Kongsberg Simrad SN90 Reference Manual page 555

Note
With the vessel in port, the environmental conditions are not satisfactory. In the shallow
waters of the port, noise from other vessels, dockyard workers or machinery will cause
unreliable test results. If you do this tests in a busy harbour, or with noise sources
present, the sensitive receivers will detect all the noise in the nearby waters.
About noise
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
• Fishing gear noise
(This is a generic illustration. Any similarities with specific products are accidental.)
The transducer can pick up noise from:
A
• Biological disturbances
• Interference
• Cavitation
• Propeller noise
• Flow noise
• Acoustic noise from other hydroacoustic systems
The transducer cable is long. Electric noise from generators, pumps, cooling
B
systems and other electric or electromechanical devices is easily picked up.
The preamplifiers are very sensitive. They can easily pick up electrical noise from
C
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 noise problems.
381294/E
Functions and dialog boxes
553