Effect of Longitudinal Stringers on Sound Transmission into a Thin Cylindrical Shell

Abstract

In the context of the transmission of airborne noise into an aircraft fuselage, a mathematical model is presented for the transmission of airborne noise into a stiffened cylindrical shell. The stiffeners are longitudinal stringers and are modeled as discrete structural elements. The numerical cases examined were typical of a narrow-bodied jet transport fuselage. The stringers appeared to raise the cylinder transmission loss in the mass-controlled region, although they produced dips at the stringer resonances. The ring-frequency dip in transmission loss, which is characteristic of monocoque shells, was found to still be present. There appeared to be a small increase in transmission loss as the number of stringers was increased. The effect of high damping was also investigated.