Thin-layer sound absorption superstructure composite acoustic shield and use method

Abstract

According to the thin-layer sound absorption superstructure composite acoustic enclosure and the using method, the acoustic enclosure is composed of the cover plate, the conformal frame, the thin-layer sound absorption superstructures and the porous sound absorption materials, the variety of the thin-layer sound absorption superstructures is not limited to one, and the broadband noise reduction effect can be achieved through the parallel superposition design of the thin-layer sound absorption superstructures and the porous sound absorption materials. Wherein the thin-layer sound absorption superstructure can absorb noise in different frequency ranges of medium and low frequency bands, the porous sound absorption material can absorb noise in medium and high frequency bands, and the working bandwidth of the composite acoustic shield after parallel connection and superposition can cover the low, medium and high wide frequency bands. The thin-layer sound absorption superstructure composite acoustic shield further has the advantages of being high in space utilization rate, high in space adaptability, small in thickness, low in surface density and high in material replaceability. Compared with an existing sound insulation cover, on the premise that the thickness is small and the surface density is low, the working frequency band is wider, the sound insulation effect is better, and the sound insulation cover has wide application prospects in noise control of various mechanical and electrical products.

Description

Technical Field

[0001] The invention belongs to the field of sound insulation and noise reduction, and specifically relates to a thin-layer sound-absorbing superstructure composite sound insulation cover and a use method thereof. Background Art

[0002] For smaller noise sources, the most effective method is to use acoustic packages that fit the equipment products to shield the noise and eliminate the interference of the noise source to the outside world. In many application scenarios, this acoustic package often appears in the form of a soundproof cover, which is generally made of sound-insulating materials with strong sound reflection. However, since conventional soundproof covers generally do not have the ability to lose sound energy, they only reflect the sound waves back and trap them in the internal space. Therefore, once there is a small gap, they will fail due to sound leakage. In addition, if low-frequency noise is to be isolated, the soundproof cover needs to have a high surface density, which is unacceptable for applications with strict restrictions on lightweight and size space. In addition, in some application scenarios, there is also a necessary need for ventilation and heat dissipation. The reflective soundproof cover cannot achieve the expected noise reduction effect due to the problem of sound wave diffraction. Filling the internal space with porous sound-absorbing materials can effectively alleviate the impact of sound leakage, but due to the limitation of space size, filling a thin layer of porous sound-absorbing materials cannot absorb low-frequency noise. Therefore, the current problem is that the reflective soundproof cover cannot resist sound leakage, and filling a thin layer of porous sound-absorbing materials cannot isolate low-frequency noise.

[0003] The development of acoustic superstructures provides a better solution for designing low-frequency sound-absorbing structures with subwavelength thickness. The basic structural forms of commonly used sound-absorbing superstructures include Helmholtz resonant cavity, film / plate structure, Fabry-Perot cavity, slit absorber, and the combination or derivative structure of these basic structural forms. Acoustic superstructures have become one of the main development directions in the field of noise control in the future due to their advantages of thin thickness and light weight. Using acoustic superstructures to design soundproof enclosures for mechanical equipment such as compressors is a better means of noise control. However, on the one hand, the main research object of acoustic superstructures at present is flat-plate structures. Researchers are committed to expanding small-sized structures to large-sized engineering applications, while soundproof enclosures generally consider factors such as space utilization and are mostly curved structures; on the other hand, the basic structural forms of acoustic superstructures still have some shortcomings, such as the Helmholtz resonant cavity structure is thicker in low-frequency design, and the film structure is prone to aging, easy to fall off, and poor durability. These shortcomings greatly limit the development and application of acoustic superstructures in the field of soundproof enclosures. Therefore, it is necessary to develop new sound insulation enclosure design methods to achieve low-frequency broadband noise reduction effects through thinner thickness and lower surface density. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of existing sound insulation covers and provide a thin-layer sound-absorbing superstructure composite sound insulation cover and a use method thereof, which is used to achieve better noise attenuation effect in a broadband range by using a thinner thickness and a lower surface density.

[0005] In order to achieve the above object, the present invention adopts the following technical solution: A thin-layer sound-absorbing superstructure composite sound insulation cover comprises a cover plate, a conformal frame, a thin-layer sound-absorbing superstructure and a porous sound-absorbing material. The thin-layer sound-absorbing superstructure and the porous sound-absorbing material are stacked in parallel and inlaid on the conformal frame to achieve a broadband noise reduction effect. The cover plate is arranged on the top of the conformal frame.

[0006] A further improvement of the present invention is that the cover plate is a labyrinth-type channel structure, which can be filled with porous sound-absorbing materials, and the structure is designed with openings according to the use requirements of the equipment.

