CN216596928U - Acoustic metamaterial unit cell, metamaterial ventilation noise reduction silencer comprising acoustic metamaterial unit cell, pipeline unit cell and pipeline - Google Patents

Abstract

The acoustic metamaterial unit cell and the metamaterial ventilation noise reduction device comprising the same comprise an inner cylinder and an outer cylinder which are coaxially arranged, wherein a main ventilation channel is arranged in the inner cylinder; the left side and the right side of the inner cylinder body and the right side of the outer cylinder body are respectively sealed by an annular left side panel and an annular right side panel, and a middle partition plate is arranged between the inner cylinder body and the outer cylinder body to divide a cavity between the inner cylinder body and the outer cylinder body into a first acoustic cavity and a second acoustic cavity; an acoustic opening communicated with the main air duct is formed in the cavity wall between the first acoustic cavity and the main air duct, and the first acoustic cavity and the cavity walls enclosing to form the first acoustic cavity form a first acoustic cellular; the high-porosity energy-absorbing medium is filled in the second acoustic cavity, a perforated plate provided with micro-perforations communicated with the main air duct is arranged on the cavity wall between the second acoustic cavity and the main air duct, and the second acoustic cavity, the high-porosity energy-absorbing medium and the cavity walls enclosing to form the second acoustic cavity form a second acoustic cell. The acoustic metamaterial unit cell has excellent noise elimination performance of low frequency, wide band and small size.

Description

Acoustic metamaterial cell and its metamaterial ventilation noise reduction muffler, piping cell, piping

technical field

The utility model belongs to high-end equipment (airplanes, rail trains, large ships, new transmission and transformation systems, high-tech electronics), modern functional buildings (highways, tunnels, waiting halls/halls, conference venues, recording/studio halls, anechoic rooms) ) The field of new materials and new structures for vibration reduction and noise reduction, in particular to an acoustic metamaterial cell used for noise reduction in ventilation pipelines and a metamaterial ventilation noise reduction device comprising the same.

Background technique

As a channel for conveying substances, the ventilation pipeline structure is widely used in various occasions such as air conditioning and ventilation of military equipment, engine intake and exhaust, gas turbines, and engine room heat dissipation. The main function of the pipeline system is to transport the fluid medium, but when the fluid medium is transported with the pipeline, the noise will also propagate along the pipeline. The noise of the ventilation pipeline is mainly generated by two aspects. One is that the vibration and noise generated by the mechanical equipment in the pipeline are transmitted along the pipeline. Eddy current and eddy resistance will also cause structural vibration and noise if the cross-sectional area changes such as the air supply and return air vents. Ventilation pipeline noise will directly affect the safety and reliability of related military equipment, affect the comfort of combatants' living environment, and endanger their health, especially low-frequency noise, which carries large energy, obvious line spectrum and propagation distance. Longer distances pose a direct threat to the stealth and vitality of naval ships and fighter jets.

The noise reduction design of the ventilation pipeline is mainly to control the noise on the noise propagation path. At present, the following two methods are mainly used to suppress the noise of ventilation pipelines: one is to use the principle of sound absorption to attach sound-absorbing materials (such as porous materials, foam materials, etc.) to the inner wall of the pipeline or install sound-absorbing structures (such as micro-perforated plates). Wait). However, the traditional noise control method using sound-absorbing materials has limited effect on low-frequency noise suppression, and has certain limitations in engineering applications. The other is to use the muffler principle to install mufflers on the pipeline, which has a wide range of applications in engineering. Traditional pipeline mufflers can be divided into resistive mufflers, resistive mufflers, impedance composite mufflers, etc. There are still some deficiencies in the traditional design of pipeline mufflers. For example, the resistance muffler needs a large space to effectively control low-frequency noise, and the muffler frequency band is narrow. Low frequency noise attenuation capability is poor. Therefore, it is urgent to design a new type of noise reduction device for ventilation pipelines to meet the needs of engineering and military equipment.

In recent years, metamaterial structures proposed and developed in the fields of acoustic physics and condensed matter physics provide new ideas for solving the problem of low-frequency noise in ventilation pipes. With the deepening of the research on structural vibration and noise reduction of acoustic metamaterials, the application of metamaterial design ideas to pipeline noise control has received extensive attention.

Acoustic metamaterials are artificial composite materials or structures with extraordinary physical properties in which artificial microstructures are arranged in a certain way. These paranormal physical properties include low frequency band gap, low frequency paranormal absorption, metamaterial parameters (negative mass density, negative elastic modulus, etc.), strong dispersion, and more. The core idea of acoustic metamaterials is to achieve modulation of elastic waves through subwavelength-scale microstructure design (that is, the structure size is much smaller than the wavelength of acoustic wave propagation), and to produce extraordinary physical effects. These extraordinary physical effects can be applied in the noise control of ventilation ducts, and are expected to realize the noise control characteristics that traditional materials/structures do not have.

Utility model content

In view of the defects and deficiencies existing in the prior art, the purpose of the present invention is to provide an acoustic metamaterial cell and a metamaterial ventilation noise reduction muffler, a pipeline cell and a pipeline comprising the same.

In order to realize the above-mentioned technical purpose, the technical scheme adopted by the present utility model is:

The acoustic metamaterial cell includes an inner cylinder and an outer cylinder, the inner cylinder is arranged in the outer cylinder and the two cylinders are coaxial, and the inner space of the inner cylinder is the main air passage;

The left and right sides of the inner cylinder and the outer cylinder are respectively closed by the annular left cover plate and the right cover plate. The cavity between the cylinders is divided into a first acoustic cavity and a second acoustic cavity;

The cavity wall between the first acoustic cavity and the main air passage is provided with an acoustic opening, and the first acoustic cavity and each cavity wall enclosing the first acoustic cavity constitute a first acoustic cell; an acoustic cavity communicated with the main air passage through the acoustic opening;

The second acoustic cavity is filled with a high-porosity energy-absorbing medium, the cavity wall between the second acoustic cavity and the main air passage is provided with a perforated plate with micro-perforations, and the second acoustic cavity and the second acoustic cavity are filled with The high-porosity energy-absorbing medium and each cavity wall enclosing and forming the second acoustic cavity constitute the second acoustic cell, and the second acoustic cavity is communicated with the main air passage through the micro-perforations on the perforated plate.

As a preferred solution of the present invention, the cross-sectional shapes of the inner cylinder and the outer cylinder are not limited, and the cross-sectional shapes of the inner cylinder and the outer cylinder are circles, ellipses or arbitrary polygons.

