Active control of multiple tones in an enclosure

In this paper, analytical and experimental investigations into active contr ol of multiple tones in a three-dimensional enclosure are presented. The fr equency range of the disturbance is chosen to encompass one or more structu ral and/or enclosure resonances. Distributed piezoceramic actuators and dis tributed polyvinylidene fluoride (PVDF) sensors are mounted on one of the e nclosure boundaries. Acoustic sensors are used inside and outside the enclo sure. An analytical formulation based on a state-space model is developed f or local vibration control on an enclosure boundary and/or local noise cont rol inside the enclosure for bandlimited disturbances. The error sensor sig nals are minimized by using digital feedforward control schemes based on fi ltered-U gradient descent algorithms. Analytical predictions from the curre nt work are found to compare well with the results obtained in our previous experimental investigations. The current efforts are relevant to sound fie lds such as those enclosed in rotorcraft cabins. (C) 1999 Acoustical Societ y of America. [S0001-4966(99)03207-5].