Piezoelectric-Actuated Vibroacoustic Absorbers for Interior Noise Control

A damped vibroacoustic absorber is fabricated using piezoceramic material as the electromechanical actuator. The absorber consists of a conic piston attached to a system of flexures with surface-bonded piezoceramic material. The absorber is designed to couple the mechanical motion of the acoustic piston to the resonant dynamics of a closed acoustic cavity. Similar to a damped vibration absorber for a mechanical system, the resonance of the vibroacoustic absorber is tuned to the resonance of the closed cavity through proper design of the flexures. A localized model of the absorber coupled to the cavity dynamics is developed using Lagrangian techniques. The model incorporates the electromechanical coupling of the piezoelectric actuators and the impedance of the acoustic load with a mechanical model of the damper-piston arrangement. The model accurately predicts the dynamics of the absorber near the fundamental resonance but modeling errors increase at higher-frequencies because rotational inertia of the piston is neglected. Model-based feedback control laws are designed using full-state feedback and full-order observers. Experimental results demonstrate that closed-loop control of the absorber achieves approximately a 30% reduction in root-mean-square pressure response below the second cavity resonance. Feedback control is robust with respect to errors in the coupled absorber-cavity model, although performance degrades for high-gain feedback control laws. Sound reduction is achieved at multiple locations within the cavity, demonstrating that global noise attenuation is achieved through energy dissipation of the coupled system resonances.