  Significant reduction in target strength and radiation signature can be
achieved by surrounding an object with multiple concentric layers comprised of
three acoustic fluids. The idea is to make a finely layered shell with the
thickness of each layer defined by a unique transformation rule. The shell has
the effect of steering incident acoustic energy around the structure, and
conversely, reducing the radiation strength. The overall effectiveness and the
precise form of the layering depends upon the densities and compressibilities
of the three fluids. Nearly optimal results are obtained if one fluid has
density equal to the background fluid, while the other two densities are much
greater and much less than the background values. Optimal choices for the
compressibilities are also found. Simulations in 2D and 3D illustrate
effectiveness of the three fluid shell. The limited range of acoustic
metafluids that are possible using only two fluid constituents is also
discussed.
