CN112259066A - N-order acoustic metamaterial low-frequency sound insulation structure - Google Patents
N-order acoustic metamaterial low-frequency sound insulation structure Download PDFInfo
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Abstract
The invention discloses an N-order acoustic metamaterial low-frequency sound insulation structure, which relates to the technical field of mechanical noise and environmental noise control, and comprises a plurality of (N-1) -order acoustic metamaterial low-frequency sound insulation structures which are expanded along x and y directions in an array manner, an N-order mass block and an external support frame which are adhered to the center of the (N-1) -order acoustic metamaterial expansion structure, wherein N is more than or equal to 2, and when N is 2, the second-order acoustic metamaterial low-frequency sound insulation structure comprises a plurality of acoustic metamaterial unit cells which are expanded along the x and y directions in an array manner and a second-order mass block which is adhered to the center of the expansion structure; the sound insulation peak generated by the structure is generated by the modal coupling anti-resonance effect of the adjacent-order acoustic metamaterial, and the N-order mass block is used for enhancing the modal coupling anti-resonance effect. The invention has the characteristics of simple structure, easy adjustment and the like, and meanwhile, the structure has a large expansion space and has potential application prospect for multi-frequency sound insulation in a low-frequency range.
Description
Technical Field
The invention relates to the technical field of mechanical noise and environmental noise control, in particular to an N-order acoustic metamaterial low-frequency sound insulation structure.
Background
With the use of a large number of electromechanical devices, the noise problem is becoming more serious in our daily production life. Especially, the isolation of low frequency noise is a difficult problem because the wavelength of the low frequency noise is long and easily penetrates through the sound barrier. As can be seen from the mass law, the use of traditional homogeneous materials for noise attenuation requires a structure with a sufficiently high areal density, which tends to make the weight and thickness of the sound-insulating structure too large to be used in practical projects. However, the advent of acoustic metamaterials has brought new ideas and methods for noise control. The acoustic metamaterial is an artificial composite structure, can realize negative equivalent dynamic parameters such as negative equivalent mass density and negative equivalent bulk modulus, and can realize an extraordinary control effect on sound waves in certain specific frequency bands. The acoustic metamaterial sound insulation structure based on the local resonance principle has potential engineering application prospects. A typical acoustic metamaterial unit cell was proposed in 2008, which is composed of a membrane, a supporting frame and a central mass, and can achieve near total reflection of acoustic waves at the antiresonance frequency of the unit cell.
With the rapid development of the acoustic metamaterial, more and more acoustic metamaterial unit cells for controlling low-frequency noise are proposed. However, most of the existing researches on low-frequency sound insulation of the acoustic metamaterial are proposed based on a unit cell structure. If the engineering application performance of the acoustic metamaterial is to be improved, the expansion of the acoustic metamaterial unit cell array must be considered to form a large-scale acoustic metamaterial structure.
However, current research shows that when the acoustic metamaterial unit cell array is expanded to a large-scale structure, the sound insulation performance of the acoustic metamaterial unit cell array is different from that of the acoustic metamaterial unit cell, namely, the low-frequency sound insulation design aiming at the unit cell is not suitable for the large-scale structure any more, and the low-frequency sound insulation performance of the expanded structure behind the unit cell array is poor, so that an effective low-frequency sound insulation peak is difficult to form. This problem severely limits the engineering applicability of acoustic metamaterials in low frequency sound insulation.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention provides a high-order acoustic metamaterial low-frequency sound insulation structure which is light and simple in structure, and can realize high sound insulation at a specific frequency in a low-frequency range by adjusting structure and material parameters. The invention has the idea of nested design, the second-order acoustic metamaterial can be formed by adding the mass block at the center of the acoustic metamaterial unit cell extension structure, the third-order acoustic metamaterial can be formed by adding the mass block at the center of the second-order acoustic metamaterial extension structure, and the like. For the N-order acoustic metamaterial, the whole board mode of the high-order acoustic metamaterial is adjusted to be lower than the whole board mode of the low-order acoustic metamaterial, and N-1 low-frequency sound insulation peaks can be realized by utilizing coupling antiresonance between adjacent-order acoustic metamaterials. Therefore, the invention can realize multi-frequency sound insulation in a low-frequency range, and has good applicability and wide application prospect for low-frequency noise with multiple noise frequencies.
