The dynamic characteristics of a beam under active control to minimize the coupled sound radiation is investigated. The beam is subjected to a harmonic point force and the resulting radiated field minimized by utilizing a piezoceramic actuator as control input. The error information from the acoustic medium is obtained by placing a single microphone in the acoustic far field. A feedforward control approach is used to derive the optimum control input applied to the actuator. The analysis shows that when the error microphone is placed along a line perpendicular to the radiating surface, the controlled structure has new eigenvalues and eigenfunctions. The controlled system eigenproperties are only a function of the control force location and independent of the disturbance input. A numerical example demonstrates the applicability of the formulation. The numerical results are also corroborated experimentally using a feedforward controller implemented on a TMS320C20 DSP processor.