Influence Of Mesoscale Urban Morphology On The Spatial Noise Attenuation Of Departure Flight Trajectories

With the improvement of air transportation system in China,the air volume has increased rapidly.At the same time,the city is rapidly expanding to the suburbs in a high-density develop-ment mode,and the airport and the living environment are getting closer and closer.The aircraft noise generated by the departure flight trajectories is of high intensity with a wide range of pollu-tion,which seriously affects the health and well-being of nearby residents.At present,the relevant researches on aircraft noise are mainly at the macro scale,and there is a lack of studies on urban regional morphology and aircraft noise that consider architectural attributes at the mesoscale.The current state of the urban morphological structure in the area surrounding the airport also remains to be clarified.Based on satellite images,this paper used blocks as the basic unit to count the proportion of Class I and Class II land that were sensitive and less sensitive to aircraft noise around Hangzhou Xiaoshan Airport’s arrival and departure trajectories,as well as the urban morphology and struc-tural characteristics of 119 Class I land blocks.It is found that more than half of areas are sensitive to noise,and the spatial form changes from extensive land use to high-rise,high-density and inten-sive.The measured data of aircraft noise shows that residents in noise-sensitive areas are greatly affected.This paper simulated and calculated the noise generated by the standard departure track of B737-800 aircraft in 20 high-density urban sample areas of 500 m×500 m,and compared the noise distribution of tracks at different angles,horizontal distances and heights above the ground,and analyzed the relationship between 7 urban morphological parameters and aircraft space noise attenuation.The results show that:there are urban areas that are sensitive to the track angle,and the background noise of the aircraft is relatively lower when the angle between the main facade of the building and the track is within 15°,and the background noise can be effectively reduced by more than 3 d BA when it is parallel to the track;only when the horizontal distance from the flight trajectories is more than 600 m can the aircraft noise be effectively reduced by staying away from the noise source;the high-density urban form structure has a significant impact on aircraft noise attenuation;the Complete Aspect Ratio(CAR)is the main urban morphological parameter that affects the aircraft noise in quiet areas,and an increase of 0.6 can effectively improve the acoustic environment;the Average Height of Buildings(AV G＿H)has a significant impact on the minimum value of aircraft noise,the optimal value is 25 m;the joint effect of the remaining parameters is that the higher the plane complexity is,the better the attenuation effect of the median and average aircraft noise.In order to improve the aircraft noise environment in urban space,the following optimization design strategies are proposed: higher average building height,higher building density and the CAR is larger when the single building plane scale is smaller,higher morphological irregularity of single building,more compact and diverse overall layout,aircraft noise attenuation better.