| Vehicle accelerating noise is one of the important performance indexes,with the development of the market,the requirement of automobile enterprises and customers for interior noise has gradually developed from “quiet” to “quality”.Powerfulness Sound Quality is a kind of feeling preference for accelerating noise,which is necessary to be enhanced for sporty vehicles.The main contributing sources of acceleration noise are intake,exhaust and engine noise,after the latter two kinds of noise are effectively controlled,the interior sound quality can be improved by optimizing the intake system.However,the evaluation method and design goal of powerfulness sound quality are not obvious,and the forward design of improving the in-car powerfulness sound quality through the intake system is still not perfect,thus unable to guide the vehicle design.In this disseration,the intake noise of an independent brand vechile is taken as the research object,aiming at realizing the forward design of the “powerfulness” sound quality in the accelerated condition.The research is carried out from two aspects: subjective and objective analysis of interior sound quality and optimization of intake system structure.Completed a set of work including evaluation index,target limitation,software development,simulation model,scheme design,test method and sample validation,etc.Including:(1)A time-varying unsteady noise evaluation method that suitable for vehicle acceleration noise is studied.In order to reflect the connotation of auditory perception of accelerating noise,a semantic space of “powerfulness” is established.Expert consultation and principal component analysis are used to reduce the dimension of semantics subdivision space to stimulation,richness and stability.A method for continuous evaluation of predefined categories is proposed to improve the accuracy of subjective evaluation of accelerating noise,which could reflect the jury differences and Time-varying unsteady characteristics of noise samples.The above research constituted a subjective evaluation method for time-varying unsteady noise.A sound sample library including research and competitve vehicles is established,the validity of the subjective evaluation method for time-varying unsteady noise is verified by the subjective evaluation and data test under three subjective evaluation indexes.(2)A set of objective evaluation parameters associated with powerfulness sound quality is studied.Evaluation index which includes time-frequency characteristics,psychoacoustics and comprehensive parameters is proposed.These include: order distribution,frequency balance,linearity,loudness,sharpness,roughness,fluctuation,boom index,modulation index and order attenuation rate.Through subjective audition and theoretical analysis and comparison,two evaluation indices of “order harmonic degree” and “order contribution” are proposed to reveal the influence mechanism of order and frequency components on sound quality.Compile psychoacoustic parameter computing program and other parameter calculating codes to calculate the objective parameters of 24 groups of sound samples.Using correlation analysis and cluster analysis,it is cleared that each subjective index is related to different objective evaluation indexes.All objective evaluation indexes of accelerated noise can be clustered into energy ratios of 2,4 and 6 Order sound pressure-to-total sound pressure and the sound pressure ratios between low-frequency Bark bands.(3)The interval intuitionistic fuzzy comprehensive ranking method for accelerated noise is studied,and the target value of "dynamic sense" sound quality is proposed.Using Fuzzy Clustering Method to Determine the Weight Distribution of Speed and Subjective Evaluation Index in Accelerating Noise Subjective Evaluation.The interval intuitionistic fuzzy information ranking method is used to evaluate and rank the accelerating sound samples comprehensively.The ranking of accelerated noise is more accurate than the ordinary average method.The “order decompositionsynthesis software” is compiled to decompose,modulate and subjective evaluate the order and frequency components of sound samples,and two kinds of powerful sound quality spectrum characteristic targets are formulated based on the support vector machine model: the “dominant order relay” and the “characteristic frequency retention”.(4)A forward design method for improving the powerful sound quality through the design of intake system is studied.A method that extract the characteristics of engine sound source by using four-load method and calculate the transient condition of nozzle noise by combining the acoustic transfer vector of intake system.The accuracy of the simulation method is compared with test and traditional simulation methods.Through orthogonal analysis,the structural parameters sensitive to nozzle and order noise are determined to improve the structural design efficiency.New acoustic units such as micro-perforated silencing structure,parallel resonator with the same crosssection and intake sound generating unit are used to control sound quality.(5)The test method of intake noise in the dimension of sound quality and the influence of intake noise on vehicle interior noise are studied.The contribution level of intake noise to vehicle interior noise is measured and analyzed by the operating transfer path method.A test bench for vehicle intake noise is built,and a modified calculation method for intake noise is proposed to extract pure intake noise.The results show that the intake noise is strongly correlated with the characteristics of vehicle interior noise.The intake noise is a high quality source of powerful sound quality in vehicle acceleration conditions.Two kinds of noise spectrum are realized by designing intake system.The subjective evaluation results of the vehicle studied are raised from 5.1 points before optimization to 6.4 points and 6.6 points respectively.The results show that the theory and method of sound quality of intake system developed in this dissertation are reasonable,effective and correct. |
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