CN217847433U - Metamaterial unit for low-frequency broadband efficient sound absorption and superstructure module thereof - Google Patents

Abstract

The utility model discloses a metamaterial unit and superstructure module for high-efficient sound absorption of low frequency broadband, metamaterial unit includes that polylith leg encloses the metamaterial cavity and the setting that closes and form and is in acoustics guided wave passageway in the metamaterial cavity is provided with the high-efficient modulation sound absorber of impedance in the acoustics guided wave passageway, and the high-efficient modulation sound absorber of impedance includes high porosity sound absorbing medium and impedance modulation passageway. The introduction of the impedance modulation channel can effectively change the acoustic characteristics of the high-porosity sound absorption medium, and the acoustic impedance can be modulated in a wide frequency band and a resonance absorption peak is generated at a low frequency band by changing the geometric configuration of the impedance modulation channel, so that the sound absorption performance of the low frequency band is obviously improved. A plurality of metamaterial units with different low-frequency high-efficiency absorption properties are connected in parallel, and a metamaterial module with low-frequency broadband high-efficiency sound absorption and noise reduction properties can be formed through the coupling effect between the metamaterial units, so that the low-frequency broadband high-efficiency sound absorption properties are realized.

Description

Metamaterial unit for low-frequency broadband efficient sound absorption and superstructure module thereof

Technical Field

The invention belongs to the field of new materials and new technologies for noise treatment, and particularly relates to a metamaterial unit for low-frequency broadband efficient sound absorption and a superstructure module thereof, which can be applied to acoustic control of modern transportation vehicles (high-speed rails, airplanes, ships and new energy automobiles), novel functional stadiums/rooms (conference stadiums, waiting hall pipes, recording/broadcasting halls, anechoic rooms and wind tunnels) and the like.

Background

In the field of noise control, materials or structures having sound absorption and noise reduction functions can be classified into two categories, i.e., porous sound absorption materials and resonance sound absorption structures according to a sound absorption principle, wherein common porous sound absorption materials include organic fiber type porous materials, inorganic fiber type porous materials, foam type porous materials, metal type porous materials and the like, and common resonance sound absorption structures include film type resonance sound absorption structures, perforated plate (including microperforated plates) type resonance sound absorption structures, slit type resonance sound absorption structures and the like.

In engineering, the traditional porous material type sound absorption material has good sound absorption effect on sound waves of medium and high frequency bands above 1000Hz, is widely applied in practical engineering, but has poor sound absorption effect on sound waves of low frequency bands (below 1000 Hz). The sound absorption mechanism of the porous material mainly comprises the following steps: air viscosity; heat exchange in the medium. The Johnson-Champoux-allred equivalent model is currently used more widely to describe porous materials, which defines five macroscopic parameters of the porous material: porosity, flow resistance, tortuosity, viscous characteristic length, and thermal characteristic length. These five macroscopic parameters can adjust the acoustic impedance by changing the equivalent bulk modulus and density of the porous material, which can affect the overall sound absorption performance of the porous material. Considering the actual preparation process of the porous material, in the processable preparation range, the adjustment range of the five macroscopic parameters to the acoustic impedance is very limited, so that the wide-band large-scale adjustment of the acoustic impedance is difficult to realize, and meanwhile, the high-efficiency sound absorption is difficult to realize in the low frequency band. In addition, the optimal sound absorption frequency of the porous material mainly depends on the thickness of the whole porous material, and the optimal sound absorption frequency moves by one octave towards the low-frequency direction every time the thickness is increased by 1 time. Therefore, the traditional porous material is used for improving the sound absorption performance of the low frequency band, the thickness of the porous material is often required to be greatly increased, the space size and the manufacturing cost of the porous sound absorption material are greatly increased, and the requirements of practical engineering application are not met.

In order to solve the problem of sound absorption of low frequency band, the prior art needs to adopt a resonance sound absorption structure. As for the film type resonance sound absorption structure, research results show that the maximum sound absorption coefficient of the film type resonance sound absorption structure is generally not more than 0.5 under the condition of no back cavity, the sound absorption coefficient of the film type resonance sound absorption structure can be improved through coherent absorption of a multilayer film structure or hybrid resonance of the film structure and a cavity, and sound wave perfect absorption at low frequency is realized. Therefore, for the film type resonance sound absorption structure, the whole thickness of the structure is often too large to realize the high-efficiency sound absorption of the low frequency band. For a perforated plate (containing a micro-perforated plate) type resonance sound absorption structure and a micro-slit type resonance sound absorption structure, the thickness of a back cavity is also obviously increased to improve the sound absorption performance of a low frequency band. Therefore, the resonant sound absorption frequency band of the existing resonant sound absorption structure generally depends on the thickness of the entire structure. In order to realize the low-frequency efficient absorption of sound waves, the thickness of the resonance sound absorption structure is often required to be increased, the space size and the manufacturing cost of the resonance sound absorption structure are greatly increased, the resonance sound absorption structure is not suitable for occasions with low-frequency noise reduction requirements and limited space, and the larger manufacturing cost does not meet the requirements of practical engineering application. In addition, the traditional resonance sound absorption structure has better sound absorption performance only near the designed resonance frequency, and the sound absorption performance is sharply reduced when the resonance frequency deviates from the designed resonance frequency, so that the high-efficiency sound absorption bandwidth is very narrow, and the low-frequency broadband sound absorption requirement in the actual engineering cannot be met. In the existing research, according to the resonance coupling effect, a sufficient number of resonance sound absorption structures with different absorption frequencies are connected in parallel, so that the purpose of effectively widening the sound absorption bandwidth is achieved, but as the sound absorption bandwidth is widened, the sound absorption coefficient is also reduced, and the low-frequency broadband efficient sound absorption is difficult to realize. In a word, the existing resonance sound absorption structure is difficult to realize perfect unification of low frequency, broadband and high-efficiency sound absorption.

