Konsberg EM 124, Руководство по установке

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Acoustic noise
As with any other hydroacoustic systems, the quality of the EM 124 echo data and
presentations are subject to unwanted acoustic noise. The echoes from any large and
small target must be detected inside the noise.
It is important that we keep the noise level as low as possible. The is necessary to obtain
long range and dependable interpretations of the echoes. Even with the advanced noise
filtering offered by the EM 124, we must address the noise challenge. This is important
during the planning and preparations for the EM 124 installation.
Topics
Contributing factors, page 27
Self noise, page 28
Ambient noise, page 31
Electrical self noise, page 31
Some means to reduce acoustic noise, page 31
Contributing factors
Several factors are contributing to the performance of the hydroacoustic equipment
used on board a vessel.
Factors contributing to the performance of the hydroacoustic equipment used on board a
vessel are:
• The quality and properties of the transmitted signal
• The quality of the receiving system
• The operational settings made during operation
• The properties of the target(s)
• The signal-to-noise ratio
The majority of these factors can neither be controlled nor improved by means
of installation methods or transducer locations. The quality and properties of the
transmitting and receiving systems are key factors during our product development, while
our end user documentation aims to help the user to make the right filter settings during
operation. As for the target properties, there is nothing any of us can do with those.
The signal-to-noise ratio , however, can be improved by making the correct choices
during installation.
Signal-to-noise ratio (often abbreviated SNR or S/N) is a measure used in
science and engineering that compares the level of a desired signal to the level of
background noise. It is defined as the ratio of signal power to the noise power, often
expressed in decibels. A ratio higher than 1:1 (greater than 0 dB) indicates more
Preparations