Design And Performance Analysis Of Sound Barrier In Subway Elevated Section

With the rapid development of China's rail transit,China's transportation system has become more and more perfect.The construction of urban rail transit has brought convenience to residents' lives,but it has also caused noise problems.For example,the common subway system will bring greater noise pollution to the surrounding residents in the elevated section,which affects people's daily life.For the problem of noise pollution,the most common treatment method is to establish a sound barrier.The sound barrier commonly used in China is upright and inclined,but the effect is not ideal,especially the problem of low frequency diffraction can not be effectively solved.In this paper,a new sound barrier is proposed based on quadratic residual diffuse sound absorber,acoustic interference theory and micro-perforated sound absorption structure.The large-scale acoustic software LMS Virtual.lab is used to verify the noise reduction characteristics of the designed sound barrier.The specific research contents are as follows:Firstly,the noise characteristics of the subway system rail transit are obtained through the literature survey method,and the noise frequency range and sound source intensity of the study are determined.In LMS.Virtual.Lab,the difference between point source and line source is analyzed and the sound source mode suitable for subway noise analysis is determined.According to Schroeder's quadratic residue diffused sound absorber(QRD)design method,the diffuse sound absorber structure is obtained.Based on the material usage and practical applicability,based on the principle of acoustic interference,a new sound barrier combined with a QRD structure and a tilted sound barrier is designed.In LMS Virtual.lab,a new type of sound barrier,T-type composite QRD type sound barrier and general tilt type sound barrier model were established.Acrylic force was used as the sound barrier material,and the influence of acoustic-vibration coupling was considered to carry out simulation analysis.Considering the difference between low frequency and medium frequency noise,the comparison and evaluation of the three types of sound barriers are divided into two groups,medium frequency and low frequency,in the form of cloud image,which respectively correspond to the performance of the interference structure when verifying the intermediate frequency and the absorption of the QRD structure in the sound barrierat low frequency.The acoustic performance finally leads to the noise reduction performance of the design structure in the mid-frequency range of the subway noise and the low frequency range that is difficult to handle.Then,based on the classical acoustic theory of micro-perforated sound absorber(PMA),the MATLAB software is used to analyze the sound absorption coefficient and semi-sucking sound of the overall structure of the four design parameters of PMA perforation diameter,plate thickness,cavity depth and perforation rate.The effect of bandwidth is obtained by the relationship between the incident noise frequency and the acoustic performance of the microperforated sound absorbing structure.On the basis of theoretical analysis,considering the actual requirements of processing and assembly,determine the more practical PMA parameter range for composite QRD slot hollowing.Then,the seven sets of slots of the QRD structure can be compared with the depth range of the cavity to determine five sets of slots that can be used for the composite microperforated sound absorbing structure.The peak frequency of the mid-band of subway noise is divided into five segments,and the center frequency is taken as the design starting point.In the MATLAB,the multi-objective genetic algorithm is used to obtain five sets of design parameters with better sound absorption coefficient and semi-sucking sound bandwidth.The designed micro-perforated structure is composited to the sound barrier of the previous design,and the noise reduction performance of the composite structure is calculated and analyzed in LMSVirtual.lab.Similarly,the intermediate frequency and low frequency groups are analyzed.The frequency of the sound barrier of the composite PMA and the insertion loss value of the measuring point are analyzed.The noise reduction capability of the composite sound barrier structure in the middle frequency band is obtained,and the low frequency of the final sound barrier combined with the PMA is also tested.Noise reduction.Finally,the assembly column matching the composite sound barrier is designed,and the plug-in type 5 transonic barrier model suitable for the subway elevated section is established by CATIA,and the modal analysis and force research of the assembly structure are carried out in ANSYS Workbench.The self-weight,snow load,wind load and seismic load are combined into two types of working conditions.The displacement and stress distribution of the sound barrier are obtained through the analysis of working conditions,and the mechanical weak points are summarized to provide reference materials for actual assembly.