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.
The signal is the echo that we want to know something about, while the noise is any unwanted signals or disturbances. The echo must be detected in the noise and therefore it is necessary to keep the noise level is as low as possible in order to obtain long range and dependable interpretation.
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
•  Fishing gear noise
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A The transducer can pick up noise from
•  Biological disturbances
•  Interference
•  Cavitation
•  Propeller noise
•  Flow noise
•  Acoustic noise from other hydroacoustic systems
B The transducer cables are long, and may pick up electric noise from generators, pumps, cooling systems and other electric or electromechanical devices.
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 for 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.