A frequency modulation ultra-thin, broadband, ultra-low frequency silencing unit and its use

Abstract

The present invention discloses a frequency-modulated ultra-thin, broadband, ultra-low frequency sound-absorbing unit, comprising two mutually nested and centrally symmetrical curled frames and two end faces fixed at the upper and lower ends of the curled frames. The curled frames are formed by a square spiral, a rectangular air cavity is formed in the center of the two curled frames, and two curled channels are formed between the two curled frames. The curled channels are spiral squares, and the rectangular air cavity is connected to the outside world through the curled channels. The two end faces seal the curled channels and the upper and lower ends of the rectangular air cavity. The ultra-low frequency sound-absorbing unit has a thickness of 0.021λ and has a deep subwavelength characteristic. When the width t of the curled channel is 2 mm, the sound energy absorption rate reaches a peak of about 0.98 at 73 Hz, and the sound energy absorption rate exceeds 0.5 in the frequency range of 66.4-80 Hz. Its relative bandwidth is 18.3%, which can simultaneously ensure the thickness of the sound-absorbing unit and the sound absorption effect in the ultra-low frequency range, thereby achieving good sound absorption performance of the ultra-thin sound-absorbing unit in the ultra-low frequency range.

Description

Technical Field

[0001] The present invention relates to the field of noise control, in particular to a frequency modulation ultra-thin, broadband, ultra-low frequency silencing unit and applications thereof. Background Art

[0002] Noise pollution is the third most common public hazard, after air and water pollution. In the manufacturing sector, ultra-low-frequency (ULF) noise is generated by the power systems, mechanical vibrations, and aerodynamics of mechanical equipment. Intense ULF noise can cause equipment failure or even damage, while also seriously harming the physical and mental health of operators. An effective method for noise control is to reduce its environmental impact by blocking or absorbing noise during its propagation. The performance of traditional anechoic / soundproofing materials strictly follows the law of mass density. This leads to the limitations of excessive thickness and density in the ULF range, limiting their application. In recent years, the emergence of acoustic metamaterials, particularly acoustic metasurfaces, has provided a new approach to overcoming the limitations of traditional anechoic / soundproofing materials. Acoustic metasurfaces are ultrathin, open, and easily controllable. Their exceptional acoustic wave manipulation capabilities provide theoretical solutions and technical pathways for the design of ultra-thin, open ULF anechoic / soundproofing structures.

[0003] Traditional silencer units follow the law of mass density. Traditional silencer units must increase the sound insulation by increasing the thickness or surface density of the unit. The thickness generally needs to reach 1 / 4 to 1 / 2 of the working wavelength. Therefore, they face the problem of large thickness and high density in the ultra-low frequency range. Or after ensuring the thickness and density, in the ultra-low frequency range, the sound energy density is low, the sound energy loss efficiency is not high, and the sound insulation effect is poor. Therefore, traditional silencer units cannot simultaneously guarantee the thickness of the silencer unit and the sound insulation effect in the ultra-low frequency range. Summary of the Invention

[0004] In order to simultaneously ensure the thickness of the silencer unit and the silencer effect in the ultra-low frequency range, the present invention provides a frequency-modulated ultra-thin, broadband, ultra-low frequency silencer unit and its use. The curled frame adopts a square spiral to form two curled channels and a rectangular air cavity. The thickness of the silencer unit meets the deep subwavelength characteristics, which can simultaneously ensure the thickness of the silencer unit and the silencer effect in the ultra-low frequency range, so that the ultra-thin silencer unit has good sound absorption performance in the ultra-low frequency range.

[0005] The technical solution adopted by the present invention is:

[0006] A frequency-modulated ultra-thin, broadband, ultra-low frequency silencer unit comprises two mutually nested and centrally symmetrical curled frames and two end faces fixed at the upper and lower ends of the curled frames. The curled frames are formed using square spirals, a rectangular air cavity is formed in the centers of the two curled frames, and two curled channels are formed between the two curled frames. The curled channels are spiral squares, and the rectangular air cavity is connected to the outside world through the curled channels. The two end faces seal the curled channels and the upper and lower ends of the rectangular air cavity. The ultra-low frequency silencer unit has a thickness a, a wall thickness e, and a width t of the curled channels.

[0007] Furthermore, the thickness of the ultra-low frequency muffler unit is a=50e, the width t of the curled channel is in the range of 0.75e≤t≤2.25e; and the number of spiral turns of the curled frame is 1.75 turns.

