Specifications

SimradSH90
Figure8Reverberation
(CD015005E)
B
A
Theechoesfromthebottomwillvarywithhowuneventhebottomis,whatkindof
bottomyouhaveunderyourvessel,(rock,mud,sandetc.)aswellasyourcurrenttilt
setting.Theechofromtheseasurfacewillvarywiththecurrentseastateandyour
currenttiltsetting.
Theillustrationdemonstrateshowthebottomandtheseasurfacereturnechoesbackto
yoursonartransducer.Insituation(A)youwillseeseveralweakechoesfromthewaves
andfromtherockonthebottom,youwillstillbeabletoidentifytheschoolofsh.In
situation(B)youwillbeabletoidentifytheupperschoolofsh,butthelowerschool
willbehiddenintheshadowoftherock.
Beawareofthatothervesselsclosetoyouwillalsogeneratereverberationduetothe
waterdisturbancecausedbythewake,thepropellersandthecoolingwaterspill.
Blocking
Themovementofyourvesselthroughthewaterwilloften–especiallyinhigherseastates
–causeairbubblestobegenerated,andthesebubbleswillmovealongthehull.Thisis
calledblocking.Inordertopreventthisnoisefromdisturbingyoursonaroperations,itis
importanttolowerthesonartransducerasfardownbelowthehullaspossible.
Checkthenoiseyourself!
Ifyouarebotheredwithacousticorelectricnoise,youcaneasilyrunafewsimple
teststoidentifythecauseoftheproblem.
Howtochecktheacousticnoise
Thisprocedureprovidesasimplemethodtochecktheacousticnoise.
1ClicktheSetuptabtoopenthemenu.
2ClicktheTestbuttontoopentheSystemtestmenu.
3ClicktheTestcongbutton,andselectNoiseandVRintheparameterdialog.
4ClicktheClosebuttonintheparameterdialogtocloseit.
5ObservetheEcholevelbuttonontheSystemtestmenu.
6Readthenoiselevel.
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