In order to achieve the above object, the present invention provides an N-order acoustic metamaterial low frequency sound insulation structure, including:
a plurality of (N-1) order acoustic metamaterial low-frequency sound insulation structures extending in an array along the x and y directions, wherein,
when N is 2, the second-order acoustic metamaterial low-frequency sound insulation structure comprises a plurality of acoustic metamaterial unit cells which are expanded along the x and y directions in an array mode and a second-order mass block which is attached to the center of the expansion structure,
when N is 3, the third-order acoustic metamaterial low-frequency sound insulation structure comprises a plurality of second-order acoustic metamaterial low-frequency sound insulation structures which are expanded along the x and y directions in an array mode, a third-order mass attached to the center of the expansion structure and an external framework,
by analogy, when N is larger than 3, the N-order acoustic metamaterial low-frequency sound insulation structure comprises a plurality of (N-1) -order acoustic metamaterial low-frequency sound insulation structures which are expanded along the x and y directions in an array mode, and an N-order mass block and an external frame which are adhered to the center of the (N-1) -order acoustic metamaterial expansion structure; the sound insulation peak generated by the structure is generated by the modal coupling anti-resonance effect of the adjacent-order acoustic metamaterial, and the N-order mass block is used for enhancing the modal coupling anti-resonance effect.
The invention has the following beneficial effects:
(1) compared with the traditional large-scale acoustic metamaterial, the sound insulation device can realize a sound insulation peak with high sound insulation in a low-frequency range lower than 500Hz, and the position, the sound insulation bandwidth and the sound insulation quantity of the sound insulation peak can be adjusted by adjusting the size and the material parameters of the structure;
(2) in the invention, the first-order mass block is used for enhancing the coupling anti-resonance effect between adjacent modes of the unit cells, the high-order mass block is used for enhancing the coupling anti-resonance effect of the whole plate mode and the local mode, and the position, the bandwidth and the sound insulation quantity of a sound insulation peak can be changed by adjusting the mass of the high-order mass block;
(3) the sound insulation peak adjusting method has the characteristics of nested design, the modes of the high-order acoustic metamaterial are richer, a plurality of sound insulation peaks can be realized in a low-frequency range by adjusting the fundamental frequency of the adjacent-order acoustic metamaterial, and N-1 sound insulation peaks can be realized for the N-order acoustic metamaterial;
the conception, the specific structure and the technical effects of the present invention will be further described with reference to the accompanying drawings to fully understand the objects, the features and the effects of the present invention.
Drawings
FIG. 1 is a schematic structural diagram of a second-order acoustic metamaterial low-frequency sound insulation structure according to one embodiment of the invention;
FIG. 2 is a design schematic diagram of a high-order acoustic metamaterial low-frequency sound insulation structure according to one embodiment of the invention;
FIG. 3 is a schematic diagram of a finite element simulation model of a second-order acoustic metamaterial low-frequency sound insulation structure according to one embodiment of the invention;
FIG. 4 is a schematic diagram of a finite element simulation sound insulation curve of a second-order acoustic metamaterial low-frequency sound insulation structure according to one embodiment of the invention;
FIG. 5 is a schematic diagram of a finite element simulation sound insulation curve of a second-order acoustic metamaterial low-frequency sound insulation structure in different sizes and second-order masses according to one embodiment of the invention;
FIG. 6 is a schematic diagram of normal vibration displacement at a sound insulation peak and a sound insulation valley of a finite element simulation sound insulation curve of a second-order acoustic metamaterial low-frequency sound insulation structure according to one embodiment of the invention;
FIG. 7 is a schematic diagram of a finite element simulation sound insulation curve of a second-order acoustic metamaterial low-frequency sound insulation structure under different thicknesses of a supporting frame according to one embodiment of the invention;
FIG. 8 is a schematic diagram of a finite element simulation sound insulation curve of a second-order acoustic metamaterial low-frequency sound insulation structure according to one embodiment of the invention under different support frame material parameters;
FIG. 9 is a schematic diagram of a finite element simulation sound insulation curve of a second-order acoustic metamaterial low-frequency sound insulation structure under different sheet thicknesses according to one embodiment of the invention;
FIG. 10 is a schematic diagram of a finite element simulation sound insulation curve of a second-order acoustic metamaterial low-frequency sound insulation structure according to one embodiment of the invention under different sheet material parameters;
FIG. 11 is a sample testing schematic diagram of a second order acoustic metamaterial low frequency sound insulating structure according to one embodiment of the present invention;
fig. 12 is a schematic diagram comparing the test result and the simulation result of the second-order acoustic metamaterial low-frequency sound insulation structure according to one embodiment of the invention.