[0008] Furthermore, the curled frame wall thickness e is 2 mm.

[0009] Furthermore, the curled frame and the two end surfaces are made of organic glass or resin.

[0010] The frequency-modulated ultra-thin, broadband, ultra-low frequency silencing unit is used for silencing ultra-low frequency sound waves. The silencing frequency range is 60-115 Hz, and the silencing frequency is adjusted by changing the ratio of the width t of the curled channel and the wall thickness e of the curled frame.

[0011] The frequency-modulated ultra-thin, broadband, ultra-low frequency silencer unit is used for silencing inside a building space or equipment. Several ultra-low frequency silencer units with the same parameters are arranged in an array in front of the inner wall of the building space or equipment. One of the two curled channels of the ultra-low frequency silencer unit faces the inner wall of the building space / equipment, and the other faces away from the inner wall of the building space / equipment.

[0012] Furthermore, the distance H1 between adjacent ultra-low frequency silencer unit arrays is 110 mm, and the distance d1 between the ultra-low frequency silencer unit and the inner wall of the building space / equipment is 5 mm.

[0013] The frequency-modulated ultra-thin, broadband, ultra-low frequency silencer unit is used for silencer in square pipes / corridors / channels. Multiple silencer modules are arranged in sequence in the square pipes / corridors / channels. The silencer module includes three recessed outer frames respectively located at the three vertices of a right triangle, two of which are located on the same side wall of the square pipe / corridor / channel, and three ultra-low frequency silencer units with the same parameters. The ultra-low frequency silencer units are respectively located in an outer frame and surrounded on three sides. The channel openings of the two curled channels of the ultra-low frequency silencer unit are one facing the outer frame and the other facing the center of the square pipe / corridor / channel.

[0014] Furthermore, the gap width d2 between the ultra-low frequency silencer unit and the outer frame on three sides is 5 mm, the outer frame width H2 is 110 mm, the center distance between the two recessed outer frames located on the same side wall of the square pipe / corridor / channel is L1 = 1100 mm, and the center distance between adjacent silencer modules is L1' = 2200 mm.

[0015] The frequency-modulated ultra-thin, broadband, ultra-low frequency silencer unit is used for silencer in square pipes / corridors / channels, and multiple silencer modules are arranged in sequence on the inner wall of the square pipe / corridor / channel. The silencer module includes three silencer unit groups respectively located at the three vertices of a right triangle, and two of them are located on the same side wall of the square pipe / corridor / channel. The silencer unit group includes five recessed outer frames arranged in sequence along the inner side of the pipe, and five ultra-low frequency silencer units. The widths t of the curled channels of the five ultra-low frequency silencer units are different. The ultra-low frequency silencer units are respectively located in an outer frame and are surrounded on three sides. The channel openings of the two curled channels of the ultra-low frequency silencer unit are one facing the outer frame and the other facing the center of the square pipe / corridor / channel.

[0016] Furthermore, the gap width d2 between the ultra-low frequency silencer unit and the three sides of the outer frame is 5mm, the curled channel width t of the five ultra-low frequency silencer units arrayed in the ultra-low frequency silencer unit group is 1.5mm, 2mm, 2.5mm, 3mm, and 3.5mm respectively, the distance l between adjacent ultra-low frequency silencer units in the ultra-low frequency silencer unit group is 130mm, the distance L2 between the two ultra-low frequency silencer unit groups arranged on the same side wall of the square pipe / corridor / channel in the silencer module is 1100mm, and the center distance L2' between adjacent silencer modules is 2200mm.

[0017] The beneficial effects of the present invention are:

[0018] 1. The frequency-modulated ultra-thin, broadband, ultra-low-frequency silencing unit of the present invention has a thickness of 0.021λ and has deep subwavelength characteristics. When the width t of the curled channel is 2 mm, the sound energy absorption rate reaches a peak of approximately 0.98 at 73 Hz. The sound energy absorption rate exceeds 0.5 in the frequency range of 66.4-80 Hz, and its relative bandwidth is 18.3%. It can simultaneously ensure the thickness of the silencing unit and the silencing effect in the ultra-low frequency range, and realize that the ultra-thin silencing unit has good sound absorption performance in the ultra-low frequency range.

[0019] 2. When the sound wave incident angle θ of the frequency-modulated ultra-thin, broadband, ultra-low frequency silencer unit of the present invention increases to 70°, the sound energy absorption rate at the resonance frequency can reach 0.85. The frequency-modulated ultra-thin, broadband, ultra-low frequency silencer unit has strong robustness to the sound wave incident angle θ.