As a preferred solution of the present invention, the high-porosity energy-absorbing medium is a porous material with a porosity greater than 90%, such as an organic porous material, a metal porous material or a ceramic porous material.

In the utility model, the sound wave enters from the acoustic opening between the main air duct and the first acoustic cavity, and forms a resonance cavity with the first acoustic cavity; the sound wave enters from the perforation between the main air duct and the second acoustic cavity. The plate enters and forms an acoustic cavity with the highly porous energy absorbing medium in the second acoustic cavity.

As a preferred solution of the present invention, the first acoustic cavity is provided with N first baffles, and the N first baffles divide the first acoustic cavity into N+1 first acoustic small cavities , each first acoustic cavity and the main air passage are provided with acoustic openings, and N+1 first acoustic small cavities are respectively communicated with the main air passage through the corresponding acoustic openings, and N is zero or a positive integer.

As a preferred solution of the present invention, M second baffles are arranged in the second acoustic cavity, and the M second baffles divide the second acoustic cavity into M+1 second acoustic small cavities, each of which is a second acoustic cavity. The side walls between the small acoustic cavity and the main air passage are all perforated plates, and the perforated plate is provided with micro-perforations. M+1 second acoustic small cavities are respectively connected with the main air passage through the corresponding micro-perforations, and M is zero or positive integer.

As a preferred solution of the present invention, each of the first small acoustic cavities is provided with a plurality of third partitions, and the plurality of third partitions are alternately arranged to separate each of the first small acoustic cavities into a curled labyrinth cavity .

As a preferred solution of the present invention, each of the second small acoustic cavities is provided with a plurality of fourth baffles, and the plurality of fourth baffles are alternately arranged to separate each of the second small acoustic cavities into a curled labyrinth cavity.

On the other hand, the present invention provides a metamaterial ventilation noise reduction muffler, comprising an inlet pipe, an outlet pipe and n coaxial and closely connected acoustic metamaterial cells, the i-th acoustic metamaterial cell. The second acoustic cavity of the material cell is closely connected with the first acoustic cavity of the i+1th acoustic metamaterial cell, i=1, 2..., n, n is a positive integer greater than or equal to 2, The main air channels of the n acoustic metamaterial cells communicate with each other;

The main air passage of the first acoustic cavity of the first acoustic metamaterial cell is connected to and penetrates the inlet pipe, and the main air passage of the second acoustic cavity of the nth acoustic metamaterial cell is connected to and penetrates the outlet pipe .

As a preferred solution of the present invention, the lengths of the n acoustic metamaterial cells along the axial direction of the main air channel are the same;

Or, the lengths of the first acoustic metamaterial cell to the nth acoustic metamaterial cell arranged in sequence along the axial direction of the main air passage increase, decrease or randomly change in length along the axial direction of the main air passage. .

As a preferred solution of the present invention, the acoustic opening angles of the first acoustic cavity in the n acoustic metamaterial cells are the same;

Or, the size of the acoustic opening angle of the first acoustic cavity in the first acoustic metamaterial cell to the nth acoustic metamaterial cell arranged in sequence along the axial direction of the main air duct increases, decreases or is irregular. random change.

As a preferred solution of the present invention, the size of the micro-perforations on the perforated plate of the second acoustic cavity in the n acoustic metamaterial cells is the same;

Or, the size of the micro-perforations on the perforated plate of the second acoustic cavity from the first acoustic metamaterial cell to the nth acoustic metamaterial cell arranged in sequence along the axial direction of the main air channel increases, decreases, or Irregular random changes.

On the other hand, the present invention provides a metamaterial ventilation and noise reduction pipeline cell, including a left connecting pipe, a right connecting pipe and any of the above acoustic metamaterial cells, the first one in the acoustic metamaterial cell. The acoustic cell is connected with the left connecting pipe and the main air passage of the first acoustic cavity is connected with the left connecting pipe, the second acoustic cell in the acoustic metamaterial cell is connected with the right connecting pipe, and the second acoustic cell is connected with the right connecting pipe. The main air passage of the cavity is connected with the right connecting pipe.

On the other hand, the present invention provides a metamaterial ventilation and noise reduction pipeline, which includes m any of the above acoustic metamaterial cells, the m acoustic metamaterial cells are connected in series by connecting pipes, and the jth acoustic metamaterial cell is connected in series. The right connecting pipe of the metamaterial cell communicates with the left connecting pipe of the j+1th acoustic metamaterial cell, j=1,2...,m.

The acoustic metamaterial cell provided in the utility model has the excellent noise reduction performance of low frequency, wide band and small size. Metamaterial ventilation and noise reduction mufflers can be constructed by arranging multiple acoustic metamaterial cells in a compact manner without space. Both ends of the metamaterial ventilation and noise reduction muffler are respectively connected with an inlet pipe and an outlet pipe to form a metamaterial ventilation and noise reduction pipeline cell. A plurality of metamaterial ventilation and noise reduction pipeline cells are connected in series to form a metamaterial ventilation and noise reduction pipeline. The cells of each metamaterial ventilation and noise reduction pipeline in the metamaterial ventilation and noise reduction pipeline can be arranged periodically at equal intervals. The metamaterial ventilation and noise reduction muffler can couple adjacent formants, thereby broadening the noise reduction frequency band, and the metamaterial ventilation and noise reduction pipeline can not only better couple different formants, but also further utilize periodic tubes. The band gap characteristic of the channel realizes the further widening of the anechoic frequency band. The metamaterial ventilation and noise reduction muffler and the metamaterial ventilation and noise reduction pipeline can adjust the internal structural parameters of the acoustic metamaterial cell and the arrangement in the pipeline without changing the external volume of a single acoustic metamaterial cell. It can achieve the goal of pipeline noise reduction in different frequency bands, and overcome many shortcomings such as narrow noise reduction frequency band, large external space occupation, and poor environmental adaptability of traditional mufflers.

The utility model is used for noise reduction of ventilation pipelines, and has the functions of ventilation and broadband noise reduction. Broadband coupling noise reduction mechanism; compared with the traditional pipeline noise reduction device, the metamaterial noise reduction and noise reduction device has a wide range of noise reduction, the overall volume is small, occupies less external space, can effectively reduce the overall weight, and is simple to process and install. The cost is low; at the same time, without changing the external structure of the metamaterial cell, the internal structure parameters of the cell and the arrangement of the pipeline can achieve the goal of pipe noise reduction in different frequency bands, which overcomes the traditional pipeline. The muffling device has many shortcomings, such as narrow muffling frequency band, large external space occupation, and poor environmental adaptability.