Detailed Description
The invention provides an N-order acoustic metamaterial low-frequency sound insulation structure, which comprises:
a plurality of (N-1) order acoustic metamaterial low-frequency sound insulation structures extending in an array along the x and y directions, wherein,
when N is 2, the second-order acoustic metamaterial low-frequency sound insulation structure comprises a plurality of acoustic metamaterial unit cells which are expanded along the x and y directions in an array mode and a second-order mass block which is attached to the center of the expansion structure,
when N is 3, the third-order acoustic metamaterial low-frequency sound insulation structure comprises a plurality of second-order acoustic metamaterial low-frequency sound insulation structures which are expanded along the x and y directions in an array mode, a third-order mass attached to the center of the expansion structure and an external framework,
by analogy, when N is larger than 3, the N-order acoustic metamaterial low-frequency sound insulation structure comprises a plurality of (N-1) -order acoustic metamaterial low-frequency sound insulation structures which are expanded along the x and y directions in an array mode, and an N-order mass block and an external frame which are adhered to the center of the (N-1) -order acoustic metamaterial expansion structure; the sound insulation peak generated by the structure is generated by the modal coupling anti-resonance effect of the adjacent-order acoustic metamaterial, and the N-order mass block is used for enhancing the modal coupling anti-resonance effect.
On one hand, compared with the traditional large-scale acoustic metamaterial, the sound insulation peak with high sound insulation capacity can be realized in a low-frequency range lower than 500Hz, and the position, the sound insulation bandwidth and the sound insulation capacity of the sound insulation peak can be adjusted by adjusting the size and the material parameters of the structure;
on the other hand, the first-order mass block in the invention has the function of enhancing the coupling anti-resonance effect between the adjacent modes of the unit cells, the high-order mass block has the function of enhancing the coupling anti-resonance effect of the whole plate mode and the local mode, and the position, the bandwidth and the sound insulation quantity of the sound insulation peak can be changed by adjusting the mass of the high-order mass block;
secondly, the sound insulation material has the characteristics of a nested design, the modes of the high-order acoustic metamaterial are richer, a plurality of sound insulation peaks can be realized in a low-frequency range by adjusting the fundamental frequency of the adjacent-order acoustic metamaterial, and N-1 sound insulation peaks can be realized for the N-order acoustic metamaterial;
in a word, the problem that low-frequency sound insulation performance is poor after the acoustical metamaterial unit cells are expanded to a large scale is solved, and meanwhile large-scale acoustical metamaterial low-frequency broadband sound insulation is achieved. The invention has the characteristics of simple structure, easy adjustment and the like, and meanwhile, the structure has a large expansion space and has potential application prospect for multi-frequency sound insulation in a low-frequency range.
In a preferred embodiment, the unit cell includes a square unit cell support frame having a circular through hole formed therein, a polymer sheet bonded to one side of the unit cell support frame, and a first-order mass block bonded to a central position of either side of the polymer sheet.
In a preferred embodiment, the outer shape of the unit cell support frame is any one of the following shapes: the shape of the through hole in the unit cell is any one of the following shapes: circular, triangular, rectangular, square, regular hexagonal.
In a preferred embodiment, the polymer sheet may be made of any one of the following materials: the unit cell supporting frame and the external frame may be any one of the following materials: FR4 glass fiber, epoxy resin, ABS resin, organic glass, iron and aluminum.
