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HYDROACOUSTICS
ANNUAL JOURNAL |
START | NEW VOL 20 | SEARCH | STATISTICS | PAS - GDANSK DIVISION |
pp. 137-142, vol. 17, 2014 Karol Listewnik Polish Naval Academy, Gdynia, Poland Key words: Lloyd mirror effect; measurement range Abstract: Noise propagation generated by a moving ship in shallow water is always associated
with energy loss because of absorption and the fact that sound is scattered by medium
inhomogeneities, also resulting in a decrease of sound intensity with range. Furthermore
sound propagation is strongly dependent on fluid space geometry and dimension, as well as
reflection and transmission loss through the sea bottom. The geometrical dimensions of the
measured ship and shallow water are comparable. The depth of water is usually less than the
length of the ship, so machinery vibration - due to propulsion machinery and auxiliary
machinery - acoustic noise in the compartments below the waterline, flow noise and propeller
noise are not generated by the hull of the ship from one point only. Hydroacoustic
measurement range is designed with the purpose of exploiting and distinguishing these effects
because of the amount of information they each bring; they allow to identify a different class
of ship, although interpretation of spatial distribution is very difficult because of sound
propagation in shallow water. This paper presents experimental research into the noises of
moving ships, measured on the sea bottom, with reflection about the influences of sound
propagation on the results of underwater acoustic measurement ranges.
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