Sea floor characterization by means of nonlinear multi-frequency generation

In the underwater context, it is known that the frequency diversity provides essential information to derive the nature of the seafloor. Actually, the information gathered from each single frequency gives a complementary picture of a particular environment. This presentation deals with the realization of a multi-frequency acoustic surveying tool based on the saturation effect. The transmitter is fed with a high-power single tone-burst: numerous harmonic waves are created by non linear interactions along the propagation. The source is unique in time and space so that the multi-frequency responses are inherently perfectly matched. The receiver is a rectangular multi-element broadband array realized for measurements in the sea environment. Seabed characterization measurements were made in the bay of Brest. First results of sediment backscatter response and seafloor images are presented.