Looped back coiled resonant sound absorption structure, composite noise reduction structure and sound absorption noise reduction method

Abstract

The application discloses a looped coiled resonant sound absorption structure, a composite noise reduction structure and a sound absorption noise reduction method, belongs to the field of noise control, aims to meet the 50Hz low frequency noise reduction performance while reducing the sound absorption area. The looped coiled resonant sound absorption structure comprises a micro-perforated plate and a first coiled channel, a second coiled channel is inserted into the first coiled channel, an annular flow channel is formed by the inner side wall of the first coiled channel and the outer side wall of the second coiled channel, the sound wave inlet for allowing sound to enter the inner cavity of the second coiled channel is arranged on the side wall of the second coiled channel, and the sound transmission hole penetrates to the annular flow channel. The application can reduce the 50Hz power frequency of most electrical and mechanical equipment; under the premise of the same sound absorption performance, the sound absorption area is reduced by 50%, and the application of noise reduction in limited space has great popularization value; in the composite noise reduction structure, the looped coiled resonant sound absorption structure is arranged in the first layer of the composite noise reduction structure, and the noise reduction performance is improved by 93% compared with the traditional noise reduction method.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of noise control, in particular to a looped coiled resonant sound absorption structure, a composite noise reduction structure and a sound absorption noise reduction method. BACKGROUND

[0002] With the development of social economy, people gradually put forward higher requirements for the governance of noise pollution. As a kind of medical auxiliary equipment used in family environment, the noise level of household oxygen generator directly affects the user experience and the quality of life. The main noise reduction and sound absorption structure at present is a three-layer structure, which is first layer, second layer and third layer, wherein the first layer and the second layer are both porous medium materials, and the third layer is a high polymer sound insulation felt. When the sound wave enters the porous material, it is reflected, scattered and gradually converted into heat energy between the pores of the porous medium material. Because the pores of the porous medium are very small, the wavelength of the low frequency sound wave is relatively long, which is easy to form diffraction, resulting in that the high frequency sound absorption capacity of the porous medium material is strong, while the low frequency sound absorption capacity is weak. For most electrical and mechanical equipment, because the frequency of 50Hz power frequency noise is too low, it is difficult to eliminate, which causes great disturbance to people in the application place with high noise reduction requirements, and a large part of the noise frequency of household oxygen generator is composed of 50Hz power frequency noise. The traditional noise reduction and sound absorption structure cannot meet the noise reduction requirements. Figure 1 The coiled resonant sound absorption structure shown is suitable for 50Hz low frequency noise reduction, which comprises a micro-perforated plate 11 and a first coiled channel 12, the first coiled channel 12 is a hollow cavity structure with closed periphery; the micro-perforated plate 11 covers the first coiled channel 12, and the micro-perforated plate 11 is provided with sound transmission holes 111. After the sound wave enters the first coiled channel 12 through the sound transmission holes 111 provided on the micro-perforated plate 11, it moves along the tortuous air flow channel in the first coiled channel 12, and forms a standing wave in the process, thereby consuming energy and achieving the purpose of low frequency noise reduction. However, the performance of low frequency noise reduction is limited by the length of the air flow channel inside the sound absorption 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. The noise reduction space inside the oxygen generator is limited, so the use of the above-mentioned coiled resonant sound absorption structure in the limited noise reduction space of the household oxygen generator is quite limited. Reducing the noise of the household oxygen generator can improve the user comfort and meet the user's demand for a quiet environment. Under such technical application, 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

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

[0004] The technical scheme adopted by the present application is: a looped coiled resonant sound absorption structure, comprising a micro-perforated panel and a first coiled channel, the first coiled channel is a hollow cavity structure with a closed periphery; the micro-perforated panel covers the first coiled channel, and the micro-perforated panel is provided with sound transmission holes; further comprising a second coiled channel, the second coiled channel is a hollow cavity structure with a closed periphery; the second coiled channel is inserted into the first coiled channel, and an annular flow channel is formed by the inner side wall of the first coiled channel and the outer side wall of the second coiled channel; the side wall of the second coiled channel is provided with a sound wave inlet for allowing sound to enter the inner cavity of the second coiled channel; the sound transmission holes pass through to the annular flow channel; and along the extension direction of the flow channel in the second coiled channel, the sound wave inlet is located at the first end position of the second coiled channel.

[0005] Further, the sound transmission holes are circular or square.

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

[0007] Further, the first coiled channel is a coiled channel formed by a hard sound field boundary wall.