In a preferred embodiment, a first-order mass block is arranged in the center of the high polymer thin plate of the acoustic metamaterial unit cell, a high-order mass block is arranged in the center of the high-order acoustic metamaterial, and the first-order mass block and the high-order mass block can be made of iron, aluminum or nonmetal and have circular, circular or square cross sections.
In a preferred embodiment, the central mass of the higher order acoustic metamaterial may be placed on the support frame, or may be placed on the unit cell to cover the unit cell, and the central mass of the 4 × 4 higher order acoustic metamaterial is placed on the support frame.
In a preferred embodiment, the N-order acoustic metamaterial is not limited in the number of (N-1) -order acoustic metamaterials.
In a preferred embodiment, the frequency position, the sound insulation bandwidth and the sound insulation quantity of the sound insulation peak can be adjusted by adjusting the structures, the material parameters and the mass size of the Nth-order mass block of the support frame and the high polymer thin plate.
Specific embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. While specific embodiments of the invention are shown in the drawings, it should be understood that the invention may be embodied in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.
In the drawings, structurally identical elements are represented by like reference numerals, and structurally or functionally similar elements are represented by like reference numerals throughout the several views. The size and thickness of each component shown in the drawings are arbitrarily illustrated, and the present invention is not limited to the size and thickness of each component. The thickness of the components may be exaggerated where appropriate in the figures to improve clarity.
It should be noted that certain terms are used throughout the description and claims to refer to particular components. As one skilled in the art will appreciate, various names may be used to refer to a component. This specification and claims do not intend to distinguish between components that differ in name but not function. In the following description and in the claims, the terms "include" and "comprise" are used in an open-ended fashion, and thus should be interpreted to mean "include, but not limited to. The description which follows is a preferred embodiment of the invention, but is made for the purpose of illustrating the general principles of the invention and not for the purpose of limiting the scope of the invention. The scope of the present invention is defined by the appended claims.
For better understanding, a second-order acoustic metamaterial is taken as an example for illustration, and fig. 1 is a schematic diagram of a high-order acoustic metamaterial low-frequency sound insulation structure according to an embodiment of the invention. As shown in FIG. 1, the second-order acoustic metamaterial low-frequency sound insulation structure 1 comprises a plurality of acoustic metamaterial unit cells 2 which are expanded in an array mode along the x direction and the y direction and a second-order mass block 3 which is attached to the center of the expanded structure. As shown in fig. 2, the third-order acoustic metamaterial low-frequency sound insulation structure 7 comprises a plurality of second-order acoustic metamaterials 1 extending in an array in the x and y directions, a third-order mass 8 attached to the center of the extending structure and an external support frame 9. By analogy, the lower-frequency sound insulation structure of the higher-order acoustic metamaterial is as follows: the N-order acoustic metamaterial can be composed of a plurality of (N-1) -order acoustic metamaterials extending in the x direction and the y direction in an array mode, an N-order mass block and an outer frame, wherein the N-order mass block is adhered to the center of the (N-1) -order acoustic metamaterial extending structure.
In the N-order acoustic metamaterial low-frequency sound insulation structure, the acoustic metamaterial unit cell 2 comprises: a square unit cell supporting frame 4 with a circular through hole inside, a high molecular polymer thin plate 5 and a first-order mass block 6. The high polymer thin plate 5 is adhered to the surface of the unit cell supporting frame 4, and the first-order mass block 6 is adhered to the center of either side of the high polymer thin plate 5.
In the N-order acoustic metamaterial low-frequency sound insulation structure, the outer shape of the unit cell supporting frame can be any one of geometrical regular shapes such as a triangle, a rectangle, a square and a regular hexagon, and the shape of the through hole in the unit cell can be a geometrical regular shape such as a circle, a triangle, a rectangle, a square and a regular hexagon and other geometrical irregular shapes.
In the N-stage acoustic metamaterial low-frequency sound insulation structure, the high polymer thin plate 5 can be a nylon plate, a PET plate or a PEI plate, and the unit cell supporting frame 4 and the external frame can be made of FR4 glass fiber, epoxy resin, ABS resin, organic glass, iron or aluminum and the like.
