Bös J., Mayer D.

Various approaches for active vibration and noise control based on velocity feedback are tested against each other. The test setup consists of several piezoceramic patch actuators that are applied to a thin rectangular aluminum plate, which is inserted in a baffle between two rooms, an electrodynamic shaker, an accelerometer, and some electronic circuitry including bandpass filters and integrators. First of all, the eigenmodes of vibration and the sound radiation behavior of the baffled plate are measured and analyzed using a scanning laser vibrometer and nearfield acoustic holography. Based on the analysis results, optimal positions for the application of four pairs of piezoceramic patches are determined by superposing the plate deflections caused by the first four vibration modes using Matlab. These four actuators, each consisting of a pair of piezo patches, are then actually applied to the aluminum plate at the predetermined locations. By measuring the transfer functions between the patches the excitability and measurability of certain vibration modes is checked. After that, several different active vibration and noise control approaches are tested. These include the narrowband control of different individual modes by using both a SISO and a SIMO method, the broadband control of several modes by using both a SISO and a Multi-SISO method, and the narrowband and broadband control of the sound transmission through the plate. The effects of these control approaches are checked by accelerometer and microphone measurements. The vibration and sound pressure amplitudes at certain modes can be reduced by up to 20 dB, but apparently the two are not strongly coupled due to the sound radiation characteristics of the plate. Unfortunately, the subjectively perceived noise reduction is negligible due to the low sensitivity of the human hearing at low frequencies.