Bidirectional rough insertion tube type double-layer Helmholtz resonance sound absorption structure

Abstract

The invention discloses a bidirectional rough interpolation tube type double-layer Helmholtz resonance sound absorption structure, which adopts a porous material lining mode, and is integrally formed by a plurality of cells arranged according to a period. Each cell comprises a double-layer resonant cavity honeycomb, a bidirectional rough inner insertion pipe and a porous material thin layer. Wherein the honeycomb cavity and the bidirectional rough inner insertion tube are combined to form a double-layer Helmholtz resonant cavity through a welding or cementing process, and meanwhile, axial and circumferential roughness is introduced to the inner insertion tube, so that impedance matching with air is improved, and a sound absorption peak of the double-layer Helmholtz resonant cavity moves towards low frequency. Meanwhile, the honeycomb cavity is filled with the porous material thin layer, energy dissipation is enhanced, and the broadband sound absorption effect is improved. The noise reduction device is simple in structure and has abundant adjustable structure parameters so as to meet different noise reduction requirements.

Description

Technical Field

[0001] The invention belongs to the technical field of air sound absorption composite structures, and in particular relates to a bidirectional rough inner-insertion tube type double-layer Helmholtz resonance sound absorption structure. Background Art

[0002] Low-frequency broadband sound absorption is of vital research significance to noise reduction technologies in the fields of transportation, architectural acoustics, etc. The traditional Helmholtz resonance sound absorption structure is composed of a micro-perforated plate and an air back cavity. It achieves the effect of sound absorption and noise reduction through the vibration of sound waves in the cavity. It is widely used in theaters, conference rooms, car cabins and other places. However, the traditional micro-perforated plate structure has obvious limitations: in order to achieve effective absorption of lower frequency sound waves, the cavity volume needs to be increased, resulting in a significant increase in the mass and volume of the structure, which is not conducive to lightweight design and processing and manufacturing. At the same time, the regular cylindrical hole shape has low damping, making it difficult to widen the sound absorption bandwidth and improve low-frequency sound absorption performance. In addition, the traditional Helmholtz sound absorption structure can only produce good sound absorption performance near the resonant frequency, which limits the broadband sound absorption performance. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to address the deficiencies in the above-mentioned prior art and provide a bidirectional roughened inner-tube double-layer Helmholtz resonant sound absorption structure to solve the technical problems of poor low-frequency sound absorption performance and narrow effective sound absorption bandwidth of traditional sound absorption structures.

[0004] The present invention adopts the following technical solutions: A bidirectional rough inner-inserted double-layer Helmholtz resonant sound absorption structure includes a plurality of cells arranged in an array, each cell is provided with a double-layer resonant cavity honeycomb, the double-layer resonant cavity honeycomb is embedded with a bidirectional rough inner-inserted tube, and the inner cavity of the double-layer resonant cavity honeycomb is filled with a thin layer of porous material.

[0005] Furthermore, the inner wall radius of the bidirectional rough inner tube satisfies the following functional relationship:

[0006] in, is the inner wall radius of the bidirectional rough inner tube, is the axial coordinate along the opening direction, is the circumferential coordinate, is the equivalent radius of the bidirectional rough inner tube, is the axial relative roughness; is the axial wave number; is the circumferential relative roughness; Indicates the number of circumferential waves.

[0007] Furthermore, the bidirectional rough inner tube has a radius of 2 to 10 mm, a length of 5 to 30 mm, and a wall thickness of 0.5 to 3 mm.

[0008] Furthermore, the height of the porous material layer is 5 to 15 mm.

[0009] Furthermore, the height of the double-layer resonant cavity honeycomb is 10-40 mm, the diagonal length of the diamond-shaped interface of the double-layer resonant cavity honeycomb is 30-80 mm, and the wall thickness of the double-layer resonant cavity honeycomb is 0.5-2 mm.

[0010] Furthermore, the axial relative roughness of the bidirectional rough inner tube is 0.05-0.25, and the axial wave number is .

[0011] Furthermore, the bidirectional rough inner tube has a circumferential relative roughness of 0.05 to 0.25 and a circumferential wave number of 4 to 12.

