On the sound radiated by electrical equipment : an active structural acoustic control of harmonic sound

In this paper a technique is presented for the active structural acoustic control of harmonic sound radiated from an electrical machine. In the study, we consider the noise radiated by the heat-exchanger enclosure of a a large size induction motor; the sound is radiated harmonically by the enclosure panels, excited by structure borne vibrations. The control source is a spatially distributed piezoelectric ceramic patch actuator attached to the enclosure panels, and the sensor is a vibration transducer or a microphone. A digital controller and digital processing software are designed based on a feedback algorithm. The paper describes: the functional characteristics of the piezoelectric patch actuators for this application, the finite element model of the enclosure for determining the optimum system configuration, the experimental dynamic analysis to map the panel vibrations, the baseline noise measurements, and the implementation of the control algorithm. Final results are presented showing a 20 dB noise reduction of the harmonic sound radiated from the electrical machine.