Method for optimizing sound insulation performance of multilayer film type acoustic metamaterial based on orthogonal experiment

Abstract

The invention provides a sound insulation performance optimization method of a multilayer film type acoustic metamaterial based on an orthogonal experiment. And a new thought is provided for realizing the design of the low-frequency broadband sound insulation material. Firstly, an MAM unit cell model based on a simplified spider topological structure is designed in combination with an existing polymorphic anti-resonance cooperative type MAM, a three-layer structure is established based on the model, and improvement of the sound insulation index and widening of the sound insulation bandwidth are achieved. Secondly, analyzing the influence of the number of resonators on the sound insulation performance in combination with sound transmission loss (STL), and revealing the sound insulation mechanism through intrinsic modes of different numbers of resonators in combination with the STL. Thirdly, analyzing the sound insulation performance of the structure when the number of the resonators in each layer is different, and screening out the structure with the optimal sound insulation performance; and finally, performing multi-factor analysis on the sound insulation performance by using an orthogonal experiment to obtain an optimal combination of a plurality of parameters, verifying the accuracy, and further optimizing the sound insulation performance.

Description

Technical field:

[0001] The invention belongs to the field of sound insulation and noise reduction of thin film acoustic metamaterials (MAM), and is a method for realizing low-frequency sound insulation by using a thin film structure. Background technology:

[0002] In modern society, noise pollution has become a serious problem, causing multiple negative impacts on people's health and life, especially low- and medium-frequency noise. Although it does not directly damage hearing, it can affect attention and emotions and cause psychological problems. The development of acoustic metamaterials shows a new direction to solve these problems. At present, acoustic metamaterials have adopted a variety of innovative structural designs in terms of sound insulation to achieve efficient isolation and absorption of sound waves of different frequencies, including phononic crystal structure, local resonance structure and micro-perforated structure. The phononic crystal structure is suitable for sound wave control in a specific frequency range, but the manufacturing is complex and the adaptability is poor; the local resonance structure can effectively isolate low-frequency sound waves, which is particularly suitable for application scenarios that require efficient and compact design, but usually requires large mass and precise design; the micro-perforated structure can achieve effective absorption and sound insulation of medium and high frequency sound waves, but the low-frequency sound absorption capacity is poor and requires precise manufacturing and maintenance. In recent years, thin-film acoustic metamaterials (MAMs) with negative mass density have been proposed, which can break the limitation of the mass law, so they have higher sound insulation performance than uniform materials of equal mass, and have the advantages of lightness, miniaturization, wide frequency response range, and high designability. At present, thin-film acoustic metamaterials still face some challenges in sound insulation applications: first, the high loss characteristics of thin-film materials themselves will lead to a decrease in the efficiency of sound energy conversion, limiting their actual performance in sound insulation systems; second, it is still difficult for thin-film acoustic metamaterials to achieve efficient sound insulation in the low-frequency band, mainly due to the huge difference between the size of the metamaterial microstructure and the wavelength of low-frequency sound waves; in addition, in practical applications, a single thin-film acoustic metamaterial is limited by material properties, and multiple units need to be combined to obtain better performance and adapt to a wider range of applications. Therefore, multi-unit MAM design is crucial to the sound insulation performance and application of thin-film acoustic metamaterials. Summary of the invention:

[0003] The present invention proposes a method for optimizing the sound insulation performance of a multilayer membrane acoustic metamaterial based on an orthogonal experiment. This method provides a new idea for the design of low-frequency broadband sound insulation materials. First, combined with the existing multi-state anti-resonance cooperative MAM, a MAM unit cell model based on a simplified spider topology structure was designed. Based on this model, a three-layer structure was established to achieve an increase in sound insulation and a widening of the sound insulation bandwidth. Secondly, the effect of the number of resonators on the sound insulation performance was analyzed in combination with the sound transmission loss (STL), and the sound insulation mechanism was revealed through the eigenmodes of different numbers of resonators combined with STL. Next, the sound insulation performance of the structure was analyzed when the number of resonators in each layer was different, and the structure with the best sound insulation performance was screened out. Finally, an orthogonal experiment was used to perform a multi-factor analysis of the sound insulation performance, and the optimal combination of multiple parameters was obtained, and the accuracy was verified to further optimize the sound insulation performance.

