A low-frequency broadband sound absorption device based on a perforated plate structure

Abstract

The application provides a slope bending cavity low-frequency broadband sound absorption device based on a perforated plate structure, which comprises a plurality of single structures connected in sequence; each single structure comprises an outer shell, a perforated plate and a plurality of bending path control plate assemblies; the middle part of the perforated plate is provided with a micropore array composed of a plurality of uniformly arranged sub-millimeter to millimeter level circular holes; in the inner cavity of the outer shell, the plurality of bending path control plate assemblies are uniformly arranged around the micropore array; after sound waves enter the inner cavity of the outer shell from the micropore array, the sound waves are diffused and blocked by the cavity wall of the outer shell and enter the bending path control plate assemblies; part of the sound wave energy is dissipated by friction through the micropore array, the bending path control plate assemblies increase the propagation path of the sound waves, increase the sound energy loss and move the absorption peak to a low frequency.

Description

Technical Field

[0001] This invention belongs to the field of low-frequency sound absorption technology design, specifically a low-frequency broadband sound absorption device based on a perforated plate structure with a sloping bent cavity. Background Technology

[0002] Low- and mid-frequency noises have strong penetrating power, long wavelengths, and strong diffraction capabilities, resulting in weak interaction between the sound-absorbing structure and the air medium, and low sound energy dissipation. Traditional sound-absorbing materials, such as porous materials and micro-perforated panels, only achieve perfect absorption of low-frequency sound waves when the structure thickness is one-quarter wavelength, leading to large structural thicknesses and limited applicability. However, acoustic metastructures have a depth subwavelength thickness, breaking through the one-quarter wavelength thickness limitation of traditional sound-absorbing materials and providing a solution for designing ultra-thin low-frequency sound-absorbing structures.

[0003] The purpose of the spatial bending resonant structure is to fold the cavity perpendicular to the incident direction of the sound wave, so that the cavity impedance and the dielectric impedance are matched to achieve perfect absorption.

[0004] For example, in the paper "Low-frequency broadband sound absorber based on micro-perforated plate and curled back cavity composite structure" published in Science Bulletin by Li Dongting et al., a sound-absorbing superstructure with a resonant frequency of 429Hz was designed by covering the top of the uniform cross-section spatial curved channel with a micro-perforated plate. However, the sound absorption bandwidth of this scheme is relatively narrow, only 39%.

[0005] In Chinese patent publication number CN110767207A, a spiral structure sound absorber is proposed, consisting of a top plate composed of a perforated cover plate with an embedded circular hole in the center, a sound-absorbing cavity composed of a spiral partition plate and a spiral cavity, and a bottom plate composed of a non-perforated baffle. This design creates an ultra-thin multi-absorption peak low-frequency absorber. Although it has two absorption peaks in the low-frequency range (<500Hz) at 146Hz and 417Hz, the absorption bandwidth of each absorption peak is very narrow, at 6.8% and 2.3%, respectively.

[0006] Chinese patent CN111549922A discloses a superstructure with an internally inserted angled sound-guiding corridor and a low-frequency sound-absorbing device made therefrom. Specifically, the outer shell is a cuboid with a top opening forming a sound-transmitting slit. Two internally inserted angled plates are symmetrically distributed, and the cavity formed by the inner wall of each angled plate and the inner wall of the outer shell constitutes an air cavity. Cavities are also formed between two angled plates and between the outer wall of each angled plate and the inner wall of the outer shell, thus creating a sound-guiding corridor. Results show an average sound absorption coefficient of 0.54 in the 50Hz-200Hz range, with absorption peaks greater than 0.9 at 100Hz and 200Hz. However, the porous material covering the surface is easily affected by the environment, resulting in poor durability of the superstructure's absorption efficiency, hindering practical applications. Summary of the Invention

[0007] To address the issues of narrow sound absorption bandwidth in existing spatial bending superstructures, the need for combinations of multiple types of sound-absorbing materials to improve sound absorption, and susceptibility to external conditions, this invention proposes a low-frequency broadband sound absorption device based on a perforated plate structure with a sloping bending cavity. This device combines a perforated plate structure with a sloping bending cavity, overcoming the thickness limitations of traditional low-frequency sound absorption structures and reducing the absorption frequency while expanding the absorption bandwidth.