In the N-order acoustic metamaterial low-frequency sound insulation structure, the center of a high polymer thin plate 5 of an acoustic metamaterial unit cell 2 is provided with a first-order mass block 6, the center of a high-order acoustic metamaterial is provided with high-order mass blocks 3 and 8, the first-order mass block 6 and the high-order mass blocks 3 and 8 are made of metal such as iron and aluminum and nonmetal, and the cross section of the first-order mass block 6 and the high-order mass blocks 3 and 8 is circular, square and the like.
In the N-order acoustic metamaterial low-frequency sound insulation structure, the central mass block of the N-order acoustic metamaterial can be placed on the supporting frame or can be placed on the unit cell to cover the unit cell, and the central mass block of the 4 x 4 high-order acoustic metamaterial is placed on the supporting frame.
In the N-order acoustic metamaterial low-frequency sound insulation structure, the number of the acoustic metamaterial unit cells 2 contained in the second-order acoustic metamaterial 1, the number of the second-order acoustic metamaterial 1 contained in the third-order acoustic metamaterial 7 and the number of the N-1-order acoustic metamaterial contained in the N-order acoustic metamaterial are not limited. The higher order acoustic metamaterials are all illustrated in a 4 x 4 array.
In the N-order acoustic metamaterial low-frequency sound insulation structure, the generated sound insulation peak is generated through modal coupling antiresonance of adjacent-order acoustic metamaterials, and the high-order mass is used for enhancing the modal coupling antiresonance effect. For an N-order acoustic metamaterial, the sound insulation peaks are generated by modal coupling antiresonance between N-order acoustic metamaterials, (N-1) order acoustic metamaterials, (N-1) order acoustic metamaterials, and the unit cells of the acoustic metamaterials, one sound insulation peak can generate N-1 sound insulation peaks, wherein the N-order mass block is used for enhancing the coupling antiresonance effect between the N-order acoustic metamaterials and the (N-1) order acoustic metamaterials.
In the N-order acoustic metamaterial low-frequency sound insulation structure, the frequency position of a sound insulation peak, the sound insulation bandwidth and the sound insulation quantity can be adjusted by adjusting the structures and material parameters of the supporting frame and the high polymer thin plate and the mass of the central mass block.
In one embodiment, to further understand the present invention, a finite element simulation study was conducted on the second order acoustic metamaterial low frequency sound insulation structure shown in fig. 1 to reveal the sound insulation mechanism thereof. The external side length of the square supporting frame 4 of the unit cell 2 is 22mm, the radius of the internal circular through hole is 10mm, and the thickness of the supporting frame 4 is 2 mm; the thickness h of the high polymer sheet 5 is 0.2 mm; radius of the first-order mass block 6 is r12mm thick h 11 mm; radius of the second order mass 3 is r25mm thick h 24 mm. The material of the supporting frame 4 is PA6, and its density, elastic modulus and poisson ratio are respectively: rhof＝1150kg/m3，Ef＝2GPa，μf0.4, and the damping coefficient is considered to be 0.1; the high molecular polymer sheet 5 is made of PET, and the density, the elastic modulus and the poisson ratio thereof are respectively as follows: rhop＝1380kg/m3，Ep＝2GPa，μp0.34, and a damping coefficient of 0.1 is considered; the first-order mass block and the second-order mass block are made of iron, and the density, the elastic modulus and the Poisson ratio of the first-order mass block and the second-order mass block are respectively as follows: 7850kg/m3, 205GPa, 0.28. The surface density of the whole low-frequency sound insulation structure is only 4.017kg/m 2. In order to analyze the sound insulation characteristic of the high-order acoustic metamaterial low-frequency sound insulation structure, finite element simulation calculation is carried out on the low-frequency sound insulation structure by adopting finite element software COMSOL Multiphysics 5.4. The finite element simulation model is shown in fig. 3 and comprises an incident sound cavity 10, a second-order acoustic metamaterial low-frequency sound insulation structure 1 and a transmission sound cavity 11. When the plane sound wave enters from the plane wave radiation surface 12, passes through the second-order acoustic metamaterial low-frequency sound insulation structure 1 and exits from the plane wave radiation surface 13, at the moment, the incident sound cavity 10 contains incident sound pressure Pi and reflected sound pressure Pr, and the transmission sound cavity 11 contains transmission sound pressure Pt, so that the calculation can be carried out according to the incident sound pressure Pi and the reflected sound pressure PrThe normal incidence sound transmission loss STL of the low frequency sound insulation structure is shown in the following formula 1.
