Ring-back curly type resonance sound absorption structure, composite noise reduction structure and sound absorption and noise reduction method

Abstract

The invention discloses a loopback curled resonance sound absorption structure, a composite noise reduction structure and a sound absorption and noise reduction method, belongs to the field of noise control, and aims to reduce the sound absorption area while meeting the 50Hz low-frequency noise reduction performance. Comprising a micro-perforated plate and a first curled channel, a second curled channel is inserted into the first curled channel, and an annular flow channel is defined by the inner side wall of the first curled channel and the outer side wall of the second curled channel; a sound wave inlet allowing sound to enter an inner cavity of the second curled channel is formed in the side wall of the second curled channel; and the sound transmission holes are communicated to the annular flow channel. According to the invention, targeted noise reduction can be carried out on 50Hz power frequency of most electrical and mechanical equipment; on the premise of the same sound absorption performance, the sound absorption area is reduced by 50%, and great popularization value is achieved in the application of noise reduction in a limited space; in the composite noise reduction structure, the loopback curled resonance sound absorption structure is placed on the first layer of the composite noise reduction structure, and the noise reduction performance is improved by 93% compared with a traditional noise reduction method.

Description

Technical Field

[0001] The invention belongs to the field of noise control, and specifically relates to a loop curling resonance sound absorption structure, a composite noise reduction structure and a sound absorption and noise reduction method. Background Art

[0002] With the development of social economy, people have gradually put forward higher requirements for the control of noise pollution. As a medical auxiliary equipment used in home environment, the noise level of household oxygen concentrator directly affects the user experience and quality of life. At present, the main noise reduction and sound absorption structure is a three-layer structure, namely the first layer, the second layer and the third layer, of which the first layer and the second layer are made of porous medium materials, and the third layer is made of polymer sound insulation felt. When sound waves enter the porous material, they are reflected and scattered between the pores of the porous medium material and gradually converted into heat energy. Because the pores of the porous medium are very small, the wavelength of low-frequency sound waves is long, and diffraction is easy to form, resulting in the high-frequency sound absorption capacity of the porous medium material being strong, while the low-frequency sound absorption capacity is weak. For most electrical and mechanical equipment, because the frequency of its 50Hz power frequency noise is too low, it is difficult to eliminate, which causes great trouble to people in application places with high noise reduction requirements. A large part of the noise frequency of the household oxygen concentrator is composed of 50Hz power frequency noise. Traditional noise reduction and sound absorption structures cannot meet the noise reduction requirements. Figure 1 The curled resonant sound-absorbing structure shown is suitable for 50Hz low-frequency noise reduction, which includes a micro-perforated plate 11 and a first curled channel 12, wherein the first curled channel 12 is a hollow cavity structure with a closed periphery; the micro-perforated plate 11 covers the first curled channel 12, and a sound-permeable hole 111 is provided on the micro-perforated plate 11. After the sound wave enters the first curled channel 12 through the sound-permeable hole 111 provided on the micro-perforated plate 11, it moves along the tortuous air flow channel in the first curled channel 12, and forms a standing wave during the movement, thereby consuming energy to achieve the purpose of low-frequency noise reduction. However, its low-frequency noise reduction performance is subject to the length of the air flow channel inside the sound-absorbing structure. The longer the air flow channel, the better the low-frequency noise reduction performance. However, the longer the air flow channel, the larger the sound absorption area is usually. However, the noise reduction space inside the oxygen concentrator is limited, so the above-mentioned curled resonant sound-absorbing structure is quite limited in the use of limited noise reduction space such as a household oxygen concentrator. Reducing the noise of home oxygen concentrators can improve user comfort and meet users' needs for a quiet environment. With the application of such technology, it is inevitable to explore a noise reduction structure that can not only meet the 50Hz low-frequency noise reduction performance but also reduce the sound absorption area. Summary of the invention

[0003] The object of the present invention is to provide a composite noise reduction structure and a sound absorption and noise reduction method thereof, which can meet the 50Hz low-frequency noise reduction performance while reducing the sound absorption area.

