CN103594080A - A light-weight low-frequency broadband thin-film metamaterial sound insulation device - Google Patents

Abstract

The invention provides a light low-frequency broadband film metamaterial sound-insulating device which comprises a grating support, a viscoelastic film and a counterweight block; the grid support is made of a rigid light material and is formed by periodically extending square grids along the x direction and the y direction; the viscoelastic film is tightly adhered to the grid support; the balancing weights are respectively arranged on the viscoelastic film in a periodic manner corresponding to the square lattices; the square lattices, the viscoelastic films corresponding to the square lattices and the balancing weights form cells, and the cells are minimum acoustic metamaterial units for blocking low-frequency noise in the sound insulation device. The broadband, namely, the wider frequency range can be covered by the balancing weights with different qualities configured in the adjacent cells; when the metamaterial unit is excited by sound waves, the local resonance phenomenon occurs on the balancing weight and the tensioned viscoelastic film, so that the average displacement of the whole cell is zero, and the sound is effectively blocked.

Description

A light-weight low-frequency broadband thin-film metamaterial sound insulation device

technical field

The invention relates to low-frequency noise blocking technology, in particular to a light-weight low-frequency broadband thin film metamaterial sound insulation device.

Background technique

Since the 1950s, with the rapid development of aerospace, high-speed trains, power transmission and transformation projects, etc., noise problems have become increasingly serious and have attracted widespread attention. In the field of life, noise interferes with people's normal work and life, and long-term exposure to high-noise environments will cause harm to people's health. In the field of production, strong noise will cause the failure or even damage of equipment, resulting in accidents. In the military field, with the development of various weapons and equipment to extreme operating environments such as high-speed, light-weight, large-scale, and heavy-duty, the noise problem caused by it has become more prominent, which has seriously affected the combat and acoustic stealth performance of certain technical weapons, and reduced the equipment battlefield survivability. Therefore, noise control is a very important task in both military and civilian fields.

The traditional sound absorption and isolation technology can effectively isolate the medium and high frequency components in the noise, while the low frequency noise has the characteristics of long transmission distance, strong sound transmission ability, and difficult isolation, which has always been a difficult problem in noise control. The sound insulation of traditional sound insulation materials in the low frequency band is controlled by the law of mass density, and it is difficult to achieve low frequency broadband sound insulation with lightweight materials. Studies have shown that prominent problems of low-frequency noise generally exist in aerospace, high-speed trains, power transmission and transformation engineering and other fields.

Contents of the invention

In order to solve the problems in the prior art, the present invention provides a light-weight low-frequency broadband thin-film metamaterial sound insulation device, which can enable light-weight materials to break through the limitation of the law of mass density and achieve high-efficiency isolation of low-frequency noise.

The present invention is achieved through the following technical solutions:

A light-weight low-frequency broadband film metamaterial sound insulation device, which is composed of a grid support, a viscoelastic film and a counterweight; the grid support is made of rigid and lightweight materials, and is composed of square grids extending in the x direction and the y direction It is formed by periodic extension; the viscoelastic film is tensioned and bonded on the grid support; the counterweights are periodically additionally arranged on the viscoelastic film corresponding to the square grid; the square grid and its corresponding The viscoelastic film and the counterweight constitute the cell, which is the smallest acoustic metamaterial unit that blocks low-frequency noise in the sound insulation device.

Preferably, the sound insulation peak frequency of the cell is positively correlated with the tension of the corresponding viscoelastic film, and negatively correlated with the mass of the corresponding counterweight.

Preferably, the grid support is made of plexiglass or aluminum or aluminum alloy; wherein, the side length of the square grid is 1-5cm, and the wall thickness is 2-8mm.

Preferably, the viscoelastic film is made of silicone rubber.

Preferably, the counterweight is made of magnets or copper, and the counterweight is a symmetrical prism.

