Sound power emission of a washing-machine cabinet

Abstract

The noise emitted by a washing machine can be divided into airborne noise produced mainly by the electric motor, and structural-borne noise caused by the cabinet vibration. The aim of this work is to determine the contribution of the structural radiation of the cabinet to the total sound power emitted by a washing machine, and to know which element is the noisiest. The total sound power was measured according to ISO 3744, and in order to know which panel of the cabinet is the noisiest, the standard ISO TR 7849 was applied. This experimental procedure relates the noise radiated by a structure with its vibration velocity, and it was found that the front and lateral left panels were the most relevant. Once the noise transmission paths were characterized, the proposal to reduce noise was focused on reducing the excitation force transmitted by the shock absorbers. As the modification of the force applied by the shock absorber is initially not feasible because it would imply changing the dynamic of the oscillating group, as a first step the panels which support these elements were modified to make them more flexible. A sound power reduction of about 5 dBA was obtained.