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http://en.wikipedia.org/wiki/Signal_to_noise_ratio(September2013)
Thesignalistheechothatwewanttoknowsomethingabout,whilethenoiseisany
unwantedsignalsordisturbances.Theechomustbedetectedinthenoiseandthereforeit
isnecessarytokeepthenoiselevelisaslowaspossibleinordertoobtainlongrange
anddependableinterpretation.
Thenoisethatcontributestothesignaltonoiseratiomaybedividedintothefollowing
typesofnoise:
•Selfnoise
•Ambientnoise
•Electricalnoise
•Reverberation
•Fishinggearnoise
AThetransducercanpickupnoisefrom
•Biologicaldisturbances
•Interference
•Cavitation
•Propellernoise
•Flownoise
•Acousticnoisefromotherhydroacousticsystems
BThetransducercableislong,andmaypickupelectricnoisefromgenerators,
pumps,coolingsystemsandotherelectricorelectromechanicaldevices.
CThepreampliersareverysensitive,andtheycaneasilypickupelectricalnoise
frominternalandexternalpowersupplies.Thepreampliersarealsovulnerablefor
analoguenoisecreatedbytheirownelectroniccircuitry.Digitalnoisecreatedby
theconverterandprocessingcircuitrycanalsocreateproblems.
DConverterstransformtheanalogueechoestodigitalformat.
ESignalprocessingcircuitrycancreatedigitalnoise.
Conceptdescriptions
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