The engine vibration and noise induced by a valve train element are analyzed through the modeling and experiment method. The valve train dynamics are firstly studied to make clear the sources of the valve train noise. The component flexibility and inertia of mass are all taken into consideration as well as the contact or impact behaviors. The contact or impact forces are applied on the combined model of a combined structure. The resulting vibration responses at the outer surfaces are considered to be the boundary conditions of the acoustic model. The acoustic model is built by the boundary element method. The analysis results show the noise induced by the valve train element is mainly in the 500–800Hz 1/3 octave bands. The noise in this frequency range is related to not only the resonance of oil pan and valve cover but the overall combined structure stiffness. And moreover, the resonance of the valve train element excited by the harmonic of the camshaft rotational frequency has heightened the noise radiation in this frequency range. The noise in the low frequency range is determined by the exciting components of the cam profile, and that in the high frequency range are produced mainly by the valve-seat impact and by the cam-tappet impact. The analysis results are proved well by comparison with the experimental results. Thus the results are very useful for understanding the source characteristics of valve train noise.

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