Measurements And Analysis Of Indoor Ground-borne Noise Arising From Chengdu Metro

The ground-borne noise caused by indoor vibration of buildings along the metro line is the main environmental problem during the metro operation period,which has aroused people's concern,especially the residents along the metro lines.Based on the research in this field at home and abroad,this paper uses the real-time acquisition and analysis system with multiple channels to perform the synchronization test of indoor vibration and indoor noise in a residential building around the Line 1 of Chengdu Metro.The indoor floor vibration velocity and indoor spatial sound pressure which are collected on different floors are analyzed to obtain the response of indoor vibration and ground-borne noise caused by Chengdu Metro operating.The main works and summary are as follows:1.Reviewed and summarized the research status and methods of the vibration and ground-borne noise in buildings caused by metro at home and abroad.Introduced the evaluation criteria of indoor vibration and ground-borne noise of buildings.2.This paper performs the synchronization test of indoor vibration and indoor noise in a residential building around the Line 1 of Chengdu Metro.According to the comparative analysis results of the measured noise during the passing time and the background noise,and the calculation results of the difference of the C sound level and A sound level,it is believed that the indoor noise of different floors has low-frequency characteristics.The statistical analysis results of the characteristic frequencies of vibration and noise show that the low-frequency noise is the ground-borne noise induced by the vibration of the metro.3.The linear regression equation obtained by fitting the vibration velocity level of indoor floor slabs to the sound pressure level of indoor ground-borne noise is:First floor:L_p,i=L_Vmid,i-?25.2±2.7?;Second floor:L_p,i=L_Vmid,i-?25.6±2.2?;Third floor:L_p,i=L_Vmid,i-?23.7±2.3?.According to HJ453-2018"Technical Guidelines for Environmental Impact Assessment-Urban Rail Transit",the ground-borne noise predicted value can be obtained from formula L_p,i=L_Vmid,i-22.Comparing the measured and predicted results,the prediction formula is applicable to the prediction of ground-borne noise in the first floor and second floor of this paper.4.The indoor floor vibration velocity and indoor spatial sound pressure which are collected on different floors are analyzed in time-histories,spectrum and 1/3octave-spectrum.It is found that the indoor vibration and ground-borne noise of low-rise masonry buildings will be enlarged with the rise of the floor.Using the US FTA manual to evaluate indoor vibration,the results show that the indoor vibration of the third floor exceeded the standard,most of which were near-track train events.Using the JGJ/T170-2009 to evaluate the indoor ground-borne noise,only the indoor ground-borne noise of the third floor exceeded the day limit of the first-class area,and each floor did not exceed the day limit of the second-class areas.Using GB/T 50355-2018 to evaluate the indoor ground-borne noise,it was found that the 63Hz and 250Hz exceeded the standard and the31.5Hz did not exceed the standard.