Near-field pressure, intensity, and wave-number distributions for active structural acoustic control of plate radiation: Theoretical analysis

Abstract

This paper presents a theoretical analysis of near-field time-averaged intensity and pressure distributions of actively controlled plate-radiated sound. A harmonic point force was considered as a noise source, and a piezoelectric element bonded to the plate was applied as control actuator. A single microphone that measures sound pressures in the radiated acoustic far field serves as an error sensor. The optimal input voltage to the piezoelectric actuator is obtained by minimizing a quadratic cost function, defined as the mean square of the error sensor signal. The influence of the location of the error microphone on near-field pressure and normal intensity was studied. Fourier transforms in the wave-number domain are also used to study the mechanisms of control. This work provides a better understanding of the behavior inherent in controlling structurally radiated sound using piezoelectric actuators. In particular, an understanding of the near-field behavior under closed loop control is inherent in the design of sensor arrays located near or on the plate surface.