Resonance unit of a frequency-modulated ultra-thin, ultra-sparse, low-frequency sound-absorbing device and its use

Abstract

The present invention provides a resonance unit of a frequency-modulated ultra-thin, ultra-sparse, and low-frequency sound-absorbing device and its use. Inside the resonance unit is a square air resonance cavity, which is formed by surrounding with two end faces and first and second coiled channels with the same structure connected end to end. The two coiled channels are centrosymmetrically distributed. The head and tail of the first coiled channel and the second coiled channel respectively have a sound channel inlet communicating with the outside and a sound channel outlet extending towards the center of the resonant air cavity. The air resonance cavity communicates with the outside through the coiled channels. By adjusting the width of the coiled channels and the distance between the two sound channel outlets, the working frequency band of the resonance unit can be regulated. Multiple resonance units can achieve a good low-frequency sound absorption effect according to a specific arrangement manner and structural parameters, have the characteristics of deep sub-wavelength, and solve the problem that traditional sound-absorbing materials are too thick in the low-frequency range.

Description

Technical Field

[0001] The present invention belongs to the field of noise control based on acoustic metamaterials, and particularly relates to a resonance unit of a frequency-modulated ultra-thin, ultra-sparse, low-frequency noise elimination device and its use. Background Art

[0002] Noise pollution is the third largest public hazard after air pollution and water pollution. In the production field, low-frequency noise will be generated in aspects such as the power system, body vibration, and aerodynamic force of mechanical equipment. Strong low-frequency noise can cause instrument failure or even damage, and seriously endanger the physical and mental health of operators. An effective method for controlling noise is to reduce the impact of noise on the environment by blocking or absorbing noise during the noise propagation process. The performance of traditional low-frequency noise elimination / acoustic insulation materials strictly follows the mass density law, and problems of large thickness and high density will occur in the low-frequency range, thus limiting the application range of traditional noise elimination / acoustic insulation materials. In recent years, the emergence of acoustic metamaterials, especially acoustic metasurfaces, has provided a new way to break through the limitations of traditional noise elimination / acoustic insulation materials. Acoustic metasurfaces have the characteristics of ultra-thin, openable, and easy to regulate, and their excellent acoustic wave manipulation ability provides a theoretical solution and technical path for designing ultra-thin and open low-frequency noise elimination / acoustic insulation structures.

[0003] Currently, in the field of acoustic metamaterials, researchers at home and abroad mainly achieve the acoustic insulation or noise elimination effect by designing thin-film resonant structures, cylindrical absorbers, and coiled space structures.

[0004] The thin-film resonant structure is to attach a mass with different mass to an elastically fixed thin film around, and adjust its resonant frequency by changing the film tension to achieve the acoustic insulation effect in different frequency bands.

[0005] The cylindrical absorber is to design the refractive index distribution of the model shell, and guide the incident sound energy along a specific propagation path into the sound absorption core to achieve the noise elimination effect. In addition, researchers design a two-dimensional cylindrical structure with specific complex mass density and bulk modulus, so that the amplitudes of the incident and scattered sound waves are similar and the phases are opposite, thus realizing a cylindrical absorber based on the coherent mechanism.

[0006] The coiled space structure is to design a coiled space unit with high symmetry, and based on the monopole Mie resonance mode of the unit, successfully achieve a strong reflection effect of low-frequency sound waves. By combining the coiled space structure with a perforated plate, ultra-thin low-frequency sound absorption can be achieved. Expanding its application to multi-layer structures can achieve broadband sound absorption effect.

[0007] The deficiencies of traditional technologies are as follows:

[0008] (1). The performance of traditional sound-absorbing / noise-insulating materials strictly follows the mass density law. To increase the noise insulation amount, it is necessary to increase the thickness or surface density of the materials. Generally, the thickness should reach 1 / 4 to 1 / 2 of the working wavelength, so there are problems of large thickness and high density in the low-frequency range.

[0009] (2). The working frequency band of traditional sound-absorbing / noise-insulating materials is usually fixed and not easy to adjust.

