Impedance composite type low-frequency broadband superstructure sound absorber and impedance transfer matching composite design method thereof

Abstract

The invention belongs to the technical field of noise reduction, and particularly relates to an impedance composite type low-frequency broadband superstructure sound absorber and an impedance transfer matching composite design method thereof.The impedance composite type low-frequency broadband superstructure sound absorber comprises a mounting side plate, an end face perforated plate, a metal wire mesh, a perforated material domain and a bottom plate; the end face perforated plate and the bottom plate are arranged at the axial end part of the mounting side plate to form a cavity with a hole in one end; the metal wire mesh is arranged in the cavity, and a surface cavity is formed between the end face perforated plate and the metal wire mesh; the perforated material area is arranged between the metal wire mesh and the bottom plate, and a back cavity is formed between the bottom and the bottom plate; the perforated material domain comprises at least one perforated material layer; the perforated material layer is of an acoustic impedance matching structure. Compared with the prior art, the problem that the cost is increased due to the complex structure of the acoustic superstructure in the prior art is solved. According to the impedance composite type low-frequency broadband superstructure sound absorber, low-frequency and broadband noise control is achieved, meanwhile, the structure is simple, and the design and production efficiency is high.

Description

Technical Field

[0001] The present invention belongs to the technical field of noise reduction, and in particular relates to an impedance composite low-frequency broadband superstructure sound absorber and an impedance transfer matching composite design method thereof. Background Art

[0002] With the rapid development of modern cities, noise pollution has become a prominent problem. Especially when there are noise sources that combine low frequency and broadband, it is difficult to achieve noise control using ordinary sound-absorbing materials.

[0003] Traditional acoustic materials are generally divided into resistive sound-absorbing materials and resistant sound-absorbing structures. Resistive sound-absorbing materials typically refer to porous materials that absorb mid- and high-frequency sound waves effectively, while resistant sound-absorbing structures typically refer to perforated plate structures that absorb sound effectively over a narrow band. However, for low-frequency sound waves, a porous material with a thickness of at least one-quarter the wavelength is generally required to achieve good sound absorption performance. While resistant sound-absorbing structures can partially address low-frequency sound absorption issues, their narrow-band absorption mechanism prevents them from addressing broadband sound absorption.

[0004] In recent years, the development of acoustic superstructures has proposed new ideas for noise control. Acoustic superstructures are digital artificial structures with special acoustic properties. By optimizing the design of their internal structural parameters, they can achieve excellent acoustic performance that surpasses traditional materials. For example, CN116153280A discloses a composite broadband noise reduction superstructure, which includes a mid-high frequency noise reduction body and a low-frequency broadband noise reduction body. This solution achieves full-band noise reduction through a combination of a multi-layer composite mid-high frequency noise reduction body and a low-frequency broadband noise reduction body and a sound-absorbing cavity. However, acoustic superstructures still face some challenges in practical applications. For example, acoustic superstructures are usually complex in structure and have high processing requirements. Although they can achieve excellent acoustic performance, the overall comprehensive cost is greatly improved compared to traditional materials. Summary of the Invention

[0005] The present invention aims to address at least one of the aforementioned issues by providing an impedance-complex, low-frequency, broadband superstructure sound absorber and a method for its impedance transfer and matching composite design. This approach addresses the cost-increasing complexity of existing acoustic superstructures. The impedance-complex, low-frequency, broadband superstructure sound absorber achieves low-frequency, broadband noise control while maintaining a simple design and high design and production efficiency.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] The first aspect of the present invention discloses an impedance composite low-frequency broadband superstructure sound absorber, comprising a mounting side plate, an end perforated plate, a metal mesh, a perforated material domain, and a bottom plate;

[0008] The end face perforated plate and the bottom plate are respectively arranged at the axial ends of the mounting side plates to form a cavity with an opening at one axial end;

[0009] The metal mesh is arranged inside the cavity, and a surface cavity is formed between the end face perforated plate and the metal mesh;

[0010] The perforated material domain is arranged between the metal mesh and the bottom plate, and a back cavity is formed between the bottom of the perforated material domain and the bottom plate;

[0011] The perforated material domain includes at least one perforated material layer;

[0012] The perforated material layer includes a porous material, an inner cavity and a perforated plate; the inner cavity is axially arranged to penetrate the perforated material layer, the porous material is enclosed outside the inner cavity, and the perforated plate is used to at least separate the perforated material layer from the back cavity;

[0013] The perforated material layer is an acoustic impedance matching structure.