[0007] A further improvement of the present invention is that the thin layer sound absorbing superstructure and the porous sound absorbing material are combined and spliced ​​by a conformal frame, and the shape and size of the conformal frame are designed according to the target noise source or the size of the equipment.

[0008] A further improvement of the present invention is that the structural area, number of openings, opening radius, opening thickness, number of cavities, cavity length and cavity depth of the thin-layer sound absorbing superstructure can be flexibly designed to meet the noise attenuation effect of different working frequency bands.

[0009] A further improvement of the present invention is that each thin layer of sound absorbing superstructure can absorb noise in different frequency ranges of medium and low frequency bands, the porous sound absorbing material can absorb noise in medium and high frequency bands, and the composite sound insulation cover after parallel superposition can achieve noise reduction effects covering low, medium and high wide frequency bands.

[0010] A further improvement of the present invention is that thin-layer sound-absorbing superstructures with adjacent working frequency bands in parallel can achieve superposition and widening of the working frequency bands, and the working frequency band of the combined structure is the superposition of the working frequency bands of each thin-layer sound-absorbing superstructure. By combining thin-layer sound-absorbing superstructures with multiple different working frequency bands, a broadband sound absorption and noise reduction effect can be achieved.

[0011] A further improvement of the present invention is that the thin-layer sound-absorbing superstructure comprises a perforated plate, a labyrinth-shaped channel and a homogenous plate which are arranged in sequence from top to bottom.

[0012] A further improvement of the present invention is that the thickness of the thin layer sound absorbing superstructure for absorbing noise in the medium and low frequency bands is 1 / 25 to 1 / 57 of the wavelength of the sound wave.

[0013] A further improvement of the present invention is that the thickness of the porous sound absorbing material used to absorb mid- and high-frequency noise is similar to the thickness of the thin-layer sound absorbing superstructure, so that the entire composite sound insulation cover has the advantages of thin thickness and low surface density, and is suitable for compact and lightweight working environments.

[0014] A method for using a thin-layer sound-absorbing superstructure composite soundproof enclosure, comprising: 1) Determine the shape and size of the cover and conformal frame based on the target noise source or equipment size; 2) According to the bandwidth of the required noise reduction frequency band, the frequency band is divided into multiple sub-bands. For medium and low frequency noise, the structural area, number of openings, opening radius, opening thickness, number of cavities, cavity length, and cavity depth of the thin-layer sound absorbing superstructure are adjusted so that the sound absorption bandwidth of each thin-layer sound absorbing superstructure corresponds to each sub-band; for medium and high frequency noise, a porous sound absorbing material with a thickness similar to that of the thin-layer sound absorbing superstructure is selected; 3) The thin-layer sound-absorbing superstructure and the porous sound-absorbing material are stacked in parallel and embedded in the conformal frame, and the effect of "absorbing instead of isolating" noise is achieved by absorbing sound energy, thereby achieving broadband noise reduction.

[0015] Compared with the prior art, the present invention has at least the following beneficial technical effects: 1. Through the parallel superposition design of thin-layer sound-absorbing superstructure and porous sound-absorbing material, the composite soundproof cover can achieve noise reduction effects covering low, medium and high wide frequency bands; 2. The structure and size of the cover plate and conformal frame can be flexibly designed according to the use requirements, with good applicability; 3. By adjusting the structural parameters of the thin-layer sound-absorbing superstructure, the noise attenuation effect for different working frequency bands can be achieved; 4. Connecting thin-layer sound-absorbing superstructures of adjacent working frequency bands in parallel can realize the superposition and widening of working frequency bands. By combining thin-layer sound-absorbing superstructures of multiple working frequency bands, a broadband sound absorption and noise reduction effect can be achieved. 5. The introduction of porous sound-absorbing materials can greatly improve the noise attenuation effect of the composite sound insulation cover in the medium and high frequency bands; 6. Compared with traditional leather and other reflective sound insulation covers, composite sound insulation covers can achieve the effect of "absorbing instead of isolating" noise by absorbing sound energy, thereby resisting sound leakage and achieving a higher average insertion loss through a smaller increase in surface density; 7. Since the composite sound insulation cover has strong sound absorption ability and can effectively dissipate sound energy, it is not necessary to completely wrap the target noise source or equipment, and can also achieve considerable sound insulation and noise reduction effects. It is suitable for work places that require ventilation and heat dissipation; 8. The composite sound insulation cover not only has good sound insulation effect, but also has the advantages of high space utilization, strong space adaptability, thin thickness, low surface density and strong material replaceability. It has broad application prospects in the noise control of various electromechanical products.

