. The aluminum honeycomb ceiling board comprises an upper aluminum plate, a lower aluminum plate and the micro-perforated sandwich layer, wherein the micro-perforated sandwich layer is bonded between the upper aluminum plate and the lower aluminum plate, a plurality of breakable dotted line grooves are evenly formed in the micro-perforated sandwich layer in a penetrating mode, all the breakable dotted line grooves are connected end to end to form a closed ring, and a to-be-pushed sandwich block which is connected with the micro-perforated sandwich layer through a plurality of ribs is formed in the closed ring. According to the aluminum honeycomb ceiling board, protruding aluminum plates and grooves on the upper aluminum plate and the lower aluminum plate correspond to the to-be-pushed sandwich block on the micro-perforated sandwich layer, the protruding aluminum plates, the grooves and the sandwich block can be nested through pressing operation, sound absorption structures extend into the aluminum plates, the sound absorption area is increased, the sound absorption efficiency is improved, and the protruding aluminum plates extend into the micro-perforated sandwich layer and is used for supporting the micro-perforated sandwich layer, so that the micro-perforated sandwich layer is prevented from deforming and stripping, and the whole ceiling board has the advantages of high strength and good sound absorption effect.

The invention discloses a mute fan. The mute fan comprises a fan main body, wherein an air inlet is formed in one side of the fan main body; the fan main body is hollow; an air chamber is formed in the fan main body; the hollow part of the fan main body surrounds the outside of the air chamber; the air inlet is provided with a sound absorbing piece and a top cover; the top cover is arranged at one end, which is away from the fan main body, of the air inlet; a projection part is formed in the middle of the side, which is close to the fan main body, of the top cover; a conical surface is formed on the periphery of the projection part; a first extension part is formed at the edge, which is positioned on the outer side of the air inlet, of the top cover; one end, which is close to the fan main body, of the sound absorbing piece surrounds the inner side of the air inlet; the other end, which is away from the fan main body, of the sound absorbing piece surrounds the inner side of the top cover; the diameter of the conical surface is gradually increased from one end which is close to the fan main body to the other end which is away from the fan main body; and the first extension part is gradually inclined to the direction close to the sound absorbing piece from one end which is close to the fan main body to the other end which is away from the fan main body. The mute fan is good in noise reduction property.