Ilja E. Tsukernikov
AO ``NIIpolygraphmash'' ul. Profsojusnaya, 57, Moscow, 117420, Russia
A method is offered for the calculation of radiation field using measurements of sound pressure and the vibration velocity normal component on a spherical surface surrounding the sound source and setting it off from extraneous sound sources. The total diffraction field is presented as a superposition of the spead radiation field and the field to be scattered by the source surface (a direct field) as well as standing waves describing a reflected field and a field of extraneous sources. The scattering properties of the emitting sphere are given with the help of modal impedances. The field components are represented as an expansion in terms of the spherical harmonics. The expansion coefficients for the scattered field pressure on the source surface are calculated by solving of the integral equation of the second kind which is derived from the discontinuity properties of the Helmholtz integral on the boundary surface and from the impedance boundary condition. The radiation field is found as the difference of the direct field and the scattered field presented with the help of the Helmholtz integrals calculated over the measured and emitted surfaces. The method is illustrated by calculating the radiation field of a sphere pulsating with the prescribed velocity in the space bounded by the perfect reflecting spherical surface.
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