[0012] Furthermore, the double-layer resonant cavity honeycomb and the bidirectional rough inner insert tube are both made of steel, alloy or composite material.

[0013] Furthermore, the double-layer resonant cavity honeycomb and the bidirectional rough inner tube are connected by gluing or welding.

[0014] Furthermore, the double-layer resonant cavity honeycomb, the bidirectional rough inner tube and the porous material thin layer are coaxially arranged.

[0015] Compared with the prior art, the present invention has at least the following beneficial effects: The present invention provides a bidirectional rough inner tube type double-layer Helmholtz resonant sound absorption structure. Under the excitation of sound waves of a specific frequency, the vibration speed of the air particles in the double-layer Helmholtz resonator intensifies, and violent friction occurs with the porous material layer, dissipating a large amount of sound energy. Due to the double-layer design, the coupling between the double-layer Helmholtz resonator and the porous material layer enhances the dissipation of the sound wave. At the same time, the introduction of the bidirectional rough inner tube improves the acoustic impedance characteristics of the overall structure and enhances the low-frequency sound absorption performance of the overall structure. During the propagation of sound waves, the friction and viscosity effects of the porous material skeleton can further dissipate sound energy and improve the broadband sound absorption performance of the structure. Compared with the traditional double-layer Helmholtz resonator, the introduction of the bidirectional rough inner tube improves the sound absorption performance of the structure, and by adjusting the roughness parameters, its sound absorption effect in the low-frequency band can be further enhanced.

[0016] Furthermore, the cavity of the present invention is made of hard materials such as structural steel, and the honeycomb wall thickness is 0.5 to 3 mm. The structure has good pressure resistance and is a load-bearing, lightweight and multifunctional structure.

[0017] Furthermore, the height of the double-layer resonant cavity honeycomb ranges from 10 to 40 mm, and the diagonal length of the honeycomb diamond interface ranges from 30 to 80 mm. The diagonal length and height of the honeycomb alter the volume of the cavity inside the cell, thereby changing the resonance characteristics and resonant frequency of the overall structure, thereby adjusting the sound absorption performance.

[0018] Furthermore, the radius of the bidirectional rough inner tube structure embedded in each layer of cavity is 2 to 10 mm, and the length is 5 to 30 mm. By changing the radius and length of the inner tube structure, the sound absorption coefficient and resonance frequency of the overall structure can be changed, thereby regulating the sound absorption performance.

[0019] Furthermore, the axial relative roughness of the bidirectional rough inner tube is 0.05-0.25, and the axial wave number is By changing the axial roughness parameters of the inner tube structure, the sound absorption coefficient and resonance frequency of the overall structure can be changed, thereby regulating the sound absorption performance.

[0020] Furthermore, the circumferential relative roughness of the bidirectional rough inner tube is 0.05-0.25, and the circumferential wave number is 4-12. By changing the circumferential roughness parameters of the inner tube structure, the sound absorption coefficient and resonance frequency of the overall structure can be changed, thereby regulating the sound absorption performance.

[0021] Furthermore, the height of the porous material layer is 5 to 15 mm. By changing the height of the porous material layer, the sound absorption coefficient and the resonance frequency of the overall structure can be changed, thereby regulating the sound absorption performance.

[0022] In summary, the present invention has excellent low-frequency broadband sound absorption performance and good pressure-bearing capacity; in terms of design, the structural parameters and material parameters are highly adjustable and can be selected according to actual working conditions, and has broad engineering application prospects.

[0023] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of a bidirectional roughened inner-tube double-layer Helmholtz sound-absorbing structure lined with porous material according to the present invention; Figure 2 It is the structural side view of the unit cell; Figure 3 is a cross-sectional view of a unit cell; Figure 4 This is a schematic diagram of a bidirectional rough inner tube structure; Figure 5 A comparison chart of the sound absorption coefficients of the sound absorption structure with bidirectional rough inner tubes, the sound absorption structure with smooth inner tubes, and the structure without inner lining porous material of the present invention; Among them: 1. Double-layer resonant cavity honeycomb; 2. Bidirectional rough inner tube 3. Porous material thin layer. DETAILED DESCRIPTION

[0025] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0026] In the description of the present invention, it should be understood that the terms "center," "longitudinal," "lateral," "up," "down," "front," "back," "left," "right," "vertical," "horizontal," "top," "bottom," "inside," "outside," "one side," "one end," and "one side" and the like, indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended only to facilitate the description of the present invention and simplify the description. They do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed, or operate in a specific orientation, and therefore should not be construed as limiting the present invention. Furthermore, in the description of the present invention, unless otherwise specified, "a plurality" means two or more.

