A-level metamaterial polyester sound absorption module for sound absorption and noise reduction in low and medium frequency environment

Abstract

The utility model discloses an A-level superstructure polyester sound absorption module for sound absorption and noise reduction in low and medium frequency environments, the module is formed by enclosing a panel, a bottom plate and four side plates, a sealed cavity is formed by enclosing the panel, the bottom plate and the four side plates, an aluminum honeycomb core for filling the cavity is arranged in the cavity, and the aluminum honeycomb core is arranged in the cavity. The inner wall of the face plate and the inner wall of the bottom plate are coated with adhesive layers used for fixing the aluminum honeycomb core, the face plate, the bottom plate and the four side plates are all polyester fiber plates, the surface density of the polyester fiber plates is 4.4-4.6 kg / m < 2 >, the weighting sound absorption coefficient alpha w is 1.00, and the noise reduction coefficient NRC is 1.00. The sound absorption performance of the A-level super-structure polyester sound absorption module can be greatly improved through a space sound absorption body jointly formed by the cavities, a large number of cavity units and the aluminum honeycomb core, the A-level super-structure polyester sound absorption module becomes a broadband efficient sound absorption body, the aluminum honeycomb core and the A-level polyester fiber board are combined together, and the good low-frequency sound absorption characteristic is achieved. The method is simple in process, low in production cost and small in environmental pollution, meets the requirements of sustainable development and has good economic and social values.

Description

Technical Field

[0001] The utility model relates to the technical field of sound-absorbing and noise-reducing materials, and in particular to a Class A super-structured polyester sound-absorbing module for sound absorption and noise reduction in medium and low frequency environments. Background Art

[0002] With the rapid development of China's economy and the continuous improvement of the quality of life, there are more and more high-rise buildings. At present, the motor room, elevator shaft, transformer room, pump room and air-conditioning room widely installed in various high-rise buildings will produce medium and low frequency noise during operation. The medium and low frequency noise exposure has a damaging effect on the human auditory system, nervous system, cardiovascular system, digestive system and metabolic function. According to the IEC581 standard of the International Electrotechnical Association and the GB / T14277-93 national standard of my country, the frequency band range is divided. Low frequency range: 30-150Hz is the low frequency band; medium frequency range: 150-500Hz is the medium and low frequency band, 500-5KHz is the medium and high frequency band; high frequency range: 5K-16KHz high frequency band. At present, the medium and low frequency noise generated by equipment such as elevator shafts, elevator rooms, and air-conditioning rooms has become a major problem affecting people's quality of life and physical health, so how to effectively control the medium and low frequency noise in buildings has become the most concerned topic at present.

[0003] At present, there are many types of sound-absorbing and noise-reducing materials used in specific environments such as elevator shafts, elevator machine rooms, and air-conditioning machine rooms. They mainly include fibrous materials, called porous sound-absorbing materials, such as glass wool, rock wool, mineral slag wool, cotton and linen, and artificial fiber wool, special metal fiber wool, etc., and also include foam plastics with interconnected gaps. The main building sound-absorbing panels are mineral wool sound-absorbing panels, sound-absorbing felts, foam plastics, sound-absorbing glass fibers, etc. According to the different sound absorption mechanisms, sound-absorbing materials can be divided into two categories: resonant sound-absorbing structural materials and porous sound-absorbing materials. There are many microscopic pores in the porous sound-absorbing material that go straight through the surface of the material or there are many interconnected bubbles inside it. Due to the viscosity and thermal conduction effects, the sound energy can be converted into heat energy and dissipated. Porous sound-absorbing materials have good sound absorption performance in the medium and high frequencies, but the sound absorption performance in the medium and low frequencies is generally poor. The current patent technologies in the field of building sound absorption and noise reduction are as follows:

[0004] CN 209780138 U discloses a sound-insulating and sound-absorbing wall structure for an elevator shaft, comprising a shaft, a sound-insulating component, a Z-shaped keel, screws, a rubber vibration-isolating pad, a plastic expansion screw, and a sound-absorbing cotton layer; a sound-insulating component is arranged outside the shaft, and a Z-shaped keel is arranged between the sound-insulating component and the shaft; the sound-insulating component is fixedly connected to the Z-shaped keel by screws; a rubber vibration-isolating pad is arranged between the Z-shaped keel and the shaft; the rubber vibration-isolating pad and the Z-shaped keel are fixed to the shaft by plastic expansion screws; a sound-absorbing cotton layer is filled between adjacent Z-shaped keels; the sound-insulating component is composed of a sound-insulating board and a fireproof board from the inside to the outside;

