Samuel Pinson, PhD in Underwater Acoustics
His research work (led at the French Naval Academy Research Institute - IRENav - Underwater Acoustics Research Team) is entitled Seafloor Characterization using the Image Source Method.
The jury, composed of:
-* Dr Jean-Yves Royer, CNRS Researcher at UBO
-* Pr Jérôme Mars, Professor at the department of Image and Signal - Institut Polytechnique de Grenoble
-* Dr Philippe Roux, CNRS Researcher at the Institut des Sciences de la Terre de Grenoble
-* Dr Yann Stéphan, Research Engineer at the Service Hydrographique et Océanographique de la Marine in Brest
-* Dr Pierre Cervenka, CNRS Researcher at the Institut Jean Le Rond d'Alembert in Saint-Cyr l'Ecole, Pierre and Marie Curie University - Paris VI, and PhD supervisor
-* Dr Laurent Guillon, Associate Professor at the French Naval Academy Research Institute, co-supervisor
-* Pr Charles Holland, Professor at the Applied Research Laboratory of the Pensstate University, USA.
awarded him the title of PhD of the Western Brittany University in Underwater Acoustics, with a summa cum laude distinction.
The work presented in this thesis deals with a new seafloor characterization method : the image source method. It is based on a physical model of the reflected waves from a point source by a layered media under the Born approximation. Thus, the reflected signal can be modeled as a sum of contributions coming from image sources relative to the seabed layers. The seabed geometry and sound speed profile can then be recovered with the localization of these image sources. The image source localization is based on recorded signal migrations and the detection is done using a semblance function. So, the method uses only one record of the seabed reflected path for one shot of the source. The main method advantages are the automation of the process, its low computational cost, its good robustness to the noise and the local aspect of the result. The results obtained with real data are very satisfying with both a vertical array and a horizontal array. Especially using an horizontal array, many successive measurements along a straight line give a range dependent sound speed profile of the seabed.
Image sources, inversion, geoacoustic, layered media, source localization