[0016] In summary, according to the above characteristics of a thin-layer sound-absorbing superstructure composite soundproof cover provided by the present invention, the composite soundproof cover provided by the present invention can achieve a good noise attenuation effect in a wide frequency range. Among them, the thin-layer sound-absorbing superstructure can absorb medium and low frequency noise, and the porous sound-absorbing material can absorb medium and high frequency noise, so that the working frequency band of the entire soundproof cover can cover low, medium and high wide frequency bands. In this soundproof cover, the structure and size of the cover plate and the conformal frame can be flexibly designed according to the use requirements, and have good applicability. Compared with traditional leather and other soundproof covers that are mainly reflective, the composite soundproof cover can achieve the effect of "absorbing instead of isolating" noise by absorbing sound energy, thereby resisting sound leakage and achieving a higher average insertion loss improvement through a small increase in surface density. Due to its strong sound absorption ability, it can effectively lose sound energy, so that it is not necessary to completely wrap the target noise source or equipment, and can also obtain a considerable sound insulation and noise reduction effect. In addition, the present invention also has the advantages of high space utilization, strong space adaptability, thin thickness, low surface density and strong material replaceability. In summary, compared with the existing sound insulation covers, this composite sound insulation cover has a wider working frequency band and better sound insulation effect while ensuring thin thickness and low surface density. It has broad application prospects in noise control of various electromechanical products. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the composition of a thin-layer sound-absorbing superstructure composite soundproof cover; Figure 2 Schematic diagram of the composition of the thin layer sound absorbing superstructure; Figure 3 a is the schematic diagram of the structure of the six designed thin-layer sound-absorbing superstructures; Figure 3 b is the sound absorption coefficient curve of the thin-layer sound-absorbing superstructure with working frequency bands of 250 ~ 500 Hz, 600 ~ 1300 Hz, and 900 ~ 2000 Hz respectively; Figure 3 c is the sound absorption coefficient curve of the thin-layer sound-absorbing superstructure with working frequency bands of 1300 ~ 2500 Hz, 1700 ~ 3100 Hz, and 2000 ~ 3600 Hz respectively; Figure 4 a is the research results of parallel coupling of thin-layer sound-absorbing superstructures with working frequency bands of 250 ~ 500 Hz and 600 ~ 1300 Hz respectively; Figure 4b is the research results of parallel coupling of thin-layer sound-absorbing superstructures with working frequency bands of 600 ~ 1300 Hz and 1300 ~ 2500 Hz respectively; Figure 4 c is the research results of parallel coupling of thin-layer sound-absorbing superstructures with working frequency bands of 900 ~ 2000 Hz and 1700 ~ 3100 Hz respectively; Figure 4 d is the research result of parallel coupling of thin-layer sound-absorbing superstructures with working frequency bands of 900 ~ 2000 Hz and 2000 ~ 3600 Hz respectively; Figure 5 a is the test result of the sound absorption coefficient of porous sound absorbing material; Figure 5 b is the sound insulation test result of a large-sized flat-plate thin-layer sound-absorbing superstructure composite sample; Figure 6 a is a simplified model diagram of the compressor; Figure 6 b is the polygon fitting idea of ​​the composite sound insulation cover; Figure 6 c is a schematic diagram of the overall structure of the composite sound insulation cover; Figure 6 d is a schematic diagram of the structure of the composite sound insulation cover I; Figure 7 a is a photo of the composite sound insulation cover I sample; Figure 7 b is a photo of the experimental equipment and measurement point layout; Figure 7 c is the sound pressure level curve of composite sound insulation cover I; Figure 7 d is the insertion loss curve of composite sound insulation cover I; Figure 8 a is a schematic diagram of the structure of composite sound insulation cover II and composite sound insulation cover III; Figure 8 b is the photo of the sample of composite sound insulation cover II and composite sound insulation cover III; Figure 8 c is the sound pressure level curve of composite sound insulation cover II and composite sound insulation cover III; Figure 8 d is the insertion loss curve of composite sound insulation cover II and composite sound insulation cover III. DETAILED DESCRIPTION

[0018] The technical scheme in the implementation case of the present invention is described below in conjunction with the relevant calculation and measurement results of the implementation case of the present invention in the accompanying drawings. Obviously, the implementation case described is only a part of the implementation case of the present invention, not all the implementation cases. Based on the implementation case in the present invention, all other implementation cases obtained by those skilled in the art without making creative work belong to the scope of protection of the present invention.

[0019] Example 1 like Figure 1 As shown, a thin-layer sound-absorbing superstructure composite sound insulation cover provided by the present invention is composed of a cover plate 1, a conformal frame 2, a thin-layer sound-absorbing superstructure 3 and a porous sound-absorbing material 4. The type of the thin-layer sound-absorbing superstructure 3 is not limited to one type. A broadband noise reduction effect can be achieved through the parallel superposition design of the thin-layer sound-absorbing superstructure 3 and the porous sound-absorbing material 4.

