A note on convergent zones

Abstract

An exact solution for ray paths near a sound channel with parabolic velocity profile is given for rays crossing the sound channel axis at small angles. The convergent zone for such rays for a source on axis is compared with the numerically computed result of Pederson, M.A. Journal of the Acoustical Society of America, 33, 1961: 465-474. Two simple straight line velocity gradient approximations are compared with the parabolic case for the purpose of observing their accuracy. Both cases show surprisingly good agreement over a range of choices for the gradients.