[0010] The reasons for the above deficiencies are as follows: Firstly, traditional sound-absorbing / noise-insulating materials are mostly porous materials, and the loss of sound energy is mainly achieved based on the flow resistance of air between pores. In the low-frequency range, the sound energy density is low, the sound energy loss efficiency is not high, and the sound absorption effect is poor. Secondly, due to the inflexible structure of traditional sound-absorbing / noise-insulating materials, the working frequency is single, lacking flexibility for different application scenarios. Summary of the Invention

[0011] Aiming at the deficiencies of existing sound-absorbing / noise-insulating materials, such as large thickness, high density in the low-frequency range, single working frequency band, and lack of adjustability, the present invention provides an ultra-thin, ultra-sparse, low-frequency sound-absorbing device based on resonance units. Its design size is small, with deep sub-wavelength characteristics, simple structure, easy to manufacture and produce, and has good sound absorption performance and an easily adjustable working frequency band.

[0012] The present invention achieves the above technical objectives through the following technical means.

[0013] A resonance unit of a frequency-modulated ultra-thin, ultra-sparse, low-frequency sound-absorbing device, characterized in that the resonance unit is an independent square resonance cavity structure, and its interior is a square air resonance cavity. The air resonance cavity is surrounded by two end faces and the first coiled channel and the second coiled channel with the same structure connected end to end. The two coiled channels are symmetrically distributed around the center; both the head and the tail of the first coiled channel and the second coiled channel respectively have a sound channel inlet communicating with the outside and a sound channel outlet extending towards the center of the resonant air cavity, so that the air resonance cavity communicates with the outside through the coiled channels; the sound channel inlet is formed by the outer wall of the first coiled channel or the second coiled channel being shorter than the inner wall; the wall thickness of the coiled channel is e, the side length of the resonance unit is a = 100e / 3, the width t of the coiled channel is: e / 2 ≤ t ≤ 19e / 6, and the distance b between the two sound channel outlets is: e / 2 ≤ b ≤ 85e / 3.

[0014] Furthermore, the resonance unit is prepared by 3D printing technology.

[0015] Furthermore, the material of the resonance unit is one of plexiglass and resin materials.

[0016] Further, the operating frequency range of the resonance unit is 100 - 250 Hz.

[0017] Further, the side length a of the resonance unit is 100 mm, the wall thickness e of the coiled channel is 3 mm, the width t of the coiled channel is 4 mm, and the distance b between the two-channel outlets is 8 mm.

[0018] The use of the resonance unit of the ultra-thin, ultra-sparse, low-frequency sound-absorbing device is characterized in that the resonance unit is placed in front of the wall, and the distance d between the resonance unit and the wall does not exceed 15 mm, for absorbing low-frequency sound waves.

[0019] Further, a plurality of the resonance units are arranged in a row and equidistantly in front of the wall. One outlet of the two coiled channels of the resonance unit faces the wall, and the other faces away from the wall; there is a gap between the resonance unit and the wall; the distance H between adjacent resonance units satisfies 2a ≤ H ≤ 7a.

[0020] The use of the resonance unit of the ultra-thin, ultra-sparse, low-frequency sound-absorbing device is characterized in that a combined unit is composed of six resonance units with different distances b between the two-channel outlets in the central cavity and widths t of the coiled channels, and then the composite units are arranged in a periodic and equidistant manner in front of the wall.

[0021] Further, the distances b between the two-channel outlets and the widths t of the coiled channels of the six resonance units in the combined unit are respectively:

[0022] The first resonance unit: b = 66 mm, t = 3 mm;

[0023] The second resonance unit: b = 8 mm, t = 4 mm;

[0024] The third resonance unit: b = 29 mm, t = 4.5 mm;

[0025] The fourth resonance unit: b = 8 mm, t = 5.5 mm;

[0026] The fifth resonance unit: b = 17 mm, t = 6 mm;

[0027] The sixth resonance unit: b = 70 mm, t = 2.5 mm;

[0028] The distance d between the resonance unit and the wall is 5 mm, and the center distance S between adjacent composite units is 696 mm.

[0029] Further, for sound absorption in a square space, at the intersection of the four side walls of the square space, the composite units arranged in an array in front of one of the two intersecting side walls are connected end to end with the composite units arranged in an array in front of the other side wall.

