Abstract: Using the wave propagation method (WPM), the forbidden band gaps of one-dimensional phononic crystals are studied. Results obtained using the method are evaluated against those by plane wave expansion (PWE). It shows that the results of PWE are close to those of WPM with an increasing of the wave number of PWE. Under the condition of the same computational accuracy, the computing time of WPM is about one fiftieth of that of WPE in the research of the forbidden band gaps in one-dimensional binary phononic crystals, and one hun- dredth in one-dimensional quaternary phononic crystals. Consi- dering the changing of elastic constants with frequency of visc- oelastic material, the forbidden band gaps can be obtained dire- ctly, and the computing time of WPM is about two orders of magn- itude lower than that of PWE improved using iterative method.

Key words: Forbidden band gaps, Phononic crystals, Viscoelasticity, Wave propagation method