[0008] The technical solution of this invention is as follows:

[0009] The aforementioned low-frequency broadband sound absorption device based on a perforated plate structure with a sloping bent cavity includes several individual structures connected in sequence; each individual structure includes an outer shell, a perforated plate, and multiple bending path control plate assemblies.

[0010] The outer shell is composed of a lower panel and a surrounding frame; a perforated plate is fixedly installed on the top of the outer shell; a micro-pore array consisting of several uniformly arranged sub-millimeter to millimeter-sized circular holes is opened in the middle of the perforated plate; in the internal cavity of the outer shell, multiple bending path control plate assemblies are evenly arranged around the micro-pore array.

[0011] When the sound wave enters the cavity of the outer shell from the micro-pore array, it diffuses and is blocked by the cavity wall, and then enters the bending path control plate assembly. Part of the sound wave energy is dissipated by friction of the micro-pore array. The bending path control plate assembly increases the propagation path of the sound wave, increases the sound energy loss, and causes the absorption peak to shift to lower frequencies.

[0012] Furthermore, the bending path control plate assembly includes a partition, an inclined plate, a vertical plate, and a horizontal plate; wherein one end of the inclined plate is fixed to the perforated plate and located on one side of the micro-hole array, the inclined plate is biased towards the outer shell frame plate on the same side, forming an angle θ with the perforated plate; the other end of the inclined plate is connected to one end of the vertical plate, the vertical plate is perpendicular to the perforated plate; the other end of the vertical plate is connected to one end of the horizontal plate, the horizontal plate is parallel to the perforated plate, and the horizontal plate points towards the outer shell frame plate on the same side, and has a gap with the outer shell frame plate on the same side; a partition is provided between the horizontal plate and the perforated plate, the partition is parallel to the perforated plate, one end of the partition is fixed to the outer shell frame plate, and the other end of the partition has a gap with the vertical plate.

[0013] Furthermore, the diameter of the sub-millimeter to millimeter-level circular hole is 0.3mm to 0.8mm.

[0014] Furthermore, the distance between the sub-millimeter to millimeter-scale circular holes is 3.53mm to 5.03mm.

[0015] Furthermore, the total perforation rate of the perforated plate is 2% to 10%.

[0016] Furthermore, the value of the angle θ is 24.62° to 71.05°.

[0017] Furthermore, the thickness of the perforated plate is 0.5mm to 2mm; the thickness of the lower panel and the surrounding frame is 0.5mm to 1.5mm.

[0018] Furthermore, the lengths of the partition and the horizontal plate are 5mm to 10mm, the length of the vertical plate is 3mm to 4mm, and the length of the inclined plate is 9.6mm to 35.94mm.

[0019] Furthermore, the distance between the horizontal plate and the lower panel of each bending path control plate assembly is equal, ranging from 10mm to 40mm; the gap between the horizontal plate and the outer shell frame plate on each side of each bending path control plate assembly is equal, ranging from 2mm to 4mm; the gap between the partition and the vertical plate in each bending path control plate assembly is equal, ranging from 2mm to 4mm; and the distance between the partition and the horizontal plate in each bending path control plate assembly is equal, ranging from 2mm to 4mm.

[0020] Furthermore, when the sound wave enters the cavity of the outer shell from the micro-pore array, it diffuses along the inclined panels of each bending path control plate assembly, then splits into multiple paths, enters the channels of each bending path control plate assembly, and finally falls into the semi-enclosed space formed by each bending path control plate assembly and the perforated plate.

