Experimental Study Of The Effect Of The Size Of The Composite Hollow Sound Insulation Specimen On The Noise Reduction Characteristics

With the development of high-speed railway and improvement of train speed,the aerodynamic noise of train has become more and more important issues recently.First,the noise of high-speed trains has seriously affected the passengers comfortable,so that many engineering designers always reduce the aerodynamic noise by board device in the train,which is used for home,commercial and engineering applications due to its unique geometric shape.Second,the noise characteristics of the board noise device are not clear,such as acoustic board materials,multilayer boards and other factors which have a significant impact on noise.Therefore,it is of great value not only to engineering application but also to theoretical research to investigate influence of geometric dimensions on the noise characteristics of the acoustic insulation device.The research object of the present study is soundproof panels of different sizes.The reverberation chamber and an acoustic measuring device are established which is suitable for the acoustic test.The acoustic characteristics of sound insulation specimens with different geometrical structures are measured,and the numerical simulation method is used to calculate the acoustic performance of the sound insulation structure.The influence of the geometrical structure of the acoustic insulation specimen on the sound insulation effect is discussed.Base on the experimental and numerical results,the constant sound pressure level of board is analyzed in the critical condition.In this paper,the reverberation chamber method for acoustic performance test of sound insulation structure is introduced;the advantages and disadvantages of this method and its application are analyzed,which provide the basis for the selection of sound insulation performance measurement method.The size of the sound insulation of each specimen in the frequency range studied is measured.Secondly,the different types of sound insulation specimens are analyzed when the same thickness and area are different,the size of the sound insulation increases with the increase of the area.It is conclude that the area is same and the thickness is different,the sound insulation with the thickness of the increase is also gradually increased.Through the above analysis,the suitable sound insulation of board and the the critical value of sound insulation specimens are clear and definite.At the same time,the numerical simulation of some specimens is carried out by modal analysis in finite element,and the appropriate geometric model is established to calculate the numerical simulation results.According to the results which are compared with the experimental results and the theoretical formulas,it conclude that the calculated results of the theoretical formula are very different from the experimental results,especially in the vicinity of the anastomosis frequency of acoustic structure can only be a preliminary estimate of theacoustic performance.However,the finite element method is in agreement with the experimental results well and is suitable for the acoustic performance simulation of sound insulation structure.Based on the experimental and numerical results,the noise mechanism of the soundproof plate is analyzed.In the low frequency band of the same specimen of the sound insulation changes relatively large,and in the high frequency,the basic showed a linear increase,but the size of the sound insulation changes little with the increasing frequency tend to balance the state.When the specimen area is the same,the thickness increases,the specimen of the sound insulation is also relatively increased.Finally,the sound insulation curve of the specimen is obtained by comparing the weighted sound insulation quantity and the spectrum correction amount Rw + C value of the specimen.