Estimating bottom properties with a Vector Sensor Array during  MakaiEx 2005


P. Santos, P. Felisberto and S.M. Jesus


(1) Institute for Systems and Robotics, University of Algarve, Campus de Gambelas, 8005-139 Faro, Portugal.

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Nowadays, vector sensors which measure both acoustic pressure and particle velocity begin to be available in underwater acoustic systems, normally configured as vector sensor arrays (VSA). Such a system was used during the Makai 2005 experiment, off Kauai I., Hawai (USA) to receive precoded  signals in  a broad frequency band from 900 Hz up to 14 kHz.

The spatial filtering capabilities of the VSA can be used, with advantage over traditional pressure only hydrophone arrays, to estimate acoustic field parameters such as ray arrival time and angle, which could give rise to simplest and/or more reliable methods in bottom estimation. An additional motivation for this work was to test the possibility of using high frequency probe signals (say above 2 kHz) as a potential for reducing size and cost of actual sub bottom profilers and current geo acoustic inversion methods.

This work studies the bottom related structure of the VSA acquired signals, regarding the emitted signal waveform, frequency band and source-receiver geometry in order to estimate the bottom properties, specially bottom reflection coefficient characteristics. The agreement between the observed and modelled acoustic data is addressed. Preliminary results on the bottom reflection estimation will be also discussed.