Fault feature extraction of gearbox by using overcomplete rational dilation discrete wavelet transform on signals measured from vibration sensors

► Time-frequency characteristics of ORDWT are compared with that of DWT. ► Applicability of the flexible ORDWT in fault feature extraction is investigated. ► An ORDWT based impulse extraction method is presented and successfully applied. ► ORDWT and Hilbert transform are combined to study AF/FM effects in signals. ► An ORDWT based denoising method is used to reveal transients masked in noises.