A deep subwavelength low-frequency sound absorption unit, sound absorption structure and sound absorption method

Abstract

The present invention discloses a deep subwavelength low-frequency sound absorption unit, a sound absorption structure, and a sound absorption method, which relate to the field of noise control. The sound absorption unit includes a top cover and a bottom cover, the top cover includes a top plate and a perforation, the bottom cover includes a bottom plate and an outer wall plate, the top of the outer wall plate is sealed and fixed to the top plate, a plurality of first annular baffles are arranged on the bottom surface of the top plate outside the perforation, and a first horizontal channel is formed by a spacing between the bottom surface of the first annular baffle and the top surface of the bottom plate; a plurality of second annular baffles are arranged on the top surface of the bottom plate inside the outer wall plate, and a second horizontal channel is formed by a spacing between the top surface of the second annular baffle and the bottom surface of the top plate; the first annular baffles are arranged with the second annular baffles and the outer wall plate in an staggered manner to form a vertical channel; the first horizontal channel is connected to the second horizontal channel and the vertical channel to form an annular folded channel. The present invention achieves the advantages of low-frequency and high-efficiency sound absorption, compact structure, and lightweight through the innovative design of the annular folded channel.

Description

Technical Field

[0001] The present invention relates to the field of noise control, and in particular to a deep subwavelength low-frequency sound absorption unit, a sound absorption structure and a sound absorption method. Background Art

[0002] A microperforated plate is a resonant sound-absorbing unit. A resonant unit can be considered a mass-spring oscillator system, with the holes and surrounding air acting as the acoustic mass, and the cavity containing the air acting as the acoustic volume. When the frequency of the noise approaches the unit's natural frequency, the sound waves cause the mass-spring oscillator system to resonate, dissipating the acoustic energy. Due to its excellent sound absorption properties, adjustable absorption bandwidth, high durability, and strong structural strength, it has garnered considerable attention and development in the field of noise suppression. According to the microperforated plate theory proposed by renowned Chinese acoustician Ma Dayou, traditional perforated and microperforated plate structures require a cavity depth of approximately one-quarter wavelength for low-frequency sound absorption, occupying a significant amount of space and making it difficult to meet the requirements of small size and lightweight in practical applications. Therefore, a deep subwavelength low-frequency sound absorption unit based on an annular zigzag channel and a perforated plate was designed to address this issue. Summary of the Invention

[0003] To address the shortcomings of existing technologies, the present invention aims to provide a deep subwavelength, low-frequency sound absorption unit, sound absorption structure, and sound absorption method based on an annular zigzag channel and a perforated plate. Through its innovative annular zigzag channel design, the present invention achieves high-efficiency low-frequency sound absorption, a compact structure, and lightweight performance advantages. This provides a new solution for noise control, demonstrating significant technical advantages and application potential.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] The present invention provides a deep subwavelength low-frequency sound absorption unit, which includes a top cover and a bottom cover. The top cover includes a top plate and a perforation located in the center of the top plate. The bottom cover includes a bottom plate and an outer wall plate fixed to the edge of the bottom plate. The top of the outer wall plate is sealed and fixed to the top plate. A plurality of first annular baffles are arranged at intervals on the bottom surface of the top plate outside the perforation. A first horizontal channel is formed by a spacing between the bottom surface of the first annular baffle and the top surface of the bottom plate; a plurality of second annular baffles are arranged at intervals on the top surface of the bottom plate on the inner side of the outer wall plate. A second horizontal channel is formed by a spacing between the top surface of the second annular baffle and the bottom surface of the top plate; the first annular baffles, the second annular baffles and the outer wall plate are arranged in an alternating manner to form a vertical channel; the first horizontal channel, the second horizontal channel and the vertical channel are connected to each other to form an annular flexural channel.

[0006] Preferably, the first horizontal channel, the second horizontal channel and the vertical channel have the same channel width.