[0004] The technical solution adopted by the present invention is: a loop-curled resonant sound-absorbing structure, including a micro-perforated plate and a first curled channel, the first curled channel is a hollow cavity structure with a closed periphery; the micro-perforated plate covers the first curled channel, and sound-permeable holes are arranged on the micro-perforated plate; it also includes a second curled channel, the second curled channel is a hollow cavity structure with a closed periphery; the second curled channel is inserted into the first curled channel, and an annular flow channel is formed by the inner wall of the first curled channel and the outer wall of the second curled channel; a sound wave inlet for allowing sound to enter the inner cavity of the second curled channel is arranged on the side wall of the second curled channel; the sound-permeable holes pass through to the annular flow channel; and, along the extension direction of the flow channel in the second curled channel, the sound wave inlet is located at the head end of the second curled channel.

[0005] Furthermore, the sound-permeable holes are circular or square.

[0006] Furthermore, the boundary of the micro-perforated plate is a hard sound field boundary.

[0007] Furthermore, the first curled channel is a curled channel formed by a combination of hard sound field boundary walls.

[0008] Furthermore, the first curly passage comprises a transverse partition, a longitudinal partition and a first square outer frame which surrounds the first outer frame, wherein the transverse partition and the longitudinal partition are arranged in the first outer frame; a tortuous air flow passage is formed by the transverse partition, the longitudinal partition and the inner side wall of the first outer frame;

[0009] The second curling channel includes a second outer frame adapted to the first outer frame, and the side walls of the second outer frame are provided with inwardly recessed grooves corresponding to the transverse partition and the longitudinal partition; the second outer frame is inserted into the first outer frame, and the transverse partition and the longitudinal partition are inserted into the corresponding grooves.

[0010] The composite noise reduction structure is composed of a first layer, a second layer and a third layer, wherein the second layer is a porous medium material, the third layer is a polymer sound insulation felt, and the first layer is a loop curling resonant sound absorption structure.

[0011] Furthermore, the porous medium material has a porosity of 30%-90%, a pore size of 0.1 μm-2 mm, and an irregular three-dimensional interlaced structure in the pore network morphology.

[0012] Furthermore, the density of the polymer sound insulation felt is 1500kg / m 3 -2500kg / m 3 , thickness range is 1mm-5mm.

[0013] In the sound absorption and noise reduction method of the above-mentioned composite noise reduction structure, the sound wave of the noise source enters the loop curled resonant sound absorption structure for processing and becomes the second noise sound wave, the second noise sound wave enters the second layer of porous medium material for processing and becomes the third noise sound wave, the third noise sound wave is processed by the third layer of polymer sound insulation felt to isolate medium and high frequency noise, the sound wave reflected by the polymer sound insulation felt returns to the second layer of porous medium material for processing, and the third transmitted sound wave is transmitted by the polymer sound insulation felt.

[0014] The sound absorption and noise reduction method, the process of the noise source sound wave entering the first curled channel is: the noise source sound wave enters the annular flow channel between the first curled channel and the second curled channel from the sound-transmitting holes on the micro-perforated plate, moves along the annular flow channel to the end, and enters the second curled channel from the sound wave inlet of the second curled channel at the end.

[0015] The beneficial effects of the present invention are as follows: the looped curled resonant sound absorbing structure disclosed in the present invention can reduce the noise of 50 Hz power frequency of most electrical and mechanical equipment in a targeted manner;

[0016] A loop flow channel is formed by arranging a second curling channel in the first curling channel, so that the propagation path of the sound wave in the loop curling resonant sound absorbing structure is longer, so that the sound absorbing area is reduced by 50% under the premise of the same sound absorbing performance, which has great promotion value in the noise reduction application of limited space;