[0027] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0028] It will be understood that when used in this specification and the appended claims, the terms “comprises” and “comprising” indicate the presence of described features, integers, steps, operations, elements and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.

[0029] It should also be understood that the terms used in the present specification are only for the purpose of describing particular embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms unless the context clearly indicates otherwise.

[0030] It should be further understood that the term "and / or" used in the present description and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

[0031] The accompanying drawings illustrate various schematic diagrams of structures according to embodiments disclosed herein. These figures are not drawn to scale; for clarity, some details are exaggerated and some details may be omitted. The shapes of the various regions and layers shown in the figures, as well as their relative sizes and positional relationships, are merely exemplary and may deviate in practice due to manufacturing tolerances or technical limitations. Those skilled in the art may design regions / layers with different shapes, sizes, and relative positions as needed.

[0032] The present invention provides a bidirectional rough inner-inserted double-layer Helmholtz resonant sound absorbing structure, such as Figure 1 As shown, it includes a double-layer resonant cavity honeycomb 1. The double-layer resonant cavity honeycomb 1 is a hollow structure. The cavity of the double-layer resonant cavity honeycomb 1 and the bidirectional rough inner tube 2 are connected by gluing or welding to form a Helmholtz resonant sound absorption structure. Both are made of metal or carbon fiber / glass fiber composite materials, and a thin layer of porous material 3 is fully filled into the upper cavity, close to the wall. The introduction of the bidirectional rough inner tube 2 not only connects the cavity with the outside air, but also has a regulating effect on the acoustic impedance of the overall structure due to its special configuration. By introducing a rough structure on the wall of the inner tube, the impedance matching with the air is improved, thereby improving the low-frequency sound absorption performance of the overall structure. This provides a compact and efficient innovative solution for low-frequency broadband noise control, and its scope of application can cover many important fields such as transportation and architectural acoustics.

[0033] The inner wall radius of the bidirectional rough inner tube (2) satisfies the following functional relationship:

[0034] in, is the inner wall radius of the bidirectional rough inner tube, is the axial coordinate along the opening direction, is the circumferential coordinate, is the equivalent radius of the bidirectional rough inner tube, is the axial relative roughness; is the axial wave number; is the circumferential relative roughness; Indicates the number of circumferential waves.

[0035] See also Figure 1 、 Figure 2 、 Figure 3 and Figure 4The present invention discloses a bidirectional roughened internally inserted double-layer Helmholtz resonant sound absorption structure comprising a plurality of cells, each of which comprises a double-layer resonant cavity honeycomb 1, a bidirectional roughened internally inserted tube 2, and a thin layer of porous material 3. The lower surface of the double-layer resonant cavity honeycomb 1 is fixed to the surface of an object requiring acoustic treatment. The interior of the double-layer resonant cavity honeycomb 1 is a double-layer cavity, with small holes formed on the upper surface of each cavity layer. The bidirectional roughened internally inserted tube is disposed within the small holes and connected to the cavity by gluing or welding. The upper cavity layer is filled with a thin layer of porous material 3 and connected to the cavity by gluing, forming a bidirectional roughened internally inserted double-layer Helmholtz resonant sound absorption structure.

[0036] The height of each cell is 20 to 60 mm.

[0037] The diamond diagonal of the double-layer resonant cavity honeycomb 1 is 30 to 80 mm, and the wall thickness is 0.5 to 2 mm.

[0038] The double-layer resonant cavity honeycomb 1 is made of hard materials such as steel, alloy, resin or composite materials. The use of hard materials ensures that the structure has a certain bearing capacity and is connected to the bidirectional rough inner tube 2 by gluing or welding.

[0039] The bidirectional rough inner insert tube 2 has a diameter of 2 to 10 mm and a length of 5 to 30 mm.

