A method for acoustic scattering by slender bodies. II. Comparison with laboratory measurements

摘要

This paper describes a comparison between a sound scattering model for slender bodies proposed in Ye et al. [J. Acoust. Soc. Am. 102, 1964–1976 (1997)], and laboratory measurements of forward and bistatic scattering by individual fish [Ding, J. Acoust. Soc. Am. 101, 3398–3404 (1997)]. A prolate spheroid target made of styrofoam is also measured to help verify the model, and it is found that the model results agree reasonably well with the measurements of the styrofoam target. Scattering of fish is assumed to be primarily due to fish flesh and swimbladder, which are modeled as liquid filled and gas filled, respectively. An asymmetric prolate spheroid is used to approximate the geometry of both fish body and swimbladder. It is shown in the modeling that fish body (flesh) is more important in determining the forward scattering at the frequency of interest (38 kHz), while in the case of bistatic scattering, swimbladder is still dominant. The model appears able to produce results in good agreement with the measurements of bistatic scattering, for incident angles within ±40°. For forward scattering, the model results of fish body follow well the general trends of the data for one side of incident angles, but for the other side, do not show as large variability as the data, suggesting more complex structures involved. When the scattering by swimbladder is added coherently to that of fish body, the total scattering is stronger than the data. Therefore it remains an open question how to combine contributions from fish body and swimbladder when their scattering strengths are not significantly different.