Measurement and analysis of a horizontal-axis washing machine for low-frequency abnormal noise

The distinct noise of a horizontal-axis washing machine is analysed through the method of spectrum and correlation analysis. A measurement setup is designed to build a three input-single output system. The sound pressure in a standard location as the output, and the sound pressures near drum bearings and near the motor and the acceleration on the drum as three inputs are measured, respectively. The spectral and coherence results show that the puzzled abnormal noise is mainly in low frequencies below 225Hz, and that the harmonics of drum base frequency from the second to the fifteen are presented in the A-weighted sound auto-spectrum in the loading condition. It is concluded that there should be problems of bearings or of misalignment and clearance in the shafting and the drum bearing should be a main noise source for the washing machine. The study in the paper is helpful for the noise reduction of the washing machine and the method proposed is useful for the noise analysis and the identification of the noise sources.