Active control of transmission loss in tightly damped panels

The transmission of non-deterministic, broadband noise across a panel is co nsidered, An active feedback control solution that improves the transmissio n loss in lightly damped panels is presented. The additional transmission l oss is achieved using accelerometer feedback and point force actuators to r educe the panel vibration at those frequencies that contribute significantl y to the radiated noise. The multivariable controller is designed in the fr equency domain through a sequential loop closure process. An experimental m ethod for determining appropriate panel locations for the sensors and actua tors is developed. Beneficial panel dynamics are utilized during the contro ller design process through the use of non-minimum phase zeros and unstable poles in the controller. The controller design methodology is also verifie d experimentally, The test facility consists of a panel that is coupled to an enclosure containing the noise source. Reductions in the transmitted sou nd pressure level of 14 dB are achieved at the frequencies corresponding to panel vibration modes which efficiently radiate sound. An overall reductio n in transmitted noise of 3.2 dB is achieved over the 10-300 Hz frequency r ange despite the presence of an acoustic mode within the test enclosure. (C ) 2000 Institute of Noise Control Engineering.