Description of drawings

1 is a partial cross-sectional schematic diagram of an acoustic metamaterial cell provided in an embodiment of the present invention;

2 is a schematic structural diagram of an acoustic metamaterial cell provided in an embodiment of the present invention, wherein (a) is a schematic diagram of the internal structure after removing the left cover plate of the first acoustic cavity in the acoustic metamaterial cell, (b) is the top view after removing the left cover plate of the first acoustic cavity in the acoustic metamaterial cell, (c) is the interior after removing the right cover plate of the second acoustic cavity in the acoustic metamaterial cell Schematic diagram of the structure, (d) is the top view after removing the right cover plate of the second acoustic cavity in the acoustic metamaterial cell;

Fig. 3 is a schematic structural diagram when partitions are set in the acoustic metamaterial cell; wherein (a) is a schematic structural diagram when two first partitions are set in the first acoustic cavity in the acoustic metamaterial cell in one embodiment, (b) is a schematic diagram of the structure of the first acoustic cavity in the acoustic metamaterial cell in one embodiment when three first partitions are arranged, (c) is the second acoustic cavity in the acoustic metamaterial cell in one embodiment Schematic diagram of the structure when 2 second partitions are arranged in the body, (d) is a schematic diagram of the structure when 3 second partitions are arranged in the second acoustic cavity in the acoustic metamaterial cell in one embodiment, (e) is an implementation In the example, two first partitions are set in the first acoustic cavity in the acoustic metamaterial cell and the third partition is set at the same time to form a structure of a curled labyrinth cavity. (f) is the acoustic metamaterial cell in one embodiment. A schematic diagram of the structure of a curled labyrinth cavity formed after three first partitions are arranged in the first acoustic cavity and a third partition is arranged at the same time. (g) In one embodiment, two are arranged in the second acoustic cavity in the acoustic metamaterial cell. A schematic diagram of the structure of the curly labyrinth cavity formed after the second baffle and the fourth baffle are arranged at the same time, (h) is an embodiment in which three second baffles are arranged in the second acoustic cavity in the acoustic metamaterial cell, and a fourth baffle is arranged at the same time. A schematic diagram of the structure of the curled labyrinth cavity formed after the separator;

Fig. 4(a) is a schematic structural diagram of the first acoustic cell and the second acoustic cell having the same axial length in the acoustic metamaterial cell according to an embodiment of the present invention; Fig. 4(b) is the utility model A schematic structural diagram of the first acoustic cell and the second acoustic cell having different axial lengths in the acoustic metamaterial cell in a new embodiment;

5 is a schematic structural diagram of a metamaterial ventilation noise reduction muffler provided in an embodiment of the present invention;

6 is a cross-sectional view of a metamaterial ventilation noise reduction muffler provided in an embodiment of the present invention;

7 is a schematic structural diagram of a metamaterial ventilation and noise reduction pipeline cell provided in an embodiment of the present invention;

8 is a schematic structural diagram of a metamaterial ventilation and noise reduction pipeline provided in an embodiment of the present invention;

9 is a schematic structural diagram of a metamaterial ventilation and noise reduction pipeline provided in an embodiment of the present invention;

FIG. 10 is a comparison diagram of the transmission loss between the metamaterial ventilation and noise reduction muffler provided by an embodiment of the present invention and the traditional simple expansion cavity muffler.

FIG. 11 is a comparison diagram of the transmission loss between the metamaterial ventilation and noise reduction pipeline provided in an embodiment of the present invention and the traditional simple expansion cavity pipeline.

illustration:

1-acoustic metamaterial cell; 1a-first acoustic cell; 1b-second acoustic cell; 2-main air duct; 3-first acoustic cavity; 4-left cover plate; 5-acoustic Opening; 6-second acoustic cavity; 7-high-porosity energy-absorbing medium; 8-perforated plate; 9-intermediate partition plate; 10-right cover plate; 11-metamaterial ventilation noise reduction muffler; 12-inlet pipe; 13-exit pipe; 14-metamaterial ventilation and noise reduction pipeline; 15-metamaterial ventilation and noise reduction pipeline cell; 16-left connecting pipe; 17-right connecting pipe; 18-first baffle; 19- The first small acoustic cavity; 20-the second partition plate; 21-the second small acoustic cavity; 22-the third partition plate; 23-the fourth partition plate;

The purpose realization, functional characteristics and advantages of the present utility model will be further described with reference to the accompanying drawings in conjunction with the embodiments.

Detailed ways

The technical solutions in the embodiments of the present utility model will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, not all of them. Example. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present invention.

It should be noted that all directional indications (such as up, down, left, right, front, back...) in the embodiments of the present invention are only used to explain the difference between the various components under a certain posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication also changes accordingly.

In addition, descriptions such as "first", "second", etc. in the present invention are only used for description purposes, and should not be understood as indicating or implying their relative importance or implicitly indicating the number of indicated technical features. Thus, a feature delimited with "first", "second" may expressly or implicitly include at least one of that feature. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise expressly and specifically defined.

In the present utility model, unless otherwise expressly specified and limited, the terms "connection", "fixed" and the like should be understood in a broad sense, for example, "fixed" can be a fixed connection, a detachable connection, or an integrated; It can be a mechanical connection, an electrical connection, a physical connection or a wireless communication connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements or the interaction between the two elements. , unless otherwise expressly qualified. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but must be based on the realization by those of ordinary skill in the art. When the combination of technical solutions is contradictory or cannot be realized, it should be considered that the technical solutions The combination does not exist and is not within the protection scope required by the present invention.

As shown in FIG. 1 , this embodiment provides an acoustic metamaterial cell, and the acoustic metamaterial cell 1 includes:

It includes an inner cylinder and an outer cylinder, the inner cylinder is arranged in the outer cylinder and the two cylinders are coaxial, and the inner space of the inner cylinder is the main ventilation channel 2 . The cross-sectional shapes of the inner cylinder and the outer cylinder are not limited, and may be circular, elliptical or any polygon.