[0014] Preferably, the inner cavity is arranged at the center of the perforated material domain, and the inner cavities of each perforated material layer are arranged concentrically.

[0015] Preferably, when the perforated material domain includes several perforated material layers, the perforated material layers are stacked in sequence, and the perforated plate is also used to separate adjacent perforated material layers.

[0016] Preferably, the thickness of the end face perforated plate is 0.5 to 6 mm; the thickness of the perforated plate is 0.5 to 6 mm.

[0017] Preferably, the end face perforated plate is provided with a plurality of circular perforations, the perforation diameter is 1 to 6 mm, and the perforation rate is 1 to 40%; the perforated plate is provided with a plurality of circular perforations, the perforation diameter is 1 to 6 mm, and the perforation rate is 1 to 40%.

[0018] Preferably, the wire diameter of the metal wire mesh is 0.23-0.02 mm, and the wire spacing is 1.33-0.042 mm.

[0019] Preferably, the porous material is one or more of glass wool, polyester fiber wool, melamine wool and polyimide wool, and the flow resistance is 5000-120000 Pa·s / m 2 .

[0020] The second aspect of the present invention discloses an impedance transfer matching composite design method for an impedance composite low-frequency broadband superstructure sound absorber as described above, wherein the normalized acoustic impedance ratio Z of the sound absorber is TsApproximately satisfying 1+0j, that is, the impedance of the composite low broadband sound-absorbing superstructure component achieves perfect impedance matching, and thus a broadband perfect sound absorption effect can be obtained;

[0021] The normalized acoustic impedance Z of the sound absorber is Ts for:

[0022] Z Ts =Z T / ρ0c0;

[0023] Where: Z T is the acoustic impedance of the sound absorber, ρ0 is the density of the air medium, and c0 is the sound velocity of the air medium;

[0024] The acoustic impedance Z of the sound absorber T for:

[0025]

[0026] Where: k b3 is the wave number of the cavity, Z b3 is the characteristic impedance of the cavity, h b3 is the thickness of the facial cavity; Z 04 is the acoustic impedance from the metal mesh to the base plate, Z 04 =Z Tn +Z m , Z Tn is the acoustic impedance from the perforated material domain to the base plate, Z m is the acoustic impedance of the metal mesh; Z p is the acoustic impedance of the end perforated plate; j is an imaginary number.

[0027] Preferably, the acoustic impedance Z from the perforated material domain to the bottom plate is Tn The transfer matrix M from the top surface of the top perforated material layer to the bottom plate T Get;

[0028] The transfer matrix M T for:

[0029]

[0030] Where: M i is the transfer matrix of the i-th perforated material layer, n is the total number of perforated material layers, M b5 is the transfer matrix of the back cavity;

[0031] The transfer matrix M T The form is:

[0032]

[0033] The acoustic impedance Z Tn for:

[0034] Z Tn =M T1 / M T3 .

[0035] Preferably, the transfer matrix M of the back cavity b5 for:

[0036]

[0037] Where: k b5 is the wave number of the back cavity, Z b5 is the characteristic impedance of the back cavity, h b5 is the thickness of the back cavity;

[0038] The transfer matrix M of the i-th perforated material layer i for:

[0039]

[0040] in:

[0041] k i is the wave number of the i-th perforated material layer:

[0042]

[0043] Z i is the characteristic impedance of the i-th perforated material layer:

[0044]

[0045] h i is the thickness of the i-th perforated material layer;

[0046] ρ i is the equivalent dynamic mass density of the i-th perforated material layer:

[0047]

[0048] K i is the equivalent bulk modulus of the i-th perforated material layer:

[0049]

[0050] Where:

[0051] ω is the angular frequency; ρ i1 is the equivalent dynamic mass density of the porous material in the i-th perforated material layer, ρ i2 is the equivalent dynamic mass density of the inner cavity in the i-th perforated material layer, ρ i3 is the equivalent dynamic mass density of the perforated plate in the i-th perforated material layer; Ki1 is the equivalent bulk modulus of the porous material in the i-th perforated material layer, K i2 is the equivalent bulk modulus of the inner cavity in the i-th perforated material layer, K i3 is the equivalent bulk modulus of the perforated plate in the i-th perforated material layer; S i1 is the surface area of the porous material in the i-th perforated material layer, S i2 is the surface area of the inner cavity in the i-th perforated material layer; i = 1, 2, ..., n-1, n.