[0020] 3. The frequency-modulated ultra-thin, broadband, ultra-low frequency silencer unit of the present invention can adjust the operating silencer frequency by controlling the ratio of the width t of the curled channel and the wall thickness e of the curled frame. The adjustable silencer frequency range is 60-115 Hz, avoiding the single curled space structure causing the operating silencer frequency band to be too narrow, especially in the ultra-low frequency range. A too narrow operating silencer frequency band will seriously affect the actual silencer effect of the curled space structure.

[0021] 4. The frequency-modulated, ultra-thin, broadband, ultra-low-frequency anechoic unit of the present invention can be applied to architectural spaces / equipment and other occasions. It can absorb sound waves incident at almost all angles, has good sound absorption effects, and can achieve high-efficiency sound absorption at ultra-low frequencies. In addition, the thickness a of the ultra-low-frequency anechoic unit has a deep subwavelength characteristic. While ensuring the sound absorption effect, it occupies a small space. Especially when applied to equipment, it can reduce the overall volume to a certain extent.

[0022] 5. The frequency-modulated, ultra-thin, broadband, ultra-low-frequency muffler unit described in the present invention is applied to square ducts / corridors / channels, achieving excellent sound absorption. In particular, the fourth embodiment, by controlling the ratio of the ultra-low-frequency muffler units with different curving channel widths t and curving frame wall thicknesses e, avoids a single curving spatial structure and achieves a sound energy absorption rate exceeding 0.5 within the frequency range of 59-110 Hz. Its relative bandwidth reaches 60.4%, and its relative width meets the ultra-wideband requirement. Furthermore, the sound energy absorption rate exceeds 0.8 within the frequency range of 63-105 Hz, and the average sound energy absorption rate reaches 0.92, achieving high-efficiency sound energy absorption in the ultra-low frequency range. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a cross-sectional view of a frequency-modulated ultra-thin, broadband, ultra-low frequency silencer unit according to an embodiment of the present invention.

[0024] Figure 2 This is an experimental measurement device for the sound absorption performance of the frequency-modulated ultra-thin, broadband, ultra-low frequency silencer unit described in Example 1 of the present invention.

[0025] Figure 3 This is a measurement principle diagram of the experimental measurement device described in Example 1 of the present invention.

[0026] Figure 4 This is a 3D printed sample image of the ultra-low frequency silencer unit with one end face removed as described in Example 1 of the present invention.

[0027] Figure 5 This is a graph showing the relationship between the sound energy absorption rate and frequency of the ultra-low frequency silencer unit described in Example 1 of the present invention.

[0028] Figure 6 This is a relationship diagram between the sound energy absorption rate of the ultra-low frequency silencer unit described in Example 1 of the present invention and the width and resonance frequency of the curled channel.

[0029] Figure 7 This is a schematic diagram of the relationship between the sound energy absorption rate of the ultra-low frequency silencer unit and the incident angle of the sound wave according to the first embodiment of the present invention. The schematic diagram of the frequency-modulated ultra-thin, broadband, ultra-low frequency silencer unit in the figure is a cross-sectional view.

[0030] Figure 8 This is a schematic diagram of the ultra-low frequency silencer unit described in Example 2 of the present invention being used for a wall / equipment, in which the schematic diagram of the frequency-modulated ultra-thin, broadband, ultra-low frequency silencer unit is a cross-sectional view.

[0031] Figure 9 This is a schematic diagram of the ultra-low frequency silencer unit and outer frame described in Example 3 and Example 4 of the present invention. The schematic diagram of the frequency-modulated ultra-thin, broadband, ultra-low frequency silencer unit in the figure is a cross-sectional view.

[0032] Figure 10 This is a schematic diagram of the silencer module described in Example 3 of the present invention, in which the schematic diagram of the frequency-modulated ultra-thin, broadband, ultra-low frequency silencer unit is a cross-sectional view.

[0033] Figure 11 This is a schematic diagram of the ultra-low frequency silencer unit described in Example 3 of the present invention used in a square pipe / corridor / channel. The schematic diagram of the frequency-modulated ultra-thin, broadband, ultra-low frequency silencer unit in the figure is a cross-sectional view.

[0034] Figure 12 This is a relationship diagram between the sound energy absorption rate and frequency of the silencer device when the ultra-low frequency silencer unit described in Example 3 of the present invention is used in a square pipe.

