We have investigated classical waves propagating in periodic binary composites. For electromagnetic waves the network topology, in which the low-velocity material forms a continuous network, is more favorable for the appearance of gaps. In contrast, for scalar and elastic waves the cermet topology, in which the low-velocity material consists of isolated inclusions surrounded by the high-velocity host material, is more favorable.

• Received 2 August 1993

DOI:https://doi.org/10.1103/PhysRevB.48.13434