Research On Perception And Mitigation Of Secondary Radiated Noise From Subway Upper Cover From The Perspective Of Soundscape

With the booming development of subway transportation,the problem of secondary radiation noise in buildings caused by it has become increasingly serious.Due to the fact that relevant standards are still not perfect,traditional vibration reduction and noise reduction methods based on objective acoustic parameters not only have high costs but also are difficult to meet people’s subjective comfort requirements for indoor sound environment.Therefore,this paper starts from the perspective of soundscape,selects the Zhongcun section of Guangzhou Metro Line 22,and studies the problem of secondary radiation noise in the subway upper cover.First,the secondary radiation noise caused by the subway was analyzed and experimentally measured through on-site measurements,and the value range of various objective parameters affecting the secondary radiation noise was determined.An indoor soundscape system was also constructed.Then,through an auralization experiment,the three main components of the indoor soundscape of the subway overlying buildings were identified as annoyance,spatial characteristic perception,and stability.The coverage rate of the three main components for all index parameters reached 53.76%.The analysis and evaluation of the indoor soundscape of the subway overlying buildings are generally applicable.Subsequently,through experiments,the correlation between the driving speed of the train,the sound pressure level increment of secondary radiation noise,room reverberation time,different living scenarios,and individual differences and the main components were further explored.Based on the control equation,the optimal value range of some objective parameters was given.It was suggested that the driving speed should be above 140km/h,and the Aweighted sound pressure level increment when the train passes by should be below 8d B(A).Additionally,the relationship between the average reverberation time of the 50 Hz and 200 Hz frequency bands of the room and the main components was clear.The portrait of sensitive groups was also determined through a questionnaire.Finally,based on the above research results and specific cases,a relief method and optimization process for the secondary radiation noise of subway overlying buildings were proposed from the perspectives of noise reduction design and characteristic sound source design.The feasibility of the optimization measures was verified through comparative experiments.It was found that after introducing the characteristic sound source for optimization,the annoyance of the indoor soundscape of the subway overlying building in the Zhongcun section of Guangzhou Metro Line 22 decreased by 34%,the stability of the soundscape increased by 23%,and the spatial characteristic perception caused by the subway passing by decreased by 33%.This indicates that even without changing the sound pressure level of secondary radiation noise,significant improvement in the indoor soundscape experience can be achieved by introducing the above optimization methods.