[0021] Furthermore, the outer casing, perforated plate, and bending path control plate assembly are made of engineering plastics or lightweight metals.

[0022] Beneficial effects

[0023] The advantages of this invention lie in its simple structure, wide range of applications, and resistance to environmental influences. It exhibits a low peak sound absorption frequency and a wide sound absorption bandwidth, making it a promising candidate for sound absorption and noise reduction engineering. Further beneficial effects are as follows:

[0024] 1. This invention proposes a low-frequency broadband micro-perforated plate-covered inclined bend cavity sound-absorbing superstructure. Sound waves generated by a sound source first enter the cavity through sub-millimeter to millimeter-scale holes. Part of the energy carried by the sound waves is dissipated due to friction as they pass through these holes. Secondly, after passing through two bend cavities with varying cross-sections formed by two bend path control plate components, the increased propagation path of the sound waves further increases sound energy loss, causing the absorption peak to shift to lower frequencies. Finally, existing bend cavity superstructures have high absorption frequencies and narrow absorption bandwidths. To address this issue, the bend path control plate component employs an inclined bend cavity sound-absorbing superstructure, which has the advantages of low absorption peak frequency and wide absorption bandwidth.

[0025] 2. As can be seen from the embodiments, compared with the existing three-channel bent cavity sound-absorbing superstructure with the same number of bends, the present invention broadens the sound absorption bandwidth (the ratio of the difference between the two frequencies at the half maximum value of the absorption coefficient to the peak frequency) and shifts the resonant frequency to lower frequencies.

[0026] 3. By introducing symmetrically distributed bent-path control plate assemblies along both sides of the micro-perforated array into the cavity of a traditional micro-perforated plate sound-absorbing structure, the resonant frequency of the sound-absorbing structure can be shifted to lower frequencies without changing the total thickness. Simultaneously, inclined bent cavities of different sizes can be arranged in parallel to cover perforated plates with different perforation rates, pore sizes, and thicknesses, thus achieving a low-frequency wide-bandgap sound-absorbing superstructure.

[0027] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0028] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0029] Figure 1 This is a schematic diagram illustrating the coordinate definition and individual structural components of the present invention.

[0030] Figure 2 This is a schematic diagram of the individual structural dimensions of the present invention.

[0031] Figure 3 This is a schematic diagram of the second structure of the present invention.

[0032] Figure 4 This is a schematic diagram of the sound wave path of the present invention.

[0033] Figure 5 This is a schematic diagram of the sound absorption curve in Example 1.

[0034] Figure 6 This is a schematic diagram of the sound absorption curve in Example 2.

[0035] Appendix Figure 1 Markings: 1. Perforated plate; 2. Bottom panel; 3. Left frame plate; 4. Right frame plate; 5. Front frame plate; 6. Rear frame plate; 7. First partition plate; 8. First bending path control plate assembly; 8-I. First inclined panel; 8-II. First vertical plate; 8-III. First horizontal plate; 9. Second partition plate; 10. Second bending path control plate assembly; 10-I. Second inclined panel; 10-II. Second vertical plate; 10-III. Second horizontal plate; 11. Sub-millimeter to millimeter level holes.

[0036] Appendix Figure 2Markings: W - Width of outer casing; L - Length of outer casing; H - Height of outer casing; H1 - Distance between the first horizontal plate and the bottom panel; H2 - Distance between the first horizontal plate and the first partition; w1 - Distance between the first partition and the first vertical plate; w2 - Distance between the first horizontal plate and the left frame plate; H3 - Distance between the second horizontal plate and the bottom panel; H4 - Distance between the second horizontal plate and the second partition; w3 - Distance between the second partition and the second vertical plate; w4 - Distance between the second horizontal plate and the right frame plate; θ - Angle between the beveled panel and the perforated plate. Detailed Implementation

[0037] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0038] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0039] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0040] The present invention proposes a low-frequency broadband sound absorption device based on a perforated plate structure with a sloping bent cavity, comprising several individual structures connected in sequence. Different individual structures can correspond to different absorption peaks, thereby improving the sound absorption effect over a wider range.

