Study On Noise Characteristics Of Virtual Track Train And Influence Of The Floor On Interior Noise

As an emerging urban rail transportation tool,virtual track trains provide a new solution for the urban public transportation of China,and provide energy-saving,environmentally friendly and smart travel mode for future cities.At present,the noise level,characteristics and mechanism of the inside and outside of the virtual track train are still unclear.In addition,the virtual track train as a new rail transit,the relevant departments have not formulated the interior and external noise standards.Therefore,based on the on-board vibration and noise test data of virtual track train,this thesis studies the evaluation,formation mechanism and control of the noise of the virtual track train.The main work of this thesis is as follows.Firstly,A certain type of virtual track train was used to conduct on-board test.Based on the test data,the characteristics of the noise of the train were analyzed,and then the noise level inside and outside the train was evaluated with reference to the relevant noise limit standards,and recommendations for the noise evaluation of the virtual track train were given.When the virtual track train runs at 52.5 km/h,its maximum interior noise is 69.5 d BA,the minimum is67.5 d BA,and the external noise is 67.8 d BA.When the train is stationary,its maximum interior noise is 62.0 d BA,and the minimum is 57.4 d BA,the external noise is 56.9 d BA.The interior noise of the Mc compartment is greater than the TP compartment.With reference to the related noise standards of domestic and foreign urban rail transit and automobile,the inside and outside noise of the virtual track train is less than their noise limits.It is recommended to refer to the interior and external noise limit standard of urban rail transit vehicles to formulate virtual track train noise limit standard.Secondly,the spectrum characteristics,source distribution characteristics,acoustic vibration transmission characteristics and time-frequency characteristics of the interior noise are analysed,and the formation mechanism of the interior noise is preliminarily defined from the source and path.The frequency band of the significant interior noise is 315～1000 Hz,and the contribution of the interior noise is the largest in 500 Hz frequency band.The interior noise mainly comes from the floor area.There is a tight correlation between interior noise and floor vibration and outside noise,which indicates that interior noise is affected by the sound insulation characteristics of the floor and vibration sound radiation characteristics.In the frequency band of the significant interior noise around 500 Hz,the significant frequency band of floor vibration increases with the increase of speed,which may be caused by rotating parts or structures.Finally,based on the statistical energy analysis method,the vehicle interior noise prediction model is established.Through the analysis,it is determined that the transmitting noise of the floor path to the interior is the airborne sound.The parameters affecting the sound insulation characteristics of the composite floor structure are investigated,and then the optimized plan for the floor is developed.The results show that when the virtual track train runs at 52.5 km/h,the noise energy in the wheel area is significant.The noise in the car mainly comes from the floor area,and the noise contribution rate from the floor area is 63.0 %,of which the contribution rate of air-borne sound is 40.2%,and the contribution rate of structureborne sound is 22.8 %.After optimization,the sound insulation of the floor has increased by4.9 d B.In the 500 Hz peak frequency band,the sound insulation has increased by 5.6 d B.After optimization,the interior noise is reduced by 2.2 d BA,and the noise reduction effect is significant in the range of 630 to 1250 Hz.In the peak frequency band of 500 Hz,the interior noise is reduced by 2.2 d BA.This thesis mainly studies the noise evaluation,mechanism and optimization design of the floor sound insulation of the virtual rail train,and could provide a reference for the vibration and noise reduction of the virtual track train,and for developing the interior and external noise standards of the virtual track train.