ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06
2aUW13. Effects of ship trim and dynamic attitude on the relative noise
level measured by a hull-mounted multibeam bathymetric sonar.
C. de Moustier
Marine Physical Lab., Scripps Inst. of Oceanogr., La Jolla, CA 92093-0205
Acoustic data recorded in various sea conditions with the hull-mounted
multibeam swath bathymetry system SeaBeam 2000 aboard R. V. MELVILLE have
been analyzed to quantify the relationship between the ship's attitude and the
relative noise levels observable in the data. The data consist of concurrent
time series of echo magnitude and direction of arrival for each transmission
cycle, and of the three attitude components roll, pitch, and heave. Although
higher noise levels are usually associated with pitch, in these data heave has
the greatest impact on noise level, presumably because of bubble syphoning from
the areated surface layer. In addition, a slight change in the trim of the ship
from horizontal to bow up results in an average relative noise increase of
about 12 dB. [Research supported by ONR.]