In summary, in engineering applications, due to the limitations of structural space size, manufacturing process, cost, etc., the existing sound-absorbing materials and structures are difficult to realize the low-frequency broadband efficient absorption of sound waves. The invention discloses a method for realizing low-frequency broadband high-efficiency sound absorption and noise reduction by adopting a metamaterial unit and a superstructure module based on the metamaterial unit, wherein the metamaterial unit is formed by introducing an impedance high-efficiency modulation sound absorber comprising a high-porosity sound absorption medium and an impedance modulation channel into an acoustic guided wave channel.

Disclosure of Invention

Aiming at the defects and shortcomings in the prior art, the invention aims to provide a metamaterial unit for low-frequency broadband efficient sound absorption and noise reduction and a superstructure module thereof.

In order to achieve the technical purpose, the invention adopts the technical scheme that:

on one hand, the invention provides a metamaterial unit for low-frequency broadband efficient sound absorption, which comprises a metamaterial cavity formed by enclosing a plurality of surrounding walls and an acoustic guided wave channel arranged in the metamaterial cavity, wherein an impedance efficient modulation sound absorber is arranged in the acoustic guided wave channel.

Furthermore, the metamaterial unit provided by the invention can further comprise a sound wave high-transmittance cover plate, the sound wave high-transmittance cover plate is arranged on the metamaterial cavity, and an acoustic wave guide channel in the metamaterial cavity is communicated with the outside through an opening or a slit on the sound wave high-transmittance cover plate.

Furthermore, the impedance efficient modulation sound absorber comprises a high-porosity sound absorption medium and an impedance modulation channel, wherein the high-porosity sound absorption medium covers the inner side wall of the acoustic wave guide channel, and more than one impedance modulation channel is arranged in the high-porosity sound absorption medium.

Furthermore, the axial direction of the impedance modulation channel is consistent with the wave guiding direction of the acoustic wave guiding channel.

Furthermore, the invention can realize the wide-band and large-amplitude modulation of acoustic impedance by changing the geometric configuration of the impedance modulation channel, and simultaneously generates resonance absorption peak in the low frequency band, thereby improving the sound absorption performance of the low frequency band.

Furthermore, the cross section of the impedance modulation channel in the direction parallel to the wave guiding direction of the acoustic wave guiding channel is rectangular, conical, trapezoidal, rhombic or regular polygon of axial symmetry type.

Furthermore, the acoustic wave guide channel is a linear channel or a zigzag channel, and the width of the acoustic wave guide channel is equal in width or gradually changed or gradiently changed along the wave guide direction of the acoustic wave guide channel.

Furthermore, the high-porosity sound absorption medium is filled in the whole acoustic wave guide channel; or the high porosity sound absorbing medium fills part of the length of the acoustic waveguide channel from the bottom of the acoustic waveguide channel.

Furthermore, the metamaterial cavity is made of metal plates, plastic plates, hard fiber boards, plywood, gypsum boards, resin boards or toughened glass boards.

Furthermore, the metamaterial cavity is formed by riveting, welding or gluing, or the metamaterial cavity is integrally formed by casting or additive machining.

Further, the high-porosity sound absorption medium is an organic fiber type porous material, an inorganic fiber type porous material, a foam type porous material or a metal type porous material.

In another aspect, the invention provides a superstructure module, which comprises a plurality of metamaterial units for low-frequency broadband high-efficiency sound absorption, wherein each metamaterial unit is connected in parallel.

Further, in the superstructure module, the metamaterial units are periodically arranged in one dimension or two dimensions.

The invention can produce the following beneficial technical effects:

the invention provides a metamaterial unit for low-frequency broadband efficient sound absorption and a superstructure module thereof, which have simpler and more reasonable structures.

According to the invention, the impedance high-efficiency modulation sound absorber is introduced into the acoustic wave guide channel and comprises the high-porosity sound absorption medium and the impedance modulation channel, so that the metamaterial unit for low-frequency broadband high-efficiency sound absorption and the superstructure module thereof with simpler and more reasonable structure are designed.