[0007] Further preferably, the diameter of the perforation is the same as the channel width of the annular folding channel.

[0008] Preferably, the top plate, bottom plate, outer wall plate, first annular partition plate and second annular partition plate have the same thickness.

[0009] Further preferably, the thickness of the top plate, the bottom plate, the outer wall plate, the first annular partition plate and the second annular partition plate is 1 / 4 of the channel width of the annular folding channel.

[0010] Preferably, the number of the first annular baffles differs from the number of the second annular baffles by one.

[0011] Preferably, the first annular partition plate and the second annular partition plate are both concentrically arranged with the through hole as the center.

[0012] Preferably, the top plate, bottom plate, outer wall plate, first annular partition plate and second annular partition plate are all made of rigid metal material.

[0013] The present invention also provides a sound absorbing structure, which includes a plurality of the sound absorbing units.

[0014] The present invention also provides a sound absorption method using the sound absorption structure, comprising the following steps:

[0015] Designing and determining the geometric dimensions of at least one sound absorbing unit based on one or more noise frequencies to be absorbed;

[0016] A plurality of sound absorbing units are arranged and combined to form a sound absorbing structure, the bottom plate is fixed in contact with a target sound absorbing object, and the perforations are directed toward the noise source to absorb the sound.

[0017] The working principle of the sound absorbing unit of the present invention is as follows:

[0018] When the present invention is used, the top cover end is aligned with the noise source, and the sound waves enter the annular folded channel behind the plate through the perforations on the top plate; the sound waves of a specific frequency are first absorbed by the perforations on the top plate through the thermoviscous dissipation effect, and then stimulate the air resonance in the annular folded channel and are absorbed in large quantities; the annular folded channel greatly extends the propagation path of the sound waves in the structure, causing the effective operating frequency of the structure to shift significantly to low frequencies, thereby achieving deep subwavelength low-frequency quasi-perfect sound absorption.

[0019] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0020] 1. By designing an annular folded channel, this invention effectively extends the propagation path of sound waves within the sound-absorbing structure without increasing the structure's external dimensions, thereby achieving low-frequency sound absorption at deep subwavelength scales. This overcomes the problem of traditional micro-perforated plate sound-absorbing units requiring a large cavity depth, making the sound-absorbing structure more compact and easier to use in space-constrained environments. The design of the annular folded channel enables the present invention to achieve miniaturization and lightweighting while maintaining efficient sound absorption performance, which is particularly important for applications requiring weight and volume control, such as aerospace and automotive.

[0021] 2. The perforated design not only serves as a channel for sound waves to enter, but also directly absorbs some sound energy through the thermoviscous dissipation effect. This mechanism is particularly important for low-frequency sound absorption, further improving overall sound absorption performance. By adjusting the perforation diameter and the length and number of annular baffles, the location and width of the sound absorption peak can be precisely controlled, achieving efficient absorption of specific low-frequency bands while maintaining a wide sound absorption bandwidth, thereby improving sound absorption efficiency and applicability.

[0022] 3. The sound-absorbing unit is preferably made of rigid metal, ensuring structural strength and durability while also facilitating large-scale production and processing. Furthermore, the choice of material and symmetrical structural design facilitate standardized production and reduce manufacturing costs.

[0023] 4. All structures of the present invention are centrally symmetrical, simple in structure, have a wide range of application scenarios, and are conducive to production and processing.

[0024] In summary, the present invention achieves structural miniaturization and lightweighting without sacrificing sound absorption performance through its innovative annular folded channel design, providing a new solution for the field of noise control, especially in situations where space is limited or there are special requirements for sound absorption efficiency, showing significant technical advantages and application potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the three-dimensional structure of the sound absorbing unit of the present invention.

[0026] Figure 2 It is a schematic diagram of the internal structure of the top cover of the present invention.

[0027] Figure 3 It is a schematic diagram of the internal structure of the bottom cover of the present invention.

