A sensitivity study for full-field inversion of geo-acoustic data
with a towed array in shallow water

S.M. Jesus sjesus@ualg.pt
UCEH - Universidade do Algarve
PT-8000 Faro, Portugal

download pdf file .
Ref.: 2nd European Conf. on Underwater Acoustics (ISBN 92-826-8000-2), pp. 899-904, Copenhagen, Denmark, 1994.

Abstract:This paper presents some of the preliminary work aimed at estimating the ocean bottom morphological structure in coastal waters using a towed array. In order to obtain an idea of the expected performance of the system and draw some conclusions on its operation this study presents the sensitivity of three processors to variations of: array length, source and receiver positions, sensor noise, source frequency and frequency band. Conclusions tend to demonstrate that cost function sensitivity to sound speed variations is higher on the bottom top layers and it increases with array length. An increased sensitivity is generally acompanied by a cost function non-monotonic behavior creating local minima and making it more difficult to reach the global minimum. Attenuations have in general small influence on the acoustic field structure and are therefore difficult to estimate. Increasing the signal frequency band by incoherent module averaging has no significant influence on sensitivity. A cost function relaying on the conventional matched filter has shown low sensitivity to sensor noise and is being extended to matching directional data from bottom arrivals at several frequencies. Mismatch cases, mainly those related to array/source relative position, will be also presented.

ACKNOWLEDGMENT: this work was partially supported by the EU project MAS2-CT920022.