Kongsberg EA440 - Some Means to Reduce Acoustic Noise

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Somemeanstoreduceacousticnoise
Severalfactorsarecontributingtotheperformanceofthehydroacousticequipment
usedonboardavessel.CarefulplanningoftheEA440installationmayreducethe
acousticnoise.
Unfortunately,itisimpossibletosimplyprovideanumberofspecicproceduresto
reducethenoise.
Animportantfactoristhephysicallocationofthetransducers.Thisdependsonthe
vessel'sdesignandconstruction,howthehullisshaped,andhowthewaterrunsalong
thehull.Otherfactorsdealwithotherequipmentmountedonboard,andthiswillalsobe
vesseldependant.Atmoderateshipspeedsthemachinerynoiseisusuallydominant.At
mediumspeedstheownoiseincreasesmorerapidlyandtakesover,whileathigher
speedthepropellernoisewillbethemaincontributor.
Note
Theinformationheremustbeconsideredasgeneraladvice.EachEA440installation
mustbehandledseparatelydependingonthehulldesignandtheotherelectricaland
mechanicalsystemsinstalledonthevessel.
Reducingownoise
•Theshapeofthetransducer(ordomearoundit)
mustbeasstreamlinedaspossible.
•Thehullplatinginfrontofthetransducermustbe
assmoothaspossible.
Important
Beespeciallyawareofbilgekeelsandzincalloy
anodes.Thekeelmustberoundedoffwithout
sharpedges.Neitherextrudingobjectsnorabrupt
transitionsmustbepresent.
•Eachtransducermustbemountedwithasmallinclinationangle(approximately2
degrees).
Reducingmachinerynoise
•Eachtransducermustbeinstalledasfarawayfromtheengineroomaspossible.
•Themainengineandrelevantauxiliaryenginesandequipmentmustbexedtorigid
foundationstoavoidvibrations.
•Anyhullstructurethatmayvibrateshouldbedampedorcoatedtoreducethe
vibrations.
Theuseofshockabsorbersoroatingraftsmaysometimesreducethisnoise.The
structure-bornenoisemaybereducedbyisolation,forexamplebyprovidingvibration
clampingbetweenthetransducerandthehullstructure.
Preparations