Specifically, the impedance high-efficiency modulation sound absorber is introduced into the acoustic wave guide channel, and due to the coupling resonance effect of the impedance high-efficiency modulation sound absorber in the low frequency band, a high-efficiency resonance absorption peak can be generated in the low frequency band, so that the sound absorption performance of the low frequency band is improved, and the high-efficiency sound absorption performance of the medium and high frequency bands is well maintained. The modulation range is very limited by only using the high porosity sound absorption medium to modulate the acoustic impedance under the condition of fully considering the practical preparation process. Furthermore, the impedance modulation channel is introduced into the high-porosity sound absorption medium to form the impedance high-efficiency modulation sound absorber, and due to the introduction of the impedance modulation channel, the acoustic impedance can be modulated in a wide frequency range and a large amplitude range only by changing the geometric configuration of the impedance modulation channel on the premise of not changing the material parameters of the high-porosity sound absorption medium, so that the sound absorption performance of a low frequency range is remarkably improved under the condition of not increasing the thickness of the high-porosity sound absorption medium, and meanwhile, the high-efficiency sound absorption performance of a medium and a high frequency range is well maintained.

Furthermore, the invention utilizes the zigzag arrangement of the acoustic wave guide channels, obviously increases the equivalent path of sound wave propagation under the condition of keeping the whole thickness dimension of the structure unchanged to a certain extent, and improves the sound absorption performance of a low frequency band to a certain extent.

Furthermore, by designing the geometric configuration of the impedance modulation channel in the metamaterial unit, the metamaterial unit with different low-frequency high-efficiency absorption properties can be obtained. The super-material units with different low-frequency high-efficiency absorption properties are connected in parallel to form a super-structure module, and the super-structure module can realize high-efficiency absorption of low-frequency-band sound waves and can also absorb sound at a medium and high frequency band through coupling and superposition of the super-material units, so that low-frequency broadband high-efficiency absorption of the sound waves can be realized.

In conclusion, the sound absorption structure has the advantages of good low-frequency, broadband and high-efficiency sound absorption performance, simple structure, easiness in processing and manufacturing, low cost and the like.

Drawings

FIG. 1 is a schematic structural diagram of an embodiment of the present invention;

FIG. 2 is a schematic structural view of an acoustic waveguide according to an embodiment of the present invention;

FIG. 3 is a cross-sectional view of one embodiment of the present invention;

FIG. 4 is a schematic structural diagram of a metamaterial unit according to an embodiment of the present invention;

FIG. 5 is a schematic structural diagram of a metamaterial unit according to an embodiment of the present invention;

FIG. 6 is a schematic structural diagram of a metamaterial unit according to an embodiment of the present invention;

FIG. 7 is a schematic structural diagram of a metamaterial unit according to an embodiment of the present invention;

FIG. 8 is a schematic structural view of an acoustic waveguide channel in accordance with an embodiment of the present invention;

FIG. 9 is a schematic structural view of an acoustic waveguide channel in accordance with an embodiment of the invention;

FIG. 10 is a schematic structural view of an acoustic waveguide channel in accordance with an embodiment of the invention;

FIG. 11 is a schematic representation of a filled form of a high porosity sound absorbing medium in accordance with an embodiment of the present invention;

FIG. 12 is a schematic representation of a filled form of a high porosity sound absorbing medium in accordance with an embodiment of the present invention;

FIG. 13 is a schematic structural diagram of an embodiment of the present invention (cover plate with acoustic wave high transmittance);

FIG. 14 is a schematic structural diagram (with acoustic high transmittance cover plate) according to an embodiment of the present invention;

FIG. 15 is a schematic view of an embodiment of the present invention (with acoustic wave high transmittance cover plate);

FIG. 16 is a schematic structural view of an embodiment of the present invention (without the acoustic high transmittance cover);

FIG. 17 is a cross-sectional view of one embodiment of the present invention;

FIG. 18 is a cross-sectional view of one embodiment of the present invention;

FIG. 19 is a cross-sectional view of an embodiment of the present invention;

fig. 20 is a schematic structural diagram (one-dimensional periodic arrangement) of a superstructure module provided by an embodiment of the present invention;

fig. 21 is a schematic structural diagram (two-dimensional periodic arrangement) of a superstructure module provided by an embodiment of the present invention;

fig. 22 is a schematic structural diagram of a superstructure module provided by an embodiment of the present invention;

FIG. 23 is a graph of sound absorption coefficient for a superstructure module provided by an embodiment of the present invention;

fig. 24 is a schematic structural diagram of a superstructure module provided by an embodiment of the present invention;

FIG. 25 is a graph of sound absorption coefficient for a superstructure module provided by an embodiment of the present invention;

reference numbers in the figures:

1. an acoustic wave guide channel; 1.1, the inner side wall of the acoustic wave guide channel; 2. a metamaterial cavity; 2.1, surrounding walls; 3. impedance high-efficiency modulation sound absorber; 3a, a high-porosity sound absorption medium; 3b, an impedance modulation channel; 4. a sound wave high transmittance cover plate; 4.1, opening holes.

The objects, features and advantages of the present invention will be further explained with reference to the accompanying drawings.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that all directional indicators (such as up, down, left, right, front, and back \8230;) in the embodiments of the present invention are only used to explain the relative positional relationship between the components, the motion situation, etc. in a specific posture (as shown in the attached drawings), and if the specific posture is changed, the directional indicators are changed accordingly.

In addition, the descriptions related to "first", "second", etc. in the present invention are only for descriptive purposes and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless explicitly specified otherwise.

