Low-frequency sound radiation from a line force excited, fluid-loaded, baffled strip

Abstract

The two-dimensional problem of a fluid-loaded, baffled elastic strip (width 2a) excited by a time-harmonic line force (circular frequency ω) is analyzed theoretically. A Green's integral representation for the plate velocity distribution is used and boundary conditions are met by a system of two integral equations along the plate edges [P. Filippi, J. Sound Vib. 100, 69–81 (1985)]. For the case of clamped edges, results for the farfield pressure are presented for several values of koa, where k0 = ω/co is the wavenumber in the fluid. It is shown that at low frequencies, i.e., for koa ≪ 1, the strip radiates like a monopole with a strength equal to the net volume velocity of the strip. This monopole behavior of the finite strip differs from the well-known dipole radiation at low frequencies for a line force excited, infinite plate. The results are compared with similar results published by Filippi. The connection is discussed of the present problem to the case of an infinite plate with two parallel clamped line joints. [Work supported by the TNO Institute of Applied Physics, Delft, The Netherlands.]