Analysis Of Vibration And Noise Reduction Characteristics Of Rail Noise Reduction Structure Based On Resonance Principle

With the rapid development of private cars,it has led to a series of problems such as road congestion and environmental pollution.Due to its convenience and large transportation volume,the subway has developed rapidly,while the vibration and noise problems of the subway have attracted more and more attention because they affected the comfort of the passengers.In the speed range of 60~120km/h of subway operation,the main noise source is wheel-rail noise.In the radiated sound power of the whole wheel-rail system,in the frequency range below 2000 Hz,the acoustic radiation of the rail dominates,so it is necessary to control the vibration and noise of the rail.Aiming at a new type of rail vibration and noise reduction structure,this paper analyzes the theory of Helmholtz resonance cavity and dynamic vibration absorber from the viewpoint of resonance sound absorption and resonance absorption,and clarifies the mechanism of structure,the vibration and noise reduction effects has been evaluated.The specific contents are as follows:(1)The research status of vibration and noise reduction technology and resonance structure of metro track system were reviewed.The prospects and research directions of resonant sound absorption and dynamic vibration absorption system in the field of vibration and noise reduction of track were discussed.(2)Based on the finite element method,the vibration analysis model of the ballastless slab track of the subway was established.The effectiveness of the rail vibration model was verified based on the frequency response function of the rail obtained by the hammer stroke test.Based on the boundary element method,the acoustic radiation prediction model of the ballastless slab track of the subway was established.The vibrational radiation characteristics of the rail head,rail waist and rail foot area and the vibrational sound radiation contribution to the whole rail were analyzed.The results show that: under the action of wheel and rail force,the significant frequency band of the rail acoustic radiation is 315Hz~1200Hz,and the rail foot and rail head contribute the most to the rail radiated sound power.(3)Combined with the resonance theory,the influence of the structural parameters and arrangement of the Helmholtz resonator was analyzed by simulation in order to provide theoretical basis for the noise reduction analysis of the resonant sound absorption structure.The results show that when the aspect ratio(diameter-to-height ratio)of the Helmholtz cavity changes around 1,the cube cavity and the cylinder cavity are better than the sphere cavity,and the difference between the square cavity and the cylinder cavity are not obvious.Multiple frequency noises can be reduced in parallel by different volume chambers,and the same volume chamber is used in parallel to increase the noise reduction of the resonator..(4)Based on the analysis results of single cavity resonance and the acoustic vibration model of rail,the effect of adding resonant sound absorption structure on the track noise at the rail waist and rail foot position was analyzed.The results show that it is more effective to add a resonant sound absorbing structure at the rail foot position than to add a resonant sound absorbing structure at the rail waist position.It can reduce the total sound pressure level of the standard field point(7.5m away from the centerline of the track and 1.2m high from the top of the track)by about 3.4dB,which mainly reduces the noise in the frequency range above 400 Hz.(5)A vibrational radiation model of the rail considering the dynamic vibration absorber is established.The natural mode method is used to solve the parameters of the dynamic vibration absorbers with tuning frequency of 220 Hz and 1020 Hz.The control effect of the dynamic vibration absorber on the vibration and noise of the rail was analyzed.The insertion loss of the resonant sound absorbing structure and the dynamic vibration absorber were superimposed to explore the effect of the resonant sound absorbing structure and the dynamic vibration absorber on the rail noise.The research results show that the noise reduction effect of the dynamic vibration absorber on the rail radiation noise is mainly reflected in the frequency range of 160Hz~400Hz and 800Hz~1250Hz.When considering the resonance sound absorption and resonance damping structure,in the case of a mass ratio of 0.1,the total sound pressure level of the rail radiation noise of the standard field point(7.5m away from the centerline of the track and 1.2m high of the top surface of the rail)can be reduced by 7.4dB.