SELF

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S.B. Karavashkin and O.N. Karavashkina

We can add that in the view of the longitudinal acoustic wave radiation, the idea of an acoustic dipole (first-order radiator) per se is conventional. “Such acoustic radiator is equivalent to two antiphase-oscillating spheres. The dipole field depends on the direction, its directivity diagram has 8-form. Close by the dipole, the acoustic field potential has a form cos /r², where is the angle between the axe of a dipole and the direction to the observation point (see Fig. 2), and in the far field cos /r” [ibidem, p. 39].

Fig.2. Conventional model of acoustic dipole (after [6, p.39])

However, in all the current theoretical and applied calculations (see e.g. [8], [9], [10]) not a pulsing but oscillating sphere is investigated. For a longitudinal acoustic wave this substitution is inessential, since both models are equivalent for this case. But for the transversal acoustical wave the difference is basic. An oscillating sphere does not produce a directed radiation in the normal direction, while according to the investigation presented below, a transversal acoustic wave can be formed only as a superposition of two longitudinal waves. In EM fields no one noted this feature, because a longitudinal field of charges per se is equivalent to a pulsing sphere, and we cannot make it directed as the pressure in gas dynamics. On the contrary, in the EM field theory there is the problem of a longitudinal EM wave radiation/reception being, of course, the feature of the compared physical phenomena. None the less, the possibility to form the polarisation plane in an acoustic wave leads to the appearance of the new properties of the wave process in gas dynamics differing from the simple superposition of two acoustic sources. The same as in case of a transverse EM wave, we should expect that in the interaction with reflecting objects, or in refracting media the polarisation plane peculiarities will essentially depend on the interaction pattern. For example, we can reveal the polarisation angle similar to the Brewster angle; the polarisation plane can rotate when the wave transits through the turbulent, heterogeneous or layered media, or through the media having the polarising heterogeneities. It means, when the transverse acoustic wave radiators/receivers appeared, the investigators obtain the powerful tool for the hydro- and aerodynamic investigations, the new scope to study the media properties revealing in the interaction with a transversal acoustic wave. Furthermore, with the polarisation plane appearance in an acoustical wave, we obtain the additional parameter whose variation is able to transmit the information. It essentially broadens the interest to the investigated phenomenon beyond the acoustic frames, enables us to discuss the feature of a transversal acoustic wave in gas as the independent physical phenomenon and makes important the investigations whose results we present in this paper. The more that up to now there exist no publications studying just the antiphase waves superposition and using the polarisation-type device as the receiver.