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Themajorityofthesefactorscanneitherbecontrollednorimprovedbymeans
ofinstallationmethodsortransducerlocations.Thequalityandpropertiesofthe
transmittingandreceivingsystemsarekeyfactorsduringourproductdevelopment,while
ourenduserdocumentationaimstohelptheusertomaketherightltersettingsduring
operation.Asforthetargetproperties,thereisnothinganyofuscandowiththose.
Thesignal-to-noiseratio,however,canbeimprovedbymakingthecorrectchoices
duringinstallation.
Signal-to-noiseratio(oftenabbreviatedSNRorS/N)isameasureusedin
scienceandengineeringthatcomparesthelevelofadesiredsignaltothelevelof
backgroundnoise.Itisdenedastheratioofsignalpowertothenoisepower,often
expressedindecibels.Aratiohigherthan1:1(greaterthan0dB)indicatesmore
signalthannoise.WhileSNRiscommonlyquotedforelectricalsignals,itcan
beappliedtoanyformofsignal[...].
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
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