[0041] like Figures 1-4 As shown, this inclined bending cavity low-frequency broadband sound absorption device based on a perforated plate structure includes several individual structures. Each individual structure includes an outer shell, a perforated plate 1, a first bending path control plate assembly, and a second bending path control plate assembly.

[0042] The outer casing is composed of a lower panel 2 and four surrounding frame plates (including a left frame plate 3, a right frame plate 4, a front frame plate 5, and a rear frame plate 6). A perforated plate 1 is fixedly installed on the top of the outer casing. The perforated plate 1 and the lower panel 2 are parallel to each other, the left frame plate 3 and the right frame plate 4 are parallel to each other and perpendicular to the lower panel 2, and the front frame plate 5 and the rear frame plate 6 are parallel to each other and perpendicular to the lower panel 2. The perforated plate 1 faces the sound source, and the lower panel 2 faces away from the sound source. A micro-pore array consisting of several uniformly arranged sub-millimeter to millimeter-sized circular holes 11 is opened in the middle of the perforated plate. In the internal cavity of the outer casing, the first bending path control plate assembly 8 and the second bending path control plate assembly 10 are symmetrically fixed on both sides of the micro-pore array.

[0043] The perforated plate has sub-millimeter to millimeter-sized circular holes with a diameter of 0.3mm to 0.8mm, a hole spacing of 3.53mm to 5.03mm, and a total perforation rate of 2% to 10%. The thickness of the perforated plate is 0.5mm to 2mm; the thickness of the bottom panel and the surrounding frame is 0.5mm to 1.5mm. The length of the partition and the horizontal plate is 5mm to 10mm, the length of the vertical plate is 3mm to 4mm, and the length of the inclined panel is 9.6mm to 35.94mm.

[0044] The value of the angle θ is 24.62° to 71.05°. Due to symmetry, the distance between the horizontal plate and the lower panel in the first and second bending path control plate assemblies is equal, ranging from 10mm to 40mm; the gap between the horizontal plate and the outer shell frame plate on each side in the first and second bending path control plate assemblies is equal, ranging from 2mm to 4mm; the gap between the partition and the vertical plate in the first and second bending path control plate assemblies is equal, ranging from 2mm to 4mm; and the distance between the partition and the horizontal plate in the first and second bending path control plate assemblies is equal, ranging from 2mm to 4mm.

[0045] The first bending path control plate assembly includes a first partition 7, a first inclined plate 8-Ⅰ, a first vertical plate 8-Ⅱ, and a first horizontal plate 8-Ⅲ. One end of the first inclined plate 8-Ⅰ is fixed to the perforated plate and located to the left of the micro-pore array. The first inclined plate 8-Ⅰ is inclined towards the left frame plate 3 on the same side, forming an angle θ with the perforated plate. The other end of the first inclined plate 8-Ⅰ is connected to one end of the first vertical plate 8-Ⅱ, which is perpendicular to the perforated plate. The other end of the first vertical plate 8-Ⅱ is connected to one end of the first horizontal plate 8-Ⅲ, which is parallel to the perforated plate and points towards the left frame plate 3 on the same side, with a gap between them. A first partition 7 is located between the first horizontal plate 8-Ⅲ and the perforated plate. The first partition 7 is parallel to the perforated plate, with one end fixed to the left frame plate 3, and the other end having a gap with the first vertical plate 8-Ⅱ. The first bending path control plate assembly realizes the inclined bending channel on the left side of the cavity.