[0017] In the composite noise reduction structure, the loop-curled resonant sound-absorbing structure is placed on the first layer of the composite noise reduction structure. Since the resonant sound-absorbing structure is usually composed of a hard sound field boundary wall, it also has a certain isolation effect on the sound waves of the noise source. Compared with traditional noise reduction methods, the noise reduction performance is improved by 93%. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of a traditional curled resonant sound absorbing structure;

[0019] Figure 2 This is a schematic diagram of the loop-curled resonant sound-absorbing structure of the present invention;

[0020] Figure 3 It is a cross-sectional view of the loop-curled resonant sound-absorbing structure of the present invention;

[0021] Figure 4 A schematic diagram showing the comparison of the sound absorption coefficients of the loop-curled resonant sound absorption structure and the traditional curled resonant sound absorption structure in the noise reduction application for 50Hz industrial frequency noise;

[0022] Figure 5 It is the 1 / 3 octave noise spectrum of the original noise;

[0023] Figure 6A comparison chart of the sound absorption coefficients of the porous medium material of the conventional method and the porous medium material of the present invention;

[0024] Figure 7 It is the 1 / 3 octave transmission loss spectrum of the loop curled sound absorbing structure after A-weighting correction;

[0025] Figure 8 This is a 1 / 3 octave noise spectrum diagram after noise reduction by the traditional noise reduction method in Comparative Example 2;

[0026] Fig. 9 This is a 1 / 3 octave noise spectrum diagram after noise reduction in Example 1 of the present invention;

[0027] Fig.10 This is a schematic diagram of noise reduction of the composite noise reduction structure disclosed in the present invention.

[0028] In the figure, there is a loop-curled resonant sound-absorbing structure 1; a porous medium material 2; a polymer sound insulation felt 3; a micro-perforated plate 11; a sound-permeable hole 111; a first curled channel 12; a second curled channel 13; an annular flow channel 14; a transverse partition 121, a longitudinal partition 122, a first outer frame 123; a sound wave inlet 131; a second outer frame 132; and a groove 133. DETAILED DESCRIPTION

[0029] The present invention is further described below in conjunction with the accompanying drawings and embodiments:

[0030] In the present invention, the terms "inside", "outside", "top", "bottom", "lateral", "longitudinal" and the like indicate directions or positional relationships based on the attached Figure 2 The orientation or positional relationship shown is only for the convenience of describing the present invention, and does not indicate or imply that the device or element must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention.

[0031] Loop-curled resonant sound-absorbing structure, such as Figure 2 and Figure 3As shown, it includes a micro-perforated plate 11 and a first curled channel 12, the first curled channel 12 is a hollow cavity structure with a closed periphery; the micro-perforated plate 11 covers the first curled channel 12, and the micro-perforated plate 11 is provided with a sound-permeable hole 111; it also includes a second curled channel 13, the second curled channel 13 is a hollow cavity structure with a closed periphery; the second curled channel 13 is inserted into the first curled channel 12, and is surrounded by the inner wall of the first curled channel 12 and the outer wall of the second curled channel 13 to form an annular flow channel 14; a sound wave inlet 131 for allowing sound waves to enter the inner cavity of the second curled channel 13 is provided on the side wall of the second curled channel 13; the sound-permeable hole 111 passes through the annular flow channel 14; and, along the extension direction of the flow channel in the second curled channel 13, the sound-permeable hole 111 corresponds to the end position of the second curled channel 13, and the sound wave inlet 131 is located at the head end position of the second curled channel 13.

[0032] The incident sound wave enters the annular flow channel 14 formed by the inner wall of the first curled channel 12 and the outer wall of the second curled channel 13 through the sound-transmitting hole 111 on the micro-perforated plate 11, moves along the annular flow channel 14 to the sound wave inlet 131 of the second curled channel 13, enters the second curled channel 13 through the sound wave inlet 131 of the second curled channel 13, and reaches the end of the second curled channel 13 after consuming energy through the curled channel. Since the sound wave forms a standing wave in the annular flow channel 14 and the second curled channel 13, the incident sound wave of 50 Hz can be absorbed according to the resonance effect of the material, thereby achieving the purpose of noise reduction.