Wherein is Win＝|pi|2/(2ρ0c0) Incident acoustic power; wout＝|pt|2/(2ρ0c0) Is the transmitted acoustic power; rho0Is the air density; c. C0Is the propagation speed of sound waves in air.
The incident sound pressure is defined to be 1Pa, the frequency scanning frequency band is 8Hz-1600Hz, and the step length is 8 Hz. In order to make comparison more intuitive and quantitative, finite element simulation is also performed on the traditional acoustic metamaterial unit cell expansion structure, the difference between the two structures is that a second-order mass block exists or not, and the sound insulation curves of the two structures are shown in fig. 4. From the figure, it can be obviously found that in the low frequency range lower than 500Hz, the sound insulation quantity of the invention is obviously higher than that of the traditional acoustic metamaterial unit cell extension structure. In addition, in the medium-frequency range higher than 500Hz, the sound insulation peak of the invention is obviously shifted to low frequency, and the sound insulation quantity is slightly increased. Simulation results show that compared with the traditional acoustic metamaterial unit cell array extension structure, the low-frequency sound insulation structure has the obvious advantage of low-frequency sound insulation, and the medium-frequency sound insulation performance can be improved to a certain extent. This is because the introduction of the second order mass 3 enhances the coupled antiresonance between the whole plate mode and the cell local mode. Further simulation researches the influence of the mass size of the second-order mass block 3 on the low-frequency sound insulation structure, the rest sizes are kept unchanged, and only the thickness of the second-order mass block 3 is changed to respectively: 2mm, 4mm and 6mm, the finite element simulation results are shown in fig. 5. Simulation results show that the low-frequency sound insulation peak can be further moved to the low frequency by increasing the mass of the second-order mass block 3, the sound insulation bandwidth is further increased, the sound insulation quantity is further increased, and in addition, the medium-frequency sound insulation peak can be moved to the low frequency, and the sound insulation quantity is slightly increased. This shows that the second order mass 3 plays a crucial role in coupling antiresonance between the whole plate mode and the cell local mode. In order to further disclose the sound insulation mechanism of the invention, taking the thickness of the second-order mass block 3 as an example, the normal vibration displacement at the first-order sound insulation valley A, the first-order sound insulation peak B, the second-order sound insulation valley C, the second-order sound insulation peak D and the third-order sound insulation valley E on the sound insulation curve is extracted, as shown in FIG. 6. At sound insulation valley a (224Hz), the whole plate shows a downward vibration mode, and the unit cells hardly vibrate, which is the first-order vibration mode of the whole plate. At sound insulation valley C (552Hz), the unit cells exhibit a downward vibration mode, while the entire plate hardly vibrates (as the support frame hardly vibrates), which is the first-order vibration mode of the unit cells. At sound insulation valley E (1224Hz), the whole plate shows a vibration mode with the center upward and the outside downward, and the unit cells hardly vibrate independently, and the unit cells are in a second-order vibration mode of the whole plate. At the sound insulation peak B (352Hz), the whole plate shows downward vibration displacement, the unit cells show upward vibration displacement, and the coupling anti-resonance of the first-order vibration mode of the whole plate and the first-order vibration mode of the unit cells occurs at the moment. At a sound insulation peak D (936Hz), the whole plate shows vibration displacement with the center downward and the outside upward, the unit cells generate downward vibration displacement, and the coupling anti-resonance of the first-order vibration mode of the unit cells and the second-order vibration mode of the whole plate occurs at the moment. Therefore, the high-order acoustic metamaterial low-frequency sound insulation structure designed by the invention generates a low-frequency sound insulation peak based on a coupling anti-resonance mechanism between a whole plate mode and a unit cell mode.
