equation C -2 (Urr - 1 Urr + ur + Uzz = Uttr U = F(r, t) on z =0, where F(r, t) is a given function and c is a constant. We also assume that the solution is bounded and behaves as outgoing spherical waves. We seek a steady-state solution for the acoustic radiation potential u = eto(r, z) with F(r, t)= eit f(r), so that o satisfies the Helmholtz equation 1 Orr + - - - r 0 +0zz + with the boundary condition Obtain the solution of the wave 0 0, (7.4.22) (7.4.23) 6=0, 0 0, on 2=0, (7.4.25)