[0033] A tortuous air flow channel is formed in the second curled channel 13, one end of the air flow channel is the head end, which is also the end where the sound wave inlet 131 is located, and the other end is the end, which is in a closed state. After the sound wave enters through the sound wave inlet 131, a standing wave is formed in the second curled channel 13. The sound wave inlet 131 is located at the head end of the second curled channel 13, so after the sound wave enters the second curled channel 13 through the sound wave inlet 131, it will move toward the end of the second curled channel 13.

[0034] Compared with the traditional curled resonant sound absorbing structure, in this embodiment, after the sound wave reaches the sound wave entrance 131 in the first curled channel 12, it continues to enter the second curled channel 13, and moves from the sound wave entrance 131 at the head end of the second curled channel 13 to the end, and the movement path is extended, which is conducive to effective energy consumption.

[0035] The micro-perforated plate 11 is a thin plate through which incident sound waves enter the sound absorbing unit. Its thickness is in the millimeter or sub-millimeter level. It is generally made of 3D printing materials with high density such as photosensitive resin, epoxy resin, or acrylic plate, etc., to ensure the hard sound field characteristics of the boundary of the micro-perforated plate 11. The sound-transmitting holes 111 on the micro-perforated plate 11 are the medium for the incident sound waves to enter the sound absorbing unit. The size is generally in the millimeter or sub-millimeter level; the shape is square or round.

[0036] The first curled channel 12 is a tortuous channel formed by a combination of materials having hard sound field boundary characteristics, and the boundary thickness is in the millimeter level. It is generally made of high-density 3D printing materials such as photosensitive resin, epoxy resin, or acrylic plates.

[0037] The second curled channel 13 is a structure that extends the air flow channel during the sound absorption process. It is a zigzag channel formed by a combination of materials with hard sound field boundary characteristics. It has a thickness of millimeters and a shape that matches the shape of the first curled channel 12. It is generally made of high-density 3D printing materials such as photosensitive resin, epoxy resin, or acrylic panels.

[0038] Figure 2 One of the specific structures of the first curling channel 12 and the second curling channel 13 is disclosed in FIG.

[0039] That is, the first curling channel 12 includes a transverse partition 121, a longitudinal partition 122 and a first square outer frame 123 that surrounds the first outer frame 123. The transverse partition 121 and the longitudinal partition 122 are arranged in the first outer frame 123, and a tortuous air flow channel is formed by the transverse partition 121, the longitudinal partition 122 and the inner side wall of the first outer frame 123. The second curling channel 13 includes a second outer frame 132 that is adapted to the first outer frame 123, and the side wall of the second outer frame 132 is provided with an inwardly concave groove 133 corresponding to the transverse partition 121 and the longitudinal partition 122; the second outer frame 132 is inserted into the first outer frame 123, and the transverse partition 121 and the longitudinal partition 122 are inserted into the corresponding groove 133. After the second outer frame 132 is inserted into the first outer frame 123, the annular flow channel 14 and the inner cavity of the second curled channel 13 are only connected through the sound wave inlet 131, and the rest of the positions are completely separated. Of course, the shape of the first outer frame 123 is not limited to the square shape shown in the figure, and other shapes are also possible. The number of transverse and longitudinal partitions is also not limited to the number shown in the figure, and it can be increased or decreased according to actual needs.

[0040] Composite noise reduction structure, such as Fig.10 As shown, it is composed of a first layer, a second layer and a third layer. The second layer is a porous medium material 2, the third layer is a polymer sound insulation felt 3, and the first layer is a loop-curled resonant sound absorption structure.

[0041] The porous medium material 2 is composed of a porous structure with a porosity of 30%-90%, a pore size distribution range of 0.1 μm to 2 mm, and an irregular three-dimensional interlaced structure. The matrix material may include polyurethane, phenolic resin, glass fiber, ceramic fiber or a composite material thereof. The porous medium material 2 is mainly used for absorbing medium and high frequency noise.

