High frequency acoustic wave reflection on the surf zone seafloor

Increased interest in high frequency sonar operations in surf and nearshore zones requires a knowledge of the acoustic properties of the sea bottom an d leads to study high frequency acoustic wave reflection on a recently sett led sediment particularly at low grazing insonification angles. In this pap er, wide angle specular reflection coefficients obtained by tank experiment s are compared with various models. An anomalous postcritical acoustic pene tration was observed experimentally. In the models, the sea bottom is succe ssively considered as an attenuating fluid, a viscoelastic solid, and final ly a poroviscoelastic medium. Applicability of these theories to sediments in the surf and nearshore zones was verified through the laboratory experim ents in the sediment by measuring reflection coefficients at 500 kHz and in verting them into physical properties and sound speed and attenuation, reve aling the nature of the material of the bottom and allowing comparison. An assessment of their validity is discussed, concluding that the Blot porovis coelastic theory is the best to model the non random acoustic and physical properties of the sediment.