[0004] (1) Multilayer structure design. MAM is a local resonance material. The MAM unit cell model is obtained from a simplified spider topology. The metal resonator and the EVA swing arm are placed on the same side of the PI film, and the film is fixed in the EVA ring frame. The cross swing arm is placed in the center of the film, and a rectangular resonator is attached radially to roughly simulate the shape of a radial spider web. The resonator is attached to the nodes of the PI film to form an overall circumferential arrangement. The cross swing arm divides the film into four sub-regions, and the metal resonator further divides the sub-regions into three film regions: the resonator, the swing arm, and the tail end of the swing arm. Based on this unit cell model, a three-layer structure was established.

[0005] (2) Analysis of the influence of the number of resonators on the sound insulation performance. The sound transmission coefficient τ represents the sound insulation performance of the sound insulation structure. Since the sound transmission coefficient τ is very small, the sound transmission loss (STL) is used to reflect the sound insulation performance of the MAM. The sound transmission loss (STL) curve and vibration mode are obtained through modeling and simulation with finite element software. The influence of the number of resonators in the structure on the sound insulation performance is analyzed by combining the sound transmission loss (STL). Through the eigenmodes of different numbers of resonators, its sound insulation mechanism is revealed.

[0006] (3) Structural optimization. The number of resonators in each layer of the structure is changed, and the changes in the sound transmission loss curve are analyzed. In combination with the situation where a lighter design is required in practice, the influence of the cavity parameters of the overall structure on the sound insulation performance is analyzed to select the structure with the best sound insulation performance.

[0007] (4) Orthogonal experiment optimization. Orthogonal tests were conducted on factors that had a significant impact on sound insulation performance. The relative bandwidth was determined as a test index by selecting a value greater than 30 dB near the STL peak. A suitable orthogonal table was selected for the experiment to obtain the optimal result. The sound transmission loss (STL) curve was calculated using finite element software to verify the accuracy of the orthogonal experiment. Description of the drawings:

[0008] Figure 1 A simplified MAM unit cell structure diagram based on spider web topology;

[0009] Figure 2 Simulation structure diagram (a) M4 and N444, (b) M0 and N000, (c) M2 and N222;

[0010] Figure 3 Transfer model diagram (a) theoretical simplified model diagram (b) actual structure model diagram;

[0011] Figure 4 STL comparison of single-layer and triple-layer MAMs (a) M4 and N444, (b) M0 and N000, (c) M2 and N222;

[0012] Figure 5 Vibration shape diagrams (a) M0, (b) M2, (c) M4;

[0013] Figure 6 (a) Different simulation structure diagrams, (b) STL comparison diagram of N000, N004 and N044, (c) STL comparison diagram of N022, N024 and N044, (d) STL comparison diagram of different cavity thicknesses;

[0014] Figure 7 STL comparison chart of the optimal combination and the N024 combination. Specific implementation method:

[0015] In order to better understand the technical content of the present invention, specific embodiments are given and described as follows in conjunction with the accompanying drawings.

[0016] A method for optimizing the sound insulation performance of a multilayer membrane acoustic metamaterial based on an orthogonal experiment, characterized in that it comprises the following steps.

[0017] S1 designs a multilayer MAM structure. MAM is a local resonance material. The MAM unit cell model is obtained from a simplified spider topology. The metal resonator and the EVA swing arm are placed on the same side of the PI film, and the film is fixed in the EVA ring frame. The cross swing arm is placed in the center of the film, and a rectangular resonator is attached radially to roughly simulate the shape of a radial spider web. The resonator is attached to the nodes of the PI film to form an overall circumferential arrangement. The cross swing arm divides the film into four sub-regions, and the metal resonator further divides the sub-regions into three film regions: the resonator, the swing arm, and the tail end of the swing arm. Based on this unit cell model, a three-layer structure was established.

