Sound generation from the evolution and interaction of elliptic vortex rings and interaction of vortex ring with a rigid sphere are calculated numerically. Discretized vortex filaments are interpolated by using a parametric blending curve function to remove a possible numerical instability. The accuracy and efficiency of the scheme are validated by comparisons with the analytic solution of circular vortex ring interaction. Distinct acoustic periods are obtained from the evolution of each single elliptic vortex ring and the pairing process of two elliptic vortex rings. The calculated periods in the acoustic signals depend to a significant degree on the initial aspect ratio of the ring and the separation distance. The effect of vortex distortion on the flow arising from the interaction between a vortex ring and a rigid sphere is also analyzed for three-dimensional, inviscid and incompressible flow. with several initial separation positions. Three different interacting patterns can be observed with small change of the initial vertical separation position between the vortex ring and a rigid sphere; vortex passing by the sphere, vortex passing over the sphere, and vortex trapped (captured) by the sphere. Force variations on the sphere can be a significant source of noise as a dipole, whereas the distortion of the vortex filament contributes to the quadrupole sound. The forces acting on the sphere are obtained by using the unsteady Bernoulli equation. The unsteady pressure term, obtained by using the potential based panel method, contributes significantly to both the unsteady lift and the drag force during interactions. Acoustic fields generated by a spinning vortex pair near the flat wall or the circular cylinder are calculated to investigate the effect of wall scattering and wall pressure fluctuations (dipole source). For the flat wall, the whole acoustic field can be described by the sum of scattering effect from the wall and acoustic radiation from the spinning vortex pair without the wall effect. However, for the case of circular cylinder, dipole effect is large.
