The equations that underlie the so-called LMR method, popularized by Bill Goodway, convert P-impedance and S-impedance into and .
where is the first Lame parameter, is the second Lame parameter, and is bulk density. and are P- and S-impedance, respectively.
Through seismic AVO inversion (estimating P and S impedances from reflection data) these equations express impedance in rock properties. Supporters claim that λ and μ discriminate fluid effects from frame (lithology) effects and that elastic moduli are more transferable to engineers for geomechanics. Geologists or drilling engineers might not have an intuitive feeling for acoustic impedance, however they may feel more comfortable with rigidity and incompressibility.