[0020] In this embodiment, the cover plate 1 is a labyrinth-shaped channel structure that can be filled with porous sound-absorbing materials, and its structure is designed with openings according to the use requirements of the equipment.

[0021] In this embodiment, the thin layer sound absorbing superstructure 3 and the porous sound absorbing material 4 are combined and spliced ​​by a conformal frame 2. The shape and size of the conformal frame 2 are designed according to the target noise source or equipment size, so that the composite sound insulation enclosure has a higher space utilization rate and a stronger space adaptability.

[0022] In this embodiment, each thin layer of sound absorbing superstructure 3 can absorb noise in different frequency ranges of medium and low frequency bands, the porous sound absorbing material 4 can absorb noise in medium and high frequency bands, and the composite sound insulation cover after parallel superposition can achieve noise reduction effects covering low, medium and high wide frequency bands.

[0023] In this embodiment, the thin-layer sound-absorbing superstructures 3 of adjacent working frequency bands in parallel can achieve superposition and widening of the working frequency bands. The working frequency band of the combined structure is the superposition of the working frequency bands of each thin-layer sound-absorbing superstructure 3. By combining a plurality of thin-layer sound-absorbing superstructures 3 of different working frequency bands, a broadband sound absorption and noise reduction effect can be achieved.

[0024] Among them, the introduction of porous sound-absorbing material 4 can greatly improve the noise attenuation effect of the composite soundproof cover in the medium and high frequency bands. Compared with traditional leather and other soundproof covers that are mainly reflective, the composite soundproof cover can achieve the effect of "absorbing instead of isolating" noise by absorbing sound energy, thereby resisting sound leakage and achieving a higher average insertion loss improvement through a smaller increase in surface density. Since the composite soundproof cover has a strong sound absorption ability and can effectively dissipate sound energy, it is not necessary to completely wrap the target noise source or equipment, and can also obtain considerable sound insulation and noise reduction effects, which is suitable for work environments that require ventilation and heat dissipation. Since the noise attenuation effect of the thin-layer sound-absorbing superstructure 3 is mainly determined by the structure itself, the material of the composite soundproof cover can be flexibly replaced according to the requirements of the use environment.

[0025] Example 2 The present invention provides a method for using a thin-layer sound-absorbing superstructure composite sound insulation cover, comprising: 1) Determine the shape and size of the cover plate 1 and the conformal frame 2 according to the target noise source or equipment size; 2) According to the bandwidth of the required noise reduction frequency band, the frequency band is divided into a plurality of sub-bands. For medium and low frequency noise, the structural area, the number of openings, the opening radius, the opening thickness, the number of cavities, the cavity length, and the cavity depth of the thin-layer sound absorbing superstructure 3 are adjusted so that the sound absorption bandwidth of each thin-layer sound absorbing superstructure 3 corresponds to each sub-band; for medium and high frequency noise, a porous sound absorbing material 4 having a thickness similar to that of the thin-layer sound absorbing superstructure 3 is selected; 3) The thin layer sound absorbing superstructure 3 and the porous sound absorbing material 4 are stacked in parallel and embedded on the conformal frame 2, so as to achieve the effect of "absorbing instead of isolating" the noise by absorbing the sound energy, thereby achieving broadband noise reduction.

[0026] Example 3 1. Design of thin-layer sound-absorbing superstructure and study of parallel coupling effect In order to illustrate the design flexibility of the structural parameters of the thin-layer sound-absorbing superstructure in the present invention, six thin-layer sound-absorbing superstructures with different working frequency bands are designed. Each thin-layer sound-absorbing superstructure 3 is composed of three parts, such as Figure 2 As shown, it includes a perforated plate 301, a labyrinth channel 302 and a homogenous plate 303. Among them, the labyrinth channel contains multiple units of different volumes. Compared with the basic Helmholtz resonance cavity, this structure transfers the required dimensions in the thickness direction to the planar thin-layer labyrinth channel, thereby achieving a significant reduction in the thickness of the sound-absorbing structure. In order to overcome the attenuation of sound absorption performance caused by the sparse distribution of thin-layer units after the size transfer, a phase cancellation mechanism between connected units is introduced to compensate for the sound absorption performance of the thin-layer sound-absorbing superstructure. By adjusting the thickness and perforation diameter of the perforated plate, the thickness of the labyrinth channel and the volume size of each unit, the noise attenuation effect for different working frequency bands can be achieved.

