Prediction On Soundscape In Commercial Pedestrian Streets Based On Acoustic Characteristics Of Crowd

As primary component of urban open space,commercial pedestrian street has been consumer shopping,leisure environment,communication and tourist scenery of important places for residents and visitors,therefore,acoustic environment of commercial pedestrian street is particularly important.In recent years,although series studies on acoustic environment of commercial pedestrian street have made great progress,did not take acoustic characteristics of crowd into account.Therefore,this paper study the influence of acoustic characteristics of crowd on soundscape in commercial pedestrian street,with acoustic characteristics of crowd as a starting point.On investigation and implementation of acoustic characteristics of crowd,this paper selected four typical commercial pedestrian streets as survey sites.Based on dividing them into series survey areas,objective measurement and subjective survey of acoustic characteristics of crowd(including crowd density,the number of people in conversation,proportion of conversation),acoustic environment and acoustic perception(including subjective loudness,acoustic comfort)were carried out in each of the commercial pedestrian street.This paper analyzed the relationship between crowd density and conversation behaviours firstly.Results indicated that there was a positive correlation between the crowd acoustic features and the number of people in the conversation.A nd the crowd acoustic features was negatively correlated with the proportion of the conversation.Secondly,this paper studies the influence of acoustic characteristics of crowd on the acoustic environment,founding that the level of sound pressure in instrument area is higher than that of music area and hawking area,the value is 3.5d BA and 1.9d BA respectively.And in the narrow alley,wide alley and central street,the level of sound pressure increased with crowd density and the number of people in conversation increasing.This study also found that,the rate of sound growth in winter was slower than in summer in commercial pedestrian street.In addition,acoustic characteristics of crowd also influenced subjective loudness and acoustic comfort.Study showed that the subjective loudness of the insrument area is highest,with the value is 3.4.And its acoustic comfort is also highest,with the value is 3.3.It is intresting to note that the relationship between acoustic characteristics of crowd and subjective loudness and acoustic comfort in the sourth commercial pedestrian street taked a linear trend,while they taked a parabolic shape in the north commercial pedestrian street on account of cultural differences in the sourth and north.On the basis of above analysis,this paper established soundscape prediction model of commercial pedestrian street to predict sound environment,subjective loudness and acoustic comfort with LS-SVM algorithm.And the predictive effect of prediction model was verified.After inspection,the prediction model of sound environment,subjective londness and acoustic comfort reached the ideal effect,and the accuracy of commercial pedestrian street was predicted.This study on establishment of soundscape database of commercial pedestrian street,not noly in favour of creating sound environment with commercial atmosphere,but also reduce disturbtion of noise to offer better acoustic experience for users.