[0052] Compared with the prior art, the present invention has the following beneficial effects:

[0053] 1. Multiple layers of perforated material are installed inside the mounting side panels to effectively improve the absorber's mid- and low-frequency sound absorption efficiency and broaden its effective absorption bandwidth. While maintaining high mid- and high-frequency sound absorption efficiency, this design achieves superior low-frequency sound absorption performance, offering strong noise reduction performance and adjustable design parameters, allowing for flexible design. Its overall thickness is less than that of traditional sound-absorbing structures, breaking the limitations of thickness and absorption bandwidth, making it easier to meet diverse customized low- and broadband sound absorption requirements.

[0054] 2. By installing side panels, the end perforated panels, face cavity, wire mesh, perforated material domain, back cavity, and bottom plate are designed and positioned. The assembly of the present invention is completed by simply stacking each set of modularly prepared perforated materials within the mounting side panels. Compared to traditional sound-absorbing structures, the present invention offers a simpler configuration, smaller size, and reduced raw material consumption. It can be rapidly processed and assembled in modularized form, reducing construction difficulty and cost. It can be widely applied to next-generation architectural acoustics, public transportation, and other large-scale noise reduction projects, such as the construction of anechoic laboratories, conference rooms, concert halls, and road sound barriers. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 This is a schematic structural diagram of the impedance composite low broadband superstructure sound absorber according to Example 1 of the present application;

[0056] Figure 2 This is a graph showing the sound absorption coefficient of the impedance composite low broadband superstructure sound absorber according to Example 1 of the present application;

[0057] Figure 3 This is a schematic structural diagram of an impedance composite low broadband superstructure sound absorber according to Example 2 of the present application;

[0058] Figure 4 This is a sound absorption coefficient curve of the impedance composite low broadband superstructure sound absorber according to Example 2 of the present application;

[0059] In the figure: 1-installation side panel; 2-end perforated plate; 3-face cavity; 4-metal mesh; 5-back cavity; 6-bottom plate;

[0060] 11-first layer of porous material; 12-first layer of inner cavity; 13-first layer of perforated plate;

[0061] 21 - second layer of porous material; 22 - second layer of inner cavity; 23 - second layer of perforated plate;

[0062] 31 - third layer of porous material; 32 - third layer of inner cavity; 33 - third layer of perforated plate;

[0063] 41 - fourth layer of porous material; 42 - fourth layer of inner cavity; 43 - fourth layer of perforated plate;

[0064] 51 - fifth layer of porous material; 52 - fifth layer of inner cavity; 53 - fifth layer of perforated plate;

[0065] (n-1)1-the n-1th layer of porous material; (n-1)2-the n-1th layer of internal cavity; (n-1)3-the n-1th layer of perforated plate;

[0066] n1-the nth layer of porous material; n2-the nth layer of inner cavity; n3-the nth layer of perforated plate. DETAILED DESCRIPTION

[0067] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the embodiments described are only a part of the embodiments of this application, rather than all the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments in this application are within the scope of protection of this application.

[0068] The terms "first," "second," and the like in the specification and claims of this application are used to distinguish similar objects, and are not used to describe a specific order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate, so that the embodiments of this application can be implemented in an order other than that illustrated or described herein, and that the objects distinguished by "first," "second," and the like are generally of the same type, and do not limit the number of objects; for example, the first object can be one or more. In addition, the term "and / or" in the specification and claims refers to at least one of the connected objects, and the character " / " generally indicates that the objects connected are in an "or" relationship.

[0069] The impedance composite low broadband superstructure sound absorber provided by the embodiment of the present application is described in detail below with reference to the accompanying drawings through specific embodiments and application scenarios.

[0070] Example 1

[0071] This embodiment provides an impedance composite low broadband superstructure sound absorber, such as Figure 1As shown, an embodiment of the present application provides an impedance composite low-bandwidth superstructure sound absorber, comprising a mounting side panel 1, an end face perforated plate 2 fixedly arranged at the axial top end of the mounting side panel 1, a bottom plate 6 fixedly arranged at the axial bottom end, a metal mesh 4 arranged near the end face perforated plate 2, a surface cavity 3 formed by separating the metal mesh 4 and the end face perforated plate 2, a perforated material domain located between the metal mesh 4 and the bottom plate 6, and a back cavity 5 between the bottom of the perforated material domain and the bottom plate 6.

