Although double-pane windows are being widely used for airborne sound insulation of building facades, they generally have sound insulation deficiencies at low frequencies due to the resonance between two panes coupled by air space. As a method to improve this very serious defect, the application of active control technology has been investigated experimentally. At first, the applicability was examined by scale model experiments in which, by setting a primary noise source in a model room, the possibility of reducing the sound transmitting through a double-pane window was examined by using the usual adaptive active control technique based on the filtered-x LMS algorithm. Regarding the secondary sources, the method using loudspeakers (inside of the source room and in the air space between the double panes) and that using vibration actuators attached on the pane were investigated. As a result, it has been found that the sound insulation deficiencies in the frequency range of the resonance can be recovered by use of the active control. In order to examine the practical applicability of this control method, field experiments were performed by using real buildings.