[0040] The axial relative roughness of the bidirectional rough inner tube 2 is 0.05-0.25, and the axial wave number is .

[0041] The bidirectional rough inner tube 2 has a circumferential relative roughness of 0.05 to 0.25 and a circumferential wave number of 4 to 12.

[0042] The porous material thin layer 3 is fully filled into the upper cavity, and the friction and viscosity effects of the porous material skeleton are used to dissipate the sound energy. The height is 5 to 15 mm.

[0043] The axes of the double-layer resonant cavity honeycomb 1, the bidirectional rough inner tube 2 and the porous material thin layer 3 coincide with each other.

[0044] The sound absorption performance of the bidirectional roughened inner-tube double-layer Helmholtz resonant sound absorption structure of the present invention is mainly determined by the structural dimensions and roughness parameters of the diamond honeycomb and the inner-tube, and the material parameters of the porous material, specifically including: The side lengths of the upper and lower honeycombs, the heights of the upper and lower cavities, the radius and length of the bidirectional roughened inner tubes, the axial relative roughness of the bidirectional roughened inner tubes, the axial wave number of the bidirectional roughened inner tubes, the circumferential relative roughness of the bidirectional roughened inner tubes, the circumferential wave number of the bidirectional roughened inner tubes, the height of the porous material layer, the material type of the porous material, the porosity of the porous material, the tortuosity factor of the porous material, the viscous characteristic length of the porous material, the thermal characteristic length of the porous material, and the static flow resistivity of the porous material. The load-bearing capacity is primarily determined by the dimensions of the cavities, including the diameter and height of the upper and lower cavities, and the thickness of the honeycomb walls. Because these structural and material parameters are adjustable, the sound absorption and load-bearing performance of the structure can be precisely adjusted.

[0045] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0046] Comparative Example 1 A sound-absorbing structure with a smooth inner tube was selected as comparative example 1.

[0047] Metal Steel: Density 7850 kg / m 3 , Young's modulus is 201 GPa, and Poisson's ratio is 0.33.

[0048] Air: Density 1.23 kg / m 3 , the speed of sound is 343 m / s.

[0049] Comparative structural dimensions: Total height of diamond honeycomb: H =43 mm.

[0050] The diagonal length of the rhombus section is: l 1=43mm, l 2=57mm Upper and lower wall thickness: t 1=1mm.

[0051] Side wall thickness: t 2=1.5mm.

[0052] Upper and lower inner tube diameters: d 1=6mm, d 2=12mm.

[0053] Neck length: l 1=6mm, l 2=9mm.

[0054] Neck wall thickness: t 3=1mm.

[0055] Comparative Example 2 A smooth inner-inserted double-layer Helmholtz resonance structure lined with porous material was selected as comparative example 2.

[0056] Metal Steel: Density 7850 kg / m 3 , Young's modulus is 201 GPa, and Poisson's ratio is 0.33.

[0057] Air: Density 1.23 kg / m 3 , the speed of sound is 343 m / s.

[0058] Porous materials: Porosity: , tortuosity factor: , viscosity characteristic length: , thermal characteristic length: , static flow resistance: .

[0059] Comparative structural dimensions: Total height of diamond honeycomb: H =43 mm.

[0060] The diagonal length of the rhombus section is: l 1=43mm, l 2=57mm Upper and lower wall thickness: t 1=1mm.

[0061] Side wall thickness: t 2=1.5mm.

[0062] Upper and lower inner tube diameters: d 1=6mm, d 2=12mm.

[0063] Neck length: l 1=6mm, l 2=9mm.

[0064] Neck wall thickness: t 3=1mm.

[0065] Example 1 A bidirectional rough inner-inserted double-layer Helmholtz resonance structure lined with porous material is selected as Example 1.

[0066] Among them, the axial relative roughness is 0.1, and the axial wave number is , the circumferential relative roughness is 0.1, and the circumferential wave number is 6.

[0067] Metal Steel: Density 7850 kg / m 3 , Young's modulus is 201 GPa, and Poisson's ratio is 0.33.

[0068] Air: Density 1.23 kg / m 3 , the speed of sound is 343 m / s.

[0069] Porous materials: Porosity: , tortuosity factor: , characteristic viscosity length: , thermal characteristic length: , static flow resistance: .