In the present invention, unless otherwise explicitly stated or limited, the terms "connected", "fixed", and the like are to be understood broadly, for example, "fixed" may be fixedly connected, may be detachably connected, or may be integrated; the connection can be mechanical connection, electrical connection, physical connection or wireless communication connection; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In addition, the technical solutions in the embodiments of the present invention may be combined with each other, but it must be based on the realization of those skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination of technical solutions should not be considered to exist, and is not within the protection scope of the present invention.

As shown in fig. 1, a superstructure module for low-frequency broadband high-efficiency sound absorption provided in an embodiment is formed by connecting three different metamaterial units in parallel, and includes a metamaterial cavity 2 surrounded by a plurality of surrounding walls 2.1 and three acoustic waveguide channels 1 disposed in the metamaterial cavity 2, wherein an impedance high-efficiency modulation sound absorber is disposed in the acoustic waveguide channel 1. In fig. 1, the metamaterial cavity 2 is a cuboid, and an acoustic high-transmittance cover plate 4 is arranged on the metamaterial cavity 2, and each acoustic waveguide channel 1 in the metamaterial cavity 2 is communicated with the outside through an opening 4.1 in the acoustic high-transmittance cover plate 4. The specific shape of the opening of the acoustic high-transmittance cover plate 4 is not limited, and may be rectangular, circular, triangular, rhombic, or polygonal. In fig. 1, the opening 4.1 on the acoustic wave high-transmittance cover plate 4 is a rectangular opening, and three rectangular openings on the acoustic wave high-transmittance cover plate 4 correspond to three acoustic wave guide channels 1 in the metamaterial cavity 2 respectively.

In some embodiments using the structure shown in fig. 1, the enclosure walls are made of acoustic high-reflectivity board, which may be metal, plastic, hardboard, plywood, gypsum board, synthetic resin board, or toughened glass board. Similarly, the inner side wall 1.1 of the acoustic wave guide channel is made of a sound wave high-reflectivity plate structure, and can be a metal plate, a plastic plate, a hard fiber plate, a plywood, a gypsum board, a synthetic resin plate or a toughened glass plate. The acoustic high-transmittance cover plate 4 is made of an acoustic high-reflectance plate structure, and can be a metal plate, a plastic plate, a hard fiber plate, a plywood, a gypsum board, a synthetic resin plate or a toughened glass plate. When the enclosure wall and the acoustic wave high-transmittance cover plate are high-rigidity plates such as a tempered glass plate and a metal plate, the metamaterial unit has good bearing capacity.

In some embodiments, the surrounding walls, the inner side wall 1.1 of each acoustic waveguide channel and the acoustic high-transmittance cover plate can be separately and independently manufactured and then connected to form a whole by riveting, welding, gluing or the like. Therefore, the acoustic wave guide channels with different geometric configurations can be conveniently adjusted and assembled according to needs.

In some embodiments, the surrounding walls, the inner side wall 1.1 of the acoustic waveguide channel and the acoustic high-transmittance cover plate can also be integrally formed by casting, 3D printing or additive machining. The integrity of the product can be guaranteed through integrated molding, and the metamaterial unit has good bearing capacity.

The shape of the acoustic waveguide channel 1 in the present invention is not limited. The acoustic wave guide channel 1 can be a straight channel or a zigzag channel such as an L-shaped zigzag channel. The zigzag channel can remarkably prolong the propagation path of sound waves under the condition of keeping the whole thickness unchanged, so that the sound absorption frequency band of the zigzag channel moves to low frequency. The width setting mode of acoustics guided wave passageway 1 is not limited, can follow its guided wave direction isopachous setting, also can be along its guided wave direction and be certain law gradual change, also can be along its guided wave direction and be gradient change. Referring to fig. 2, the acoustic waveguide channel 1 in one embodiment is an L-shaped meandering channel, and the width of the acoustic waveguide channel 1 is set to be equal in width along the waveguide direction.

Referring to fig. 3, in an embodiment, 3 acoustic waveguide channels 1 are disposed in the metamaterial cavity 2, and an impedance efficient modulation sound absorber 3 is disposed in each acoustic waveguide channel 1. The high-efficiency impedance modulation sound absorber 3 comprises a high-porosity sound absorption medium 3a and an impedance modulation channel 3b, wherein the high-porosity sound absorption medium 3a covers the inner side wall 1.1 of the acoustic wave guide channel, and more than one impedance modulation channel 3b is arranged in the high-porosity sound absorption medium 3 a. Specifically, in 3 acoustic guided wave channels 1 in the metamaterial cavity 2, one acoustic guided wave channel 1 is linear, and the other two acoustic guided wave channels 1 are L-shaped zigzag channels. The L-shaped zigzag channel can obviously prolong the propagation path of sound waves under the condition of keeping the whole thickness unchanged, so that the sound absorption frequency band of the L-shaped zigzag channel moves to low frequency. The high-porosity sound absorption medium 3a in the 3 acoustic wave guide channels 1 fills the length of the whole acoustic wave guide channel. The 3 acoustic guided wave channels are respectively provided with an impedance modulation channel 3b, and the axial direction of each impedance modulation channel 3b is consistent with the guided wave direction of the acoustic guided wave channel 1 where the impedance modulation channel is located. In fig. 3, a sound wave high-transmittance cover plate 4 is arranged on the metamaterial cavity 2, 3 rectangular openings 4.1 are formed in the positions, corresponding to the 3 impedance modulation channels 3b, of the sound wave high-transmittance cover plate 4, and the 3 impedance modulation channels 3b are respectively communicated with the outside through the corresponding openings 4.1 in the sound wave high-transmittance cover plate 4.