[0030] Compared with the prior art, the beneficial effects produced by the present invention are as follows:

[0031] First of all, the resonance unit of the frequency-modulated ultra-thin, ultra-sparse, and low-frequency sound-absorbing device proposed by the present invention can achieve an excellent sound-absorbing effect based on the intrinsic resonance mode. At a frequency of 141 Hz, the sound energy absorption rate reaches 0.99, and in the frequency range of 134.6 Hz - 147.4 Hz, the sound energy absorption rate exceeds 0.5, and its relative bandwidth is 9.1%. Further, by changing the width of the unit's curled channel and the distance between the curled channels, the working frequency band can be adjusted, and this resonance mode always exists and exhibits high-quality sound absorption performance. The size of the frequency-modulated ultra-thin, ultra-sparse, and low-frequency sound-absorbing device constructed by using the resonance unit of the present invention is sub-wavelength in depth, the unit thickness is 0.043λ, and the structural space occupancy ratio is 25%. The structure is simple, easy to process and prepare, and easy to integrate. Brief Description of the Drawings

[0032] Figure 1 It is a schematic cross-sectional structure diagram of the resonance unit of the frequency-modulated ultra-thin, ultra-sparse, and low-frequency sound-absorbing device of the present invention.

[0033] Figure 2 It is a three-dimensional view of the resonance unit of the frequency-modulated ultra-thin, ultra-sparse, and low-frequency sound-absorbing device prepared by 3D printing after removing one end face.

[0034] Figure 3 It is a schematic diagram of the experimental device of the frequency-modulated ultra-thin, ultra-sparse, and low-frequency sound-absorbing device of the present invention, where the resonance unit is a cross-sectional view.

[0035] Figure 4 It is a schematic plan view of the frequency-modulated ultra-thin, ultra-sparse, and low-frequency sound-absorbing device of the present invention, where the resonance unit is a cross-sectional view.

[0036] Figure 5 It is a spectrogram of the sound energy absorption rate of the sound-absorbing wall measured and simulated by the experimental device of the frequency-modulated ultra-thin, ultra-sparse, and low-frequency sound-absorbing device of the present invention.

[0037] Figure 6 It is a spectrogram of the sound energy absorption rate of the sound-absorbing wall corresponding to different parameters b simulated by the frequency-modulated ultra-thin, ultra-sparse, and low-frequency sound-absorbing device of the present invention.

[0038] Figure 7 It is a spectrogram of the sound energy absorption rate of the sound-absorbing wall corresponding to different parameters t simulated by the frequency-modulated ultra-thin, ultra-sparse, and low-frequency sound-absorbing device of the present invention.

[0039] Figure 8 It is a schematic structure diagram of the broadband sound-absorbing wall composed of the frequency-modulated ultra-thin, ultra-sparse, and low-frequency sound-absorbing device of the present invention, where the resonance unit is a cross-sectional view.

[0040] Figure 9 It is the spectrogram of the sound energy absorption rate for the simulation and experimental measurement of the broadband anechoic wall composed of the frequency modulation ultra-thin, ultra-sparse, and low-frequency sound absorption devices described in the present invention.

[0041] Figure 10 It is the structural schematic diagram of the broadband anechoic chamber composed of the frequency modulation ultra-thin, ultra-sparse, and low-frequency sound absorption devices described in the present invention.

[0042] Figure 11 It is the spectrogram of the sound energy absorption rate of the broadband anechoic chamber composed of the frequency modulation ultra-thin, ultra-sparse, and low-frequency sound absorption devices described in the present invention.

[0043] Figure 12 It is the total sound pressure field distribution diagram of the broadband anechoic chamber composed of the frequency modulation ultra-thin, ultra-sparse, and low-frequency sound absorption devices described in the present invention, corresponding to point A and point B in the spectrogram of the sound energy absorption rate of the anechoic chamber respectively.

[0044] Figure 13 It is the sound energy distribution diagram of the reflected sound field of the broadband anechoic chamber composed of the frequency modulation ultra-thin, ultra-sparse, and low-frequency sound absorption devices described in the present invention, corresponding to point A and point B in the spectrogram of the sound energy absorption rate of the anechoic chamber respectively.