[0027] The schematic diagrams of the six thin-layer sound-absorbing superstructures are shown in Figure 2. Figure 3 As shown in a, the cross section of each thin-layer sound-absorbing superstructure is a square, and the side lengths are marked in the figure. The commercial finite element software COMSOL Multiphysics was used to simulate and calculate their sound absorption coefficients. The calculation results are shown in Figure 3 b and Figure 3 As shown in Figure c, the operating frequency bands of the six thin-layer sound-absorbing superstructures are 250 ~ 500 Hz, 600 ~ 1300 Hz, 900 ~ 2000 Hz, 1300 ~ 2500 Hz, 1700 ~ 3100 Hz and 2000 ~ 3600 Hz. It can be seen from the figure that within their operating frequency bands, the thin-layer sound-absorbing superstructures all produce relatively continuous sound absorption peaks, which can achieve good sound absorption effects in specific frequency bands. Therefore, by adjusting the structural parameters of the thin-layer sound-absorbing superstructure, the noise attenuation effects in different frequency bands can be achieved, which has good parameter design flexibility.

[0028] In order to illustrate the parallel coupling effect of different types of thin-layer sound-absorbing superstructures in the present invention, the parallel coupling effect between four groups of thin-layer sound-absorbing superstructures in adjacent working frequency bands was studied, namely, the parallel coupling effect between the thin-layer sound-absorbing superstructures in the working frequency band of 250 ~ 500 Hz and the working frequency band of 600 ~ 1300 Hz, the parallel coupling effect between the thin-layer sound-absorbing superstructures in the working frequency band of 600 ~ 1300 Hz and the working frequency band of 1300 ~ 2500 Hz, the parallel coupling effect between the thin-layer sound-absorbing superstructures in the working frequency band of 900 ~ 2000 Hz and the working frequency band of 1700 ~ 3500 Hz, and the parallel coupling effect between the thin-layer sound-absorbing superstructures in the working frequency band of 900 ~ 2000 Hz and the working frequency band of 2000 ~ 3600 Hz. The results of the four groups of parallel coupling effect studies are shown in FIG. Figure 4 As shown in the figure. The calculation results of each group all show that the parallel connection of thin-layer sound-absorbing superstructures with adjacent working frequency bands can achieve the superposition and widening of the working frequency bands. The working frequency band of the combined structure is the superposition of the working frequency bands of each thin-layer sound-absorbing superstructure, although this parallel superposition method will reduce the sound absorption amplitude of the combined structure. This shows that by combining a variety of thin-layer sound-absorbing superstructures with different working frequency bands, a broadband sound absorption and noise reduction effect can be achieved.

[0029] In order to illustrate the parallel coupling effect between the thin layer sound absorbing superstructure and the porous sound absorbing material in the present invention, the sound absorption coefficient of the selected porous sound absorbing material was firstly tested. The experiment was carried out using an impedance tube system and repeated three times. The test results are shown in the figure. Figure 5As shown in a. Due to the limitation of the impedance tube itself, the highest frequency that can be measured is 1600 Hz. The test results show that in the frequency range before 1400 Hz, the sound absorption coefficient of the porous sound absorbing material is about 0.4, which does not show a good sound absorption effect. According to the sound absorption performance of common porous sound absorbing materials and combined with the test results, the porous sound absorbing material used should have a good sound absorption effect in the medium and high frequency range after 1600 Hz. A large-sized flat-plate thin-layer sound absorbing superstructure composite sample was prepared by 3D printing technology and experimental tests were carried out. The lateral size of the large-sized flat-plate thin-layer sound absorbing superstructure composite sample is 830 mm×830 mm. There are four types of thin-layer sound absorbing superstructures used, and the working frequency bands are 250 ~ 500 Hz, 600 ~ 1300 Hz, 900 ~ 2000 Hz and 1700 ~ 3100 Hz, covering 250~ 3100 Hz as a whole. A 20 mm wide channel is reserved between two adjacent thin-layer sound-absorbing superstructures, and the thickness of the homogeneous backplane of the channel is 5 mm. The parallel coupling effect between the thin-layer sound-absorbing superstructure and the porous sound-absorbing material is studied by filling or not filling the channel with porous sound-absorbing material. The experiment was carried out in a semi-anechoic chamber-reverberation chamber, and the test was carried out according to the 1 / 3 octave measurement point. The test results are shown in Figure 5 As shown in b. From the test results, it can be seen that the large-sized flat-plate thin-layer sound-absorbing superstructure composite sample filled with porous sound-absorbing material has a higher sound insulation amplitude at almost all measured frequency points compared with the sample not filled with porous sound-absorbing material, especially in the frequency range after 1000 Hz. This shows that the filling of porous sound-absorbing material can better improve the sound insulation performance of large-sized flat-plate thin-layer sound-absorbing superstructure composite samples in the medium and high frequency range. Compared with the prediction results of the mass law, the large-sized flat-plate thin-layer sound-absorbing superstructure composite sample filled with porous sound-absorbing material can break the constraints of the mass law in the frequency range before 3150 Hz, and has a good broadband noise reduction effect. This shows that the parallel superposition of thin-layer sound-absorbing superstructure and porous sound-absorbing material can greatly improve the noise attenuation effect of the composite sound insulation cover in the medium and high frequency bands.

