This paper describes several alternative solutions to the problem of controlling sound transmission through rectangular plates radiating into an enclosed cavity. The specific problem examined is how adaptive filtering compares with feedback control techniques for reducing the level of sinusoidal disturbances transmitted by the plate. In a smart structure with embedded sensors and actuators, it will be likely that feedback control is the preferred option. The feedback controllers examined are LQG/LTR, H∞, internal disturbance model pole placement, and internal disturbance model LQG. These controllers are compared to the filtered-x LMS technique, which is the standard method of dealing with sinusoidal disturbances for this type of problem. All the controllers are examined using simulation and then implemented on a test structure.