[0028]In order to enable those skilled in the art to better understand the solutions of this application, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are only It is a part of the embodiments of this application, but not all the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of this application.
[0029]For ease of understanding, please refer toFigure 1 ~ Figure 3 , An acoustic metamaterial for blocking low-frequency noise in substations provided by this application, including a substrate 1;
[0030]The substrate 1 is filled with a structural unit a2 and a structural unit b3. The structural unit a2 includes a liquid ball 21 with bubbles 20 inside, and the structural unit b3 includes a metal ball 30 and a hard silicone rubber 31 covering the metal ball 30.
[0031]It should be noted that when the incident sound field is smaller than the scattered sound field caused by the scattering of the material structure, the unit volume change is opposite to the dynamic sound pressure change, that is, when the unit volume becomes smaller, the dynamic sound pressure increases or when the unit volume becomes larger, the dynamic sound pressure The reduction causes the material to have a negative equivalent modulus. Specifically for the structural unit a2 in this embodiment, when the incident sound field is smaller than the scattered sound field caused by the scattering of the material structure, the sound field energy in the structural unit a2 is concentrated in The inside of the bubble 20 produces a lower acoustic energy transmittance, that is, a certain band gap is generated at the low frequency, so as to block low frequency noise.
[0032]In addition, for the structural unit b3, in the local resonance phononic crystal theory, the metal ball 30 acts as a mass, and the hard silicone rubber 31 plays an elastic role, combining the metal ball 30 and the hard silicone rubber 31 in a structure When the sound wave passes through the structural unit b3, the sound wave energy is transferred to the metal ball 30, so that the metal ball 30 generates kinetic energy. When the dipole resonance frequency in the structural unit b3 is consistent with the sound wave frequency, the metal ball 30 in the structural unit b3 The direction of motion is opposite to the direction of excitation, resulting in a negative equivalent mass density effect. At the same time, the energy transferred by the sound wave is converted into the kinetic energy of the metal ball. After the energy is consumed, the sound wave cannot continue to propagate forward. Therefore, it passes through the metal ball. 30 motion can absorb the energy transmitted by sound waves, that is, a band gap is produced at low frequencies.
[0033]Therefore, in this embodiment, through the reasonable design of the structural unit a2 and the structural unit b3, the acoustic metamaterial has a negative equivalent mass density and a negative equivalent bulk modulus in the same frequency band, and can produce a band gap at low frequencies. The propagation of noise is double-blocked or the propagation path of low-frequency noise is changed, thereby improving the blocking effect of low-frequency noise.
[0034]The above is an embodiment of an acoustic metamaterial for blocking low-frequency noise in a substation provided by this application, and the following is another embodiment of an acoustic metamaterial for blocking low-frequency noise in a substation provided by this application.
[0035]For easy understanding, please refer toFigure 1 ~ Figure 3 , An acoustic metamaterial for blocking low-frequency noise in substations provided by this application includes a substrate 1;
[0036]The substrate 1 is filled with a structural unit a2 and a structural unit b3. The structural unit a22 includes a liquid ball 21 with bubbles 20 inside, and the structural unit b3 includes a metal ball 30 and a hard silicone rubber 31 covering the metal ball 30.
[0037]Among them, the base material 1 is made of soft silicon rubber, epoxy resin, sponge or foam.
[0038]It is understandable that the substrate 1 can also be made of other soft materials, and at the same time, the structure and shape of the substrate 1 are not limited.
[0039]Wherein, the bubble 20 is filled with air or nitrogen or hydrogen, and the liquid in the liquid ball 21 is water or silicon oil.
[0040]Wherein, the liquid ball 21 is wrapped with a film 22, and the film 22 is made of gelatin.
[0041]Among them, the diameter of the liquid ball 21 is 3-10 mm, the diameter of the bubble 20 is 1-3 mm, and the thickness of the film 22 is 30-100 um.
[0042]Among them, the metal ball 30 is an iron ball or a copper ball.
[0043]Among them, the diameter of the metal ball 30 is 1 to 3 mm, and the diameter of the metal ball 30 after being coated with the hard silicone rubber 31 is 3 to 10 mm.
[0044]Among them, the structural unit a2 and the structural unit b3 are both several, and the filling rate of the structural unit a2 and the structural unit b3 is 10%-50%.
[0045]Among them, such asimage 3 As shown, the structural unit a2 and the structural unit b3 are alternately distributed in the body center or face center of the cubic lattice of the substrate 1.
