The concept of Johnson's dynamic permeability k(omega) is analyzed k(omega)
includes the effects of both the viscous force correction and the mass cou
pling in Blot's theory. A comparison between k(omega) and related Blot's fo
rmulation k(B)(omega) shows that the difference is slight if beta approxima
te to 64 alpha (infinity)/m. It is shown that the borehole acoustic guided
waves decay more slowly for a formation of a larger alpha (infinity).