The characteristic identification of disc brake squeal based on ensemble empirical mode decomposition

Disc brake squeal, which is considered as a self-excited vibration induced by friction force, has received much attention over decades due to the high customer requirements of the NVH properties of vehicles. This paper presents a characteristic identifying method for the disc brake squeal by analysing the acoustic brake squeal signal obtained from experiment. The sound of brake squeal was recorded with a sound level meter to obtain the acoustic signal that later is examined by implementing several different signal processing methods. Firstly, the Fast Fourier Transform and the Short-Time Fourier Transform are performed to illustrate the frequency components of the signal and their evolution with time. Later, the acoustic signal is analyzed using ensemble empirical mode decomposition (EEMD) which is improved from empirical mode decomposition (EMD) by adding white noises of finite amplitude to the original acoustic signal to alleviate mode mixing problem occurred in EMD. After the implementation of EEMD, the original signal is decomposed into several intrinsic mode functions (IMFs). Finally, the Hilbert Transform is conducted for revealing the detailed information about the frequency and amplitude features of each calculated IMF.