[0045] In the figure: 1. Computer, 2. Data controller, 3. Power amplifier, 4. Sound source, 5. Miniature microphone, 6. Resonance unit, 7. Waveguide, 8. Wall, 9. Combination unit, 601. First coiled channel, 602. Second coiled channel, 603. Channel entrance, 604. Channel exit, 605. End face, 61. First resonance unit, 62. Second resonance unit, 63. Third resonance unit, 64. Fourth resonance unit, 65. Fifth resonance unit, 66. Sixth resonance unit. Specific embodiments

[0046] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited thereto.

[0047] Such as Figure 1As shown in the figure, the resonance unit 6 of the ultra-thin, ultra-sparse, and low-frequency sound-absorbing device proposed by the present invention is an independent square resonance cavity structure, and its internal is a square air resonance cavity. The air resonance cavity is formed by surrounding two end faces 605 and the first coiled channel 601 and the second coiled channel 602 with the same structure connected end to end. The two coiled channels are symmetrically distributed around the center; the first coiled channel 601 and the second coiled channel 602 each have a sound channel inlet 603 communicating with the outside at both ends and a sound channel outlet 604 extending towards the center of the resonant air cavity at both ends, so that the air resonance cavity communicates with the outside through the coiled channels; the sound channel inlet 603 is formed by the outer wall of the first coiled channel 601 or the second coiled channel 602 being shorter than the inner wall. The side length of the resonance unit 6 is a, the wall thickness of the coiled channel is e, the width of the coiled channel is t, and the distance between the two sound channel outlets 604 is b.

[0048] The sound energy absorption effect of the frequency-modulated ultra-thin, ultra-sparse, and low-frequency sound-absorbing device is based on the excitation of the intrinsic resonance mode of the resonance unit 6. The sound energy is inhaled into the unit, and during this process, it is dissipated through the viscous friction between the air and the wall in the narrow channel. The frequency-modulated ultra-thin, ultra-sparse, and low-frequency sound-absorbing device has an excellent low-frequency sound energy absorption effect. When the sound wave signal is vertically incident, the sound wave signal corresponding to the characteristic frequency will be almost completely absorbed by the resonance unit 6.

[0049] Changing the width of the coiled channel of the unit and the distance between the two channels can regulate the working frequency of the unit. Specifically, the wall thickness of the coiled channel of the resonance unit 6 is e, the side length a = 100e / 3, the width t of the coiled channel is e / 2 ≤ t ≤ 19e / 6, the distance b between the two sound channel outlets 604 is: e / 2 ≤ b ≤ 85e / 3, and the working frequency range is 100 - 250 Hz.

[0050] The resonance unit 6 is prepared by 3D printing technology, and the material used is one of plexiglass and resin materials.

[0051] Example 1

[0052] The resonance unit 6 is made by 3D printing technology, as Figure 2 shown. The side length of the made resonance unit 6 is a = 100 mm, the wall thickness e of the coiled channel is 3 mm, the width of the coiled channel is t = 4 mm, the distance between the two sound channel outlets 604 is b = 8 mm, and the parameters of the materials used are: the density of the resonance unit 6 is 1180 kg / m 3 , the longitudinal wave velocity is 2720 m / s and the transverse wave velocity is 1460 m / s, the density of air is 1.21 kg / m 3 and the sound velocity is 343 m / s.

[0053] To verify the sound absorption effect of the frequency modulation ultra-thin, ultra-sparse, low-frequency sound absorption device described in the present invention, the sound energy absorption performance of the sound absorption device was numerically simulated using the finite element method and experimentally verified by the double-sensor measurement method in the waveguide 7. The specific results of the simulation and experiment are as follows:

[0054] Figure 3 An experimental measurement device for the sound absorption performance of the sound absorption device includes: a computer 1, a data controller 2, a power amplifier 3, a sound source 4, a miniature microphone 5, a sample to be measured, and a waveguide 7. The experimental measurement device uses the double-sensor measurement method in the waveguide 7. The waveguide 7 is made of plexiglass, and its width is equal to the spacing between adjacent resonance units 6, meeting the hard boundary conditions of the sound field. The 3D-printed resonance unit 6 is placed at the right end inside the waveguide 7. The sound source 4 is a speaker array placed on the left side of the waveguide 7 and driven by the power amplifier 3. Two miniature microphones 5 extend into the waveguide through small holes to collect sound pressure and phase information and are collected by the data controller 2, and finally processed by the terminal computer 1. At the same time, all parameters of the simulation experiment are the same as those of the actual measurement, and the Figure 5 Spectrum diagrams of the sound energy absorption rates of the simulated and measured sound absorption devices are shown. It can be seen from the figure that the simulation results are in good agreement with the measurement results. The sound energy absorption rate reaches a peak at 141 Hz, approximately 0.99. In the frequency range of 134.6 Hz - 147.4 Hz, the sound energy absorption rate exceeds 0.5, and its relative bandwidth is 9.1%, showing excellent low-frequency sound absorption performance.

[0055] Figure 6 and Figure 7 Are respectively the spectrum diagrams of the sound energy absorption rates of the resonance unit 6 for simulating and measuring different spacings b between the two-channel outlets 604 and the width t of the coiled channel. It can be seen from the figure that when other structural parameters remain unchanged, by adjusting the width t of the coiled channel and cooperating with changing the spacing b between the two-channel outlets 604, continuous regulation of the working frequency can be achieved in the range of 100 Hz - 180 Hz while maintaining high-quality sound absorption performance. By further expanding the adjustment range of the spacing b between the two-channel outlets 604 and the width t of the coiled channel, the working frequency of the resonance unit 6 can be increased to 250 Hz. In addition, the working frequency of the resonance unit 6 scales proportionally with the overall structural parameters. When all structural parameters of the resonance unit 6 are doubled, its working frequency is reduced to half of the original. Conversely, if all structural parameters of the resonance unit 6 are reduced to half of the original, its working frequency is increased to 2 times the original.

[0056] Example 2: Sound absorption device one

[0057] A plurality of resonance units 6 are arranged at equal intervals in front of a wall 8, with a gap left between the resonance unit 6 and the wall 8, and the distance d between the resonance unit 6 and the wall 8 does not exceed 15 mm. The distance 2a between adjacent resonance units 6 in the sound-absorbing device satisfies 2a ≤ H ≤ 7a. The sound wave signal is incident perpendicular to the wall surface, that is, the exits of the two coiled channels of each resonance unit 6, one faces the wall 8 and the other faces away from the wall 8. This arrangement constitutes a frequency-modulated ultra-thin, ultra-sparse, low-frequency sound-absorbing device, as Figure 3 shown. In this embodiment, the structural parameters and material parameters of the resonance unit 6 are the same as those in Embodiment 1. The width of the gap between the resonance unit 6 and the wall 8 is d = 5 mm, and the distance between adjacent resonance units 6 is H = 4a = 400 mm.

[0058] The thickness of the resonance unit 6 is 0.043 of the sound signal wavelength, and the structural space occupancy is 25%. The resulting sound-absorbing device has the structural characteristics of deep sub-wavelength and ultra-sparse.

[0059] Embodiment 3: Sound-absorbing device two

[0060] Figure 8 Another frequency-modulated ultra-thin, ultra-sparse, low-frequency sound-absorbing device constructed for the resonance unit 6. First, a combination unit 9 is formed by arranging six resonance units 6 with different distances b between the two-channel exits 604 and widths t of the coiled channels in a row at equal intervals; then the combination unit 9 is periodically arranged in front of the wall 8 to form an array of combination units 9, constituting a sound-absorbing device. The sound wave signal is incident perpendicularly, that is, the exits of the two coiled channels of each resonance unit 6, one faces the wall 8 and the other faces away from the wall 8. The gap h between adjacent resonance units 6 in the combination unit 9 is 16 mm, and the b and t of the six resonance units 6 are as follows:

[0061] The first resonance unit 61: b = 66 mm, t = 3 mm;

[0062] The second resonance unit 62: b = 8 mm, t = 4 mm;

[0063] The third resonance unit 63: b = 29 mm, t = 4.5 mm;

[0064] The fourth resonance unit 64: b = 8 mm, t = 5.5 mm;

[0065] The fifth resonance unit 65: b = 17 mm, t = 6 mm;

[0066] The sixth resonance unit 66: b = 70 mm, t = 2.5 mm.