[0005] CN 218622719 U discloses a sound insulation structure for an air conditioner room, comprising a mounting plate and a sound insulation unit, wherein: the mounting plate: the rear wall surface of the notches symmetrically arranged at the four corners of the front surface of the mounting plate is provided with mounting holes; the sound insulation unit: comprises an asbestos board, sound insulation foam and sound insulation felt board, the asbestos board, sound insulation foam and sound insulation felt board are arranged in the inner cavity of the mounting plate from back to front in sequence, the front surface of the asbestos board is fixedly connected to the rear surface of the sound insulation foam, and the front surface of the sound insulation foam is fixedly connected to the rear surface of the sound insulation felt board; wherein: the front surface of the mounting plate is provided with a glass fiber board; wherein: the front surface of the glass fiber board is provided with evenly distributed sound absorption cavities; wherein: the front surface of the glass fiber board is provided with evenly distributed high-density sound insulation boards.

[0006] CN 212129524 U discloses a sound insulation and noise reduction device for an air-conditioning room, belonging to the field of noise treatment. The device comprises a frame body, a slot is provided on the top of the frame body, a card slot is provided on the inner wall of the slot, a tenon block is provided on one side of the frame body, a tenon groove is provided on the other side of the frame body, and an insert block is fixed on the bottom of the frame body. When the device is installed vertically, a worker inserts the insert block into the slot, and the card block begins to shrink after being squeezed. When the insert block is inserted to the bottom of the slot, the card block is inserted into the card groove under the restoring capacity of a spring. When the device is installed horizontally, the worker aligns the tenon block with the tenon groove and then moves downward so that the tenon block can be inserted into the tenon groove. When the entire machine room wall is installed, the four sides of each device group can be limited and fixed.

[0007] It is not difficult to find from the above patents that the current noise reduction for medium and low frequency noise generated by elevator shafts, air conditioning rooms, etc. has developed from a single sound absorption noise reduction to a comprehensive use of multiple technical means such as sound absorption, sound insulation, and vibration reduction to achieve comprehensive control of noise pollution, but there are still some problems. Since the characteristics of medium and low frequency noise are long sound waves, strong diffraction ability, strong transmission ability, and difficulty in sound absorption, it is a thorny problem in noise control. The internal sound energy density of machine rooms, elevator shafts, etc. is too large, which aggravates the pollution of transmitted noise. When the sound insulation component is radiated by low frequency noise, the sound insulation component will vibrate. The vibration of the sound insulation component is related to the sound pressure level intensity of the low frequency noise and the mass density of the sound insulation component. When the sound pressure intensity of the low frequency noise is sufficient to overcome the mass and density of the sound insulation component, the sound insulation component will vibrate with the vibration frequency of the low frequency noise. Patent technologies such as the above cannot solve the problem of vibration of the sound insulation component caused by medium and low frequency noise. The noise can still be transmitted through the sound insulation component, and the vibration energy generated by the medium and low frequency noise cannot be effectively consumed. It can be seen that the current means of reducing medium and low frequency noise are not ideal. In order to overcome the problem of sound wavelength when absorbing lower frequency sound waves, the structure needs to have a cavity depth of more than 20cm, which is obviously not realistic in actual application. Therefore, how to take into account the comprehensive means of sound absorption, sound insulation and vibration reduction to achieve effective control of medium and low frequency noise, meet industrial application and reduce costs has become the focus and difficulty of noise control, and has important significance for the research and control of environmental noise. Utility Model Content

[0008] In view of the shortcomings of the prior art, the technical problem to be solved by the utility model is to provide a Class A super-structured polyester sound-absorbing module for sound absorption and noise reduction in medium and low frequency environments, which has obvious sound absorption effect on noise in medium and low frequency bands and has a simple structure, reasonable design and low cost.