In one embodiment, to further understand the present invention, finite element simulations have studied the effect of support frame structural parameters on the sound insulation performance of a second order acoustic metamaterial low frequency sound insulation structure. Taking the thickness of the supporting frame as an example, the remaining structural parameters and material parameters are kept consistent with the finite element simulation model shown in fig. 3, and only the thickness of the supporting frame is changed as follows: h1 mm, H2 mm, H3 mm, the finite element simulation results are shown in fig. 7. Simulation results show that the low-frequency sound insulation peak can move to high frequency by increasing the thickness of the supporting frame, the sound insulation bandwidth is reduced, and the sound insulation quantity is reduced. Because the increase of the thickness of the supporting frame can make the whole plate fundamental frequency mode move to high frequency obviously, and the cellular fundamental frequency mode moves to high frequency slightly.
In one embodiment, for further understandingAccording to the invention, finite element simulation researches the influence of the material parameters of the supporting frame on the sound insulation performance of the low-frequency sound insulation structure of the second-order acoustic metamaterial. Three different materials of the support frame are selected, respectively: nylon PA1010, nylon PA6, and nylon PA 66. The densities and poisson's ratios of these three materials do not differ much, and the modulus of elasticity is the main material parameter affecting the sound insulation performance. Therefore, keeping the remaining structural and material parameters consistent with the finite element simulation model shown in fig. 3, the elastic modulus of the supporting frame is changed to: ef＝1.07GPa，Ef＝2GPa，EfThe finite element simulation results are shown in fig. 8, 8.3 GPa. Simulation results show that the increase of the elastic modulus of the supporting frame can also enable the low-frequency sound insulation peak to move towards high frequency, reduce the sound insulation bandwidth and reduce the sound insulation quantity. Because increasing the elastic modulus of the supporting frame will shift the whole board fundamental frequency mode significantly to high frequency, while the cellular fundamental frequency mode slightly shifts to high frequency.
In one embodiment, in order to further understand the invention, finite element simulation studies the influence of the structural parameters of the high polymer thin plate on the sound insulation performance of the second-order acoustic metamaterial low-frequency sound insulation structure. Taking the thickness of the polymer sheet as an example, the remaining structural parameters and material parameters are kept consistent with the finite element simulation model shown in fig. 3, and only the thickness of the polymer sheet is changed as follows: h is 0.2mm, h is 0.3mm, and h is 0.4mm, and the finite element simulation results are shown in fig. 9. Simulation results show that the low-frequency sound insulation peak can move to high frequency by increasing the thickness of the thin plate, the sound insulation bandwidth is increased, and the sound insulation quantity is increased. Because the increase of the thickness of the supporting frame can make the fundamental frequency mode of the unit cell move to high frequency obviously, and the fundamental frequency mode of the whole plate moves to high frequency slightly.
In one embodiment, to further understand the present invention, finite element simulation studies the influence of polymer sheet material parameters on the sound insulation performance of a second-order acoustic metamaterial low-frequency sound insulation structure. Three different sheet materials were selected, respectively: high density PE-HD, PET and PVC. The densities and poisson's ratios of these three materials do not differ much, and the modulus of elasticity is the main material parameter affecting the sound insulation performance. Thus, the remaining structural parameters are maintainedThe number and material parameters are consistent with those of the finite element simulation model shown in fig. 3, and the elastic modulus of the high polymer sheet is changed as follows: ef＝1.07GPa，Ef＝2GPa，EfThe finite element simulation results are shown in fig. 10, 3.5 GPa. Simulation results show that the low-frequency sound insulation peak can be moved to high frequency by increasing the elastic modulus of the thin plate, the sound insulation bandwidth is increased, and the sound insulation quantity is increased. Because the increase of the thickness of the supporting frame can make the fundamental frequency mode of the unit cell move to high frequency obviously, and the fundamental frequency mode of the whole plate moves to high frequency slightly.