[0046] The second bending path control plate assembly includes a second partition 9, a second inclined panel 10-I, a second vertical plate 10-II, and a second horizontal plate 10-III; wherein one end of the second inclined panel 10-I is fixed to the perforated plate and located on the right side of the micro-hole array, the second inclined panel 10-I is inclined toward the right frame plate 4 on the same side, and forms an angle θ with the perforated plate; the other end of the second inclined panel 10-I is connected to one end of the second vertical plate 10-II, the second vertical plate 10-II is perpendicular to the perforated plate; the other end of the second vertical plate 10-II is connected to One end of the second horizontal plate 10-III is parallel to the perforated plate and points towards the right frame plate 4 on the same side, with a gap between them; a second partition 9 is provided between the second horizontal plate 10-III and the perforated plate, the second partition 9 is parallel to the perforated plate, one end of the second partition 9 is fixed to the right frame plate 4, and the other end of the second partition 9 has a gap with the second vertical plate 10-II; the second bending path control plate assembly realizes the inclined bending channel on the right side of the cavity.

[0047] When the sound wave enters the cavity of the outer shell from the micro-pore array, it diffuses along the inclined panels of the first bending path control plate assembly and the second bending path control plate assembly, and then splits into two paths, entering the channels of the first bending path control plate assembly and the second bending path control plate assembly respectively, and finally falling into the semi-enclosed space formed by the two bending path control plate assemblies and the perforated plate.

[0048] The perforated plate, the various plates that make up the bending path control plate assembly, and the outer shell are made of engineering plastics or lightweight metals such as aluminum and stainless steel, and are structurally fixedly connected by structural brazing (or adhesive bonding).

[0049] Example 1:

[0050] This embodiment is a single-unit structure with external dimensions W, L, and H of 51.5mm, 33.5mm, and 53.5mm, respectively. The thickness of the partitions in the lower panel 2, left frame 3, right frame 4, front frame 5, rear frame 6, first bending path control plate assembly 8, and second bending path control plate assembly 10 is 1mm. The dimensions W and L of the perforated plate 1 and lower panel 2 are 51.5mm and 33.5mm, respectively. The dimensions L and H of the left frame 3 and right frame 4 are 33.5mm and 53.5mm, respectively. The dimensions W and H of the front frame 5 and rear frame 6 are 51.5mm and 53.5mm, respectively. The lengths of the first partition 7, first horizontal plate 8-Ⅲ, second partition 9, and second horizontal plate 10-Ⅲ are all 5mm. The lengths of the first vertical plate 8-Ⅱ and second vertical plate 10-Ⅱ are all 4mm. The lengths of the first inclined plate 8-Ⅰ and second inclined plate 10-Ⅰ are all 12.65mm. The value of θ is 28.31°. H1 and H3 are both 40mm, H2 and H4 are both 4mm, w1 and w3 are both 2mm, w2 and w4 are both 2mm, the diameter of the micro-perforations on the perforated plate 1 is 0.5mm, the perforation rate is 7%, and the plate thickness is 0.5mm. In this embodiment, compared with the existing three-channel constant cross-section bent superstructure (the structure in the paper "Low-frequency sound absorption of hybrid absorber based on micro-perforated panel and coiled-up channels"), the sound absorption peak value is reduced from 454Hz to 432Hz, the sound absorption peak value shifts to lower frequencies, and the relative bandwidth (the ratio of the difference between the two frequencies at the half maximum of the absorption coefficient to the peak frequency) is increased from 56.38% to 79.86%, thus broadening the sound absorption bandwidth.

[0051] Example 2:

[0052] This embodiment consists of two single-unit structures extending along the x-direction, designated Unit-1 and Unit-2, respectively. The difference lies in the sub-millimeter to millimeter-level perforations 11 on the perforated plate 1 of the two structures. Specifically, the sub-millimeter to millimeter-level perforations 11 in Unit-1 have the following dimensions: diameter 0.45mm, perforation rate 5%, and plate thickness 0.5mm; while the sub-millimeter to millimeter-level perforations 11 in Unit-2 have the following dimensions: diameter 0.8mm, perforation rate 2.5%, and plate thickness 0.5mm. Results show two absorption peaks at 406Hz and 432Hz, and a sound absorption coefficient >0.5 within the 320Hz to 752Hz range, enhancing sound absorption in the mid-to-low frequency range.

