Abstract: This paper presents a theoretical analysis of the reflection of a sound pulse by the plane interface between the air and an idealized porous medium. A general expression for a pulsed point source has been derived. The detialed analysis is presented for three special cases: (1) source and receiver located on a line perpendicular to the interface, semi-infinite porous medium; (2) source and receiver located on a line perpendicular to the interface, porous me-dium layer; (3) grazing incidence, semi-infinite porous medium. In the second case, the problem is solved by considering the different reflections in the layer of porous medium. Experimental results are compared with the theoretical calculations for a kind of porous material.