The cross-sectional shape of the impedance modulation channel 3b in the direction parallel to the wave guiding direction of the acoustic wave guiding channel 1 is not limited in the present invention, and may be rectangular, conical, trapezoidal, rhombic, or other polygonal shapes. The introduction of the impedance modulation channel can effectively change the acoustic characteristics of the high-porosity sound absorption medium, and the acoustic impedance can be modulated in a wide frequency band and a large amplitude by changing the geometric configuration of the impedance modulation channel, and meanwhile, a resonance absorption peak is generated in a low frequency band, so that the sound absorption performance of the low frequency band is obviously improved.

Referring to fig. 4, fig. 4 is a schematic structural diagram of a metamaterial unit in an embodiment of the present invention, including a metamaterial cavity surrounded by a plurality of enclosure walls 2.1, and an acoustic waveguide channel 1 disposed in the metamaterial cavity, where an impedance efficient modulation sound absorber 3 is disposed in the acoustic waveguide channel 1. The acoustic guided wave channel in fig. 4 is an L-shaped acoustic guided wave channel 1, an impedance efficient modulation sound absorber 3 is arranged in the acoustic guided wave channel 1, and the impedance efficient modulation sound absorber 3 completely fills the whole acoustic guided wave channel 1. The high-efficiency impedance modulation sound absorber 3 comprises a high-porosity sound absorption medium 3a and an impedance modulation channel 3b, wherein the high-porosity sound absorption medium 3a covers the inner side wall 1.1 of the acoustic wave guide channel, and more than one impedance modulation channel 3b is arranged in the high-porosity sound absorption medium 3 a. The high-porosity sound absorption medium 3a covers the inner side wall 1.1 of the acoustic wave guide channel. High porosity sound absorbing medium 3a and acoustics guided wave channel inside wall 1.1 between can adopt the glued mode to carry out fixed connection, also can be for carrying out fixed connection through rib, grid or net. High porosity sound absorption medium 3a also can wrap the back fixed connection on acoustics guided wave channel inside wall 1.1 with sound wave high transmissivity wrapping cloth, is guaranteeing like this under the absorptive prerequisite of sound wave transmission, has improved high porosity sound absorption medium's durability simultaneously. An impedance modulation channel 3b is arranged in the high-porosity sound absorption medium 3a, the axial direction of the impedance modulation channel 3b is consistent with the wave guide direction of the acoustic wave guide channel 1 where the impedance modulation channel is located, the cross section of the impedance modulation channel 3b in the wave guide direction parallel to the acoustic wave guide channel 1 is rectangular, acoustic impedance broadband can be greatly modulated by changing the geometric configuration (such as length and width) of the impedance modulation channel 3b, and a resonance absorption peak is generated in a low frequency band, so that the sound absorption performance of the low frequency band is improved.

Referring to fig. 5, fig. 5 is a schematic structural diagram of a metamaterial unit according to an embodiment of the present invention; an impedance efficient modulation sound absorber 3 is arranged in the L-shaped acoustic guided wave channel 1, and the impedance efficient modulation sound absorber 3 completely fills the whole acoustic guided wave channel 1. The high-porosity sound absorption medium 3a is fixed on the inner side wall 1.1 of the acoustic wave guide channel. The difference from the embodiment shown in fig. 4 is that the embodiment shown in fig. 5 is provided with two impedance modulation channels 3b in the high porosity sound absorbing medium 3a, wherein one impedance modulation channel 3b is rectangular, and the other impedance modulation channel 3b is parallel to the L-shaped acoustic wave guiding channel 1 and is in a zigzag shape of L shape. The axial direction of each impedance modulation channel 3b coincides with the wave guiding direction of the acoustic wave guiding channel 1 in which it is located. The wide-band and large-amplitude modulation of acoustic impedance can be realized by changing the geometrical configuration of the impedance modulation channels 3b (such as the length and width of each impedance modulation channel 3b and the distance between adjacent impedance modulation channels 3 b), and meanwhile, resonance absorption peaks are generated in a low frequency band, so that the sound absorption performance of the low frequency band is improved.

Referring to fig. 6, fig. 6 is a schematic structural diagram of a metamaterial unit according to an embodiment of the present invention; an impedance efficient modulation sound absorber 3 is arranged in the L-shaped acoustic guided wave channel 1, and the impedance efficient modulation sound absorber 3 completely fills the whole acoustic guided wave channel 1. The high-porosity sound absorption medium 3a is fixed on the inner side wall 1.1 of the acoustic wave guide channel. A conical impedance modulation channel 3b is arranged in the high-porosity sound absorption medium 3a, namely the cross section of the impedance modulation channel 3b in the wave guiding direction parallel to the acoustic wave guiding channel is conical. The acoustic impedance broadband can be greatly modulated by changing the geometric configuration of the impedance modulation channel 3b (such as the length of the impedance modulation channel 3b, the size of a top channel opening, the included angle of a bottom channel and the like), and a resonance absorption peak is generated in a low frequency band, so that the sound absorption performance of the low frequency band is improved.

