Influencing Factors Of Absorption-type Noise Barrier Insertion Loss

With the rapid development of high-speed railway construction in China,high-speed rail network has been basically formed.In the process of the rapid development,high-speed railway also bring increasing serious noise pollution to the residents along the railway.Thus,the high-speed railway noise pollution has become a problem that urgently need to solve.In the paper,through summarizing the predecessors' research results,the reduced scale model absorption sound barrier was set up in a semi-anechoic chamber,and was test with Header software to study the influencing factors of high-speed railway absorption sound barrier insertion loss.According tothe actual size,structure and materials of high-speed railway sound absorption barrier in China,and the on the basis of contents of the research,the reduced scale model of sound-absorption with different sound-absorbing material thickness,density and acoustic barrier panel opening rates were established in semi-anechoic chamber.Then,software Header was applied to test the sound pressure level before and after the installation of noise barrier in white noise environment.The noise reduction effect of sound absorption barriers was analyzed based on the data analysis.Finally,the effect of sound absorption material thickness,density and acoustic barrier panel opening rate on sound barrier insertion loss was studied.The main contents of the paper are as follows:1.According to the present domestic and foreign relevant literature of high-speed railway sound barrier structure,by combining with the contents of the research and the conditions of the laboratory,noise barrier structure was selected.Next,relevant literature,specifications to determine the test point arrangement and test methods were combined.Finally,the test plan was prepared.2.Several common sound absorption materials for noise barrier at home and abroad were selected for the experiment of sound absorption coefficient.four kinds of sound absorption materials were preliminary selected,namely,superfine glass wool,rock wool,expanded perlite,and foam glass.After analyzing the curve of the absorption coefficient of the four materials,the author finally determined to use superfine glass wool as the sound absorption material of the sound absorption barrier.3.Based on the noise barrier source height diversity of the high-speed railway,five sound sources at different height(0.7m,0.9m,1.1m,1.3m and 1.5m)were placedon the sound absorption barrier model.The noise reduction effect of sound absorption barrier for sound sources at different height was studied.According to the results,under certain noise barrier height,when sound source was lower,noise barrier had better noise reduction effect.After comprehensively considering the possible impact of the reflection of the ground in semi-anechoic chamber,0.7m of sound source height was finally chosen in the paper.4.Based on the above research and analysis,the insertion loss effect of sound absorption barrier under different absorption material thickness density and acoustic panel opening rate was further studied.For the superfine glass,60 mm,80mm and100 mm in thickness,as well as 24kg/m3,32kg/m3 and 48kg/m3 in density,acoustic panel opening rate of 25%,35% and 45% were chosen.According to the research results,when sound barrier was under certain height,with the increase of noise barrier panel opening rate,noise barrier had more and more significant noise reduction effect,explaining that the increase of panel opening rate was conducive to improve the noise reduction effect of noise barrier.At the same time,with the increase of the thickness of core material and the decrease of the density of core material,noise barrier had more and more significant noise reduction effect,suggesting that the increase of core material thickness and the decrease of core material density also was helpful to improve the noise reduction effect of noise barrier.5.Considering sound barrier might affect road side sound field under the conditions of different absorption material thickness,density and acoustic barrier panel opening rate,finally,the effect of sound barrier on road side sound field under the conditions of different absorption material thickness,density and acoustic barrier panel opening rate was analyzed in the paper.The research showed that different sound absorption material thickness,density and acoustic barrier panel opening rate had little impact on the road side noise.