Study On Bandgap Characteristics And Noise Reduction Performance Of Phononic Crystal Type Sound Barrier For Rail Transit

China’s rail transit infrastructure has been developed to a great extent,and its operating mileage and train operating speed have reached a new height.Therefore,after the infrastructure construction is completed,China’s rail transit research will focus on the long-term service performance of trains and line foundation as well as environmental pollution prevention and control.With the implementation of the new version of the Noise Pollution Prevention and Control Law in China,higher requirements have been put forward for the noise problem of rail transit,and it is necessary to systematically study the control strategy of rail transit noise at a later stage.As one of the most important noise reduction measures for rail transit,sound barriers are often installed on both sides of the line in noise-sensitive areas to mitigate the impact of major noise such as wheel tracks on the sound environment along the line.However,with the increasing speed of train operation and the requirement for noise environment,it is necessary to further improve the sound insulation performance of sound barriers.As a new type of acoustic metamaterial,phonon crystals can form their unique band gap characteristics according to different periodic arrangements,so they can effectively suppress the propagation of sound waves;if they are applied to rail transit sound barriers,they can be designed according to the spectral characteristics of the main rail transit noise to form a new type of sound barrier that can effectively suppress rail transit noise,which can further effectively improve the sound insulation performance of sound barriers.Based on the bragg band gap theory,this dissertation proposes two types of new two-dimensional phononic crystal sound barriers for rail transit wheel track noise using single hollow steel tube phononic crystal design,and analyzes the energy band characteristics of the design scheme using COMSOL Multiphysics multi-physics coupled finite element software;the sound insulation effect is verified by sound transmission loss.Next,the influence law of scatterer material and size on the sound insulation effect of the design scheme was analyzed.The study shows that the band gap width of two-dimensional phonon crystal type sound barrier is mainly influenced by the changes of its structural parameters,mainly:the larger the radius of the scatterer,i.e.,the larger the filling rate,the better the performance of the energy band structure;when the acoustic impedance of the scatterer material is much larger than that of the air matrix,the total reflection phenomenon will occur when the sound waves are transmitted to the scatterer,and the hollow scatterer structure can be used to save material,at which time the air inside the scatterer cannot respond to the external fluctuations,resulting in the sound waves will not be reflected in the scatterer.In order to save material,a hollow scatterer structure can be used.Secondly,the corresponding open-ended and four-composite phonon crystals are designed in combination with Helmholtz resonators,which form a Helmholtz resonant cavity and produce low frequency absorption resonance,so that the structure can produce a complete band gap with significant attenuation effect at 500Hz.The energy band structure arrangement designed in this dissertation combined with phonon crystal theory can form an efficient barrier to wheel track noise in specific frequency bands;by reasonably designing the arrangement form and geometric parameters of the scatterer,the effective sound insulation in specific multiple frequency bands can be further realized;therefore,applying the scheme proposed in this paper to the sound barrier design can effectively improve the sound insulation performance of the sound barrier,and applying it to the research and development of sound barrier design has Therefore,the application of the proposed scheme to sound barrier design can effectively improve the sound insulation performance,and its application to sound barrier design and development has good potential and feasibility.