Referring to fig. 7, fig. 7 is a schematic structural diagram of a metamaterial unit according to an embodiment of the present invention; an impedance high-efficiency modulation sound absorber 3 is arranged in the L-shaped acoustic guided wave channel 1, and the impedance high-efficiency modulation sound absorber 3 completely fills the whole acoustic guided wave channel 1. The high-porosity sound absorption medium 3a is fixed on the inner side wall 1.1 of the acoustic wave guide channel. An impedance modulation channel 3b which is contracted and then expanded along the waveguide direction of the acoustic waveguide channel is arranged in the high-porosity sound absorption medium 3a, and the cross section of the impedance modulation channel 3b in the waveguide direction parallel to the acoustic waveguide channel is similar to a prism in shape. By changing the geometrical configuration of the impedance modulation channel 3b (such as the length of the impedance modulation channel 3b, the size of a top channel opening, the size of a middle channel part, the size of a bottom channel and the like), the wide-band large-amplitude modulation of the acoustic impedance can be realized, and a resonance absorption peak is generated in a low frequency band, so that the sound absorption performance of the low frequency band is improved.

It is understood that the geometric configuration of the impedance modulation channel 3b of the present invention is not limited to the ones shown in fig. 3, 4, 5, 6 and 7, and those skilled in the art can reasonably design and adjust it.

In the superstructure module of the invention, more than one acoustic guided wave channel 1 is arranged in the metamaterial cavity 2, the arrangement mode of the acoustic guided wave channels 1 is not limited, the shape of each acoustic guided wave channel 1 is not limited, and various forms of acoustic guided wave channel 1 combinations can be adopted.

The shape of the acoustic waveguide channel is not limited, and may be a straight channel or a meandering channel. Referring to fig. 8, 9, and 10, three different types of acoustic waveguide channels, i.e., a straight acoustic waveguide channel, an L-shaped acoustic waveguide channel passing through one turn, and a hook-shaped acoustic waveguide channel passing through two turns, are provided. It is to be understood that the geometric configuration of the acoustic waveguide channel of the present invention is not limited to those shown in fig. 8, 9 and 10, and those skilled in the art can reasonably design and adjust it.

The high-porosity sound absorption medium 3a can be completely filled in the whole acoustic wave guide channel, and can also be filled in the acoustic wave guide channel with partial length from the bottom of the acoustic wave guide channel. Referring to fig. 11, in the embodiment shown in fig. 11, each acoustic waveguide 1 disposed in the metamaterial cavity 2 is filled with a high-porosity sound-absorbing medium 3a along the entire length direction thereof, that is, the high-porosity sound-absorbing medium 3a is completely filled in each acoustic waveguide. Referring to fig. 12, in the embodiment shown in fig. 12, in each acoustic waveguide 1 arranged in the metamaterial cavity 2, the high-porosity sound absorbing medium 3a fills part of the length of the acoustic waveguide from the bottom of the acoustic waveguide. The heights of the high porosity sound absorbing medium 3a filled in the three acoustic waveguide channels in fig. 12 are different from each other.

The metamaterial cavity 2 can be provided with a sound wave high-transmittance cover plate or not. If the metamaterial cavity 2 is provided with the acoustic high-transmittance cover plate 4, the shape and distribution form of the openings or the slits on the acoustic high-transmittance cover plate 4 are not limited. The sound wave high-transmissivity cover plate 4 can be a slotted plate, a full-aperture plate and a half-aperture plate. As shown in fig. 13, 14, and 15, the acoustic high transmittance cover 4 is shown in several different cases. In fig. 13, 3 rectangular openings are formed in the acoustic high transmittance cover plate 4 disposed on the metamaterial cavity 2. In fig. 14, 3 strip-shaped perforated belts are disposed on the acoustic high transmittance cover plate 4 disposed on the metamaterial cavity 2, and each perforated belt is provided with a plurality of round holes or square holes. In fig. 15, the acoustic high-transmittance cover plate 4 disposed on the metamaterial cavity 2 is a full-aperture plate, the apertures on the acoustic high-transmittance cover plate 4 are arranged in a matrix, and the apertures are not limited to be circular or square. Referring to fig. 16, the acoustic high-transmittance cover plate 4 is not disposed on the metamaterial cavity 2 in fig. 16.

Referring to fig. 1 to 19, the number, shape, arrangement and combination of the acoustic waveguide channels 1 disposed in the metamaterial cavity 2 are not limited. When a plurality of acoustic wave guide channels 1 can be arranged in the metamaterial cavity 2, the filling heights of the high-porosity sound absorption media 3a in the acoustic wave guide channels can be the same, partially the same or different from each other, and the high-porosity sound absorption media can be combined randomly. The length, shape and width of each acoustic wave guide channel can be the same, partially the same or different from each other, and any combination thereof. The number, the geometrical configuration and the distribution form of the impedance modulation channels 3b arranged in the high-porosity sound absorption medium 3a in each acoustic wave guide channel can be the same, partially the same or different from each other, and any combination can be adopted. By designing these features differently, metamaterial units with different low-frequency high-efficiency absorption properties can be obtained.