[0067] The distance d between the resonance unit 6 and the wall 8 is 5 mm, and the center distance S between adjacent combination units 9 is 696 mm.

[0068] Figure 9 This is the spectrogram of the sound energy absorption rate of the noise elimination device in this embodiment obtained from simulation and actual measurement. The experimental measurement method used is the same as that in Embodiment 1. It can be seen from the figure that in the frequency range of 116.4 Hz - 174.8 Hz, the sound energy absorption rate of the noise elimination device in this embodiment exceeds 0.5, and the relative bandwidth reaches 40%. It shows good broadband low-frequency sound absorption performance; moreover, the simulation results are basically in line with the experimental results.

[0069] Embodiment 4: Noise elimination device for a square anechoic chamber

[0070] In this embodiment, the noise elimination device is applicable to a square space. It is formed by arranging the combination units 9 described in Embodiment 2 in a head-to-tail connection manner in front of the four side walls 8 of the square anechoic chamber, as Figure 10 shown. That is, at the intersection of the four side walls 8 of the square space, the combination units 9 arranged in front of one of the two intersecting side walls 8 are connected head-to-tail with the combination units 9 arranged in front of the other side wall 8. The number of groups N of the combination units 9 arranged on each wall is 9, and the cylindrical sound source is set at the center position O of the square anechoic chamber. Figure 11 This is the spectrogram of the simulated sound energy absorption rate of the anechoic chamber. It can be seen from the figure that in the frequency range of 117 Hz - 172.4 Hz, the sound energy absorption rate exceeds 0.5, and the relative bandwidth reaches 38.3%. The sound absorption performance is similar to that in Embodiment 2, demonstrating excellent omnidirectional and broadband low-frequency sound absorption performance.

[0071] Figure 12 These are respectively the total sound pressure field distribution diagrams of the anechoic chamber corresponding to point A (149 Hz) and point B (161 Hz) obtained from simulation and Figure 11 in, Figure 13 These are respectively the sound energy distribution diagrams of the reflected sound field corresponding to Figure 12 in. It can be concluded from the figure that the total sound pressure field distribution diagram of the anechoic chamber is very close to the sound pressure field distribution diagram of the free field space, indicating that almost all incident sound waves in all directions are absorbed by the anechoic chamber, and the sound energy distribution diagram of the reflected sound field also confirms that the reflected sound waves from the side walls 8 of the anechoic chamber are very weak. Therefore, the noise elimination device has good omnidirectional and broadband low-frequency sound absorption performance. In this embodiment, the thickness of the side walls 8 of the anechoic chamber is only 105 mm, which is about 1 / 10 of the thickness of the side walls 8 of the traditional anechoic chamber using sound-absorbing cotton, solving the problem that the performance of traditional sound-absorbing / noise-insulating materials strictly follows the mass density law and it is necessary to increase the thickness or surface density of the materials to improve the noise insulation, thus facing the problems of large thickness and high density in the low-frequency range.

[0072] In summary, the frequency-tunable ultra-thin, ultra-sparse, and low-frequency sound-absorbing device proposed by the present invention has an array composed of resonance units backed against a wall 8 as the main body. The resonance unit consists of a square air resonance cavity in the center and two symmetrically arranged long and narrow coiled channels surrounding it to form a square resonance cavity, where the central square cavity communicates with the outside through the two coiled channels. The designed sound-absorbing device has a good low-frequency sound absorption effect. By adjusting the width of the coiled channels of the resonance unit and the separation distance between the two coiled channels, the working frequency band of the sound-absorbing device can be regulated, and its adjustable frequency range is 100 Hz - 250 Hz. The thickness of the resonance unit is 0.043λ, featuring a deep sub-wavelength characteristic, which solves the problem that traditional sound-absorbing materials are too thick in the low-frequency range. The frequency-tunable ultra-thin, ultra-sparse, and low-frequency sound-absorbing device has an extremely wide unit spacing, with a structural space occupancy of 25%. By combining resonance units with different parameters to form a composite sound-absorbing device, the purpose of broadband sound absorption can be achieved without changing the overall structural thickness.