[0009] In order to solve the above technical problems, the technical solution adopted by the utility model is: a Class A super-structured polyester sound-absorbing module for sound absorption and noise reduction in medium and low frequency environments, the module is formed by a panel, a bottom plate and four side plates, the panel, the bottom plate and the four side plates are surrounded to form a sealed cavity, an aluminum honeycomb core for filling the cavity is arranged in the cavity, the inner walls of the panel and the bottom plate are coated with an adhesive layer for fixing the aluminum honeycomb core, the panel, the bottom plate and the four side plates are all polyester fiber boards, and the surface density of the polyester fiber boards is 4.4-4.6kg / m 2 , weighted sound absorption coefficient αw = 1.00, noise reduction coefficient NRC = 1.00.

[0010] The above-mentioned Class A super-structured polyester sound-absorbing module for sound absorption and noise reduction in medium and low frequency environments, the surface density of the polyester fiberboard is 4.5kg / m 2 .

[0011] The above-mentioned Class A super-structured polyester sound-absorbing module for sound absorption and noise reduction in medium and low frequency environments has a polyester fiber board with a thickness of 11 mm and a module thickness of 50 mm.

[0012] The above-mentioned Class A super-structured polyester sound-absorbing module for sound absorption and noise reduction in medium and low frequency environments, the four side panels are integrally formed with the four edges of the bottom plate, and the panel is integrally formed with any one of the four side panels.

[0013] The above-mentioned Class A super-structured polyester sound absorption module for sound absorption and noise reduction in medium and low frequency environments, the connection between adjacent side panels is bonded and fixed, and the connection between the panel and the side panel symmetrically arranged on one side of the bottom plate is bonded and fixed.

[0014] The advantages of the A-class super-structured polyester sound-absorbing module used for sound absorption and noise reduction in medium and low frequency environments of the utility model are: compared with the traditional method of first controlling the radiation energy of low-frequency noise to the sound insulation component through auxiliary measures of sound insulation, it can be achieved without a thicker structure, which is more in line with the actual application needs. The spatial sound absorber composed of the cavity, a large number of cavity units and the aluminum honeycomb core can greatly improve the sound absorption performance of the A-class super-structured polyester sound absorption module, and become a high-efficiency sound absorber with a wide frequency band. The aluminum honeycomb core is combined with the A-class polyester fiberboard, which has good low-frequency sound absorption characteristics. Compared with traditional high-density sound-absorbing materials, it has the characteristics of light weight, softness and easy preparation; compared with porous noise reduction materials such as fibers and foams, it can effectively improve the medium and low frequency sound absorption performance. The method is simple and easy to operate, with a short production cycle, convenient for large-scale production and application, low production cost, low environmental pollution, in line with the requirements of sustainable development, and has good economic and social value. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of the overall structure of Embodiment 1 of the present utility model;

[0016] Figure 2 This is a schematic diagram of the internal structure of Embodiment 1 of the present utility model;

[0017] Figure 3 This is a full cross-sectional view of Example 1 of the utility model;

[0018] Figure 4 This is a diagram of the expanded structure of each plate in Example 1 of the utility model;

[0019] Figure 5 This is a diagram of the expanded structure of each plate of Example 2 of the utility model;

[0020] Figure 6 This is a schematic diagram of the installation structure for testing the sound absorption performance of Class A super-structured polyester sound absorption modules;

[0021] Figure 7The frequency characteristic curve of the sound absorption coefficient of the Class A super-structured polyester sound absorption module of the utility model;

[0022] Figure 8 The noise reduction coefficient frequency characteristic curve of the A-class super-structured polyester sound absorption module of the utility model is shown in FIG. DETAILED DESCRIPTION

[0023] The utility model is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0024] In the present invention, unless otherwise stated, the directional words used, such as "upper" and "lower", generally refer to the upper and lower parts of the device in actual use or working state, specifically the drawing direction in the accompanying drawings; while "inner" and "outer" refer to the outline of the device. In addition, in the description of this application, the term "including" means "including but not limited to". The terms first, second, third, etc. are used only as labels and do not impose numerical requirements or establish an order. The term "plurality" means "two or more".