[0028] Figure 4 It is a schematic cross-sectional structural diagram of the sound absorbing unit of the present invention.

[0029] Figure 5 It is a graph showing the sound absorption coefficient of the sound absorption unit of the present invention changing with frequency.

[0030] In the figure: 1. Top cover; 11. Perforation; 12. Top plate; 13. First annular partition; 2. Bottom cover; 21. Bottom plate; 22. Second annular partition; 23. Outer wall plate; 3. Annular folding channel; 31. First horizontal channel; 32. Second horizontal channel; 33. Vertical channel. DETAILED DESCRIPTION

[0031] To help those skilled in the art better understand the technical solutions of the present invention, the preferred embodiments of the present invention are described below in conjunction with specific examples. However, it should be understood that the drawings are for illustrative purposes only and are not to be construed as limiting this patent. To better illustrate this embodiment, some components in the drawings may be omitted, enlarged, or reduced, and do not represent the dimensions of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions may be omitted in the drawings. The positional relationships described in the drawings are for illustrative purposes only and are not to be construed as limiting this patent.

[0032] The present invention will be further described in detail below with reference to the accompanying drawings to illustrate a deep subwavelength low-frequency sound absorption unit, a sound absorption structure and a sound absorption method.

[0033] like Figure 1-4 As shown, the present invention provides a deep subwavelength low-frequency sound absorption unit, the structure of which mainly includes a top cover 1 and a bottom cover 2. The top cover 1 is composed of a top plate 12 and a perforation 11 located in the center of the top plate 12. The perforation 11 serves as a channel for sound waves to enter. The bottom cover 2 is composed of a bottom plate 21 and an outer wall plate 23 fixed to the edge of the bottom plate 21. The top of the outer wall plate 23 is sealed and fixed to the top plate 12 to ensure that sound waves propagate within the structure. The top plate 12 and the bottom plate 21 are both circular, and their projections on the plane coincide. The center of the perforation 11 coincides with the center of the top plate 12 to dissipate sound energy through the thermoviscous effect.

[0034] To achieve low-frequency sound absorption, the present invention includes multiple first annular baffles 13 spaced apart on the bottom surface of the top plate 12 outside the perforations 11. These baffles form a first horizontal channel 31 at a predetermined distance from the bottom plate 21. Simultaneously, multiple second annular baffles 22 are spaced apart on the top surface of the bottom plate 21 inside the outer wall plate 23. These baffles form a second horizontal channel 32 with the top plate 12. The first annular baffles 13 are staggered with the second annular baffles 22 and the outer wall plate 23 to form vertical channels 33. These horizontal and vertical channels 33 are interconnected, forming the annular folded channel 3.

[0035] To optimize sound absorption, the present invention employs a specific design for channel width. Specifically, the first horizontal channel 31, the second horizontal channel 32, and the vertical channel 33 are all designed to have the same width. This design facilitates uniform propagation and resonance of sound waves within the channels. Furthermore, the diameter of the perforations 11 is designed to be the same as the channel width to ensure smooth entry of sound waves into the annular zigzag channel 3.

[0036] In terms of material selection, the present invention preferably uses rigid metal for the top plate 12, bottom plate 21, outer wall plate 23, first annular baffle 13, and second annular baffle 22. This material not only provides sufficient strength and durability but also facilitates large-scale production and processing. Furthermore, the centrally symmetrical design of all structures facilitates standardized production and reduces manufacturing costs.

[0037] The present invention also provides a sound absorbing structure composed of multiple sound absorbing units and a sound absorbing method thereof. Specifically, sound absorbing structures of different sizes and shapes can be constructed according to actual needs, and multiple sound absorbing units can be arranged and combined according to a certain pattern.