[0046] It is understandable that the structural unit a2 and the structural unit b3 are arranged in a cubic lattice body-centered or face-centered staggered distribution, and the structural unit a2 and the structural unit b3 can be arranged and distributed periodically to form a generalized phononic crystal. Sub-crystals can produce multiple scattering effects, that is, when sound waves pass through the phononic crystal, multiple scattering effects occur. The sound waves are continuously reflected, and the reflected sound waves interfere, and the energy of the sound waves will be greatly consumed due to the interference. The sound velocity of substrate 1 is determined by the material of substrate 1. According to the principle of Bragg scattering, the center frequency f of the lowest acoustic band gap of the phononic crystal can be determined by the substrate sound velocity c and the lattice constant a, that is, the center frequency f=c/ 2a. Therefore, different lattice constants can be determined according to the pre-obtained main frequency ranges of different noise environments to achieve the best effect of blocking low-frequency noise.
[0047]The following is a detailed description of an example in this embodiment.
[0048]Such asimage 3 As shown, an acoustic metamaterial for blocking low-frequency noise in substations provided in this example includes a base material 1; the base material 1 is filled with structural units a2 and b3, and structural unit a2 includes a liquid with bubbles 20 inside. Ball 21, structural unit b3 includes metal ball 30 and hard silicone rubber 31 covering metal ball 30, structural unit a2 and structural unit b3 are alternately distributed in the body center or face center of the cubic lattice of substrate 1, and the filling rate is 30 %.
[0049]Among them, the base material 1 is made of soft silicone rubber, the gas in the structural unit a2 is hydrogen, the liquid in the liquid ball 21 is water, the diameter of the liquid ball 21 is 5 mm, and the diameter of the bubble 20 is 2 mm; the metal ball 30 in the structural unit b3 It is a copper ball, the diameter of the copper ball is 2mm, and the diameter of the copper ball after being covered by the hard silicone rubber 31 is 5mm.
[0050]The multiple scattering theory (MST) method is used to calculate the energy band structure of the acoustic metamaterial, such asFigure 4 As shown, where the frequency unit is 2πvt/a, vt is the shear wave velocity in the material, and a is the lattice constant of the cubic lattice, fromFigure 4 It can be seen that there is a forbidden band between the normalized frequency of 0.4 to 0.5, which makes it difficult for the sound corresponding to the frequency to pass through the forbidden band when the normalized frequency is 0.4 to 0.5, making the acoustic metamaterial have Good blocking effect of low frequency noise, and the lattice constant a value of the cubic lattice can be set through different noise environments.
[0051]In addition, the three models of structural unit a2, structural unit b3, and structural unit a2 + structural unit b3 in this example are calculated for theoretical sound absorption coefficient, such asFigure 5 Shown. FromFigure 5 It can be seen that the structural unit a2 has a good sound absorption coefficient in the frequency range of 550 to 800 Hz (the sound absorption coefficient is 0.7 to 0.8), and the functional structure b has a good sound absorption coefficient (the sound absorption coefficient) in the frequency range of 300 to 600 Hz. It is 0.6~0.7). When the entire material structure includes a combination of functional structure a + functional structure b, compared with the above two models, there is a better sound absorption coefficient in the frequency range of 300 to 800 Hz (the sound absorption coefficient is 0.8 to 0.98). , The sound absorption coefficient corresponding to a frequency of 550 Hz is close to 1, reaching the highest. This shows that the noise reduction effect at a frequency of 550 Hz is very good. It can be seen that the structural unit a2 and the structural unit b3 have good sound absorption coefficients in their respective ranges, and when a certain range of the two is combined, the sound absorption coefficient is significantly better than that produced when the two are alone. The barrier effect.
[0052]The above is another embodiment of an acoustic metamaterial for blocking low-frequency noise in a substation provided by this application, and the following is an embodiment of a method for manufacturing an acoustic metamaterial for blocking low-frequency noise in a substation.
[0053]For easy understanding, please refer toFigure 6 This application provides a method for manufacturing an acoustic metamaterial for blocking low-frequency noise in a substation. The acoustic metamaterial for blocking low-frequency noise in a substation based on the above embodiment includes the following steps:
[0054]Step 1: Enter the aqueous solution mixed with magnesium powder into the hopper of the dripping machine, add the gelatin slurry to the glue hopper of the dripping machine, and keep it at a constant temperature; put the cooling liquid into the soft capsule container, and then pass the drip first The machine drops the gelatin slurry onto the cooling liquid to diffuse and cool to form a rubber skin, and then drops the aqueous solution mixed with magnesium powder onto the rubber skin through the drip machine, so that the rubber skin sinks. After standing, the rubber skin is completely wrapped Aqueous solution mixed with magnesium powder to form pellets with spherical structure and cool the pellets to form soft capsules; then, the pellets are dried at room temperature, washed with petroleum ether, and then passed through 95% ethanol After washing, place it in an environment with a temperature of 30-35°C for drying, so that the magnesium powder reacts with the aqueous solution to generate gas, and is wrapped in the capsule, thereby obtaining the structural unit a;
