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An important factor is the physical location of the transducer. 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 SN90 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 shape of the transducer (or dome around it) must be as streamlined as possible.
• The hull plating in front of the transducer must be as smooth as possible. Be
especially aware of bilge keels and zinc alloy anodes. The keel should be rounded
off without sharp edges.
Important
No extruding objects or any abrupt transitions should appear.
Reducing machinery noise
• The transducer must be installed as far away from the engine room as possible.
• The main engine and relevant auxiliary engines and equipment should be fixed to
rigid foundations to avoid vibrations. Use of shock absorbers or floating rafts may
sometimes reduce this noise.
• Any hull structure that may vibrate should be damped or coated to reduce the
vibrations.
• The structure-borne noise may be reduced by isolation, for example by providing
vibration clamping between the transducer and the hull structure.
Reducing propeller noise
• The transducer should be installed as far away from the propellers as possible.
• Sufficient clearance between the propellers and the hull, the rudder and the keel
should be provided.
• Place the zinc alloy anodes in places where the water flow is the least disturbed.
Simrad SN90
Summary of Contents for Simrad SN90
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