In this paper, active control of harmonic sound transmitted through a soft-core sandwich panel into a rectangular enclosure is studied. As it has already been shown for the low frequency region, the noise transmission through a soft-core sandwich panel mainly occurs due to the flexural and the dilatational modes. Therefore, in this study, volume velocity cancellation control strategy is used to control these modes, and achieve sound attenuation in a broad frequency range. Point force and uniformly distributed force actuators are used as the secondary actuator to cancel the volume velocity of the bottom faceplate, which opens to the cavity, of the sandwich panel. Cancelling the net volume velocity of the bottom faceplate is compared not only in terms of the reduction in sound transmission through the sandwich panel into cavity but also in terms of the faceplate velocities. Also, the effectiveness of the volume velocity cancellation strategy has been studied for different values of isotropic loss factor of the core. Sound transmission into the cavity has also been calculated by considering the effect of cavity pressure on the sandwich panel. Numerical studies indicate that the active control method controls both the flexural and the dilatational modes of the sandwich panel and therefore, attenuates significant amount of sound pressure inside the cavity irrespective of the isotropic loss factors of the viscoelastic core in a broad frequency range. Also a finite element study has been done in the commercially available COMSOL Multiphysics software to compare with the analytical results.