COMPLETE ACOUSTIC STOP BANDS FOR CUBIC ARRAYS OF SPHERICAL LIQUID BALLOONS

We present theoretical results for acoustic band structures for cubic arrays of spherical water balloons surrounded by a mercury. host. Mult iple, complete acoustic band gaps (i.e., stop bands) are found for the face-centered cubic (fcc), body-centered cubic (bcc), and simple-cubi c (sc) lattices. These stop bands are widest for a volume fraction of similar to 24% and the corresponding gap/midgap ratios are about 0.83, 0.77, and 0.62, respectively, for fee, bcc, and sc lattices. We stres s that such a simple three-dimensional (3D) inhomogeneous system of li quids exhibits the largest stop bands ever reported for 3D elastic as well as for dielectric composites. For mercury balloons surrounded by water the gaps obtained are surprisingly small. (C) 1996 American Inst itute of Physics.