InMAR - Intelligent Materials for Active Noise Reduction

During the last decade fundamental research on smart structures using intelligent materials has raised industrial interest. One of the most challenging application field is noise and vibration control. The strongly coupled phenomena vibration and noise limit the design of highly advanced and efficient lightweight structures. To face the challenge European Union has granted funding for the Integrated Project Intelligent Materials for Active Noise Reduction - InMAR as the key European Union funded project in the area of Intelligent Materials within the FP 6. VTT's main focuses in InMAR project are in - developing novel concepts for vibroacoustic properties of light weight composite materials - developing new large surface structural and acoustic sensor-actuator pairs for sound transmission control developing new local feedback control methods, especially for multi-channel active sound transmission loss control - implementing active sound profiling for car interior sound quality control - applying the developed materials, actuators and control methods in passive design, and in active systems in car sound package design and elevator wall sound transmission loss increase. The first realization of novel composite panel concept at VTT is a GFRP panel with striped core made of two different materials. The panel shows up to 10 dB better sound insulation compared to the reference (homogenous stiff core) panel. Two types of polymer material based actuator-sensor elements have been developed together with Panphonics Oy, one for active structural control and the other for active acoustic control of sound transmission loss of panel type structures. Development of multi-channel digitally adjustable analog control system is carried out for the active systems e.g. utilising large surface polymer actuators. The developed FPAA prototype controller contains an FPAA unit board and a microcontroller. The prototype controller system has been tested in active car sound package mock-up with large surface polymer actuator-sensor pair with up to 9 dB improvement in the target frequency band with broadband acoustic excitation. Local feedback control system gives possibilities to tune and increase the sound insulation of the sound package at selected frequencies giving flexibility for the sound insulation design of car sound packages and other panel like structures.