Theoretical Study On Vehicle-induced Vibration Noise Of Rail Transit Sound Barriers

The construction of rail transportation in China has been developed rapidly under the support of the strategy of a strong transportation country,however,the noise problem caused by the operation of trains has become one of the key issues limiting its rapid development.There are many kinds of noise formed during the operation of trains,and in order to reduce the influence of wheel-track noise on the sound environment along the line,the installation of sound barriers on both sides of the line is often used to mitigate,in order to weaken the influence of noise from the propagation path.In engineering practice,upright insert type sound barrier has the advantages of low construction difficulty,good sound insulation effect,easy replacement at a later stage and low manufacturing cost,so upright insert type sound barrier is the most commonly used form of sound barrier for rail transit in China.However,with the increasing speed of rail transit trains and the intensification of wheel-rail interaction,the vibration caused by the trains will be further transmitted to the sound barrier,which will also cause the sound barrier to vibrate and radiate noise to the outside;as a noise reduction measure,the sound barrier becomes one of the sound sources affecting the sound environment of rail transit,so it is necessary to control the sound barrier’s own vibration noise.Therefore,this paper takes the upright insert type sound barrier installed on the elevated line as the research object,adopts the impedance tube transfer function method and the reverberation chamber method to investigate the influence of different filling materials and geometric dimensions of the rail transit sound barrier on the sound absorption and sound insulation performance of the acoustic panel in the calculation frequency band,and determines the parameters related to the sound barrier with good sound insulation performance.Secondly,based on the train-track-bridge interaction theory,the vehicle-induced vibration characteristics of the sound barrier are analyzed as the boundary conditions for the subsequent acoustic analysis of the sound barrier;finally,the vehicle-induced vibration noise characteristics of the sound barrier are further analyzed by using the acoustic indirect boundary element method;and on this basis,noise reduction measures to reduce the noise of the sound barrier itself are studied.The following main conclusions are obtained from the study:(1)In order to ensure the sound insulation performance of upright insert type sound barrier,sound-absorbing rock wool with thickness of 120 mm is suitable as the inner filling sound-absorbing material,and the rectangular openings with 25% aperture rate of the sound barrier panel design can effectively improve its sound absorption and insulation performance.(2)Under the excitation of track unevenness,the car-caused vibration of high-speed railroad vertical sound barrier is mainly in the frequency range of 0-120 Hz,among which the vibration in 20-80 Hz is the most violent,and the vibration sound radiation of the upper side sound-absorbing plate is more significant in the transverse sound field;the car-caused vibration frequency range of urban rail transit vertical sound barrier is 0-120 Hz,and the violent vibration frequency band is 20-45 Hz,and the transparent sound insulation plate is the main contributor of vibration sound radiation in each component.(3)In order to reduce the vehicle-induced vibration noise of the sound barrier itself,transverse ribs are set inside the sound-absorbing panel and the transparent sound insulation panel adopts the design of "twenty" type with ribs,which makes the transverse vibration acceleration of the sound barrier decrease significantly and the linear sound pressure level of the transverse sound field decrease accordingly,which indicates that the above low-noise structure design plays an effective role in suppressing the vehicle-induced vibration noise of the sound barrier.