In this report a process is presented which allows the complete characteris
ation of homogeneous structures using ultrasonic spectroscopy. This analysi
s makes use of only two backwall time domain signals of the media being tes
ted Since they present an attenuation almost linearly proportional to frequ
ency, the use of the Fast Fourier Transform and an adequate processing of t
he echoes in the frequency domain have permitted one to evaluate the amplit
ude and phase responses characterising the media. The amplitude response in
conjunction with the respective linear function has allowed the measuring
of the acoustic impedance and attenuation, and the phase spectra have permi
tted the evaluation of the thickness and phase velocity. Such parameters ca
n give a great contribution to the total characterisation of structures, na
mely in terms of grain size and percentage porosity.