Acoustic pulse in a wall-less waveguiding

Abstract

The reflection of an acoustic wave from a concave cone-shaped surface leads to the formation of an intense wave propagating along the symmetry axis, with a flat front and a radial profile described by a zero-order (n=0) Bessel function of the first kind. The wave front profile retains the shape over an extended path, as if the wave would be propagating in an acoustic waveguide; the role of the waveguide walls is performed by the side energy supply. In the case of a cone-shaped reflecting surface with a spiral directrix, the radial profile of the reflected wave field corresponds to the first-kind Bessel function with n>0 and the wave propagates as if in a hollow waveguide.