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Interference
Interference from other hydroacoustic equipment on board the same vessel may be an
annoying source of disturbance. Unless the same frequency is used for more than one
piece of equipment only the transmitted pulse will contribute to the interference.
In physics, interference is the phenomenon in which two waves superpose each
other to form a resultant wave of greater or lower amplitude. Interference usually
refers to the interaction of waves that are correlated or coherent with each other,
either because they come from the same source or because they have the same or
nearly the same frequency. Interference effects can be observed with all types of
waves, for example, light, radio, acoustic, surface water waves or matter waves.
https://en.wikipedia.org/wiki/Interference_(wave_propagation), April 2016
Ambient noise
Ambient noise is usually not a limiting factor to the performance of sonars and echo
sounders.
The ambient noise may be split up as follows:
•
Sea noise
: Air bubbles, seismic disturbances, waves, boundary turbulence, etc.
•
Biological noise
: Fish, mammals
•
Man made noise
: Other vessels, interference
•
Precipitation noise
: Heavy rain or hail
In some areas, where many vessels operate together, the engine and propeller noise from
other vessels may be disturbing. Interference from hydroacoustic instruments located
in other vessels may also be a limiting factor. The sea noise depends on the weather
conditions. In bad weather the sea noise can be quite high due to the waves.
Electrical self noise
Electrical or electronic self noise is picked up or generated in any other part of the
equipment than the transducer.
Hum picked up by the transducer cables or picked up from the power supply is usually
the most common source of electrical self noise. At higher frequencies – where rather
wide bandwidths are necessary – the noise from components, transistors or other
analogue electronic may be a limiting factor.
Summary of Contents for EA640
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