The left and right sides of the inner cylinder and the outer cylinder are respectively closed by the annular left cover plate 4 and the right cover plate 10, and an annular intermediate partition plate 9 is arranged between the inner cylinder and the outer cylinder to separate the inner cylinder. The cavity between the body and the outer cylinder is divided into a first acoustic cavity 3 and a second acoustic cavity 6;

An acoustic opening 5 is formed on the cavity wall between the first acoustic cavity 3 and the main air duct 2 , and the first acoustic cavity 3 and each cavity wall enclosing the first acoustic cavity 3 constitute the first acoustic cavity. Cell 1a; the first acoustic cavity 3 communicates with the main air duct 2 through the acoustic opening 5;

The second acoustic cavity 6 is filled with a high-porosity energy-absorbing medium 7 , the cavity wall between the second acoustic cavity 6 and the main air passage 2 is provided with a perforated plate 8 with micro-perforations, and the second acoustic cavity 6 , the high-porosity energy-absorbing medium 7 filled in the second acoustic cavity 6 and each cavity wall enclosing the second acoustic cavity 6 constitute the second acoustic cell 1b, and the second acoustic cavity 6 passes through the perforated plate 8 The micro-perforations on the upper are communicated with the main air passage 2.

In the embodiment shown in FIG. 1 , the main air duct 2 is circular, and the first acoustic cell 1a and the second acoustic cell 1b are both annular cavity structures.

The first acoustic cell 1a and the second acoustic cell 1b may be an integrally formed integral structure, or may be a structure that is fabricated separately and then connected together.

The sound wave enters from the acoustic opening 5 between the main air duct 2 and the first acoustic cavity 3, and forms a resonance cavity with the first acoustic cavity 3; the sound wave enters between the main air duct 2 and the second acoustic cavity 6 The perforated plate 8 enters, and forms a sound absorption cavity with the high-porosity energy-absorbing medium 7 in the second acoustic cavity 6 .

In the present invention, the main ventilation duct 2 is communicated with the first acoustic cavity 3 through the acoustic opening 5 to form an acoustic resonance effect, and the acoustic wave energy is reflected into the main ventilation duct 2 , which passes through the perforated plate 8 The micro-perforation is communicated with the second acoustic cavity 6, and the second acoustic cavity 6 is filled with a high-porosity energy-absorbing medium 7, which has a strong acoustic absorption effect and dissipates the sound waves in the form of heat energy. The perforated plate 8 mainly It is used to isolate the high-porosity energy-absorbing medium and the main air passage, and also has a certain absorption function for sound waves. The high-porosity energy-absorbing medium 7 is a material with a porosity greater than 90%, which can be organic porous materials such as glass wool, polystyrene foam, polyurethane foam, etc., or metal porous materials and ceramic porous materials. Each cavity wall of the first acoustic cavity 3 and each cavity wall of the second acoustic cavity 6 can be made of metal materials or non-metallic materials, typically steel, iron, aluminum alloy, plexiglass, resin, acrylic, aromatic Lun honeycomb paper, etc.

The resonant frequencies of the first acoustic cell 1a and the second acoustic cell 1b in the present invention are determined according to the control target. The opening angle of 5, the perforation rate and size of the perforated plate 8, and the parameters of the high-porosity energy-absorbing medium 7 can enhance the coordinated coupling between the resonance peaks of the first acoustic cell 1a and the second acoustic cell 1b, and widen the Low-frequency broadband anechoic performance of material cells. Referring to FIG. 2, it is a schematic structural diagram of an acoustic metamaterial cell provided in an embodiment of the present invention, wherein (a) is the internal structure after removing the left cover plate of the first acoustic cavity in the acoustic metamaterial cell Schematic diagram, (b) is the top view after removing the left cover of the first acoustic cavity in the acoustic metamaterial cell, (c) is after removing the right cover of the second acoustic cavity in the acoustic metamaterial cell The schematic diagram of the internal structure of , (d) is the top view after removing the right cover plate of the second acoustic cavity in the acoustic metamaterial cell. In the embodiment shown in Fig. 2, the first acoustic cavity in the acoustic metamaterial cell 1 is a complete annular cavity, and the opening angle of the acoustic opening 5 is 60 degrees as shown in Fig. A circular arc-shaped acoustic opening with an arc of 60 degrees is opened on the inner cylindrical wall of the acoustic cavity. The second acoustic cavity 6 in the acoustic metamaterial cell 1 is completely filled with a high-porosity energy-absorbing medium 7, and the inner cylindrical wall of the second acoustic cavity 6 is provided with micro-perforations arranged in an array, and micro-perforations are provided. The corresponding area of is the perforated plate 8.

Further, in some preferred embodiments of the present invention, the first acoustic cavity 3 is provided with N first partitions 18 , and the N first partitions 18 divide the first acoustic cavity 3 into N+1 first acoustic small cavities 19, each of the first acoustic small cavities 19 and the main air duct 2 is provided with an acoustic opening 5, and the N+1 first acoustic small cavities 19 pass through the corresponding acoustic The opening 5 communicates with the main ventilation channel 2, and N is zero or a positive integer. Referring to (a) and (b) in FIG. 3 , (a) is a schematic structural diagram when two first partitions are arranged in the first acoustic cavity in the acoustic metamaterial cell in one embodiment, and the two first The partition plate 18 equally divides the first acoustic cavity into two semi-annular first acoustic small cavities 19 , and fan-shaped acoustic openings 5 are opened on the inner side walls corresponding to each of the first acoustic small cavities 19 . (b) is a schematic diagram of the structure of the first acoustic cavity in the acoustic metamaterial cell when three first partitions are arranged in an embodiment, and the three first partitions 18 divide the first acoustic cavity into three equal parts. A fan-shaped first acoustic cavity 19 is provided, and a fan-shaped acoustic opening 5 is opened on the inner side wall corresponding to each first acoustic cavity 19 .

Further, in some preferred embodiments of the present invention, M second partitions 20 are arranged in the second acoustic cavity 6 , and the M second partitions 20 divide the second acoustic cavity 6 into M+1 There are two second acoustic small cavities 21, and the side wall between each second acoustic small cavity 21 and the main air duct 2 is provided with a perforated plate 8 with micro-perforations, and M+1 second acoustic small cavities 21 pass through the corresponding The micro-perforation is communicated with the main air channel 2, and M is zero or a positive integer. Referring to (c) and (d) in FIG. 3 , (c) is a schematic structural diagram when two second partitions are arranged in the second acoustic cavity in the acoustic metamaterial cell in one embodiment, and the two second partitions are The plate 20 equally divides the second acoustic cavity 6 into two semi-annular second acoustic small cavities 21 , and the inner wall corresponding to each second acoustic small cavity 21 is provided with a perforated plate 8 with micro-perforations. (d) is a schematic structural diagram when three second baffles are arranged in the second acoustic cavity in the acoustic metamaterial cell in one embodiment, and the three second baffles 20 divide the second acoustic cavity 6 into three equal parts The fan-shaped second acoustic small cavity 21 is provided with a perforated plate 8 with micro-perforations on the corresponding inner side wall of each second acoustic small cavity 21 .

