The paper is concerned with the hole-tone feedback cycle problem, also known as Rayleigh's bird-call. A methodology for analyzing the influence of non-axisymmetric perturbations of the jet on the sound generation is described. These perturbations are applied at the jet nozzle via piezoelectric or electro-mechanical actuators, placed circumferentially inside the nozzle at its exit. The mathematical model is based on the discrete vortex method, using vortex fllament rings. The nozzle and the holed end-plate are represented by bound (fixed) axisymmetric vortex rings. The shear layer of the jet and the actuator-equipped downstream section of the nozzle are represented by three-dimensional vortex fllaments. The sound generation is described mathematically using the Powell-Howe theory of vortex sound. The ultimate aim of the work is to control the flow and the accompanying sound generation.