Research On Gasoline Engine Noise Source Identification And Sound Quality Improvement

Along with the development of society and the progress of science and technology, people have higher demands for the comfort of vehicle, one of the most important aspect is the problem of noise, vibration and harshness. Engine is the key power of vehicle, and it's also the main source of noise and vibration, therefore, the issue of noise and vibration control has become the focus of research area. At the same time, the study found that when the noise intensity decreased to a certain degree, the subjective feeling for the sound cannot be reflected by the sound pressure level, so it has an important practical meaning for studying the sound quality.In this paper, noise source identification of gasoline engine was studied based on acoustic signal test and analysis. An automotive gasoline engine 2.0DCVVT was taken as a study object, independent component analysis(ICA) was used to blind source separation(BSS) of noise signal and the independent components(ICs) were obtained. Then analyzed each IC time-frequency characteristics, and combined with the structure of gasoline engine and noise generated principle to identify each IC correspond to noise source. Meanwhile, the acoustic array technology was used to take the experiment of noise source identification at a particular frequency, so that it can verify the results of independent component analysis.In order to study the effects of noise source on the sound quality, the typical noise sample was chosen to do the band-stop filter processing, and 8 different samples were obtained. After calculated and compared the coefficient of psychoacoustics parameters and sensory pleasantness, the result can be obtained.In order to investigate effects of the frequency and order distribution on sound quality, the Toyota Corolla gasoline engine was selected to take the contrast noise experiments, the difference of frequency of the two engines can be analyzed. The frequency ranging from 345 Hz to 1250 Hz and 3450 Hz to 6300 Hz were filtered from 2.0D noise samples. After calculated and compared the coefficient of psychoacoustics parameters and sensory pleasantness, the influence of frequency components on sound quality can be obtained. After compared the order distribution of two engines speed up conditions, the influence of order distribution on sound quality can be obtained.Finally, the GT-Power software was used to optimize the intake noise sound quality of 2.0D gasoline engine, after that, the engine intake and exhaust system and the surface radiation noise sound quality simulation and optimization process were established. There is also an innovative idea that to improve the sound quality during the original design stage, and the sound quality development process was established.