Further, in some preferred embodiments of the present invention, the first acoustic cavity 3 is provided with N first partitions 18 , and the N first partitions 18 divide the first acoustic cavity 3 into N+1 first acoustic small cavities 19, each of the first acoustic small cavities 19 and the main air duct 2 is provided with an acoustic opening 5, and the N+1 first acoustic small cavities 19 pass through the corresponding acoustic The opening 5 communicates with the main ventilation channel 2, and N is zero or a positive integer. At the same time, a plurality of third partitions 22 are arranged in each of the first small acoustic cavities 19 , and the plurality of third partitions 22 are alternately arranged to separate each of the first small acoustic cavities 19 into a curly labyrinth cavity. Referring to (e) and (f) in FIG. 3 , (e) is formed after two first partitions and a third partition are simultaneously arranged in the first acoustic cavity of the acoustic metamaterial cell in one embodiment. Schematic diagram of the structure of the coiled labyrinth cavity. (f) is a schematic diagram of the structure of the curly labyrinth cavity formed after three first partitions are arranged in the first acoustic cavity in the acoustic metamaterial cell and the third partitions are arranged at the same time in one embodiment. The coiled labyrinth cavity can effectively reduce the resonance frequency of the first acoustic cell.

Further, in some preferred embodiments of the present invention, M second partitions 20 are arranged in the second acoustic cavity 6 , and the M second partitions 20 divide the second acoustic cavity 6 into M+1 There are two second acoustic small cavities 21, and the side wall between each second acoustic small cavity 21 and the main air duct 2 is provided with a perforated plate 8 with micro-perforations, and M+1 second acoustic small cavities 21 pass through the corresponding The micro-perforation is communicated with the main air channel 2, and M is zero or a positive integer. At the same time, several fourth partitions 23 are arranged in each of the second small acoustic cavities 21 , and the several fourth partitions 23 are arranged at alternate intervals to separate each of the second small acoustic cavities 21 into a curled labyrinth cavity. Referring to (g) and (h) in FIG. 3 , wherein (g) is an embodiment in which two second baffles are arranged in the second acoustic cavity of the acoustic metamaterial cell and a fourth baffle is arranged at the same time to form a curl. Schematic diagram of the structure of the labyrinth cavity, (h) is a schematic diagram of the structure of a curled labyrinth cavity formed after three second partitions and a fourth partition are arranged in the second acoustic cavity in the acoustic metamaterial cell in one embodiment. The curled labyrinth cavity can effectively change the effective sound absorption range of the porous material cavity.

It can be understood that those skilled in the art can control and adjust the amount of the high-porosity energy-absorbing medium filled in the second acoustic cavity as required, and the second acoustic cavity can be fully or partially filled with the high-porosity energy-absorbing medium. The high-porosity energy-absorbing medium is a material with a porosity greater than 90%, which can be organic porous materials such as glass wool, polystyrene foam, polyurethane foam, etc., or metal porous materials and ceramic porous materials.

It can be understood that the lengths of the first acoustic cell 1a and the second acoustic cell 1b along the axial direction of the main ventilation duct can be designed as required, and the first acoustic cell and the second acoustic cell are located along the main ventilation duct. The length of the channel in the axial direction may be the same or different. The length of the first acoustic cell in the axial direction of the main air channel may be greater than the length of the second acoustic cell in the axial direction of the main air channel. The length of an acoustic cell in the axial direction of the main air passage is smaller than the length of the second acoustic cell in the axial direction of the main air passage. Referring to Figure 4, (a) in Figure 4 is a schematic structural diagram of the first acoustic cell and the second acoustic cell in the acoustic metamaterial cell in an embodiment of the present invention having the same axial length; Figure 4 (b) ) is a schematic structural diagram of the first acoustic cell and the second acoustic cell having different axial lengths in the acoustic metamaterial cell according to an embodiment of the present invention.

The side cavity walls of the first acoustic cavity 3 and the second acoustic cavity 6 in the present invention can be made of metal materials or non-metallic materials, typically steel, iron, aluminum alloy, plexiglass, resin, acrylic, Aramid honeycomb paper, etc.; the first separator 18, the second separator 20, the third separator 22, and the fourth separator 23 can be metal materials or non-metallic materials, typically steel, iron, carbon fiber composite materials, Plexiglass, acrylic, PVC, aramid honeycomb paper, etc.

5 and 6, in another embodiment of the present utility model, a metamaterial ventilation noise reduction muffler 11 is provided, comprising an inlet pipe 12, an outlet pipe 13 and n coaxial and closely connected above-mentioned any In the acoustic metamaterial cell 1 provided in an embodiment, the second acoustic cavity of the ith acoustic metamaterial cell 1 is closely connected with the first acoustic cavity of the i+1th acoustic metamaterial cell, i=1, 2..., n, n is a positive integer greater than or equal to 2, and the main air channels 2 of the n acoustic metamaterial cells 1 communicate with each other;

The main air passage 2 of the first acoustic cavity of the first acoustic metamaterial cell 1 is connected to and through the inlet pipe 12 , and the main air passage 2 of the second acoustic cavity of the nth acoustic metamaterial cell 1 is connected to the inlet pipe 12 . The outlet pipe 13 is connected and penetrated. In FIG. 5, n is 6.

In the embodiment shown in FIG. 5 , the lengths of the n acoustic metamaterial cells along the axial direction of the main air channel are the same, and the first acoustic cavity and the second acoustic cavity in each acoustic metamaterial cell are along the main air passage. The lengths of the air passages in the axial direction are all the same. It can be understood that what is shown in FIG. 5 is only a preferred embodiment of the utility model. In practical applications, those skilled in the art can adjust the first acoustic cavity in each acoustic metamaterial cell in the metamaterial ventilation and noise reduction muffler as required. The length of the body and the second acoustic cavity along the axial direction of the main air channel. The lengths of the first acoustic metamaterial cells to the nth acoustic metamaterial cells arranged in sequence along the axial direction of the main air channel can be designed to be different along the axial direction of the main air channel, or to change in a certain regularity. Such as increasing and decreasing trend. The lengths of the first acoustic metamaterial cell to the nth acoustic metamaterial cell arranged in sequence along the axial direction of the main air passage can also be designed to vary randomly and irregularly along the axial direction of the main air passage.

