Kongsberg Simrad ES80, Руководство по установке, Страница: 57 / 312

416739/A
55
C
The preamplifiers are very sensitive, and they can easily pick up electrical noise from
internal and external power supplies. The preamplifiers are also vulnerable to analogue
noise created by their own electronic circuitry. Digital noise created by the converter
and processing circuitry can also create problems.
D
Converters transform the analogue echoes to digital format.
E Signal processing circuitry can create digital noise.
Related topics
Acoustic noise, page 53
Preparations, page 41
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. We will here go into some details in order to
analyse the different sources of self noise on a vessel and how they may influence upon 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
Electrical noise
Modern vessels are normally equipped with a lot of electric instruments such as
hydroacoustic systems, radars, navigation systems, and communication equipment. Any
electric instruments may in some cases cause electrical interference and noise. International
regulations and certifications are used to control and reduce this, but even these are limited if
the electrical systems are poorly installed and/or maintained.
Propeller noise
Propeller noise is often the main source of noise at higher vessel speeds. Variable pitch
propellers or fast moving propellers usually make more noise than fixed propellers or slow
moving propellers.
Preparations