According to the metamaterial unit provided by the invention, the impedance high-efficiency modulation sound absorber is introduced into the acoustic wave guide channel, on one hand, the coupling resonance effect of the metamaterial unit in the low frequency band is utilized, and a high-efficiency resonance absorption peak can be generated in the low frequency band, so that the sound absorption performance of the low frequency band is improved; on the other hand, by changing the geometric configuration of the impedance modulation channel, the wide-band large-amplitude modulation of the acoustic impedance at a low frequency band can be realized, and the sound absorption performance of the low frequency band is obviously improved.

The superstructure module provided by the invention consists of a plurality of metamaterial units for low-frequency broadband efficient sound absorption provided by any one or more of the above embodiments, and all the metamaterial units are connected in parallel.

The metamaterial units employed in the superstructure module may be identical, partially identical, or completely different. Different metamaterial units have different low-frequency high-efficiency absorption properties. The manner of obtaining the metamaterial units with different low-frequency high-efficiency absorption properties is described in detail in the embodiments related to the metamaterial units, and is not described herein again.

In one embodiment, a plurality of metamaterial units with different low-frequency high-efficiency absorption performance are connected in parallel, and a superstructure module with low-frequency broadband high-efficiency sound absorption and noise reduction performance is formed through the coupling effect of the metamaterial units, so that the low-frequency broadband high-efficiency sound absorption performance is realized.

The superstructure module utilizes the wide-frequency large-amplitude modulation of the metamaterial units on the acoustic impedance and the coupling resonance effect of the low frequency of the metamaterial units, can obviously improve the sound absorption performance of low-frequency-band sound waves, keeps excellent sound absorption performance of high and medium frequency bands, has good low-frequency, broadband and high-efficiency sound absorption performance, and has the advantages of simple structure, easiness in processing and manufacturing, low cost and the like.

Referring to fig. 20, a schematic structural diagram of a superstructure module provided in an embodiment of the present invention is shown, where each metamaterial unit in the superstructure module is periodically arranged in one dimension. The length of the metamaterial unit in the superstructure module in the x-axis direction is unlimited and can be infinitely extended. And each metamaterial unit in the superstructure module is periodically arranged along the y-axis direction.

Referring to fig. 21, which is a schematic structural diagram of a super-structure module according to an embodiment of the present invention, each super-material unit in the super-structure module is periodically arranged in two dimensions. The metamaterial units in the superstructure module are periodically arranged along the x-axis direction and are also periodically arranged along the y-axis direction.

In a preferred embodiment of the present invention, the superstructure module is formed by connecting two different metamaterial units in parallel, and the periodic arrangement is a two-dimensional periodic arrangement. As shown in fig. 22, a schematic structural diagram of a superstructure module is provided, which has a structural dimension of 80mm in the x-axis direction, 80mm in the y-axis direction, and 100mm in the z-axis direction. The superstructure module comprises two acoustic guided wave channels 1 which are respectively a linear channel and an L-shaped zigzag channel, and the width of the channels is selected to be equal in width and gradient change; the impedance efficient modulation sound absorber 3 comprises an impedance modulation channel 3b, the shape of the cross section parallel to the guided wave direction is selected to be rectangular, and the impedance efficient modulation sound absorber 3 is completely filled in the acoustic guided wave channel 1; the enclosure wall 2 is made of steel and is formed by welding, and has good bearing capacity; the high-porosity sound absorption medium 3a is selected from a foam type porous material; and the high-porosity sound absorption medium 3a is fixedly connected with the surrounding wall 2 in a cementing manner. The metamaterial unit comprises a sound wave high-transmissivity cover plate 4 which is selected as a slotted plate, the shape of a slot is rectangular, a metal plate is selected, the material is steel, and the super-structure module is matched with the high-rigidity surrounding wall 2, so that the whole super-structure module has good bearing capacity. As shown in fig. 23, which is a graph of sound absorption coefficients corresponding to this embodiment, it can be known that the sound absorption coefficients are all above 0.9 and reach 0.965 on average in the low-frequency broadband range of 273 to 1000 Hz; in the low-frequency broadband range of 294-779 Hz, the sound absorption coefficient is above 0.96 and reaches 0.984 on average.

