Publication Date:
2022-05-26
Description:
This is the final report of Contract N00014-84-C-0185 between the Woods Hole
Oceanographic Institution and the Office of Naval Research for the contract
period 1 January, 1984, to 28 February, 1985. This contract supported an
experiment that was conducted in the Norwegian Sea during May and June of 1984
to assess the possibilities of using ocean acoustic tomography as a measuring
tool in the Arctic. The object of the experiment was to identify and
determine the temporal stability (coherence), and resolvability, of Arctic
acoustic paths. Identification refers to the ability to match a pulse arrival
with a particular ray path, primarily through computer modelling. Resolvable
rays are those that arrive sufficiently far apart in time so as to be distinct
and separable. In order to use tomography, rays must be identified, resolved
and stable. Unlike the deep temperate ocean, where there are many wholly
refracted paths, the upward refracting Arctic sound speed profile causes ray
paths to reflect off the ice-covered surface of the permanent pack and the
mixed ice-covered and ice-free surface of the marginal ice zones. The
reflection process is time-varying and hence leads to resolvability,
identification and stability questions that do not arise in the case of
entirely refracted paths.
A 224 Hz acoustic source was moored in an ice-free region. It transmitted
phase coded, frequency stable signals to receivers fixed on the bottom and
receivers drifting with the icepack at ranges of approximately 150 km. The
received signals are to be analyzed with respect to identification,
resolvability and stability issues.
This contract covered the costs associated with installation and retrieval of
the source and preliminary data reduction from the drifting and fixed
hydrophones. Detailed data analysis costs are to be covered elsewhere.
Nevertheless, preliminary analysis indicates that the received signals,
particularly those from paths that interact with the ice-free surface, appear
to have sufficient stability for tomographic purposes.
Description:
Funding was provided by the Office of Naval Research under Contract
N00014-84-C-0185.
Keywords:
Underwater acoustics
;
Tomography
;
Sound
;
Hearing
Repository Name:
Woods Hole Open Access Server
Type:
Technical Report
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