Compared with the prior art, the present invention has the following beneficial technical effects:

The light-weight low-frequency broadband thin-film metamaterial sound insulation device of the present invention is composed of several acoustic metamaterial units periodically arranged, and can achieve broadband, that is, a wider frequency range, by configuring counterweights of different masses in adjacent cells. coverage; when the metamaterial unit is excited by sound waves, not only the local resonance phenomenon occurs between the counterweight and the tensioned viscoelastic film, so that the average displacement of the entire unit cell is zero, so as to effectively block the sound, there will also be adjacent The anti-phase vibration of the counterweight and the tensioned viscoelastic film in the cell produces efficient sound insulation at a lower frequency position, thereby achieving noise isolation in a wider frequency range. Not only can it effectively block noise within a certain frequency range, especially low-frequency noise that cannot be isolated using traditional sound insulation materials and technologies, but the sound insulation effect on a wide frequency band can also meet general requirements. The cell as the smallest acoustic metamaterial can generate low-frequency resonance, realize the low-frequency acoustic band gap, effectively block the propagation of low-frequency sound waves, and break through the limitation of the law of mass density.

Furthermore, the effect of the present invention on blocking low-frequency noise is improved by limiting the structure material and size of the cells in the cell; among them, by limiting the material of the grid support, it can be ensured that the grid is square under the premise of ensuring strength. The lattice has a small wall thickness, which reduces the mass of the grill support and the penetration of noise.

Description of drawings

Fig. 1 is a schematic diagram of the overall structure of the sound insulation device of the present invention.

Fig. 2 is a schematic diagram of four cell structures in the center extraction in Fig. 1 .

Fig. 3 is a schematic diagram of the structure of the experimental sample described in the examples of the present invention.

Fig. 4 is a schematic structural diagram of test samples of counterweights of different masses described in the examples of the present invention; a is sample 1, b is sample 2, and c is sample 3.

Figure 5 is a comparison of the acoustic transmission loss curves of the three samples obtained by finite element software simulation.

Fig. 6 is a diagram of the vibration displacement corresponding to the frequency of the sound insulation valley and sound insulation peak in the sound transmission loss curve of sample 1 obtained by finite element software simulation.

Figure 7 shows the acoustic transmission loss curves of the three samples obtained through actual measurement.

In the figure: 1 is a counterweight, 2 is a viscoelastic film, and 3 is a grid support.

Detailed ways

The present invention will be further described in detail below in conjunction with specific embodiments, which are explanations of the present invention rather than limitations.

A light-weight low-frequency broadband film metamaterial sound insulation device of the present invention, as shown in Figure 1 and Figure 2, consists of a grid support 3, a viscoelastic film 2 and a counterweight 1; the grid support 3 consists of a rigid Made of lightweight materials, the square grid is periodically extended along the x direction and the y direction; the viscoelastic film 2 is tensioned and bonded to the grid support 3; the counterweights 1 correspond to the square The grids are periodically additionally arranged on the viscoelastic film 2; the square grids and the corresponding viscoelastic film 2 and the counterweight 1 form a cell, which is the smallest acoustic metamaterial unit for blocking low-frequency noise in the sound insulation device.

Further, the sound insulation peak frequency of the cell is positively correlated with the tension force of the viscoelastic film 2, and negatively correlated with the mass of the counterweight 1; in this preferred example, the grid support 3 is made of plexiglass or aluminum or aluminum alloy; Wherein, the side length of the square grid is 1-5cm, and the wall thickness is 2-8mm; the viscoelastic film 2 is made of silicon rubber; the counterweight 1 is made of magnet or copper, and the counterweight 1 is a symmetrical prism, A cylinder or a cuboid is preferably used.

Specifically, the rigid grid support 3 in the cell mainly plays a supporting role, and has little effect on the sound insulation performance of the entire light-weight low-frequency broadband thin-film metamaterial sound insulation device. Therefore, on the premise of meeting a certain bending stiffness, through Controlling and optimizing its structural parameters can reduce the quality of the grid support, thereby reducing the quality of the entire sound insulation device.

