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 you 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 signal than noise. While SNR is commonly quoted for electrical signals, it can be applied to any form of signal [...].
Wikipedia, Copied September 2013
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 as low as possible in order to obtain high echo 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
•  Underwater noise
•  Fishing gear noise
Image
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 cable is long. Electric noise from generators, pumps, cooling systems and other electric or electromechanical devices is easily picked up.
C The preamplifiers are very sensitive. 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 noise problems.
D The converters transform the analogue echoes to digital format.
E Signal processing circuitry can create digital noise.
Related topics
Acoustic noise