Active control of sound transmission through soft-cored sandwich panels using volume velocity cancellation

Abstract

In this paper, the active control of harmonic sound transmitted through soft-cored sandwich panels into a rectangular enclosure is studied. As it has already been shown that in the low frequency region, the noise transmission through soft-cored sandwich panels mainly occurs due to flexural and dilatational modes [Rimas Vaicaitis, NASA Technical Note, NASA TN D-8516, 1977], 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 source to cancel the volume velocity of the inner plate, which is open to cavity, of the sandwich panel. Cancelling the net volume velocity of this plate is compared not only in terms of the reduction in sound power in the enclosure but also in terms of the plate velocities. Numerical studies indicate that the active control method controls both the flexural and dilatational modes and therefore, attenuates significant amount of sound power inside the cavity irrespective of the isotropic loss factors of the viscoelastic core. Also a finite element study has been done in the commercially available COMSOL Multiphysics software to compare with the analytical result.