[0072] The end face perforated plate 2 and the metal wire mesh 4 are arranged at intervals to form a face cavity 3 with a certain thickness;

[0073] The perforated material domain is arranged in the form of at least one group of perforated material layers along the axial direction between the metal mesh 4 and the back cavity 5;

[0074] Each set of perforated material layers is further composed of a porous material, an inner cavity and a perforated plate. The inner cavity is longitudinally penetrated inside the porous material, and a perforated plate is provided at the bottom of the porous material and the inner cavity (the perforated plate supports the porous material).

[0075] The structural parameters of each set of perforated material layers are precisely designed through impedance matching to achieve near-perfect low-frequency and wide-bandwidth sound absorption performance.

[0076] As can be appreciated, by adjusting the structural parameters of each perforated material layer within the perforated material domain, the system can be adapted to various target sound absorption frequency bands, providing a wide range of design flexibility. Specifically, the number of perforated material layers, the thickness, pore size, and perforation ratio of each perforated plate group, the thickness and flow resistivity of each perforated material layer, and the size of the internal cavity can all be adjusted based on application requirements, thereby ensuring high low-bandwidth sound absorption performance across the entire superstructure (meeting target design requirements).

[0077] In the embodiment of the present application, the aforementioned impedance-composite, low-bandwidth superstructure sound absorber is employed. Multiple perforated material layers are disposed within the mounting side panel 1. As the size of the cavity within each perforated material layer changes, the impedance matching relationship between the porous material and air is effectively improved. Furthermore, the significant size disparity between the porous material's pores and the internal cavity allows for strong coupling between the two pore sizes, resulting in greater energy dissipation. This effectively improves the absorber's mid- and low-frequency sound absorption efficiency and broadens its effective absorption bandwidth. While maintaining high mid- and high-frequency sound absorption efficiency, it achieves superior low-frequency sound absorption performance, boasts strong noise reduction performance, and offers adjustable design parameters, allowing for flexible design. Its overall thickness is less than that of conventional sound-absorbing structures, transcending the limitations of thickness and absorption bandwidth, making it suitable for meeting diverse customized low-bandwidth sound absorption requirements.

[0078] In a preferred embodiment, as Figure 1As shown, the mounting side panels 1 and the bottom panel 6 constitute a mounting frame, inside which parallel end face perforated plates 2, a surface cavity 3, a metal mesh 4, a perforated material domain and a back cavity 5 are fixedly arranged from top to bottom.

[0079] It should be noted that the inner cavity in each set of perforated material layers is located in the central area of the porous material and is aligned in the axial direction in a symmetrical manner;

[0080] The porous materials in each group of perforated material layers are distributed around the inner cavity. The porous materials and the inner cavity are connected in parallel and in series with the perforated plate at the bottom.

[0081] The first perforated material layer in the plurality of perforated material layers is located below the metal wire mesh 4 and includes a first layer of porous material 11, a first layer of inner cavity 12 and a first layer of perforated plate 13;

[0082] The second perforated material layer in the plurality of perforated material layers is located below the first perforated plate 13 and includes a second layer of porous material 21, a second layer of inner cavity 22 and a second layer of perforated plate 23;

[0083] In this way, multiple sets of perforated material layers are stacked and assembled in sequence;

[0084] Then, the nth perforated material layer in the plurality of perforated material layers is located below the n-1th perforated plate (n-1)3, and includes the nth porous material layer n1, the nth inner cavity n2 and the nth perforated plate n3, where n≥2;

[0085] The n-th layer of perforated plate n3 is spaced apart from the bottom plate 6 to form a back cavity 5 .

[0086] If the perforated material layer is a single-layer structure, the end perforated plate 2, the surface cavity 3, the metal mesh 4, the perforated material domain (single-layer perforated material layer) and the back cavity 5 are fixedly arranged parallel to each other from top to bottom inside the installation frame.

[0087] In the embodiment of the present application, the above-mentioned impedance composite low broadband superstructure sound absorber is used.

[0088] By installing side panels 1, the end perforated panels 2, surface cavity 3, wire mesh 4, perforated material domain, back cavity 5, and bottom panel 6 are designed and positioned. The assembly of the present invention is completed by simply stacking each modularly prepared set of perforated materials within the cavity formed within the installed side panels 1. Compared to traditional sound-absorbing structures, the present invention offers a simpler configuration, smaller size, and reduced raw material consumption. It can be rapidly processed and assembled in modularized form, reducing construction difficulty and cost. It can be widely applied to the next generation of architectural acoustics, public transportation, and other large-scale noise reduction projects, such as the construction of anechoic laboratories, conference rooms, concert halls, and road sound barriers.