Those skilled in the art can adjust the number and position of the first baffles in the first acoustic cavity in each acoustic metamaterial cell in the metamaterial ventilation and noise reduction muffler as required, and adjust the size of each acoustic opening in the first acoustic cavity. The size of the opening angle. The number and position of the first baffles in the first acoustic cavity in each acoustic metamaterial cell, the position of each acoustic opening and the opening angle may be the same or different from each other. As in a preferred embodiment of the present invention, the acoustic opening angle of the first acoustic cavity in the first acoustic metamaterial cell to the nth acoustic metamaterial cell arranged in sequence along the axial direction of the main air duct The size is increasing, decreasing, or changing randomly.

Those skilled in the art can adjust the size and number of micro-perforations on the perforated plate in each acoustic metamaterial cell in the metamaterial ventilation and noise reduction muffler as required. The size and number of micro-perforations on the perforated plate in each acoustic metamaterial cell can be the same or different from each other. For example, in a preferred embodiment of the present invention, in the second acoustic cavity in the first acoustic metamaterial cell to the nth acoustic metamaterial cell arranged in sequence along the axial direction of the main air channel, the perforated plate has microscopic The size of the perforations and the number of microperforations increased, decreased or changed randomly.

Referring to FIG. 7 , in another embodiment of the present invention, a metamaterial ventilation and noise reduction pipeline cell 15 is provided, including a left connecting pipe 16 , a right connecting pipe 17 and any of the above-mentioned embodiments. Acoustic metamaterial cell 1, the first acoustic cell 1a in the acoustic metamaterial cell 1 is connected to the left connecting pipe 16 and the main air passage of the first acoustic cavity is connected to the left connecting pipe 16, and the acoustic ultra The second acoustic cell 1b in the material cell 1 is connected with the right connecting pipe 17 and the main air passage of the second acoustic cavity is connected with the right connecting pipe 17 .

8 , in another embodiment of the present invention, a metamaterial ventilation and noise reduction pipeline 14 is provided, including m acoustic metamaterial cells 1 described in any of the above embodiments, m acoustic metamaterials The cells 1 are connected in series by connecting pipes, the right connecting pipe 17 of the jth acoustic metamaterial cell 1 is connected with the left connecting pipe 16 of the j+1th acoustic metamaterial cell 1, j=1, 2..., m.

In the metamaterial ventilation and noise reduction pipeline 14 provided by the embodiment shown in FIG. 8 and FIG. 9 , the first acoustic cavity 1a and the second acoustic cavity in each acoustic metamaterial cell 1 in the metamaterial ventilation and noise reduction pipeline The lengths of the body 1b along the axial direction of the main air channel 2 are all the same, and the spacing between adjacent acoustic metamaterial cells 1 is the same. It can be understood that the embodiments shown in FIG. 8 and FIG. 9 are all preferred embodiments of the present invention. In practical applications, those skilled in the art can adjust each acoustic metamaterial cell 1 in the metamaterial ventilation and noise reduction pipeline as required. The lengths of the first acoustic cavity 1a and the second acoustic cavity 1b along the axial direction of the main ventilation channel 2 and the distance between adjacent acoustic metamaterial cells 1, and then adjust the ventilation and noise reduction pipeline elements of each metamaterial The length of the cell 15 along the axial direction of the main air passage, such as the first acoustic cavity 1a or/and the second acoustic cavity 1b in each acoustic metamaterial cell 1 in the metamaterial ventilation and noise reduction pipeline along the main air passage 2 The length in the axial direction is increasing, decreasing or changing randomly and irregularly. The spacing between adjacent acoustic metamaterial cells 1 in each acoustic metamaterial cell 1 in the metamaterial ventilation and noise reduction pipeline is designed to be different, for example, in each acoustic metamaterial cell 1 in the metamaterial ventilation and noise reduction pipeline The spacing between adjacent acoustic metamaterial cells 1 increases, decreases or randomly changes randomly along the axial direction of the main air channel.

Those skilled in the art can adjust the number and position of the first baffles in the first acoustic cavity in each acoustic metamaterial cell 1 in the metamaterial ventilation and noise reduction pipeline 14 as required, and adjust the number and position of the first partitions in the first acoustic cavity. The size of the opening angle of the acoustic opening. The number and position of the first baffles in the first acoustic cavity in each acoustic metamaterial cell, the position of each acoustic opening and the opening angle may be the same or different from each other. As in a preferred embodiment of the present invention, the acoustic opening angle of the first acoustic cavity in the first acoustic metamaterial cell to the nth acoustic metamaterial cell arranged in sequence along the axial direction of the main air duct The size is increasing, decreasing, or changing randomly.

Those skilled in the art can adjust the size and number of micro-perforations on the perforated plate in each acoustic metamaterial cell 1 in the metamaterial ventilation and noise reduction pipeline 14 as required. The size and number of micro-perforations on the perforated plate in each acoustic metamaterial cell can be the same or different from each other. For example, in a preferred embodiment of the present invention, in the second acoustic cavity in the first acoustic metamaterial cell to the nth acoustic metamaterial cell arranged in sequence along the axial direction of the main air channel, the perforated plate has microscopic The size of the perforations and the number of microperforations increased, decreased or changed randomly.

The transmission losses of the first acoustic cell and the second acoustic cell are superimposed on each other, and the coupling between different resonance peaks of the first acoustic cell is enhanced. A number of acoustic metamaterial cells are compactly arranged in the pipeline without space to form a metamaterial ventilation noise reduction muffler. However, arranging the acoustic metamaterial cells in the pipeline at regular intervals can constitute a metamaterial ventilation and noise reduction pipeline. By arranging the acoustic metamaterial cells periodically in the pipeline, the coupling effect between the resonance peaks of the first acoustic cell is enhanced under the action of the high-porosity energy-absorbing medium in the second acoustic cell, and finally a low-frequency broadband can be formed. noise reduction effect. The metamaterial ventilation and noise reduction pipeline can not only better couple different resonance peaks, but also further widen the anechoic frequency band by further utilizing the band gap characteristic of the periodic pipeline. The metamaterial ventilation and noise reduction muffler and the metamaterial ventilation and noise reduction pipeline can adjust the internal structural parameters of the acoustic metamaterial cell and the arrangement in the pipeline without changing the external volume of a single acoustic metamaterial cell. It can achieve the goal of pipeline noise reduction in different frequency bands, and overcome many shortcomings such as narrow noise reduction frequency band, large external space occupation, and poor environmental adaptability of traditional mufflers.