[0042] Polymer sound insulation felt 3, the sound insulation felt is made of high-density polymer material, the main component is modified polyethylene (PE), polyvinyl chloride (PVC) or their composite materials, the material density range is 1500kg / m 3 Up to 2500kg / m 3 , the thickness range is only 1mm to 5mm. Mainly used for isolation of medium and high frequency noise.

[0043] The composite noise reduction structure, whose first layer of loop curled resonant sound absorption structure performs targeted noise reduction on the 50Hz power frequency of most electrical and mechanical equipment. The loop curled resonant sound absorption structure 1 belongs to the hard sound field boundary and can also isolate the full-frequency noise; the second layer of porous medium material 2 mainly absorbs medium and high frequency noise; the third layer uses polymer sound insulation felt 3, which mainly isolates medium and high frequency noise. The combination of the three layers improves the overall noise reduction performance. While the loop curled resonant sound absorption structure 1 has the same sound absorption performance, the sound absorption area of ​​the traditional curled resonant sound absorption structure is reduced by 50%, making the sound absorption in limited spaces more efficient. It reduces the difficulty of noise reduction in limited spaces in practical applications, and has great promotion value in application fields where 50Hz industrial power frequency noise reduction is required.

[0044] The specific noise reduction process is as follows: Fig.10 As shown:

[0045] The noise source sound wave pi1 enters the loop curling resonant sound absorbing structure 1 for noise reduction treatment. Its sound absorption coefficient is 0.9, so the 50Hz power frequency noise is reduced by 10dB; at the same time, the loop curling resonant sound absorbing structure 1 also has the ability to isolate other frequency noises. The noise source sound wave pi1 is processed by the loop curling resonant sound absorbing structure 1 to become the second noise sound wave pi2, which is equal to the first layer of transmitted sound wave pt1 in value. The second noise sound wave pi2 is then processed by the second layer of porous medium material 2 to reduce the high-frequency noise therein and becomes the third noise sound wave pi3, which is equal to the second layer of transmitted sound wave pt2.

[0046] The third noise sound wave pi3 is processed by the third layer of polymer sound insulation felt 3 to isolate the medium and high frequency noise. The sound wave pr3 reflected by the polymer sound insulation felt 3 returns to the second layer of porous medium material 2 for processing, and the third transmitted sound wave pt3 is transmitted by the polymer sound insulation felt 3. Finally, the noise sound wave at the human ear position becomes the transmitted sound wave pt3 of the third layer of polymer sound insulation felt.

[0047] Since the looped curled resonant sound absorbing structure 1 is made of hard sound field boundary material, it has a certain isolation effect on the sound waves of the noise source, and the sound wave pr1 reflected by it is relatively large. The porous medium material 2 mainly absorbs sound waves, and the sound wave pr2 reflected by it is very small. The polymer sound insulation felt 3 mainly plays a role in isolating medium and high frequency noise, and the sound wave pr3 reflected by it is very large. Large, very small and very large are expressions of the three layers' ability to reflect sound waves in comparison.

[0048] The noise reduction performance of the composite noise reduction structure disclosed in the present invention is further described below with specific embodiments:

[0049] Embodiment 1:

[0050] The composite noise reduction structure disclosed in the present invention is subjected to a noise reduction test, and the specific data of the first layer of the looped curled resonant sound absorbing structure are as follows:

[0051] The micro-perforated plate 11 is 4 mm thick and is made of high-density photosensitive resin as a 3D printing material; the sound-transmitting hole 111 on the micro-perforated plate 11 has a diameter of 5.5 mm and a circular shape; the wall thickness of the surrounding walls and the bottom wall thickness of the first curled channel 12 is 2 mm and is made of high-density photosensitive resin as a 3D printing material; the wall thickness of the second curled channel 13 is 0.1 mm; the total thickness of the loop curled resonant sound-absorbing structure is 45 mm, the length is 171 mm, the width is 130 mm, and the sound absorption area is 171×130=22230 mm 2 ,like Figure 4 As shown, the sound absorption coefficient of the loop-curled resonant sound-absorbing structure for 50Hz noise is 0.9.