[0089] In a preferred embodiment, the impedance transfer matching composite design method of the above-mentioned impedance composite low broadband superstructure sound absorber is as follows:

[0090] like Figure 1 As shown,

[0091] The arrangement between the side panels 1 and the end perforated panels 2 and the bottom panel 6 is as follows from top to bottom in the axial direction: the surface cavity 3, the metal mesh 4, the first perforated material layer, the second perforated material layer, ..., the n-1th perforated material layer, the nth perforated material layer and the back cavity 5.

[0092] The first perforated material layer includes a first layer of porous material 11, a first layer inner cavity 12 enclosed by the first layer of porous material 11, and a first layer of perforated plate 13 for supporting the first layer of porous material 11 and separating the first layer of perforated material from the adjacent perforated material layer located thereunder.

[0093] The second perforated material layer includes a second layer of porous material 21, a second layer of inner cavity 22 enclosed by the second layer of porous material 21, and a first layer of perforated plate 23 for supporting the second layer of porous material 21 and separating the second layer of perforated material from an adjacent layer of perforated material located therebelow; ...; the n-1th perforated material layer includes an n-1th layer of porous material (n-1) 1, an n-1th layer of inner cavity (n-1) 2 enclosed by the n-1th layer of porous material (n-1) 1, and an n-1th layer of perforated plate (n-1) 3 for supporting the n-1th layer of porous material (n-1) 1 and separating the n-1th layer of perforated material from an adjacent layer of perforated material located therebelow;

[0094] The nth perforated material layer comprises an nth layer of porous material n1, an nth inner cavity n2 enclosed by the nth layer of porous material n1, and an nth perforated plate n3 for supporting the nth layer of porous material n1 and separating the nth layer of perforated material from the back cavity 5 located thereunder.

[0095] The structural parameters of each set of perforated material layers are precisely designed through impedance matching.

[0096] 1) Based on the equivalent dynamic mass density ρ of the porous material i1, the inner cavity i2 and the perforated plate i3 in the i-th group of perforated material layers i1 , ρ i2 , ρ i3 and the equivalent bulk modulus K i1 , K i2 , K i3 , the equivalent dynamic mass density (ρ i ) and equivalent bulk modulus (K i ) is expressed as:

[0097]

[0098] Where, i = 1, 2, ..., n-1, n, S i1 is the surface area of the i-th group of porous materials, S i2 is the surface area of the cavity in group i.

[0099] 2) Characteristic impedance of the i-th group of perforated material layers (Z i ) and wave number (k i ) is expressed as:

[0100]

[0101] Where ω is the angular frequency.

[0102] 3) According to the transmission relationship between the interlayer sound pressure and sound velocity, the transfer matrix (M i ) is expressed as:

[0103]

[0104] Where j is the imaginary unit, h i is the thickness of the i-th group of perforated material layers.

[0105] 4) The transfer matrix (M) formed by the back cavity 6 and the bottom of the perforated plate of the nth group of perforated material layers (nth layer perforated plate n3) to the bottom plate 6 b5 ) is expressed as:

[0106]

[0107] Where k b5 and Z b5 is the wave number and characteristic impedance of the back cavity 5, h b5 is the thickness of the back cavity 5.

[0108] 5) Transfer matrix (M) from the upper surface of the first perforated material layer to the bottom plate 6 T ) is expressed as:

[0109]

[0110] Where,

[0111] 6) Acoustic impedance (Z) from the upper surface of the first perforated material layer to the bottom plate 6 Tn ) is expressed as:

[0112] Z Tn =M T1 / M T3 .

[0113] 7) Finally, the end perforated plate 2, the surface cavity 3, the metal mesh 4, the perforated material domain, the back cavity 5 and the bottom plate 6 are connected in series to calculate the overall acoustic impedance Z of the impedance composite low broadband superstructure sound absorber. T and normalized acoustic impedance ratio (Z Ts ), the expression is:

[0114]

[0115] Z Ts =Z T / ρ0c0;

[0116] Where k b3 and Z b3 is the wave number and characteristic impedance of cavity 3; h b3 is the thickness of the surface cavity 3; Z 04 is the acoustic impedance from the metal mesh 4 to the bottom plate 6, Z 04 =Z Tn +Z m , Z m is the acoustic impedance of the metal mesh 4; Z p is the acoustic impedance of the end perforated plate 2; ρ0 and c0 are the density and sound speed of the air medium respectively.

