Finite 90-Deg Biconical Surface as an Acoustic Target

Abstract

It is often desirable for an acoustic target to have a large target strength independent of target aspect. A sphere is considered to have a low target strength that is independent of target aspect, whereas a cylinder is considered to have a high target strength for a particular target aspect but low target strength for other aspects. The measured target strength in water of a finite 90-deg biconical surface as a function of target aspect is compared to similar data for a finite cylinder and sphere with the same relative dimensions. The biconical surface targets are two metal cones, having a common axis, and joined at their vertices with the vertex angles equal to 90 deg. The finite 90-deg biconical surface is shown to have a lower maximum target strength than the cylinder but has a target strength that is less dependent upon target aspect than that of the cylinder. Target strength data for four right-circular conical surfaces measured in water at two frequencies in the plane normal to the conical axis are compared to the empirical formula T = 10 logR3/3λ, where R is the radius of the base of the finite 90-deg biconical surface and λ is the wavelength of the incident acoustic wave. (This work is supported by the Bureau of Ships.)