[0070] Example structure size: Total height of diamond honeycomb: H =43 mm.

[0071] The diagonal length of the rhombus section is: l 1=43mm, l 2=57mm Upper and lower wall thickness: t 1=1mm.

[0072] Side wall thickness: t 2=1.5mm.

[0073] Equivalent diameter of upper and lower inner tubes: d 1=6mm, d 2=12mm.

[0074] Neck length: l 1=6mm, l 2=9mm.

[0075] Neck wall thickness: t 3=1mm.

[0076] Porous material height: h p =10mm Example 2 A bidirectional rough inner-inserted double-layer Helmholtz resonant structure lined with porous material was selected as Example 2.

[0077] Among them, the axial relative roughness is 0.15, and the axial wave number is , the circumferential relative roughness is 0.15, and the circumferential wave number is 6.

[0078] Metal Steel: Density 7850 kg / m 3 , Young's modulus is 201 GPa, and Poisson's ratio is 0.33.

[0079] Air: Density 1.23 kg / m 3 , the speed of sound is 343 m / s.

[0080] Porous materials: Porosity: , tortuosity factor: , viscosity characteristic length: , thermal characteristic length: , static flow resistance: .

[0081] Example structure size: Total height of diamond honeycomb: H =43 mm.

[0082] The diagonal length of the rhombus section is: l 1=43mm, l 2=57mm Upper and lower wall thickness: t 1=1mm.

[0083] Side wall thickness: t 2=1.5mm.

[0084] Equivalent diameter of upper and lower inner tubes: d 1=6mm, d 2=12mm.

[0085] Neck length: l 1=6mm, l 2=9mm.

[0086] Neck wall thickness: t 3=1mm.

[0087] Porous material height: h p =10mm Both Example 1 and Example 2 use a sound-absorbing structure without a thin layer of porous material lining and a smooth inner tube sound-absorbing structure lined with porous material as control groups. The air parameters and total thickness remain consistent with the corresponding examples. The sound absorption coefficient of the structure at 0 to 1600 Hz is calculated using numerical simulation.

[0088] See also Figure 5 , which is a comparison of the simulated sound absorption coefficient curves of the two embodiments and the two control groups. The black solid line is the sound absorption coefficient curve of the double-layer Helmholtz resonance structure without a porous material lining; the black dashed line is the sound absorption coefficient curve of the smooth inner-inserted double-layer Helmholtz resonance structure with a porous material lining; the black dotted line is the sound absorption coefficient curve of the bidirectional rough inner-inserted double-layer Helmholtz resonance structure with a porous material lining, wherein the axial relative roughness is 0.1 and the axial wave number is , the circumferential relative roughness is 0.1, and the circumferential wave number is 6; the black dotted line is the sound absorption coefficient curve of the bidirectional rough inner tube double-layer Helmholtz resonant structure lined with porous material, among which the axial relative roughness is 0.15, and the axial wave number is , the circumferential relative roughness is 0.15, and the circumferential wave number is 6.

[0089] The sound-absorbing structure of the present invention has improved low-frequency sound absorption performance within a certain frequency range compared to the smooth inner tube sound-absorbing structure. The introduction of porous materials can effectively enhance the system damping and adjust the acoustic impedance matching, thereby achieving perfect broadband sound absorption. By introducing axial and circumferential roughness into the inner tube wall, the impedance matching between the sound-absorbing structure and the air is improved, so that the present structure achieves perfect low-frequency broadband sound absorption. The two peak frequencies of Example 1 shifted to low frequencies by 117 Hz and 156 Hz, respectively, and the two peak frequencies of Example 2 shifted to low frequencies by 174 Hz and 217 Hz, respectively. The following technical effects are achieved: 1. Excellent broadband sound absorption performance. The structure of the present invention can achieve an increase in the average sound absorption coefficient within a wide frequency range, and the peak sound absorption coefficient reaches above 0.99, showing excellent sound absorption performance.

[0090] 2. Excellent low-frequency sound absorption performance. The bidirectional roughened inner tube 2 of the present invention introduces axial roughness and circumferential roughness to improve impedance matching with air, and thus the peak frequency shifts significantly toward low frequencies compared to the original structure.

