Kongsberg EM 2040 MKII, Installation Manual

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Some means to reduce acoustic noise
Several factors are contributing to the performance of the hydroacoustic equipment used
on board a vessel. Careful planning of the installation may reduce the acoustic noise.
Unfortunately, it is impossible to simply provide a number of specific procedures to
reduce the noise.
An important factor is the physical location of the transducers. This depends on the
vessel's design and construction, how the hull is shaped, and how the water runs along
the hull. Other factors deal with other equipment mounted on board, and this will also be
vessel dependant. At moderate ship speeds the machinery noise is usually dominant. At
medium speeds the flow noise increases more rapidly and takes over, while at higher
speed the propeller noise will be the main contributor.
Note
The information here must be considered as general advice. Each system installation
must be handled separately depending on the hull design and the other electrical and
mechanical systems installed on the vessel.
Reducing flow noise
• The hull plating in front of the transducer must be as smooth as possible.
Important
Be especially aware of bilge keels and sacrificial anodes. The keel must be rounded off
without sharp edges. Neither extruding objects nor abrupt transitions must be present.
Reducing machinery noise
• Any hull structure that may vibrate must be damped or coated to reduce the vibrations.
Reducing propeller noise
• Sufficient clearance between the propellers and the hull, the rudder and the keel must
be provided.
• Place the sacrificial anodes in places where the water flow is the least disturbed.
• Ensure that the propellers blades are correctly designed and without damages.
KONGSBERG EM 2040 MKII Installation Manual