[0117] After precise design of the structural parameters of each group of perforated material layers, end perforated plate 2, surface cavity 3, metal wire mesh 4 and back cavity 5 in the above impedance composite low broadband superstructure sound absorber, Z Ts The impedance of the designed structure is close to the air impedance within the target noise reduction frequency range, that is, the expected impedance of the designed structure approximately satisfies 1+0j. The impedance composite low broadband sound absorption superstructure component achieves perfect impedance matching and can obtain a broadband perfect sound absorption effect.

[0118] In a preferred embodiment, the thickness of the end face perforated plate 2, the first layer perforated plate 13, ..., the n-1th layer perforated plate (n-1) 3 and the nth layer perforated plate n3 is set to 0.5mm~6mm, and each of these perforated plates is provided with a plurality of circular perforations, the perforation diameter is set to 1mm~6mm, and the perforation rate is set to 1%~40%.

[0119] In a preferred embodiment, the wire diameter of the metal wire mesh 4 is set to 0.025 mm, the aperture is set to 0.027 mm, the wire spacing is set to 0.052 mm, and the mesh number is set to 500 meshes.

[0120] In a preferred embodiment, the porous material in each group of perforated material layers is set to glass wool, and the flow resistivity is set to 11500 Pa·s / m 2In some other embodiments, the porous material may be selected from one or more porous materials such as polyester fiber cotton, melamine cotton and polyimide cotton, and the flow resistance thereof is between 5000 and 120000 Pa·s / m 2 between.

[0121] In a preferred embodiment, as Figure 2 As shown, the horizontal axis represents the frequency, the vertical axis represents the sound absorption coefficient, the solid dotted line represents the sound absorption coefficient of the homogeneous glass wool (Comparative Example 1) with the same thickness as that of the present embodiment, the solid line represents the theoretical sound absorption coefficient obtained by analytical solution of the impedance composite low broadband superstructure sound absorber of the embodiment of the present application, and the hollow dotted line represents the sound absorption coefficient obtained by experimental testing of the impedance composite low broadband superstructure sound absorber of the embodiment of the present application.

[0122] The experimental tests were mainly conducted using an acoustic impedance tube test system in accordance with the national standard GB / T 18696.2-2002 "Measurement of sound absorption coefficient and acoustic impedance in acoustic impedance tubes Part 2: Transfer function method". The sound absorption coefficients of "homogeneous glass wool of the same thickness as that of this embodiment" and "the impedance composite low-bandwidth superstructure sound absorber of this embodiment" were tested.

[0123] By comparing the results, it can be seen that the theoretical sound absorption coefficient obtained by analysis is in good agreement with the sound absorption coefficient obtained by experimental test. The sound absorption effect of the sound absorber of this scheme is much higher than that of the homogeneous sound-absorbing glass wool of the same thickness as that of this embodiment in the low-frequency band.

[0124] It can be understood that the impedance composite low-bandwidth superstructure sound absorber of the embodiment of the present application has a high sound absorption coefficient in a wide frequency band. While having a high-efficiency mid- and high-frequency sound absorption effect, it has better low-frequency sound absorption performance compared to traditional sound-absorbing glass wool of the same thickness.

[0125] Example 2

[0126] like Figure 3 and Figure 4 As shown, this embodiment provides an impedance composite low broadband superstructure sound absorber, which is the same as the embodiment 1 except for the following contents.

[0127] In a preferred embodiment, the number of perforated material layers in the impedance-composite low-bandwidth superstructure sound absorber, n, is 5. The mounting side panel 1 is a plate-like structure with a thickness of 1 mm and a cross-sectional dimension of 200 mm x 600 mm. The front cavity 3 is 50 mm thick, and the back cavity 5 is 50 mm thick.

