Acoustic Insulation Performance Of Composite Thin Film Acoustic Metamaterials

The problem of noise pollution is becoming more and more serious.Because of the long wavelength of low-frequency noise,it is difficult to attenuate the sound wave in the transmission process.At present,low-frequency vibration and noise reduction has become a hot research topic in the field of acoustics.The basic thin film acoustic metamaterial structure is composed of tensional membrane fixed on the supporting frame,which breaks through the restriction of mass density law and has excellent sound insulation performance in low frequency band.In this paper,the low-frequency sound insulation characteristics of thin film structure are studied.The main research contents are as follows:First,the center cross mass block thin film structure was designed,and the 1HZ-1000Hz sound insulation of the structure was calculated by COMSOL finite element simulation software and Matlab program,and the vibration modal analysis was carried out.The formation mechanism of the structure’s sound insulation characteristics was elaborated in detail,and the conclusion was drawn:The acoustical metamaterial structure of thin film can suppress the vibration of thin film successfully by adding a central mass block,so as to improve the sound insulation performance of the structure.Second,an acoustic metamaterial structure with bias triangular blocks is further designed to further move the sound isolation peak to the lower frequency band,while creating the secondary peak and improving the average sound transmission loss.Through the analysis of sound insulation mechanism and vibration mode,it can be seen that the influence of structural parameters on the sound insulation performance of the film structure is as follows:(1)with the increase of the film size,the position of the peak and trough of sound insulation volume gradually moves to the low frequency.(2)Increasing the size of the additional mass block without changing the overall size of the film has no significant improvement effect on sound insulation performance.(3)Improve the tension of the film,so that the sound insulation of the structure moves to high frequency as a whole.(4)The peak value and frequency of structure sound insulation are almost unchanged by increasing the surface density of the film.Thirdly,an acoustic metamaterial structure with piezoelectric film is designed to achieve the tunability of peak sound insulation.Furthermore,a composite film acoustic metamaterial structure was designed by connecting orthogonal ribs to compensate for the TL valley effect as much as possible,thus greatly improving the sound insulation performance of the structure.Fourthly,carbon fiber reinforcement materials are introduced into the designed thin film acoustic metamaterial structure,and Q235 steel is replaced by iron-carbon mixture with 10%carbon content.The new equivalent parameters of the structure are used to obtain the corresponding sound insulation by simulation and calculation.The results show that:By increasing the carbon fiber content of the structure,it is helpful to improve the sound insulation performance of the thin film acoustic metamaterial structure,and opens a new idea for the research of low frequency vibration and noise reduction from the material field.Fifthly,the design of thin film acoustic metamaterial structure specimens was prepared,and the prestige impedance tube was used for sound insulation experimental test.After the experimental data of each group were measured,the experimental results were analyzed.Experimental results are used to verify the simulation values and analytical solutions of the sound insulation of each junction.The results well verify the feasibility of the research contents of the sound insulation performance of each thin film acoustic metamaterial structure.In conclusion,this paper,through the research and design of the structure sound insulation performance of thin film acoustic metamaterial,provides a new idea to realize low frequency,broadband and high sound insulation of thin film structure,and is expected to play a certain role in the research field of low frequency vibration and noise reduction.