B.0: FAQ B-2
3200-XS SUB-BOTTOM SYSTEM 0004840_REV_E
7. How do environmental conditions affect performance of the 3200-XS Sub-Bottom Profiling
System?
There are several environmental factors that affect performance:
Geological conditions 3200-XS Sub-Bottom Profiling System operating parameters and listed
specifications are greatly affected by the geologic conditions that the
acoustic energy transmitted from the tow vehicle encounters. A very
dense geologic interface, such as rock, coral, sand, stone, shell beds, and
so on, will limit the sound penetration into the sub-bottom. This
limitation is caused by the density interface reflecting most, if not all,
normal incidence acoustic energy back to the receiving hydrophone
which results in little penetration.
Air/water interface Air/water interface reflects 99.8 percent of the acoustic energy it
receives. Therefore, when air or gas is encountered in the water column
or in the sub-bottom, almost all of the transmitted acoustic energy will
be reflected back to the tow vehicle resulting in little or no penetration
into the seabed.
Survey vessel’s wake Ship's wake is a very turbulent area that is located immediately behind
the ship. When towing the tow vehicle in or near this wake, the
transmitted acoustic energy encounters highly charged aerated water
caused by the cavitation of the ship’s propellers. If the tow vehicle is
operated in this area, most of the acoustic energy from the aerated water
reflect to its source, similar to that exhibited by an air/water interface.
The tow vehicle is designed to operate in a horizontal position relative to
the sea floor. The turbulence encountered when operated in or near the
ship’s wake will cause instability in the tow vehicle and reduce the
effectiveness of the output energy in penetrating the sub-bottom
sediments.
Noise Operating other nearby acoustic devices at frequencies within the
operating frequency bandwidth of the 3200-XS Sub-Bottom Profiling
System can result in data distortion.
Survey vessel’s motion Tow vehicle is designed to tow in a stable horizontal plane. Excessive ship
motion can cause instability in the tow vehicle attitude resulting in
reduced performance. Rough sea conditions, sharp turns of the ship and
any similar external induced motions on the tow vehicle will have a
similar effect on the system operation.
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