Analytical and experimental studies undertaken for controlling noise in the interior of a three-dimensional enclosure with a flexible wall are presented. The rigid walls are constructed from acrylic material, and the flexible wall, which is clamped along all four edges, is constructed from aluminium material. Noise generated by an external speaker is transmitted into the enclosure through the flexible boundary and active control is realized by using lead zirconate titanate (PZT) piezoelectric actuators bonded to the flexible boundary. Condenser microphones are used for noise measurements. For harmonic external disturbances, optimization analyses are carried out in the frequency domain to determine the optimal voltage inputs to the piezoelectric actuators for global and local noise control. In the associated experiments, analog feedforward control is implemented by using acoustic error signals for different panel and cavity controlled modes.

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Analytical and experimental studies undertaken for controlling noise in the interior of a three-dimensional enclosure with a flexible boundary are presented. The rigid boundaries are constructed from acrylic material, and the flexible boundary is constructed from aluminum material. Noise generated by an external speaker is transmitted into the enclosure through the flexible boundary and active control is realized by using Lead Zirconate Titanate (PZT) piezoelectric actuators bonded to the flexible boundary. Condenser microphones are used for noise measurements. For panel and cavity controlled modes, analog controllers based on feedforward schemes using acoustic error signals are developed and discussed.

In this paper, analytical and experimental investigations into active control of multiple tones in a three-dimensional enclosure are presented. The frequency range of the disturbance is chosen to encompass one or more structural and/or enclosure resonances. Distributed piezoceramic actuators and distributed polyvinylidene fluoride (PVDF) sensors are mounted on one of the enclosure boundaries. Acoustic sensors are used inside and outside the enclosure. An analytical formulation based on a state-space model is developed for local vibration control on an enclosure boundary and/or local noise control inside the enclosure for bandlimited disturbances. The error sensor signals are minimized by using digital feedforward control schemes based on filtered-U gradient descent algorithms. Analytical predictions from the current work are found to compare well with the results obtained in our previous experimental investigations. The current efforts are relevant to sound fields such as those enclosed in rotorcraft cabins.