Porous silicon (PS) layers were obtained from (100) p(+)-type silicon substrate of thickness 290 mu m with a resistivity of (1-8) x 10-(2) Omega cm and porosity values ranging from 20% to 55%. Microacoustic techniques were performed to investigate the elastic properties of the PS layers. The porosity dependence of the longitudinal and Rayleigh velocities of the PS layers was obtained by microechography and acoustic signature V(z) respectively. Moreover, acoustic imaging was performed in order to analyse qualitatively the homogeneity of the samples. The profile of the PS layer-non-porous silicon interface was also obtained by time-resolved measurements.