| Noise pollution has become a problem that can not be ignored in the environmentally friendly construction of urban transit.As the key node connecting the urban space and the urban transit network,the station is not only a waiting place for passengers,but also a working area for station staffs,which is important for acoustic environment-friendly construction of urban rail transit.As the most common form of urban transit station,underground station is buried underground deeply,forming a narrow and closed platform space.The train runs directly on the track laid on the station structure when entering and leaving the station.The generated violent noise spreads to the platform area at close range,containing a variety of sound sources.With the effect of reverberation of closed space,the noise cannot be attenuated rapidly,which brings serious noise pollution to the underground platform and seriously affects the comfort of passengers who are waiting on the platform,the physical and mental health of the staff,as well as the intelligibility of the station broadcast voice.Therefore,It is of great significance to study the characteristics of platform sound field and put forward improvement measures to improve the friendliness of platform sound environment.Thus,this thesis was supported by National Key R&D Program Funded Projects(2017YFB1201104-02).Based on vehicle track coupling dynamics,structural dynamics,structural vibration radiation noise theory and physical acoustics theory,the generation mechanism of sound source of underground platform,sound propagation characteristics of platform space,sound field characteristics under the action of multiple sound sources and optimization measures are systematically studied by combining numerical simulation and field test,The specific contents include:(1)The establishment of a multi-source sound field broadband simulation model for underground platforms.Based on vehicle-track coupling dynamics theory,acoustic finite element method,and sound ray tracing method,a broad-band sound field simulation model for underground platform under multi-sound source excitation has been established.The model includes two sub-modules: low-frequency finite element acoustic analysis module and high-frequency geometric acoustic analysis module.The acoustic finite element analysis sub-module includes the station structure sub-model,the soil-boundary sub-model,and structural vibration radiated noise sub-model.In which the sound radiation effect of each structural boundary of the platform was considered in detail.The geometric acoustic analysis module includes acquisition of the sub-sound sources and the geometric acoustic sub model of platform,in which the acoustic effect of each boundary of platform sound cavity was considered in detail.And the sub sound source includes wheel-rail rolling sound source,air conditioning equipment sound source and broadcast sound source.The model can consider the influence of the excitation of multi-sources and underground platform space system on the sound field characteristics in detail,and the fine simulation and analysis of multi-source broadband sound field of underground platform were realized.(2)Experimental study on acoustic field characteristics of underground platformsThe noise characteristics and platform space parameters of 15 different stations were investigated and summarized,and some typical underground platforms were selected to be tested and analyzed detailly.The sound field characteristics of underground platform were analyzed systematically from two aspects: the sound propagation characteristics of the platform space itself and the noise characteristics caused by trains’ operation.The reverberation characteristics of different types of platform space,the sound attenuation characteristics of platform area and the sound insulation performance of different platform doors were obtained by using standard sound source excitation under the nonoperating period of empty field conditions.Based on this,the key acoustic parameters of simulation model were modified.For the platform noise characteristics caused by trains’ operation,the time-space-frequency distribution characteristics of platform noise under different train operation conditions during the operating period of the platform were analyzed,and the control requirements for platform noise have been clarified,and the characteristics of various sound sources and their contributions have been grasped.Finally,the reliability of the simulation model was verified based on the field test data.(3)Research on the sound field distribution law of underground stations under the excitation of typical sound sourcesBased on the established multi-source sound field broad-band simulation model of underground platform,the sound propagation characteristics of platform space were studied from the spatial sound field parameters and the sound propagation characteristics with distance in platform space firstly.And the influence of platform space parameters on the acoustic propagation characteristics in platform space were analyzed systematically,including platform width,platform height and platform door types.Then,taking the wheel-rail sound source generated by train operation in the track area as the input of sound source,the sound field distribution law and propagation characteristics of the platform were studied,and the key influence area of the platform excited by wheel-rail sound source was defined.Finally,the vibration characteristics of the station structure were studied.Combined with the modal characteristics of the platform acoustic cavity,the sound radiated mechanism from platform structure vibration,frequency spectrum characteristics and spatial distribution law were analyzed.(4)Research on the sound field characteristics of underground platform under the excitation of multiple sound sourcesAiming at the acoustic environment of underground platform that containing multinoise sources excitation and broadcast sources excitation,a method for evaluating the quality of the platform acoustic environment was proposed from the perspective of platform personnel comfort and broadcast speech intelligibility.With regards to the excitation of multiple noise sources,the characteristics of platform sound field were studied based on sound quality.And the applicability of sound quality in evaluation of platform multi-source sound field was clarified.The influence of trains’ inbound speed and platform space parameters on platform sound quality was analyzed.In view of the broadcasting conditions,the distribution characteristics of platform speech transmission index were analyzed,the characteristics of platform sound field were analyzed from the perspective of STIPA.And the influence of the change of station passenger flow,the broadcast volume,and the effect of the loudspeaker’s arrangement on the distribution of public address speech transmission index on platform were studied.(5)The multi-objective optimization measures for underground platform sound field were proposedFacing the multi-source sound field environment of underground platforms,taking reverberation time,sound quality and broadcast speech intelligibility as the optimization objectives,the optimization measures for multi-objective control requirements were proposed based on multi-source sound field characteristics.According to the established multi-source broad-band sound field simulation model of the platform,the optimization effects of sound source control measures and propagation path optimization measures on the sound quality of platform were studied.and the optimization effects of spatial acoustic processing measures and architectural form optimization on platform reverberation time,sound quality and broadcast speech intelligibility were studied. |
