a) The Gassmann (1951) equation is inherent zero frequency theory, but due to experimental difficulties, the Gassmann equation has not been rigorously verified in both laboratory and field.
b) Biot's theory incorporates frequency effects, thus it is inadequate to account for overall dispersion in rocks as its considers only the effect of large scale fluid flow ( regional flow ).
c) For example, for high porosity, high permeability rock saturated with low viscosity fluid, the seismic data gathered at 10-200 Hz which are close to Gassmann. While the low porosity, low permeability rock saturated with high viscosity causing the data gathered at the frequency close to log or lab measured data.
d) However, the true magnitude of wave dispersion in fluid saturated rock will remain unknown until several technical problem is solved.