[0035] Figure 13 This is a schematic diagram of the silencer module described in Example 4 of the present invention, in which the schematic diagram of the frequency-modulated ultra-thin, broadband, ultra-low frequency silencer unit is a cross-sectional view.

[0036] Figure 14 This is a schematic diagram of the ultra-low frequency silencer unit described in Example 4 of the present invention used in a square pipe / corridor / channel. The schematic diagram of the frequency-modulated ultra-thin, broadband, ultra-low frequency silencer unit in the figure is a cross-sectional view.

[0037] Figure 15 This is a graph showing the relationship between the sound energy absorption rate and frequency when the ultra-low frequency silencer unit described in Example 4 of the present invention is used in a square pipe.

[0038] Description of reference numerals:

[0039] 1. Curled frame; 2. Curled channel; 3. Rectangular air cavity; 4. Computer; 5. Data controller; 6. Power amplifier; 7. Sound source; 8. Waveguide; 9. Micro microphone; 10. Outer frame. DETAILED DESCRIPTION

[0040] The present invention will be further described in detail below with reference to the specific embodiments of the drawings, but the protection scope of the present invention is not limited thereto.

[0041] Example 1

[0042] Figure 1 This is a cross-sectional view of an ultra-thin, broadband, ultra-low frequency silencer unit. The ultra-low frequency silencer unit includes a curled frame 1 that is nested and centrally symmetrical with each other and two end faces fixed at the upper and lower ends of the curled frame 1. The curled frame 1 and the two end faces are made of organic glass or resin. The wall thickness e of the curled frame 1 is 2 mm. The curled frame 1 is made of a square spiral. A rectangular air cavity 3 is formed in the center of the two curled frames 1, and two curled channels 2 are formed between the two curled frames 1. The width t of the curled channel 2 ranges from 0.75e≤t≤2.25e. The curled channel 2 is a spiral square. The rectangular air cavity 3 is connected to the outside world through the curled channel 2. The two end faces seal the curled channel 2 and the upper and lower ends of the rectangular air cavity 3. The thickness of the ultra-low frequency silencer unit is a=50e, and the number of spiral turns of the curled frame 1 is 1.75 turns.

[0043] Figure 2 The invention relates to an experimental measurement device for the sound absorption performance of the frequency-modulated ultra-thin, broadband, and ultra-low frequency silencing unit, comprising a computer 4, a data controller 5, a power amplifier 6, a waveguide 8, a sound source 7, and a miniature microphone 9. The data controller 5 is electrically connected to the computer 4 to realize the control of the data controller 5 by the computer 4 and the data transmission of the data controller 5. The data controller 5 is electrically connected to the sound source 7 through the power amplifier 6 to realize the start and stop of the sound source 7 and the control of the frequency of the sound emitted by the sound source 7. The sound source 7 is arranged on one side of the waveguide 8 to provide experimental sound waves to the waveguide 8. The waveguide 8 is made of organic glass, and the other side of the waveguide 8 is used to place the frequency-modulated ultra-thin, broadband, and ultra-low frequency silencing unit. Two miniature microphones 9 are also provided on the waveguide 8 and connected to the data controller 5 for collecting sound wave signals inside the waveguide 8 and transmitting them to the computer 4 through the data controller 5. The computer 4 processes the sound wave signals collected by the miniature microphone 9, and combines the sound wave information emitted by the sound source 7 to obtain a sound energy absorption rate spectrum of the frequency-modulated ultra-thin, broadband, and ultra-low frequency silencing unit.

[0044] Figure 3 This is the measurement principle diagram of the experimental measurement device. The computer 4 drives the sound source 7 through the data controller 5 and the power amplifier 6 to generate a sound wave signal in the waveguide 8 and incident on the sample surface. The sample absorbs the sound wave and reflects part of the sound wave. The two micro-microphones 9 on the waveguide 8 collect the sound wave signal. The micro-microphone close to the sound source of the two micro-microphones 9 is called the first micro-microphone, and the micro-microphone close to the sample is called the second micro-microphone. The distance between the two micro-microphones 9 is s, and the distance between the second micro-microphone and the edge of the sample is l. The incident sound wave signal is set to PI , the reflected sound wave signal is P R , the sound wave signals collected by the first micro-microphone and the second micro-microphone are P2 and P3 respectively, and the sound wave signals collected by the two micro-microphones 9 can be expressed as

[0045] P2=P I e ik(s+l) +P R e -ik(s+l) (1)

