Research On The Partition Control Of Bus Sound Quality Based On The Masking Effects

In recent years,with the deepening of multi-disciplinary and cross-discipline in the field of vehicle engineering,the masking effect has been introduced and gradually applied to the research of noise,vibration and harshness(NVH)of vehicles.Reasonable use of the masking effect can meet the psychological needs of the drivers and passengers,improve the interior sound quality and the acoustic comfort of the vehicle.This thesis combines the National Natural Science Foundation of China project "Analysis and Evaluation of Car Noise Quality and Research on Adaptive Active Control Method"(51605189),a city bus was taken as the research model.The interior of the experimental vehicle was divided into driving area and passenger area from the perspective of sound function.Some problems in the sound quality control of city bus interior based on the masking effect were studied,including the orthogonal test design,loudspeaker layout scheme and sound quality evaluation test.After processing and analyzing the evaluation results,the difference in the importance of the masking sound emotion type and the masking sound relative to the sound pressure level of the noise environment in the bus were explored as two factors of the orthogonal test under two stable conditions.The differences in the degree of correlation between the subjective and objective evaluation results were also revealed.The aim of this study is to explore the method and research process of city bus sound quality zoning control based on the masking effect.The main research contents of this paper are as follows:First of all,on the basis of the introduction of Chapter 1,the masking effect was introduced as a characteristic of human hearing.The traditional psychoacoustic objective parameters and their calculation models were summarized.After introducing some subjective evaluation methods and subjective evaluation indexes,the choices of this research were introduced.In addition,the information related to the subjective evaluation subject of the driving area and passenger area was given.Secondly,the masking sound environments were designed for the zoning control of the sound quality in the bus.Based on the masking effect,three factors including the working conditions,the emotional type of the masking sound,and the sound pressure level of the masking sound relative to the noise environment in the bus were selected..The emotional classification of the masking sound was studied emphatically.The masking sound emotion classification library was constructed using the Hevner emotion model of semantic similarity.Subsequently,the level values of each factor were designed,and 16 acoustic environments for the sound quality evaluation were obtained after the orthogonal experimental design.Third,the acoustic design software EASE was used to realize the establishment of sound field control model.In order to ensure the good subjective feelings of drivers and passengers while the sound fields of the driving area and the passenger area do not affect each other,the A-weighted total sound pressure level at different measurement points in the city bus sound field was simulated.The non-uniformity of sound field and the acoustic contrast between the bright and dark zone were used and analyzed in detail.The audience areas were also simulated to show the performance of sound quality partition control.The simulation results proved that the uniformity of the vehicle sound field need to be further optimized,and the sound quality partition control of the passenger area also should be improved.Then,through real-vehicle experiments,the A-weighted total sound pressure level of different measuring points was measured,the unevenness of the sound field in the experimental vehicle and the acoustic contrast between the bright and dark zone were calculated,and the audience areas of the sound field in the car were measured and drawn.Analyzing the results of actual measurement and simulation,the validity of model establishment and index calculation under the EASE software environment is verified.On this basis,optimize the design of the loudspeaker layout scheme,which is a key issue in the control of the spatial division of the sound field.Under the optimized layout plan,the sound field in the car is more uniform and the partition effect is more obvious.The sound field optimization effect is more obvious,and it is more suitable for the partition control of the sound quality in the car.Finally,the optimized loudspeaker layout scheme was used to construct 16 bus interior acoustic environments according to the orthogonal experiment design.The objective evaluation tests were completed in a relatively uniform interior sound field.The subjective evaluation tests of the two areas were organized with adopting the comfort as the subjective evaluation index.By processing and analyzing the evaluation results,the difference in the importance of the masking sound emotion type and the masking sound relative to the sound pressure level of the noise environment were explored as two factors of the bus in the orthogonal test under two stable conditions.The differences in the degree of correlation between the subjective and objective evaluation results were also revealed.