Ultra-wideband sound absorption unit and sound absorber based on micro-perforated plate back cavity filled with porous sound absorption material

Abstract

The invention relates to the technical field of noise control engineering and indoor acoustics, in particular to an ultra-wideband sound absorption unit based on a back cavity of a micro-perforated plate filled with a porous sound absorption material and a sound absorber. Each unit comprises a micro-perforated plate, a porous sound absorption material and a back cavity shell; a containing cavity is formed in the back cavity shell, and the micro-perforated plate covers an opening of the containing cavity; the containing cavity is filled with the porous sound absorption material which is attached to the inner side wall of the containing cavity, and an air channel extending in the depth direction is defined in the center area of the containing cavity. Thin air layers are arranged between the micro-perforated plate and the porous sound absorption material and between the micro-perforated plate and the air channel. According to the unit, ultra-wide-band efficient sound absorption from low frequency to high frequency can be achieved through a small number of ultra-wide-band sound absorption units, and the unit has the advantages of being simple in structure and high in rigidity.

Description

Technical Field

[0001] This application relates to the fields of noise control engineering and indoor acoustics, and in particular to an ultra-wideband sound-absorbing unit and sound absorber based on porous sound-absorbing material filling the back cavity of a micro-perforated plate. Background Technology

[0002] With the acceleration of modern industrialization and the improvement of urbanization, noise pollution has become one of the most important environmental problems affecting people's quality of life and physical and mental health. In the fields of noise control engineering and interior acoustic design, the development of efficient sound-absorbing structures has always been a research hotspot. Among these, achieving efficient sound absorption from low frequencies to ultra-wideband has extremely high application value and scientific significance.

[0003] Existing sound absorption technologies are mainly divided into two categories: traditional sound-absorbing materials / structures and acoustic metamaterials. The first category consists of traditional sound-absorbing materials and structures. Porous sound-absorbing materials primarily utilize the viscosity and thermal conduction effects generated by the micropores within the material to dissipate sound energy; micro-perforated plates absorb sound through frictional damping within the micropores and the resonance effect of the back cavity. However, the sound absorption performance of these traditional technologies is strictly limited by physical dimensions, typically following the "quarter-wavelength" theory. This means that to achieve effective low-frequency sound absorption, the thickness of the material or back cavity must reach one-quarter of the sound wave wavelength. This implies that when dealing with low-frequency noise, traditional structures often require a large physical space, making it difficult to meet the needs of applications with strict thickness constraints, such as aerospace, automotive interiors, or small equipment.

[0004] The second category is acoustic metamaterials, which have emerged in recent years. To overcome the low-frequency sound absorption bottleneck of traditional materials, researchers have developed various subwavelength sound-absorbing metastructures, such as Helmholtz resonator-type absorbers, thin-film metamaterial absorbers, and Fabry-Pérot-type absorbers. These metamaterials, through localized resonance mechanisms, can achieve efficient absorption of specific low frequencies at the subwavelength scale.

[0005] However, existing acoustic metamaterial sound absorbers have significant drawbacks: Narrow sound absorption bandwidth: Since its sound absorption mechanism is mainly based on local resonance, it can usually only produce sound absorption peaks near the resonance frequency, resulting in a very narrow sound absorption bandwidth, making it difficult to cope with wide-band noise environments.

[0006] Complex structure and high cost: In order to broaden the sound absorption bandwidth, existing technologies often require complex series or parallel combinations of multiple resonant units, or the design of gradient structures. This not only makes the overall structure of the sound absorber extremely complex and increases its weight, but also greatly increases the manufacturing difficulty and production cost.

[0007] Therefore, how to achieve ultra-wideband efficient sound absorption from low to high frequencies using a small number of ultra-wideband sound-absorbing units while maintaining a simple structure, small size, light weight, and sufficient rigidity remains a major technical challenge that urgently needs to be solved in the field of acoustics. Summary of the Invention

[0008] Therefore, it is necessary to provide an ultra-wideband sound-absorbing unit that can achieve ultra-wideband high-efficiency sound absorption from low frequency to high frequency by using a small number of ultra-wideband sound-absorbing units, which has the characteristics of simple structure and high rigidity.