In an embodiment of the present invention, a metamaterial ventilation noise reduction muffler 11 having a structure as shown in FIG. 6 is provided. Among them, the cross-sectional shapes of the main air passage 2, the inlet pipe 12, and the outlet pipe 13 of the acoustic metamaterial cell are selected as circular, and the inner diameters of the main air passage 2, the inlet pipe 12, and the outlet pipe 13 are all 100 mm. The inner diameters of the first acoustic cavity 3 and the second acoustic cavity 6 are the same as the main air passage, which is 100 mm. The diameters of the outer cavity walls of the first acoustic cavity 3 and the second acoustic cavity 6 are the same, and both are 200 mm. There is one acoustic opening 3 in each second acoustic cavity 6, and its corresponding opening angle is 60 degrees. No partition is set in the first acoustic cavity. The first acoustic cell 1a and the second acoustic cell The thickness of the intermediate partitions 9 between 1b is 2 mm. The perforated plate 8 opened as micro-perforation occupies half of the inner cavity wall of the second acoustic cavity 6, the aperture of the micro-perforation on the perforated plate 8 is 2 mm, the thickness of the perforated plate 8 is 1.5 mm, the perforation rate is 0.1, and the second acoustic cavity 6 no longer set any partitions. The second acoustic cavity is completely filled with a high-porosity energy-absorbing medium, and the high-porosity energy-absorbing medium is selected from a foam material. The lengths of the first acoustic cell 1a and the second acoustic cell 1b in the axial direction of the main air channel are the same, and both are 25 mm. The total length of a single acoustic metamaterial cell 1 is 56 mm, and 6 acoustic metamaterial cells 1 are periodically arranged along the axial direction of the main air duct. The acoustic metamaterial cells 1 are compactly arranged without interval, and the internal structural parameters are consistent. The material of each cavity wall of the first acoustic cavity 3 and the second acoustic cavity 6 is made of steel with a wall thickness of 2 mm, which can be regarded as a hard boundary of the sound field, and the influence of sound-structure coupling is not considered. For the metamaterial ventilation noise reduction muffler 11 provided in this embodiment, a plane wave excitation signal is applied to the inlet pipe end, and the outlet pipe end is set as a non-reflection end, and its transmission loss is calculated, and the calculation result is shown in FIG. 10 . It can be seen that, compared with the expansion cavity muffler with the same expansion ratio, the metamaterial muffler can achieve a noise reduction effect of more than 10dB within 345Hz-1080Hz, especially at the resonance frequency of 370Hz, the transmission loss reaches 55.5dB.

In an embodiment of the present invention, a metamaterial ventilation and noise reduction pipeline 14 with a structure as shown in FIG. 9 is provided, wherein the cross-sectional shapes of the main ventilation channel 2, the inlet pipe 12 and the outlet pipe 13 of the acoustic metamaterial cell are selected It is circular, and the inner diameters of the main ventilation duct 2, the inlet pipe 12, and the outlet pipe 13 are all 100 mm. The inner diameters of the first acoustic cavity 3 and the second acoustic cavity 6 are the same as the main air passage, which is 100 mm. The diameters of the outer cavity walls of the first acoustic cavity 3 and the second acoustic cavity 6 are the same, and both are 200 mm. There is one acoustic opening 3 in each second acoustic cavity 6, and its corresponding opening angle is 60 degrees. No partition is set in the first acoustic cavity. The first acoustic cell 1a and the second acoustic cell The thickness of the intermediate partitions 9 between 1b is 2 mm. The perforated plate 8 opened as micro-perforation occupies half of the inner cavity wall of the second acoustic cavity 6, the aperture of the micro-perforation on the perforated plate 8 is 2 mm, the thickness of the perforated plate 8 is 1.5 mm, the perforation rate is 0.1, and the second acoustic cavity 6 no longer set any partitions. The second acoustic cavity is completely filled with a high-porosity energy-absorbing medium, and the high-porosity energy-absorbing medium is selected from a foam material. The lengths of the first acoustic cell 1a and the second acoustic cell 1b in the axial direction of the main air channel 2 are the same as 25 mm, and the total length of a single acoustic metamaterial cell is 56 mm. The acoustic metamaterial cell, the left connecting pipe 16 and the right connecting pipe 17 together form a metamaterial ventilation and noise reduction pipeline cell, wherein the inner diameter and wall thickness of the left and right connecting pipes are the same as those of the main ventilation duct, and the lengths are 100mm. Six metamaterial ventilation and noise reduction pipeline cells are periodically arranged along the axial direction of the main air duct. The structural parameters of the six metamaterial ventilation and noise reduction pipeline cells are consistent. The overall structural material is selected as steel, with a wall thickness of 2mm. It can be regarded as a hard boundary of the sound field, and the influence of sound-structure coupling is not considered. For the metamaterial ventilation and noise reduction pipeline provided in this embodiment, a plane wave excitation signal is applied to the inlet pipe end, and the outlet pipe end is set as a non-reflection end, and its transmission loss is calculated, and the calculation result is shown in Figure 11. It can be seen that, compared with the expansion cavity pipeline with the same expansion ratio, the designed metamaterial pipeline can reflect the broadband noise reduction characteristics, and can achieve a noise reduction effect of more than 10dB at 305Hz-1080Hz. Affected by the local resonance characteristics, after the transmission loss at the resonance peak is superimposed, the amplitude has been greatly improved, and can reach more than 150dB.

The results show that the utility model can achieve a better noise reduction effect in a wider frequency band, and compared with the traditional expansion muffler, the muffler bandwidth and muffler amplitude are significantly improved.

All features disclosed in this specification, or all disclosed steps in a method or process, may be combined in any way except mutually exclusive features and/or steps. Any feature disclosed in this specification (including any accompanying claims, abstract and drawings), unless expressly stated otherwise, may be replaced by other equivalent or alternative features serving a similar purpose. That is, unless expressly stated otherwise, each feature is but one example of a series of equivalent or similar features. For example, in the embodiment of the present invention, the shape of the inlet pipe, the outlet pipe and the cavity is circular, but obviously it can be replaced with a square, a rhombus, a triangle, a pentagon, a hexagon, and the like.