[0052] The second layer uses 25mm thick porous medium material; the third layer uses polymer sound insulation felt 3;

[0053] The 1 / 3 octave noise spectrum of the original noise used in the test is as follows: Figure 5 shown.

[0054] Comparative Example 1:

[0055] The noise reduction test was carried out using a traditional curled resonant sound absorbing structure. Figure 1 As shown, it mainly includes a micro-perforated plate 11 and a first curled channel 12, and there is no second curled channel 13. Among them, the micro-perforated plate 11 is 4mm thick and is made of high-density photosensitive resin as a 3D printing material; the sound-permeable hole 111 on the micro-perforated plate 11 has a diameter of 5.5mm and a circular shape; the wall thickness around and the bottom wall thickness of the first curled channel 12 are 2mm, and it is made of high-density photosensitive resin as a 3D printing material. The total thickness of the curled resonant sound-absorbing structure is 45mm, the length is 343mm, the width is 130mm, and the sound absorption area is 343×130=44590mm 2 ,like Figure 4As shown, the sound absorption coefficient of the traditional curled resonant sound absorption structure for 50Hz noise is 0.9.

[0056] The 1 / 3 octave noise spectrum of the original noise used in the test is as follows: Figure 5 shown.

[0057] That is, the comparative example is completely identical to the first layer loop curled resonant sound absorbing structure of Example 1 except that the length of the curled resonant sound absorbing structure is different and the second curled channel 13 is missing.

[0058] Comparative Example 2:

[0059] The noise reduction test was carried out using a traditional noise reduction structure. The first layer used a porous medium material of the same thickness as the loop-curled sound-absorbing structure in Example 1, that is, the first layer was a porous medium material with a thickness of 45 mm; the second layer used a porous medium material, and its material and thickness were exactly the same as those in Example 1, which was a 25 mm thick porous medium material; the third layer used a polymer sound insulation felt, and its material and thickness were exactly the same as those in Example 1.

[0060] The 1 / 3 octave noise spectrum of the original noise used in the test is as follows: Figure 5 shown.

[0061] Through the experiment, the sound absorption coefficient comparison between the loop-curled resonant sound absorption structure and the traditional curled resonant sound absorption structure in the noise reduction application of 50Hz industrial frequency noise was obtained. Figure 4 As shown in the figure, it can be seen that for 50Hz power frequency noise, the sound absorption coefficient of the loop curled resonant sound absorption structure disclosed in Example 1 is 0.9, and the sound absorption coefficient of the traditional curled resonant sound absorption structure disclosed in Comparative Example 1 is 0.9. That is, under the same sound absorption coefficient, the sound absorption area of ​​the loop curled resonant sound absorption structure disclosed in the embodiment is reduced by 50% compared with the traditional curled resonant sound absorption structure disclosed in the comparative example.

[0062] Through experiments, we obtained Fig. 9 The 1 / 3 octave noise spectrum after noise reduction in Example 1 is shown, and Figure 8 The 1 / 3 octave noise spectrum after noise reduction in Comparative Example 2 is shown. Figure 8 and Fig. 9 It can be seen that the noise reduction performance of the composite noise reduction structure disclosed in Example 1 is improved by 93% compared with the noise reduction performance of the composite noise reduction structure disclosed in Comparative Example 2.

[0063] Through experiments, we obtained Figure 6 The comparison diagram of the sound absorption coefficient of the porous medium material in Example 1 and the porous medium material in Comparative Example 2 is shown. The conventional method in the figure refers to Comparative Example 2, and the present invention refers to Example 1.

[0064] Through the experiment, the 1 / 3 octave transmission loss spectrum of the loop-curled sound-absorbing structure after A-weighted correction was also obtained.

