Research On Influence Of Crowd Characteristics On Environmental Sound Level Of Urban Squares

Urban squares are important parts of urban open space.The urban squares optimize the layout of the urban morphology,improve the quality of life of the citizens,and become important places for people to entertain.Therefore,the sound environment of the urban squares is particularly important.In recent years,great progress has been made in the study of acoustic environment in urban squares,but the important factor of the crowd has rarely been considered.Therefore,this paper studied the crowd characteristics in the squares with different spatial factors,such as regional location,area size and road layout,and emphatically analyzed the impact of these characteristics on the environmental sound level of urban square,through field investigation,objective measurement,software prediction and data analysis.Eight typical urban squares were selected as survey sites,and the research area and time were further determined according to the characteristics of crowd activity in urban squares.Based on that,reasonable measuring instruments were selected to measure the crowd characteristics(crowd size,crowd behavior,crowd distribution)and environmental sound level in urban squares.Meanwhile,the crowd characteristics and environmental sound level in different types of urban squares were summarized.In terms of the impact of crowd characteristics on the environmental sound level,as for the impact of crowd density on the environmental sound level,when the crowd density increment is the same,the increase of sound pressure level in residential square is the largest,reaching 1.6dBA,and the increase of sound pressure level in park square is the smallest,which is 0.4dBA.The large square has the largest increase in that,and the medium square has the smallest increase in sound pressure level.The sound pressure level increment of the double-faced street square and three-faced street square are the largest,and that of the single-faced street square is the smallest.In terms of the influence of crowd behavior on the environmental sound level,in the squares with different regional locations,the difference between the influence of organized behavior and unorganized behavior on the sound pressure level is from large to small: residential squares,park squares and street squares.In the squares with different sizes,the difference between the influence of organized behavior and unorganized behavior on the sound pressure level is from large to small: large squares,medium squares and small squares.In terms of the influence of crowd distribution on the environmental sound level,under the condition of random distribution,the sound pressure level increment of the street square is the largest,while that in residential squares is the smallest.Under the condition of edge distribution,the sound pressure level fluctuation of the small square is the largest,while that of the medium squares is the smallest.Under the condition of multi-concentration point,within the same distance from the sound source,the more squares facing the street,the greater the attenuation of the sound pressure level.Based on the above analysis,the influence of crowd characteristics on the environmental sound level of the urben square was supplemented by Cadna/A.It found that with the increase of population density,the sound pressure level of the urben square increased in a cubic curve.With the increase of the number of organized activity groups,the sound pressure level of the urban square increased gradually,and the sound pressure level increased by 1.42 dBA for each additional group of people.The smaller the crowd distribution range,the higher the local sound pressure level.The sound pressure level of crowd blocky distribution was larger than of crowd strip distribution.This study lays a foundation for the in-depth study of the soundscape of urban open space,provides help for improving the sound environment of urban open space,and broadens ideas of urban open space design for architects,urban planners,landscape designers and so on.