Pulse-echo method can't measure wave attenuation accurately
  A number of techniques with different degrees of accuracies have been devised for the measurement of acoustic wave attenuation in solids and liquids. Still, a wide variation is observed in the attenuation values in different materials reported in the literature. Present numerical study based on a 'propagating wave' model analysis clearly shows that the attenuation constant obtained from exponential fitting of the echo heights in pulse-echo method differs from the exact value of intrinsic attenuation in the medium, even in the ideal situation of plane wave propagation without diffraction, dispersion or scattering. 
Barnana Pal
physics.ins-det cond-mat.other