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Signal-to-noiseratio(oftenabbreviatedSNRorS/N)isameasureusedinscienceand
engineeringthatcomparesthelevelofadesiredsignaltothelevelofbackgroundnoise.
Itisdenedastheratioofsignalpowertothenoisepower,oftenexpressedindecibels.
Aratiohigherthan1:1(greaterthan0dB)indicatesmoresignalthannoise.WhileSNR
iscommonlyquotedforelectricalsignals,itcanbeappliedtoanyformofsignal[...].
http://en.wikipedia.org/wiki/Signal_to_noise_ratio(September2013)
Foractivesonarandechosoundersystems,thesignalistheechothatwewanttoknow
somethingabout,whilethenoiseisanyunwantedsignalsordisturbances.Theechomustbe
detectedinthenoiseandthereforeitisnecessarytokeepthenoiselevelisaslowaspossible
inordertoobtainlongrangeanddependableinterpretation.Thenoisethatcontributesto
thesignaltonoiseratioonhydroacousticinstrumentsmaybedividedintothefollowing
typesofnoise:
•Selfnoise
•Ambientnoise
•Fishinggearnoise
•Electricalnoise
•Reverberation
AThetransducercanpickupnoisefrom
•Biologicaldisturbances
•Interference
•Cavitation
•Propellernoise
•Flownoise
•Acousticnoisefromotherhydroacousticsystems
BThetransducercableislong,andmaypickupelectricnoisefromgenerators,pumps,
coolingsystemsetc.
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