Resonance peculiarities in sound focusing by liquid sphere

The angular and radial dependences of the acoustic pressure field for different values of the wave dimension $kr_0$ and attenuation in the material of a sphere are computed as a result of an exact solution using a BESM - 6 computer of a diffraction problem for a plane acoustic wave affected by a liquid sphere. Excitation of the natural vibrations of the sphere at definite values of $kr_0$ lead to a sharp variation of these dependences. At the n - th resonance, the angular dependence of scattering is determined by the dominant Legendre polynomial $P_n$, which leads to an increase in the number and amplitude of the secondary maxima, as well as to a significant increase in the maximum at θ = 0° (direction of mirror reflection). Attenuation in the material of the sphere leads to "stabilization" of the radial and angular pressure distributions, thereby converting the lens into a wide - band focusing system. The selection of material for this sphere with wave resistance ¯pc equal to the wave resistance of the surrounding liquid pc, does not eliminate the resonance nature of the focusing effect with $¯pc^{2}$ /$рс^{2}$ ≠ 1 (i.e., in the case of different compressibilities of the external and internal liquid).