Research On Subject Evaluation Of The Diesel Engine

With technology development and extended application, diesel automobile grows very quickly in number in recently years. As people pay more attention to energy and environmental problem, and car's noise, vibration and harshness (or NVH) become key factors to evaluate a car's quality. Diesel engine noise is the main source of car's noise, and it is import to analyze and control diesel engine sound quality. The goal is to improve the sound quality, so it is accepted easier by people, less boring than before.Based on latest research result on acoustic subjective evaluation, the essay has done some research work on subjective evaluation of sound quality of the diesel engine noise. First, Subjective evaluation of domestic and foreign research results and methods were analyzed and summarized. Then the theoretical basis of subjective evaluation - the basic concepts of psychoacoustics and subjective evaluation of the need for experimental study problems and the use of experimental methods commonly used in psychoacoustic parameters are briefly introduced. A source of engine noise, a variety of categories and causes of noise are introduced. The experiment of nine-point sound-pressure test was described in detail. Taking diesel engine of three different manufacturers'for the study, three typical conditions were selected of each engine as the test sample of the jury to obtain the data analyzed in paper.Second, the subject evaluation of vehicle exhaust noise is processed by the paired comparison jury test, and the proper psychoacoustic parameters are selected among the all to objectively characterize the sound quality of exhaust noise. The relation between sensory pleasantness and objective parameters is achieved through multiple linear regression analysis. The research indicates that the sharpness is the most important factor of those affecting the perceptions of people to the vehicle exhaust noise and has a negative correlation with the satisfaction.Last, the sound quality prediction model of exhaust noise of the diesel engine is established based on back-propagation neural network. Sensory pleasantness of exhaust noise samples are obtained through the prediction model, and the results are compared with that obtained through multiple linear regression prediction model. The result shows that the prediction values are close to the measured values, the neural network model is more effective than multiple linear regression model in prediction of individual exhaust noise. The neural network prediction model represent the nonlinear relation between sensory pleasantness and objective parameters exactly, can be used for predicting the sound quality of the diesel engine noise.