EXPERIMENTAL-STUDY OF THE DISPERSION OF ULTRASONIC-WAVES IN SANDY SEDIMENTS

The present note discusses the dispersion that occurs in sediments sat urated by water at medium ultrasonic frequencies (in the 0.2-1.2 MHz r ange). A standard algorithm based on the phase spectrum is used to cal culate the phase velocity versus frequency. Some measurements have bee n performed on a granular material (a sand sample provided by IFREMER) . It is shown that the wavespeed decreases slightly versus frequency. The implications of such measurements are discussed in relation with t heoretical models and some recently published results. (C) Academie de s Sciences/Elsevier, Paris.