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Noise is more and more perceived as an environmental pollutant. This shift in attitude is reflected in stricter legislation and has wide ranging economic consequences. Traditionally, noise was reduced by passive means like mufflers, damping plates, sound absorbing materials, double-glazing windows, noise barriers etc. All these passive means are mostly suitable for high frequencies and have various disadvantages. In the last decade, active control of sound and vibration (at audio frequencies) has emerged as a viable technology to bridge the low-frequency technology gap. The general area considered is broadband noise transmitted to an enclosed area. We are investigating Active Structural Acoustic Control (ASAC) on the enclosure, and Active Noise Control (ANC) in the enclosed space. Our work tries to introduce novel aspects of multivariable control to this field and is focused on two problems. For the ASAC problem we want to develop techniques for the joint design of the ``smart structure'', the placement of the sensors and actuators, and the synthesis of the control law. For ANC we propose to look at the three-dimensional problem with special emphasis on hitherto neglected aspects of feedback control. The work builds on decades of experience at our lab in robust control, system identification and adaptive control and consists of a balance of simulation, theory and experimentation. This project is supported by the ETH Zurich and the EMPA Duebendorf . In collaboration with: Acoustics group of EMPA, the Centre of Structures Technologies at ETH and the University of Newcastle (Australia). |
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