[0008] Further, the first coiled channel comprises a horizontal partition plate, a vertical partition plate and a square first outer frame surrounding a periphery, the horizontal partition plate and the vertical partition plate are arranged in the first outer frame; a tortuous air flow channel is formed by the horizontal partition plate, the vertical partition plate and the inner side wall of the first outer frame;

[0009] The second coiled channel comprises a second outer frame matched with the first outer frame, the side wall of the second outer frame is provided with a recessed groove inwardly recessed at the corresponding positions of the horizontal partition plate and the vertical partition plate; the second outer frame is inserted into the first outer frame, and the horizontal partition plate and the vertical partition plate are inserted into the corresponding recessed grooves.

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

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

[0012] Further, the density of the high polymer sound insulation felt is 1500 kg / m 3 -2500 kg / m 3 , and the thickness ranges from 1 mm to 5 mm.

[0013] The sound absorption and noise reduction method of the composite noise reduction structure is as follows: noise source sound waves become second noise source sound waves after being processed by the looped and curled resonant sound absorption structure, the second noise source sound waves become third noise source sound waves after being processed by the second layer of porous medium material, the third noise source sound waves are processed by the third layer of high-molecular sound insulation felt, the sound waves reflected by the high-molecular sound insulation felt are processed in the second layer of porous medium material, and the third transmission sound waves are transmitted by the high-molecular sound insulation felt.

[0014] The sound absorption and noise reduction method is as follows: noise source sound waves enter the looped and curled resonant sound absorption structure through the first curled channel, and then enter the second curled channel at the end of the looped and curled resonant sound absorption structure.

[0015] The looped and curled resonant sound absorption structure disclosed by the application has the advantages that the looped and curled resonant sound absorption structure is targeted for noise reduction of 50Hz power frequency of most electrical and mechanical equipment.

[0016] The second curled channel is arranged in the first curled channel to form a looped flow channel, so that the propagation path of sound waves in the looped and curled resonant sound absorption structure is longer, the sound absorption area is reduced by 50% under the premise of the same sound absorption performance, and the looped and curled resonant sound absorption structure has great popularization value in noise reduction applications in limited space.

[0017] In the composite noise reduction structure, the looped and curled resonant sound absorption structure is arranged in the first layer of the composite noise reduction structure, the resonant sound absorption structure is usually composed of a hard sound field boundary wall, and the resonant sound absorption structure has a certain isolation effect on noise source sound waves, and the noise reduction performance is improved by 93% compared with the traditional noise reduction method. BRIEF DESCRIPTION OF DRAWINGS

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

[0019] Figure 2 It is a schematic diagram of the looped and curled resonant sound absorption structure of the application.

[0020] Figure 3 It is an A-A sectional view of the looped and curled resonant sound absorption structure of the application.

[0021] Figure 4 It is a schematic diagram of sound absorption coefficients of the looped and curled resonant sound absorption structure and the traditional curled resonant sound absorption structure in noise reduction applications for 50Hz power frequency noise.

[0022] Figure 5 It is a 1 / 3 octave noise spectrum diagram of original noise.

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

[0024] Figure 7 A 1 / 3 octave band transmission loss spectrum chart of the A-weighted modified loop-curl type sound absorption structure in Example 1;

[0025] Figure 8 A 1 / 3 octave band noise spectrum chart after noise reduction by the traditional noise reduction method in Comparative Example 2;

[0026] Figure 9 A 1 / 3 octave band noise spectrum chart after noise reduction by the present application in Example 1;

[0027] Figure 10 A noise reduction schematic diagram of the composite noise reduction structure disclosed by the present application.

[0028] In the figure, 1 is a loop-curl type resonant sound absorption structure, 2 is a porous medium material, 3 is a high-molecular sound insulation felt, 11 is a micro-perforated panel, 111 is a sound transmission hole, 12 is a first curling channel, 13 is a second curling channel, 14 is a loop-shaped flow channel, 121 is a transverse partition plate, 122 is a longitudinal partition plate, 123 is a first outer frame, 131 is a sound wave inlet, 132 is a second outer frame, and 133 is a groove. DETAILED DESCRIPTION

[0029] The present application is further described below in combination with the accompanying drawings and examples:

[0030] In the present application, the terms "inner", "outer", "top", "bottom", "lateral", "longitudinal", and the like indicate the orientation or positional relationship based on the accompanying drawings. Figure 2 The orientation or positional relationship shown is only for the convenience of describing the present application, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0031] The loop-curl type resonant sound absorption structure, such as Figure 2 and Figure 3As shown, it comprises a micro-perforated plate 11 and a first coiled channel 12 in a peripherally closed hollow cavity structure; the micro-perforated plate 11 covers the first coiled channel 12, and the micro-perforated plate 11 is provided with sound transmission holes 111; it further comprises a second coiled channel 13 in a peripherally closed hollow cavity structure; the second coiled channel 13 is inserted into the first coiled channel 12, and an annular flow channel 14 is formed by the inner side wall of the first coiled channel 12 and the outer side wall of the second coiled channel 13; the side wall of the second coiled channel 13 is provided with a sound wave inlet 131 for allowing sound waves to enter the inner cavity of the second coiled channel 13; the sound transmission holes 111 extend through to the annular flow channel 14; and along the extension direction of the flow channel in the second coiled channel 13, the sound transmission holes 111 correspond to the end position of the second coiled channel 13, and the sound wave inlet 131 is located at the head end position of the second coiled channel 13.

[0032] The incident sound waves enter the annular flow channel 14 formed by the inner side wall of the first coiled channel 12 and the outer side wall of the second coiled channel 13 through the sound transmission holes 111 on the micro-perforated plate 11, move along the annular flow channel 14 to the sound wave inlet 131 of the second coiled channel 13, enter the second coiled channel 13 through the sound wave inlet 131, and reach the end of the second coiled channel 13 after energy consumption in the coiled channel. Due to the formation of standing waves in the annular flow channel 14 and the second coiled channel 13, the incident sound waves of 50 Hz can be absorbed according to the resonance effect of the material, achieving the purpose of noise reduction.

[0033] The second coiled channel 13 forms a tortuous air flow channel, one end of which 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. The sound waves enter the second coiled channel 13 through the sound wave inlet 131 and form standing waves in the second coiled channel 13. The sound wave inlet 131 is located at the head end position of the second coiled channel 13, so that the sound waves move towards the end of the second coiled channel 13 after entering the second coiled channel 13 through the sound wave inlet 131.

[0034] Compared with the traditional coiled resonant sound absorption structure, in the present embodiment, the sound waves continue to enter the second coiled channel 13 after reaching the sound wave inlet 131 position in the first coiled channel 12, and move from the sound wave inlet 131 at the head end to the end of the second coiled channel 13, with a longer movement path, which is beneficial to effectively consume energy.

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

[0036] The first winding channel 12 is a winding channel formed by a combination of materials with hard sound field boundary characteristics, with a boundary thickness of millimeters, and is generally made of 3D printing materials such as photosensitive resin, epoxy resin, or acrylic plates.

[0037] The second winding channel 13 is a winding channel formed by a combination of materials with hard sound field boundary characteristics, with a thickness of millimeters, and is generally made of 3D printing materials such as photosensitive resin, epoxy resin, or acrylic plates.

[0038] Figure 2 One of the specific configurations of the first winding channel 12 and the second winding channel 13 is disclosed in the specification.

[0039] That is, the first winding channel 12 includes a transverse partition plate 121, a longitudinal partition plate 122, and a square first outer frame 123 surrounding a periphery, the transverse partition plate 121 and the longitudinal partition plate 122 are arranged in the first outer frame 123, and a winding air flow channel is formed by the transverse partition plate 121, the longitudinal partition plate 122, and the inner side wall of the first outer frame 123. The second winding channel 13 includes a second outer frame 132 adapted to the first outer frame 123, the side wall of the second outer frame 132 is provided with a recess 133 inwardly recessed at the corresponding position of the transverse partition plate 121 and the longitudinal partition plate 122; the second outer frame 132 is inserted into the first outer frame 123, and the transverse partition plate 121 and the longitudinal partition plate 122 are inserted into the corresponding recess 133. After the second outer frame 132 is inserted into the first outer frame 123, the annular flow channel 14 is only communicated with the inner cavity of the second winding channel 13 through the sound wave inlet 131, and the rest 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 partition plates and longitudinal partition plates is also not limited to the number shown in the figure, and can be increased or decreased according to actual needs.

[0040] The composite noise reduction structure, as shown in Figure 10 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 high polymer sound insulation felt 3, and the first layer is a loop winding type resonance sound absorption structure.

[0041] The porous medium material 2 is composed of a porous structure penetrating the inside, with a porosity of 30%-90% and a pore size distribution range of 0.1 μm to 2 mm, and the pore network has an irregular three-dimensional interlaced structure. The base material can 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] High polymer sound insulation felt 3, which is made of high density high polymer material, mainly including modified polyethylene (PE), polyvinyl chloride (PVC) or composite materials, with a material density ranging from 1500 kg / m 3 to 2500 kg / m 3 , and a thickness ranging from 1 mm to 5 mm. It is mainly used for isolating medium and high frequency noise.