[0053] As can be seen from the embodiments, the present invention has a low peak sound absorption frequency and a wide sound absorption bandwidth, and has broad application prospects in sound absorption and noise reduction engineering.

[0054] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A low-frequency broadband sound-absorbing device based on a perforated plate structure with a sloping bent cavity, characterized in that: It includes several individual structures connected in sequence; each individual structure includes an outer shell, a perforated plate, and multiple bending path control plate assemblies. The outer shell is composed of a lower panel and a surrounding frame; a perforated plate is fixedly installed on the top of the outer shell; a micro-pore array consisting of several uniformly arranged sub-millimeter to millimeter-sized circular holes is opened in the middle of the perforated plate; in the internal cavity of the outer shell, multiple bending path control plate assemblies are evenly arranged around the micro-pore array. The bending path control plate assembly includes a partition, an inclined plate, a vertical plate, and a horizontal plate. One end of the inclined plate is fixed to a perforated plate and located on one side of the micro-hole array. The inclined plate is biased towards the outer shell frame plate on the same side, forming an angle θ with the perforated plate. The value of angle θ is 24.62°~71.05°. The other end of the inclined plate is connected to one end of the vertical plate, which is perpendicular to the perforated plate. The other end of the vertical plate is connected to one end of the horizontal plate, which is parallel to the perforated plate and points towards the outer shell frame plate on the same side, with a gap between the horizontal plate and the outer shell frame plate. A partition is located between the horizontal plate and the perforated plate. The partition is parallel to the perforated plate, and one end of the partition is fixed to the outer shell frame plate, while the other end of the partition has a gap with the vertical plate. The thickness of the perforated plate is 0.5mm~2mm; the thickness of the lower panel and the surrounding frame plates is 0.5mm~1.5mm; the length of the partition and the horizontal plate is 5mm~10mm, and the length of the vertical plate is 3mm~4mm; the length of the inclined panel is 9.6mm~35.94mm; the distance between the horizontal plate and the lower panel of each bending path control plate assembly is equal, all being 10mm~40mm; the gap between the horizontal plate and the outer shell frame plate on each side of each bending path control plate assembly is equal, all being 2mm~4mm; the gap between the partition and the vertical plate in each bending path control plate assembly is equal, all being 2mm~4mm; the distance between the partition and the horizontal plate in each bending path control plate assembly is equal, all being 2mm~4mm. When the sound wave enters the cavity of the outer shell from the micro-pore array, it diffuses and is blocked by the cavity wall, and then enters the bending path control plate assembly. Part of the sound wave energy is dissipated by friction of the micro-pore array. The bending path control plate assembly increases the propagation path of the sound wave, increases the sound energy loss, and causes the absorption peak to shift to lower frequencies.

2. The low-frequency broadband sound-absorbing device based on a perforated plate structure with a sloping bent cavity according to claim 1, characterized in that: The diameter of the sub-millimeter to millimeter-level circular holes is 0.3mm to 0.8mm.

3. The low-frequency broadband sound-absorbing device based on a perforated plate structure with a sloping bent cavity according to claim 2, characterized in that: The distance between the sub-millimeter to millimeter-sized circular holes is 3.53mm to 5.03mm.

4. The low-frequency broadband sound-absorbing device based on a perforated plate structure with a sloping bent cavity according to claim 3, characterized in that: The total perforation rate of the perforated plate is 2% to 10%.

5. The low-frequency broadband sound-absorbing device based on a perforated plate structure with a sloping bent cavity according to claim 1, characterized in that: When the sound wave enters the cavity of the outer shell from the micro-pore array, it diffuses along the inclined panels of each bending path control plate assembly, then splits into multiple paths, entering the channels of each bending path control plate assembly respectively, and finally falls into the semi-enclosed space formed by each bending path control plate assembly and the perforated plate.

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