[0030] 2. Composite sound insulation enclosure structure design and performance analysis In order to illustrate the good acoustic performance of the thin-layer sound-absorbing superstructure composite soundproof cover in the present invention, the noise control problem of a certain high-speed train onboard compressor is taken as the research object, and the structural design and performance analysis of the composite soundproof cover are carried out. In order to improve the space utilization rate, the surface configuration design of the composite soundproof cover is realized through the polygon fitting idea. The simplified model of the compressor is as follows Figure 6 As shown in a, the polygon fitting idea is as follows Figure 6As shown in b. Since the shape of the thin-layer sound-absorbing superstructure is a standard cube, it is not feasible to directly combine the thin-layer sound-absorbing superstructure into polygons. Therefore, the inner and outer wall panels are used to connect each side, as shown in the schematic diagram Figure 6 As shown in c, the overall structure has reached an octagonal shape, including nine long sides and nine short sides. In the nine long side regions, a thin layer of sound absorbing superstructure or porous sound absorbing material is arranged; in the nine short side regions, porous sound absorbing material is used for filling.

[0031] Four thin-layer sound-absorbing superstructures with different working frequency bands and porous sound-absorbing materials are combined to design a composite sound insulation cover I. The structural diagram is shown in Figure 6 d. The operating frequency bands of the four thin-layer sound-absorbing superstructures are 250 ~ 500 Hz, 600 ~ 1300 Hz, 900 ~ 2000 Hz and 1700 ~ 3100 Hz, respectively, covering 250 ~ 3100 Hz as a whole. The cover of the composite soundproof cover I is designed as a labyrinth channel structure. The surface density of the composite soundproof cover I is about 9.80 kg / m 2 , the wall thickness is about 22mm.

[0032] The sample of composite sound insulation cover I was prepared by 3D printing technology. The sample photo is shown in the figure below. Figure 7 The acoustic performance is tested in a semi-anechoic chamber. The experimental equipment and measurement points are arranged as shown in the figure. Figure 7 As shown in Figure 2, during the data analysis phase, the average of the results of the five measurement points arranged during the experiment was taken to conduct a comprehensive analysis of the acoustic performance, and the sound pressure level curve and insertion loss curve of the experimental test were obtained. The results are shown in Figure 2. Figure 7 c and Figure 7 d. Figure 7 c It can be seen that compared with traditional leather and other reflective sound insulation covers, the composite sound insulation cover I has a lower sound pressure level amplitude in the frequency range of 63 ~ 1250 Hz and a better sound insulation effect. Figure 7 It can be seen that in the frequency range of 63 ~ 1250 Hz, the insertion loss of the composite soundproof cover I is about 10.28 dB higher than that of the traditional leather soundproof cover on average, and the maximum increase can reach 19.71 dB, which occurs at 80 Hz. According to the formula of average insertion loss (average insertion loss = total sound pressure level of Gaussian white noise - total sound pressure level of soundproof cover), under A weighting, the analysis frequency range is 25 ~ 10000 Hz, the average insertion loss of the traditional leather soundproof cover is 20.06 dB, and the average insertion loss of the composite soundproof cover I is 24.47 dB, and the average insertion loss is increased by 4.41 dB, which shows that the composite soundproof cover I has a good sound insulation effect in a wide frequency range.

[0033] By adjusting the type and quantity of thin-layer sound-absorbing superstructures in the composite soundproof cover and the distribution of porous sound-absorbing materials, the surface density and noise reduction effect of the composite soundproof cover can be optimized. Two composite soundproof covers are optimized and designed, named composite soundproof cover II and composite soundproof cover III, respectively. The schematic diagram is shown in the figure. Figure 8 As shown in a. There are two types of thin-layer sound-absorbing superstructures in the composite soundproof cover II, and their operating frequency bands are 600 ~ 1300 Hz and 1300 ~ 2500 Hz, respectively, covering a frequency range of 600 ~ 2500 Hz; there is one type of thin-layer sound-absorbing superstructure in the composite soundproof cover III, and its operating frequency band is 600 ~ 1300 Hz. For the layout of porous sound-absorbing materials, the form of "porous sound-absorbing material + homogeneous backboard" is adopted, that is, the outer side of the composite soundproof cover is a homogeneous board, and the inner side is filled with porous sound-absorbing materials. The surface density of the composite soundproof cover II is about 6.99 kg / m 2 The surface density of the composite sound insulation cover III is about 6.74 kg / m 2 The wall thickness of the two composite sound insulation covers is about 22 mm. Figure 8 b. The acoustic performance was tested in a full anechoic chamber. The sound pressure level curve and insertion loss curve are shown in Figure 8 c and Figure 8 d. It can be found that the sound pressure level and insertion loss curves of the two composite soundproof enclosures are similar, and they have comparable acoustic performance. Compared with Gaussian white noise, the sound pressure level of the two composite soundproof enclosures has been greatly reduced in the test frequency range, and they have higher insertion losses in the frequency range after 250 Hz. Among them, the average insertion loss of the composite soundproof enclosure II is 27.50 dB, and the average insertion loss of the composite soundproof enclosure III is 28.00 dB.