[0043] The composite noise reduction structure, the first layer of the looped coiled resonant sound absorption structure is targeted at reducing 50Hz power frequency noise of most electrical and mechanical equipment, and the looped coiled resonant sound absorption structure 1 belongs to a hard sound field boundary, and can also isolate noise in the full frequency domain; the second layer of the porous medium material 2 mainly absorbs medium and high frequency noise; the third layer uses high polymer sound insulation felt 3, which mainly isolates medium and high frequency noise, and the combination of the three layers improves the overall noise reduction performance. Under the premise of the same sound absorption performance, the sound absorption area of the looped coiled resonant sound absorption structure 1 is reduced by 50% compared with the traditional coiled resonant sound absorption structure, making the sound absorption in limited space more efficient. It reduces the difficulty of noise reduction in limited space in actual application, and has great promotional value in application fields that need to reduce 50Hz industrial power frequency noise.

[0044] The specific noise reduction process is shown in Figure 10 .

[0045] The noise source sound wave pi1 enters the looped coiled resonant sound absorption structure 1 for noise reduction processing, and the sound absorption coefficient is 0.9, so the 50Hz power frequency noise is reduced by 10dB; at the same time, the looped coiled resonant sound absorption structure 1 also has the ability to isolate noise of other frequency points. After the noise source sound wave pi1 is processed by the looped coiled resonant sound absorption structure 1, it becomes the second noise sound wave pi2, which is equal in value to the first layer of transmitted sound wave pt1. The second noise sound wave pi2 is processed by the second layer of porous medium material 2 to reduce the high frequency noise, 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 high polymer sound insulation felt 3 to isolate medium and high frequency noise, and the sound wave pr3 reflected by the high 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 high polymer sound insulation felt 3. The noise sound wave at the human ear position finally becomes the transmitted sound wave pt3 of the third layer of high polymer sound insulation felt.

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

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

[0049] Example 1:

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

[0051] The micro-perforated plate 11 has a thickness of 4 mm and is made of high-density photosensitive resin as a material and 3D printed; the sound transmission hole 111 on the micro-perforated plate 11 has a diameter of 5.5 mm and a circular shape; the first coiled channel 12 has a wall thickness of 2 mm around the periphery and a bottom wall thickness of 2 mm, and is made of high-density photosensitive resin as a material and 3D printed; the wall thickness of the second coiled channel 13 is 0.1 mm; the total thickness of the looped coiled resonant sound absorption structure is 45 mm, the length is 171 mm, the width is 130 mm, and the sound absorption area is 171x130=22230 mm 2 As shown in Figure 4 , the sound absorption coefficient of the looped coiled resonant sound absorption structure for 50 Hz noise is 0.9.

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

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

[0054] Comparative Example 1:

[0055] A traditional coiled resonant sound absorption structure is used for noise reduction test, and the traditional coiled resonant sound absorption structure is shown in Figure 1 , mainly including a micro-perforated plate 11 and a first coiled channel 12, without a second coiled channel 13. Among them, the micro-perforated plate 11 has a thickness of 4 mm and is made of high-density photosensitive resin as a material and 3D printed; the sound transmission hole 111 on the micro-perforated plate 11 has a diameter of 5.5 mm and a circular shape; the first coiled channel 12 has a wall thickness of 2 mm around the periphery and a bottom wall thickness of 2 mm, and is made of high-density photosensitive resin as a material and 3D printed. The total thickness of the coiled resonant sound absorption structure is 45 mm, the length is 343 mm, the width is 130 mm, and the sound absorption area is 343x130=44590 mm 2 As shown in Figure 4As shown, the absorption coefficient of the traditional coiled resonant sound-absorbing structure for 50Hz noise is 0.9.

[0056] The 1 / 3 octave band noise spectrum of the original noise used in the experiment is shown below. Figure 5 As shown.

[0057] That is, compared with the first layer of loop-type resonant sound-absorbing structure in Example 1, the comparative example is exactly the same except that the length of the loop-type resonant sound-absorbing structure is different and there is no second loop channel 13.

[0058] Comparative Example 2:

[0059] Noise reduction tests were conducted using a traditional noise reduction structure. The first layer was a porous medium material with the same thickness as the loop-shaped sound-absorbing structure in Example 1, i.e., the first layer was a porous medium material with a thickness of 45 mm. The second layer was a porous medium material with the same material and thickness as in Example 1, which was a porous medium material with a thickness of 25 mm. The third layer was a polymer sound insulation felt with the same material and thickness as in Example 1.