[0018] S2 Analysis of the influence of the number of resonators on sound insulation performance. In order to generate more anti-resonance modes and ensure lightweight as the starting point of design, the study is carried out from the perspective of reducing the number of resonators. The mass of the resonator affects the equivalent mass of the MAM vibration system, thereby affecting the natural frequency of the system vibration. Therefore, reducing the number of resonators can generate anti-resonance modes at different frequency points. In order to make the film appear symmetrical anti-phase vibration displacement, the number of resonators can only be 0, 2, or 4. Combined with the sound transmission loss (STL), the influence of different numbers of resonators on the sound insulation performance is analyzed, and the sound insulation mechanism is revealed through the eigenmodes of different numbers of resonators.

[0019] S3 structural optimization. Through the sound insulation performance analysis of the three-layer MAM, it is necessary to explore the impact of changes in each layer of structure on the overall sound insulation performance, analyze the impact of the cavity parameters of the overall structure on the sound insulation performance, and select the structure with the best sound insulation performance.

[0020] S4 Orthogonal experiment optimization. Different structural parameters have an impact on the sound insulation performance of the overall structure. Orthogonal tests are conducted on factors that have a greater impact on the sound insulation performance. The relative bandwidth is determined as a test indicator by selecting a value greater than 30dB near the STL peak. A suitable orthogonal table is selected for the experiment to obtain the optimal result. The sound transmission loss (STL) curve is calculated using finite element software to verify the accuracy of the orthogonal experiment.

[0021] Figure 1 The simplified MAM unit cell structure diagram based on the spider web topology. The metal resonator and the EVA swing arm are placed on the same side of the PI film, and the film is fixed in the EVA ring frame. In order to match the characteristics of the spider web, the film is simulated as a spider web. In the entire structure, in the MAM unit cell, the cross swing arm is placed in the center of the film, and a rectangular resonator is attached radially to roughly simulate the radial spider web shape. The resonator is attached to the node of the PI film to form an overall circular arrangement. The cross swing arm divides the film into four sub-regions, and the metal resonator further divides the sub-regions into three film regions, namely the resonator, the swing arm, and the tail end of the swing arm. The spider web structure divides the MAM unit cell into twelve symmetrically distributed sub-unit cells, and the material parameters of the sub-unit cells show staggered properties.

[0022] Figure 2 Figure 2 is a simulation structure diagram. (a)-(c) are simulation structure diagrams of M4 and N444, M0 and N000, and M2 and N222, respectively. Based on the designed MAM unit cell, a tubular EVA frame is used and the membrane is fixed inside the tube. The resonator and the cross-shaped swing arm are connected to the same side of the PI membrane. In this configuration, the entire structure can be regarded as three MAM unit cells with two cavities sandwiched between the MAM units. Cavity (H c) is set to 25mm, and the total height of the structure is 65mm. The simulation model includes a solid domain and a pressure acoustic domain. In the solid domain, the frame and membrane are surrounded by fixed boundaries to simulate the overall sound insulation performance under fixed constraints, and the initial prestress in the membrane is 1MPa. The loss factor of the PI film is calculated to improve the accuracy. Both ends of the pressure acoustic domain are set to plane wave radiation. The upper surface is used as the sound wave entrance, and the amplitude of the vertically incident plane wave is 1Pa. The lower surface is used as the sound wave exit with a non-reflecting boundary.

[0023] Figure 3 The figure is a transfer model diagram. The structure is composed of a variety of different materials, and there are cavities between the layers. The acoustic impedance of the air in the cavity is significantly different from that of the simplified structure. In the theoretical analysis, the characteristic impedance of the structure is assumed to be constant, which can simplify the analysis. When the sound wave is incident, the theoretical simplified model is as follows Figure 3 As shown in (a), the actual transmission mode of the model is Figure 3 (b) shows that mediums I and III represent air, while medium II represents the effective structure.