[0009] To achieve the above-mentioned objectives of this invention, the technical solution adopted is as follows: An ultra-wideband sound-absorbing unit based on a micro-perforated plate back cavity filled with porous sound-absorbing material includes a micro-perforated plate, porous sound-absorbing material, and a back cavity shell. The back cavity shell contains a receiving cavity, and the micro-perforated plate covers the opening of the receiving cavity. The porous sound-absorbing material fills the receiving cavity and adheres to its inner wall, forming a straight air channel extending along the depth direction in the central region of the receiving cavity. A thin air layer is provided between the micro-perforated plate, the porous sound-absorbing material, and the straight air channel. The sound-absorbing unit achieves broadband sound absorption through impedance matching of the micro-perforated plate, the thin air layer, and the composite back cavity formed by the porous sound-absorbing material and the straight air channel.

[0010] Preferably, the cross-section of the back cavity shell is square, the porous sound-absorbing material fills the inner walls of the back cavity, and the straight air channel is located in the central region.

[0011] Furthermore, the acoustic parameters of the porous sound-absorbing material satisfy the Johnson-Champoux-Allard model, and its flow resistance is... Porosity Twists and turns Viscous characteristic length and thermal characteristic length The acoustic impedance of the micro-perforated plate is a preset value. The calculation formula is as follows: in, air viscosity, For the thickness of the micro-perforated plate, The diameter of the perforation. The perforation constant is Angular frequency, air density, It is the imaginary unit.

[0012] Furthermore, the equivalent density of the porous sound-absorbing material and equivalent bulk modulus The calculation formulas are as follows:

[0013]

[0014]

[0015] in, For Prandtl numbers, The specific heat ratio of air. Atmospheric pressure.

[0016] Furthermore, the equivalent density of the air channel and equivalent bulk modulus The calculation formulas are as follows:

[0017] in, Here is the shape factor parameter, for a width of rectangular channel, ， The wave number in the air. The speed of sound.

[0018] Furthermore, the equivalent parameters of the composite layer composed of porous sound-absorbing material and air channels in the ultra-wideband sound-absorbing unit are calculated using the dual-pore theory, and its composite equivalent density is... and composite equivalent bulk modulus They are respectively:

[0019] in, This represents the area ratio of the air passage in the back cavity cross-section.

[0020] Furthermore, the total input impedance of the ultra-wideband sound-absorbing unit The calculation formula is: in, For the impedance of microperforated plates based on volume velocity, Perforation rate; The total impedance of the back cavity is determined by the impedance of the thin air layer. and the input impedance of the composite layer The results were obtained from the series calculation:

[0021] in, The thickness of the thin air layer, , For the corresponding unit cross-sectional area, , , , This refers to the effective length of the air passage for the corresponding unit.

[0022] Furthermore, the reflection coefficient of the ultra-wideband sound-absorbing unit... Specifically:

[0023] Its sound absorption coefficient for: .

[0024] The ultra-wideband sound absorber, which is based on porous sound-absorbing material filling the back cavity of a micro-perforated plate, is composed of several ultra-wideband sound-absorbing units arranged and combined.

[0025] Preferably, the reflection coefficient is as follows: the ultra-wideband sound-absorbing units are arranged according to a preset array period to form a sound-absorbing array; in the sound-absorbing array, the resonant frequency of the sound absorber is adjusted by adjusting the effective length of the air channel, the filling thickness of the porous sound-absorbing material, and the cross-sectional length and width of the ultra-wideband sound-absorbing unit.