[0034] Therefore, by combining a variety of thin-layer sound-absorbing superstructures and porous sound-absorbing materials with different working frequency bands, a low-frequency broadband sound insulation and noise reduction effect can be achieved. Compared with traditional leather and other reflective sound insulation covers, composite sound insulation covers can achieve the effect of "absorbing instead of isolating" noise by absorbing sound energy, thereby resisting sound leakage and achieving a higher average insertion loss improvement through a smaller increase in surface density, especially composite sound insulation cover III, which can increase 1.54 kg / m 2 The average insertion loss is increased by 7.94 dB at the expense of areal density.

[0035] Since the composite soundproof cover has strong sound absorption ability and can effectively dissipate sound energy, it is not necessary to completely wrap the target noise source or equipment to obtain a considerable sound insulation and noise reduction effect. In addition, the thin-layer sound-absorbing superstructure composite soundproof cover has the advantages of high space utilization, strong space adaptability, thin thickness, low surface density, and strong material replaceability while ensuring the sound insulation effect.

[0036] According to the above data, it can be seen that the technical effects that the present invention can achieve are as follows: 1. Through the parallel superposition design of thin-layer sound-absorbing superstructure and porous sound-absorbing material, the composite soundproof cover can achieve noise reduction effects covering low, medium and high wide frequency bands; 2. The structure and size of the cover plate and conformal frame can be flexibly designed according to the use requirements, with good applicability; 3. By adjusting the structural parameters of the thin-layer sound-absorbing superstructure, the noise attenuation effect for different working frequency bands can be achieved; 4. Connecting thin-layer sound-absorbing superstructures of adjacent working frequency bands in parallel can realize the superposition and widening of working frequency bands. By combining thin-layer sound-absorbing superstructures of multiple working frequency bands, a broadband sound absorption and noise reduction effect can be achieved. 5. The introduction of porous sound-absorbing materials can greatly improve the noise attenuation effect of the composite sound insulation cover in the medium and high frequency bands; 6. Compared with traditional leather and other reflective sound insulation covers, composite sound insulation covers can achieve the effect of "absorbing instead of isolating" noise by absorbing sound energy, thereby resisting sound leakage and achieving a higher average insertion loss through a smaller increase in surface density; 7. Since the composite sound insulation cover has strong sound absorption ability and can effectively dissipate sound energy, it is not necessary to completely wrap the target noise source or equipment, and can also achieve considerable sound insulation and noise reduction effects. It is suitable for work places that require ventilation and heat dissipation; 8. The composite sound insulation cover not only has good sound insulation effect, but also has the advantages of high space utilization, strong space adaptability, thin thickness, low surface density and strong material replaceability. It has broad application prospects in the noise control of various electromechanical products.

[0037] In summary, according to the above characteristics of a thin-layer sound-absorbing superstructure composite soundproof cover provided by the present invention, the composite soundproof cover provided by the present invention can achieve a good noise attenuation effect in a wide frequency range. Among them, the thin-layer sound-absorbing superstructure can absorb medium and low frequency noise, and the porous sound-absorbing material can absorb medium and high frequency noise, so that the working frequency band of the entire soundproof cover can cover low, medium and high wide frequency bands. In this soundproof cover, the structure and size of the cover plate and the conformal frame can be flexibly designed according to the use requirements, and have good applicability. Compared with traditional leather and other soundproof covers that are mainly reflective, the composite soundproof cover can achieve the effect of "absorbing instead of isolating" noise by absorbing sound energy, thereby resisting sound leakage and achieving a higher average insertion loss improvement through a small increase in surface density. Due to its strong sound absorption ability, it can effectively lose sound energy, so that it is not necessary to completely wrap the target noise source or equipment, and can also obtain a considerable sound insulation and noise reduction effect. In addition, the device also has the advantages of high space utilization, strong space adaptability, thin thickness, low surface density and strong material replaceability. In summary, compared with the existing sound insulation covers, this composite sound insulation cover has a wider working frequency band and better sound insulation effect while ensuring thin thickness and low surface density. It has broad application prospects in noise control of various electromechanical products.

