P_{r} = [P_{T}/(4p)^{3}][(l^{2}G^{2}s)/R^{4}]e^{-4bR}

where

P_{r} = Received acoustic power, watts

P_{T} = Transmitted power, watts

l = Wavelength in the
medium, m

R = Distance to target, m

G = Gain of receiving and transmitting transducers

b = Absorptive attenuation
factor of the medium, pre meter

s = Equivalent cross-sectional
area of target, m2

the absorptive attenuation factors we have measured to date do not appear
to follow the e^{-4bR} term, the reason
for which is yet to be determined. We have found that for radar, attenuation
generally increases with frequency raised to the power of 0.5, whereas
for acoustic waves in rock the attenuation more commonly increases with
frequency raised to the power of 0.9.