[0060] The 1 / 3 octave band noise spectrum of the original noise used in the experiment is shown below. Figure 5 As shown.

[0061] Through experiments, the sound absorption coefficients of the loop-type coiled resonant sound-absorbing structure and the traditional coiled resonant sound-absorbing structure were compared in noise reduction applications for 50Hz power frequency noise. Figure 4 As shown in the figure, for 50Hz power frequency noise, the sound absorption coefficient of the loop-shaped coiled resonant sound-absorbing structure disclosed in Example 1 is 0.9, and the sound absorption coefficient of the conventional coiled resonant sound-absorbing structure disclosed in Comparative Example 1 is also 0.9. That is, under the same sound absorption coefficient, the sound absorption area of ​​the loop-shaped coiled resonant sound-absorbing structure disclosed in Example 1 is reduced by 50% compared with the conventional coiled resonant sound-absorbing structure disclosed in Comparative Example 1.

[0062] Through experiments, we obtained Figure 9 The 1 / 3 octave band noise spectrum diagram after noise reduction in Example 1 is shown below. Figure 8 The 1 / 3 octave band noise spectrum after noise reduction is shown in Comparative Example 2. Figure 8 and Figure 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 diagram shows a comparison of the sound absorption coefficients of the porous medium material in Example 1 and the porous medium material in Comparative Example 2. The conventional method in the diagram refers to Comparative Example 2, while the present invention refers to Example 1.

[0064] Through experiments, the 1 / 3 octave band transmission loss spectrum of the loop-shaped sound-absorbing structure after A-weighting correction was also obtained.

Claims

1. A loop-shaped resonant sound-absorbing structure, comprising a micro-perforated plate (11) and a first coiled channel (12), wherein the first coiled channel (12) is a hollow cavity structure with a closed outer periphery; the micro-perforated plate (11) covers the first coiled channel (12), and the micro-perforated plate (11) is provided with sound-transmitting holes (111); characterized in that: It also includes a second coiled channel (13), which has a hollow cavity structure with an outer periphery closed; the second coiled channel (13) is inserted into the first coiled channel (12), and is surrounded by the inner side wall of the first coiled channel (12) and the outer side wall of the second coiled channel (13) to form an annular flow channel (14). The side wall of the second coiled channel (13) is provided with a sound wave inlet (131) for sound to enter the inner cavity of the second coiled channel (13); the sound-transmitting hole (111) extends to the annular flow channel (14); and, along the extension direction of the inner flow channel of the second coiled channel (13), the sound wave inlet (131) is located at the beginning of the second coiled channel (13); The first curved channel (12) includes a horizontal partition (121), a vertical partition (122), and a first outer frame (123) surrounding it. The horizontal partition (121) and the vertical partition (122) are arranged inside the first outer frame (123). A tortuous airflow channel is formed by the inner walls of the horizontal partition (121), the vertical partition (122), and the first outer frame (123). The second curling channel (13) includes a second outer frame (132) adapted to the first outer frame (123), and the side wall of the second outer frame (132) is provided with an inwardly recessed 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 longitudinal partition (122) are inserted into the corresponding grooves (133), so that the annular flow channel (14) and the inner cavity of the second coiled channel (13) are connected only through the sound wave inlet (131).

2. The loop-shaped resonant sound-absorbing structure as described in claim 1, characterized in that: The sound-permeable hole (111) is circular or square.

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

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

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

6. The composite noise reduction structure as described in claim 5, characterized in that: The porous medium material (2) has a porosity of 30%-90%, a pore size of 0.1μm-2mm, and an irregular three-dimensional interlaced pore network.

7. The composite noise reduction structure as described in claim 5, characterized in that: The polymer sound insulation felt (3) has a density of 1500kg / m³-2500kg / m³ and a thickness range of 1mm-5mm.

8. The sound absorption and noise reduction method of the composite noise reduction structure as described in claim 5, characterized in that: After the noise source sound wave enters the loop-shaped resonant sound absorption structure (1) and is processed, it becomes the second noise sound wave. After the second noise sound wave enters the porous medium material (2) of the second layer and is processed, it becomes the third noise sound wave. The third noise sound wave is processed by the third layer, which is a polymer sound insulation felt (3), to isolate the mid-to-high frequency noise. The sound wave reflected by the polymer sound insulation felt (3) returns to the porous medium material (2) of the second layer for processing. The third transmitted sound wave is transmitted by the polymer sound insulation felt (3).

9. The sound absorption and noise reduction method of the composite noise reduction structure as described in claim 8, 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-permeable 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) at the end.

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