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The mechanism of acoustic oscillation generation due to the formation of stable vortex structures in a medium in motion is considered with reference of the example of impinging swirling air flow. It is established that, as the swirling flow attains a limiting flow-rate velocity, the amplitude frequency characteristic of the acoustic oscillations in the hydromechanical system restructures itself. The discovered effect of the acoustic oscillation self-adjustment manifests itself in the resonance amplification of the amplitudes of the vortex chamber eigenfrequencies at the expense of the absorption of the acoustic oscillation spectrum components generated by the vortex structure of the flow.An investigation of the vortex formation effect on the acoustic oscillation generation on the sound and infrasound ranges is of great importance in developing a new, more perfect generation of different vehicles and power setups, including nuclear power plants.The phenomenon of acoustic oscillation generation in liquid and gaseous media due to the vortex formation effects was named the "vortex sound" [1]. In accordance with the conventional representations, the vortex sound generation mechanism was mainly connected with the vortex formation effect in flows past bodies (Aeolian harp [1]). At the same time, the experimentally established and fairly well studied facts include the sound oscillation generation in the so-called vortex whistles or vortex sound generators. The authors of [2-4] performed some theoretical and experimental studies which can provide the foundation for understanding the mechanism of the vortex generation of acoustic oscillations. In those studies the sound radiation process was explained basing on the ideas connected with the manifestation of the hydrodynamic instability of a swirling flow due to the precession of the region of quasi-solid rotation of the central vortex generated under the action of geometric and dynamic flow parameters. It was believed that the vortex generator, as an acoustic radiator, represents a rotating vortex.As shown in the experiments [5][6][7], the reason for the acoustic oscillation appearance in swirling flows can be the effect of the formation of a deterministic internal vortex structure of the flow. The relation between the vortex flow structure and the acoustic resonance generation effect was established using the acoustic method proposed in [5] and based on the measurement of the frequency characteristics of sound oscillations in a swirling impinging jet. The theoretical analysis using the acoustic flow approximation [5] and helical flow theory [8], together with the comparison of the experimental and calculated results, validate the suggested physical flow model which predicts the appearance of vortex resonances due to the vortex flow topology.

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