[0038] When using the sound-absorbing structure for sound absorption, the base plate 21 is fixed in contact with the target object, and the perforations 11 are oriented toward the noise source to absorb sound. After sound waves pass through the perforations 11 and enter the annular zigzag channel 3, they resonate within the channel and are largely absorbed. The design of the annular zigzag channel 3 significantly extends the sound wave propagation path within the structure, enabling the structure to achieve low-frequency sound absorption at deep subwavelength scales. Furthermore, the thermoviscous dissipation effect of the perforations 11 directly absorbs some sound energy, further enhancing overall sound absorption performance.

[0039] The present invention will provide a set of structural parameters and material parameters to verify the effectiveness of the present invention. The following is a specific design example:

[0040] (1) The overall structure radius R of the sound absorbing unit is 50 mm, and the thickness H is 22 mm.

[0041] (2) The diameter d of the perforation on the top plate is 4 mm.

[0042] (3) The thickness t of the top plate and the bottom plate is 1 mm, and the thickness b of the outer wall plate, the first annular baffle and the second annular baffle is 1 mm; the number of the first annular baffles is 5, and the number of the second annular baffles is 4.

[0043] (4) The height H1 of the folded channel is 20 mm, and the width s of the first and second horizontal channels and the width w of the vertical channel are both 4 mm.

[0044] (5) The multi-physics coupling analysis software COMSOL Multiphysics was used to construct the sound absorption model. The present invention only considers the vertical incidence of plane waves. The incident sound field is established above the sound absorption unit. Correspondingly, the top plate, bottom plate, first annular baffle, second annular baffle, outer wall plate, perforation, and folded channel in the sound absorption unit area are constructed one by one. Among them, the incident sound field is defined as the pressure acoustic domain, the perforation and folded channel are defined as the thermoviscous acoustic domain, and the top plate, bottom plate, first annular baffle, second annular baffle, and outer wall plate are defined as the solid mechanics domain.

[0045] (6) The top of the incident sound field is set as plane wave radiation, and the plane wave is incident vertically on the sound absorbing unit. The sound wave transmission of the sound absorbing unit is ignored, and the bottom of the base plate and the outer side of the outer wall plate are set as fixed constraints.

[0046] (7) The top cover and bottom cover are made of structural steel, and its elastic modulus is E=210×10 9 Pa, density ρ1=7850kg / m 3 , Poisson's ratio υ1 = 0.3; the incident sound field and the folded channel material are selected as air, and its density ρ2 = 1.21 kg / m 3 , speed of sound c=343m / ,s dynamic viscosity η=1.82×10 -5 Pa·s, thermal conductivity κ=0.0258W·m -1 ·K -1 , constant pressure heat capacity C p =1005.42 J·kg -1 ·K -1 , specific heat rate

[0047] (8) The sound absorption coefficient can be obtained by solving the finite element model using COMSOL Multiphysics software, and the calculated sound wave frequency range is 100 Hz-300 Hz.

[0048] like Figure 5 As shown, the sound absorption coefficient of the sound absorbing unit designed in the present invention reaches 0.96 at 162 Hz, and the thickness of the entire structure is only 1 / 96 of the wavelength corresponding to this frequency, which has excellent deep subwavelength low-frequency sound absorption capability.

[0049] In summary, reducing the thickness of low-frequency sound absorption units has always been a difficult problem for sound absorption units. The present invention introduces an annular folded channel into the perforated plate, which greatly extends the propagation path of the sound wave and significantly shifts the sound absorption peak toward low frequencies. This overcomes the defect of traditional perforated plate structures that require the thickness to reach 1 / 4 of the wavelength corresponding to the operating frequency. As a result, the present invention has excellent low-frequency sound absorption performance, a simple structure, and is easy to manufacture.

[0050] According to the description and drawings of the present invention, those skilled in the art can easily manufacture or use the deep subwavelength low frequency sound absorbing unit of the present invention, and can produce the positive effects described in the present invention.

[0051] Unless otherwise specified, in the present invention, if there are terms such as "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicating orientation or positional relationships, they are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the orientation or positional relationships in the present invention are only used for illustrative purposes and cannot be understood as limiting this patent. For ordinary technicians in this field, they can understand the specific meanings of the above terms in conjunction with the drawings and according to specific circumstances.

