Considerations on the reduction of structure-borne sound radiation using passive and semi-active treatments and active structural actuators and sensors

Control of structure-borne sound radiation utilising "intelligent materials" is one research topic in EUfunded Integrated Project "Intelligent Materials for Active Noise Reduction" (InMAR). The most obvious method is to damp resonant modes of a structure using passive treatments. More complex methods include treatments with semi-active materials like shape memory alloys, and using active structural actuators like piezoelectric patches to damp the vibration of the structure. If the intention is to control only the sound radiation from the structure (so called Active Structural Acoustic Control, ASAC), more effort must be placed on the identification of modes, which are good sound radiators instead of damping all modes. Also structural sensors are often used as it is a wish to predict the sound radiation from the structure using sensors fixed on the structure itself. In this paper an outline is given of the work done in InMAR Work Area for actuators and sensors (WA 1.2) coordinated by Technical Research Centre of Finland (VTT). Work is mostly oriented for developing different structural actuators to control actively the sound radiation from vibrating structures along with structural sensors for sound radiation prediction. Actuators for high temperature applications are being developed, and investigations on transparent actuator-sensor systems performed. Basic principles of actuator and sensor systems to be developed mainly for plate-like structures will be described and some modelling results are presented.