[0024] Figure 4 The STL comparison of single-layer and three-layer MAM. STL is used as the evaluation standard for sound insulation performance. Figure 4 (a) shows the STL of N444. The sound insulation bandwidth of N444 is 120-860Hz, and the peak STL at 460Hz is 104dB. Compared with the single-layer MAM unit M4, the low-frequency sound insulation performance of N444 in the range of 330-810Hz is significantly improved. The overall trend of the STL of N444 is consistent with that of M4, with minimal differences in valley and peak frequencies and sound insulation bandwidth. However, when sound waves pass through the three-layer MAM of N444, especially at the peak frequency, the sound energy is effectively offset and transmitted, resulting in an exponential increase in the sound insulation peak. 4(b) and Figure 4 (c) shows the STL of the N000 and N22 structures, respectively. The sound insulation bandwidth of N000 is 260-620Hz, and the peak STL at a frequency of 580Hz is 48.5dB. The sound insulation bandwidth of N222 is 130-600Hz, and the peak STL at a frequency of 340Hz is 86.1dB. It is observed that increasing the number of resonators can expand the sound insulation bandwidth and increase the peak STL. However, similar to the comparison between M4 and N444, in N000 and N222, the peak STL at the frequency point doubles, while the sound insulation bandwidth remains essentially unchanged, and no new anti-resonance modes are generated.

[0025] Figure 5(a)-(c) are vibration mode diagrams of M0, M2 and M4, respectively. For M0, at 273 Hz, the whole is in a coupled resonance mode, the vibration direction is in the same direction as the incident sound wave, and the sound transmission coefficient is the largest. For M2 at 131 Hz and M4 at 122 Hz, the whole is in a coupled resonance mode, the vibration direction is in the same direction as the incident sound wave, and the sound transmission coefficient is the largest. For M0, the membrane exhibits symmetrical anti-phase vibration displacements near 570 Hz, and the incident sound energy is offset by the local resonance of the membrane, resulting in the maximum STL value. For M2 at 351 Hz and M4 at 483 Hz, the membrane near the resonator exhibits symmetrical anti-phase vibration displacements, and the entire unit cell is in a quasi-dynamic equilibrium state, resulting in the maximum STL value. For M0 at 639 Hz, the vibration direction of most areas of the film is in the same direction as the incident sound wave, and the sound energy is offset by a small part of the reverse sound wave, forming a trough. For M2 at 618 Hz and M4 at 917 Hz, the film region without resonator vibrates in phase, the resonator vibration amplitude is small, and a large amount of sound energy is gathered and transmitted from the film region to form a trough.

[0026] Figure 6 (a) is a diagram of different simulation structures, with different numbers of resonators placed on each layer for study. Figure 6 (b) STL comparison diagram of N000, N004 and N044. It can be seen that compared with N000, N004 exhibits a new STL peak in the frequency range of 200-550Hz, and a peak of 37.7dB in the frequency range of 460Hz. This peak corresponds to the resonant frequency of the M4 structure, indicating that it originates from the anti-resonance behavior of the M4 structure. Compared with N004, the peak STL of N044 in the frequency range of 170-560Hz is 68.4dB at a frequency of 450Hz. This confirms the emergence of a new anti-resonance mode in N044. The generation of the two STL peaks is attributed to the anti-resonance behavior of the M0 and M4 structures, respectively. Under the coupled vibration of the two structures, the overall STL is enhanced. Figure 6(c) STL comparison diagram of N022, N024 and N044. Based on N044, N022 and N024 were compared. N022 showed a new STL peak in the frequency range of 280-480Hz, with a peak of 59.1dB at 350Hz. This peak corresponds to the resonant frequency of the M2 structure. N024 showed multiple anti-resonance modes in the frequency range of 300-800Hz, with three STL peaks. Compared with N022, N024 showed better sound insulation performance after 380Hz. Compared with N044, N024 showed higher sound insulation performance before 380Hz. Although the sound insulation peak of N024 at 380Hz is not as high as that of N044, the sound insulation level of N024 still meets the application requirements, and it is also lighter. Therefore, with the goal of generating more anti-resonance modes and ensuring lightweight design, the N024 structure is considered to be the best choice. The STL of three-layer MAM is the result of coupling of different structures, and the order of each layer does not affect the overall sound insulation performance. Figure 6 (d) STL comparison of different cavity thicknesses, with cavity thicknesses of 15 mm, 25 mm, and 35 mm. When the cavity thickness increases, the sound insulation performance in the entire frequency range improves, while the overall bandwidth remains relatively unchanged. Therefore, increasing the cavity thickness can further enhance the dissipation of sound energy and improve the overall sound insulation performance.

