Vector intensity field scattered by a rigid prolate spheroid

This is the authors' abstract. We don't add key points for this paper.

The short-wavelength, steady-state vector intensity field scattered by a rigid prolate spheroid (10:1 fineness ratio) is investigated analytically. The intensity field is the product of the scalar acoustic pressure and the acoustic particle velocity fields which are computed from the Helmholtz equation in prolate spheroidal coordinates. Particular emphasis is placed on results in the forward-scattered direction. It is found that the equivalent plane wave intensity varies by less than ±0.5dB (relative to the incident acoustic intensity) in the far-forward-scattered direction with the selected parameters. This illustrates that the forward-scattered pressure is masked by and interferes with the incident wave. The reactive intensity in the forward-scattered direction is found to be −25dB relative to the incident active intensity, and the computed phase difference between pressure and particle velocity is 4° at ranges approaching 10 spheroid lengths at a reduced frequency of h=41.7; in the absence of the spheroid, the phase difference due to the incident plane wave alone is exactly 0°. The study demonstrates that unique information, extending beyond direction-of-arrival estimation, can be derived from the total acoustic intensity field and may allow inferences to be made regarding the presence or absence of the spheroid.