[0046] P3=P I e ikl +P R e -ikl (2)

[0047] Among them, e is a natural constant, i is an imaginary unit, λ is the wavelength of the sound wave, and k is the wave number in the air. The wave number k in the air can be expressed as

[0048]

[0049] Combining equations (1) and (2), we can calculate the incident sound wave signal P I and the reflected sound wave signal is P R They are:

[0050]

[0051]

[0052] The acoustic reflection coefficient R of the sample surface is

[0053]

[0054] The sound energy absorption rate α is

[0055] α=1-R 2 (7)

[0056] like Figure 4 This is a 3D printed sample of a ULF anechoic unit. The width t of the curled channel 2 of the ULF anechoic unit sample is 2mm, the wall thickness e of the curled frame 1 is 2mm, the thickness of the ULF anechoic unit sample is a=50e=100mm, and the number of spiral turns of the curled frame 1 is 1.75. The material used for the ULF anechoic unit sample is photosensitive resin with a density of 1180kg / m 3 , longitudinal wave velocity is 2720m / s and transverse wave velocity is 1460m / s.

[0057] The ultra-low frequency silencing unit sample is placed in the waveguide 8, with the opening of one of the curved channels 2 of the ultra-low frequency silencing unit sample facing the sound source 7, and the sound frequency emitted by the sound source 7 is changed. Several points are evenly selected within the range of 50Hz-120Hz, and the sound energy absorption rate of the ultra-low frequency silencing unit sample at different frequencies is experimentally measured. The following is obtained: Figure 5 The relationship between the sound energy absorption rate and frequency of the FM ultra-thin, broadband, ultra-low frequency anechoic unit is shown in the figure. The environmental parameters during the experiment were the air density of 1.21 kg / m 3 , the speed of sound is 343m / s.

[0058] Through COMSO simulation, the width t of the curled channel 2 is 2 mm, the wall thickness e of the curled frame 1 is 2 mm, the number of spiral turns of the curled frame 1 is 1.75, the thickness a = 50e = 100 mm, and the material density is 1180 kg / m 3 The ultra-low frequency anechoic unit has a longitudinal wave velocity of 2720m / s and a shear wave velocity of 1460m / s. The simulated environmental parameters are an air density of 1.21kg / m 3 , the sound speed is 343m / s, the sound frequency is adjusted in the range of 50Hz-120Hz, and the sound energy absorption rate of the ultra-low frequency silencer unit at different frequencies is simulated and measured, and the following is obtained: Figure 5 The relationship between the sound energy absorption rate and frequency of the FM ultra-thin, broadband, ultra-low frequency anechoic unit is shown in the figure. Figure 5 It can be seen that the simulation data is in good agreement with the experimental data. The acoustic energy absorption rate reaches its peak at 73Hz, which is the resonant frequency. The acoustic energy absorption rate is about 0.98. In the frequency range of 66.4-80Hz, the acoustic energy absorption rate exceeds 0.5, and its relative bandwidth is 18.3%. The wavelength λ is

[0059]

[0060] Where v is the speed of sound and f is the frequency.

[0061] Based on a sound velocity of 343 m / s and a sound frequency of 73 Hz when the sound energy absorption rate reaches its peak, the wavelength λ at this time is calculated to be 4.70 m. The thickness a of the ultra-low frequency muffler unit is 100 mm. The proportional relationship between the thickness a and the wavelength λ is calculated to obtain the ultra-low frequency muffler unit thickness a = 0.021λ. This shows that the ultra-low frequency muffler unit sample has a deep subwavelength characteristic, which can simultaneously ensure the thickness of the muffler unit and the muffler effect in the ultra-low frequency range, achieving broadband sound absorption performance of the ultra-thin muffler unit in the ultra-low frequency range.

[0062] Through COMSO simulation, the curled frame 1 is constructed with a wall thickness e of 2 mm, a spiral number of 1.75 turns, a thickness a of 100 mm, and a material density of 1180 kg / m 3 The ultra-low frequency anechoic unit has a longitudinal wave velocity of 2720m / s and a shear wave velocity of 1460m / s. The simulated environmental parameters are an air density of 1.21kg / m 3 , the speed of sound is 343m / s. By changing the width t of the curled channel 2, the sound energy absorption rate of the ultra-low frequency anechoic unit with different widths t at different frequencies is simulated and measured, and the relationship between the sound energy absorption rate, width t and resonance frequency is obtained as shown in the figure below. Figure 6 As shown, it can be seen that the frequency-modulated ultra-thin, broadband, ultra-low frequency silencer unit can adjust the working resonance frequency by adjusting the ratio of the width t of the curled channel 2 and the wall thickness e of the curled frame. While ensuring the sound energy absorption rate, the width t of the curled channel 2 is 1.5mm~4.5mm, that is, in the range of 0.75e~2.25e, and the adjustment frequency range is 60-115Hz.