[0025] Embodiment 1:

[0026] like Figure 1 , 2 As shown in , 3, a Class A super-structured polyester sound-absorbing module for sound absorption and noise reduction in medium and low frequency environments is formed by a panel 1, a bottom plate 2 and four side plates 3. A sealed cavity 4 is formed between the panel 1, the bottom plate 2 and the four side plates 3. An aluminum honeycomb core 5 is arranged in the cavity 4 to fill the cavity 4. An adhesive layer 6 for fixing the aluminum honeycomb core 5 is coated on the inner walls of the panel 1 and the bottom plate 2. The panel 1, the bottom plate 2 and the four side plates 3 are all polyester fiber boards. The joints 7 of adjacent side plates 3 are bonded and fixed to each other, and the panel 1 is bonded and fixed to the joints of the side plates 3 symmetrically arranged on one side of the bottom plate 2.

[0027] Of course, according to the different strength requirements of the sound absorption module and the purpose of absorbing different sound wave frequency bands, the adhesive layer can also be applied only on one side of the inner wall of the panel or the inner wall of the bottom plate 2. In the double-sided coating method, the aluminum honeycomb core 5 is fixed by double-sided fixing. The elasticity of the aluminum honeycomb core 5 in the single-sided fixing method is relatively good, which is used to absorb medium and high frequency sound waves. The double-sided fixing method reduces the overall elasticity of the aluminum honeycomb core 5, and the resistance to external forces during vibration is also greater, and the vibration frequency is lower, which is better for absorbing medium and low frequency sound waves. In the actual application process, for the treatment of low-frequency noise, a structure with a larger thickness of aluminum sheets of the aluminum honeycomb core itself can be selected. The resistance to external forces during vibration is also greater, the vibration frequency is lower, and it is easier to absorb the sound waves generated by low-frequency noise.

[0028] like Figure 4As shown, in order to enhance the overall strength of the Class A super-structured polyester sound-absorbing module, reduce production costs, and improve production efficiency, the four side panels 3 are integrally formed with the four sides of the bottom panel 2, and the panel 1 is integrally formed with one of the long side panels of the four side panels 3. Figure 4 As shown by the dotted lines, during production, the panel 1 and the side panel 3 and the other three side panels 3 and the bottom panel 2 can be folded upward along the dotted lines according to the size requirements, and then fixed with adhesive. The aluminum honeycomb core 5 is cut according to the size of the cavity 4 and filled into the cavity 4. Finally, the adhesive layer 6 is applied to the inside of the panel 1, and the panel 1 is compacted and bonded to the aluminum honeycomb core 5 and the top of each side panel 3. In the embodiment of the utility model, the thickness of the polyester fiber board is 11mm, and the module thickness is 50mm. The surface density of the polyester fiber board is 4.4-4.6kg / m 2 , weighted sound absorption coefficient αw = 1.00, noise reduction coefficient NRC = 1.00. The surface density of the polyester fiberboard of the utility model is preferably 4.5 kg / m 2 The polyester fiberboard of the utility model is a grade A polyester fiberboard.

[0029] Sound absorption principle:

[0030] In the utility model, the filling of the aluminum honeycomb core 5 makes the cavity 4 form a large number of cavity units. After the adhesive layer is coated on one side, each cavity unit can be regarded as consisting of a cavity and an opening. Each cavity unit can be regarded as a Helmholtz resonator, whose cavity is the cavity unit and whose opening is the small hole surrounded by hexagons. In this way, the entire aluminum honeycomb core 5 constitutes an acoustic super structure. When air enters or goes out through the opening, a pressure change will occur inside the cavity, causing the air to vibrate. If the frequency of the incident sound wave matches the vibration frequency inside the cavity, then resonance will occur, that is, the vibration amplitude inside the cavity increases and consumes the energy of the incident sound wave. In this way, the absorption of sound waves of a specific frequency is achieved.

[0031] When the sound wave is incident on the surface layer 1, the sound wave energy can enter the material along the fine pores on the surface of the A-grade polyester fiberboard, causing the vibration of the air molecules in the pores. Due to the viscous resistance of the air and the friction between the air molecules and the pore walls, the sound energy is converted into heat energy and lost, thereby achieving the purpose of thin plate resonance sound absorption. After a part of the mid-high frequency noise sound waves are absorbed by the surface layer 1, part of the mid-high frequency noise sound waves and low frequency noise sound waves will enter the cavity 4 at the rear of the material. Since the A-grade super-structured polyester sound absorption module has a cavity structure inside, the filling of the aluminum honeycomb core 5 makes the cavity 4 form a large number of cavity units. After the low-frequency noise sound waves enter the cavity unit, they are repeatedly reciprocated and consumed in the cavity. At the same time, the radiation of low-frequency noise causes the vibration of the aluminum honeycomb core 5 by utilizing the thin and elastic metal sheet structure characteristics of the aluminum honeycomb core 5. The low-frequency sound wave energy is further consumed through the vibration of the metal sheet and the reciprocating oscillation of the sound waves in the cavity unit, which greatly weakens the radiation energy of the low-frequency noise, thereby achieving the purpose of effectively controlling the mid-low frequency noise.

