Testing the active minimization of the total radiated sound power of a vibrating plate

Abstract

This paper presents an experimental investigation of an Active-Noise-Control (ANC) system for reducing unwanted so-called primary sound by destructive interference with sound generated by so-called secondary sources (loudspeakers). In this work the primary source is a vibrating simply supported plate which is radiating sound into the free field. The loudspeakers are placed in front of the plate. The ANC-system utilizes the measured signals of the primary accelerometers which are placed on the surface of the plate. The number of the primary accelerometers corresponds to the number of the loudspeakers. Also, one secondary accelerometer is fixed onto each loudspeaker cone. Furthermore, a microphone in front of each loudspeaker measures the near field sound pressure. An adaptive feed-forward-controller is used to calculate the optimal control signal for each secondary source. The optimal control is achieved by minimizing the radiated active sound intensity in front of each loudspeaker in order to minimize the total radiated sound power of the primary and secondary sources. The ANC-system is tested in different configurations with one or two loudspeakers in front of the plate. Also, an approach for the system calibration is developed to compensate the phase deviation between the true and the measured sound intensity.