[0063] Through COMSO simulation, the curled frame 1 is constructed with a wall thickness e of 2 mm, a width t of 2 mm for the curled channel 2, 1.75 turns of the spiral of the curled frame 1, a thickness a of 100 mm, and a material density of 1180 kg / m 3 The ultra-low frequency anechoic unit has a longitudinal wave velocity of 2720m / s and a shear wave velocity of 1460m / s. The simulated environmental parameters are an air density of 1.21kg / m 3 , the sound speed is 343m / s, and the angle between the channel opening of the two curled channels 2 and the radial direction of the waveguide 8 is adjusted to adjust the sound wave incident angle θ. The sound wave incident angle θ is set to 30°, 70° and 80° respectively. The sound energy absorption rate of the ultra-low frequency anechoic unit at different sound wave incident angles θ and different frequencies is simulated and measured. The relationship between the sound energy absorption rate of the frequency modulated ultra-thin, broadband, ultra-low frequency anechoic unit and the sound wave incident angle θ is shown in the figure below. Figure 7 As shown, it can be seen that when the sound wave incident angle θ increases to 70°, the sound energy absorption rate can reach 0.85 at the resonance frequency, so the ultra-low frequency silencer unit has strong robustness to the sound wave incident angle θ.

[0064] Example 2

[0065] like Figure 8The diagram shows a schematic diagram of the ultra-low frequency muffler unit used in a building space / equipment. In Example 1, several parameters are identical: the ultra-low frequency muffler units are arranged in an array in front of the inner wall of the building space / equipment. The wall thickness e of the ultra-low frequency muffler unit's curved frame 1 is 2 mm, the width t of the curved channel 2 is 0.75e≤t≤2.25e, the thickness a of the ultra-low frequency muffler unit is 50e, and the openings of the two curved channels 2 of the ultra-low frequency muffler unit face the inner wall of the building space / equipment, while the other faces away from the inner wall. The ultra-low frequency muffler unit array spacing H1 is 110 mm, and the spacing d1 between the ultra-low frequency muffler unit and the inner wall of the building space / equipment is 5 mm. The ultra-low frequency muffler unit can be used in building spaces and equipment casings for sound absorption and sound insulation, reducing noise pollution.

[0066] The ultra-low frequency muffler unit exhibits strong robustness against sound wave incident angles θ. Therefore, when applied to a building space or equipment, it can absorb sound waves incident at nearly all angles, achieving excellent sound absorption and highly efficient sound absorption at ultra-low frequencies. Furthermore, the ultra-low frequency muffler unit has a deep subwavelength thickness a, ensuring effective sound absorption while occupying a small space. This can significantly reduce the overall volume of equipment, particularly when applied to equipment.

[0067] Example 3

[0068] like Figure 9-11 As shown, the ultra-low frequency muffler unit can also be used for muffler in square ducts / corridors / channels. Multiple muffler modules are arranged in sequence within the square duct / corridor / channel. The muffler module includes three recessed outer frames 10 located at the three vertices of a right triangle, two of which are located on the same side wall of the square duct / corridor / channel, and three ultra-low frequency muffler units with the same parameters as those described in Example 1. The width H2 of the outer frame 10 is 110 mm. The ultra-low frequency muffler units are each located within an outer frame 10 and surrounded on three sides. The width d2 of the gap between the ultra-low frequency muffler unit and the outer frame 10 is 5 mm. The openings of the two curved channels 2 of the ultra-low frequency muffler unit are one facing the outer frame 10 and the other facing the center of the square duct / corridor / channel. The center-to-center distance between the two recessed outer frames 10 located on the same side wall of the square duct / corridor / channel is L1 = 1100 mm, and the center-to-center distance between adjacent muffler modules is L1' = 2200 mm.

