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