[0038] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the attached claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention. Any figure mark in the claims should not be regarded as limiting the claims involved.

[0039] In addition, it should be understood that although this specification is described in accordance with the implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation modes that can be understood by those skilled in the art. The above content is only to illustrate the technical idea of ​​the present invention, and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution according to the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A thin layer sound absorbing superstructure composite sound insulation cover, characterized in that: The invention comprises a cover plate (1), a conformal frame (2), a thin-layer sound-absorbing superstructure (3) and a porous sound-absorbing material (4). The thin-layer sound-absorbing superstructure (3) and the porous sound-absorbing material (4) are stacked in parallel and embedded on the conformal frame (2) to achieve a broadband noise reduction effect. The cover plate (1) is arranged on the top of the conformal frame (2).

2. The thin-layer sound-absorbing superstructure composite soundproof cover according to claim 1, characterized in that: The cover plate (1) is a labyrinth-shaped channel structure and can be filled with porous sound-absorbing material. The structure is designed with openings according to the use requirements of the equipment.

3. The thin-layer sound-absorbing superstructure composite soundproof cover according to claim 1, characterized in that: The thin layer sound absorbing superstructure (3) and the porous sound absorbing material (4) are combined and spliced ​​through a conformal frame (2), and the shape and size of the conformal frame (2) are designed according to the target noise source or equipment size.

4. The thin-layer sound-absorbing superstructure composite soundproof cover according to claim 1, characterized in that: The structural area, number of openings, opening radius, opening thickness, number of cavities, cavity length, and cavity depth of the thin-layer sound-absorbing superstructure (3) can be flexibly designed to meet the noise attenuation effects of different working frequency bands.

5. The thin-layer sound-absorbing superstructure composite sound insulation cover according to claim 1, characterized in that: Each thin layer of sound absorbing superstructure (3) can absorb noise in different frequency ranges of medium and low frequency bands, the porous sound absorbing material (4) can absorb noise in medium and high frequency bands, and the composite sound insulation cover after parallel superposition can achieve a noise reduction effect covering low, medium and high wide frequency bands.

6. The thin-layer sound-absorbing superstructure composite soundproof cover according to claim 1, characterized in that: Thin-layer sound-absorbing superstructures (3) with adjacent working frequency bands connected in parallel can achieve superposition and broadening of the working frequency bands. The working frequency band of the combined structure is the superposition of the working frequency bands of each thin-layer sound-absorbing superstructure (3). By combining a plurality of thin-layer sound-absorbing superstructures (3) with different working frequency bands, a broadband sound absorption and noise reduction effect can be achieved.

7. The thin-layer sound-absorbing superstructure composite soundproof cover according to claim 1, characterized in that: The thin-layer sound-absorbing superstructure (3) comprises a perforated plate (301), a labyrinth-shaped channel (302), and a homogeneous plate (303) which are arranged in sequence from top to bottom.

8. The thin-layer sound-absorbing superstructure composite soundproof cover according to claim 1, characterized in that: The thickness of the thin layer sound-absorbing superstructure (3) used to absorb noise in the medium and low frequency bands is 1 / 25 to 1 / 57 of the wavelength of the sound wave.

9. The thin-layer sound-absorbing superstructure composite sound insulation cover according to claim 8, characterized in that: The thickness of the porous sound-absorbing material (4) for absorbing noise in the medium and high frequency bands is similar to that of the thin-layer sound-absorbing superstructure (3), so that the entire composite sound insulation cover has the advantages of thin thickness and low surface density, and is suitable for compact and lightweight working environments.

10. A method for using a thin-layer sound-absorbing superstructure composite soundproof enclosure according to any one of claims 1 to 9, characterized in that: include: 1) Determine the shape and size of the cover plate (1) and the conformal frame (2) according to the target noise source or equipment size; 2) According to the bandwidth of the required noise reduction frequency band, the frequency band is divided into a plurality of sub-bands. For medium and low frequency noise, the structural area, the number of openings, the opening radius, the opening thickness, the number of cavities, the cavity length, and the cavity depth of the thin layer sound absorbing superstructure (3) are adjusted so that the sound absorption bandwidth of each thin layer sound absorbing superstructure (3) corresponds to each sub-band; for medium and high frequency noise, a porous sound absorbing material (4) having a thickness similar to that of the thin layer sound absorbing superstructure (3) is selected; 3) The thin layer sound absorbing superstructure (3) and the porous sound absorbing material (4) are stacked in parallel and embedded on the conformal frame (2), so as to achieve the effect of "absorbing instead of isolating" noise by absorbing sound energy, thereby achieving broadband noise reduction.

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