6. Vibro-Acoustic Noise Analysis of a Washing Machine

This study is a comprehensive effort in analyzing the vibro-acoustic characteristics of a top loaded washing machine, and focuses on the identification of the main noise source. For this purpose, the vibro-acoustic behaviors of components in washing machine are investigated systematically. Modal analysis of the main components in the system (cabinet, tub, and motor) are performed for identification of vibration modes that are related to noise radiation. The cogging torque that is associated with the brushless DC motor is identified with the order analysis. The critical frequency bands are determined with respect to components, and preliminary investigation for the noise source identification is concluded. For a quantitative ranking of contributions from several components to output noise during operation of the washing machine, Operational Transfer Path Analysis method is used. The vibration and acoustic response are measured in a relation to stepwise control of the operation speed of the BLDC motor. Transmissibility functions with respect to transfer paths are calculated, and cross-talk cancellation is applied using principal component analysis. The evaluated synthesized response matched well with the measured noise output through all measurement steps.