In another preferred embodiment of the present invention, the superstructure module is formed by connecting four different metamaterial units in parallel, and the periodic arrangement is a one-dimensional periodic arrangement. As shown in fig. 24, a schematic structural diagram of the superstructure module is provided, wherein the structural dimension along the x-axis direction is 20mm, the structural dimension along the y-axis direction can be any preset dimension, and is selected to be 60mm, and the structural dimension along the z-axis direction is 100mm. The superstructure module comprises four acoustic guided wave channels 1 which are respectively a straight line channel and three L-shaped zigzag channels, and the width of the channels is selected to be equal width and gradient change; the impedance efficient modulation sound absorbers 3 only comprise one impedance modulation channel 3b, the cross section parallel to the guided wave direction is selected to be conical, and the impedance efficient modulation sound absorbers 3 are completely filled in the acoustic guided wave channel 1; the enclosure wall 2 is formed by selecting a toughened glass plate and connecting the toughened glass plate in a cementing manner; the high-porosity sound absorption medium 3a is selected from a foam type porous material; and the high-porosity sound absorption medium 3a and the enclosure wall 2 are fixedly connected in a cementing manner. Referring to figure 25, in the frequency range of 271-20000 Hz, the sound absorption coefficient is above 0.928, and the average sound absorption coefficient reaches 0.993; within the low-frequency broadband range of 260-1000 Hz, the sound absorption coefficient is above 0.9 and reaches 0.943 on average.

The results of the above examples show that: the invention can obviously improve the sound absorption performance of low-frequency-band sound waves by utilizing the wide-band large-amplitude modulation of the acoustic impedance and the low-frequency coupling resonance effect of the acoustic impedance, simultaneously keeps the excellent sound absorption efficiency of a medium-high frequency band, and has good low-frequency, broadband and high-efficiency sound absorption performance.

All of the features disclosed in this specification, or all of the steps in any method or process so disclosed, may be combined in any combination, except combinations of features and/or steps that are mutually exclusive. Any feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving equivalent or similar purposes, unless expressly stated otherwise. That is, unless expressly stated otherwise, each feature is only an example of a generic series of equivalent or similar features.

The above description is only one of the preferred embodiments of the present invention, but the scope of the present invention is not limited thereto. Other embodiments of various modifications and equivalent arrangements, which may be readily devised by those skilled in the art based upon or using the teachings herein, are also within the scope of the present invention.

Claims (12)

1. A metamaterial unit for high-efficient sound absorption of low frequency broadband, its characterized in that encloses the metamaterial cavity that closes to form and sets up including the polylith bounding wall and is in acoustics guided wave passageway in the metamaterial cavity, be provided with the high-efficient modulation sound absorber of impedance in the acoustics guided wave passageway.

2. The metamaterial unit for low-frequency broadband efficient sound absorption according to claim 1, further comprising a sound wave high-transmittance cover plate disposed on the metamaterial cavity, wherein the acoustic wave guide channels in the metamaterial cavity are communicated with the outside through openings or slits in the sound wave high-transmittance cover plate.

3. The metamaterial unit for low-frequency broadband high-efficiency sound absorption according to claim 1 or 2, wherein the impedance high-efficiency modulation sound absorber comprises a high-porosity sound absorption medium and an impedance modulation channel, the high-porosity sound absorption medium covers the inner side wall of the acoustic wave guide channel, and more than one impedance modulation channel is arranged in the high-porosity sound absorption medium.

4. A metamaterial unit for low frequency broadband efficient sound absorption according to claim 3, wherein the axial direction of the impedance modulation channel is consistent with the wave guiding direction of the acoustic wave guiding channel in which it is located.

5. A metamaterial unit for low-frequency broadband high-efficiency sound absorption as claimed in claim 4, wherein the geometric configuration of the impedance modulation channel is changed to realize wide-frequency and large-amplitude modulation of acoustic impedance, and simultaneously, a resonance absorption peak is generated in a low frequency band, so that the sound absorption performance of the low frequency band is improved.

6. A metamaterial unit for low frequency broadband high efficiency sound absorption as claimed in claim 4, wherein the cross-sectional shape of the impedance modulation channel in the direction parallel to the waveguiding direction of its acoustic waveguiding channel is rectangular or conical or trapezoidal or diamond or regular symmetric polygon.

7. The metamaterial unit for low-frequency broadband high-efficiency sound absorption according to claim 4, 5 or 6, wherein the acoustic guided wave channel is a straight channel or a zigzag channel, and the width of the acoustic guided wave channel is equal in width or gradually changed or gradiently changed along the guided wave direction of the acoustic guided wave channel.

8. The metamaterial unit for low frequency broadband high efficiency sound absorption of claim 7, wherein the high porosity sound absorbing medium fills the entire acoustic guided wave channel; or the high porosity sound absorbing medium fills part of the length of the acoustic waveguide channel from the bottom of the acoustic waveguide channel.

9. The metamaterial unit for low-frequency broadband efficient sound absorption according to claim 1, 2, 4, 5, 6 or 8, wherein the metamaterial cavity is made of metal plates, plastic plates, hard fiber plates, plywood, gypsum boards, synthetic resin plates or tempered glass plates;

the metamaterial cavity is formed by riveting, welding or gluing in a connecting mode, or the metamaterial cavity is integrally formed by casting or additive machining.

10. A metamaterial unit for low frequency, broadband, high efficiency sound absorption as in claim 9, wherein the high porosity sound absorbing media is organic fiber type porous material, inorganic fiber type porous material, foam type porous material or metal type porous material.

11. A superstructure module, characterized in that, comprises a plurality of metamaterial units for low frequency broadband high efficiency sound absorption as claimed in claim 1, each metamaterial unit is connected in parallel.

12. The superstructure module according to claim 11, wherein said metamaterial units are arranged in one-dimensional or two-dimensional periodicity.

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