[0032] The thickness of the aluminum honeycomb core 5 in the utility model is about 24mm. According to the principle that the length or size of an object can affect the frequency of vibration, the vibration frequency of an object with a longer length is lower, and the vibration frequency of an object with a shorter length is higher. In addition, after the adhesive layer is coated on both sides, the aluminum honeycomb core 5 actually forms an elastic damping structure layer after being fixed, which can absorb medium and low frequency sound waves well and suppress the vibration of the sound absorption module to achieve the effect of sound insulation. Since the aluminum honeycomb core 5 is composed of a large number of honeycomb structures connected to each other, and the honeycomb structure is an aluminum sheet, coupling will occur between two adjacent cavity units, resulting in the emergence of two resonant frequencies, and finally forming a resonance of the overall aluminum honeycomb core, thus increasing the number and width of the absorption band. After solidification, the coated adhesive layer 6 can not only prevent the interference of reflected waves, but also provide a rigid support for the sound absorption module, which can further enhance the absorption effect. By changing the aperture size of the aluminum honeycomb holes, the position and intensity of the resonance frequency can be adjusted. For example, the aluminum honeycomb core 5 is compressed laterally and placed in the cavity 4. Through different degrees of compression, different sound insulation effects can be designed according to the actual needs of sound absorption and noise reduction.

[0033] During installation, according to the actual installation area, the elevator shaft noise reduction board can be directly spliced ​​and fixed with special staples when used inside the elevator shaft. The installation is simple and the construction efficiency is very high. The material can also be made into wall panels and installed in the elevator shaft. At the same time, this product can also be combined with other wall materials to form a soundproof wall or soundproof ceiling. The main purpose is mainly suitable for sound absorption and noise reduction treatment in various specific structures such as elevator shafts, elevator machine rooms, and air-conditioning machine rooms. It can absorb a large amount of sound energy in the space and reduce indoor noise. It is also non-toxic and harmless, and is a truly green sound-absorbing decorative board.

[0034] Embodiment 2:

[0035] The same parts of this embodiment as those of embodiment 1 are not described in detail. The difference between the present embodiment and embodiment 1 is that Figure 5 As shown, the four side panels 3 are integrally formed with the four sides of the bottom panel 2 , and the panel 1 is integrally formed with a side panel of one of the short sides of the four side panels 3 .

[0036] The test results of the sound absorption and noise reduction performance of the A-class super-structured polyester sound absorption module of the utility model are as follows:

[0037] like Figure 6 As shown, the utility model adopts the reverberation chamber method to measure the sound absorption coefficient of the A-class super-structured polyester sound absorption module. The sample size of the A-class super-structured polyester sound absorption module material is 1800mm×600mm×50mm. The thickness of the panel 1, the bottom plate 2 and the four side plates 3 is 11mm. The aluminum honeycomb core 5 is filled inside, and the surface density is 4.5kg / m 2 . Size and installation method: Install the Class A super-structured polyester sound absorption module 8 in the reverberation room, with an area of ​​4.2m×2.4m, a total of 10.08㎡, surrounded by a 40mm thick reinforced concrete slab, and the distance between the original wall 9 and the Class A super-structured polyester sound absorption module 8 is 350mm. The detection instrument uses the RTA840 system, and the specific test results of its sound absorption coefficient and noise reduction coefficient are shown in Table 1 and Table 2:

[0038] Table 1:

[0039] Frequency / Hz 100 125 160 200 250 315 400 500 630 800 Sound absorption coefficient αs 0.70 0.89 0.66 0.99 0.98 1.00 0.98 0.94 0.99 1.00

[0040] Frequency / Hz 1000 1250 1600 2000 2500 3150 4000 5000 Average sound absorption coefficient Sound absorption coefficient αs 0.99 0.97 1.00 0.99 0.96 0.96 0.98 1.00 0.94

[0041] From the above table and reference Figure 7 It can be concluded that the average sound absorption coefficient of the Class A superstructured polyester sound absorption module of the utility model between 100-5000 Hz is 0.94.