[0073] The frequency-tunable ultra-thin, ultra-sparse, and low-frequency sound-absorbing device proposed by the present invention has high-quality sound-absorbing performance, simple structure, easy to process and manufacture, convenient to install, and can be widely applied in the fields of noise control, architectural acoustics, environmental protection, etc.

[0074] The described embodiments are the preferred embodiments of the present invention, but the present invention is not limited to the above embodiments. Without departing from the essence of the present invention, any obvious improvements, substitutions, or variations that those skilled in the art can make all fall within the protection scope of the present invention.

Claims

1. A resonance unit of an ultra-thin, ultra-sparse, low-frequency sound-absorbing device, characterized in that, The resonance unit is an independent square resonance cavity structure, and its interior is a square air resonance cavity. The air resonance cavity is formed by enclosing two end faces and the first and second coiled channels with the same structure end to end. The two coiled channels are symmetrically distributed about the center; both the beginning and the end of the first and second coiled channels respectively have a sound channel inlet communicating with the outside and a sound channel outlet extending towards the center of the resonance air cavity, so that the air resonance cavity communicates with the outside through the coiled channels; the sound channel inlet is formed by the outer wall of the first or second coiled channel being shorter than the inner wall; the wall thickness of the coiled channel is e , and the side length of the resonance unit is a = 100 e / 3. The width of the coiled channel t is: e / 2 ≤ t ≤ 19 e / 6. The distance between the two sound channel outlets b is: e / 2 ≤ b ≤ 85 e / 3.

2. The resonance unit of the ultra-thin, ultra-sparse, low-frequency sound-absorbing device according to claim 1, characterized in that, The resonance unit is prepared by 3D printing technology.

3. The resonance unit of the ultra-thin, ultra-sparse, and low-frequency sound-absorbing device according to claim 1, characterized in that, The material of the resonance unit is one of plexiglass and resin material.

4. The resonance unit of the ultra-thin, ultra-sparse, and low-frequency noise elimination device according to claim 1, characterized in that The operating frequency range of the resonance unit is 100 - 250 Hz.

5. The resonance unit of the ultra-thin, ultra-sparse, low-frequency sound-absorbing device according to claim 1, characterized in that The side length of the resonance unit a = 100 mm, the wall thickness of the coiled channel e = 3 mm, the width of the coiled channel t = 4 mm, the distance between the two channel outlets b = 8 mm.

6. Use of the resonance unit of the ultra-thin, ultra-sparse, low-frequency noise elimination device according to any one of claims 1-5, characterized in that, The resonance unit is placed in front of the wall, and the distance d between the resonance unit and the wall does not exceed 15 mm, which is used to absorb low-frequency sound waves.

7. Use of the resonance unit according to claim 6, characterized in that, A plurality of the resonance units are arranged in a row and equidistantly in front of a wall. The exits of the two coiled channels of the resonance unit are one facing the wall and the other facing away from the wall; the distance between adjacent resonance units is 2 a ≤ H ≤7 a 。 8. Use of the resonance unit of the ultra-thin, ultra-sparse, low-frequency sound-absorbing device according to any one of claims 1-5, characterized in that, Six two coiled channel outlets with different spacings in the central cavity b and resonant units with different widths t of the coiled channels form a combined unit, and then the combined units are arranged periodically at equal intervals in front of the wall.

9. Use of the resonance unit according to claim 8, characterized in that, The distance between the two-channel outlets of the six resonance units in the combined unit b and the width t of the coiled channel are respectively as follows: The first resonance unit: b = 66 mm, t = 3 mm; The second resonance unit: b = 8 mm, t = 4 mm; The third resonance unit: b = 29 mm, t = 4.5 mm; The fourth resonance unit: b = 8 mm, t = 5.5 mm; The fifth resonance unit: b = 17 mm, t = 6 mm; , The sixth resonance unit: b = 70 mm, t = 2.5 mm; The distance between the resonance unit and the wall d = 5 mm, and the center distance between adjacent combined units S = 696 mm.

10. Use of the resonance unit according to claim 9, characterized in that, For noise elimination in a square space, at the intersection of the four walls of the square space, the composite units arranged in an array in front of one of the two intersecting walls are connected end to end with the combined units arranged in an array in front of the other wall.

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