因此，能够通过调整粘弹性薄膜2的张紧力和调整重物的尺寸和材料，控制本发明的隔声峰值频率。粘弹性薄膜2张紧力越大，隔声峰值频率越高，呈正相关；配重块1质量越大，隔声峰值频率越低，呈负相关。The viscoelastic film 2 and the counterweight 1 in each cell can be equivalent to a local resonance structure in which a spring connects a vibrator. Adjusting the tension of the viscoelastic film 2 is similar to changing the elastic coefficient of the spring, and adjusting the size and material of the counterweight 1 is similar to changing the quality of the vibrator. For a local resonant structure composed of a spring with an elastic constant K and a vibrator with a mass m, its resonant frequency is

Therefore, the sound insulation peak frequency of the present invention can be controlled by adjusting the tension of the viscoelastic film 2 and adjusting the size and material of the weight. The greater the tension of the viscoelastic film 2, the higher the peak frequency of sound insulation, showing a positive correlation; the larger the mass of the counterweight 1, the lower the peak frequency of sound insulation, showing a negative correlation.

As shown in Figure 3, it is a sample physical picture of a lightweight low-frequency broadband thin-film metamaterial sound insulation device containing four cells. Preferably, the material of the grid support 3 is aluminum with light density and good processability. Due to the size limitation of the standing wave tube, the overall sample is a short cylinder with a diameter of 100 mm and a thickness of 15 mm. Four rectangular small holes of 20×20mm are processed on the aluminum experimental sample, the wall thickness between the small holes is 4mm, the wall thickness corresponding to the grid support 3 is 4mm, and the side length is 2cm; the viscoelastic film 2 is made of elastic Larger silicone rubber material with higher tear strength, with a thickness of 0.2mm, a density of 1000kg/m ³ , an elastic modulus of 2×107Pa, and a film tension of 0.56×106Pa. The counterweight 1 adopts magnets that can be easily added or subtracted, the radius of which is 2mm, and the mass of each magnet is 0.9g. Adjust the local resonance frequency of the cell by increasing or decreasing the number of magnets.

In order to verify the sound insulation effect of the present invention, a comparative test is therefore carried out, and three kinds of samples as shown in Figure 4 are designed, the structural size, the material, the tension force of the viscoelastic film 2 of the grid support 3 adopted by these three kinds of samples etc. are the same as the above-mentioned samples, but the quality of the counterweight 1 is different. Figure 4a shows sample 1, which contains magnets of two masses, and magnets with masses of 0.18g and 0.27g are respectively placed between adjacent cells, where the magnets of 0.18g are represented by open dots, and the magnets of 0.27g Indicated by a solid circle. Figure 4b shows sample 2, its four cells are all placed with magnets with a mass of 0.18g. Figure 4c shows sample 3, its four cells are all placed with magnets with a mass of 0.27g.

As shown in Fig. 5, the acoustic transmission loss curves of the three samples calculated by the finite element method. It can be seen from Figure 5 that the sound transmission loss curves of samples 2 and 3 have two sound insulation valleys and one sound insulation peak, while the sound transmission loss curve of sample 1 has three sound insulation valleys and two sound insulation peaks. Sample 1 can not only produce a sound-insulating effect in the frequency band where sample 2 and sample 3 have better sound-insulating effects, but also produce a sound-insulating peak at a lower frequency, thereby expanding the sound-insulating properties of the cells described in the present invention. Frequency Range. If there are more kinds of heavy objects, the sound insulation frequency band will inevitably be further broadened, which not only has good targeting, but also can easily adjust the structure to meet a wide range of sound insulation requirements.