[0026] The beneficial effects of this invention are as follows: This invention discloses an ultra-wideband sound-absorbing unit based on a micro-perforated plate back cavity filled with porous sound-absorbing material, comprising a micro-perforated plate, porous sound-absorbing material, and a back cavity shell. The back cavity shell contains a receiving cavity, and the micro-perforated plate covers the opening of the receiving cavity. The porous sound-absorbing material fills the receiving cavity and adheres to its inner wall, forming a straight air channel extending along the depth direction in the central region of the receiving cavity. A thin air layer is provided between the micro-perforated plate, the porous sound-absorbing material, and the straight air channel. The sound-absorbing unit achieves broadband sound absorption through impedance matching of the micro-perforated plate, the thin air layer, and the composite back cavity formed by the porous sound-absorbing material and the straight air channel. The structure of this invention can greatly broaden the sound absorption bandwidth and low-frequency sound absorption performance of the unit. A single ultra-wideband sound-absorbing unit can achieve low-frequency to ultra-wideband sound absorption, and two ultra-wideband sound-absorbing units connected in parallel can enhance low-frequency sound absorption performance while reducing structural thickness. This sound absorber has a simple structure, small size, high rigidity, and is easy to manufacture, making it perfectly suited to different application scenarios. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of an ultrawideband sound absorber based on porous sound-absorbing material filling the back cavity of a micro-perforated plate in one embodiment; Figure 2 This is a schematic diagram of a two-dimensional cross-section of the sound absorber in one embodiment; Figure 3 This is a schematic diagram of the sound absorption curve of an ultra-wideband sound-absorbing unit in one embodiment; In the figure, 1 is a micro-perforated plate, 2 is a porous sound-absorbing material, and 3 is the back cavity shell. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0029] Example 1 like Figure 1 As shown, an ultra-wideband sound-absorbing unit based on a micro-perforated plate back cavity filled with porous sound-absorbing material includes a micro-perforated plate 1, a porous sound-absorbing material 2, and a back cavity shell 3. The back cavity shell 3 has a receiving cavity, and the micro-perforated plate 1 covers the opening of the receiving cavity. The porous sound-absorbing material 2 fills the receiving cavity and adheres to the inner wall of the receiving cavity, forming a straight air channel extending along the depth direction in the central region of the receiving cavity. A thin air layer is provided between the micro-perforated plate 1, the porous sound-absorbing material 2, and the straight air channel. The sound-absorbing unit achieves broadband sound absorption through impedance matching of the micro-perforated plate 1, the thin air layer, and the composite back cavity formed by the porous sound-absorbing material 2 and the straight air channel. In this embodiment, the broadband sound absorption performance of the sound absorber was studied based on theoretical derivation, and the accuracy of the theoretical derivation was verified by numerical simulation using the finite element software COMSOL Multiphysics. The introduction of rubber greatly broadens the sound absorption bandwidth of the unit and improves the low-frequency sound absorption performance.

[0030] like Figure 2 As shown, in one specific embodiment, the cross-section of the back cavity shell 3 is square, the porous sound-absorbing material 2 fills the inner wall around the back cavity, and the straight air channel is located in the central region.

[0031] In one specific embodiment, the acoustic parameters of the porous sound-absorbing material 2 satisfy the Johnson-Champoux-Allard model, and its flow resistivity is... Porosity Twists and turns Viscous characteristic length and thermal characteristic length This is a preset value; In this embodiment, the flow resistance is... The porosity is 0.996, the tortuosity factor is 1.04, and the viscous characteristic length is... The thermal feature length is The acoustic impedance of the microperforated plate 1 The calculation formula is as follows: in, air viscosity, For the thickness of the micro-perforated plate, The diameter of the perforation. The perforation constant is Angular frequency, air density, It is the imaginary unit.

[0032] In one specific embodiment, the equivalent density of the porous sound-absorbing material 2 is... and equivalent bulk modulus The calculation formulas are as follows:

[0033]

[0034]

[0035] in, For Prandtl numbers, The specific heat ratio of air. Atmospheric pressure.

[0036] In one specific embodiment, the equivalent density of the air channel and equivalent bulk modulus The calculation formulas are as follows:

[0037] in, Here is the shape factor parameter, for a width of rectangular channel, ， The wave number in the air. The speed of sound.

[0038] In one specific embodiment, the equivalent parameters of the composite layer consisting of porous sound-absorbing material and air channels in the ultra-wideband sound-absorbing unit are calculated using the dual-pore theory, and its composite equivalent density is... and composite equivalent bulk modulus They are respectively:

[0039] in, This represents the area ratio of the air passage in the back cavity cross-section.