[0091] 3. Good load-bearing capacity. The double-layer resonant cavity honeycomb 1 is made of metal steel, which gives the structure a certain load-bearing capacity. The thickness of the structure is only 20 to 60 mm, making it a multifunctional structure with load-bearing, lightweight, sound absorption and noise reduction.

[0092] 4. Adjustable structural and material parameters. Changes in the structural parameters of the honeycomb and inner tube, the axial and circumferential roughness parameters of the bidirectional rough inner tube 2, and the material parameters of the porous material have a significant impact on the sound absorption performance of the structure and can be selected based on actual working conditions.

[0093] In summary, the bidirectional roughened, internally inserted, double-layer Helmholtz resonant sound absorption structure of the present invention exhibits excellent low-frequency, broadband sound absorption performance. The structural and material parameters offer significant tunability, allowing for selection based on actual operating conditions. This structure has broad engineering application prospects, providing a compact, efficient, and innovative solution for low-frequency, broadband noise control, encompassing a wide range of applications, including transportation and architectural acoustics.

[0094] The above content is only for explaining the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A bidirectional rough inner-insertion double-layer Helmholtz resonant sound absorption structure, characterized in that: The invention comprises a plurality of cells arranged in an array, each cell being provided with a double-layer resonant cavity honeycomb (1), the double-layer resonant cavity honeycomb (1) being embedded with a bidirectional rough inner tube (2), and the inner cavity of the double-layer resonant cavity honeycomb (1) being filled with a porous material thin layer (3).

2. The bidirectional rough inner-inserted double-layer Helmholtz resonant sound absorption structure according to claim 1, characterized in that: The inner wall radius of the bidirectional rough inner tube (2) satisfies the following functional relationship: in, is the inner wall radius of the bidirectional rough inner tube, is the axial coordinate along the opening direction, is the circumferential coordinate, is the equivalent radius of the bidirectional rough inner tube, is the axial relative roughness; is the axial wave number; is the circumferential relative roughness; Indicates the number of circumferential waves.

3. A bidirectional rough inner-inserted double-layer Helmholtz resonant sound-absorbing structure according to claim 1 or 2, characterized in that: The bidirectional rough inner tube (2) has a radius of 2 to 10 mm, a length of 5 to 30 mm, and a wall thickness of 0.5 to 3 mm.

4. The bidirectional rough inner-inserted double-layer Helmholtz resonant sound absorption structure according to claim 1, characterized in that: The height of the porous material thin layer (3) is 5 to 15 mm.

5. The bidirectional rough inner-tube double-layer Helmholtz resonant sound absorption structure according to claim 1, characterized in that: The height of the double-layer resonant cavity honeycomb (1) is 10 to 40 mm, the diagonal length of the rhombus interface of the double-layer resonant cavity honeycomb (1) is 30 to 80 mm, and the wall thickness of the double-layer resonant cavity honeycomb (1) is 0.5 to 2 mm.

6. The bidirectional rough inner-inserted double-layer Helmholtz resonant sound absorption structure according to claim 1, characterized in that: The axial relative roughness of the bidirectional rough inner tube (2) is 0.05-0.25, and the axial wave number is .

7. The bidirectional rough inner-inserted double-layer Helmholtz resonant sound absorption structure according to claim 1, characterized in that: The bidirectional rough inner tube (2) has a circumferential relative roughness of 0.05 to 0.25 and a circumferential wave number of 4 to 12.

8. The bidirectional rough inner-tube double-layer Helmholtz resonant sound absorption structure according to claim 1, characterized in that: The double-layer resonant cavity honeycomb (1) and the bidirectional rough inner insert tube (2) are both made of steel, alloy or composite material.

9. The bidirectional rough inner tube type double-layer Helmholtz resonant sound absorption structure according to claim 1, wherein the double-layer resonant cavity honeycomb (1) and the bidirectional rough inner tube (2) are connected by gluing or welding.

10. The bidirectional rough inner tube type double-layer Helmholtz resonant sound absorption structure according to claim 1, wherein the double-layer resonant cavity honeycomb (1), the bidirectional rough inner tube (2) and the porous material thin layer (3) are coaxially arranged.

Images