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A shearing motion inevitably occurs along the creep distance on the macroscopic surface of two objects before the friction transformed from static into kinetic state when they come into contact each other. In the process of shearing, it will creep to the characteristic distance before slipping on the supporting surface, then proceed to slip on the contacting points, such an alternating motion between contact surfaces is prone to result in rattling noise. In this paper, the mechanism of the automotive rattling or clicking noise produced in bolted joints surface will be addressed mathematical through the characteristic distance of stick-slip model. Finally, it is suggest that how to prevent these noises in the early design phase.

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To address the rattling noise issue of a Twin-tube hydraulic shock absorber for a electric vehicle, a road test and subjective evaluation were performed. The diagnostic method of the rattling noise source of the shock absorber is studied, and three methods are used to process the test date: the fast Fourier transform can only obtain the main frequency band of the rattling noise; and the short-time Fourier transform can roughly diagnose the frequency band and the occurrence time; using wavelet transform technology combined with displacement signal can accurately lock the source of rattling noise in the rebound stroke. Furthermore, combined with the internal valve configuration of the shock absorber, the rattling noise source is diagnosed in the rebound valve and the compensation valve. The time of rattling noise and the corresponding working stroke of shock absorber can be quickly locked by using the wavelet transform, which is of great significance to solve the problem of shock absorber rattling noise caused by deficiency design of the internal valve architecture of the shock absorber.

Electric power steering (EPS) system is becoming the primary source of Electric Vehicle (EV) noise due to absence of classic power train. The rattle noise produced by EPS, which is easily discernible when driving. Since the conventional subjective evaluation approach makes it difficult to identify the source, it is required to establish an objective way to solve such an issue. In this paper, the principle of multiple coherence method is first addressed analytically, and then is employed to analyze the vibration signal acquisition from EPS different points, meanwhile, combine with in-car sound signal, to accurately identify the specific location.