Low Frequency Noise Reduction Technology Based On Membrane Type Acoustic Meta-material

For a long time, due to the particularity of the wavelength of low frequency noise, using common sound insulation material is difficult to achieve a satisfactory isolation effect. The appearance of membrane type acoustic meta-material, makes up the defects of traditional liner material in insulating low frequency noise, membrane type acoustic meta-material shows a good performance in low frequency noise insolation. the membrane type acoustic meta-material, which based on the principle of local resonance, has become a major development trend of reducing low-frequency noise in the field of meta-material application. In order to promote the practical process of membrane type acoustic meta-material, this paper systematically studies the theoretical basis and mechanism of the membrane type acoustic meta-material, as a new kind of meta-materials, in the field of low frequency noise insolation. The specific content of the work are as follows:Firstly, this paper analyzed the reflection, transmission and absorption coefficient of the sound waves in a surface of the insulation structure, defined the basic method of sound insulation material analysis, and gives the evaluation index of sound insulation performance. Based on the energy theory of structure mechanics to predict the energy distribution of the membrane structure, which is on a deformed state, provides a theoretical basis for the analysis and simulation of acoustic absorption type meta-material absorption mechanism.Secondly, The theoretical model of acoustic absorption type meta-material has been analyzed. Based on the fundamental analysis of sound insulation material, using the finite element method(FEM) and finite element analysis software COMSOL, building a sound-solid coupling model for membrane type meta-material. Using this model, the sound insulation effect of sound reflection type membrane meta-material at different frequencies(100Hz~1000Hz) has been analyzed, which proves the superiority of the low-frequency noise acoustic meta-materials. We further analyze the sound absorption mechanism of sound absorption type meta-material, and calculate the vibration displacement and energy distribution of sound absorption type meta-material, which verify the validity theoretical prediction.Then, Based on sound-solid coupling model, the influence of structural parameters of meta-materials design on meta-material absorption coefficient was studied. By improving the quality of the block structure and the optimal selection, improved materials for low-frequency noise absorption effect overall. And through the analysis of two-layer meta-material structures, demonstrate that using two-layer membrane-type acoustic meta-material can reduce the average sound transmission coefficient of the low frequency noise(20Hz~600Hz) to less than 0.05.Finally, physical sample of meta-material is made. Based on wave tube measurement method, building an experimental platform, The sample’s low frequency noise effect is tested under the platform, experimental results and finite element analysis results are in good agreement, proved the correctness of finite element analysis and experimental methods. The experimental results show that the decibel noise of the acoustic meta-material sample can achieve 38 dB at the 414 Hz, which prove the effectiveness of the acoustic meta-material in the field of low frequency noise reduction.