Research On Evaluations Of Sound Sequences In Transport Hub

In recent years,with the rapid population growth and rising living standards,the urban living environment has faced unprecedented pressure and has received increasing attention.Transportation is one of the most important carriers of urban functions.With the rapid development of the economy,transportation has been promoted a transportation hub with much larger scale,more complex functions and more intensive space.Sound environment is one of the most important environmental factors in daily life.Research of the comprehensive sound environment on transportation hub is of great significance for improving the urban living environmentThe transportation hub focuses on the transportation and waiting for crowds,organizing spatial layout and streamlines,integrating multiple functions such as business and catering,which make it extremely particular in function,space and sounds.The study of sound environment in transportation hub is very different from other building types and urban spaces,which involves complex factors.At present,there are many related studies,however,they are relatively scattered.A systematic and complete theoretical framework has not been constructed.Related results are needed to integrate urgently.Based on sound perception mode and many factors integrated,a theoretical framework of sound perception has been established in transportation hub,and concepts of“sound scene" and“sound sequence" have been proposed.Sound scenes have been investigated extensively and objective indicators were extracted and analyzed.Subjective evaluation has been performed,and core indicators for subjective evaluation and prediction models for sound scenes were proposed.Materials of typical sound scenes have been selected,and different sound sequences have been simulated.Basic laws of sound sequences have been revealed,and optimization strategies have been proposed.Sound sequence theory would improve sound environment with a purpose of scientific and economical improvement for transportation hub.It enriches the theoretical system of sound environment and provides a new perspective for variousFirstly,theory framework of sound perception in transport hubs has been constructed based on grounded theory approach.Characteristics of sound environment in transport hub have been analyzed from the perspectives of design,sound source,sound propagation and sound evaluation.Based on data acquisition and codes analysis from grounded theory,seven main factors of sound perception for transport hub are proposed,which are "subjective feelings and needs","behavioral strategies","functional properties","sound scenes",“other objective environmental factors","temporal experience" and "individual differences".Based on those factors,theory framework of sound perception in transport hubs has been constructed.Users can choose to travel or stay in various functional areas through various behavioral strategies based on subjective feelings and needs,and experience a series of acoustic scenes.Based on the effects of other objective environmental factors and individual differences,different subjective feelings and new needs are generated.Accumulating over time,serialized sound experiences have been formed eventually.Different functional areas in transport hub correspond to unique behavior patterns,crowd density,sound source characteristics,and sound propagation characteristics.The unique sound environments in different functional areas are defined as "sound scenes".Sound scenes are the basic units of sound perception in transport hub,rather than spaces.The user passes or stays in various acoustic scenes to form a serialized sound scene experience,and defines it as an“sound sequence".The transport hub has 6 kinds of basic sound sequences,including 30 sound scenes.Secondly,data of sound scenes in transport hubs have been extensively investigated,and objective indicators have been extracted and analyzed.Site selection are based on acoustic scenes,covering various site types and sizes.The original recording data covering all the acoustic scenes have been obtained based on the real traveling streamlines from the user's perspective during the survey,and 676 acoustic scene samples were collected.Combined with human ear hearing effects,the shortcomings of A sound level in evaluation on sound scenes were pointed out in transport hubs.The characteristics of sound quality evaluation methods have been discussed.Psychoacoustic indicators have been introduced,alculated by software of ArtemiS.Statistics of 7 categories of site types,5 categories of site sizes,6 categories of function types,and 30 categories of sound scenes have been made.Sound scenes of 8 objective indicators for characteristics have been summarized in transport hubs,which are A sound level,C sound level,loudness,sharpness,roughness,fluctuation strength,tonality,and articulation.Thirdly,representative sound scene units have been selected for subjective evaluation,the core indicators affecting subjective evaluation have been determined,and prediction models have been established.Duration of 30s as the unified time for sound scene unit,which can satisfy the subjective evaluation of sound scene in traffic hubs.Comprehensively considering the sound pressure level,fluctuation and sound events,209 pieces of representative 30s sound units have been selected,and 8 objective indicators have been calculated respectively,from 676 sound scene samples of different time durations.30 subjects with hearing health have been selected,and acceptance evaluation experiments have been conducted using quantitative classification method.The analysis of variance has been used.It is found that among the four classification,the functional type can only significantly define the subjective evaluation.The analysis of correlation has been used.It is found that there are five indicators affecting subjective evaluation.A sound level,C sound level,loudness,and roughness are significantly negatively correlated with subjective scores,and sharpness is positively correlated with subjective scores.The correlation between sharpness,fluctuation strength,tonality and subjective score is small,and these three indicators can be excluded.A mathematical model for subjective evaluation of sound units has been established through multiple linear regression.C sound level and roughness are two key factors that negatively affect subjective scores.The subjective scores of sound units can be predicted by calculating C sound levels and roughness.Finally,the basic laws of sound sequences have been revealed,and optimization strategies have been discussed through simulation evaluations on different sound sequences.The pilot experiment has been conducted to determine the sound sequence simulation method.209 sound units were divided into three levels of low acceptance,medium acceptance,and high acceptance.Four groups of experiments have been conducted.20 sound units were selected to form one sound sequence for each experiment.In the sequence,each sound unit has been re-evaluated.It is found that the score of any sound sequence will decrease over time,which is the basis law of“attenuation effect" of the sound sequence.Different levels of acceptances lead to greatly different attenuation.Sound sequence adjustment with a high-acceptance unit would change the original attenuation trend,which slows down the attenuation and called it“deceleration effect".The opposite one is“acceleration effect".Sound sequence adjustment with a low acceptance unit would result in a“rebound effect"for scores.Based on these effects,sound sequence optimization strategies have been discussed.Low-acceptance sound sequences should be minimized and controlled within 3min.The medium-acceptance sound sequences are suitable for extensively used in transport hubs,which should be controlled in 5-6min and presented efficiency and economy.High-acceptance sound sequences would also decay over time,which is suitable in 7-8min.In general,the key to sound sequence is to improve richness.It is suggested that duration of the sound sequences would be controlled reasonably at each level and the basic laws of the sound sequences would be used sufficiently,which can improve the sound environment in transport hubs.