Claims

1. A loop curling resonant sound absorbing structure, comprising a micro-perforated plate (11) and a first curling channel (12), wherein the first curling channel (12) is a hollow cavity structure with a closed periphery; the micro-perforated plate (11) covers the first curling channel (12), and the micro-perforated plate (11) is provided with a sound-transmitting hole (111); characterized in that: The second curled channel (13) is a hollow cavity structure with a closed periphery; the second curled channel (13) is inserted into the first curled channel (12), and is surrounded by the inner side wall of the first curled channel (12) and the outer side wall of the second curled channel (13) to form an annular flow channel (14); A sound wave inlet (131) for allowing sound to enter the inner cavity of the second curled channel (13) is provided on the side wall of the second curled channel (13); the sound-permeable hole (111) penetrates the annular flow channel (14); and, along the extension direction of the inner flow channel of the second curled channel (13), the sound wave inlet (131) is located at the head end of the second curled channel (13).

2. The loop-curled resonant sound absorbing structure according to claim 1, characterized in that: The sound-transmitting hole (111) is circular or square.

3. The loop-curled resonant sound absorbing structure according to claim 2, characterized in that: The boundary of the micro-perforated plate (11) is a hard sound field boundary.

4. The loop-curled resonant sound absorbing structure according to claim 3, characterized in that: The first curling channel (12) is a curling channel formed by a combination of hard sound field boundary walls.

5. The loop-curled resonant sound absorbing structure according to any one of claims 1 to 4, characterized in that: The first curling channel (12) comprises a transverse partition (121), a longitudinal partition (122) and a first outer frame (123) which surrounds the first outer frame (123); the transverse partition (121) and the longitudinal partition (122) are arranged in the first outer frame (123); a tortuous air flow channel is formed by the inner side wall of the transverse partition (121), the longitudinal partition (122) and the first outer frame (123); The second curling channel (13) comprises a second outer frame (132) adapted to the first outer frame (123), and inwardly recessed grooves (133) are provided at the side walls of the second outer frame (132) corresponding to the transverse partition (121) and the longitudinal partition (122); The second outer frame (132) is inserted into the first outer frame (123), and the transverse partition (121) and the longitudinal partition (122) are inserted into corresponding grooves (133).

6. A composite noise reduction structure, which is composed of a first layer, a second layer and a third layer, wherein the second layer is a porous medium material (2), and the third layer is a polymer sound insulation felt (3), characterized in that: The first layer is the loop-curled resonant sound-absorbing structure (1) as described in any one of claims 1 to 4.

7. The composite noise reduction structure according to claim 6, characterized in that: The porous medium material (2) has a porosity of 30%-90%, a pore diameter of 0.1 μm-2 mm, and a pore network morphology of an irregular three-dimensional interlaced structure.

8. The composite noise reduction structure according to claim 6, characterized in that: The density of the polymer sound insulation felt (3) is 1500 kg / m 3 -2500kg / m 3 , thickness range is 1mm-5mm.

9. The sound absorption and noise reduction method of the composite noise reduction structure according to claim 6, characterized in that: The sound wave of the noise source enters the loop-curled resonant sound absorbing structure (1) for processing and becomes a second noise sound wave. The second noise sound wave enters the second layer of porous medium material (2) for processing and becomes a third noise sound wave. The third noise sound wave is processed by the third layer of polymer sound insulation felt (3) to isolate medium and high frequency noise. The sound wave reflected by the polymer sound insulation felt (3) returns to the second layer of porous medium material (2) for processing and is transmitted by the polymer sound insulation felt (3) to emit a third transmitted sound wave.

10. The sound absorption and noise reduction method of the composite noise reduction structure according to claim 9, characterized in that: The process of the noise source sound wave entering the first curled channel (12) is as follows: the noise source sound wave enters the annular flow channel (14) between the first curled channel (12) and the second curled channel (13) through the sound-transmitting hole (111) on the micro-perforated plate (11), moves along the annular flow channel (14) to the end, and enters the second curled channel (13) through the sound wave inlet (131) of the second curled channel (13) at the end.

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