[0042] Table 2:

[0043]

[0044] From the above table and reference Figure 8 It can be concluded that the noise reduction coefficient NRC of the Class A super-structured polyester sound-absorbing module of the utility model at 250Hz, 500Hz, 1000Hz, and 2000Hz is 1.00.

[0045] It can be seen from Table 1 and Table 2 that the A-class super-structured polyester sound-absorbing module of the utility model exhibits excellent full-frequency sound absorption performance, and has good sound absorption and noise reduction performance in the medium and low frequency bands. Test conclusion: The weighted sound absorption coefficient αw=1.00 and the noise reduction coefficient NRC=1.00 of the sample tested. According to GB / T16731-2023 "Sound absorption performance classification of building sound absorption products", the sound absorption performance level of its sound absorption structure is divided into Class A and Class I.

[0046] Compared with the traditional method of first controlling the radiation energy of low-frequency noise to the sound insulation component through auxiliary measures of sound insulation, the utility model can be realized without a thicker structure, which is more in line with the actual application requirements. For the vibration of the component caused by the radiation of low-frequency noise, a combination of elastic damping and cavity units is adopted. While the aluminum honeycomb core 5 vibrates, the oscillation consumption of the cavity unit is assisted, which not only reduces the vibration intensity of the aluminum honeycomb core 5, but also weakens the radiation energy of the low-frequency noise. The spatial sound absorber composed of the cavity 4, a large number of cavity units and the aluminum honeycomb core 5 can greatly improve the sound absorption performance of the A-class super-structured polyester sound absorption module, becoming a broadband high-efficiency sound absorber. The aluminum honeycomb core 5 is combined with the A-class polyester fiberboard, which has good low-frequency sound absorption characteristics.

[0047] The utility model A-class super-structured polyester sound-absorbing module combines the advantages of sound-absorbing materials, vibration isolation materials and air dampers. In addition to high sound absorption coefficient, wide sound absorption frequency and excellent acoustic performance, it also has good physical and mechanical properties and indoor decorative performance. It can be widely used in various specific structures such as elevator shafts, elevator machine rooms, air-conditioning machine rooms, etc. for sound absorption and noise reduction. It is non-toxic and harmless, and is a truly green sound-absorbing decorative board.

[0048] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Any changes, modifications, additions or substitutions made by ordinary technicians in this technical field within the essential scope of the present invention should fall within the protection scope of the present invention.

Claims

1. A Class A super-structured polyester sound absorption module for sound absorption and noise reduction in medium and low frequency environments, characterized in that: The module is formed by a panel, a bottom plate and four side plates. A sealed cavity is formed between the panel, the bottom plate and the four side plates. An aluminum honeycomb core is arranged in the cavity to fill the cavity. The inner walls of the panel and the bottom plate are coated with an adhesive layer for fixing the aluminum honeycomb core. The panel, the bottom plate and the four side plates are all polyester fiberboards. The surface density of the polyester fiberboard is 4.4-4.6kg / m 2 , weighted sound absorption coefficient αw = 1.00, noise reduction coefficient NRC = 1.

00.

2. The Class A super-structured polyester sound absorbing module for sound absorption and noise reduction in medium and low frequency environments according to claim 1 is characterized by: The surface density of the polyester fiberboard is 4.5 kg / m 2 .

3. The Class A super-structured polyester sound absorbing module for sound absorption and noise reduction in medium and low frequency environments according to claim 1 is characterized by: The thickness of the polyester fiberboard is 11 mm, and the thickness of the module is 50 mm.

4. The Class A super-structured polyester sound absorbing module for sound absorption and noise reduction in medium and low frequency environments according to claim 1 is characterized by: The four side panels are all integrally formed with the four edges of the bottom panel, and the panel is integrally formed with any one of the four side panels.

5. The Class A super-structured polyester sound absorbing module for sound absorption and noise reduction in medium and low frequency environments according to claim 4 is characterized in that: The connection between the adjacent side panels is bonded and fixed, and the connection between the panel and the side panel symmetrically arranged on one side of the bottom panel is bonded and fixed.

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