As shown in Figure 6, the vibration displacement diagram of the corresponding frequency of the sound insulation valley and sound insulation peak in the sound transmission loss curve of sample 1 calculated by the finite element method shows its good sound insulation effect and wide sound insulation frequency Range, achieve sound insulation over a wide sound insulation frequency band. Figure 6a shows the vibration displacement diagram corresponding to the frequency of the first sound insulation valley. It can be seen that the magnet with a mass of 0.27g vibrates in the same direction as the viscoelastic film 2 of the unit where it is located, while the magnet with a mass of 0.18g and its viscoelastic film 2 The cell's viscoelastic membrane barely vibrates. Figure 6b shows the vibration displacement diagram corresponding to the frequency of the second sound insulation valley. It can be seen that the magnet with a mass of 0.18g vibrates in the same direction as the viscoelastic film 2 of the unit where it is located, while the magnet with a mass of 0.27g and the viscoelastic film 2 of its unit The viscoelastic membrane 2 of the cell hardly vibrates. Figure 6c shows the vibration displacement diagram corresponding to the frequency of the third sound insulation valley. It can be seen that the magnet with a mass of 0.27g and the magnet with a mass of 0.18g hardly participate in the vibration, while the viscoelastic films of the four units move toward the same direction vibration. Figure 6d shows the vibration displacement diagram corresponding to the frequency of the first sound insulation peak. It can be seen that a magnet with a mass of 0.27g and the viscoelastic film of its unit vibrate in one direction, while a magnet with a mass of 0.18g and the viscoelastic film of its unit vibrate The viscoelastic film vibrates in the other direction. Figure 6e shows the vibration displacement diagram corresponding to the frequency of the second sound insulation peak. It can be seen that the magnet with a mass of 0.27g and the magnet with a mass of 0.18g vibrate in one direction, while the viscoelastic film 2 of the four units vibrates in the other direction. Vibrates in one direction.

As shown in Figure 7, it is the acoustic transmission loss curves of the three samples obtained from the experimental measurement. It can be seen that the curves obtained by the experimental measurement are roughly consistent with the curves calculated by the finite element method in Figure 5, and the frequencies corresponding to the sound insulation peaks and sound insulation valleys are also consistent. However, the acoustic transmission loss measured by the experiment is higher than that calculated by the finite element method. This is because the impedance tube is round, and the sample must also be made round, so the four cells are surrounded by 15mm thick aluminum. It has a high sound insulation capacity, so that the overall sound transmission loss is improved. Therefore, the experimental measurement can be replaced by the finite element analysis, and the accuracy is better, the speed is faster, and the cost is saved. The experimental results of the finite element analysis shown in Fig. 5 and Fig. 6 are true and reliable.

Claims (8)

1. A light-weight low-frequency broadband film metamaterial sound insulation device, characterized in that it consists of a grid support (3), a viscoelastic film (2) and a counterweight (1); the grid support (3 ) is made of rigid and lightweight materials, and is formed by periodically extending the square lattice along the x direction and the y direction; the viscoelastic film (2) is tensioned and bonded to the grid support (3); the The counterweights (1) are periodically additionally arranged on the viscoelastic film (2) corresponding to the square grids respectively; the square grids, the corresponding viscoelastic films (2) and the counterweights (1) form a cell, It is the smallest acoustic metamaterial unit that blocks low-frequency noise in sound insulation devices. 2. A light-weight low-frequency broadband thin-film metamaterial sound insulation device according to claim 1, characterized in that the peak frequency of the sound insulation of the cell is positively correlated with the tension of the corresponding viscoelastic film (2), and the corresponding The mass of the counterweight (1) is negatively correlated. 3. A light-weight low-frequency broadband thin-film metamaterial sound insulation device according to claim 1, characterized in that the grid support (3) is made of plexiglass or aluminum or aluminum alloy. 4. A light-weight low-frequency broadband thin-film metamaterial sound insulation device according to claim 1 or 3, wherein the side length of the square grid is 1-5cm. 5. A light-weight low-frequency broadband thin-film metamaterial sound insulation device according to claim 1 or 3, characterized in that, the wall thickness of the square grid is 2-8mm. 6. A light-weight low-frequency broadband film metamaterial sound insulation device according to claim 1 or 2, characterized in that the viscoelastic film (2) is made of silicone rubber. 7. A light-weight low-frequency broadband thin-film metamaterial sound insulation device according to claim 1, characterized in that the weight (1) is made of magnets or copper. 8. A light-weight low-frequency broadband thin-film metamaterial sound insulation device according to claim 1, 2 or 7, characterized in that the weight (1) is a symmetrical prism.

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