Band-gap engineering in periodic elastic composites

Periodic elastic composites can give rise to complete band gaps in which vibrations, sound, and phonons are forbidden. This is of interest for applications such as creation of vibrationless environment and improvements in transducers, as well as for pure physics related to localized vibrations and phonons. We present rudimentary ideas of the ‘‘band-gap engineering’’ necessary for designing suitable frequency gaps. This is illustrated by means of acoustic band structures, computed for periodic, binary composites of long, elastic cylinders that form a hexagonal lattice.