Effect of poroelastic material on vibroacoustic behavior of truncated conical shells

Abstract

Acoustic transmission through single- and double-walled truncated conical shells lined with poroelastic material is analytically studied. The thin isotropic shells are excited by an oblique plane acoustic wave. The equations of motion of the shells are governed by Love's theory, and the wave propagation within the elastic porous material is described by an equivalent fluid model based on Biot's theory. To extract the acoustic pressures exerting on the surfaces of the conical shells, the shells are divided into several truncated segments which are narrow enough to be considered locally cylindrical. By employing a convergent power series solution the exact dynamic response of the conical shells is obtained. At first, the transmission loss results of this study are validated against those of previous works. Then, the results of various configurations of the single-walled conical shell lined with porous material are compared with those of its double-walled counterpart with equal mass. It is found that the single-walled shell lined with a porous layer is appropriate for sound insulation purposes at low frequencies below the first ring frequency, whereas, at higher frequencies, the double-walled sandwich shell provides better performance and more options for tuning the sound insulation. It is also shown that, except for low frequencies, the effects of the porous material and the method for bonding it to the facing shell are significant to improve the acoustic insulation ability. Finally, the influence of the porous layer thickness is investigated on the sound transmission loss.