[0069] Through COMSO simulation, the curled frame 1 is constructed with a wall thickness e of 2 mm, a spiral number of 1.75 turns, a width t of 2 mm, a thickness a of 100 mm, and a material density of 1180 kg / m 3 The ultra-low frequency anechoic unit has a longitudinal wave velocity of 2720m / s and a shear wave velocity of 1460m / s. The simulated environmental parameters are an air density of 1.21kg / m3 , the sound speed is 343m / s, and the arrangement is carried out in a square pipe with a width of W1=200mm according to the above arrangement mode. By changing the number N of the silencer module groups, N=1 and N=2 respectively, the sound energy absorption rate of the ultra-low frequency silencer unit when the silencer module groups N are N=1 and N=2 respectively is simulated and measured. The relationship between the sound energy absorption rate and frequency when the ultra-low frequency silencer unit is used in the square pipe is obtained as shown in the figure below. Figure 12 As shown, it can be seen that when N=2, the pipe sound energy absorption rate reaches more than 0.9 at the resonance frequency, and the relative width is 17%, achieving broadband sound absorption performance in the ultra-low frequency range when the silencer unit is used in a square pipe.

[0070] Example 4

[0071] like Figure 9 and Figure 13-14 As shown, the ultra-low frequency silencer unit can also be used for silencer in square pipes / corridors / channels, and multiple silencer modules are arranged in sequence on the inner wall of the square pipe / corridor / channel. The silencer module includes three silencer unit groups respectively located at the three vertices of a right triangle, and two of them are located on the same side wall of the pipe / corridor / channel. The silencer unit group includes five recessed outer frames 10 arranged in sequence along the inner side of the pipe, and the ultra-low frequency silencer unit described in Example 1. The widths t of the curled channels 2 of the five ultra-low frequency silencer units are different. The ultra-low frequency silencer units are respectively located in an outer frame 10 and are surrounded on three sides. The channel openings of the two curled channels 2 of the ultra-low frequency silencer unit are one facing the outer frame 10 and the other facing the center of the pipe / corridor / channel.

[0072] The widths t of the curled channels 2 of the five ultra-low frequency silencer units arrayed in the ultra-low frequency silencer unit group are 1.5 mm, 2 mm, 2.5 mm, 3 mm, and 3.5 mm, respectively. The widths d2 of the gaps between the ultra-low frequency silencer unit and the outer frame 10 on three sides are all 5 mm. The distance l between adjacent ultra-low frequency silencer units in the ultra-low frequency silencer unit group is 130 mm. The distance L2 between two ultra-low frequency silencer units arranged on the same side wall of the pipe in the silencer module is 1100 mm, and the center distance L2' between adjacent silencer modules is 2200 mm.

[0073] Through COMSO simulation, the curled frame 1 is constructed with a wall thickness e of 2 mm, a spiral number of 1.75 turns, a width t of 2 mm, a thickness a of 100 mm, and a material density of 1180 kg / m 3 The ultra-low frequency anechoic unit has a longitudinal wave velocity of 2720m / s and a shear wave velocity of 1460m / s. The simulated environmental parameters are an air density of 1.21kg / m 3, sound speed 343m / s, according to the above arrangement, two groups of the silencer modules are arranged in a square pipe with a width of W2=200mm, and the sound energy absorption rate of the ultra-low frequency silencer unit when used in the square pipe is simulated and measured. The relationship between the sound energy absorption rate and frequency of the ultra-low frequency silencer unit when used in the square pipe is obtained as shown in the figure below: Figure 15 As shown, it can be seen that the sound energy absorption rate in the frequency range of 59-110Hz exceeds 0.5, its relative bandwidth reaches 60.4%, and its relative width meets the ultra-wideband requirement. In addition, the sound energy absorption rate in the frequency range of 63-105Hz exceeds 0.8, and the average sound energy absorption rate reaches 0.92. It can be seen that the ultra-low frequency silencer unit is applied to the square pipe and achieves high-efficiency sound energy absorption in the ultra-low frequency range.

[0074] The examples are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments. Any obvious improvements, substitutions or modifications that can be made by those skilled in the art without departing from the essence of the present invention are within the scope of protection of the present invention.

Claims

1. A frequency modulation ultra-thin, broadband, ultra-low frequency muffler unit, characterized by: The invention comprises two curled frames (1) nested in each other and centrally symmetrical, and two end faces fixed at the upper and lower ends of the curled frames (1); the curled frames (1) are formed by a square spiral; a rectangular air cavity (3) is formed at the center of the two curled frames (1); and two curled channels (2) are formed between the two curled frames (1); the curled channels (2) are spiral squares; the rectangular air cavity (3) is connected to the outside world through the curled channels (2); and the two end faces seal the curled channels (2) and the upper and lower ends of the rectangular air cavity (3); the thickness of the ultra-low frequency silencer unit is a, the wall thickness of the curled frame (1) is e, and the width of the curled channel (2) is t.

