In the European Union funded FACTS project the development of Active Noise Control (ANC) systems for vehicles utilising distributed actuators based on ElectroMechanical Film (EMFi) technology was started. EMFi is made of thin (about 0.05 mm) biaxially oriented special plastic compound, the main component being polypropylene. During the manufacturing process the film is ''stretched'' in two directions. Two car demonstrations were built, one for the ''traditional'' active engine order noise control and one for the attenuation of broad band noise radiation of the dash panel, caused by the vibrations of the panel. Results show that noise reduction using membrane mode EMFi actuators is fully effective at higher engine orders (the noise peaks are reduced to background noise level), when the frequencies are above 200 Hz and the noise levels are reasonable (below 80 dB). Also the broad band noise radiation caused by the dash panel vibrations could be attenuated some 5 dB in the frequency range 150 - 300 Hz, but some amplification was present at higher frequencies. As the main conclusion it can be stated that by using flat EMFi panel actuators in active noise reduction systems, totally new approaches can be taken. Large areas can be covered with sound producing panel elements, and the active noise cancellation can be extended to higher frequencies than with dynamic loudspeakers.
Active noise control in cars based on utilising ElectroMechanical Film (EMFi) based actuators
Aktive Schallregelung in Kraftwagen unter Verwendung von Aktoren auf elektromechanischer Filmbasis
2001
6 Seiten, 6 Bilder, 6 Quellen
Conference paper
English
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