Control of sound transmission through thin plate

Active suppression of the acoustic transmission through plate structure is the major target of this paper. The model consists of a plane acoustic wave incident onto a clamped elastic rectangular thin plate and the piezoceramic patches modelled as four point moments are bonded on the surface of the plate as controllers. Control methods are model based, and rely on state or output feedback to change dynamic characteristic of the plate. The transmitted sound power before and after control is compared using different numbers of controllers. The results show that both the plate responses and the transmission of sound power obtained theoretically and experimentally match. After control the transmitted acoustic power is reduced by about 30-40 dB by one or two piezoelectric ceramics and the global sound pressure level is reduced by about 20-30 dB for low to mid-range frequencies. (C) 1998 Academic Press.