[0040] In one specific embodiment, the total input impedance of the ultra-wideband sound-absorbing unit The calculation formula is: in, For the impedance of microperforated plates based on volume velocity, Perforation rate; The total impedance of the back cavity is determined by the impedance of the thin air layer. and the input impedance of the composite layer The results were obtained from the series calculation:

[0041] in, The thickness of the thin air layer, , For the corresponding unit cross-sectional area, , , , This refers to the effective length of the air passage for the corresponding unit.

[0042] The reflection coefficient of the ultra-wideband sound-absorbing unit Specifically:

[0043] Its sound absorption coefficient for: .

[0044] Example 2, The ultra-wideband sound absorber, which is based on porous sound-absorbing material filling the back cavity of a micro-perforated plate, is composed of several ultra-wideband sound-absorbing units arranged and combined.

[0045] In one specific embodiment, the reflection coefficient is as follows: the ultra-wideband sound-absorbing units are arranged according to a preset array period to form a sound-absorbing array; in the sound-absorbing array, the resonant frequency of the sound absorber is adjusted by adjusting the effective length of the air channel, the filling thickness of the porous sound-absorbing material 2, and the cross-sectional length and width of the ultra-wideband sound-absorbing unit.

[0046] In one specific embodiment, the effective length of the air channel, the thickness of the porous material filling the inner wall, and the unit cross-sectional size are all negatively correlated with the resonant frequency.

[0047] Example 3 In one specific embodiment, the sound absorber requires only one unit with a total thickness of H=108 mm and a perforation rate of 50%. The sample's wall thickness and perforated plate thickness... All are 1 mm, the effective length and width of the back cavity are both W=45 mm, and the diameter of the perforated plate is 1 mm. The thickness of the porous sound-absorbing material filling the inner walls is mm. The thickness of the thin air layer is The width of the middle air passage .

[0048] In one specific embodiment, the first sound-absorbing unit A and the second sound-absorbing unit B are arranged according to a preset array period to form a sound-absorbing array plate; the resonant frequency of the sound absorber is adjusted by adjusting the effective length of the air channel, the filling thickness of the porous sound-absorbing material, and the cross-sectional length and width of the unit.

[0049] In one specific embodiment, the thickness of the thin air layer The range is from 0.5mm to 2mm; the porous sound-absorbing material 2 is melamine sponge or polyester fiber cotton.

[0050] In this embodiment, as Figure 3 As shown, the sound absorption coefficient of the composite sound absorber was calculated, and the accuracy of the theory was verified by numerical calculation using COMSOL software. The two methods show good consistency, proving the accuracy of the theoretical model. The proposed composite sound absorber exhibits a sound absorption coefficient greater than 0.8 from 238 Hz and greater than 0.9 from 285 Hz. The high consistency between the theoretical calculation and simulation results demonstrates that the sound absorber possesses excellent low-frequency to ultra-wideband sound absorption performance.

[0051] Therefore, this invention designs a composite sound absorber capable of achieving perfect sound absorption from low frequencies to ultra-wideband by attaching porous sound-absorbing material to the inner walls of the back cavity of a micro-perforated plate. Only one unit is needed to achieve low-frequency broadband sound absorption in a subwavelength structure. Theoretical calculations and simulations have proven the rationality of the design. Compared with existing technologies, this structure is small in size, simple in design, and requires no complicated design process, making it perfectly suited for various sound absorption scenarios.

Claims

1. An ultra-wideband sound-absorbing unit based on a porous sound-absorbing material filling the back cavity of a micro-perforated plate, characterized in that, The device includes a micro-perforated plate (1), a porous sound-absorbing material (2), and a back cavity shell (3). The back cavity shell (3) has a receiving cavity, and the micro-perforated plate (1) covers the opening of the receiving cavity. The porous sound-absorbing material (2) fills the receiving cavity and is attached to the inner wall of the receiving cavity, forming a straight air channel extending along the depth direction in the central area of ​​the receiving cavity. A thin air layer is provided between the micro-perforated plate (1), the porous sound-absorbing material (2), and the straight air channel. The sound-absorbing unit achieves broadband sound absorption through impedance matching of the micro-perforated plate (1), the thin air layer, and the composite back cavity composed of the porous sound-absorbing material (2) and the straight air channel.

