Kongsberg EA440 - Avoid Protruding Objects Near the Transducer

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Cavitation
Cavitationistheformationofsmallairbubblesclosetothetransducerface.Thebubbles
appearbecausethelocalpressurebecomesnegativeduringpartsoftheacousticpressure
cycles.Thecavitationthresholdincreaseswiththehydrostaticpressure.Thenoiseis
madewhenthebubblesimplode.
Transmittinginair
Thetransducermustneverbeliftedfreeofthewatersurface.Ifthetransduceris
activatedwhenoutofwateritmaybedamagedbeyondrepair.Mountingthetransducer
atadeeppositiononthehullwillinnormallypreventthis.
Slamming
Slamminghappensifthevesselhullclimbsoutofthewaterinheavyseas.Theforceof
thewaterwhenthehullfallsdownmaypushthetransducerup,andmaycausedamage
bothtothetransducerandtoitsmounting.Thisisespeciallyimportantforlowfrequency
transducerswithlargefaces.Theeffectofslammingcanbereducedbymountingthe
transducerasdeepaspossibleonthehull.
Note
KongsbergMaritimeAStakesnoresponsibilityforanydamagestothetransducer,the
cableorthemountingarrangement,causedbyslamming.
Avoidprotrudingobjectsnearthetransducer
Objectsprotrudingfromthehullwillgenerateturbulenceandownoise.Thiswill
reducetheEA440performance.
Protrudingobjectsmaybezincanodes,transducersoreventhevessel'skeel.Holesand
pipeoutletsarealsoimportantnoisesources,aswellasroughsurfacescausedbybad
welding.Eventracesofsealingcompound,sharpedges,boltsoremptyboltholeswill
createnoise.Alltheseprotrudingobjectsmayactasresonantcavitiesamplifyingthe
ownoiseatcertainfrequencies.
Donotplaceatransducerinthevicinityofprotrudingobjects,andespeciallynotclose
behindthem.Makesurethatthesurfaceofthetransducerface,thehullplatingandputty
aroundthetransducerisasevenandsmoothaspossible.Mountingscrewsorboltsmust
notbeextrudingfromthetransducer,theinstallationhardwareorthehullplating.If
necessary,grindandpolishallsurfaces.
EA440Installationmanual