[0128] In a preferred embodiment, the thickness of the first layer of porous material 11 is set to 67 mm, and the cross-sectional dimensions of the cavity 12 in the first layer are 25 mm × 25 mm; the thickness of the second layer of porous material 21 is set to 98 mm, and the cross-sectional dimensions of the cavity 22 in the second layer are 34 mm × 34 mm; the thickness of the third layer of porous material 31 is set to 36 mm, and the cross-sectional dimensions of the cavity 32 in the third layer are 55 mm × 55 mm; the thickness of the fourth layer of porous material 41 is set to 128 mm, and the cross-sectional dimensions of the cavity 42 in the fourth layer are 72 mm × 72 mm; the thickness of the fifth layer of porous material 51 is set to 171 mm, and the cross-sectional dimensions of the cavity 52 in the fifth layer are 123 mm × 123 mm;

[0129] In a preferred embodiment, the end face perforated plate 2 has a thickness of 1 mm, a perforation diameter of 4 mm, and a perforation rate of 40%. The first layer of perforated plate 13 has a thickness of 0.8 mm, a perforation diameter of 1 mm, and a perforation rate of 15%. The second layer of perforated plate 23 has a thickness of 0.8 mm, a perforation diameter of 2 mm, and a perforation rate of 20%. The third layer of perforated plate 33 has a thickness of 0.8 mm, a perforation diameter of 1 mm, and a perforation rate of 10%. The fourth layer of perforated plate 43 has a thickness of 0.8 mm, a perforation diameter of 1 mm, and a perforation rate of 5%. The fifth layer of perforated plate 53 has a thickness of 0.8 mm, a perforation diameter of 1 mm, and a perforation rate of 3%.

[0130] In a preferred embodiment, as Figure 4 As shown, the horizontal axis represents frequency, the vertical axis represents sound absorption coefficient, the solid dots represent the sound absorption coefficient of homogeneous glass wool (Comparative Example 2) of the same thickness as that of this embodiment, the solid line represents the theoretically analyzed sound absorption coefficient of this embodiment 2, and the hollow dots represent the experimental sound absorption coefficient of this embodiment 2 obtained by a third-party institution. The testing method is the same as that of Example 1.

[0131] pass Figure 4 It can be seen that the impedance-composite, low-bandwidth superstructure sound absorber provided in Example 2 has a sound absorption coefficient exceeding 0.9 in the low-frequency range of 50Hz-200Hz, with an average sound absorption coefficient approaching 0.96, demonstrating remarkable low-frequency sound absorption performance. In the low- to mid-frequency range below 700Hz, its sound absorption coefficient is significantly higher than that of a conventional homogeneous glass wool material of the same thickness (600mm). This example achieves excellent low-frequency, broadband, and high sound absorption performance.

[0132] It should be noted that, in this article, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device comprising the element. In addition, it should be noted that the scope of the methods and devices in the embodiments of the present application is not limited to performing functions in the order shown or discussed, and may also include performing functions in a substantially simultaneous manner or in the opposite order according to the functions involved. For example, the described method may be performed in an order different from that described, and various steps may also be added, omitted, or combined. In addition, the features described with reference to certain examples may be combined in other examples.

[0133] In summary, the present invention has ultra-low frequency and wide-bandwidth sound absorption effects, a simple structure, flexible design, modular rapid processing and assembly, breaking through the limitations between the thickness and sound absorption bandwidth of traditional sound-absorbing structures, and can be widely used in the fields of noise reduction in large-scale projects such as the new generation of architectural acoustics and public transportation.

[0134] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. An impedance composite low-frequency broadband superstructure sound absorber, characterized in that: It includes a mounting side plate (1), an end perforated plate (2), a metal wire mesh (4), a perforated material domain and a bottom plate (6); The end face perforated plate (2) and the bottom plate (6) are respectively arranged at the axial ends of the mounting side plate (1), forming a cavity with an opening at one axial end; The metal wire mesh (4) is arranged inside the cavity, and a surface cavity (3) is formed between the end face perforated plate (2) and the metal wire mesh (4); The perforated material domain is arranged between the metal wire mesh (4) and the bottom plate (6), and a back cavity (5) is formed between the bottom of the perforated material domain and the bottom plate (6); The perforated material domain includes at least one perforated material layer; The perforated material layer comprises a porous material, an inner cavity and a perforated plate; the inner cavity is axially arranged to penetrate the perforated material layer, the porous material is enclosed outside the inner cavity, and the perforated plate is used to at least separate the perforated material layer from the back cavity (5); The perforated material layer is an acoustic impedance matching structure.

2. The impedance composite low-frequency broadband superstructure sound absorber according to claim 1, characterized in that: The inner cavity is arranged at the center of the perforated material domain, and the inner cavities of each perforated material layer are arranged concentrically.