In one embodiment, the finite element simulation method used in the present invention is proved to be correct and reasonable for further understanding of the present invention. A sample of the second-order acoustic metamaterial was prepared, the structural parameters and the material parameters of which were consistent with those of the finite element model shown in fig. 3, and an experimental test was performed in an impedance tube, and the test site and the sample piece were installed as shown in fig. 11. The test result is shown in fig. 12, and the comparison of the test result and the finite element simulation result shows that the sound insulation curves of the two are better consistent, so that the correctness of the finite element simulation method is proved, and the high-order acoustic metamaterial low-frequency sound insulation structure provided by the invention has excellent low-frequency sound insulation performance.
Although the embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to the above-described embodiments and application fields, and the above-described embodiments are illustrative, instructive, and not restrictive. The person skilled in the art, in the light of the present description and without departing from the scope of the claims, can also make numerous constructive forms, in particular higher order acoustic metamaterial low frequency sound-insulating structures, which are covered by the present invention.
The foregoing detailed description of the preferred embodiments of the invention has been presented. It should be understood that numerous modifications and variations could be devised by those skilled in the art in light of the present teachings without departing from the inventive concepts. Therefore, the technical solutions available to those skilled in the art through logic analysis, reasoning and limited experiments based on the prior art according to the concept of the present invention should be within the scope of protection defined by the claims.
Claims (8)
1. An N-order acoustic metamaterial low frequency sound insulating structure, the structure comprising:
a plurality of (N-1) -order acoustic metamaterial low-frequency sound insulation structures extending in the x and y directions in an array mode, wherein the acoustic metamaterial low-frequency sound insulation structures are arranged on the upper surface of the base plate;
when N is 2, the second-order acoustic metamaterial low-frequency sound insulation structure comprises a plurality of acoustic metamaterial unit cells which are expanded along the x and y directions in an array mode and a second-order mass block attached to the center of the expansion structure;
when N is 3, the third-order acoustic metamaterial low-frequency sound insulation structure comprises a plurality of second-order acoustic metamaterial low-frequency sound insulation structures which are expanded along the x and y directions in an array mode, a third-order mass attached to the center of the expansion structure and an external frame;
by analogy, when N is larger than 3, the N-order acoustic metamaterial low-frequency sound insulation structure comprises a plurality of (N-1) -order acoustic metamaterial low-frequency sound insulation structures which are expanded along the x and y directions in an array mode, and an N-order mass block and an external frame which are adhered to the center of the (N-1) -order acoustic metamaterial expansion structure; the sound insulation peak generated by the structure is generated by the modal coupling anti-resonance effect of the adjacent-order acoustic metamaterial, and the N-order mass block is used for enhancing the modal coupling anti-resonance effect.
2. The structure of claim 1, wherein the unit cell preferably includes a square support frame having a circular through hole formed therein, a polymer sheet bonded to one side of the unit cell support frame, and a first-order mass bonded to a central position of either side of the polymer sheet.
3. The structure of claim 1, wherein the outer shape of the unit cell support frame is any one of the following shapes: the shape of the through hole in the unit cell is any one of the following shapes: circular, triangular, rectangular, square, regular hexagonal.
4. The structure of claim 1, wherein the polymer sheet is made of any one of the following materials: the unit cell supporting frame and the external frame may be any one of the following materials: FR4 glass fiber, epoxy resin, ABS resin, organic glass, iron and aluminum.
5. The structure of claim 1, wherein a first-order mass is arranged in the center of the high polymer thin plate of the acoustic metamaterial unit cell, a high-order mass is arranged in the center of the high-order acoustic metamaterial, and the first-order mass and the high-order mass can be made of iron, aluminum or nonmetal and are circular, circular or square in cross section.
6. The structure of claim 1, wherein the central mass of the higher order acoustic metamaterial can be placed on a support frame or placed on a unit cell to cover the unit cell, and the central mass of the 4 x 4 higher order acoustic metamaterial is placed on the support frame.
7. The structure of claim 1, wherein the N-1 order acoustic metamaterial is not limited in number by the number of N-1 order acoustic metamaterials contained in the N-order acoustic metamaterial.
8. The structure of claim 1 or 2, wherein the frequency position, sound insulation bandwidth and sound insulation amount of the sound insulation peak can be adjusted by adjusting the structures, material parameters and mass sizes of the Nth-order mass block of the supporting frame and the high polymer thin plate.
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