| With the increasing development of social economy,people have higher and higher requirements for the quality of life.The function of automobiles has evolved from the initial ride instrument to part of living space.Therefore,consumers pay more and more attention to the acoustic comfort of the interior environment of the car in addition to the traditional indicators such as power performance and economy,when buying a car,and the acoustic comfort of the interior environment of the car become one of the main reference indicators for car selection.As the evaluation index of interior acoustic environment in the car,the sound quality of the car can be used to guide the acoustic design and optimization of the sound quality of automobile products,so as to improve the acoustic comfort of interior environment and enhance the market competitiveness of the product.At present,more studies have been conducted on the sound quality of the car under steady-state operating conditions in China,and relatively perfect evaluation methods and indicators for the sound quality of the car under steady-state operating conditions have been obtained.However,there is little research on the sound quality of the car under accelerated conditions,and it is still immature.There are frequent acceleration and deceleration working conditions during the driving process due to the traffic situation in China.Therefore,the car sound quality under accelerated conditions is attracting more and more consumers' attention,which needs to be further studied.Combined with the China Automotive Technology and Research Center project called "Research on Sound Quality of Vehicle Interior Noise Under Accelerating Working Conditions ",evaluation mechanism of people's subjective perception on the sound signal in accelerated vehicle is studied.By referring to the domestic and foreign research experience and methods of subjective and objective evaluation of vehicle sound quality in accelerated working conditions,the subjective evaluation of each main sound quality attribute in accelerated working conditions was carried out to achieve the purpose of comprehensive and accurate evaluation of vehicle sound quality in accelerated working conditions,and the research results were used to guide the development of actual vehicles.The main research contents of this paper is as follows:(1)Evaluation of sound quality in vehicle under accelerated conditions.34 representative vehicles of different brands were selected to test and sample the interior noise of the vehicle under accelerating conditions,then,34 sound samples of accelerating conditions were obtained,and the psychoacoustic objective parameters of each sound sample were calculated.A professional jury was organized to subjectively evaluate the sound samples.In order to comprehensively and accurately evaluate the sound quality of interior noise,subjective evaluation uses Semantic Differential method was used to evaluate the eight sound quality attributes of the sound sample.The subjective evaluation results of each subjective evaluator were tested by data inspection,and the unreasonable evaluation results were eliminated to obtain the subjective sound quality score of each sound quality attribute of each sound sample.Factor analysis method was used to analyze the evaluation results of 8 sound quality attributes of sound samples,and comfort feeling factor and dynamic feeling factor were extracted.These two factors contain 92.349% information of the eight sound quality attributes,which can comprehensively and accurately evaluate the sound quality of the vehicle under accelerating conditions.(2)Interior sound quality evaluation model under accelerating conditions.Through correlation analysis and multiple linear regression analysis,mathematical models were established to describe the scores of comfort factor and dynamic factor with psychoacoustic objective parameters.The results show that under accelerating conditions,the comfort factor score of the sound quality in the car is mainly affected by the three psychoacoustic objective parameters of A-weighted sound pressure level,loudness and sharpness.The score of the dynamic factor of the sound quality in the car is mainly affected by the two psychoacoustic objective parameters,loudness and roughness.Then,support vector machine regression is used to establish the SVM prediction models of sound quality comfort factor score and dynamic force factor score,respectively.The SVM model and multiple linear regression model were respectively used to predict the sound quality of test samples,and the prediction results were compared and analyzed.The results show that the prediction accuracy of the multiple linear regression model is poor,the prediction error of the comfort factor score is between-52-18%,and the prediction error of the dynamic factor score is between-56-49%.The support vector machine model can better predict the scores of two common factors,the prediction error of comfort factor score is between-9%-6%,and the prediction error of dynamic factor score is between-10.42% and 10.51%.This shows that the support vector machine algorithm based on statistical learning theory and the principle of minimum structural risk is suitable for solving the small sample nonlinear problem of sound quality evaluation.(3)Comparative analysis of sound quality of test vehicle and benchmark vehicle.The established support vector machine sound quality evaluation model was used to predict the sound quality of the test sample vehicle and the benchmark vehicle,it is found that the test vehicle's dynamic factor score is 3.25 higher than the benchmark vehicle,which was inconsistent with the enterprise's initial goal of emphasizing the sound quality of comfort.By comparing the difference between the order spectrum(ColorMap)of the test sample vehicle and the benchmark vehicle,and by using the digital tracking filter of ArtemiS software to filter the order components which are significantly higher than that of the benchmark vehicle,the psychoacoustic parameters are calculated.It is found that reducing the sound pressure level of the half-order component can reduce the roughness and thus reduce the predictive value of the dynamic factor score,while the predictive value of the comfort factor score has little change.Therefore,the technical route of reducing the score of dynamic factor by reducing the half-order component of the interior noise of the test sample vehicle was determined.(4)Synthesis analysis of interior noise transfer path.Based on transfer path synthesis(TPS)technology,the equivalent model of vehicle noise synthesis is established.The noise source of the model consists of air noise source and structural noise source.Air noise sources include the engine,air intake,left exhaust,right exhaust and tires,Structural noise sources include engine left mount,right mount and rear mount.Simulation analysis is carried out through the established vehicle noise synthesis model,and the results show that the half-order components that have an important influence on the test sample vehicle's dynamic factor score come from the left exhaust port noise source and the right exhaust port noise source.(5)Research on the influence of exhaust manifold structure on interior sound quality.The theoretical analysis and experimental verification of the propagation process of exhaust noise show that the isometric exhaust manifold can reduce the full-order components such as 3st order,5st order and half-order components such as 2.5st order and 3.5st order of exhaust noise.Symmetric isometric exhaust manifold can reduce half-order components 2.5-order,3.5-order of exhaust noise.By replacing the non-isometric exhaust manifold of the original engine with isometric exhaust manifold,the goal of reducing the score of dynamic factor of interior noise under accelerating conditions was achieved.After using the isometric exhaust manifold,the predicted value of the dynamic factor score of the target point noise in the vehicle was reduced by 2.89 levels,which better realized the target of sound quality adjustment proposed by the enterprise. |
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