[0052] Unless otherwise specified or limited, the terms "disposed," "connected," and "connected" in this disclosure should be interpreted broadly. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to direct connections, indirect connections through an intermediary, or internal connections between two components. Those skilled in the art will understand the specific meanings of these terms in this disclosure based on the specific circumstances.

[0053] The above is only a preferred embodiment of the present invention, but the present invention is not limited to the above specific embodiment. Those skilled in the art may make several modifications, supplements or use similar methods instead without departing from the principles of the present invention, and these should also be considered as the scope of protection of the present invention.

Claims

1. A deep subwavelength low-frequency sound absorbing unit, comprising a top cover (1) and a bottom cover (2), wherein the top cover (1) comprises a top plate (12) and a perforation (11) located at the center of the top plate (12), and the bottom cover (2) comprises a bottom plate (21) and an outer wall plate (23) fixed to the edge of the bottom plate (21), wherein the top of the outer wall plate (23) is sealed and fixed to the top plate (12), characterized in that: A plurality of first annular baffles (13) are arranged at intervals on the bottom surface of the top plate (12) outside the perforation (11), and a gap exists between the bottom surface of the first annular baffles (13) and the top surface of the bottom plate (21) to form a first horizontal channel (31); a plurality of second annular baffles (22) are arranged at intervals on the top surface of the bottom plate (21) inside the outer wall plate (23), and a gap exists between the top surface of the second annular baffles (22) and the bottom surface of the top plate (12) to form a second horizontal channel (32); the first annular baffles (13), the second annular baffles (22) and the outer wall plate (23) are arranged in an alternating manner to form a vertical channel (33); the first horizontal channel (31), the second horizontal channel (32) and the vertical channel (33) are connected to each other to form an annular folding channel (3).

2. The deep subwavelength low frequency sound absorbing unit according to claim 1, characterized in that: The first horizontal channel (31), the second horizontal channel (32) and the vertical channel (33) all have the same channel width.

3. The deep subwavelength low frequency sound absorbing unit according to claim 2, characterized in that: The diameter of the perforation (11) is the same as the channel width of the annular folding channel (3).

4. The deep subwavelength low frequency sound absorbing unit according to claim 1, characterized in that: The thicknesses of the top plate (12), the bottom plate (21), the outer wall plate (23), the first annular partition plate (13) and the second annular partition plate (22) are all the same.

5. The deep subwavelength low frequency sound absorbing unit according to claim 4, characterized in that: The thickness of the top plate (12), the bottom plate (21), the outer wall plate (23), the first annular partition plate (13) and the second annular partition plate (22) is 1 / 4 of the channel width of the annular folding channel (3).

6. The deep subwavelength low frequency sound absorbing unit according to claim 1, characterized in that: The number of the first annular partition (13) and the second annular partition (22) differs by one.

7. The deep subwavelength low frequency sound absorbing unit according to claim 1, characterized in that: The first annular partition plate (13) and the second annular partition plate (22) are both concentrically arranged with the through hole (11) as the center.

8. The deep subwavelength low frequency sound absorbing unit according to claim 1, characterized in that: The top plate (12), the bottom plate (21), the outer wall plate (23), the first annular partition plate (13) and the second annular partition plate (22) are all made of rigid metal.

9. A sound absorbing structure, characterized in that: The sound absorbing structure comprises a plurality of sound absorbing units according to any one of claims 1 to 8.

10. A sound absorption method using the sound absorption structure according to claim 9, characterized in that: The following steps are involved: Designing and determining the geometric dimensions of at least one sound absorbing unit based on one or more noise frequencies to be absorbed; A plurality of sound absorbing units are arranged and combined to form a sound absorbing structure, the bottom plate (21) is fixed in contact with a target sound absorbing object, and the perforation (11) is directed toward a noise source to absorb sound.

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