2. The frequency modulation ultra-thin, broadband, ultra-low frequency muffler unit according to claim 1, characterized in that: The thickness of the ultra-low frequency muffler unit is a=50e, the width t of the curled channel (2) is in the range of 0.75e≤t≤2.25e; and the number of spiral turns of the curled frame (1) is 1.75 turns.

3. The frequency modulation ultra-thin, broadband, ultra-low frequency muffler unit according to claim 1, characterized in that: The wall thickness e of the curled frame (1) is 2 mm.

4. The frequency modulation ultra-thin, broadband, ultra-low frequency muffler unit according to claim 1, characterized in that: The curled frame (1) and the two end surface materials are both made of organic glass or resin.

5. Use of the frequency modulated ultra-thin, broadband, ultra-low frequency muffler unit according to any one of claims 1 to 4, characterized in that: The invention is used for silencing ultra-low frequency sound waves, and the silencing frequency range is 60-115 Hz. The silencing frequency is adjusted by changing the ratio of the width t of the curled channel (2) and the wall thickness e of the curled frame (1).

6. The use of the frequency modulated ultra-thin, broadband, ultra-low frequency muffler unit according to claim 5, characterized in that: Used for silencing inside a building space or equipment, a plurality of ultra-low frequency silencing units with the same parameters are arranged in an array in front of the inner wall of the building space or equipment, and the channel openings of the two curled channels (2) of the ultra-low frequency silencing units are one facing the inner wall of the building space / equipment and the other facing away from the inner wall of the building space / equipment.

7. The use of the frequency modulated ultra-thin, broadband, ultra-low frequency muffler unit according to claim 6, characterized in that: The distance H1 between adjacent ultra-low frequency silencer units is 110 mm, and the distance d1 between the ultra-low frequency silencer unit and the inner wall of the building space / equipment is 5 mm.

8. The use of the frequency modulated ultra-thin, broadband, ultra-low frequency muffler unit according to claim 5, characterized in that: Used for silencing in a square duct / corridor / channel, a plurality of silencing modules are sequentially arranged in the square duct / corridor / channel, the silencing modules comprising three recessed outer frames (10) respectively located at three vertices of a right triangle, two of which are located on the same side wall of the square duct / corridor / channel, and three ultra-low frequency silencing units according to any one of claims 1 to 4 with the same parameters, the ultra-low frequency silencing units respectively located in an outer frame (10) and surrounded on three sides, the channel openings of the two curled channels (2) of the ultra-low frequency silencing units are one facing the outer frame (10) and one facing the center of the square duct / corridor / channel.

9. The use of the frequency modulated ultra-thin, broadband, ultra-low frequency muffler unit according to claim 5, characterized in that: Used for silencing in square pipes / corridors / channels, a plurality of silencing modules are arranged in sequence on the inner wall of the square pipe / corridor / channel, the silencing modules include three silencing unit groups respectively located at three vertices of a right triangle, and two of them are located on the same side wall of the square pipe / corridor / channel, the silencing unit group includes five recessed outer frames (10) arranged in sequence along the inner side of the pipe, and five ultra-low frequency silencing units according to any one of claims 1 to 4, the widths t of the curled channels (2) of the five ultra-low frequency silencing units are different, the ultra-low frequency silencing units are respectively located in an outer frame (10) and are surrounded on three sides, and the channel openings of the two curled channels (2) of the ultra-low frequency silencing units are one facing the outer frame (10) and one facing the center of the square pipe / corridor / channel.

10. The use of the frequency modulated ultra-thin, broadband, ultra-low frequency muffler unit according to claim 9, characterized in that: The gap width d2 between the three sides of the ultra-low frequency silencer unit and the outer frame (10) is 5 mm. The widths t of the curled channels (2) of the five ultra-low frequency silencer units arrayed in the ultra-low frequency silencer unit group are 1.5 mm, 2 mm, 2.5 mm, 3 mm, and 3.5 mm, respectively. The distance l between adjacent ultra-low frequency silencer units in the ultra-low frequency silencer unit group is 130 mm. The distance L2 between two ultra-low frequency silencer unit groups arranged on the same side wall of the square pipe / corridor / channel in the silencer module is 1100 mm. The center distance L2' between adjacent silencer modules is 2200 mm.

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