Kongsberg EM 2040 MKII, Installation Manual

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The noise that contributes to the signal to noise ratio may be divided into the following
types of noise:
• Self noise
• Ambient noise
• Electrical noise
• Reverberation
• Underwater noise
The transducer can pick up noise from:
• Biological disturbances
• Interference
• Cavitation
• Propeller noise
• Flow noise
• Acoustic noise from other hydroacoustic systems
The transducer cables are long. Electric noise from generators, pumps, cooling systems
and other electric or electromechanical devices is easily picked up.
Self noise
Any vessel equipped with a hydroacoustic system (for example echo sounder or sonar)
will produce more or less self noise.
There are many sources of such self noise. It is necessary to analyse the different sources
of self-noise on a vessel, and find out how each source can affect the noise level of
the hydroacoustic instruments.
Machinery noise
The main contributor to machinery noise is usually the main engine on board the vessel.
The contribution from auxiliary machinery may, however, be considerable, especially if
it is in poor shape. The machinery noise can be transmitted to the transducer as:
• Structure-borne noise through the ship structure and the transducer mountings.
• Water-borne noise through the hull into the water to the transducer.
KONGSBERG EM 2040 MKII Installation Manual