The last decades, a lot of research has been done about the propagation of sound in heterogeneous and porous materials. Especially the two-phase nature of the poro-elastic material leads to interesting physical phenomena. During recent years, several measuring methods have been developeded to determine the material parameters. However, a lot of problems aren't solved yet. Because of the visco-elastic behavior of a lot of these materials, the elastic moduli will become frequency dependent (rubberlike behavior at low frequencies and glasslike behavior at high frequencies). Experimental data about the frequency- and temperature dependence of the elastic moduli are scarce because of experimental difficulties. Some experimental and numerical results about this subject will be presented . Porous materials still have to be studied in a lot of configurations. One of them is a porous material in an elastic cylinder. Some numerical results about the dispersion curves of the wave propagating in the system will be presented. These will be compared with some experimental results.