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This paper examines the onset of brake noise and the mechanisms involved during the initial stages of noise occurrence. The emphasis is directed towards disc mode coupling and improvements are suggested to inhibit the coupling of the in-plane and out-of-plane modes with similar frequencies. To better understand the mechanisms, modal analysis of the system is carried out in a static condition but with varying pressure loads. In addition the operational deflection shape (ODS) was recorded under normal braking conditions using tri axial accelerometers attached on a disc. It was identified by a 3D scanning technique during squeal braking. Through a parametric study and using complex eigenvalue analysis the disc mode shapes were reproduced and correlated to the system results. The proposals to reduce mode coupling were successfully evaluated on a brake dynamometer and the results were confirmed with vehicle testing.

Creep-groan noise is a low frequency noise less than 1000Hz and occurs when the vehicle is moving from stop or slowly stopping while the brake is applied at low brake pressure. The vibration source causing the sound is commonly thought to result from friction force variation in stick-slip phenomenon between friction material and disc. In the past, studies have been mainly focused on stick-slip. However, systematic approach involving chassis components has been recently investigated. In this paper, using a chassis dynamometer creep groan noise was reproduced. Through vibration measurements and modal impact tests, the effects of the vehicle system on creep noise were analyzed.