An Approch Of Low Noise Design And Experimental Investigations Into Interior Noise Of High Speed Trains

The operational condition of high-speed railway in China is complicated,including the variety of high-speed tracks,the different environment,great change of operation speed,state changing of wheel/rail surface,and long running distance.All the situations mentioned above make the issues of interior noise of high-speed trains more severe.Not only the interior noise of high-speed trains made by China,but also the imported high-speed trains exceeding the noise limitation.From high-speed tains operation in China,the interior noise control depends on the passive noise control method which is problem-based.Although some important achievements have been obtained,this passive noise control method is becoming more and more limited and cannot fundamentally achieve the noise reduction.Moreover,with more and more high-speed railway lines have being built up and more and more high-speed trains have being operated,abnormal interior noise and vibration occurs from time to time.How to quickly respond to and deal with such problems is also a key issue in the ensuring the normal operation and solving the interior noise of high-speed trains.Aiming at the interior noise issues of high-speed trains,this paper conducts a systematic study in the five aspects:(1)SEA prediction model of interior noise,(2)acoustic index design of the key components of carbody,(3)optimal design of sound insulation and vibration reduction of key composite structures,(4)interior noise experiments and low-noise design verification,and(5)treatment method and examples of abnormal interior noise.This paper discusses how to control the interior noise of high-speed trains from problem-based to low-noise design from the initial design stage,and how to identify and deal with abnormal interior noise and vibration happened during the high-speed train operation.An approach of low-noise design for interior noise of high-speed trains is proposed,it includes:(1)acoustic design target of the train,(2)acoustics index design of the components,(3)acoustic simulation of the components,(4)acoustic experiment of the components,(5)noise prediction of the whole train,(6)in situ noise experiment of the whole train,and(7)low-noise design system.In view of the key issues in the low-noise design process and the problems of abnormal interior noise and vibration of high-speed trains,the main research work is carried out as follows:1.Based on the method of Statistical Energy Analysis(SEA),an interior noise simulation model of a high-speed train is established.Modal densities of the structural subsystems are derived from measured frequency response functions using the modal counting method.Damping loss factors of the structural subsystems are obtained using the half-power bandwidth method and the vibration attenuation method,and these of the cavity subsystems are obtained through the sound absorption measurement.Coupling loss factors between structures and cavities are obtained through the structure sound radiation using sound intensity scanning method,and these between cavities and cavities are obtained through the sound insulation measurment.The reliability of the prediction model is verified through in situ experiments.2.A method for acoustics index design of the key components of carbody is proposed.Based on the verified simulation model,the characteristics of subsystems' power flow,the sensitivity of the acoustic parameters on the interior noise and the influence of wheel out-of-round on the interior noise are investigated.The sound insulation index of carbody is designed according to the acoustic design target of the high-speed train.3.In the acoustic laboratory,the sound insulation characteristics of the multi-layer composite structure of the carbody are tested and analyzed.The influence of different combination of the used materials on the sound insulation is studied.Based on the Finite Element and Boundary Element Method(FE-BEM),the sound radiation simulation model of whole floor is established.The influences of the height,elasticity modulus and damping loss factor of the damping pad on the floor sound radiation are investigated.The effect of acoustic design of components is discussed.4.Based on the in situ noise experiments of the high-speed train,the interior noise sources are identified,the contributios of interior noise transfer paths are obtained,the characteristics of the interior noise at different speeds,on slab track or ballast track,and on the ground surface or in a tunnel are investigated,and the relationship between interior noise and vibration is studied.The variation tendencies of wheel out-of-round,bogie area noise and interior noise in a wheel life cycle(about 300 thousand km)are analyzed.5.A method for contribution analysis of the interior airborne sound based on exterior noise source identification and interior sound intensity test is proposed,and the results are discussed.6.A method for identifying abnormal interior noise and vibration in a high speed train is proposed.Using the abnormal interior noises in the coach end and in the tourist cabin as two cases,the experimental analysis and the improved results measured are given out.The research work in this paper helps to realize the interior noise design target of a new high-speed train,the interior noise reduction up to 3-5 dBA of it is achieved,compared to the existing high-speed trains.It can provide a basis for more systematic research on the low-noise design and interior noise control of high-speed trains in future.