2. The ultra-wideband sound-absorbing unit based on porous sound-absorbing material filling the back cavity of a micro-perforated plate according to claim 1, characterized in that, The back cavity shell (3) has a square cross-section, the porous sound-absorbing material (2) fills the inner wall of the back cavity, and the straight air channel is located in the central area.

3. The ultra-wideband sound-absorbing unit based on porous sound-absorbing material filling the back cavity of a micro-perforated plate according to claim 1, characterized in that, The acoustic parameters of the porous sound-absorbing material (2) satisfy the Johnson-Champoux-Allard model, and its flow resistance is... Porosity Twists and turns Viscous characteristic length and thermal characteristic length The acoustic impedance of the micro-perforated plate (1) is a preset value. The calculation formula is as follows: in, air viscosity, For the thickness of the micro-perforated plate, The diameter of the perforation. The perforation constant is Angular frequency, air density, It is the imaginary unit.

4. The ultra-wideband sound-absorbing unit based on porous sound-absorbing material filling the back cavity of a micro-perforated plate according to claim 3, characterized in that, The equivalent density of the porous sound-absorbing material (2) and equivalent bulk modulus The calculation formulas are as follows: in, For Prandtl numbers, The specific heat ratio of air. Atmospheric pressure.

5. The ultra-wideband sound-absorbing unit based on porous sound-absorbing material filling the back cavity of a micro-perforated plate according to claim 4, characterized in that, The equivalent density of the air channel and equivalent bulk modulus The calculation formulas are as follows: in, Here is the shape factor parameter, for a width of rectangular channel, , The wave number in the air. The speed of sound.

6. The ultra-wideband sound-absorbing unit based on porous sound-absorbing material filling the back cavity of a micro-perforated plate according to claim 5, characterized in that, The equivalent parameters of the composite layer consisting of porous sound-absorbing material and air channels in the ultra-wideband sound-absorbing unit were calculated using the dual-pore theory, and its composite equivalent density was... and composite equivalent bulk modulus They are respectively: in, This represents the area ratio of the air passage in the back cavity cross-section.

7. The ultra-wideband sound-absorbing unit based on porous sound-absorbing material filling the back cavity of a micro-perforated plate according to claim 6, characterized in that, The total input impedance of the ultra-wideband sound-absorbing unit The calculation formula is: in, For the impedance of microperforated plates based on volume velocity, Perforation rate; The total impedance of the back cavity is determined by the impedance of the thin air layer. and the input impedance of the composite layer The results were obtained from the series calculation: in, The thickness of the thin air layer, , For the corresponding unit cross-sectional area, , , , This refers to the effective length of the air passage for the corresponding unit.

8. The ultra-wideband sound-absorbing unit based on porous sound-absorbing material filling the back cavity of a micro-perforated plate according to claim 7, characterized in that, The reflection coefficient of the ultra-wideband sound-absorbing unit Specifically: Its sound absorption coefficient for: .

9. An ultrawideband sound absorber based on porous sound-absorbing material filling the back cavity of a micro-perforated plate, characterized in that, It is composed of a plurality of ultra-wideband sound-absorbing units as described in any one of claims 1 to 8.

10. The ultrawideband sound absorber based on porous sound-absorbing material filling the back cavity of a micro-perforated plate according to claim 9, characterized in that, The reflection coefficient is as follows: the ultra-wideband sound-absorbing units are arranged according to the preset array period to form a sound-absorbing array; in the sound-absorbing array, the resonant frequency of the sound absorber is adjusted by adjusting the effective length of the air channel, the filling thickness of the porous sound-absorbing material (2) and the cross-sectional length and width of the ultra-wideband sound-absorbing unit.

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