3. The impedance composite low-frequency broadband superstructure sound absorber according to claim 1, characterized in that: When the perforated material domain includes several perforated material layers, the perforated material layers are stacked in sequence, and the perforated plate is also used to separate adjacent perforated material layers.

4. The impedance composite low-frequency broadband superstructure sound absorber according to claim 1, characterized in that: The thickness of the end face perforated plate (2) is 0.5-6 mm; the thickness of the perforated plate is 0.5-6 mm.

5. The impedance composite low-frequency broadband superstructure sound absorber according to claim 1, characterized in that: The end face perforated plate (2) is provided with a plurality of circular perforations, the perforation diameter is 1 to 6 mm, and the perforation rate is 1 to 40%; the perforated plate is provided with a plurality of circular perforations, the perforation diameter is 1 to 6 mm, and the perforation rate is 1 to 40%.

6. The impedance composite low-frequency broadband superstructure sound absorber according to claim 1, characterized in that: The wire diameter of the metal wire mesh (4) is 0.23-0.02 mm, and the wire spacing is 1.33-0.042 mm.

7. The impedance composite low-frequency broadband superstructure sound absorber according to claim 1, characterized in that: The porous material is one or more of glass wool, polyester fiber wool, melamine wool and polyimide wool, and the flow resistance is 5000-120000 Pa·s / m 2 .

8. A method for impedance transfer matching composite design of an impedance composite low-frequency broadband superstructure sound absorber according to any one of claims 1 to 7, characterized in that: The normalized acoustic impedance Z of the sound absorber is Ts Approximately satisfies 1+0j; The normalized acoustic impedance Z of the sound absorber is Ts for: WITH Ts =Z T / ρ0c0; Where: Z T is the acoustic impedance of the sound absorber, ρ0 is the density of the air medium, and c0 is the sound velocity of the air medium; The acoustic impedance Z of the sound absorber T for: Where: k b3 is the wave number of the cavity (3), Z b3 is the characteristic impedance of the cavity (3), h b3 is the thickness of the facial cavity (3); Z 04 is the acoustic impedance from the metal mesh (4) to the bottom plate (6), Z 04 =Z Tn +Z m , Z Tn is the acoustic impedance from the perforated material domain to the bottom plate (6), Z m is the acoustic impedance of the metal mesh (4); Z p is the acoustic impedance of the end-face perforated plate (2); j is an imaginary number.

9. The impedance transfer matching composite design method of an impedance composite low-frequency broadband superstructure sound absorber according to claim 8, characterized in that: The acoustic impedance Z of the perforated material domain to the bottom plate (6) Tn The transfer matrix M from the upper surface of the top perforated material layer to the bottom plate (6) T Get; The transfer matrix M T for: Where: M i is the transfer matrix of the i-th perforated material layer, n is the total number of perforated material layers, M b5 is the transfer matrix of the back cavity (5); The transfer matrix M T The form is: The acoustic impedance Z Tn for: Z Tn =M T1 / M T3 。 10. The impedance transfer matching composite design method of an impedance composite low-frequency broadband superstructure sound absorber according to claim 9, characterized in that: The transfer matrix M of the back cavity (5) b5 for: Where: k b5 is the wave number of the back cavity (5), Z b5 is the characteristic impedance of the back cavity (5), h b5 is the thickness of the back cavity (5); The transfer matrix M of the i-th perforated material layer i for: in: k i is the wave number of the i-th perforated material layer: Z i is the characteristic impedance of the i-th perforated material layer: h i is the thickness of the i-th perforated material layer; ρ i is the equivalent dynamic mass density of the i-th perforated material layer: K i is the equivalent bulk modulus of the i-th perforated material layer: Where: ω is the angular frequency; ρ i1 is the equivalent dynamic mass density of the porous material in the i-th perforated material layer, ρ i2 is the equivalent dynamic mass density of the inner cavity in the i-th perforated material layer, ρ i3 is the equivalent dynamic mass density of the perforated plate in the i-th perforated material layer; K i1 is the equivalent bulk modulus of the porous material in the i-th perforated material layer, K i2 is the equivalent bulk modulus of the inner cavity in the i-th perforated material layer, K i3 is the equivalent bulk modulus of the perforated plate in the i-th perforated material layer; S i1 is the surface area of the porous material in the i-th perforated material layer, S i2 is the surface area of the inner cavity in the i-th perforated material layer; i = 1, 2, ..., n-1, n.

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