[0027] Figure 7 The STL comparison diagram of the optimal combination and the N024 combination. In the frequency range of 461.1-1038.5Hz, the STL value of the optimal combination is always higher than that of the combination 024, and the sound insulation bandwidth of more than 30dB is significantly increased. The results show that through orthogonal experiments, MAM can be analyzed by multiple factors, thereby optimizing and improving the structure of STL and widening the sound insulation bandwidth.

Claims

1. A method for optimizing the sound insulation performance of a multilayer membrane acoustic metamaterial based on an orthogonal experiment, characterized in that: The following steps are involved: Step 1: Design a multi-layer MAM unit structure and set various physical parameters; Step 2: Use finite element software to perform modeling and simulation to obtain the sound transmission loss and analyze the effect of the number of resonators on the sound insulation performance; Step 3: Optimize the multi-layer structure based on actual conditions; Step 4: Improve the sound insulation performance of the structure by conducting orthogonal experiments on factors that have a greater impact on the sound insulation performance.

2. The method for optimizing the sound insulation performance of a multilayer membrane acoustic metamaterial based on an orthogonal experiment according to claim 1, characterized in that: In Step 1, the MAM unit cell model is obtained from the simplified spider topology. The metal resonator and the EVA swing arm are placed on the same side of the PI film, and the film is fixed in the EVA ring frame. The cross swing arm is placed in the center of the film, and a rectangular resonator is attached radially to roughly simulate the radial spider web shape. The resonator is attached to the nodes of the PI film to form an overall circumferential arrangement. The cross swing arm divides the film into four sub-regions, and the metal resonator further divides the sub-regions into three film regions: the resonator, the swing arm, and the tail end of the swing arm.

3. The method for optimizing the sound insulation performance of a multilayer film-type acoustic metamaterial based on an orthogonal experiment according to claim 1, characterized in that: In Step 2, in order to generate more anti-resonance modes and ensure lightweight as the starting point of the design, research is conducted from the perspective of reducing the number of resonators. The mass of the resonator affects the equivalent mass of the MAM vibration system, thereby affecting the natural frequency of the system vibration. Therefore, reducing the number of resonators can generate anti-resonance modes at different frequency points. The number of resonators is 0, 2, and 4. The effect of different numbers of resonators on the sound insulation performance is analyzed in combination with the sound transmission loss. The sound insulation mechanism is revealed through the eigenmodes of different numbers of resonators.

4. The method for optimizing the sound insulation performance of a multilayer film-type acoustic metamaterial based on an orthogonal experiment according to claim 1 is characterized in that: In Step 3, through the analysis of the sound insulation performance of the three-layer MAM, it is necessary to explore the impact of changes in each layer of structure on the overall sound insulation performance, and analyze the impact of the cavity parameters of the overall structure on the sound insulation performance, and select the structure with the best sound insulation performance.

5. The method for optimizing the sound insulation performance of a multilayer film-type acoustic metamaterial based on an orthogonal experiment according to claim 1, characterized in that: In Step 4, different structural parameters have an impact on the sound insulation performance of the overall structure. Orthogonal tests are carried out on factors that have a greater impact on the sound insulation performance. The relative bandwidth is determined as a test indicator by selecting a value greater than 30dB near the STL peak. A suitable orthogonal table is selected for the experiment to obtain the optimal result. The sound transmission loss curve is calculated using finite element software to verify the accuracy of the orthogonal experiment.

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