The above are only the preferred embodiments of the present utility model, and the protection scope of the present utility model is not limited to the above-mentioned embodiments, and all technical solutions under the idea of the present utility model belong to the protection scope of the present utility model. It should be pointed out that for those skilled in the art, some improvements and modifications without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims (15)

1. The acoustic metamaterial cellular is characterized by comprising an inner cylinder and an outer cylinder, wherein the inner cylinder is arranged in the outer cylinder, the two cylinders are coaxial, and the inner space of the inner cylinder is a main air duct;

the left side and the right side of the inner cylinder and the outer cylinder are respectively sealed by an annular left side cover plate and an annular right side cover plate, and an annular middle partition plate is arranged between the inner cylinder and the outer cylinder to divide a cavity between the inner cylinder and the outer cylinder into a first acoustic cavity and a second acoustic cavity;

an acoustic opening is formed in the cavity wall between the first acoustic cavity and the main air duct, and the first acoustic cavity and the cavity walls which enclose the first acoustic cavity form a first acoustic cellular; the first acoustic cavity is communicated with the main air duct through an acoustic opening;

the high-porosity energy-absorbing medium is filled in the second acoustic cavity, a perforated plate provided with micro-perforations is arranged on the cavity wall between the second acoustic cavity and the main ventilation duct, the high-porosity energy-absorbing medium filled in the second acoustic cavity and the cavity walls enclosing to form the second acoustic cavity form a second acoustic cell, and the second acoustic cavity is communicated with the main ventilation duct through the micro-perforations on the perforated plate.

2. The acoustic metamaterial unit cell of claim 1, wherein the cross-sectional shape of the inner cylinder and the outer cylinder is circular, elliptical, or polygonal.

3. The acoustic metamaterial unit cell of claim 2, wherein the high porosity energy absorbing medium is a porous material with a porosity greater than 90%.

4. The acoustic metamaterial unit cell of claim 3, wherein the high-porosity energy absorbing medium is an organic porous material, a metal porous material, or a ceramic porous material.

5. The acoustic metamaterial unit cell of any one of claims 2 to 4, wherein the acoustic waves enter from an acoustic opening between the main air duct and the first acoustic cavity and form a resonant cavity with the first acoustic cavity; the sound waves enter from the perforated plate between the main ventilation channel and the second acoustic cavity and form a sound absorption cavity together with the high-porosity energy absorption medium in the second acoustic cavity.

6. The acoustic metamaterial unit cell of claim 5, wherein N first partition plates are disposed in the first acoustic cavity, the N first partition plates divide the first acoustic cavity into N +1 first acoustic small cavities, an acoustic opening is disposed between each first acoustic small cavity and the main air duct, the N +1 first acoustic small cavities are respectively communicated with the main air duct through corresponding acoustic openings, and N is zero or a positive integer.

7. The acoustic metamaterial unit cell of claim 5, wherein M second partitions are disposed in the second acoustic cavity, the M second partitions divide the second acoustic cavity into M +1 second acoustic chambers, sidewalls between each second acoustic chamber and the main air duct are perforated plates, micro-perforations are formed in the perforated plates, the M +1 second acoustic chambers are respectively communicated with the main air duct through the corresponding micro-perforations, and M is zero or a positive integer.

8. The acoustic metamaterial unit cell of claim 6, wherein a plurality of third partitions are disposed in each first acoustic chamber, the plurality of third partitions dividing each first acoustic chamber into coiled labyrinth chambers by alternating spacing.

9. The acoustic metamaterial unit cell of claim 7, wherein a plurality of fourth partitions are disposed in each second acoustic chamber, and the plurality of fourth partitions divide each second acoustic chamber into curly labyrinth chambers by being alternately disposed.

10. A metamaterial ventilation noise reduction muffler characterized by comprising an inlet pipe, an outlet pipe and n acoustic metamaterial cells as claimed in claim 1,2, 3, 4, 6, 7, 8 or 9 coaxially and closely connected in series, wherein the second acoustic cavity of the ith acoustic metamaterial cell is closely connected with the first acoustic cavity of the (i + 1) th acoustic metamaterial cell, i is 1,2, n is a positive integer greater than or equal to 2, and the main ventilation ducts of the n acoustic metamaterial cells are communicated with each other;

the main ventilation channel of the first acoustic cavity of the 1 st acoustic metamaterial unit cell is connected with and communicated with the inlet pipe, and the main ventilation channel of the second acoustic cavity of the nth acoustic metamaterial unit cell is connected with and communicated with the outlet pipe.

11. The metamaterial ventilation noise reduction muffler of claim 10, wherein the n acoustic metamaterial cells have the same length in the axial direction of the main ventilation duct;

or the lengths of the 1 st acoustic metamaterial unit cell to the nth acoustic metamaterial unit cell which are sequentially arranged along the axial direction of the main ventilation duct are increased, decreased or irregularly changed randomly along the axial direction of the main ventilation duct.

12. The metamaterial ventilation noise reduction muffler of claim 10, wherein the acoustic opening angles of the first acoustic cavities in the n acoustic metamaterial cells are the same;

or the sizes of the acoustic opening angles of the first acoustic cavities in the 1 st to the nth acoustic metamaterial cells which are sequentially arranged along the axial direction of the main ventilation duct are increased progressively, decreased progressively or irregularly and randomly changed.

13. The metamaterial ventilation noise reduction muffler according to claim 10, wherein the sizes of the micro-perforations on the perforated plate of the second acoustic cavity in the n acoustic metamaterial units are the same;

or the sizes of the micro-perforations on the perforated plate of the second acoustic cavity in the 1 st to the nth acoustic metamaterial cells sequentially arranged along the axial direction of the main ventilation duct are increased progressively, decreased progressively or randomly changed irregularly.

14. The metamaterial ventilation noise reduction duct unit cell, which is characterized by comprising a left side connecting pipe, a right side connecting pipe and the acoustic metamaterial unit cell as claimed in claim 1,2, 3, 4, 6, 7, 8 or 9, wherein a first acoustic unit cell in the acoustic metamaterial unit cell is connected with the left side connecting pipe, a main ventilation duct of a first acoustic cavity is communicated with the left side connecting pipe, a second acoustic unit cell in the acoustic metamaterial unit cell is connected with the right side connecting pipe, and a main ventilation duct of a second acoustic cavity is communicated with the right side connecting pipe.

15. The metamaterial ventilation noise reduction pipeline is characterized by comprising m acoustical metamaterial unit cells as claimed in claim 1,2, 3, 4, 6, 7, 8 or 9, wherein the m acoustical metamaterial unit cells are connected in series through connecting pipes, the right connecting pipe of the jth acoustical metamaterial unit cell is communicated with the left connecting pipe of the jth +1 th acoustical metamaterial unit cell, and j is 1,2.

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